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Chapter 1 FAIL IN LINEAS

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CHAPTER 1
INTRODUCTION
1.1
Introduction:
The dependency of secure power is increasing in the society which leads to higher demands on
the availability of electric power. The availability can be defined as the fraction of time that the
electric power is available in a certain point in the network during a given time interval. The
complement to availability is called unavailability and is the fraction of time that the electric
power is unavailable in a certain point in the network during a given time interval. Most of the
electric power in Bangladesh is transmission through the 132 kV substations that are parts of
the main grid. Many of the 132 kV substations in the main grid are today old and needs to be
modernized. It has also in the last years occurred a number of faults in these substations that
has increased the actuality of making the substations more reliable. The term reliability is
closely related to the term availability and can be defined as the probability of failure-free
operation of a system for a specified period of time in a specified environment. One major
difference between the reliability concept and the availability concept is that the availability
can be decreased by both planned and unplanned unavailability while the reliability concept
only considers the equipments ability to function correctly when it is in service. The steam
power stations which are owned by the company PDB, produces approximately 60% of the
total consumption of electricity in Bangladesh. Transmission line of Bangladesh is as well
connected to the 132 kV substation but through a 33 kV substation. The 400 kV substation
needs now to be replaced due to its age and due to the upgrades of active power output
capability of the generators in Bangladesh power grid. The suggested design consists of double
bus bars and double disconnecting circuit breakers, DCBs, which has the disconnect or
function integrated in the circuit breaker. The DCBs are meant to replace the conventional
combination of circuit breakers and separate disconnectors. The existing substation consists of
four bus bars of which one is a transfer bus bar used to bypass faults in the event of fault in any
of the devices in the substation. The existing substation has a relatively large flexibility to
change connection by operation of circuit breakers and disconnectors.
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1.2 Problem Statement:
It has been questioned by EEL if faults on the disconnecting circuit breaker in the proposed
substation design will cause high unavailability for EEL. This thesis has investigated how the
unavailability will be affected on the incoming lines to the substation, that are connected
between EEL power transformers T1 and T2 and the 33 kV substation. However, when
replacing an old system with a new one it is of importance to not only consider the
improvement of the new system, but also consider the possible drawbacks. To do this it
necessary to define the requirements on the system. The substation could be seen as a part of a
larger electricity system that consists of generation, distribution and consumption of electricity.
The demands on the larger electricity system is to continuously produce and distribute
electricity of good quality to satisfy the instantaneous electricity consumption in each point of
the grid. The quality of the electricity is of importance to make the equipment connected to the
grid function correctly without being damaged. From this discussion it is possible to derive two
requirements on the substation. First, it should under normal conditions continuously distribute
and be able to switch the electric power that the generators are producing. Second, it should
minimize the function loss of the substation when a failure occurs and it should help to
maintain the quality of the electricity. For the first requirement, the substation needs to contain
switching devices and control equipments for the switches. The function of the switches is to
control the connection and disconnection of the incoming power from the high voltage stations
at Simpevarp and to switch the connection to the outgoing lines. The switching can both be
controlled by manual operation and by the protection system, which mainly consists of circuit
breakers and protection systems. The circuit breaker can from a reliability point of view be
seen as 1) an high voltage apparatus that can cause short circuit or earth faults and 2) a
switching device that is used to break load and fault current. The purpose of the protection
system is to sense if a fault condition occurs in the protected zone and send a tripping signal to
the concerned circuit breakers around the protected zone. When a component has been
disconnected it will be unavailable. To determine the unavailability in a point of the protection
system it is necessary to consider the basic criteria‘s of a protective systems that commonly
includes the following factors(1) selectivity, (2) speed of operation (3) reliability, (4) simplicity and (5) costs.
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1.3 Objectives:
The purpose of this thesis was to construct a program that can be used for reliability
calculations and to use this program to compare and evaluate how the suggested two-breaker
arrangement design and the existing 11 kV substation in Simpevarp will differ in terms of
production availability for EEL.
1.4 Methodology:
This chapter starts with a motivation of the chosen methodology. It continues with an
explanation of how the study was performed and how the data was collected. Next follows a
discussion of the validity of the study and in the end there is an explanation of how the factors
that affect the availability have been measured.
1.4.1 Motivation for the Chosen Methodology:
The determination of the expected future reliability (Li 2005) of a system is done by a risk
evaluation. Power system risk evaluation normally includes these four tasks:
1. Determination of component outage model
2. Selecting possible states of the system and calculating the probabilities.
3. Evaluating the consequences of selected system states
4.Calculating the risk indices The purpose of a risk evaluation is often to manage the expected
risk. Risk management normally includes:
1. A risk evaluation to determine the quantitive risk
2. Determination of measures to reduce risk
3. Evaluation and justification of an acceptable risk level.
For power systems the acceptable risk level is always a balance between costs and the
reliability of the system. There are a few different techniques that traditionally have been used
in reliability evaluations of substations and their substations. These techniques can be divided
into two categories. In the first category the failure states are selected deterministically, these
are often referred to as state enumeration techniques and can include Marko chains, fault tree
analysis, cut set methods and linear programming. In the second category the fault states are
determined stochastically with a Monte Carlo analysis. The main advantage of state
enumeration techniques over the stochastically technique is its simplicity and it is normally
preferable when dealing with smaller systems. For larger systems that are more complex,
Monte Carlo simulation are instead normally preferred. This study is based on a state
enumeration technique given by Meeuwsen and Kling (1997) who introduced a technique to
deal with the complex switching options in a substation. Many earlier studies have neglected
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the complex switching option, which is to switch disconnectors to bypass faults, and instead
chosen to evaluate simpler configurations which many times are inconsistent with the real case
where switching normally has been possible.
1.4.2 Data Collection:
The study has primarily been based on secondary data collected from EEL‘s intranet as well as
from the databases and literature available through Chalmers library. Most of the reliability
studies that have been used for comparison have been obtained from the database IEEE. For a
general understanding of the function of the substation has one guided visit to the 132 kV
substation at Simpevarp been made which included visit to the control house. The function of
the substation and its protection system has been explained by personnel at EEL.
1.5 Validity of the Study:
The validity of the result of this study is highly dependent on the quality of the data used to
appreciate the failure rates and the repair times as well as on the model that is used to calculate
the availability. The statistical data used in this study suffers from a few unavoidable problems.
First, the number of faults that occurs in substation equipment is generally quite low and with a
small statistical population follows a high uncertainty. Second, there are only a few sources
available for fault statistics for the Swedish grid and these are in general limited to just
showing the average fault values and no variance is for this reason possible to obtain. The data
used for the fault frequencies and repair times are historical data collected from a grid with a
large part of ageing components and might not be representative for a newly build substation.
However, a large part of the uncertainties with the point estimation of the input data used in the
model is avoided by performing a sensitivity analysis that makes it possible to make some
more general conclusions about the relative advantages between the different designs.
1.6 Thesis Outline:
This Project/thesis is organized as follows:
Chapter1 Introduction
Chapter 2 Literature Reviews
Chapter 3 Substation of EEL
Chapter 4 Hardware Development
Chapter 6 Hardware Development
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CHAPTER 2
LITERATURE REVIEWS
2.1 Introduction:
A substation is a component of an electricity transmission or distribution system where voltage
is transformed from high to low, or the reverse, using transformers. A transmission substation
transforms the voltage to level suitable for transporting electric power over long distances. This
is to minimize capital and operating costs of the system. Once it is transported close to where it
is needed, a distribution substation transforms the voltage to a level suitable for the distribution
system. So the assembly of apparatus used to change some characteristic of electric supply is
called a substation In a substation using step up and step down transformer change AC voltages
from one level to Another, change AC to DC or DC to AC. A substation may have one or more
relates transformers, many protective equipment and switches. Substation is important part
of power transmission and distribution system. Substations are the most critical part of any
electrical supply grid. A failure of a single piece of substation equipment Can cause a total grid
collapse which may take days or even longer to rectify. The continuity of power supply
depends on successful operation of substations. It is therefore essential to exercise Extreme
care while designing and building a substation. Specific functions of substation are Power
transformer. Local network for Connection point. Switchyard, bus-bars, circuit breakers,
disconnections. Measuring point for control center – Potential and current transformers. Fuses
and other protection device.
Classification of substations: There are the two most important ways of classifying a
substation. According to1. Production requirement
2. Constructional features
2.2 According to Production requirement:
A substation may be called upon to change voltage level or improve power factor or convert ac
power into depower etc. According to service requirement 11kV substation is Transformer
substation. In this substations using power transformer changes voltage level of electric supply.
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2.3 According to constructional features:
A substation has many components (e.g. Circuit breaker, switches, fuses, instrument etc.)
Which must be used properly to ensure continuous and reliable service?
According to constructional features the substation is outdoor type Substation. The outdoor
equipment is installed under the sky. Outdoor type substations should be in fenced enclosures
or located in special-purpose buildings. Indoor substations are usually found in urban areas to
reduce the noise from the transformers, for reasons of appearance, or to protect switchgear
from extreme climate or pollution conditions 11/.440 kV Substation Arrangement The
arrangement of substations can
be
done in many ways. However the main sectors of
arranging the substations are – At load center: Where voltage is getting down 11kV to 400volts
using transformer and this is near to be load center.
2.4 Substation Layout:
Figure: 11KV to 440V Substation Layout
a) Principle of Substation Layouts Substation layout consists essentially in arranging a number
of switch gear components in an ordered pattern governed by their function and rules of spatial
Separation.
b) Spatial Separation:
i. Earth Clearance: This is the clearance between live parts and earthed structures, walls,
screens and ground.
ii. Phase Clearance: This is the clearance between live parts of different phases.
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iii. Isolating Distance: This is the clearance between the terminals of an isolator and the
connections.
iv. Section Clearance: This is the clearance between live parts and the terminals of a work
section. The limits of this work section, or maintenance zone, may be the ground or a platform
from which the man works.
c) Separation of maintenance zones Two methods are available for separating equipment in a
maintenance zone that has been isolated and made dead.
i. The provision of a section clearance
ii. Use of an intervening earthed barrier the choice between the two methods depends on the
voltage and whether horizontal or vertical clearances are involved.
2.5 Equipment Function:
To provide reactive Power during low load Neutral Grounding Resistor Limit the earth current.
Function of Substation:
1 – Supply of required electrical power.
2 – Maximum possible coverage of the supply of network.
3 – Maximum security of supply.
4 – Shortest possible fault-duration.
5 – Optimum efficiency of plants and the network.
6 – Supply of electrical power within targeted frequency limits (49.5 Hz and50.5 Hz).
7 – Supply of electrical power within specified voltage limits.
8 – Supply of electrical energy to the consumers at the lowest cost.
2.6 Elements of a Substation:
Substations have one or more transformers, switching and control equipment. In a substation,
circuits breakers are used to interrupt any short-circuit or overload currents that may occur on
the network. Substations do not usually have generators, although a power plant may have
substation nearby. Other devices such as power factor correction capacitors, synchronizer and
voltage regulators may also be located at a substation. The main equipment‘s of substation are
shown 11/.440 kV Substation equipment‘s details Transmission line set giving the rated
voltage level up to 11 kV. This 11 kV lines are connected to the 2MVA transformer via 11 kV
bus bars is further connected to LT switchgear. The equipment required for a transformer SubStation depends upon the type of Sub-Station, Service requirement and the degree of protection
desired. 11kV Sub-Station has the following major equipment‘s.
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2.6.1 Transformer:
2 MVA 33/11KV Main Transformer(4 MVA.3 MVA.2 MVA. &1.5 MVA)
2. Lightning arrestor
3. Isolator and Earth switches
4. Current Transformer
5. Potential Transformer
6. Duplicate type bus bar
7. Insulators
8. PFI Plant
9. LT Switchgear–3000Amps, 2500Amps, 1600Amps.1250Amps, 1000Amps.
All LT Switchgear is Various ACB/ABB.
2.6.1.a Faraday’s law of induction, which states that:
The induced electromotive force (EMF) in a y closed circuit is equal to the e time rate of
change of the magnetic flux through the circuit. Or alternatively: The EMF generated is
proportional to the rate of change of the magnetic flux. Where Vs. is the instantaneous voltage,
Ns is the number of turns in the secondary coil and Equals the magnetic flux through one
turn of the coil. If the turns of the coil are oriented perpendicular to the magnetic field lines, the
flux is the product of the magnetic flux density B and the area A through which it cuts. The
area is constant, being equal to the cross-sectional area of the transformer core, whereas the
magnetic field varies with time according to the excitation of the primary. Since the same
magnetic flux passes through both the primary and secondary coils in an ideal transformer, the
instantaneous voltage across the primary winding equals Electrical power is transmitted
from the primary circuit to the secondary circuit.
2.6.1.b Transformer EMF equation:
If the flux in the core is purely sinusoidal, the relationship for either winding between its rms
voltage Erm of the winding, and the supply frequency f, number of turns N, core crosssectional Area a and peak magnetic flux density B If the flux does not contain even
harmonics the following equation can be used for half-cycle. There are only 4 possible
transformer combinations: Delta to Delta – use: industrial applications Delta to Wye use: most
common for step-up transformer; commercial and industrial Wye to Delta use: most common
for step-down high voltage Wye to Wye use: rare, don‘t use causes harmonics and balancing
problems.
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2.6.2 Characteristics of Distribution Transformer:
1. According to method of cooling
* Oil-immersed, combination self-cooled and fan -cooled
2. According to insulation between windings a. Windings insulated from each other
* Autotransformers
3. According to number of phase‘s a Poly-phase
4. According to method of mounting a. Platform
5. According to purpose
* Constant-voltage
* Variable-voltage
6. According to service a. large power
* Distribution
2.6.3 Bus-bar Trunking:
Figure: Bus bar Connections
Bus-bars are the important components in a substation. There is several bus-bar arrangements
that can be used in substation. The choice of a particular arrangement depends upon various
factors such as voltage, position of substation, degree of reliability, cost etc. These are made up
of copper and aluminum to which the terminal of generators, transformers, distribution lines,
loads etc. is connected. In an electrical power distribution system that conduct electricity
within a switchboard, distribution board, substation, or other electrical apparatus. These busbars are insulated from each other and also from the earth. The size of the bulbar is important
in determining the maximum amount of current that can be safely
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carried. Bus
bars can have a cross-sectional area of as little as 10 mm² but electrical substations may use
metal tubes of 50 mm in diameter (1,963 mm²) or more as bus bars.
2.6.3.a The following are the important bus-bar arrangements used in substation.
• Single Bus-bar
• Single Bus-bar system with Sectionalization
• Double/Duplicate bus-bar arrangement
Duplicate type Bus-bar this system consists of two bus-burs, a main bar-bar and a spare busbar. Each bus bar has the capacity to take up the entire substation load .The incoming and
outgoing lines can be connected to either bus-bar with the help of a bus bar coupler which
consists of a circuit breaker and Isolators. The incoming and outgoing lines remain connected
to the main bus bar. However, in case of repair of main bus-bar or fault occurring on it, the
continuity of supply to the circuit can be maintained by transferring it to the spare bus-bar.
Insulators the insulator serves two purposes. They support the conductor (or bus bar) and
confine the current to the conductor. The most commonly used material for the manufactures
of insulators is porcelain. There are several type of insulator (i.e. pine type, suspension type
etc.) and there used in Sub-Station will depend upon the service requirement.
2.6.4 Insulators:
The insulator serves two purpose. They support the conductor and on fine the current to the
conductor. The most commonly used material for the manufactures of insulators is porcelain.
There are several type of insulator (i.e. pine type, suspension type etc.) and there used in SubStation will depend upon the service requirement.
2.6.5 Earth system:
Figure: Earth System of 11/.44kv Substation
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2.6.5.a Why ground?
Poor grounding not only contributes to unnecessary downtime, but a lack of good grounding is
also dangerous and increases the risk of equipment failure. Without an effective grounding
system, we could be exposed to the risk of electric shock, not to mention instrumentation
errors, harmonic distortion issues, power factor problems and a host of possible intermittent
dilemmas. If fault currents have no path to the ground through properly designed
and maintained grounding system, they will find unintended paths that could include people.
2.6.5.b What is a ground and what does it do?
The NEC, National Electrical Code, Article 100 defines a ground as: ―a conducting connection,
whether intentional or accidental between an electrical circuit or equipment and the earth, or
twosome conducting body that serves in place of the earth.‖ When talking about grounding, it
is actually two different subjects: earth grounding and equipment grounding. Earth grounding
is an intentional connection from a circuit conductor, usually the neutral, to a ground electrode
placed in the earth. Equipment grounding ensures that operating equipment within a structure
is properly grounded. These two grounding systems are required to be kept separate except for
a connection between the two systems.
2.6.5.c What is a good ground resistance value?
There is a good deal of confusion as to what constitutes a good ground and what the ground
resistance value needs to be. Ideally a ground should be of zero ohms resistance. There is not
one Standard ground resistance threshold that is recognized by all agencies. However the
NFPA and IEEE have recommended a ground resistance value of 5.0 ohms or less. The NEC
has stated to ―Make sure that system impedance to ground is less than 25ohms specified in
NEC 250.56. In facilities with sensitive equipment it should be 5.0ohms or less.
The Telecommunications industry has often used 5.0ohms or less as their value for grounding
and bonding.
2.7 Components of a Ground electrode:
Ground conductor
• Connection between the ground conductor and the ground electrode
• Ground electrode
2.7.1 Locations of Resistances:
(a) The ground electrode and its connection the resistance of the ground electrode and its
connection is generally very low. Ground rods are generally made of highly conductive / low
resistance material such as steel or copper.
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(b) The contact resistance of the surrounding earth to the electrode The National Institute of
Standards(a governmental agency within the US Dept. of Commerce) has shown this resistance
to be almost negligible provided that the ground electrode is free of paint, grease, etc. and that
the ground electrode is in firm contact with the earth.
(c) The resistance of the surrounding body of earth the ground electrode is surrounded by earth
which conceptually is made up of concentric shells all having the same thickness. Those shells
closest to the ground electrode have the smallest amount of area resulting in the greatest degree
of resistance. Each subsequent shell incorporates a greater area resulting in lower resistance.
This fin ally reaches a point where the additional shells offer little resistance to the ground
surrounding the ground electrode. So based on this information, we should focus on ways to
reduce the ground resistance when installing grounding systems.
2.7.1.a What affects the grounding resistance?
First, the NEC code (1987, 250-83-3) requires a minimum ground electrode length of 2.5
meters (8.0 feet) to be in contact with soil. But, there are four variables that affect the ground
resistance of a ground system:
1. Length/depth of the ground electrode
2. Diameter of the ground electrode
3. Number of ground electrodes
4. Ground system design
2.7.2 Length/depth of the ground electrode:
One very effective way of lowering ground resistance is to drive ground electrodes deeper. Soil
is not consistent in its resistivity and can be highly unpredictable. It is critical when installing
the ground electrode that it is below the frost line. This is done so that the resistance to ground
will not be greatly influenced by the freezing of the surrounding soil. Generally, by doubling
the length of the ground electrode you can reduce the resistance levels by an addition an
l0%. There are occasions where it is physically impossible to drive ground rods deeper—
areas that are composed of rock, granite, etc. In these instances, alternative methods including
grounding cement are viable.
2.7.3 Diameter of the ground electrode:
Increasing the diameter of the ground electrode has very little effect in lowering the resistance.
For example, you could double the diameter of a ground electrode and your resistance would
only decrease by 10 %.
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2.7.4 Number of ground electrodes:
Another way to lower ground resistance is to use multiple ground electrodes. In this design,
more than one electrode is driven into the ground and connected in parallel to lower the
resistance. For additional electrodes to be effective, the spacing of additional rods needs to be
at least equal to the depth of the driven rod. Without proper spacing of the ground electro
des, their spheres of influence will intersect and the resistance will not be lowered. To assist
you in installing a g that will meet your specific resistance requirements, you can use the
table of ground resistances, below. Remember, this is to only be used as a rule of thumb,
because soil is in layers and is rarely homogenous. The resistance values will vary greatly.
2.7.5 Ground system design:
Simple grounding systems consist of a single ground electrode driven into the ground. The use
of a single ground electrode is the most common form of grounding and can be found outside
your home or place of business. Complex grounding systems consist of multiple ground rods,
connected, mesh or grid network, ground plates, and ground loops. These systems are typically
installed at power generating substations, central offices, and cell tower sites. Complex
networks dramatically increase the amount of contact with the surrounding earth and lower
ground resistances.
2.7.5.a How do I measure soil resistance?
To test soil resistivity, connect the ground tester as shown below. As you can see, four earth
ground stakes are positioned in the soil in a straight line, equidistant from one another. The
distance between earth ground stakes
should be at least three times greater than the stake
depth. So if the depth of each ground stake is one foot(.30meters), make sure the distance
between stakes is greater than three feet(.91meters). The Fluke 1625 generates a known current
through the two outer ground stakes and the drop in voltage potential is measured between the
two inner Ground stakes. Using Ohm‘s Law (V=IR), the Fluke tester automatically calculates
the soil resistance. Because measurement results are often distorter and invalidated by
underground pieces of metal, underground aquifers, etc. additional measurements where the
stake‘s axis are turned 90 degrees is always recommended. By changing the depth and distance
several times, a profile is produced that can determine a suitable ground resistance system.
Soil resistivity measurements are often corrupted by the existence of ground currents and their
harmonics. To prevent this from occurring, the Fluke 1625 uses an Automatic Frequency
Control (AFC) System. This automatically selects the testing frequency with the least amount
of noise enabling you to get a clear reading.
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2.8 Fall-of-Potential measurement:
The Fall-of-Potential test method is used to measure the ability of an earth ground system or
an individual electrode to dissipate energy from a site.
2.8.a How does the Fall-of-Potential test work?
First, the earth electrode of interest must be disconnected from its connection to the site.
Second, the tester is connected to the earth electrode. Then, for the 3-pole Fall-of-Potential
test, two earth stakes are placed in the soil in a direct line-away from the earth electrode.
Normally, Spacing of 20 meters (65feet) is sufficient. For more detail on placing the stakes,
seethe next section. A known current is generated by the Fluke 1625 between the outer stake
(auxiliary earth stake) and the earth electrode, while the drop in Voltage potential is measured
between the earth stake and the earth electrode. Using Ohm‘s Law (V=IR), the tester
automatically calculates the resistance of the earth electrode. Connect the ground tester as
shown in the picture. Press START and read out the RE (resistance) value. This is the actual
value of the ground electrode under test.
2.9 Specification of Substation:
11/0.415kV, 2MVA Sub-station of Instrument is …
a) 2MVA 33/11Kv Main Transformer,
b) LT Switchgear-5000A 4000A 3000A
c) Dropout Fuse, Rated Voltage (Nominal) -11kV, Rated Current RMS -100A, 1Set
d) Lightning Arrester, Rated Voltage (RMS) – 9kV, 1Set
e) 2Mva – 3 Units1500 KVAR-tow units, 150KVAR 3-Units Automatic PFI Plant.
f) Current Transformer, Ratio 2500/5A 1000/5A-500/5A,
g) Potential Transformer, Ratio -11//110V, 3pcs.
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2.9.1 Setup Information:
Factory requirement following as there instrument will be ascension. There Instrument of the
figure same as connection from the distribution line. First time we are connected Isolator.
It
connect to main line include drop out Fuse 15A, 3pcs, for 3phase. Isolator one terminals
connect to main distribution line (11kv line) another terminal connects to current transformer
of primary side. This Isolator attach on the front of poll after transformer connection.
Transformer connected is delta to star, primary side is delta and secondary side is star. Primary
side voltage is 11kV and secondary voltage is 415V. Secondary side of common terminal
connected to grounding and also transformer body connected to grounding. Primary side
bushing number is 3pcs. And secondary side bushing number is 4pcs. Transformers all of
check, oil level, silica gel, temperature, and all nut bolt. Transformer secondary side connects
to LT switch gear (Low tension) its medium is LT cable. There have 4 LT of (Radiator room,
Transformer Tank Section, miscellaneous section, Machine-Shop and Paint section), Nickel
section. All are connects by 185 and 95 RM cables. Now Low tension switch gear connection
Low tension indoor type switchgear with hard drawn copper bus-bars, TPN&E equipped with
incoming connected is 1no. 1600A, 36kA, TP MCCB with adjustable thermal overload and
adjustable magnetic short-circuit releases. 3 Current transformer, ratio: 690/5A with suitable
accuracy and burden. 3 -Ammeter 0-500A, 1Voltmeter 0-500V, with selector switch. 2
indicating lamp on/off and 1 set control fuse. Outgoing is 1, 2 and 3 CB 1250A, 36kA,
TP MCCB with adjustable thermal overload and adjustable magnetic short circuit releases. No.
of 4 CB, 690A, 18kA, TP MCCB with adjustable thermal overload and adjustable magnetic
short circuit releases. Distributed to factory machineries by some low tension switchgear by
the. And power factor improvement plant connected from low tension switchgear. Substation
last pert is 250kVAR automatic power factor improvement plant connected. It is flour
mounting, 415V, 50HZ, 250kVAR indoor type Automatic power factor improvement plant. To
direct connections connected by another CB.
2.9.2 Comprising:
1500kVAR bank of TP dry type power 3-capacitor with built-in discharge resistor (Direct).
With 1500kVAR bank of TP dry type power capacitor Built-in to discharge. Automatic power
factor correction relay. Use some TP air contractors of adequate ratings. HRC fuses with base
of adequate rating. Indicating lamps and 1 set control fuses. And other gives the connected on
Distribution Box, Switching board etc. There are connected from low tension switchgear.
Connect the Machineries line from Distribution Box. And all Instrument & machineries of
body connected to earth grounding.
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2.10 Operation of Sub-station:
At many places in the line of the power system, it may be desirable and necessary to change
some characteristic (voltage, frequency, power factor etc.) of electric supply. This is
accomplished by suitable apparatus called substation. The sub-station operation explained as
under:
1) The 3-phase, 3-wire of 300rm 11kV line is tapped and brought to the gang operating switch
installed near the sub-station. The G.O. Switch consists of isolators connected in each phase of
the 3-phase line.
2) From the G.O. Switch, the 11kV line is brought to the indoor sub-station as underground
cable of 185RM. It is fed to the H.T. Side of the transformer (11kV/400V) via the 11kV O.C.B.
The transformer steps down the voltage to 400V, 3-phase, 4 wires per wires are 120Rm, but
together 630Rm.
3)The secondary of transformer supplies to the bus-bars via the main OCB. From the bus- bars,
400V, 3phase, 4-wire supply is given to the various consumers via 400V OCB. The voltage
between any phase and neutral it is 230V. The single phase residential load is connected
between any one phase and neutral whereas 3-phase, 400V motor load is connected across 3phase lines directly.
4) The CTs are located at suitable place in the sub-station circuit and supply for the metering
and indicating instruments and relay circuits. Total 23 DB, and many Circuit barkers. All DB
connects by 95RM Cables.
2.11 Maintenance and Trouble shutting:
Symmetrical Fault the symmetrical fault rarely the symmetrical fault is occurs in practice as
most severe and imposes more majority of the fault are of heavy duty on the circuit unsymmetrical nature breaker. The reader to understand the problems that, short circuit
conditions present to the power system. Single line to ground, any line with short to the
Separate to the line from short fault. Ground faults. Designed Circuit for solve the problem.
1.
Line to line fault. One line with another line to separate to the line from short. Circuit for
solving the problem. Insulation problem.
2.
Double line to ground two line with short to the Separate to the line from short fault.
2.11.1 Problems:
3.
Arc phenomenon when a short-short
circuit Arc
resistance is made
to occurs, a
heavy current increase with time so that flows the contacts of the current is reduced to a value
circuit breaker. Insufficient to maintain the arc.
16
4.
The ionized particles between the contacts tend to maintain the arc. Transformer open circuit an
open circuit in one phase open phase connected with to fault. Of a 3-phase transformer circuit
may cause undesirable heating.
2.11.2 Relay protection is not provided against open circuits:
5.
On the occurrence of such because this condition is fault, the transformer can be relatively
harmless. Disconnected manually from the system.
6.
Transformer overheating over heating of the relay protection is also fault. Transformer
is usually not provide against this caused by sustained contingency and thermal overloads or
short-circuit accessories are generally used and very occasionally by the two sound an alarm or
control failure of the cooling the bank of fans.
2.11.3 System:
7.
Transformer Winding short-circuit (also the transformer must be short circuit fault. Called
internal faults)on the disconnected quickly from the
8.
Transformer arises from system because a prolonged deterioration of winding arc in the
transformer may insulation due to cause oil fire.
2.11.4 Overheating or mechanical injury:
9.
Lightning for over voltage the surges due to internal Surges due to internal causes fault. Causes
hardly increase their taken care of by providing.
10.
System voltage to twice the proper insulation to the normal value. Equipment in the power
system.
11.
A lightning arrester is a protective device which conducts the high voltage surges on the power
system to the ground.
12.
Low voltage Supply voltage is low. Transformer tap changing turn to move after solved the
problem.
2.12 Switchgear:
The term switchgear, used in association with the electric power system, or grid, refers to the
electrical
equipment like isolators, fuses, circuit breakers which intended to
connect
and
disconnect power circuits are known collectively as switchgear. Switchgear is used in connect
with generation, transmission, distribution and conversion of electric power for controlling,
metering protecting and regulating devices. A basic function of switchgear power systems is
protection of short circuits and overload fault currents while simultaneously providing service
continuously to unaffected circuits while avoiding the creation of an electrical hazard.
Switchgear power systems also provide important isolation of various circuits from different
17
Power supplies for safety
issues. There are many different types and classifications of
switchgear power systems to meet a variety of different needs. Switchgear power systems can
vary, depending on several factors, such as power need, location of system and necessary
security. Therefore, there are several different types of switchgear Power systems and each has
their own unique characteristics to meet the specific needs of the system and its location.
Figure: LT Switchgear
2.12.1 Switchgear instruments of Factory:
Factory has low voltage (up to 380 volt) and medium voltages (up to 400V) switch gear. It is
indoor type and switch gear instruments are:
1) Circuit breaker:-Miniature circuit breaker, Vacuum circuit breaker, MCC breaker.
2) Relay– Distance Relay, over current and Earth
fault
relay, Under/Over voltage relay,
Trip circuit supervision relay, Differential protection relay, Static relay:
3) Current transformer (C T)
4) Potential transformer (PT)
5) Fuse
6) Lightning arrestor
7) Isolator and Earth switches
8) Magnetic conductor
2.13 Current transformers (CT):
Current Transformers are used in current circuits in protection systems employing secondary
relays. This transformer is to measure large currents and differs in phase from it by an angle
18
which is approximately zero for an appropriate direction of the connections. This highlights the
accuracy requirement of the current transformer but also important is the isolating function.
Figure: Current Transformer (CT)
The Primary which is usually of few turns or even a single turn or thick copper or brass bar is
inserted into the core of the transformer is connected in series with the load. The secondary
current is normally rated for 5A or 1A and the number of turns in the secondary will be high.
When the current transformer has two secondary windings then one winding is connected to
the protective Relay system and there is to indicating metering circuit. Current transformer
windings are polar in nature. The current transformers with 1A rating secondary can handle
25 times more burden than the current transformers of 5A secondary. Current Transformers of
1ASecondaries are normally used in the protection of 11 kV–132 kV. Transmission lines
where the substation apparatus is located at a considerable distance from the control room,
where the relays are situated. The magnitude of the current which flows through the secondary
winding of a CT is a function of the primary current, the transformation ratio and also the
impedance of the secondary circuit. CT‘s normally operate under Conditions close to shortcircuit conditions. The Secondary winding burden further depends upon the method of
connection of the CT secondary, the relay windings and the kind of short circuit experience.
CT‘s used for extra high voltage network protection must be capable of accurately transmitting
currents both during steady state process and under transient conditions in order to permit
operation of the protective devices correctly. The reasons for choosing proper CT‘s for extra
high voltage network protection are;
1. The time constants of DC components in the short circuit currents of EHV networks are
large.
2. The ratio of the short circuit current to the rated current is very high, due to increased
concentration.
19
3. High Speed relaying is essential to protect electrical equipment during fault
and to increase system stability
The accuracy of a CT is directly related to a number of factors including:
 Burden
 Burden class/saturation class
 Rating factor
 Load
 External electromagnetic fields
 Temperature and
 Physical configuration.
 The selected tap, for multi-ratio CT‘s
 Ratio 5000/5A
2.14 Potential Transformers (PT):
Figure: potential transformers (PT)
Instrument Transformers are of means of extending the range of AC in strumpets like
ammeters, voltmeters, V.A.R. Meters, Walt-meters. They are two types of potential
transformers. The primary of the potential transformers is connected across the transmission
line whose voltage may range from 2.4 kV to 220 kV. The secondary voltage is standardized at
110 kV. The load connected to the secondary is referred to as burden Small leakage reactance.
The leakage reactance is due to the leakage of the magnetic fluxes of the primary & secondary
voltages. They can be minimized by keeping the primary, secondary windings as close as
possible subject to insulation
problem as the primary is at high voltage. Small Magnetic
20
current. This can be achieved by making the reluctance of the core as small as possible and
flux density in the core is also lowland it is very less than 1wb/m.
2.14.1 Minimum Voltage Drop:
The resistance of the windings is made as small as possible. The Primary as it
carries high
voltage should be heavily insulated. Hence it is immersed in oil and the terminals are brought
out to porcelain bushing. Now-a-days synthetic rubber insulation like styrene is used avoiding
oil and porcelain. When the load or burden on the secondary is increased, the secondary current
increases with corresponding increase in primary current so that transformation ratio remains
the same.
2.14.2 Specification of Potential Transformer
• Manufacturer
: Energypac
• Device maximum operating voltage
: 2000kV
• Rated frequency
: 50-60Hz
• Rated voltage
: 11 kV
• Rated output
: 440V
2.14.3 Lightning Arrestor:
Figure: Lightning arrester
A lightning arrester is a device used on electrical power systems to protect the insulation on
the system from the damaging effect of lightning. Metal oxide arrestors (MOVs) have been
used for power system protection since the mid1970s. The typical lightning arrester also
known as surge arrester has a high voltage terminal and a ground terminal. When a lightning
surge or switching surge travels down the power system to the arrester, the current from the
surge is diverted around the protected insulation in most cases to earth.
21
2.14.4 Specification of Lightning Arrestor:
• Manufacturer
: ABB
• Rated voltage
: 11kV
• Rated current
: 50-60Hz
• Rated discharging current
: 10kA
• Continuous operating voltage
: 100.8kV
• Residual voltage under thunder in : 10kA 615kV peak
• Standard discharging current
: 1.0kAPeak
2.15 Circuit Breaker:
Figure: Circuit Breakers
A circuit breaker is an automatically-operated electrical switch designed to protect an electrical
circuit from damage caused by overload or short circuit. Its basic function is to detect a fault
condition and these by interrupting continuity, to immediately discontinue electrical flow
principle of Operation All circuit breakers have common features in their operation, although
details vary substantially depending on the voltage class, current rating and type of the circuit
breaker. The circuit breaker must detect a fault condition in low-voltage circuit breakers this
is usually done within the breaker enclosure. Circuit breakers for large currents or high
voltages are usually arranged with pilot devices to sense a fault current and to operate the trip
opening mechanism. The trip Solenoid that releases the latch is usually energized by a separate
battery,
although some high-Voltage
circuit
breakers are self-contained
with
current
transformers, protection relays and an internal control power source. Once a fault is detected,
contacts within the circuit breaker must op en to interrupt the circuit. Some mechanically22
stored energy (using something such as springs or compressed air) contained within the breaker
is used to separate the contacts, although some of the energy required may be obtained from
the fault current itself. The circuit breaker contacts must
carry the load current without
excessive heating, and must also withstand the heat of the arc produced when interrupting the
circuit. Contacts are made of copper or copper alloys, silver alloys and other materials. Service
life of the contacts is limited by
the erosion due to interrupting the arc. Miniature circuit
breakers are usually discarded when the contacts are worn, but power circuit breakers and
high-voltage circuit breakers have replaceable contacts.
2.15.a Classification of Circuit Classification of Circuit Breaker According to the voltage
level circuit breaker are classified into three categories, such as
1. Low Voltage Circuit Breaker (Up to 619 volt)
2. Medium Voltage Circuit Breaker (Up to 11kV)
3. High Voltage Circuit Breaker (Up to 145kV)
2.15.1 Low Voltage Circuit Breaker:
• A contact system with arc-quenching and current-limiting means
• A mechanism to open and close the contacts
• Auxiliaries which provide additional means of protection and indication of the switch
positions. The MCCB may be used as an incoming device, but it is more generally used as an
outgoing device on the load side of a switchboard. It is normally mounted into a low-voltage
switchboard or a purpose-designed panel board. In addition to the three features listed at the
start of this section, it also includes:
• An electronic or thermal/electromagnetic trip sensing system to operate through the tripping
mechanism and open the circuit breaker under overload or fault conditions
• All parts housed within a plastic molded housing made in two halves
• Current ratings usually from 10A to 1600A.
2.15.2 Medium Voltage Circuit Breakers:
Medium-voltage circuit breakers rated between 440 Voltage and 11kV assemble into metalenclosed switchgear line ups for indoor use in MPS substation. Medium voltage circuit
breakers are also operated by current sensing protective relays operated through current
transformers. Medium-voltage circuit breakers nearly always use separate current sensors and
protective relays, instead of relying on built-in thermal or magnetic over current sensors.
23
2.15.3 High-voltage circuit breakers:
Electrical power transmission networks are protected and controlled by high-voltage breakers.
The definition of high voltage varies but in power transmission work is usually thought to be
72.5 kV or higher. In MPS used SF6 circuit breaker for high voltage in substation. Highvoltage Breakers are always solenoid-operated, with current sensing protective relays operated
through current transformers. In substations the protective relay scheme can be complex,
protecting equipment and busses from various types of overload or ground /earth fault.
2.15.4 Miniature Circuit Breaker (MCB):
Miniature circuit breakers rated current not more than 100A trip characteristic normally not
adjustable. The miniature circuit
breaker (MCB) has a contact system and means of arc
quenching, a mechanism and tripping and protection system to open the Circuit breaker under
fault conditions. Early devices were generally of the ‗zero-cutting‘ type, and during a short
circuit the current had to pass through a zero before the arc was extinguished; this provided a
short circuit breaking capacity of about 3kA. Most of these early MCBs were housed in
Bakelite moldings. The modern MCB is a much smaller and more sophisticated device. All the
recent developments associated with molded case circuit breakers have been incorporated into
MCBs to improve their performance, and with breaking capacities of 10kA to 16kA now
available, MCBs are used in all areas of commerce and industry as a reliable means of
protection. Most MCBs are of single-pole construction for use in single-phase circuits.
2.15.5 Vacuum circuit breaker:
Figure: Vacuum circuit breakers
Vacuum circuit breaker with rated current up to 3000A, these breakers interrupts the current
by creating and extinguishing the arc in a vacuum container. These are generally applied for
24
voltages up to about 35,000V but PS use vacuum circuit breaker for 11KV which corresponds
roughly to the medium voltage range of power systems. Vacuum circuit breakers tend to have
longer life expectancies between overhaul than do air circuit breakers. Vacuum circuit breakers
tend to have longer life expectancies between overhaul than do air circuit breakers. In a
vacuum circuit breaker, two electrical contacts are enclosed in a vacuum. One of the contacts is
fixed, and one of the contacts is movable. When the circuit breaker detects a dangerous
situation, the movable contact pulls away from the fixed contact, interrupting the current.
Because the contacts are in a vacuum, arcing between the contacts is suppressed, ensuring that
the circuit remains open. As long as the circuit is open, it will not be energized. Vacuum
recluses will automatically reset when conditions are safe again, closing the circuit and
allowing electricity to flow through it. Re-closers can usually go through several cycles before
they will need to be manually reset Vacuum interrupters, mounted vertically within the circuit
breaker frame, perform the circuit.
2.15.6 Specification of Vacuum circuit breaker:
• Rated frequency-50 -60Hz
• Rated making Current-10 Peak kA
• Rated Voltage-11kV
• Supply Voltage Closing-220 V/DC
• Rated Current-1250 A
• Supply Voltage Tripping-220 V/DC
• Insulation Lev el-IMP 75 KVP
• Rated Short Time Current-40 kA (3 SEC)
2.16 Fuses:
25
Figure: Fuses
A fuse is a short piece of wire or thin strip which melts when excessive current flows through it
for sufficient time. It is inserted in series with the circuit to be protected. Under normal
operating conditions the fuse element it at a temperature below its melting point. Therefore, it
carries the normal load current without overheating. However when a short circuit or overload
occurs, the current through the fuse element increases beyond its rated capacity. This raises the
temperature and the fuse element melts (or blows out), disconnecting the circuit protected by
Inuit Electronics and electrical
engineering a fuse (short for fusible link) is a type of
sacrificial over current protection device. Its essential component is a metal wire or strip that
melts when too much current flows, which interrupts the circuit in which it is connected. Short
circuit, overload or device failure is often the reason for excessive current.
2.16.1 Fuse Ratings:
2.16.1.a
Ampere Rating:
Each fuse has a specific ampere rating, which is its continuous current-carrying capability.
There are different types of fuse used in MPS, rating start from 2A. Voltage rating the voltage
rating of a fuse must be at least equal to the circuit voltage. The voltage rating of a fuse can be
higher than the circuit voltage, but never lower. A 500 volt fuse, for example, could be used in
a 450 volt circuit, but a 350 volt fuse could not be used in a 500 volt circuit.
2.16.1.b
Magnetic Contactor:
A magnetic contactor is a relay-controlled switch used to turn a power control circuit on and
off. It is electrically controlled and uses less power than other circuits. A magnetic contactor
comes in different forms and capacities. Magnetic contactors are a form of electrical relay
found on most electrically powered motors. They act as a go-between for direct power sources,
and high-load electrical motors in order to homogenize or balance out changes in electrical
26
frequency which may come from a power supply as well as to act as a safeguard Components a
magnetic contactor has three parts: power contacts, contact springs and auxiliary contacts. The
power contact creates, carries and breaks the current in a magnetic contactor. Input a basic
magnetic conductor has a coil input that is driven by either a DC or AC supply, and it can be
energized at the same voltage as the motor. It can also be controlled separately using programmable controllers and low voltage pilot devices. Most contactors handle lighting, Heating,
electric motors and capacitor banks
2.16.1.c
Function of Magnetic conductor:
Figure: Magnetic conductors
Contactors are usually fitted on open contacts, and are designed to suppress and control electric
arcs which are produced by interrupting heavy motor currents. They work on the principle of
electromagnetism and the electricity runs through the coil from the core of the contactor. While
the core is moving, a force is developed that allows the electromagnet to carry charge and hold
the contacts together. Once the contactor coil is de-energized, the spring of the electromagnet
returns to its original position.
2.17 Summary of This Chapter:
I joint to EnergyPac Engineering Ltd. Factory for internship. This factory of all worker and
management is very good and helpfully. Their help for my internship period happen be easy,
therefore I would highly obliged. There, I learn to 11kv/.440kv Sub-station, Generator,
Switchgear and factory maintenance division of equipment‘s are working principle, competent
and possible cause‘s solution. Hare, many new machine, instruments & tools about understood.
There are many problem to face and there with try to solution. This is my new experience. I am
very enjoy the internship period, because it a new situation, new work and new problem
solution invention and new learn of goods are characters. I hope this experience will need of
my service and my future.
27
CHAPTER 3
ANALYSIS AND SIMULATION
3.1 Introduction
Electrical utility has three functional areas namely generation, transmission and distribution. In
the distribution network there are two main distribution network lines namely, primary
distribution lines (33kV/22kV/11kV) and secondary distribution lines (415 volts line voltage).
Primary distribution lines feed the HT consumers and distribution transformers. The
distribution transformers feed the low voltage distribution networks which are the secondary
distribution lines. Hence low voltage distribution network (LV network) is the last link
connecting the consumers. Each of the primary distribution line leaves the sub-station as a
three-phase circuit and supplies a number of distribution transformers. On the secondary side
of the distribution transformer, the Secondary distribution lines are connected. The distribution
transformers and secondary distribution lines are rated to maintain the voltage received by
consumers within a prescribed tolerance over the full range of loading conditions. The Figure 1
shows the distribution system prevalent in EEL. The main part of distribution system includes:-
3.2 Analysis of Distribution System
Figure : Distribution System
28
Figure : Sub-transmission lines.
Figure : Secondary circuits on the LV side of the distribution transformer.
Figure : Service mains with metering arrangement.
The existing system in the distribution network is manually controlled. The distribution
transformers are located at convenient places in the load area. At the distribution transformer,
the voltage is stepped down to 415V and power is fed into the secondary distribution systems.
The secondary distribution system consists of distributors (Pillar Boxes) which are laid along
the road sides. The service connections to consumers are tapped off from the distributors. The
29
main feeders, distributors may consist of overhead lines or cables or both. The distributors are
3-phase, 4 wire circuits, the neutral wire being necessary to supply the single phase loads.
There are single phase and three phase services given by the electrical utility depending on the
requirement of consumers. The service connections of consumer are known as service mains.
A ground connectionism normally provided, connected to conductive cases and other safety
equipment, to keep current away from equipment and people. For single phase services the
phase and neutral conductors from distribution transformer is connected to Figure 1.
3.3 Performance of distribution system
The distribution system requires more attention as it is very difficult to standardize due to its
complexity. As it involves consumers, power quality becomes paramount consideration in
feeding the power supply. With a quality power there is need for uninterrupted supply of
power. To avoid shortage of power one important consideration is reduction of transmission
and distribution losses. Transmission and distribution losses (t & d losses) in Bangladesh have
been consistently on the higher side between the ranges of 21–25%. Out of these losses, 19% is
at the distribution level in which 14% is contributed by technical losses. This is due to
inadequate investments for system improvement work. The detailed analysis of distribution
transformers with different types of loading patterns have to be studied for solving power
quality issues. Such data are not available in scientific way for analysis across the country.
Therefore, DSP has been developed. At most care has been taken to collect the data of LV
network from different places like metro, urban and rural populated regions to be analysed
using DSP. Valentina Cecchi and et al (2007) have designed instrumentation and measurement
configuration for network configuration and meter placement. The work is in primary
distribution network and it is not extended up to secondary distribution network. Aderiano
Galindo Leal and et al (2009) describes artificial neural network approach for loss evaluation
of distribution transformer. The authors have recorded seven-day load profiles of distribution
transformers of Brazilian distribution utility which proves uniformity in stochastic nature of the
loads. That is, load profiles of different categories of consumers can be grouped under clusters
as residential, commercial and industrial. But it requires daily load profiles of consumers
whereas daily load profiles of distribution transformer are only available in developed
country‘s scenario. Hence development of DSP for developing countries‟ is significant
contribution for distribution sector.
30
3.4 Development of distribution simulation package
In the existing system of distribution network, energy meters are provided for energy
accounting. There is no means of sensing unbalance currents, voltage unbalance and power
factor correction requirement for continuous 24 hours in three phases of LT Feeder. In other
words, load curves, voltage curves, energy curves and power factor curves for individual three
phases for full day are not available for monitoring, analyzing and controlling the LV network.
To solve this, the modules developed in the DSP are listed below along with their associated
function.
Load Survey Module: Collection of 30 minute readings on the daily load pattern of
distribution transformer.
Power measurement Module: The measurement of power (Real, Reactive and Apparent) and
display of voltage –current (vi-profile), power factor and power in the front panel for each
phase R, Y and B.
Display Module: The display of voltage graph showing all three phases, current graph with all
three phases, power graph showing all three phases and total power for any selected day for the
low voltage distribution network. These graphs are effectively utilized for load analysis and to
study the power quality performance of low voltage distribution network.
Unbalance Prediction Module: Prediction of unbalance in the network for the day selected
and display them with LED indicators.
3.4.1 Design of Simulation Package
In the existing system of distribution network, the distribution transformers are fixed with
energy meters in the secondary of the distribution transformer and energy meter readings are
downloaded with CMRI. The energy meter reading includes voltage current profile (vi–profile)
and power factor. It can because for power measurement. With additional functionalities
developed in this work like plotting of all electrical parameters on graph, prediction of
unbalance current, LabVIEW based system can be termed as effective management and
monitoring Module (MMM)for low voltage distribution networks.
3.5 Load analysis
Load analysis of distribution transformers with different loading patterns deduces
Significant inferences for the work presented in this paper. For performing load analysis,
distribution simulation package developed as discussed in Section 3.1 is effectively utilized.
One number sample transformer has been presented in this paper as case study. Typical loads
on low voltage networks are stochastic by nature. However it has to be ensured that there is
31
similarity in stochastic nature throughout the day. For arriving at practical and effective
conclusion for formulating this pragmatic methodology and to solve the power quality
issues,the study has been undertaken using DSP.
Balanced Condition
Unbalanced condition
Balanced Condition in two phases
Unbalanced Condition in two phases
Input to the DSP
Low voltage distribution album of distribution transformer. Meter readings of distribution
transformer (30minute readings).
Output from the DSP
Power measurement
Voltage graph
Load (Current Graph)
Power graph and Total power
3.5.1 Load Analysis of Sample Distribution Transformer
The schematic diagram with low voltage distribution album is shown in Figure 8. Energy
Measurement for one day is shown in Figure 9 and load graphs for 2 different days taken at
random are shown in Figure10 and Figure 11.
3.6 Results and Discussions
The detailed analysis of distribution transformers with different types of loading patterns leads
to very interesting findings as summarized below.
Though the load utilization of individual consumers is a variable factor, there is uniformity
found in stochastic nature.
The per-capita consumption of electricity is high in urban compared to rural areas.
The peaks and valleys in load graphs tend to follow similarity though not identical in all types
of distribution network.
The high peak occurs in approximately same band of one hour every day, the major variation
may be two hours which is also very rare.
The peak load of the transformer occurs when majority of the consumers connected to
distribution network utilizes most of the loads. It occurs in the same time band of peak load of
the distribution transformer due to prevailing culture and
32
habit of the people.
The percentage of unbalance between phases is observed to be proportionate and hence value
of unbalance will be maximum during peak loads.
3.7 Summary:
All the inferences made out of low voltage distribution network load analysis prove that
optimization of low voltage distribution network can be achieved by proper planning and
successful reconfiguration of consumers to avoid unbalance of loads in distribution LV
network. This distribution package serves as a backbone for the load analysis. With this
method of load analysis and load reconfiguration there is a possibility of energy saving in
terms of millions of rupees to the nation.
33
CHAPTER 4
HARDWARE DEVELOPMENT
4.1 Introduction:
There are 3 substations within campus – Substation A,B,C. The 11kv 3phase supply is directly
received at Substation A. From there we have 11kV feeder running to Sub B and C. For the
purpose of distribution it is first step down to 440V. Single phase lines of 230 V are distributed
among the various loads (department, hostel, lab, library etc.). For the purpose of backup each
substation is equipped with 250kVA diesel generator. Its kVA rating is not enough to drive
both the departments as well as the hostel at the same time. So it is usually switched between
them depending upon the requirement. During day time, most of are gone for classes so in case
of power failure, diesel generator if run supplies to the department only. Whereas at night, the
authorities give priority to water pumping and then to the mess and the hostel. In VNIT you
won‘t find overhead cables. The large number of trees falling during rainy season leading to
interruption in power supply plus increased maintenance expenditure had forced the authorities
to shift all the cables underground.
4.2 Main Component of 11kV substation:
4.2.1 Circuit breakers:
Circuit breaker does the task of on load making and breaking of the circuit. This task can't be
done in open air for high voltage as it leads to arcing as a result of ionization of air.
There are different type of circuit breakers :
1.
Gas Circuit Breakers
2.
Oil Circuit Breakers
3.
Vacuum Circuit Breakers
4.
Air Circuit Breakers
For 11kV, Vertical isolation VCB's are installed at VNIT substation. It uses spring energy for
making and breaking of the circuit. It is 3 pole VCB having a rated current rating of 800A.It
has a breaking capacity up to 20kA. The making and breaking time of the installed VCB is 3
cycles. Panel installed above it are for monitoring of relay protection, tripping etc.
34
4.2.2 Other advantages of Vertical isolation VCB are :
1.
A time tested product for high reliability
2.
Motorized spring charging mechanism
3.
Cost effective solution by add-on protective devices like Series tripping coils.
4.
Portable earthing device for bus bar feeder earthing
3-pole Air Circuit Breaker is installed on the 400V incomer coming form the transformer.
For lower voltage level Ie. at the distribution end, MCCB of 250A rating are installed on each
phase (Phase Voltage =230V). There are air circuit breakers which uses arc chutes for
extinguishing of the arc produced during the process.
Figure: Vacuum Circuit Breaker
4.2.3 Current transformers:
Current transformers are installed at various stages in a network. Current transformers serve
two basic purposes :
Measurement of current Driving Protection relays
Current transformers usually have 1 -5A on the secondary side. 5A is usually required for
driving protection relays. As for example the CT installed on the 400V incomer from
transformer is 600:5. For measurement purposes we 200:1 or 400:1 etc rating.
4.3 Transformer :
Figure: Transformer
35
Transformer is a constant flux device used for changing the ac voltage level. Each substation
has two 400kVA 11kV/400V delta - star step down transformer of which one of them is
standby in case some problem occurs. It is provided with ONAN type of cooling.
4.4 Auxiliaries attached to transformer:
3.4.1 Conservator:
The above described transformer is filled with 310Kg of oil for the purpose of cooling. Due to
heating of the oil, oil will expand. If space is not provided to allow expansion, the transformer
will burst. To prevent such scenario from being created, Conservators are installed on the top
of the transformer to allow expansion.
4.4.2 Buchholz relay:
Buchholz relay is a mechanical actuator, which trips the transformer in case of internal faults
like insulation breakdown, short circuit of winding etc. Due to these faults the temperature
rises and there is decomposition of insulating oil and gases are produced which get
accumulated in the upper part of the Buchholz relay. This leads to tilting of the mercury
switch. Based upon the level, the alarm is produced and relay comes in action.
4.4.3 Silica Jell:
One of the biggest enemy of transformer is the moisture. To deal with these, the transformer
are provided with silica jell box. It is blue in color. As it absorbs moisture it becomes pinkish.
Then it is required to be replaced. They can be reused after placing them in light for some time.
They lose their moisture content and become blue again and ready to be reused. However with
every use the silica content keeps on getting reduced so it can't be used
infinitely and needs to be replaced with new one.
4.4.4 Various:
Various other components such are thermometer, pressure release valve, tap changer are
present to ensure smooth functioning of the transformer.
4.5 Capacitor Bank:
Capacitor Bank is installed in each substation to improve the power factor. Power factor is
keep close to 1 usually .99 by using different combination of 25kVAR and 50kVAR of
Capacitors.
36
Figure: Capacitor Bank
4.6 Distribution Panel:
Distribution Panel contains panels containing Circuit Breakers for each department, hostel etc.
so that the can be switched on and off depending upon the requirement.
Figure: Distribution Bord(DB)
4.7 Diesel Generator Set:
To ensure uninterrupted supply in case of power failure within the campus, each substation
has a 250kVA Diesel Generator Set. Since it is less than 400kVA transformer that are meant to
power the campus, the DG set is incapable of powering the normal load at once. So usually
power is restored depending upon the requirement as stated earlier.
Figure: Diesel Generator
37
DG set installed is a GPW250 model Greaves power 50Hz DG set of dimension 4*1.8*2.15
(m). It is a 3 phase generator set with operating power factor of 0.8 and maximum load current
capacity of 347.8A at this power factor. It has 24V, 2*180AH battery required for its starting
up. Integral fuel tank capacity provided is 420L. It uses water as coolant.
4.8 DG set comprises of two main parts:
1. Diesel Engine
2. Alternator
4.8.1 Diesel Engine:
Figure: Diesel Engine
It is a 6 cylinder, TBD3V8 Greaves model rated at 1500rpm and output of 313HP. It has lub oil
sump capacity of 29L and Greaves Maxtherm API CF is used as lub oil. For starting the
engine 24V battery is installed. AMF Panel is provided with a start button to start the generator
remotely. However before this the Changeover should be moved from the transformer side to
the diesel engine side. It is used as prime mover for the alternator.
4.8.2 Alternator:
Figure: Alternator
38
The shaft of the diesel engine is connected to a 3 phase, 4 poles brush-less generator of 250
kVA, 415V and power factor of 0.8. It is provided with IP23 protection and class-H insulation.
4.9 Other features:
Ease of maintenance with integrated components and outboard Exciter/Rotating Rectifier. A
reliable long life with superior class 'H' insulation. Higher motor starting capability. Compact,
light and sturdy die cast aluminum stator for frames up to 250, offer superior finish. High
thyristor load withstand capability for Cell-Phone and Telecom applications. Short circuit
withstand capability. Wide range of coupling discs/adaptor for single bearing construction
suitable for wide range of Engine makers.
Additionally there is air cleaner pumps for proper functioning of the DG set. Also we have
various meters for oil level, water temperature, battery charge indicator etc for monitoring the
health of the set. The whole DG set is provided with an acoustic enclosure to prevent noise
pollution. Also regular maintenance is done to extend the life of the DG set. And lastly an
important question!!Ever wondered what's the electrical bill of our campus??
It's 30 lakhs per months!! So when they ask us to save electricity, they do actually mean it.
4.10 Summary of The Chapter:
A substation in which the apparatus is equipped inside the substation building is called indoor
substation. Such type of substation is mainly used for the voltage up to 11000 v, but when the
surrounding air is contaminated by impurities such as metal corroding gases and fumes,
conductive dust, etc., their voltage can be raised up to 33000v to 66000v. The indoor substation
is subdivided into several compartments like control compartment, indicating and metering
instruments and protective device compartment main bus-bar compartment, current
transformer and cable sealing box compartment as shown in the figure below. For the
protection of feeders usually, reverse power relay is used. For the protection of oil filled
transformer Buchholz relay is used. The accessories of the indoors type substations are a
storage battery, fire fighting equipment such as water, buckets, and fire extinguisher, etc., The
battery is used for the operation of protective gear and switching operating solenoids and
emergency lighting in substations in the case of failure of supply.
Indoor substations and transformer substation, as well as, high voltage switchboards consist of
a series of open and enclosed chamber or compartments. The main equipment for this
39
installation is arranged in these compartments. The chamber space within which the equipment
of the main bus-bar is connected is called a compartment or a cubical cell.
4.10.a Substations of the Integrity Built Type: In such type of substation, the device is
equipped on site. In such substation, the cell structure is constructed of concrete or bricks.
4.10.b Substations of the Composite Built-Up Type: In such type of substations factory or
workshop are built but are assembled on site within a substation switch gear room. The
compartments of such substations take the form of metal cabinets or enclosures, each of which
contains the equipment of one main connection cell. In such cabinets, an oil circuit breaker, a
load interrupter switch, and one or more voltage transformers may be mounted.
4.10.c Unit Type Factory Fabricated Substations and Metal Clad Switchboards: These
are built in electrical workshops and are carried to the site of installations fully pre-assembled.
After installations of substations and switchboards only connection to the incoming and
outgoing power circuits are required to be made
40
CHAPTER 5
RESULTS AND DISCUSSIONS
5.1 Introduction:
Electricity is the basic necessity for the economic of a country. The industrial development and
the increase of living standard of people are directly related to the more use of electricity.
Without it is not possible to drive industrial machine, pump for irrigation and possible to
develop living slandered of people. It is quit impossible for us to study on protective devices in
a distribution substation. So in short we have tried to discuss the main components of the
power protection system of the distribution substation. It has seen that fuses, circuit breakers,
relays, lightning arresters, isolators, ear-thing and current limiting reactors are used as
protective devices of distribution substation system protection.
5.2 Discussion of Low Voltage Substation:
The reason that we are at 400KV is to reduce the line currents. If we stepped down to 33 KV
then the current would be 12–13X and the wires would have to be correspondingly heavier.
Usually a step down is tied together with splitting of the power to multiple branches so each
branch will be carrying less power and hence lowers the current to manageable amounts at the
lower branch voltages. You need lower voltages in the branches because you are going from
large transmission towers with wide arms for air insulation to smaller towers and smaller
insulators. It's all a matter of scale. A distribution transformer is a transformer that provides the
final voltage transformation in the electric power distribution system, stepping down the
voltage used in the distribution lines to the level used by the customer. The invention of a
practical efficient transformer made AC power distribution feasible; a system using distribution
transformers was demonstrated as early as 1882. Distribution transformers normally have
ratings less than 500 kVA, although some national standards can describe up to 5000 kVA as
distribution transformers. Since distribution transformers are energized for 24 hours a day
(even when they don't carry any load), reducing iron losses has an important role in their
design. As they usually don't operate at full load, they are designed to have maximum
41
efficiency at lower loads. To have a better efficiency, voltage regulation in these transformers
should be kept to a minimum. Hence they are designed to have small leakage reactance.
5.3 Result of Low Voltage Substation:
Result of Substation and the thesis paper. The substations are constructed under roof is called
indoor type substation. Generally 11 KV and sometime 33 KV substation are of this type.
5.3.1 Step Down Substation:
The stepped up voltages must be stepped down at load centers, to different voltage levels for
different purposes. Depending upon these purposes the step down substation are further
categorized in different sub categories.
5.3.2Primary Step Down Substation:
The primary step down sub stations are created nearer to load center along the primary
transmission lines. Here primary transmission voltages are stepped down to different suitable
voltages for secondary transmission purpose.
5.3.3 Secondary Step Down Substation:
Along the secondary transmission lines, at load center, the secondary transmission voltages are
further stepped down for primary distribution purpose. The stepping down of secondary
transmission voltages to primary distribution levels are done at secondary step down
substation.
5.3.4 Distribution Substation:
Distribution substation are situated where the primary distribution voltages are stepped down
to supply voltages for feeding the actual consumers through a distribution network.
5.3.5 Underground Substation:
The substation are situated at underground is called underground substation. In congested
places where place for constructing distribution substation is difficult to find out, one can go
for underground sub-station scheme.
5.3.6 Pole Mounted Substation:
Pole mounted substation are mainly distribution substation constructed on two pole, four pole
and sometime six or more poles structures. In these type of substation fuse protected
distribution transformer are mounted on poles along with electrical isolator switches.
42
5.4 Summary of The chapter:
A distribution substation transfers power from the transmission system to the distribution
system of an area. The input for a distribution substation is typically at least two transmission
or sub transmission lines. Distribution voltages are typically medium voltage, between 2.4 and
33 kV depending on the size of the area served and the practices of the local utility. Besides
changing the voltage, the job of the distribution substation is to isolate faults in either the
transmission or distribution systems. Distribution substations may also be the points of voltage
regulation, although on long distribution circuits (several km/miles), voltage regulation
equipment may also be installed along the line. Complicated distribution substations can be
found in the downtown areas of large cities, with high-voltage switching, and switching and
backup systems on the low-voltage side.
43
CHAPTER 6
SUBSTATION OF EEL
6.1 Introduction:
Energypac Engineering Ltd. (EEL) is one of the leading power engineering companies in
Bangladesh. Continual research and development, state of the art production facility, quality
products, competent services, and countrywide operations have made it warmly acceptable to
the customers. Energypac was incorporated in 1982 as a private limited business enterprise. It
is powered by 1200 skilled manpower of which 150 are graduated engineers. The relentless
efforts and dedication of these people are providing continual help to improve technology to
innovate and develop new products, just in time delivery, pre and post sales services to
maintain a long term business relationship with the customers. To meet countrywide demand
of its products and services, Energypac has extensive distribution network throughout
Bangladesh with full-fledged offices in the major cities like Chittagong, Khulna, Rajshahi,
Sylhet, and Bogura. In an effort to introduce its products globally, Energypac has established
its offices in India, Nepal, Italy and China. Energypac has already experienced its products
and service supply to India, Nepal, Yemen, Ghana, Uganda, Nigeria, Saudi Arabia, Vietnam,
Korea, Philippines and United Kingdom.
6.2 Description:
Energypac is an ISO 9001:2008 and 14000:2004 certified company. Energypac enhances the
business of its customers by providing them with complete solutions. While creating better and
environmentally compatible technologies, Energypac focuses on the customers. Energypac is
one of the leading power engineering companies in Bangladesh. Continual research and
development, state of the art production facility, quality products, competent services, and
countrywide operations have made it warmly acceptable to the customers. Energypac was
incorporated in 1982 as a private limited business enterprise. It is powered by 1200 skilled
manpower of which 150 are graduated engineers. The relentless efforts and dedication of these
people are providing continual help to improve technology to innovate and develop new
products, just in time delivery, pre and post sales services to maintain a long term business
relationship with the customers. To meet countrywide demand of its products and services,
44
Energypac has extensive distribution network throughout Bangladesh with full-fledged offices
in the major cities like Chittagong, Khulna, Rajshahi, Sylhet, and Bogura. In an effort to
introduce its products globally, Energypac has established its offices in India, and China.
Energypac has already experienced its products and service supply to India, Yemen, Ghana,
Uganda, Nigeria, Saudi Arabia, and United Kingdom.
6.3 Construction:
Energypac provides complete solution to the customers including engineering, procurement
and construction (EPC). We deliver the keys of a commissioned plant to the owner for an
agreed amount, just as a builder hands over the keys of a flat to the purchaser. It is also a way
that needs the better understanding of customer‘s need for perfect execution of a project. An
EPC contract is important for several vital reasons. EEL provides total solution to the
customers for their power requirement from the project solution activities. Two broad
categories of the project solutions are Turnkey, and EPC (Engineering, Procurement, and
Construction). It entails project development, BOP development, project engineering, and
project management. Our knowledgeable, skilled and experienced engineers are getting
involved with the customers through all the stages of project conception, development,
implementation, and continuation. It happens from a tiny substation to a large project
implementation. Energypac Engineering Ltd. has an established department for taking care of
the projects. It starts with the concept development, and finishes with the successful
implementation of the project. It includes the preparation of project profile, feasibility study,
detailed engineering, outsourcing needful, managing resources, and draw fine finishes to the
projects. Desirous to be a cutting-edge engineering organization, EEL is relentlessly trying for
acquiring excellence in engineering knowledge, preparing BOQ & feasibilities, and practical
implementations of the projects. Relevant books are collected and consulted, trainings are
received, and hands on experience are achieved for establishing proven confidence. Stringent
calculations on different engineering aspects of product characteristics, performance analysis,
and environmental considerations have been made it possible to reengineer the product,
improvement in the quality of installations, and enhancement of performance.
6.4 Installation and Commissioning:
Energypac Engineering Ltd is acquainted with the installation and commissioning of thousands
of transformers, switchgears, and complete substations in its nearly 3 decade‘s long experience.
The entire process of installation and commissioning involves the preparation of BOQ,
45
ensuring availability of the right materials at the right quantity at the right time, physical
arrangements of transformer, switchgear, ancillary materials, and arrangement of all
equipment‘s as per the regulatory authority‘s requirement. The ultimate focus on this job is to
ensure that safety of the power transmission/distribution equipment, efficient power
transmission/distribution, and maximum care for the installation and the environment. The
commissioning of the equipment‘s has specific and stringent procedures to avoid premature or
wrong operations. It includes the checking of all connections and settings of equipment‘s and
ancillaries, load management, test run, and finally supplying power to the grid/loads.
Energypac has highly expert engineers who are designated only to perform the commissioning
jobs. They have received intensive trainings and are of highly experienced to demonstrate
perfections in their jobs.
6.5 Spare Parts:
Energypac Engineering Limited supports customers through the supply of genuine spare parts
from the globally reputed and authentic sources. We cater the demand of spare parts through
our business network all over Bangladesh as well as in abroad. The storage place at our factory
premise is a well-managed and controlled temperature and humidity warehouse. Each part is
entered, stored, and exited through modern software system. We maintain a huge stock of parts
for our own consumption as well as warranty and life time support of the equipment‘s.
6.6 Service and Maintenance:
Figure: Maintenance of Transformer
Energypac Engineering Ltd is involved with the service and maintenance of its own supplied
equipments and solutions. Basically it happens in two ways, on call basis, and contract basis.
46
On Call method allows the customers to call EEL‘s After Market Care (AMC) people to
provide service and maintenance when it requires, and are charged for the completion of that
particular job. We provide service and maintenance on 24/7 basis. Expert engineers and
technicians are just a call away from our valued customers to respond to their complaints and
act promptly. For Contracted Services, customers have to sign formal agreements with EEL for
a certain period of time with specified terms and conditions of service and maintenance.
Service and Maintenance Contracts may include schedule maintenance, unscheduled
maintenance, health-check and troubleshooting. During the contracted period, EEL people will
visit customer‘s facility as per the agreed schedule and provide service and maintenance. It is
divided into two categories.

LTSA (Long Termed Service Agreement): Under LTSA customers are contracted for
long term services which may include spare parts also. It gives the customers comfort in
keeping the price of parts and services valid for several years.

STSA (Short Termed Service Agreement): STSA facilitates customers to take the
benefits of taking discounted price on services and spares for a reasonable short period of
time.
47
CHAPTER 7
CONCLUSION
7.1 Conclusion
7.2 Limitation of work
7.3 The Future of 11kV/440V Substation
7.1 Conclusion:
For a technical service provider plant O&M activities are very important as its service mostly
depends on the availability of its equipment. To maintain properly it requires very efficient
O&M activities with minimum costing. By using proper O&M schedule of substation costcan
be reduced and supply can be increased. O&M is traditionally classified as a part of output that
comes from the system. There are many diverse ways of evaluating O&M of power system, as
well as different objectives. O&M comprises all measures for maintaining and restoring the
target condition as well as determining and assessing the actual condition of the technical
equipment in a system. During this study, it has been observed from the organizational point of
view where it has been implemented. There are so many improvements and applications that
can be offered through this substation which of course would have direct benefit for the
organization.
7.2 Limitation of Work:
The researched problem in this thesis was to analyze how the suggested two-breaker
arrangement design will differ from the existing substation considering the following aspects:
The following points should be developed 
All instruments should be clearance between two equipment.

Bus-bar should be used 20% or 30% ampere greater than the load current.

Every circuit breaker really has time setting option from 0-1sec. If circuit breaker is
more than one the time setting should be from 10ms to 80ms or 10ms to 1sec from load
circuit breaker to generator circuit breaker.

Transformer oil and silica gel should be checked after one month or any types of fault
occurs any time . Oil should be changed if it is decomposed.
48

All cable should be cheek before use or any kinds

They use manually based equipment, if they use PLC based equipment then the system
will be easier.

If they use new technology then the system loss will be reduce.

High system loss, it will be reducing.

Expected unavailability due to faults and maintenance
Thesis Problem: The researched problem in this thesis was to analyze how the suggested twobreaker arrangement design will differ from the existing substation considering the following
aspects:
• Expected unavailability due to faults and maintenance
• Fault and maintenance frequencies
• Costs of the different substation designs
Purpose: The purpose of this thesis was to construct a program that can be used for reliability
calculations and to use this program to compare and evaluate how the suggested two-breaker
arrangement design and the existing 11 kV substation in Simpevarp will differ in terms of
production availability for EEL. Other factors that earlier have been mentioned as being of
importance for the choice of substation design are the space that the construction will require
and the possible affect the construction will have on the environment. This thesis will not
further consider space limitation of the substation configurations. The new DCBs (ABB 2015)
contain the gas SF6 which is a gas that contributes to the greenhouse effect. The handling of
the gas needs to be done in an environmental friendly way which increase the demands on the
maintenance, like for example refilling of the gas and testing of the gas pressure. The
environmental aspect has not been considered further in this thesis.
7.3 Future Scopes of the Work:
It takes smart approaches and powerful technologies to meet the world‘s soaring demand for
electrical energy and to transmit power to where it is needed most. High-voltage substations
are the node points of the increasingly complex power transmission infrastructure. They play a
key role in enabling the reliable transmission of large amounts of power. As a turnkey
contractor, Siemens offers the one-stop planning and construction of customized, state-of-theart high-voltage substations worldwide.
Finally, it could also be of interest to investigate the different interests of the users of the
substation. This can be divided into four groups. First, EEL that supply the grid with power.
Second, BPDB that owns the substation and has the main responsibility for the function of the
49
main grid. Third, the electricity consumers that is dependent of the supply of electric power
and fourth, the other electricity producers that is dependent on a well functioning grid to be
able to deliver and sell their production of electric power. All of these can be assumed to be
interested in a well functioning substation. However, EEL and BPDB can have different
priorities concerning where in the grid it is important to have high availability. BPDB have
responsibility for the availability in the whole main grid while EEL interest is more concerned
with the ability to deliver its produced electricity to the main grid. This thesis will only
concentrate on how the production availability for EEL is affected by the suggested new
substation design. The factors that are important for EELs ability to deliver its power is both
the unavailability on the incoming lines and on the outgoing lines. The incoming lines are the
lines connected between the power transformers and the substation. The outgoing lines are the
transmission lines leaving the substation and they are included in the study because the loss of
load might force EEL to limit its production of electricity. For this reasons the study will
concentrate on determining the unavailability in both the incoming and outgoing lines in the
substation.
7.3.1 Other Important Factors to Consider:
Other factors that earlier have been mentioned as being of importance for the choice of
substation design are the space that the construction will require and the possible affect the
construction will have on the environment. This thesis will not further consider space
limitation of the substation configurations. The new DCBs (ABB 2015) contain the gas SF6
which is a gas that contributes to the greenhouse effect. The handling of the gas needs to be
done in an environmental friendly way which increase the demands on the maintenance, like
for example refilling of the gas and testing of the gas pressure. The environmental aspect has
not been considered further in this thesis.
50
REFERENCES
[1] Books
i. Principlesof Power System by V.K Mehta & Rohit Mehta A Electrical Textbook of Electrical
Technology_Vol.2 by B.L Theraja. Transmission & Distribution by B.L. Theraja
ii. Protection and Switchgear by U.A.Bakshi and M.V. Bakshi Theraja. ii. J.B. Gupta, ―A Course in Electrical
Installation, Estimating & Costing‖; Published by S.K Kataria & Sons, 9thEdition.
iii. POWER SYSTEM ANALYSIS 5th ed
iv. A.S.Pabla, ―Electrical Power Distribution System‖, Tata McGraw-Hill, 5th Edition
[2] Journal
International Journal of Advanced Research in Electrical, Electronics and Instrumentation Engineering(An ISO
3297: 2007 Certified Organization)Vol. 3, Issue 11, November2014
Valentina Cecchi, Xiaoguang Yang, Karen Miu and Chipka Nwankpa, ―Instrumentation and Measurement of a
Power Distribution System laboratory for Meter Placement and Network reconfiguration Studies‖, IEEE
Instrumentation & Measurement Magazine, October 2007
[3] Online Links
http://www.assignmentpoint.com/science/eee/report-on-building-aspects-of-electric-substation.html
http://www.school-for-champions.com/science/electrical_generation.htm
http://electronics-polytech.wikispaces.com/DC+Generator
http://dc349.4shared.com/doc/spDAwc9C/preview.html
http://www.school-for-champions.com/science/dc_circuits.htm
http://ytcphyssci.wikispaces.com/Ohm's+Law
http://qiszqaiszmama.blogspot.com/2012/05/electricity-parallel-series-circuit.html
http://kiran111.hubpages.com/hub/electrical-substation
http://heag.en.alibaba.com/product/325207748200603654/JW_252_Outdoor_High_Voltage_Earthing_Switch.htm
http://en.wikipedia.org/wiki/Capacitor_voltage_transformer
https://www.google.com.bd/search?q=11kv/440v+substation+layout
http://commonelectricaldoubts.blogspot.com/2014/10/vnit-11kv-indoor-substation.html
http://www.electricaltechnology.org/2013/07/how-to-calculatefind-rating-of.html
https://iiteeeestudents.wordpress.com/2011/11/14/key-diagram-11kv400v-indoor-substation/
http://eblogbd.com/basic-of-substation-substation-design-part-1/
http://winsol.info/substation-hardware/
https://electricalnotes.wordpress.com/2011/06/08/11kv415v-overhead-line-specification-rec
http://macao.communications.museum/eng/exhibition/secondfloor/moreinfo/2_4_1_ACGenerator.html
http://circuitglobe.com/indoor-substation.html#ixzz4NGu8T3ts
http://www.oneschool.net/Malaysia/UniversityandCollege/SPM/revisioncard/physics/electromagnetism/induction.
html
51
Appendix
A
AC : Alternating Current
Alternator : A synchronous AC generator
Alternator rotor: The rotor consists of a coil of wire wrapped around an iron core
B
Bus-bar : The metal (often copper) bar system which is the distribution media for the
3-phase high voltage system in the power plant
C
Current Transformer: In electrical engineering, a current transformer (CT) is used for
measurement of electric currents. Current transformers are also known
as instrument transformers.
Capacitor : A device capable of storing electric energy. It consists of two conducting
surfaces separated by insulating material. It blocks the flow of direct
current while allowing alternating current to pass.
Conductor : A wire or cable for carrying current.
CT : Short for Current Transformer. An AC current measuring the generators to share the
reactive component of the
Current: The rate of flow of electricity. The unit of the ampere (A) defined as 1 ampere =
1coulomb per second.
Circuit Breaker: An automatic switch that stops the flow of electric current in a suddenly
over loaded or otherwise abnormally stressed electric circuit.
F
Frequency: Number of cycles over a specified time period over which an event occurs.
52
Feeder : The temperature to which oil must be heated in order to give sufficient vapor to
forma flammable mixture with air under the conditions of the test. The vapor will
ignite but will not support combustion
G
Generator: A device that produces electric current, usually by rotating a conductor in a
magnetic field, thereby generating current through electromagnetic induction.
H
Hertz (Hz): Units in which frequency is expressed. Synonymous with cycles per second
values. Machine language programs are often written in hexadecimal notation.
HT: High Temperature (cooling water circuit)
I
Isolator: A passive attenuator in which the loss in one direction is much greater than that in the
opposite direction; a ferrite
isolator for waveguides is an example.
L
Load: The electrical demand of a process expressed as power (watts), current (amps) or
resistance (ohms).
Load sharing: The way in which two or more alternators are run to accommodate the load
demands from the electrical network.
LT side: Low tension side.
O
O&M: Operation and Maintenance.
53
P
Parallel operation : More than one unit supplying power to the same network.
Phase line: A line in an electrical network having system voltage potential.
PLC : Programmable Logic Controller.
Power factor : The extent to which the voltage zero differs from the current zero. (p.f = kW
/kVA)
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