Transformador de Potência e Reator: Manual de Instalação e Operação

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POWER TRANSFORMERS &
REACTORS
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INSTRUCTION MANUAL
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(JÉÆb÷ - 2)
INSTRUCTIONS FOR INSTALLATION,
COMMISSIONING, OPERATION AND
MAINTENANCE
(VOLUME - II)
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BHART HEAVY ELECTRICALS LIMITED, BHOPAL
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Eäò ºlÉÉ{ÉxÉ, Eò¨ÉÒ¶ÉËxÉMÉ {ÉÊ®úSÉɱÉxÉ B´ÉÆ +xÉÖ®úIÉhÉ Eäò
ʱɪÉä +xÉÖnäù¶É
INSTRUCTIONS FOR INSTALLATION,
COMMISSIONING, OPERATION AND
MAINTENANCE OF
POWER TRANSFORMERS
&
REACTORS
¦ÉÉ®úiÉ ½äþ´ÉÒ <±ÉäÎC]ÅõEò±ºÉ ʱÉʨÉ]äõb÷, ¦ÉÉä{ÉɱÉ
BHART HEAVY ELECTRICALS LIMITED,
BHOPAL
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
ºlÉÉ{ÉxÉ, Eò¨ÉÒ¶ÉËxÉMÉ, {ÉÊ®úSÉɱÉxÉ B´ÉÆ +xÉÖ®úIÉhÉ Eäò +xÉÖnäù¶É
JÉÆb÷ - II
(EÖò±É JÉÆb÷ - 2)
INSTALLATION, COMMISSIONING,
OPERATION AND MAINTENANCE
INSTRUCTIONS
VOL-II of II
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
PREFACE
BHEL Transformers and Reactors are designed, manufactured and
tested with care. With proper attention during installation and use, the user
should receive from it the maximum expected service.
Before installing the transformers/ reactor read these instructions
carefully.
These instructions have been prepared to provide information on
assembly, installation, commissioning and regular maintenance of the
transformers/reactors and shall form part of Instruction Manual.
These instructions do not intend to cover operation and maintenance of
the transformer under abnormal conditions.
Should further information be needed or any problem arises which is
not covered by these instructions, please ask BHEL for further information.
In operating the Transformer/Reactor, Care should be taken that loading
limits as specified are strictly followed. For instructions regarding, general
information on accessories such as OLTC, WTI, OTI, Buchholz relay, fan,
pump, etc. Vol. I may please be referred.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
CONTENTS
Page No.
SECTION
SECTION
SECTION
SECTION
1
GENERAL INFORMATION
1.1
INTRODUCTION
11
1.2
TRANSPORT OF TRANSFORMER / REACTOR
13
2
INSTALLATION
2.1
RECEPTION AND ASSEMBLING OF TRANSFORMERS
/ REACTORS DESPATCHED PARTLY DISMANTLED
AND FILLED WITH NITROGEN
21
2.2
STORING OF TRANSFORMER / REACTOR DESPATCHED
FILLED WITH NITROGEN
33
2.3
ASSEMBLING OF EXTERNAL PIPES
35
2.4
INSULATING OIL, QUALITY AND TREATMENT
37
2.5
OIL FILLING UNDER VACUUM
41
2.6
OIL FILLING INSTRUCTIONS FOR CONSERVATORS
WITH AIR CELL
47
2.7
UNTANKING OF ACTIVE PART
53
2.8
MOUNTING OF GASKETS
55
2.9
WELDED COVER (IF APPLICABLE)
57
2.10 EARTHING OF ACTIVE PART AND CORE
INSULATION TEST
59
2.11 TOUCH-UP PAINTING
69
3
COMMISSIONING
3.1
TESTING AFTER ASSEMBLY OF THE TRANSFORMER
/ REACTOR AT SITE
77
3.2
COMMISSIONING CHECKS - TRANSFORMER
79
3.3
COMMISSIONING CHECKS - REACTOR
93
4
MAINTENANCE AND OPERATION
4.1
SUPERVISION OF TRANSFORMER / REACTOR
101
4.2
SUPERVISION AND CONTROL OF OIL
109
4.3
TROUBLE SHOUTING
109
4.4
PARALLEL OPERATION
119
4.5
DO'S AND DON'TS
137
4.6
DISPOSAL
145
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
¦ÉÉMÉ-1
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SECTION-1
GENERAL INFORMATION
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
SECTION 1
GENERAL INFORMATION
1.1
INTRODUCTION
1.1.1
POWER TRANSFORMERS
Unlike shunt reactor and Neutral Grounding Reactors where standard
specification is generally followed by utilities, requirements of power
transformers vary depending upon the system design. Hence a tailor made
product becomes the answer. Depending upon the requirements two winding/
three winding/ auto connection/ split winding arrangement with ON LOAD or
OFF CIRCUIT tap changer, five limbs/ three limbs core construction, welded
or bolted tank construction are adopted.
Variation in capacity, impedance and transport profile result in different
sizes of transformer. Refer VoI I for specific requirements of the equipment.
1.1.2
SHUNT REACTORS
Shunt Reactors are used in high voltage systems to compensate
capacitive generation from long lightly loaded overhead lines or extended cable
systems and also for control of dynamic over voltages.
Gapped core construction is preferred for high system voltages over
coreless construction due to the high energy density that can be achieved in
gapped core construction. The core sections between consecutive air gaps
are moulded in epoxy resin to prevent movement between individual laminations.
The spacers forming the air gaps are blocks of ceramics with a high modules
of elasticity and the whole stacking of core modules is cemented together
during the assembly to form a solid column without possibility of rocking , or
rubbing between individual parts.
The core segments are of radial laminated configuration. The radial
laminations prevent fringing flux from entering flat surfaces of core steel which
would result in eddy current overheating and hot spots.
Five limbed core construction is adopted to achieve high zero sequence
impedance. In addition to the three gapped core limbs with windings, there
are two continuous outer return limbs. The two unwound side limbs help in
achieving zero sequence impedance approximately equal to the positive
sequence impedance. Other construction type can be a three limbed
construction. For single phase reactors e.g. 800 KV class middle leg wound
with two return legs type of construction is adopted.
Interleaved disc winding has been used for rated voltages 220 KV and
above. This type of winding configuration provides better impulse voltage
distribution. For lower voltage classes a continuous disc winding or a multi
layer helical winding are used. The tank is rectangular in construction with flat
cover welded to the tank rim at top. The associated cooling control equipment
is housed in a tank mounted weather proof marshalling box. The reactors are
equipped with all standard measuring and controlling fittings and accessories
as described in Volume I.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
Reactors have been designed for resting on concrete foundation as shown
in the foundation plan drawing. Rollers have been provided only for movement
of the reactor at site.
1.1.3
NEUTRAL GROUNDING REACTOR
When single pole reclosing is used on lines, the Neutral Grounding Reactor
is used.
The Neutral Grounding Reactors are connected between neutral point
of 400 kV/800 KV reactors and earth, where the neutral of shunt Reactor is
suitable for 145 kV class insulation.
The reactors are oil immersed type ONAN cooled (oil immersed with
natural air cooling) with continuous rating of 10/15 Amps and a 10 sec. rating
as indicated in the Rating Data sheet. As continuous losses of the reactors are
negligible, reactor tank surface is adequate for dissipation of these losses.
Hence radiators are not provided.
Considering linear impedance characteristic requirement upto rated short
time current a core less design with magnetic shielding of CRGO sheet has
been made. The magnetic circuit, therefore consists of rectangular frame of
CRGO steel lamination packets of adequate area. Area of magnetic circuit is
selected such that saturation does not take place under short time current. A
rigid clamping structure is provided for clamping of magnetic frame and a very
low flux density is used to minimize the vibration and achieve linear impedance
characteristic.
The graded disc type concentric winding suitable for a rated voltage of
145 kV and basic insulation level of 550 kVp has been provided without core
inside. Winding is held in position by way of special insulation structure inside
winding and finally kept under pressure between top and bottom yokes of
magnetic frame. Return path of flux is provided by way of two return limbs.
The line terminal is taken out through the tank cover via 145 kV, 800
Amps OIP condenser bushing provided with suitable terminal connector. The
neutral lead is taken out through the tank cover via a 36kV, 630 Amps porcelain
bushing.
The tank is of welded mild steel plate construction shot blasted on the
inside and outside to remove scales before painting. The tank is painted on the
inside with yellow paint and its outside surface is painted with two coats of
primer paint and finishing coat, of light grey paint to shade 631 of IS:5. This
is a standard painting scheme followed for all equipment .
The fittings include a conservator with a magnetic oil gauge, pressure
relief device, drain and filter valves, sampling valves, thermometer pockets,
Buchholz relay, temperature indicator for oil and silicagel breather .
These reactors are designed for mounting directly on plinth.
1.2
TRANSPORT OF TRANSFORMER/REACTOR
Power Transformers and Reactors hereinafter referred as "Transformers,"
depending upon the restriction imposed by transport weight and/or other
considerations, have to be transported either filled with oil or nitrogen as per
the description given below. The transformer is loaded on wagon as per loading
gauge drawing prepared in each case.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
1.2.1
WITH OIL
The Transformer is filled with oil such that about 10% of the tank
volume is left clear for expansion to limit the excess internal air pressure to
0.35 kg/cm2. Fittings dismantled before transport are packed in packing cases
in line with shipping list.
All openings resulting from removal of fittings for shipment are sealed
with suitable gasketted blanking plates during transport.
The balance oil quantity required for the complete filling of the reactor is
supplied separately.
A transformer despatched according to this method can be stored at
site or elsewhere for one year provided, that all insulating materials are covered
with oil and silicagel breather is mounted and quality of oil is maintained as per
IS: 1866. Measures to be taken on reception at site are given clause 2.1
1.2.2
WITH NITROGEN
Large oil filled transformers/reactors are not normally oil filled during
shipping due to weight limitations. To protect the active parts against moisture
the transformer tank is filled with dry Nitrogen at a positive pressure of 0.175
kg/cm2 (2.5 psi) at BHEL works before despatch. The internal pressure at the
time of shipment is painted on the tank.
All openings resulting from the removal of fittings for shipment are
sealed with suitable gasketted blanking plates during transport.
A Transformer despatched according to this method should normally be
stored upto 3 months after arrival at site or elsewhere.
For control of gas pressure and maintaining the pressure during transport
and possible storage before assembling, the transformer is equipped with an
automatic device. This device is called two stage N2 regulator and is kept in a
steel box and mounted on the frame provided on tank side for keeping two
back up Nitrogen cylinders. Nitrogen regulator is connected to two cylinders
by copper tubes and to tank by a rubber hose as shown in the Fig. 1.1.
N2 regulator reduces cylinder high pressure of 120 to 140 kg/cm2 to
required low pressure of 0.175 kg/cm2 in two stages. One gauge provided on
the first stage indicates the cylinder pressure, whereas other gauge provided
on second stage indicates the tank pressure. Regulator is fixed at factory.
When tank pressure falls below 0.15 kg/cm2, due to leakage/fall of
ambient temperature, regulator automatically feeds the gas from cylinders, to
build up required pressure in the tank.
The gas consumption during transport and possible storage is difficult
to estimate as it depends on ambient temperature variation, possible leakages
as well as on the duration of transport and storage. However, two back up
cylinders are provided to meet the gas requirement. Normally one cylinder is
kept open and the other shut. When the pressure of first cylinder falls to 10
kg/cm2 this should be considered as empty and immediately its valve should
be closed and the valve of second cylinder should be opened.
When cylinder is required to be removed for refilling, disconnect copper
tubing from cylinder valve.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
Use only dry Nitrogen gas to IS:1747 with 50 ppm moisture and 1%
oxygen by volume.
If the storage time exceeds 3 months, the transformer is filled with oil
according to directions given in clause 2.5. If for some reason oil filling is not
possible, then nitrogen must be continuously maintained at a positive pressure.
Measures to be taken on receipt at site are given in clause 2.1.
1.2.3
INSTRUCTIONS FOR FILLING DRY PURE NITROGEN GAS WITH
BACK UP CYLINDERS (AT WORKS)
Lower the oil level to the minimum necessary to dismantle the items
(such as bushing and turrets) which must be removed for shipping.
Pull 500 mm mercury vacuum after blanking off all openings.
Break the vacuum by admitting dry nitrogen through a convenient valve
at the top of the tank and drain the oil completely.
Continue to supply nitrogen until it maintains a steady pressure of 0.17
± 0.02 kg/cm2 above the atmosphere.
Pressure of nitrogen gas shall be maintained at 0.17 ± 0.02 kg/cm2 at
same reference temperature. Pressure would be monitored by taking three
readings within 24 hours to ensure that there is no leakage of gas.
Shut off the gas supply valve and fit dry nitrogen back up cylinders
through nitrogen regulator valve.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
¦ÉÉMÉ-2
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SECTION-2
INSTALLATION
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
SECTION 2
2.
INSTALLATION
2.1
RECEPTION AND ASSEMBLING OF TRANSFORMER/REACTOR
DESPATCHED PARTLY DISMANTLED AND FILLED WITH NITROGEN.
To ensure that a Transformer will function satisfactorily it is important
that handling, lifting, storing and assembling are carried out with great care
and cleanliness by experienced personnel who know the various working
operations very well.
This section gives instructions how handling, lifting, storing and
assembling should be carried out. For large Transformers it is recommended
that the work is done by BHEL or is under supervision by experts from BHEL.
2.1.1
INSPECTION
In connection with receiving and unloading at site, and at the final storing
place before assembling, the transformers shall be inspected carefully. External
visible damages as dents, paint damages etc. may imply that the transformer
has been subjected to careless handling during transport and/or re-loadings,
and a careful investigation is therefore justified.
After the arrival of the material at receiving points, the customer should,
in case of possible damage/loss of any component, make the necessary claims
with the contractors representatives under intimation to supplier so that such
claims can be registered with the transport agents. Before unloading, the
condition of packing and of the visible parts should be checked and possible
traces of leaks verified (condenser bushings). If necessary, appropriate
statements and claims should be made.
Drums containing oil which have been despatched separately should be
examined carefully for leaks or any sign of tampering. All drums are despatched
filled up to their capacity and any shortage should be reported.
In order to protect the active part against moisture, the transformer
tank is filled with nitrogen during transport at an over pressure of 0.17 kg/
sq.cm (2.5 psi) approximately at room temperature.
Check immediately the gas pressure at the arrival. A positive pressure
indicates that the tank and the transformer components respectively are tight,
and that the active part including the insulation materials is dry.
If there is no positive gas-pressure, transformer should be immediately
filled with dry Nitrogen gas at a pressure of 0.17 kg/cm2 (2.5 psi) without loss
of time as per instructions given para 1.2.3
Otherwise, it should be checked if the core isolation is satisfactory and
that accessories packed separately have not been damaged during the transport.
Instructions for checking of the core isolation are given in clause 2.10
2.1.2
UNLOADING
Typical unloading arrangement of the transformer is shown in fig 2.1.
Whenever rollers/trolleys are supplied with transformer, movement of
transformer at site is carried out by mounting these rollers/trolleys. For mounting
of rollers refer roller mounting drawing included in Vol.I.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
Alternatively for movement of transformer from loading bay to actual
site of the equipment, skidding on greased rails etc. can also be resorted to.
2.1.3
STORING
Dismantled equipment and components are packed to be protected
against normal handling and transport stresses. The instructions for lifting
given on the packages, must be complied with to avoid damages.
Goods stored outdoors must not be placed directly on the ground, and
should be covered carefully with tarpaulin or similar material.
Oil drums should be stored in horizontal (lying) position with both the
bungs also in horizontal position.
2.1.4
LIFTING
Lifting devices on the transformer tank are dimensioned for lifting of the
complete transformer filled with oil. The positioning of the lifting devices,
permissible lifting angles, minimum height to crane hook and transformer
weight, appear from the OGA drawings. Check at lifting of complete transformer
that the lifting wires/ropes are not in contact with bushing or other components
on the cover.
For lifting with hydraulic jacks, the transformer is provided with jacking
pads dimensioned for lifting of complete transformer filled with oil. The position
of the pads appear on the OGA drawings. If active part is to be lifted refer
instructions given in clause 2.7.
2.1.5
LOCATION AND SITE PREPARATION
a) Reactor shall always be placed on concrete plinth without rollers as
per foundation plan drawing whereas transformer may be even placed
with rollers. Therefore it is very important to refer foundation drawing
before placing the transformer/reactor on final location.
b) Transformer/reactor should be placed on the foundation so that easy
access is available all around and diagram plates, thermometers, valves,
oil gauges, etc. can be easily reached or read. Adequate electrical
clearances are also to be provided from various live points of the
transformer to earthed parts.
c) ONAN type transformers/reactors depend entirely upon the surrounding
air for carrying away the heat generated due to losses. For indoor
installation, therefore, the room must be well ventilated so that the
heated air can escape readily and be replaced by cool air . Air inlets
and outlets should be of sufficient size and number to pass adequate
air to cool the transformer. The inlets should be as near the floor as
possible and outlets as high as the building will allow. Where necessary,
exhaust fans can be installed for the purpose.
d) The transformers should always be separated from one another and
from all walls and partitions to permit free circulation of air. In this
connection reference is also drawn to IS: 10028 (Part II).
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
e) Where rollers are not fitted, level concrete plinth with bearing plates
of sufficient size and strength can be adopted for outdoor transformers.
To prevent the formation of rust, it is essential to avoid presence of
air and water in the space between the plinth and the base of the
transformer by use of cretex or similar bituminous compound.
f) Where rollers are fitted, suitable rails or tracks should be used and
the wheels locked to prevent accidental movement of the transformer.
Where walls are provided, it should be ensured that the transformer
gets a good ventilation as mentioned above for indoor transformers.
Provision should be made for the emergency drainage of the oil from
the transformers (e.g. in case of fire in neighbouring apparatus or
bushing or the transformer tank), by surrounding the transformer plinth
with sump filled with small pebbles.
2.1.6
INTERNAL INSPECTION AND CHECK POINTS FOR ASSEMBLING
THE TRANSFORMER/REACTOR
(a) Check-points before starting assembly:
1. Conditions of leads.
2. Bracing, clamping of leads.
3. Connections.
4. Tapchanger checks.
5. General conditions of insulation.
6. Core check that it has not moved in transit.
7. Core-ground; this is checked with the megger after removing earth
connection.
8. CTs, including the secondary leads and their passage through metal
parts.
9. Check that shipping frame for bushings have been removed.
10. Check that coil position has not moved in transit.
11. Check for dirt, metal swarf, moisture.
12. Check that the bushing leads set without being too close to ground
or other points of different potential.
(b) Check-points during Assembly
By means of the Part list and the transformer/reactor OGA, the assembling
of a fully completed transformer is carried out according to the following
instructions. The following precautions are to be taken:
(i)
Fire-fighting equipment shall be available at the oil-treatment
equipment as well as at work on and adjacent to the transformer .
(ii) Welding work on or adjacent to the transformer shall be avoided, but
if this is not possible, the work shall be supervised by fire-protection
personnel.
(iii) Smoking on or near the transformer shall not be allowed.
(iv) Transformer tank, control cabinet etc. as well as assembling and oiltreatment equipment shall be connected with the permanent earthing
system of the station.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
(v)
(vi)
(vii)
(viii)
(ix)
(x)
(xi)
(xii)
(xiii)
(xiv)
(xv)
(xvi)
(xvii)
Check that there is no overpressure in the transformer when blanking
plates or connection lids are to be opened.
All loose objects, tools, screws, nuts etc., shall be removed from the
transformer cover before opening the connection and blanking lids.
All loose objects (tools, pencils, spectacles etc.,) shall be removed
from the boiler-suit pockets etc. before starting the work through
man holes.
Tools to be used inside the transformer/reactor -e.g. for tightening of
screw-joints- shall be fastened to the wrist or another fixed point by
means of cotton tape or string.
Tools with loose sleeves and tools with catches must not be used at
work inside the transformer.
Greatest possible cleanliness shall be observed at work inside the
transformer/reactor, and at handling of parts to be mounted inside
the transformer.
Fibrous cleaning material should not be used as it can deterioate oil
when mixed with it.
All components despatched separately should be cleaned inside and
outside before being fitted.
A transformer/reactor is best protected from damp hazard by
circulating warm, dry, deaerated oil through it until it temperature is
5° C to 100 C above ambient. This should be done before allowing
external excess to the interior of the tank. The warm oil should be
circulated all the time transformer is open to atmosphere,
Oil pump & all joints in the oil pipe work should be airtight to avoid
entrance of air through leakage joints.
The active part (core and winding) should be exposed to the
surrounding air as short time as possible. Open therefore only one
blanking plate or connection lid at a time for remounting of bushings,
valves etc.
Objects which-despite all precaution are dropped inside transformer/
reactor, must absolutely be brought up from the equipment.
Check that the oxygen content inside the transformer tank is minimum
20% if a person is to enter the tank.
2.1.7
ASSEMBLY OF WHEELS
Mounting of wheels under reactor/transformer is to be done as per roller
arrangement drawing. The reactor however in service, is to be placed on
plinth with anti-earthquake fastening without rollers. Transformer placement
can be with or without rollers as per applicable OGA/foundation drawing.
2.1.8
ASSEMBLY OF BUSHINGS
In case the bushings are mounted on turrets on the transformer/reactor
cover, they are either delivered mounted on their turret or -incase of large
bushings dismantled from the turrets.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
The turrets are often individually adapted; check therefore that they are
re-mounted in correct places, which appear from the OGA drawing and ,part
list.
Assembling of bushings is carried out according to the detailed
information documents available.
2.1.9
ASSEMBLY OF VALVES
Valves which may affect the loading gauge, or will be subjected to
damages, should be dismounted before delivery. Re-mount the valves -the
positionings appear from the OGA drawing and part list. The gasketting surfaces
shall be cleaned well and new gaskets fitted. Check that all valves are closed.
2.1.10
ASSEMBLY OF COOLING DEVICES
Valves which are not dismantled like shut-off valves for radiators, coolers
and possible headers shall be provided with blanking plates during the transport.
Remove the blanking plates when the assembling of the coolers is to be
started. Check first that the valves are closed.
Check that each radiator and possible header are assembled in the correct
positions according to OGA drawing. In case of OFAF or OFWF cooler mounting
shall be done as per the relevant leaflet given in Vol.I
The shut-off valves against the transformer tank shall be closed until
the oil-filling is started.
2.1.11
ASSEMBLY OF OIL CONSERVATOR
The conservator, which may be with or without aircell is assembled
either on the transformer, or on a separate frame. Before the conservator is
assembled it shall be checked that belonging equipment -e.g. Oil-level indicator
-functions satisfactorily.
The breather is connected to the oil conservator, and it is very important
that joints and couplings in the pipe between breather and conservator are air
tight. Refer Clause 2.6 for detailed instruction for oil filling.
2.1.12
ASSEMBLY OF PIPE WORK
Pipes with flanges for connection of conservator, radiators, as well as
pipes for equalising of turrets etc. are mostly delivered completely ready for
assembling according to OGA & part list.
In certain cases -e.g. at a separately assembled oil conservator -certain
fitting and welding of pipes and flanges on site is however required. Instruction
for such assembly of external pipes is given in Clause 2.3
2.1.13
FLANGES, BLANKING PLATES
When re-mounting blanking plates, connection flanges etc., the gasketting
surface shall be cleaned well and new gaskets fitted.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
2.1.14
ACCESSORIES
Accessories like cooling fans, pumps, OLTC and components for
supervision and control, oil-level indicator, flow indicators, gauges, Buchnolz
relay, PRV, thermometers etc. are assembled according to leaflet/description
valid for the components (refer Vol. I).
2.1.15
CONTROL CABLING
Re-assemble the control cables according to the drawing of wiring system
and connect the cable ends to terminal blocks in instruments, terminal boxes,
junction boxes and control cabinets according to valid connection diagram.
2.1.16
GASKETS
The sealing system normally used against oil and gas in BHEL's
transformers and belonging components has rubber gaskets in grooves and
nitrile rubber bonded cork gaskets at other places. Refer clause 2.8 for general
information and assembly instructions for gasket mounting.
2.1.17
OIL FILLING
The completely mounted Transformer is oil-filled according to directions
in Clause 2.5 & 2.6. The oil shall be treated according to Clause 2.4.
The lower and upper shut-off valves for radiators/coolers and possible
headers shall be open during evacuation and oil-filling.
If coolers are placed on suspension beams, which are mounted at right
angle to the tank, the suspension beams shall be supported against the ground
during the evacuation. Also radiators mounted on the tank wall shall be
supported in a similar way.
The hose for filling of oil is connected to the bottom valve of the
transformer which must not be opened until the hose has been deaerated and
completely filled with oil.
2.1.18
CLEANING & PAINTING
The transformer and its equipment are cleaned carefully from dirt, oil,
lubricating grease, and damaged surfaces are touch-up painted with the primer
paints and finish paints delivered as per clause 2.11.
2.1.19
EXCHANGE OF BUSHING
When exchanging a damaged bushing or other component on the cover
of a fully oil- filled transformer, we should proceed according to the following:
Close the valve in the pipe between the transformer and the oil
conservator. Pump oil from the transformer tank into the oil conservator so
that the oil quantity which need be drained off to lower the oil-level enough
below the transformer cover is pushed to the conservator. As the oil is being
transferred from tank to conservator, fill up the tank with dry nitrogen via a
suitable valve on the cover or in turrets.
Exchange the faulty bushing and transfer then the oil from the conservator
to the tank by opening the valve in the pipe between conservator and main
tank. De-air the bushings and turrets.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
2.2
STORING OF TRANSFORMER/REACTOR DESPATCHED FILLED WITH
NITROGEN
2.2.1
STORING BEFORE COMPLETE ASSEMBLING
The storing place should be easily accessible for inspection and
maintenance of the transformer. The bedding for the equipment should be
larger than its bottom surface and dimensioned for the load. The transformer
is placed on boardings or beams so that good ventilation is obtained underneath
the transformer bottom.
Before storing, the transformer is inspected according to directions in
Clause 2.1 "Reception and assembling of transformer/reactors despatched
partly dismantled and filled with nitrogen".
A transformer without remarks may be stored up to 3 months after
arrival at the site without oil-filling. During the storing time, the inert gas
(nitrogen) filling shall be maintained and pressure regulated, so that exposure
of active part to atmosphere is avoided.
If the storage time is judged to exceed 3 months, the transformer should
be provided with oil conservator including oil-level indicator and breather, and
oil-filled according to Clause 2.5. "Oil filling under vacuum". Certain valves
must be re-mounted to enable the oil-filling being carried out. Furthermore, at
the time at oil-filling of a completely assembled transformer, certain rules in
Clause 2.5 & 2.6 must be complied with absolutely.
Wherever possible it would be most desirable to keep the transformer
energized even at a low voltage so that its temperature is higher than the
ambient temperature. The low voltage may be applied under open circuit or
short circuit conditions. It may be ascertained whether partial cooling is required
in such a case. The oil quality should also be periodically monitored. If for
some reason, oil filling cannot be carried out after a storage period longer than
3 months, the nitrogen pressure shall be maintained and supervised carefully.
If the storage time without oil exceeds 18 months BHEL should be consulted
about measures to be taken.
2.2.2
STORING OF COMPONENTS AND ACCESSORIES BEFORE
COMPLETE ASSEMBLING
Independent of the duration of the storing time, the directions below
apply for dismounted components and accessories, as well as for material to
be used in connection with the assembling work.
(a) Storing indoors
In such a room, the following articles should be stored:
(i) Insulation material as paper, pressboard, bakelite, wood, cotton tape
etc.
(ii) Insulated details as paper-insulated conductors, pressboard insulated
shielding bodies etc.
(iii) Chemicals as solvents, glues, varnishes, hardeners etc.
(iv) Breathers, drying agents.
(v) Terminal boxes, connection boxes, control cabinets.
(vi) Gas relays, oil-level indicators, thermometers, pressure valves etc.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
(vii) MBox, OLTC motor drive, Fans, Pumps, Instruments & fittings.
(Heating elements provided shall be connected to supply)
(b) Storing outdoors
The below components may be stored outdoors. They should be placed
above ground and covered with tarpaulin etc.
(i) Oil-conservator with blanking plates for all openings.
(ii) Radiators and coolers with blanking plates for all openings.
(iii) Structures, A frames, Pipe supports, Supports for oil-conservators,
radiators, control cabinets etc.
2.2.3
SUPERVISION
During the storing time, the storing place, transformer/reactor
components and accessories are inspected regularly. Tap changer if provided
should be operated at 6 monthly intervals. Two or three runs from one end of
the range to the other and back are sufficient. Observations, readings, measures
and dates should be noted and BHEL should be contacted for directions about
possible measures. Check at even intervals -and further more at weather
changes as rain, storm, frost or thawing the foundation material (boardings,
beams etc.) and the condition of the ground.
Inspect the transformer/reactor periodically with regard to possible
external faults and/or rust-damage.
Check also that screws and nuts in sealing joints (covers, lids etc.) are
tightened. Check every second week that the connected-in heating elements
in control cabinets function.
If the Transformer is inert gas filled, one shall check every second week
the overpressure or inert gas consumption.
If the reactor is oil-filled, one shall take oil-samples after 6 months, and
then min. once a year. The oil is investigated with regard to Electric Strength
(BDV) and moisture content.
Inspect periodically stored components and accessories with regard to
possible , external damages and/or rust damages. If any touching up of paint
is required it should be carried out as per clause 2.11. Check at the same time
that insulation material and insulated details are not damaged or have become
dirty.
2.3
ASSEMBLING OF EXTERNAL PIPES
2.3.1
This technical description shall be applied at assembling of
transformers, when external pipes, for some reasons, are not fully completed
at delivery but require some kind of machining or fitting at site.
At the design occasion it is judged which details that can be made fully
completed in the workshop and which details that must be fitted into position
at site. Fully completed details are delivered with complete surface treatment.
Details of the pipe work despatched can be seen at shipping list.
2.3.2
BREATHER PIPE
The pipe is normally made of 15 NB painted steel pipe. The pipe shall be
cleaned carefully after machining. Supplementary surface treatment is, not
required normally.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
It is very important that the pipe is tight. Possible leakage will cause
moisture on the transformer with the service disturbances.
Mounting of the breather pipe shall be as per OGA drawing.
2.3.3.
OIL CONSERVATOR
For position of conservator along with necessary supports, refer OGA
drawing.
2.3.4
OIL CONSERVATOR PIPE
The pipe has dimension 80 mm usually and has welded flanges. The
pipe shall be painted internally with a yellow, oil-resistant paint, and externally
with a paint specified on the drawing. The pipes shall always incline upwards
minimum 2/3 degrees from the transformer.
2.3.5
EQUALISING PIPES
The pipe system in connection with the transformer cover is as a rule
manufactured in workshop. The pipe between transformer and conservator
may be pre-assembled.
The pipe is provided with weld-flanges. No pipe part is allowed to be so
long that internal inspection and cleaning is difficult to carry out. Besides
straight extensions, each pipe part may contain one bend.
The pipes shall always be placed with minimum 2/3 degrees inclining
upwards from the transformer. Internal surface treatment is with yellow oil
resistant paint. External surface treatment is made as specified on the drawing
as per specification. Cleanliness is extremely important.
2.3.6
COOLERS
The positioning of the radiators/coolers is indicated on OGA drawing.
These are positioned so that the highest point of the oil-pipe system is always
positioned below the bottom level of the conservator.
The pipe system is provided with filter valves at the start and finish to
enable pumping the oil through the system.
All places where air may be collected are provided with air release plugs/
valves.
2.3.7
COOLER PIPES
The pipe having dimensions as per OGA drawing and may be provided
with weld- flanges, expansion joints. No pipe part is allowed to be so long that
internal inspection and cleaning will be difficult.
The pipes shall be placed so that air release plugs will be positioned at
the highest point of the pipe part. The pipes shall be painted internally with a
yellow, oil-resistant paint and externally according to the paint as per
specification.
2.4
INSULATING OIL, QUALITY AND TREATMENT
2.4.1
QUALITY
The oil to be filled in transformer generally complies with the
requirements of the customer's specification. The characteristics of fresh oil
as per IS: 335 "Specification for New Insulating Oil" are given below:
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
CHARACTERISTICS AND PARAMETERS OF NEW
INSULATING OIL
Sr.No.
Characteristics
1.
Appearance
2.
3.
Density at 29.5°C
Kinematic Viscosity
at 27° C (max.)
Interfacial tension
at 27oC (Min)
Flash Point (Min)
Pour Point (Max)
Neutralisation value
(Total acidity), (Max)
Corrosive sulphur :
Electric strength
(breakdown voltage)
(Min)
New untreated oil,
4.
5.
6.
7.
8.
9.
(a)
(b)
10.
11.
12.
13.
a)
b)
14.
a)
b)
c)
d)
15
After filtration
Dielectric dissipation
factor (tan δ) at 90°C
(Max)
Water content (Max)
Specific resistance (Min)
at900C
at27OC
Oxidation stability
Neutralisation value
(Max)
Total sludge after
oxidation (Max)
Ageing characteristics
after accelerated ageing
(open beaker method
with copper catalyst).
Resistivity (Min)
at 900C
at 270C
Tan δ at 90°C (Max)
Total acidity (Max)
Sludge content by weight (Max)
Presence of oxidation
Unit
Requirement
gm/cc
The oil shall be clear,
transparent & free from
suspended matter or
sediments.
0.89
Cst
27
N/m
o
C
o
C
0.04
140
-6
mg/KOH/g
0.03
Non-corrosive
kV (rms)
kV (rms)
30
(If the above value is not
obtained the oil shall be
filtered in laboratory).
60
ppm
0.002
50
ohm-cm
ohm-cm
35x1012
1500 x 1012
mg/KOH/g
0.4
mg/KOH/g
0.10%
ohm-cm
ohm-cm
0.2x 1012
2.5 x 1012
0.2
0.05
0.05%
Oil shall not contain
inhibitor oxidation inhibitor
mg/KOH/g
Note: Methods of test shall be as per IS: 335
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
2.4.2
SUPPLY AND TESTING
The transformer oil is despatched directly to site from oil refinery. The
oil is thoroughly inspected and tested at oil supplier's works in presence of
BHEL and/or customer's representative or their authorised representatives.
Test certificate giving values obtained for all characteristics is issued.
2.4.3
HANDLING
The oil drums should be carefully handled at site, details of which are
given in Clause 9.1of IS:1866.
2.4.4
RECONDITIONING
Transformer oil is usually contaminated during handling, transport and
storage due to ingress of moisture and solid impurities. Hence, oil shall be
vacuum filtered separately at 50 0C to 60 °C using a suitable filtration machine
and a spare clean tank before filling in the transformer. Details of filtration are
given in Clause 9.2 of IS:1866. Oil treatment shall be terminated when the
following parameters are attained.
TABLE 2.1
kV Class of transformer
Recommended Permissible limit
Electric Strength
(BDV) in kV (Min)
Upto 145
245
420
60
65
70
Moisture Content
ppm (Max)
20
15
15
Storage tank shall be as per typical arrangement shown in Fig 2.2
Electric strength and moisture content shall be determined following
the test procedure of IS: 335.
2.5
OIL FILLING UNDER VACUUM
2.5.1
APPLICATION
Transformers and Reactors with vacuum-proof tanks shall be filled with
oil according to this method.
2.5.2
STORING TIME
Generally it applies that Transformers and reactors which during transport
are filled with dry nitrogen on arrival at the site shall be evacuated and oil
filled. Before storing, the equipment shall be inspected according to the
directions given in Clause 2.1 "Reception and assembling of transformer/reactor
despatched partly dissembled and filled with nitrogen". During the storing
time, overpressure shall be maintained, and nitrogen consumption checked
according Clause 2.2.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
2.5.3
FLOW CHART FOR HANDLING
In Annexure 2.1 is given a flow chart of handling procedures. The pressure
should be measured at different times. The pressure is OK if it is maintained
according to instructions given in Clause 2.2. Reference is also drawn to para
9.0 of IS: 1866 regarding handling and filling of oil.
2.5.4
UNITS
Annexure 2.1 gives the relation between different units.
2.5.5
EVACUATION
The transformer tank (excluding cooler bank & conservator) shall be
evacuated to a pressure of 1.00 torr. max. The pressure shall be maintained
for the time given in Table 2.2.
TABLE 2.2
VACUUM TREATMENT
System Voltage
Evacuate and hold
vacuum for
Standing time after oil
circulation before
application of voltage
kV
hours
hours
Upto 145
12
12
145 & upto 420
24
48
Above 420
36
120
The equipment required for vacuum treatment and oil-filling under vacuum
should generally be as per Annexure 2.2. The transformer tank and electrical
terminals shall be earthed for safety reasons.
No electrical test on the Transformer is permitted during the evacuation.
Fig. 2.3 shows a typical example of pipe work and valve positioning.
Oil conservators are not evacuated. Valve 7 shall be closed. Valve 6
shall be open unless a breather is fitted.
2.5.6
OIL FILLING
2.5.6.1 OIL QUALITY
The transformer/reactor shall be filled under vacuum with oil which has
been purified and degassed according to Clause 2.4
2.5.6.2 OIL FILLING IN MAIN TANK
The oil shall be heated to a temperature of 500- 60°C measured at the
filter outlet valve. The pressure during the filling shall be max. 1 torr. During
the oil-filling, a transparent plastic tube (5) can be used as an oil-level gauge.
The tube which should be a wall thickness of 5-8 mm, may be connected to a
top and a bottom valve on the transformer.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
Oil-filling of the tank is done through valve (12) at a low level on the
transformer and at a maximum rate of 4-5 kL/hour. The pressure in the oil
pipes shall be kept positive and shall be checked by a manometer 13 (if
provided). When the oil-level has reached about 50 mm below the cover/the
vacuum pump is stopped it is preferred that dry nitrogen is introduced in the
tank by opening valve (8). Valve (7) is then opened .and valve (6) closed and
the filling is continued in tank and conservator until the correct oil- level has
been reached in the conservator.
Conservator supplied with rubber air cell shall be filled according Clause
2.6. For oil filling in diverter switch assembly of a OLTC refer leaflet (Vol.1).
Separate vacuum-proof cooler system/radiators can be evacuated for
about 1-2 hours and filled separately with purified and degassed oil. The oil is
then circulated through the vacuum filter at least twice via drain valves as
near as possible to the transformer. When the oil circulation has been completed
the valves between coolers and main tank shall be opened.
Care should be taken to keep all air release plugs and valves open to
allow escape of trapped air during oil filling operation. These valves/plugs
should be closed after completion of oil filling.
2.5.7
HOT OIL CIRCULATION
To facilitate oil-penetration and absorption of possible gas bubbles, the
temperature of transformer shall-after completed oil-filling-be increased by
circulating the oil through the vacuum filter and with circulation direction
according to Fig. 2.4.
The oil will be circulated through a vacuum filtration machine till the
parameters are attained as per table 2.3 below.
TABLE 2.3
kV Class of
Transformer
Recommended Permissible Limits
Electric
Strength
(BDV) in
kV (min)
Moisture
Content
ppm (Max)
Resistivity *
at 90oC
(Ohm-cm)
Tan delta*
at 90oC
Upto 72.5
145
40
50
25
20
1x1012
1x1012
0.05
0.05
245 and 420
60
15
1x1012
0.05
* Subject to availability of testing facility at site.
Method of test for Electric Strength and moisture content shall be as
per IS:335.
CAUTION:
The temperature during oil circulation should not increase beyond 70oC
otherwise this may cause oxidation of oil.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
2.5.7.1 SAMPLING
Oil sampling at various stages shall be done in accordance with IS:
6855. when samples are taken from transformer tank, oil will be drawn from
bottom of the tank. When it is desired to know gas content and composition
of dissolved gases in transformer oil before commissioning for reference
purposes (required for interpretation of Dissolved Gas Analysis results during
service), sampling shall be done as per IS 9434.
2.5.8
STANDING TIME
Standing time is the time between 'finished oil circulation' and
'energisation'. The time appears form table 2.2.
2.5.9
FINAL OIL FILLING OF TRANSFORMERS/REACTORS DESPACTCHED
OIL FILLED.
Smaller transformers/reactors are often factory-filled with degassed oil
up to about 10% below the cover and transported in this condition. The final
filling up to the correct level in the conservator is made at site.
2.5.9.1 TRANSFORMERS/REACTORS WITH SYSTEM VOL TAGE < 36 KV
Previously degassed oil (e.g., at the factory) stored in tight drums may
be used for the filling. Check the dielectric strength of the oil which should be
as per Cluase 2.4.4. If accepted, the oil is pumped into the conservator and in
this way fed into the tansformer. To prevent any free water in the drums from
entering the reactor the opening of the suction tube must lie 0.1 m above the
lowest point in the drum. A suitable valve on the cover and/or valves or upper
tightening nuts at the bushings have to be opened for complete removal of air
below the cover and in the bushings. When the oil is seeping out at these
points, shut the valves and tighten the nuts at the bushings.
2.5.9.2 TRANSFORMERS/REACTORS WITH SYSTEM VOLTAGE > 36 KV
The filling is performed as described above, but at least a paper filter
must be used for drying the oil.
2.6
OIL FILLING INSTRUCTIONS FOR CONSERVATORS WITH AIR CELL
2.6.1
INTRODUCTION
In all transformers specially in high voltage class, maintenance of
insulating oil notably its dielectric property forms one of the determining factors
of reliability of equipment in service. Oxidation and contamination of
transformers/reactor oil can be avoided in a simple and effective way by use
of above oil preservation system. The complete system is known as
"Conservator with Air Cell".
In this oil preservation system a flexible air cell made of oil resistant
nitrile rubber is placed inside the conservator and floats on the oil surface. The
air cell inflates or deflates as the oil level in the conservator falls or rises
depending on the ambient temperature and load on the reactor. The inside of
the rubber bag (Air Cell) is put into communication with atmosphere by means
of a silica gel breather which ensures dry atmosphere inside the air cell. In
addition to the above this system provides following advantages.
(i) It avoids saturation of absorbed gases.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
(ii)
As no gas is used in this system, which operates at constant
pressure, this formation of gas bubbles at low ambient temperature
and load is eliminated. The system thus preserves the oil quality
particularly its dielectric properties.
The conservator with air cell is provided with a magnetic oil gauge
having one electrical contact. The indication shown on the dial physically
corresponds to the oil level in the conservator which is due to balance of
static pressure between the oil of the conservator and the atmospheric air
inside the air cell. This system is also provided sometimes with a set of pressure
and vacuum valves. These valves operate to pass either oil or air in the event
of over filling or under filling the conservator during installation.
2.6.2
DESCRIPTION OF OPERATION
Figure 2.5 indicates the general arrangement of oil preservation system,
The oil connection between conservator and transformer tank is made through
Buchbolz relay and valves are provided in between.
The flexible air cell is connected to the top of the conservator through
gasket ted joint. Under normal condition air cell is completely surrounded by
oil and floats in the conservator. The air cell inflates/deflates as the oil volume
changes. The float of the MOG which is always in contact with under side of
the air cell moves up and down and indicates the oil level. The cell will sink in
the remote event if it is damaged and MOG alarm will operate. The conservator
then functions as a conventional conservator without effecting the performance
of the transformers/reactor.
2.6.3
INSTALLATION
This system is shipped separately from main tank. The air cell is shipped
fitted in the conservator. A low positive pressure of less than .07 kg/sq.cm (1
psi) is maintained to avoid excessive movement of air cell in the conservator
during transit. MOG is also shipped fitted on the conservator. Install the
conservator and associate parts except breather as per transformers/reactor
outline drawings and assemble oil pipe work.
2.6.4
OIL FILLING
The following procedure is recommended.
(i) Close and blank the valve (14) to isolate the conservator from main
tank. Fill the oil in transformer under vacuum upto Buchholz level as
per instructions given else where. '
(ii) After filling the oil in transformer and breaking the vacuum, oil can
be filled in the conservator either through reactor or by drain valve
(4).
(iii) Remove the inspection cover (11) provided on the side of the
conservator and check the air cell assuring that it is inflated. The air
cell must remain in fully inflated condition during oil filling operation.
If the air cell is found deflated fit the inspection cover and inflate the
air cell with dry air/nitrogen gas to 0.035 kg/sq.cm max. through
connection (8). A gauge may be put by removing plug (10). After
filling close these connections.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
(iv) Remove air release plugs (5) (6) and (7) provided on top of the
conservator.
(v) Slowly pump the oil through the main reactor/drain valve (4).
Temporarily stop filling operation when oil starts coming from opening
(5) and (6) after ensuring that no air bubbles come out through these
air release holes. Fit the two air release plugs.
(vi) Continue oil filling till oil start coming from air release plug (7) stop
oil after ensuring that no air bubbles come out. Fit the plug (7).
(vii) Now release the air pressure held inside the air cell from point (8)
and continue oil filling until magnetic oil gauge (3) indicates 35°Clevel.
(viii) Remove oil pump and connect air cell to breather (9) from point (8).
Also remove pressure gauge and put plug (10).
(ix) The system is now properly filled. Air release plugs (5), (6) and (7)
are fitted in normal operation.
2.6.5
(i)
PRECAUTIONS
Oil filling in the conservator and also draining whenever required
must be done very slowly. During oil filling, pressure in the air ce]l
should not exceed 0.1kg/sq.cm (1.5 psi).
(ii) If a pressure or vacuum is ever applied to the main reactor tank the
conservator must be disconnected and a blanking plate fitted on
shut off valve.
(iii) Do not weld on conservator to avoid damage to the air cell.
(iv) Once all the air has been driven out during oil filling in the conservator
do not remove air release plugs (5), (6) and (7). Otherwise air will be
sucked inside the conservator.
2.6.6
MAINTENANCE
Little maintenance work will normally be required except routine visual
inspection. However, it is desirable to check the breather opening to ensure it
is not blocked. Further silicagel should be regenerated/replaced when its colour
changes from blue to pink.
2.6.7
AIR CELL
Air cell is made from Nylon fabric coated with Nitrile rubber, In the
event it becomes necessary to replace or test the air cell for leaks the following
method is recommended.
(i) De-energise the transformers/reactor.
(ii) Isolate the conservator by closing the valves (14).
(iii) Drain the oil from the conservator through the valve (4) by removing
air release plugs (5) and (6).
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
(iv) Remove inspection cover (11) if necessary, Install the pressure gauge
on point (10).
(v) Pressurise the air cell (2) by dry air/nitrogen to a max. pressure of
1.5 psi and seal. Check the pressure for 6 hours.
(vi) If leaks are found, air cell to be repaired by patching or replaced by a
new air cell.
(vii) For taking out the air cell from conservator, remove the air cell flange
and loops from hooks provided on inside of the conservator top.
Collapse the air cell slowly and fold, remove it from conservator very
carefully.
(viii) In the event air cell is not available immediately, conservator may be
used as a conventional conservator.
2.6.8
OIL PRESSURE TEST
Oil pressure test on fully erected Transformer/Reactor to be conducted
as per annexure 2.3 before hot oil circulation.
2.7
UNTANKING OF ACTIVE PART
2.7.1
GENERAL
If for some reason it becomes necessary to untank the active part (core
and windings) of a large reactor/transformer, it ought to be done under
supervision by BHEL erectors. Universal instruction for the untanking procedure
cannot be given, as the design practices of large equipment vary. The following
general directions are, however, applicable in most cases.
The untanking must be done indoors. If there is no suitable hall available,
lifting can be done in the temporarily arranged room. e.g. a tent. The oil & the
internal parts of the transformer must not in any case be exposed to rain or
humidity.
In case of bell shaped transformer, only bell cover is lifted for access to
active part.
2.7.2
OIL DRAINAGE
Drain off the oil from the transformers/reactor either partly or completely.
2.7.3
DISCONNECTING
Disconnect leads to bushings, current transformers, winding temperature
devices and earthing leads between active part and cover or tank side.
Disconnections mentioned above can usually be made through handholes
in cover or tank side.
2.7.4
REMOVAL
Remove all large bushings, cover mounted conservator and lightning
arrestors (if provided). Break all connections between cover and tank-piping to
oil conservator and cooler thermometers etc.
Remove the cover bolts. If the cover is welded to the tank flange, free
the cover according to directions given in Clause 2.9.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
2.7.4.1 COVER
When lifting the cover use the cover-lifting eyes which are designed for
a minimum angle of 60 degrees between sling branches and the horizontal
plane. The length of the sling should therefore be sufficient for at least this
angle.
Place the cover on suitable wooden supports and in such a way that
thermometer pockets, small bushing etc. underneath the cover are not damaged.
No grinding or cleaning up of the tank flange is to be carried out before
the active part is lifted out of the tank.
2.7.4.2 UNTANKING
Loosen locking devices, if any, between top core clamps and tank side.
Lift the active part by means of lifting eyes or lifting lugs provided on
the top core clamps. The untanking height is shown on the outline drawing.
To avoid damages on the active part it is important that it is centered carefully
in the tank during lifting procedure.
After untanking, place the active part on a horizontal foundation.
2.7.5
RETANKING
Grinding or/and cleaning up of the tank flange has to be done before the
active part is lowered into the tank. Check that the tank inside is free from
contaminations.
Retanking is then done in the reverse order that is outlined above. Note
that guiding pins or blocks are welded to the tank bottom to prevent the
active part from moving in the tank. When lowering the active part, check that
it fits exactly the guiding pins or blocks.
2.7.6
REASSEMBLING
Wipe the underside of the cover free from any dirt or foreign matter
before lifting it into correct position above the reactor tank. Lower the cover
the last few inches exactly into position without sliding on the gaskets.
Reassemble bolts nuts of supporting devices. Weld the cover when the
welded construction is used. Reassemble Bushings, conservator etc., and
reconnect pipings, leads to bushings, current transformers, etc. Reassemble
inspection covers.
After the transformer is completely assembled, it may be necessary to
dry it before oil fining- see clause 2.5.
2.8
MOUNTING OF GASKETS
2.8.1 The gaskets have a circular/flat cross-section and are made of oil
and heat- resistant synthetic nitrile rubber/nitrile rubber bonded cork. For small
gaskets, O-rings are used with diameter 3,5.0 or 8.0 mm, while round rubber
cords with diameters 8,12 or 19 mm are used for large gaskets.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
The groove is normally milled or turned, but for large flanges the groove
is created by means of steel bars welded on top of the flange. The width of
the groove is slightly smaller than the cross-section diameter of the gasket in
order to keep the gasket in position during the assembling work.
Opened sealing joints may be sealed again using the same gasket provided
that the same has not been damaged. If the gasket has become hard or got
small cracks on the surface, it is recommended to change the gasket by a new
one.
When handling and lifting flange, cover etc. with gasket grooves, care
should be taken when using tools and lifting devices to avoid that the grooves
getting damaged or deformed.
Before assembling of groove gaskets, it is checked that the grooves and
contact-surface in the joint are free from foreign particles and that the paint is
free from thick coatings, trickles and drops.
When assembling the rubber cord in the groove, the cord length shall be
continuous . The gasket is given a small surplus length to compensate for
shrinkage.
The gasket is pressed down into the groove without stretching or
slackening.
To prevent the gasket from falling from the groove on vertical surfaces,
the gasket may be spot-glued to the bottom of the groove.
The screws in the sealing joint shall be tightened so that an even pressure
is obtained on the gasket. This is obtained preferably by means of a moment
spanner. Rubber gaskets in grooves need not normally be re-tightened.
Above description is followed generally for turrets, inspection cover
etc. For main tank rim joint, LV turrets of Generator Transformers where metallic
stops are provided, nitrile rubber bonded cork is used, for which following
instructions shall apply.
2.8.2 (i) Gaskets when supplied loose, have no bolt holes in them. They
are usually cut to the size and shape required, although they may
be supplied as straight, angled pieces from which complete gaskets
can be built up.
(ii) Scarfed joints should be used. A 40 mm scarf in 5 mm thick
material is recommended. Joints should be located away from
comers and bolt holes, and should be well bonded, smooth and
free from local thickening. Neoprene solution is used as an adhesive
for joints.
(iii) Gaskets are best stored in hermetically sealed containers in a cool
place. They must be protected from damp, oil and grease(iv) To make a gasket joint, first clean the metal surfaces ensuring
that they are free from oil, rust, scale etc. Using one of the flanges
as a template, punch the necessary bolt holes. Insert the bolts
and tighten the bolts sequentially, a little every time so that uniform
pressure is exerted on the gasket until the gasket is compressed
to about 2/3 of its original thickness. Joints should not be subjected
to pressure until tightening is complete. If care is taken in making
joints, and in handling the gasket, it is possible to break and remake a joint several times, using the same gasket.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
(v) For making leak proof and good gasket joints, it is necessary that
uniform pressure is achieved all over the gasket after matching
rims/ flanges have been clamped with bolts/studs.
Following instructions be followed for proper tightening of bolts/studs.
a) Tighten lightly the bolts/studs diagonally in the sequence as shown
in the fig. 2.6.
b) Tighten again bolts/studs in the same sequence with the torque
given below :
Bolt/Stud
Max. Torque
Size
(Kg-M)
M 10
1
M 12
2
M 16
6
M 20
12
M 24
20
M 30
30
In case of metallic stoppers tighten until metal to metal contact is achieved.
c)
Do not overtighten, otherwise gasket will get crushed.
2.9
WELDED COVER (IF APPLICABLE)
In order to obtain a good sealing between the transformer tank and the
cover a welded joint is recommended. The welding is performed in a certain
way to permit opening and new welding repeated a number of times. The
chiselling up and re-welding will take about the same time as dismantling and
reassembling of bolted cover .
If the welded cover for any reason has to be removed proceed as follows:
2.9.1
OPENING THE COVER
When opening the cover the welding joint should be removed by a suitable
grinding wheel. The cover should be clamped to the frame by means of Gclamps to prevent iron chips from penetrating into the tank. Any parts of the
weld which may possibly remain on the tank flange should be removed by a
chisel to enable a good result of the re-welding.
2.9.2
REASSEMBLY
When fitting the cover again cork-rubber gaskets, 25 x 5 or as specified
are fitted on the tank flange, see fig. 2.7.
The gaskets are kept in the correct position with glue base on rubber
base. The cover should be clamped to the tank flange by means of G-clamps
evenly distributed along the flange with about 600 mm spacing. Tack welding
is carried out with about 100 mm spacing. An extra G-clamp is used during
the tack welding and is moved along the flange during the progress of the
work. The continuous weld is then applied. Finally the weld should be cleaned
and painted.
WARNING
When welding, a fire-extinguishing equipment should be available, and
the work supervised by fire-protection personnel.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
2.10
EARTHING OF ACTIVE PART AND CORE INSULATION TEST
2.10.1
REACTORS
The ground-connection terminals for the reactor active part are located
in a box at the tank end, close to the bottom. Please see fig. 2.8.
The terminal are protected by a cover. The cover can be removed with
the tank oil- filled.
The terminal box contains a terminal block with three terminals.
-The terminal marked CL is connected to the core laminations.
-The terminal marked CC is connected to the core clamps.
-The terminal marked G is connected to ground (the tank).
For the core-insulation test, remove the cover. Disconnect the closing
link that connects the two terminals CL-G. Use perferably 3500 V direct voltage
between CL and CC + G. The tank shall be grounded during the test. The
insulation value after 1 min. test- time shall be minimum 1000 kohms. There
is no general requirement on the insulation level CC-G .
2.10.2
TRANSFORMERS
For checking core insulation incase of transformers refer Fig. 2.9 for
connection details.
2.11
TOUCH-UP PAINTING
2.11.1
PURPOSE
A basic principle at touch-up painting should be to restore a damaged
paint coat on a surface to the same quality and finish as of the surrounding
surface. The touch-up painting should be limited to a surface as small as
possible.
2.11.2
CLEANING
Both damaged and surrounding surface should be cleaned so that all
grease, dust and other impurities will be removed.
2.11.3
GRINDING OF DAMAGES
Large damages and defects are ground by means of a coarse abrasive
paper, e.g. No.100. The surface is then ground with a finer paper in connection
with the damage, e.g. 150 or 180. Damages that are limited to the paint coat
only, should be ground off completely at which glazing can be avoided.
2.11.4
PRIMER PAINTING
Damages on the primer paint and grinding down to the steel surface
should be painted with two coats of anti-corrosive priming paint.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
2.11.5
FINISHING PAINT
Two coats of finishing paint should be applied as per specification which
is generally light grey shade No.631 of lS: 5. Please refer Table 2.4 for suppliers
reference.
TABLE 2.4
SI
Suppliers
No. Name
Suppliers Reference
Anti corrosive
High Quality full
priming paint for
gloss outdoor
outside painting
finishing paint
1.
Addison
IS 2907
Shade 631 of IS 5
jasmine yellow
shade no.397
of IS 5 for
inside painting
2.
Asian
32/F 3257
Apcolite synthetic
-
3.
Berger
BPL Red oxide
Zinc Chromate
Luxol 3H1 Glass
synthetic enamel
-
4.
Alkali
Chemicals
32-781
Dulux synthetic
enamel
-
5.
Garware
PR-4460
-
-
6.
Shalimar
Sample No. 5999/1
Superlac synthetic
7377/1
7.
Goodlass
205/023
500 Series
548/101
Oil resistant air
drying synthetic
enamel
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
ANNEXURE 2.1
FLOW CHART FOR HANDLING
ARRIVAL AT
SITE
MEASUREMENT OF
PRESSURE
ASSEMBLY
EVACUATION AND OIL
FILLING
OIL-CIRCULATION
THROUGH FILTER
STANDING TIME
ACCORDING TO TABLE 2.2.
VOLTAGE APPLICATION
Relationship between different units
1 bar = 105 Pa = 750 Torr = 14.5 psi = 1.02 kg/sq.cm
1 Torr = 1.33 mbar = 0.133 kPa
1 kPa = 103 Pa = 10 mbar = 7.501 Torr
1 MPa = 106 Pa
Force
1 kp = 9.807 N
Volume
11itre = 0.26 US gallons
1 US gallon = 3.781itres
11itre = 0.22 Imp gallons
1 Imp = 4.551itres gallon
Temperature
C = 5 x (F-32)/9
F = 9 x (C+32)/5
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
ANNEXURE 2.2
EQUIPMENT FOR OIL-FILLING UNDER VACUUM
(i)
High-vacuum 2 stage oil filtration plant provided with thermostatcontrolled oil heaters and vacuum-proof hoses with independant
vacuum pumping system for tank evacuation. Capacity: 6000 lph.
(ii)
Oil-storage tanks provided with silica-gel breathers and inlet/outlet
valves for oil circulation. Recommended capacity 20 kL -30 kL (Clause
2.4)
(iii) Vacuum gauges provided in filtration plant.
(iv) Equipment for measurement of electric strength (BDV) of oil- 100 kV
set.
(v)
Equipment for moisture content of oil.
(vi) Equipment for measurement of Resistivity and Tan delta at 90o C.
(vii) Oil-sampling cans or bottles.
(viii) Transparent vacuum-proof tubes for checking of oil-level during oil
filling.
(ix) Valves, fittings, gaskets etc.
(x)
Dry nitrogen cylinders.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
(1)
(2)
HAULAGE HOLE- JÉÓSÉxÉä Eäò ʱɪÉä ÊUôpù
(3)
JACK- VÉäEò
(4)
(5)
(6)
(7)
(8)
RLY. WELL WAGON- ®äú±É´Éä ´Éä±É ´ÉäMÉxÉ
JACKING LUG- VÉäËEòMÉ ±ÉMÉ
90 LB. RAIL - 90 B±É ¤ÉÒ ®äú±É
SUPPORTS TO PREVENT SLIPPING- Ê¡òºÉ±ÉxÉ ºÉä ¤ÉSÉxÉä Eäò ʱɪÉä +ÉvÉÉ®ú
GROUND LEVEL- ¦ÉÚ欃 ºÉiɽþ
THESE SLEEPERS WILL BE PUT AT SITE AT THE TIME OF UNLOADING- <xÉ º±ÉÒ{É®úÉå EòÉä =iÉÉ®úxÉä
Eäò ºÉ¨ÉªÉ ºÉÉ<]õ {É®ú ®úJÉå
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
Fig. 2.1 Typical Unloading Arrangement of the Transformer
ÊSÉjÉ 2.1 ]ÅõÉƺɡòɨÉÇ®ú EòÉä =iÉÉ®úxÉä EòÒ ´ªÉ´ÉºlÉÉ EòÉ xɨÉÚxÉÉ
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
1.
2.
3.
4.
5.
6.
OIL SAMPLING VALVE 15 mm 2 Nos. iÉä±É
ºÉä¨{É˱ÉMÉ ´Éɱ´É 15 ʨɨÉÒ. 2 xÉÆ.
FILLTER VALVE 50 mm 2 Nos. Ê¡ò±]õ®ú ´Éɱ´É 50 ʨɨÉÒ. 2 xÉÆ.
DRAIN VALVE 80 mm 1 No. bÅä÷xÉ ´Éɱ´É 80 ʨɨÉÒ. 1 xÉÆ.
DRAIN PLUG 15 mm 1 No. bÅä÷xÉ {±ÉMÉ 15 ʨɨÉÒ. 1 xÉÆ.
MAN HOLE 1 No. ¨ÉèxÉ ½þÉä±É 1 xÉÆ.
VACUUM APPLICATION VALVE 25 mm 1 No. ´ÉäCªÉÚ¨É ´Éɱ´É 25 ʨɨÉÒ. 1 xÉÆ.
7. BUSHING MOUNTING HOLES WITH BLANKING FLANGE 3 Nos.
¤ÉÖ˶ÉMÉ ±ÉMÉÉxÉä Eäò ʱɪÉä ÊUôpù ¤±ÉåËEòMÉ }±ÉéVÉ ºÉʽþiÉ 3 xÉÆ.
Fig. 2.2 Typical Arrangement of oil Storage tank
ÊSÉjÉ 2.2 iÉä±É ºÉÆOɽþ Eò®úxÉä EòÒ ]ÆõEòÒ EòÉ xɨÉÚxÉÉ
1.
Oil-filtering plant with heater
(1)
½þÒ]õ®ú Eäò ºÉÉlÉ iÉä±É Ê¡ò±]õË®úMÉ {±ÉÉÆ]õ
2.
Oil-storage tank
(2)
iÉä±É ºÉÆOɽþ Eò®úxÉä Eäò ʱɪÉä ]åõEò
3.
High-vacuum pump
(3)
=SSÉ ÊxÉ´ÉÉÇiÉ {ɨ{É
4.
Conservator
(4)
EòxVÉ®ú´Éä]õ®ú
5.
Oil-level indicator
(5)
iÉä±É-ºiÉ®ú ºÉÚSÉEò
6.
Valve
(6)
´Éɱ´É
7.
Valve
(7)
´Éɱ´É
8.
Valve
(8)
´Éɱ´É
9.
Valve
(9)
´Éɱ´É
10. Valve
(10) ´Éɱ´É
11. Dry-N2 container
(11) ¶ÉÖ¹Eò xÉÉ<]ÅõÉäVÉxÉ ºÉÆOɽþEò
12. Valve
13. Manometer
Fig. 2.3
ÊSÉjÉ 2.3
(12) ´Éɱ´É
(13) ¨ÉäxÉÉä¨ÉÒ]õ®ú
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
TRANSFORMER
REACTOR
VACUUM
FILTER
]ÅõÉƺɡòɨÉÇ®ú/Ê®úBC]õ®ú ]ÆõEòÒ
´ÉèCªÉÚ¨É Ê¡ò±]õ®ú
Fig. 2.4
ÊSÉjÉ 2.4
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
OIL PRESERVATION SYSTEM WITH AIR CELL
+É<±É Ê|ÉVÉ´Éæ¶ÉxÉ ÊºÉº]õ¨É BªÉ®ú ºÉä±É Eäò ºÉÉlÉ
GENERAL ARRANGEMENT
ºÉɨÉÉxªÉ ´ªÉ´ÉºlÉÉ
SL.No.
Gò. ºÉÆ.
DESCRIPTION Ê´É´É®úhÉ
1.
AIR CELL BªÉ®ú
ºÉä±É
2.
MAGNETIC OIL GAUGE ¨ÉäMÉxÉäÊ]õEò
3.
BREATHER ¥ÉÒnù®ú
4.
DRAIN VALVE bÅä÷xÉ ´Éɱ´É
5.
AIR RELEASE PLUGS
+É<±É MÉäVÉ
BªÉ®ú Ê®ú±ÉÒVÉ {±ÉMÉ
6.
FLANGE FOR TRANSFORMER CONNECTION ]ÅõÉƺɡòɨÉÇ®ú
7.
AIR CELL SUPPORTING LUGS BªÉ®ú
8.
OIL
9.
PRESSURE GAUGE CONNECTION (WITH PLUG) |Éä¶É®ú
ºÉä VÉÉäc÷xÉä Eäò ʱɪÉä }±ÉåVÉ
ºÉä±É Eäò +ÉvÉÉ®ú ±ÉMÉ
iÉä±É
10. PRESSURE GAUGE |Éä¶É®ú
MÉäVÉ EòÉ EòxÉäC¶ÉxÉ ({±ÉMÉ Eäò ºÉÉlÉ)
MÉäVÉ
11. BREATHER CONNECTING FLANGE ¥ÉÒnù®ú
VÉÉäc÷xÉä ´ÉɱÉÒ }±ÉåVÉ
12. CONSERVATOR END COVER EòxVÉ®ú´Éä]õ®ú Bxb÷ Eò´É®ú
13. INSPECTION COVER <xºÉ{ÉäC¶ÉxÉ
Eò´É®ú
Fig. 2.5
ÊSÉjÉ 2.5
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
Fig. 2.6
ÊSÉjÉ 2.6
Fig. 2.7
ÊSÉjÉ 2.7
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
Fig. 2.8
ÊSÉjÉ 2.8
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
Fig. 2.9
ÊSÉjÉ 2.9
NOTE:
1. WHILE DISCONNECTING/EARTHING CONNECTION BETWEEN CORE/YOKE
CLAMP & TANK, REMOVE THE LINK.
1. EòÉä®ú/ªÉÉäEò C±Éä¨{É B´ÉÆ ]ÆõEòÒ EòÉ ¦ÉÚºÉÆ{ÉEÇò ʴɪÉÖHò Eò®úxÉä Eäò ʱÉB ªÉ½þ Eòb÷Ò ½þ]õÉ nåù*
2. WHILE PUTTING IN SERVICE PLACE LINKS IN POSITION.
2. {ÉÊ®úSÉɱÉxÉ Eäò ºÉ¨ÉªÉ ªÉ½þ Eòb÷Ò VÉMɽþ {É®ú ±ÉMÉÉ nåù*
Earthing Connections from core and top yoke clamp.
EòÉä®ú B´ÉÆ ]õÉì{É ªÉÉäEò C±Éä¨{É ºÉä ¦ÉÚºÉÆ{ÉEÇò ªÉÖÊHò
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
ANNEXURE 2.3
PRESSURE TESTING OF TRANSFORMER / REACTORS AT SITE
1. After completion of oil filling, lock PRV and pressurise the air cell by
filling nitrogen/ dry air to 5.0 p.s.i. (0.35 Kg/cm.sq.).
2. Maintain above pressure for at least 12 hours.
3. Inspect all joints for leakage, if any.
4. Record pressure testing as given below.
5. After pressure testing unlock PRV and release the nitrogen/ dry air
pressure of air cell.
NOTE: In case of conventional oil preservation system (without air cell)
pressurise conservator by filling nitrogen/dry air in conservator .
RECORD OF PRESSURE TESTING AT SITE
1. Date & Time of testing
DATE
TIME
(a) Started on
.........
.........
(b) Finished on
.........
.........
2. Initial pressure
....................................
3. Pressure after 12 hours
....................................
4. Leakages observed if any
location of leakages
YES /NO
....................................
5. If leakages are observed. Same to be arrested and pressure testing
is to be repeated.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
¦ÉÉMÉ-3
Eò¨ÉÒ¶ÉËxÉMÉ
SECTION-3
COMMISSIONING
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
SECTION 3
3
COMMISSIONING
3.1
TESTING AFTER ASSEMBLY OF THE TRANSFORMER/ REACTOR
AT SITE.
After the transformer/reactor has been assembled at site, it shall be
tested in order to check that it has not been damaged during transport and
assembly to such an extent that its future operation will be at risk. Regarding
the performance of the test, refer to the testing method as per standards. The
results of the test shall be documented as detailed in Clause 3.2 "commissioning
checks -Transformers" and Clause 3.3 commissioning checks - Reactors.
3.1.1
APPLICATION OF VOLTAGE
If possible, the voltage should be increased step by step up to rated
voltage. This may be done by connecting the transformer/reactor to a generator
whose voltage is raised slowly. The higher the rated voltage of transformer/
reactor the more important it becomes that the application of the voltage is
done as described. If it is not possible to use a generator, the transformer/
reactor may be connected directly to a live line.
After the first application of voltage, the transformer/reactor shall be
checked carefully (gas relay, temperatures, leakages).
When the transformer/reactor has been is service for some weeks with
normal working temperature, all sealing joints shall be re-tightened.
3.1.2
ENERGISING
The initial magnetising current at the time of switching will be very
high. This depends on the particular moment in the cycle. The transformer
should always be soaked for few hours under constant care i.e. keep it
energized. If the breaker trips on differential, Buchholz or any other device,
the cause must be investigated before re-energising the transformer or reactor.
After successful charging, performance of the transformer/reactor , OTI, WTI
readings should be monitored for 24 hours and ensured that they are as per
loading.
3.1.3
ANALYSIS OF GAS
The gas conected in the relay will help to identify the nature of the fault.
It is suggested that the following checks are made at convenient intervals or
following the indication of accumulation of gas through alarm signal.
1. Rate of gas collection- The greater the rate of gas collection, the more
severe is the nature of the developing fault.
2. Colour of the gas helps in finding the affected material as follows.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
Colour
Identification
White
Gas of decomposed paper and cloth insulation.
Yellow
Gas of decomposed wood insulation.
Grey
Gas of overheated oil due to burning of iron portion
Black
Gas of decomposed oil due to electric arc.
3.
Combustibility of Gas- A small amount of gas drawn through the top
pet cock if brightens the test flame, then the gas is combustible.
Incombustible gas indicates air.
4.
Chemical Analysis of the Gas -The principles of working gas analyzing
equipment is illustrated in the figure 3.1.
Two solutions are prepared as detailed below and best results are obtained
with freshly prepared solution.
Solution 1: 5 gms of silver nitrate (AgNO3) dissolved in 100 ml
distilled water.
Solution 2:
A week solution of ammonia in water is slowly added to
100 ml of solution 1, until a white curdled precipitate
which forms first disappears in the mixture.
The gas analyser loaded with these solution is then connected to the
top pet cock. Small quantities of gas collected in the relay is allowed to pass
through the two solutions as illustrated.
The results are identified as follows:
1. Both solutions are clear
: Gas is air .
2. Solution 1 -White precipitate
turning brown on exposure to
sunlight
: Gas of oil decomposition.
3. Solution 2 -turning to
Dark brown precipitate
: Gas of decomposed paper,
cotton or wood insulation.
Note: THE ABOVE INFORMATION ON GAS ANALYSIS ARE AS
DETAILED IN IS:3638-1966. PLEASE REFER IS:3638-1966 FOR
ALTERNATIVE METHOD OF CHEMICAL ANALYSIS.
3.2
COMMISSIONING CHECKS -TRANSFORMER
3.2.0
SCOPE
This schedule covers the tests to be done at site after transformer has
been installed and dried out.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
3.2.1
GENERAL
Check the following:
Sl.No. Description
1.
2.
3.
4.
5.
6.
7.
8.
Breather Silicagel (Blue when dry)
Oil in the Breather housing cup.
All valves for their correct opening and closing sequence.
Oil level in conservator tank.
Oil in cooling system.
Oil level in bushings.
Release air, wherever necessary.
Cooling accessories (Pump motors, Fan motors etc.) for direction and O/L
setting.
Buchholz, oil level indicator, pressure gauges, thermometer,Temp. indicators
etc. for operation.
Earthing of main tank M.Box T/C driving gear, diverter, Pump Fan motor etc.
Neutral earthing.
Earth Resistance of Electrodes.
Earthing of bushing test tap.
Check oil leakage for 24 hrs.
Check Auxiliary circuit voltage (415 V).
Calibration of OTI/WTI with hot oil.
Check Working of WTI/RTD repeaters at control room.
IR of core to earth.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
3.2.2
INSULATION RESISTANCE TEST
Sl. Description
No.
1.
2.
3.
4.
Control wiring
Tap Changer
a) Motor
b) Control
Cooling system
a) Motor Fan
b) Motor pump
c) Control wiring
Main winding
a) HV/E+LV
b) IV/E+HV
c) LV/E+HV+IV
d) HV/IV
e) IV/LV
f) HV/LV
Date
Time
in Hrs
Megger
used
IR
Temp.
Value oC
Remarks
(Not less
than 500 V
megger)
(Not less
than 1000V
megger)
NOTE :
(1) While checking these values no external line, lightning arrestors etc. should
be in circuit.
(2) Special care should always be taken while meggering the transformer
winding to ensure that there is no leakage in the leads.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
3.2.3
OIL CHARACTERISTICS
Take necessary precaution (regarding rinsing the bottle, cleaning hand,
air bubble etc.) while withdrawing the samples (Please refer IS:6855). Each
sample should be free of air bubbles and should not be tested when it is hot
The sample should satisfy IS:1866.
Sl. Oil Sample
No. From
Time & Condition Moisture Break
Date Time Weather in PPM down
Voltage
in kV
Resisti Tan- Rem
vity at 90oC arks
at 90oC
(in ohm
-cm)
1. Tank
Top Sample
Bottom Sample
2. Cooling system
Top Sample
Bottom Sample
3. OLTC Diverter
(each phase)
3.2.4
1.
2.
3.
4.
3.2.5
TESTS ON CT
Ratio
Polarity
Magnetising current
IR value.
ON LOAD TAP CHANGER
Sl. Description
No.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
Date
Observation
Remarks
Visual Inspection of equipment.
Hand operation on all taps.
Complete wiring of the circuits.
Limit Switch
Over running device.
Remote Panel wiring.
Over load Device of Driving Motor.
Local Operation (Electrical).
Remote Operation (Electrical).
Tap Position Indicator.
Step by step contractor.
Out of Step Relay.
Note : While operating the mechanism on Electrical Control, check once again
limit switches, step by step contractor, over running device etc. for
their actual operation and ensure that they are functioning properly.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
3.2.6
OFF CIRCUIT TAP SWITCH
Tap switch handle should not be left halfway and/or unlocked.
3.2.7
CONTINUITY TEST
Continuity between line and neutral (for neutral end TC) or line to line
(for line end TC) with multimeter on all taps and phases to be confirmed.
3.2.8
Winding
MEASUREMENT OF WINDING RESISTANCE:
Tap No.
HV
1
Winding
2
Phase U
Phase V
Phase W
Temp
Remarks
3
4
5
6
7
8
9(a)
9(b)
9(c)
10
11
12
13
14
15
16
17
IV
Winding
LV
Winding
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
3.2.9
VOLTAGE RATIO TEST
Ratio on all taps is to be checked by hand operation only. This can be
done any time, once the tap changer is completely erected. Start the tap
changer from lowest tap and then go on increasing tap by tap while checking
the value instead of starting from normal tap.
Tap
Nos.
Voltage applied
Voltage Measured
Ratio obtained
Remarks
1.
2.
3.
4.
5.
6.
7.
8.
9. (a)
9. (b)
9. (c)
10.
11.
12.
13.
14.
15.
16.
17.
3.2.10
a)
Note:
Voltage Applied
Current measured
U-V
V-W
U-W
U phase
V phase
W phase
Volts
Volts
Volts
Remarks
m Amps
m Amps
m Amps
In case of single phase transformer, apply 230 V, 1 phase supply
between line terminal and earth.
b) Apply 3 phase 415 V on LV terminals and keep HV open.
u-v
v-w
u-w
Note:
MAGNETISATION CURRENT
Apply 3 phase 415 V on HV Terminals and keep LV open.
volts
volts
volts
u phase
v phase
w phase
m Amps
m Amps
m Amps
In case of single phase transformer apply 230 V, 1 phase between
line and earth terminal.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
3.2.11
VECTOR GROUP
Check the vector group of the transformer by connecting in a suitable
manner.
Vector
group
Diagram of
connection
Diagram as connected
for test
CONDITIONS TO BE PROVED
1.
2.
3.
Remarks
VOLTAGE MEASURED
1.
2.
3.
3.2.12
FINAL IR CHECKS
The megger readings finally after the transformer is connected to the
system
Date ......................... Time ........................Temp .......................
Windings
Megger
used
Value obtained in
Mega ohms
Remarks
HV/E+LV
IV/E+HV+LV
LV/E+HV+IV
HV/IV
IV/LV
HV/LV
3.2.13
OTHER TEST
WTI Setting
Alarm
Trip
Fan Start
Fan Stop
Pump Start
Pump Stop
Set for Proved
OTI Setting
Set for
Proved
Alarm
Trip
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
3.2.14
PROTECTION AND ALARMS
Prove the tripping of associated breakers by actual operation of the
various devices and relays.
UNDER NO CIRCUMSTANCES SHORTING OF ELECTRICAL
CONNECTIONS SHOULD BE DONE.
Sl.No. Device
1.
2.
Set for
Alarm
Trip
Proved
Alarm
Trip
Remarks
Buchholz
Excessive Winding
temperature
Excessive Oil Temp.
Oil flow failure
Water flow failure
Differential pressure
(OFWF cooling system)
Fan failure
Low oil level
(conservator tank)
Pressure relief valve
Differential relay
Over current relay
Earth fault (REF)
Instt. Earth fault
Inter trip, if any
Trip free check.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
3.2.15
a)
RECORD THE FOLLOWING AFTER CHARGING
No load current at relay terminal
U phase
A
V phase
A
CT Ratio
W phase
A
b) Temperature (at the time of charging)
o
O.T.I.
C
o
W.T.I.
C
o
C
Ambient
c)
Maximum temperature after 24 hours.
C
o
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
3.3
COMMISSIONING CHECKS REACTOR
Customer
W.O. No.
Site
Sl.No.
Rating
Voltage class
Scope
This schedule covers the tests to be done at site after reactor has been
installed and dried out.
3.3.1
GENERAL
Check the following :
Sl.No.
Description
1.
2.
3.
4.
5.
6.
7.
8.
Breather Silicagel (Blue When Dry)
Oil in the Breather Cup.
All valves for their correct opening and closing sequence.
Oil level in conservator tank.
Oil in cooling system.
Oil level in bushings.
Release air, wherever necessary.
Buchholz, oil level indicator, thermometer, temp. indicators etc.
for operation.
Earthing of main tank, M. Box.
Neutral earthing.
Earth Resistance of Electrodes.
Earthing of bushing test tap.
Check oil leakage for 24 hours.
Check auxiliary circuit voltage (415 V).
Calibration of OTI/WTI with hot oil.
Check Working of WTI/RTD repeaters at control room.
IR of core to earth.,
9.
10.
11.
12.
13.
14.
15.
16.
17.
3.3.2
INSULATION RESISTANCE TEST
Sl. Description
No.
1.
2.
a)
Remarks
Control Wiring
Main Winding
HV/E
Date
Time
in hrs.
Megger
used
IR
Value
Temp.
Remarks
500 V
>1000V
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
Note:
(i)
While checking these values no external lines, lightning arresstors
etc. should be in circuit.
Special care should always be taken while meggering the reactor
winding to ensure that there is no leakage in the leads.
(ii)
3.3.3
OIL CHARACTERISTICS
Take necessary precaution (regarding rinsing the bottle, cleaning hand,
air bubble etc.) while-withdrawing the samples. Each sample should be free of
air bubbles and should be tested when it is hot. The sample should satisfy
IS:1866.
SI. Oil Sample
No. From
1.
2.
Time & Condition
Moisture
Date Time Weather in PPM
Break
Resisti
Tandown
vity at
at
Voltage 90oC
90oC
in kV
(in ohmcm)
Rem
arks
Tank
Top Sample
Bottom Sample
Cooling system
Top Sample
Bottom Sample
3.3.4
1.
2.
3.
4.
3.3.5
TESTS ON CT
Ratio
Polarity
Magnetising current
IR value
MEASUREMENT OF WINDING RESISTANCE
Phase U Phase V
Phase W
Temp.
Remarks
Winding
3.3.6
a)
CURRENT MEASUREMENT
Apply 3 phase 415 volts on HV Terminals.
Voltage Applied
Current measured
U-V
Volts
U Phase
mA
V-W
Volts
V Phase
mA
W-U
Volts
W Phase
mA
Remarks
Note: In case of single phase reactors apply 230 V, 1 phase between
line terminal and earth.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
3.3.7
FINAL CHECKS
The megger readings finally after the reactor is connected to the system.
Date
Winding
Time
Megger used
Temperature
Value Obtained
in megaohms
Remarks
HV/E
3.3.8
OTHER TEST
WTI Setting
Set for
Proved
OTI Setting
Set for
Proved
Alarm
Trip
3.3.9
PROTECTION AND ALARMS
Prove the tripping of associated breakers by actual operation of the
various devices and relays.
Note: Under no circumstances shorting of electrical connections be done.
Sl.No. Device
1.
2.
Set for
Alarm
Trip
Proved
Alarm
Trip
Remarks
Buchholz
Excessive Winding
Temperature
Excessive Oil Temp.
Oil Level
(Low & Max.)
Pressure Relief Valve.
3.
4.
5.
3.3.10
RECORD THE FOLLOWING AFTER CHARGING
a) No load current at relay terminal
U phase
mA
V phase
mA
W phase
mA
CT Ratio
b) Temperature (at the time of charging)
o
O.T.I.
C
o
W.T.I.
C
o
Ambient
C
c)
Maximum temperature
after 24 hours.
C
o
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
¦ÉÉMÉ-4
+xÉÖ®úIÉhÉ B´ÉÆ {ÉÊ®úSÉɱÉxÉ
SECTION-4
MAINTENANCE AND OPERATION
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
SECTION 4
4.
MAINTENANCE AND OPERATION
4.1
SUPERVISION OF TRANSFORMER/REACTOR
4.1.1
GENERAL
In order to avoid faults and disturbances, it is important that a careful
and regular supervision and control of the reactor and its components is planned
and carried out.
The frequency and extent of such a supervision and control is dependent
on climate, environment and service conditions etc.
The directions for a certain transformer/reactor are therefore preferably
based on experiences from comparable transformer/ reactor installations.
A supervision and maintenance program according to schedule in
ANNEXURE 4.1 is recommended.
Spare transformers/reactors are supervised and maintained according
to the same schedule as transformers/ reactors in service.
4.1.2
GENERAL MAINTENANCE
Dirt/Dust
The external transformer surfaces shall be inspected regularly and when
required cleaned from dust, insects, leaves and other airborne dirt.
Possible Leakage
After energising of the transformer, a certain settling may appear in
sealing joints. These should therefore be retightened according to schedule in
ANNEXURE 4.1. This applies especially to sealing joints with plain gaskets
that are not placed in grooves.
Rust damages, touch-up painting
A regular inspection of the external surface treatment of the reactor
should be carried out. Possible rust damages are removed and the surface
treatment restored to original state by means of primer and finish paints.
4.1.3
OIL PRESERVATION SYSTEM, MOISTURE ABSORPTION
Transformer oil absorbs easily moisture from the surrounding air. The
moisture absorption has been prevented by means of rubber sack in
convservator which acts as a separating wall between the oil and the
surrounding air.
The moisture absorption is further prevented by a breather connected
to the conservator. The active drying agent (silica gel) should be exchanged or
regenerated when 2/3 of the agent has been red-coloured by absorbed moisture.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
The breather contains also an oil-seal that prevents spontaneous air
circulation. This seal should be filled with oil to the level specified.
4.1.3.1 OIL LEVEL INDICATOR FOR OIL CONSERVATOR
The Transformer oil conservator is provided with an oil-level indicator.
At an oil temperature of 45oC, the conservator should be half filled. If the level
exceeds the value “full”, oil must be drained off. If the value is “low”, oil must
be filled in, Normal oil level should be at 35oC mark.
4.1.3.2 GAS-OPERATED RELAY (BUCHHOLZ RELAY)
The use of gas-operated relay as protection for oil-immersed transformers
is based on the fact that faults as flash over, short-circuit and local overheating
normally result in gas- generation. The gas- bubbles gathering in the gasoperated relay affect a float- controlled contact which gives an alarm signal.
4.1.3.3 MOISTURE
If the oil has been subjected to moist air, the moisture content and the
electric strength of the oil shall be checked.
4.1.3.4 SLUDGE, ACID
Normally the BHEL transformers have uninhibitated oil.
Sometimes inhibited oil is used. The inhibitor works so that it breaks the
chain reaction by which sludge and acid are produced. This retards the ageing
process and extends the utilization time of the oil.
If sludge is being produced in the oil, the oil changes colour and becomes
darker and turbid. The sludge can be removed by means of filtering, but if the
sludge formation has started, it will increase with time. The oil should therefore
be exchanged if the neutralisation value according to IS:1866 exceeds 0.5 mg
KOH/g or precipitable soluble sludge is produced.
The oil exchange should preferably be carried out when the transformer
is warm and the oil viscosity is low.
The exchange should be as complete as possible, because old oil will
affect the new one, speeding up the ageing.
Oil which is not too much oxidized may in certain cases be regenerated,
but this is economical only for large oil quantities.
4.1.3.5 OIL, MISCELLANEOUS
For supplementary information about transformer oil, see clause 4.2
“Supervision and control of oil”.
4.1.4
TEMPERATURE SUPERVISION
The service life of a transformer is highly dependent on the temperature
prevailing in the core and windings under operation. It is thus important to
keep the oil and winding temperatures under observation continuously. The
temperatures should be read regularly and the measured values registered.
These values will give guidance for judging the service life of the
transformer, cooling system functions etc.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
4.1.4.1 OVERLOAD
A Transformer can normally be overloaded at a low ambient temperature.
However, the permissible overload must not be judged only with regard to the
oil temperature. We must also consider that the temperature difference between
winding and oil will increase with the load. Therefore, also the winding
temperature must be supervised during overloading.
For determination of the overload capacity for modern transformers refer
IS:6600.
If the temperature in a transformer shows a tendency of rising without
a corresponding increase of the load, this may be caused by a reduction of the
cooling ability of the cooling equipment (dirt, dust). The thermometer should
also be checked in this case.
4.1.4.2 THERMOMETER FOR MEASUREMENT OF TOP-OIL TEMPERATURE
The thermometer consists of a cylindrical sensing body with a flange, a
capillary tube, and a thermometer housing with dial and contact-device. The
measuring system is filled with a liquid, which changes its volume at
temperature variations, and affects spring bellows. The movements of the
bellows are transferred to the pointer and signal contacts via a link system.
The thermometer is provided with two signal contacts of mercury switches.
The contacts can be set independently of each other.
For control and adjustment of the thermometer, see OTI leaflet.
4.1.4.3 WINDING-TEMPERATURE INDICATOR
The thermometer system consists of a sensitive body with assembling
details, a capillary tube and a thermometer housing, which contains a scale
with an indicating pointer and a max. pointer, heating and adjusting resistor,
as well as contact- device for four switches.
For further information about function, control and adjustment of winding
temperature indicator, see WTI Leaflet.
4.1.4.4 REMOTE CONTROL OF WINDING TEMPERATURE
For remote control of winding temperature a resistance temperature
device has been used with a heating element built into the same housing. The
heating element is fed by the secondary current of a current transformer.
For setting of the heating element there is a parallel connected adjusted
resistor installed in the control cabinet.
For further information about function and calibration, see RTD Leaflet.
4.1.4.5 RADIATORS
The external cooling surfaces shall be inspected regularly and when
required cleaned from dust, insects, leaves or other airborne dirt. This is
especially important in case of fan cooling. The cleaning is suitably carried out
by means of water flushing at high pressure.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
Normally, no measures are necessary for keeping the internal cooling
surfaces clean as long as the oil is in good condition. If, however, sludge
formation has set in, the sludge may deposit on horizontal surfaces in radiators.
In such a case, the radiator should be flushed internally with clean oil.
If the sludge does not loosen, we can firstly flush with petrol etc. and
then with oil.
4.1.4.6 CONTROL CABINET
The operation of the control cabinet and devices normally included, are
described in Vol. I.
4.1.4.7 BUSHINGS
Bushing porcelains shall be cleaned from dust and dirt regularly. In areas
where the air contains impurities as salt, cement dust, smoke or chemical
substances, shorter intervals are required. See also the Instructions in the
special information documents about bushings that are included in vol.I.
4.1.4.8 CONNECTIONS
In order to avoid prohibited temperature rises in the electrical connections
of the transformers/reactor, all screw-joints should be checked and re-tightened
according to schedule enclosed.
4.1.4.9 ACCESSORIES
Separate leaflet/instructions should be followed for various fittings (as
applicable) for Fans, Pumps, Flow indicators, Pressure Gauges, Oil Gauge,
Pressure reducing valve, OLTC, Off circuit tap switch, OFAF/OFWF Coolers
etc.
These leaflet are enclosed with Vol I.
4.1.5
MAINTENANCE SCHEDULE
Maintenance schedule given at Annexure 4.1 should be followed. With
proper maintenance as per this schedule normal life of Transformer or reactor
can be expected.
4.1.6
IR TEMPERATURE RELATION
It has always been the question from our customers as to how the IR
value can be converted at different temperatures. We have drawn a curve
(Fig. 4.1) for guidance of the operating staff on the basis of our experience.
So that they can judge the IR Value at any temperature. This curve cannot be
taken for absolute value but will serve as a good guide for conversions of IR
values at different temperatures. A simple example is given as to how to
calculate the value at different temperature.
Suppose IR value of 70oC is 300 M Ohms and we want to convert at
o
40 C, the curve will give you a factor K for difference in temperature i.e.
(70oC-40oC)=30oC.
K for 30oC temperature difference = 4.2
So the value at 40oC = 4.2x300 = 1260 M. Ohms.
Value thus converted fairly tally with the actual
Value when cooling the transformer. The factors are tabulated as below:
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
Difference
in temp.
Factor K
4.2
10oC
1.65
20oC
2.6
30oC
4.2
40oC
6.6
50oC
10.5
SUPERVISION AND CONTROL OF OIL
4.2.1
GENERAL
The oil in a reactor provides an electrically insulating and a cooling
medium. The service reliability of an oil-immersed transformer/reactor is
therefore mainly, depending on the oil quality.
In service, oil is subjected or normal deterioration due to the conditions
of use mainly due to air, water and solid particles/sediment.
4.2.2
SCHEDULE
The oil should be maintained as per the guidelines of IS:1866. Periodicity
of test and permissible limits for important parameters of oil - electric strength,
water content, resistivity, tan-delta, neutralization value, sediment and
precipitable sludge, flash point and interfacial tension are given in Annexure
4.2. Health of reactors can be effectively monitored by Dissolved Gas Analysis
(DGA) technique described in detail in IS:9434 and IS:10593. This technique
helps in detection of incipient faults in reactors.
4.3
TROUBLE SHOOTING
General measures for trouble shooting are described in this section.
4.3.1
Items to be informed to BHEL in case of trouble.
Followings are items to be informed to BHEL.
1. Transformer or Reactor specifications
Capacity
Serial number & work order No.
Year of manufacture.
2. Load current (A) or load (kW)
3. Operating tap position (In case of Transformer)
4. Conditions at time of trouble.
a)
Date, time
b) Trouble phenomena
c)
Checked items and results
4.3.2
Transformer troubles and check items. Troubles, their possible causes
and items to be checked are given in Table 4.1 & 4.2.
4.3.3
Detective devices and their functions. Refer to table 4.3
4.3.4
Check items and judging standard Refer to table 4.4.
4.3.5
Detection method of oil or gas leaks. Refer to table 4.5.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
Table 4.3: Detective devices and their functions
No. Detective
device
Description
1.
Buchholz
relay
(1st stage)
This relay detects the gas evolution due to internal trouble and
gives alarm, and is suited to the detection of minor or slowly
developing faults. The nature of the detected fault can be judged
to an extent by analyzing the gas and oil. In case of nitrogen gas
sealed transformer, part of dissolved nitrogen gas comes out due
to the sudden temperature drop, which sometimes results in the
actuation of this relay.
2.
Buchholz
relay
(2nd stage)
When a major fault suddenly takes place inside the transformer,
oil flows suddenly from the transformer tank to the conservator.
The second stage of Buchholz relay is actuated by this oil flow. If
the second stage of the relay functions independently, check the
air breather, nitrogen gas sealing device etc. If it functions
combinedly with the over current relay etc. it is suspected that a
serious internal defect is existent. In such a case take all tentative
measures and contact BHEL immediately.
3.
Pressure
relief device
When the internal pressure of the transformer rises above the set
value, the pressure relief device functions. It also functions, though
occasionally by the choking of the air breather. The self- excited
pressure relief plate is subject to brittleness caused by secular
change. Comprehensive judgment based on the inspection of other
protective relays is the key to determining whether the function of
this device is an erroneous operation or a normal operation caused
by internal defect.
4.
Differential
relay
This relay detects the internal defect by comparing the input current
and the output current of the transformer. If it functions combinedly
with other protective devices, it is indicative, in almost all cases,
of an internal fault. Note that this relay sometimes operates due to
inrush current when the transformer is energized, and this is of
course not an internal fault.
5.
Dial thermo
meter alarm
contact
This thermometer gives alarm when the temperature rises beyond
the preset value. Insufficient cooling effect of cooling equipment
due to contamination of cooling fins, Stoppage of oil pumps, fans
and so forth is one of the reasons that operates this device.
6.
Overcurrent
relay, ground
fault relay
These are intended for detecting faults in the electric system
connected with the transformer. A fault in the transformer results
in the function of these relays, which is always accompanied by
the actuation of protective devices of the transformer. Detection
of the fault in the electric system should therefore be made on the
basis of a comprehensive judgment of these functions.
7.
Voltmeter
ammeter
If a sudden change in voltage or current is noted when no
abnormalities are detected in the electric system, or an abnormal
unbalance of voltage or current is noted between phases, investigate
the cause.
8.
Human
senses
Note that human senses also play an important role in fault
detection. Following are the points to be checked by your senses.
1) Discolouration or odour of insulation oil (blackening or stink). If
pieces of insulating materials or copper particles are found in
the oil, it is suspected that an internal defect has developed.
2) Abnormal vibration or sound.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
Table 4.4: Check and refer standards
No. Check Point
Description
Judging standard
1.
Measurement
of insulation
resistance
Grounding fault can be detected by
this measurement, though to some
extent. The measurement must be
proceeded after disconnecting the
transformer from lines and cleaning
of bushing surfaces.
Judgment to be
made by comparison
with values obtained
by periodical
inspection.
2.
Measurement
of winding
resistance
This is a primary means to be
employed for detecting the fault of
windings. The resistance should
preferably be measured independently
by the D.C. drop of potential method.
Judgment to be made
by comparison with
the factory test report.
3.
Measurement
of voltage ratio
This can be conducted by applying a
voltage of about 200V which can be
readily obtained at job-site. Accurate
measurement at job site entails some
difficulties due to source voltage
variation and errors of instruments.
In case of 3 phase transformers, it is
essential to measure the ratio phase
by phase and check the variation of
the ratio between phases.
Judgment to be made
by comparison with
the factory test report.
This measurement is very useful to
detect fault in windings and/or cores.
Local short- circuit in windings or
cores often causes an increase in the
exciting current. The test can be made
by applying a low voltage (200-400
volts) to a winding.
1
Measure dielectric strength and check
for carbon sludge, offensive odour
and discoloration.
Judgment to be made
with reference to
Annexure 4.1 & 4.2.
4.
Measurement
of exciting
current
2
Comparison of
the measured
values with
previously
obtained ones.
Significant
difference in
value among
phases.
5.
Checking of
insulation oil
6.
Measurement
of dielectric
loss factor,
tan
7.
Analysis of gas
accumulated in
Buchholz relay
When gas is accumulated in the
Buchholz relay,its composition must
be clarified by the gas chromatograph
analyzer to check for the possible
internal defect.
Contact BHEL
8.
Analysis of
dissolved gas
in oil
Existence of internal defect can be
judged, though to a limited degree,
by sampling and analyzing oil by a
gas chromatograph. (Refer 4.3.2).
Contact BHEL
Judgment to be made
by comparison with
values obtained by
periodical inspection.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
Table 4.5 Method for detecting oil or nitrogen leaks
Leak
Measures
Description
Oil leak
Clean the suspected leak
part with thinner or gasoline
apply chalk powder to it.
The leak part will present
itself as a soiled spot.
The following are susceptible
to leakage.
(1) Gasketed joints.
(2) Welded parts.
Nitrogen leak
(in case of
Nitrogen sealed
system)
Step up Nitrogen gas pressure
to 0.17 kg/cm2
The following are susceptible
to leakage
(1) Accessories for pressure
relief
(2) Flanges
(3) Welded parts
4.3.6
GAS ANALYSIS ON TRANSFORMER OIL
Incipient faults in oil filled transformer are usually the result of electrical
or thermal excess stress of either the transformer oil or insulating materials.
It is known that such excessive stresses produce a mixture of gases
characteristic of which give an indication of the type of faults, and materials
associated with the faults.
It is recommended that analysis of dissolved gases in transformer oil by
gas chromatographic equipment is made, the time of commissioning and then
after an interval of one year for transformers of 145 kV class and above.
4.3.7
ANALYSIS METHOD
4.3.7.1 SAMPLING OF OIL FROM TRANSFORMERS
Oil in transformers can be sampled through drain or sampling valve near
bottom of the tank. Special care shall be taken not to introduce air, foreign
matter, or dirty oil into sampling container. For this purpose, first 0.5-1.0 litre
of oil from the transformer shall be over-flown through the oil container. Shape
of the sampling container may be that of shown in Fig. 4.2 and sampling
method shall be in accordance with Fig. 4.3. See also IS:9497 Sampled oil
shall not be exposed to air before analysis.
4.3.7.2 GAS ANALYSIS
Gases to be analysed and criteria for the gases found in transformer oil
are tabulated in table 4.6.
4.3.8
ASSESING THE TEST RESULTS
Test results on gas contents in oil by some typical faults in transformer
active part models are shown in table 4.7.
Table 4.6 and table 4.7 may by referred to evaluate transformer condition.
To analyse DGA test results, flow chart given at Appendix A of IS:10593
should be followed. Standard values may be taken from CBIP Technical report
no. 62 of April 88 titled "Guide for testing of Transformer by Sampling and
analysis of free and dissolved gases" Ratio technique of IS:10593 should be
used to know the nature of fault. IS:9434 and IS:10593 have been adopted
from IEC pub 567 and IEC pub 599.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
Table 4.6 Gases to be analysed and criteria
1. Gases to be analysed normally
O2, N2, H2, Co, Co2, CH4
2. Gases to estimate abnormality
H2, CH4, C2H2, C2H4, C2H6
3. Gases to estimate deterioration
Co, Co2, CH4
Table 4.7 Gas content in oil by faults
Sl.
Type of faults
Decomposable gases in
transformer oil
1. Overheat of oil
CH4, C2H4, H2, (C2H6, C2H2,C3H6 C3H8)
2. Arcing in oil
H2, C2H2, (CH4, C2H4)
3. Overheat of solid insulating materials
CO, CO2, (H2, C2H4)
4. Overheat of oil and paper combination CH4, C2H4, CO, CO2, H2
5. Arcing of oil and paper combination
(
4.4
(i)
H2, C2H2, CO, CO2, (C2H4)
) shows gas contents which appear rarely.
PARALLEL OPERATION
If it is desired to parallel a transformer which is not identical in
design with BHEL transformer, it is preferable to refer the matter to
BHEL for advice.
(ii) The voltage ratings/ratios and impedance values at all taps should
match for the two transformers that are to be paralleled. Only certain
combinations of vector groups are capable of being paralleled. The
table 4.8 below indicates the more common permissible combinations.
Table 4.8
TRANSFORMER (B)
H.V.
Delta
Star
Delta
Star
L.V.
Star
Delta
Delta
Star
Yes
Yes
No
No
Yes
Yes
No
No
No
No
Yes
Yes
No
No
Yes
Yes
H.V./L.V.
Delta/Star
TRANSFORMER (A) Star/Delta
Delta/Delta
Star/Star
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
(iii) Reference to the connection diagrams of two transformers should
indicate the terminals to be paralleled.
(iv) The reversal of two leads on either side of a three-phase transformer
will reverse the polarity changing them in sequence (e.g. form UVW
to VWU or WUV) will swing the vectors through 120.
(v) Phase sequence and polarity can be checked by energising both
transformers on the primary side before paralleling and measuring
the open-circuit voltage appearing across each pair of terminals which
will ultimately be paralleled.
(vi) IS:2026 and IS:10561 may also be referred.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
ANNEXURE 4.1
MAINTENANCE SCHEDULE
SI Items to be
inspected
Inspection notes
HOURLY
1.
2.
3.
4.
Ambient
temperature
Winding
temperature
Oil temperature
Load amps/Load
voltage
-
-
Check that temperature
rise is reasonable.
Shutdown the transformer and
investigate, if either is persistently
higher than normal.
Check against rated figures
An improper tap position can
cause excessive core loss. Voltage
and tap position should be
corrected.
DAILY
1.
2.
3.
4.
Oil level in
transformer
conservator
Oil level in tap
changer diverter
switch.
Oil level in
bushings.
Check oil level from oil
gauge
Top up, if found low.
Check oil level from the
gauge glass.
Top up, if found low.
Check the oil level from
gauge glass/gauge.
Top up, if found low.
Pipework and
accessories for
leakages
Inspect the transformer for
leakages.
If leakages are observed tighten
evenly the gasket joints. Replace
‘O’ ring or washer suitably.
Replace gasket if needed.
MONTHLY
1.
2.
Buchholz Relay
Dehydrating
breather
Leakages of
water into
cooler.
Check oil level
Check colour of silicagel.
1.
Bushings
2.
Transformer oil
and tap changer
oil
Cooler fan,
bearing and
controls,
pumps.
Examine for dirt deposition
and tightness of oil filling
plugs. Examine for cracks
in porcelain.Clean and
tighten plugs.
Check for di-electric
strength and moisture
content.
Check contacts, manual
control and interlocks.
3.
3.
Action required
-
Release collected gas/air
Reactivate/replace with new
charge, if found pink Investigate
and rectify after taking shutdown.
QUARTERLY
Cracked porcelain should be
rectified/replaced.
Take suitable action to restore
quality of oil.
Lubricate the fan bearings.
Replace worn out contacts and
other parts. Clean/ adjust controls
and interlocks.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
4.
On load tap
changer
Examine contacts, check
step by step mechanism
operation, end position
limit switches and brakes.
Also check oil in driving
gear mechanism.
Replace all worn out and burnt
contacts. Set limit switches in
position. Clean/ replace brake shoe
lining. Lubricate all bearing and
coupling points suitably. (Refer
Separate leaflet.)
5.
Dehydrating
breather
Check oil level in the cup
and ensure air passages
are free.
Top up, if found low. Clean air
passages.
YEARLY
1.
Transformer oil
Check for characteristics in
line with IS:1866
Filter/replace as required to restore
the quality.
2.
Cable box
Check for proper scaling of
compound filling holes.
Check for cracks in the
compound (if used).
Replace sealing washer, if found
damaged.
3.
Alarm and
protection
circuits.
Check all protections and
alarm circuits by actual
external initiation. Check
operation of relays and
their sensitivity.
Replace burnt out fuses Adjust the
setting and check wiring circuits.
Adjust relay setting, if needed.
Replace damaged relays.
4.
OTI & WTI
pockets
Check oil in the WTI and
OTI pockets.
Replenish, if required
5.
Earth strip
Check earthing resistance
6.
Packing gaskets
of fans
Inspect the condition of
packing gaskets.
Take suitable action, if resistance
is noted high.
Replace if worn out or resilience
lost.
7.
Fan motors
Check IR value of motor
winding after rainy season.
Noise & vibration of fans.
Dry out, if found low, check
balancing of fans.
8.
Tank and
accessories
Check painting and surface
finish.
Mechanical
inspection
of
all
accessories.
Touch up/repaint, if required
Replace any component found
damaged.
9.
Gasket joints
10. Divert servicing
11. Diverter switch
of on-load tap
changer
Check the tightness of
bolts
One
year
commissioning
after
Check the contacts for
burning or pitting marks.
Tighten evenly all loose bolts,
nuts, locking etc.
Draw out diverter, clean, tighten
contacts.
Recondition/replace if required.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
12. Diverter switch
oil
Filter oil irrespective of
strength.
Replenish with new oil,if oil is too
much contaminated.
13. Tank cover and
conservator
Dirt, Dust, Surface
Clean touch-up painting.
14. Bushing top
connectors.
Check contact joints
Retighten.
1.
Oil conservator
General
Inspection
including checking the
operation of gauges on it.
Check heathiness of air
cell.
Clean, if required. Ensure proper
functioning of indicator/Replace if
punctured.
2.
Transformer oil
Examine values as per
IS:1866
Filter oil if required.
3.
Buchholz relay
Mechanical inspection of
buchholz
Set floats, if required.
TWO YEARLY
7-10 YEARLY
1.
Transformer and
tap changer
Assembly
Overall internal inspection
including lifting of core and
coil assembly
Tighten all clamping arrangement,
loose cleatings etc. Tighten all
nuts and bolts and check locking
arrangements and fasteners.
Wash core and coil with dry
transformer oil.
NOTES:
1. In addition to the above instructions, reference should be made to
IS:10028 “Code of practice for selection installation and maintenance
of transformer’’
2. Reference of IS:1866 "Code of practice for Maintenance and
Supervision of Mineral insulating oil in equipments'' should be made
for maintenance of oil while transformer is in service. Table 1&2 of
IS:1866 are given at annexure 4.2 & 4.3 for ready reference.
3. The inspection schedule specified for longer periods automatically
includes those specified for shorter period.
4. All maintenance test results and observations should be specifically
recorded.
5. Where matter given in the inspection book differs from that given in
standards referred to, the transformer user should follow the instruction
book.
6. In case of anything abnormal occuring during service, advice from
BHEL should be obtained giving them complete particulars as to the
nature and extent of occurrence, together with the name plate
particulars in order to assist identification of the transformer.
7. As efforts are being constantly made to improve designs and service,
the transformer supplied may differ in minor details from data given
herein.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
ANNEXURE 4.2
APPLICATION AND INTERPRETATION OF TESTS ON OIL IN TRANSFORMERS AND
REACTORS (INCLUDING SELECTOR TANKS OF ON-LOAD TAP CHANGERS
(CLAUSE 5.1 (a), 5.2, 6.0 and 7.1)
Sl.No
CHARACTERISTIC
(1)
(2)
(i)
Electric strength
(breakdown
voltage-kV)
EQUIPMENT
VOLTAGE
TEST METHOD
(REF TO IEC/ISO
TEST VENUE
F=FIELD
OR APPENDIX)
L=LABORATARY
SUGGESTED
INITIAL
PERIODICITY
OF TESTS
(3)
(4)
(5)
145 kV and
above
IS:6792-1972*
(average of 6
brealdowns
on one cell filling
with 2.5 mm gap
spacing)
F/L
72 kV and
less than
145 kV
Below 72.5 kV
(ii)
water content
(ppm)
145 kV and
above
PERMISSIBLE
LIMIT
SATISFACTORY
FOR USE
ACTION IF
OUTSIDE
PERMISSIBILE
LIMIT SEE ALSO
(6)
(7)
(8)
After filling
or re-filling
prior to
energizing,
then after
three months
and after one year
50 kV
(Min)
Recondition
or alternatively
If more econmic
or other tests
dictate, replace
oil.
40 kV
(Min)
30 kV
(Min)
IS:335-1983
L
After filling
25 PPM
or re-filling
(Max)
prior to
energizing,
35 PPM
3 months
and after one year
Recondition oil
or alternatively
If more econmic
or other tests
dictate, replace
oil.
Below 145 kV
(iii)
Specific resistance
(resistivity
ohm-cm) at
900C (see Note 9)
All voltages
IS:6103-1971
L
After filling
or re-filling
prior to
energizing,
3 months
and after 2 years
0.1X1012
ohm-cm
(Min) at
900C
Recondition if
the value of the
DDF permits,
reclaim or replace
if not.
(iv)
Dielectric dissipation
factor (tan δ)
at 900C
145 kV and
above
Below 145 kV
IS:6262-1971
L
After filling
or re-filling
prior to
energizing, then
after 2 years
0.2 (Max)
Reclaim or
replace oil (limit
to be adopted
depends on the
type of equipment
and instructions
from the
manufacturer).
(v)
Neutralisation
value (total
acidity (see
Note 10)
All voltage
IS:1448 (P:2)
1967
F
or
L
do
0.5 mg
KOH/g
(Max)
Reclaim or replace
oil
(vi)
Sediment and/
or precipitable
sludge
All voltage
Appendix A
L
do
No sediment
or precipltable
sludge should
Recondition oil
if sediment is
detected
be detectable
1.0 (Max)
alternatively
if more economic
or other test
dictate replace
oil. Reclaim or
replace oil if
precipitable
sludge is
detected.
(vii)
Flash point
(see Note 11)
All voltage
IS:1448 (P:21)
1970
L
do
Decrease in
the flash point
15oC (Max) of
the inital value
minimum value
125oC
Reclaim or
replace oil after
knowing causes.
(viii)
Interfacial
tension
at 27oC
All voltage
IS:6104-1971
L
do
0.018 N./m
(Min)
Reclaim or
replace oil.
(ix)
Dissolved gas
analysis
145 kV and
above
IS:9434-1979
L
After filling
or re-filling
prior to
energizing,
3 months and
after one year.
IS:10593
1983
Reclaim or
replace oil.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
Note 1
Note 2
The voltages indicated in col 3 are highest system voltages.
The full application of these recommendations to small transformers
upto 1 MVA or below 36 kV will be technically necessary only in
cases where high reliability is required. It will normally be uneconomic.
In most cases, it could be limited to the simpler field tests and the
periodicity of tests will be determined with relation to the reliability
required. Inspection of oil in pole- mounted transformers is assumed
to be uneconomic.
Note 3 Characteristics are normally well above the permissible limits given
in col 7 at the time of test of transformer in the manufacturer’s
works. However, no separate limits have been fixed for this stage.
Note 4 Higher limits may be required for electric strength and lower limits
for water content prior to testing in the factory and prior to energizing
the transformer. Special instructions given by the manufacturer may
be followed.
Note 5 Suggested initial periodicity of tests have been given in col. 6.
Subsequent intervals may vary depending on previous test results
(progress of ageing) and on changed service conditions.
Note 6 Instructions of equipment manufacturers should be taken into account
in adoption of the recommendation of this table.
Note 7 For application and interpretation of test in diverter tanks of on-load
tap changers, guidance shall be taken from the manufacturer.
Note 8 Alternatively an indication of the presence and effect of water content
can be obtained from a resistivity comparison at 27oC and 90oC (see
6.4.1.2).
Note 9 Water content and acidity influence the values of the specific
resistance. The limit is indicative only and when value falls below
this limit the cause should be ascertained by other tests.
Note 10 Perform test more frequently when value exceeds 0.3 mg KOH/g.
For transformers subject to test (ii), method(s) it will be necessary
to test more frequently to establish when neutralization value (total
acidity) exceeds 0.1 mg KOH/g.
Note 11 This test may also be required when an unusual odour is noted or
when an internal fault has occured.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
ANNEXURE 4.3
GUIDELINES FOR THE CHARACTERISTICS OF OIL TO BE OBTAINED BEFORE
ENERGIZING NEW TRANSFORMERS USING NEW INSULATING OILS ACCORDING
TO IS:335-1983
SL.
NO.
CHARACTERISTIC
EQUIPMENT
VOLTAGE
TEST METHOD
(REF TO IS:OR
APPENDIX)
PERMISSIBLE
LIMIT
SATISFACTORY
FOR USE
(1)
(1)
(2)
Electric strength
(breakdown
voltage kV)
(3)
(4)
Below 72.5 kV
(5)
IS:6792-1972
40 kV (rms) min
72.5 kV and less
than 145 kV
50 kv (rms) min
145 kV
above
60 kV (rms) min
and
(ii)
Specific
resistance
(resistivity ohmcm at 90oC)
All voltages
IS:6103-1971
1X10 12
(min)
(iii)
Dielectric
dissipation
factor (tanδ) at
90oC Max.
All voltages
IS:6262-1971
0.05
(iv)
Water content,
ppm Max.
Below 72.5 kV
IS:335-1983
25 ppm
72.5 kV and less
than 72.5 kV
20 ppm
145 kV
above
15 ppm
(v)
Interfacial
tension at 27oC
(Min) N/m
All voltages
(vi)
Dissolved gas
content
145 kV
above
and
IS:6104-1971
and
ohm-cm
0.030
(Under
Consideration)
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
4.5
DO’S AND DON’TS
4.5.1
DON’TS FOR POWER TRANSFORMER/REACTOR
1.
Do not energise without thorough investigation of the transformer/reactor, whenever
any alarm of protection has operated.
2.
Do not re-energise the transformer/reactor, unless the Buchholz gas is analysed.
3.
Do not re-energise the transformer/reactor without conducting all pre-commissioning
checks. The results must be comparable with results at works.
4.
Do not handle the off-circuit tap switch when the transformer is energised.
5.
Do not energise the transformer, unless the off-circuit tap switch handle is in
locked position.
6.
Do not leave-off circuit tap switch handle unlocked.
7.
Do not leave tertiary terminals unprotected outside the tank, connect them to
tertiary lightning arrestors protection scheme, when connected to load.
8.
Do not allow WTI/OTI temperature to exceed 55oC during dryout of transformer,
and filter machine temperature beyond 60oC.
9.
Do not parallel transformers which do not fulfil the condition given in clause 4.4.
10. Do not use low capacity lifting jacks on transformer/reactor for jacking.
11. Do not move the transformer/reactor with bushings mounted.
12. Do not overload the transformer other than the specified limits as per IS:6600.
13. Do not change the settings of WTI and OTI alarm and trip frequently. The setting
should be done as per the site condition.
14. Do not leave red pointer behind the black pointer in OTI and WTI.
15. Do not leave any connection loose.
16. Do not meddle with the protection circuits.
17. Do not allow conservator oil level to fall below 1/4 level.
18. Do not allow oil level to fall in the bushings, they must immediately to be topped
up.
19. Do not leave marshalling box doors open, they must be locked.
20. Do not switch off the heater in marshalling box except to be periodically cleaned.
21. Do not allow dirt and deposits on bushings, they should be periodically cleaned.
22. Do not allow unauthorised entry near the transformer/reactor.
23. Do not leave ladder unlocked, when the transformer/reactor is ‘ON’ in service, in
case it is provided.
24. Do not change the sequence of valve opening for taking standby pump and motor
into circuit.
25. Do not switch on water pump unless oil pump is switched on.
26. Do not allow water pressure more than oil pressure in differential pressure gauge.
27. Do not mix the oil, unless it conforms fully to IS:335.
28. Do not allow inferior oil to continue in transformer/reactor. The oil should be
immediately processed and to be used only when BDV/ppm conforms to IS:1866.
29. Do not continue with pink silicagel, this should immediately be changed or
regenerated.
30. Do not leave secondary terminal of an unloaded CT open.
31. Do not store transformer/reactor for long after reaching site. It must be erected
and commissioned at the earliest.
32. Do not keep the transformer/reactor gas filled at site for a longer period.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
4.5.2
DO’S FOR POWER TRANSFORMER/REACTOR
1. Check and thoroughly investigate the transformer/reactor whenever any
alarm or protection operated.
2. Check air cell in conservator.
3. Attend the leakages on the bushing immediately.
4. Examine the bushings for dirt deposits and coats, and clean them
periodically.
5. Check the oil in transformer and OLTC for di-electric strength and moisture
content and take suitable action for restoring the quality.
6. Check the oil level in oil cup and ensure air passages are free in the
breather. If oil is less, make up the oil.
7. Check the oil for acidity and sludge as per IS:1866.
8. If inspection covers are opened or any gasket joint is to be tightened,
then tighten the bolts evenly to avoid uneven pressure.
9. Check and clean the relay and alarm contacts. Check also their operation,
and accuracy and if required change the setting.
10. Check the protection circuits periodically.
11. Check the pointers of all gauges for their free movement.
12. Clean the oil conservator thoroughly before erecting.
13. Check the buchholz relay and readjust the floats, switches etc.
14. Inspect the painting and if necessary retouching should be done.
15. Check the OTI and WTI pockets and replenish the oil, if required.
16. Remove the air through vent plug of the diverter switch before you energise
the transformer.
17. Check the oil level in the diverter switch and if found less, top up with
fresh oil conforming to IS:335.
18. Check the gear box oil level, if less top up with specified oil.
19. Examine and replace the burnt or worn out contacts as per Annexure 4.1
of Maintenance Schedule.
20. Check all bearings and operating mechanism and lubricate them as per
schedule.
21. Open the equalising valve between tank and OLTC, wherever provided
at the time of filling the oil in the tank.
22. Connect gas cylinder with automatic regulator if transformer is to be
stored for long, in order to maintain positive pressure.
23. Fill the oil in the transformer/reactor at the earliest opportunity at site
and follow storage instructions.
24. Check the door seals of marshalling Box. Change the rubber lining if
required.
25. Equalise the diverter compartment of the OLTC by connecting equalising
pipe between flange joints provided on the tap changer head.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412
4.6
DISPOSAL
The items to be disposed off are mineral oil, silicagel, gasket and other
insulating material. For disposal of these items, following procedure is
recommended.
4.6.1
INSULATING OIL :
The transformer oil is mineral Hydro Carbon (Petroleum) oil. No special
risks are involved in the handling and use of transformer oil. Howerver, attention
is drawn to the need for personnel hygiene i.e washing of skin & clothing,
which has come in contact with oil by personnel dealing with these products.
Hands in such cases should be washed carefully before eating and drinking
and contaminated clothing should be changed. Also inhalation of fumes or
vapours should be avoided.
When used oil has to be disposed off, certain precautions are necessary
to avoid risk of environmental pollution such as large spillage and leakage
from the containers, which may otherwise result into destruction of greenary,
water birds, fishes.
Normally, non contaminated oil free of PCB (Poly Chlorinated Biphenyls)
can be destructed by burning or sent to local authorities for asphalt production.
However contaminated oil containing PCB shall be filled in drums and sent to
local authorities for disposal.
4.6.2
SILICAGEL :
When silicagel can not be regenerated and to be disposed off, it can be
dumped in a pit and covered with earth.
4.6.3
GASKET AND OTHER INSULATING MATERIAL :
Crok Gaskets & Nitrile Rubber Gaskets can be disposed off by burning
in a place separately marked and prepared for the purpose. In case these can
not be burnt, these can be dumped in a pit and covered with earth.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412