Load Flow Study Etap

Load Flow Analysis
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Load Flow Overview
Overview
Topics
Basic
Concepts
Methodology
3Ph & 1Ph Power
Goals
Steps
Non-Linear
Objectives
PF
Iterative
Methods
Capabilities
Per Unit
Loading &
Generation
Panels
Load & Gen
Categories
Study Case
Main & Subs
& Toolbars
Connections
Generation
Global
Adjustments
Schedule
Operation Modes
Data
Requirements
Lumped
Load
Load
Invertor, Charger,
Types
UPS
Decoupled
OLV Display
Generator
Systems
DataBlock, …
Limits
Exercise 1&2
IEEE Example
Example
Run
Studies
Panel
Advanced
Topics
Summary
Convergence
OPF
3-Phase
Alerts
2-Phase
1-Phase
Reports
Create Wizard
Result
Analyzer
Exercise 3
Blue – PowerPoint
Load Flow Analysis
Orange - ETAP
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Overview
•
•
•
•
•
•
•
•
Mother of all Studies
Load Flow Analysis is an Engineering Art
The Art of duplicating and understanding
the steady-sate behavior of Power Systems
First studies to be done to validate the project model
Last studies to be done to validate other studies
Has contradictory objectives with SC & TS studies
Need to consider past, present & future conditions
Need to consider all possible operating conditions
Compare limits & duties for the correct operation of
the power systems apparatus
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Overview
Objectives
• To Protect the System Against:
– Electrical Limits
• Over/Under Voltage conditions
• Over Load conditions
• Voltage and Current Limits
– Mechanical
• Tension & Stress Levels
• Life Time
– Thermal
• Steady-State Temperature Limits
• Emergency Temperature Limits
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Overview
Objectives
• Steady-State Operating Conditions









Load Flow Analysis
Voltage Profile
Power Flows
Current Flows
Power Factors
Voltage Drops
Generator’s Mvar Demand (Qmax & Qmin)
Generator’s MW Demand
Total Generation & Demand
MW & Mvar Losses
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Overview
Capabilities
Handel any kind of Integrated Network
No Limitations for the followings
 Connectivity / Subsystems
 DC, AC (1P-1W, 1P-2W, 2P-2W, 2P-3W, 3P-3W, 3P-4W
 Nominal Voltage
 Frequency
 Phase Connection
 Bus Number – 1,000,000+ tested
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Basic Concept
• Power in Balanced 3-Phase Systems
S 1  V
LN
I
*
S 3  3  S 1

3  V LL I *
 P  jQ
 Inductive loads have lagging Power Factors.
 Capacitive loads have leading Power Factors.
Lagging Power Factor
Load Flow Analysis
Leading Power Factor
Current and Voltage
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Load Flow Concept
• Leading & Lagging Power Factors
 Leading PF:
 Lagging PF:
P+jQ , -P-jQ
P-jQ, -P+jQ
Gen1
Bus3
4997.8
-j270.9
Cable1
6 %
99.5
Bus1
796.9
j330.5
Mtr1
-697.8
j289.4
Mtr3
Load Flow Analysis
796.9
j330.5
Syn1
Syn2
796.9
-j330.5
848.5
j525.9
LUMP1
848.5
-j525.9
LUMP2
793
j594.8
Load1
793
-j594.8
Load2
j892.1
CAP1
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Load Flow Concept
• Leading & Lagging Power Factors
 Current (amp) direction is based on the value of P (kW).
 Leading Power Factor are displayed as a negative value.
Gen1
Bus3
209.4
-99.9%
Cable1
6 %
99.5
209.4
-99.9%
Bus1
36.3
92.4%
Mtr1
-31.7
-92.4%
Mtr3
Load Flow Analysis
36.3
92.4%
Syn1
36.3
-92.4%
Syn2
41.9
85%
LUMP1
41.9
-85%
LUMP2
41.7
80%
Load1
41.7
-80%
Load2
37.5
0%
CAP1
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Load Flow Concept
• 3-Phase Per Unit System
 Three phase power equation

S  3VI 





V

3
ZI


 Base calculations
IB 
kVA B
3kVB
(kVB ) 2
ZB 
MVA B
 Per Unit calculations
I pu 
Zpu 
Load Flow Analysis
I actual
IB
Vpu 
Zactual
ZB
Spu 
Vactual
VB
Sactual
SB
Z
n
pu
V
 Z 
V
o
pu
o
B
n
B



2
 S Bn 
 o 
 SB 
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Load Flow Concept
• Elimination of Transformer Turn Ratio:
 To determine base voltage:
kVB1 
N1
kVB2
N2
Bus 1
kVB1
Bus 2
kVB2
 Impedance of transformer in per unit:
X pu
Load Flow Analysis
X
Z pu   
R 

2
X
1  
R 
R pu
Cabl
x pu

X
 R 
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Load Flow Concept
Base for per unit or % values in ETAP
 Machines Z
Rated kVA and kV
 ANSI Transformers Z
Rated Output kVA and kV
 IEC Transformers Z
Rated Input kVA and kV
 Base Voltage
Bus Nominal kV
% Loading Reports
 Loads
Rated kVA
 Transformers
Max kVA
 Lines & Cables
Allowable (Derated/U-D) Amp
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Load Flow Concept
• Example:
 Base voltage calculation across a transformer in ETAP:
 Branch impedances in LF report are in percentage
 Turn ratio: N1/N2 = 3.31
 X/R = 12.14
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Load Flow Concept
• Example (cont’d):
X pu 
0.065 (12 .14 )
1  (12 .14 ) 2
R pu 
 0.06478
0.06478
 0.005336
12 .14
 Impedance conversion to 100 MVA base
 “n” stands for new & “O” stands for old values
Z
n
pu
o
o  VB 
 Z pu  n 
 VB 
2
 S Bn 
 13.8 
 o   (5.33 10 3  j 0.06478)

S
13
.
5


 B
2
 100 

  (0.1115  j1.3538)
5


%Z  100  Zpu  11 .15  j135 .38
 The base voltage of the branch impedance (Z1) determined by
transformer turn ratio
kVutility 13 .5
VB 

 4.0695
N
1
  3.31
 N 2 
Load Flow Analysis
VB2
(4.0695 ) 2
ZB 

 0.165608
MVA
100
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Load Flow Concept
• Example (cont’d) :
Z pu 
Zactual (0.1  j1)

 (0.6038  j6.0382 )
ZB
0.1656
%Z  100  Zpu  60 .38  j603 .8
 Load flow report generated by ETAP for branches:
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Load Flow Concept
Decoupled Systems:
V 1  V1 1
V 2  V2  2
S  V  I   P  jQ
V  V2
 1
Sin(1   2 ) 
X
2
V1  V2
V2 
j
 Cos (1   2 ) 

X
X


V1  V2
P
Sin(1   2 )
X
2
V1  V2
V2
Q
Cos(1   2 ) 
X
X
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Load Flow Concept
Decoupled Systems:
Gen1
U1
1.7
j1.054
Bus1
1.7
j1.054
%
100
0 de
g
LUMP1
1.7
j1.054
1.707
j1.058
Gen2
%
101
3.26
j78.735
1.554
j77.677
0 de
g
Bus4
1.7
j1.054
Gen3
U3
%
100
1339.5
j91.184
1.7
j1.054
Load Flow Analysis
0 de
g
LUMP4
T2
LUMP5
%
100
0.162
-j75.854
LUMP3
Bus5
0 de
g
LUMP2
T1
U2
Bus3
Bus2
%
100
1.7
j1.054
1337.8
j90.13
10 d
eg
T3
Bus6
%
100
1331.5
-j144.6
1.7
j1.054
0 de
g
LUMP6
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Load Flow Concept
• Power transfer between two buses in per unit
1
( V E)
X
( V E)
X
sin 




cos 
Power Flow
1
0
2
V
X
1
2
2

0


Real Power Flow
Reactive Power Flow
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Methodology
 Goals
 Steps
 Non-Linear Solution
 Solution Methods
 Requirements
 Load Types
 PV, PQ Elements
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Goal
Methodology
A healthy operation under different conditions
*** Size Equipments & Determine Parameters ***

Cable

Lines

Capacitor

Transformer MVA Rating

Transformer Tap Setting & Limits

Current Limiting Reactor Ratings

MCC & Switchgear Current Ratings

Generator Operating Mode (Isochronous / Droop)

Generator’s Mvar Demand

Transmission, Distribution & Utilization kV
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Methodology
• Verify operation conditions within limits
 Bus Voltages are Within Acceptable Limits
 Voltages are Within Rated Insulation Limits of Equipment
 Power & Current Flows Do Not Exceed the Maximum Ratings
 Acceptable System MW & Mvar Losses
 Circulating Mvar Flows are Eliminated
 Steady State Stability Limits
• Validation of data in steady state condition
 Comparison of real time metered data with load flow results
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Methodology
• Load Flow Problem
 Given:




Power consumption at all buses
Branch impedances in the network
Network Topology (Configuration)
Generation and load VAriation
 Output:
 Voltage magnitude and angle at all buses
 Power flows on all the branches including power factors
 Losses on all branches
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Steps in a Project
Methodology
1. Understand the Scope of the Project and its Objectives
2. Obtain existing equipment data, one-lines, study
reports, plots, recorded data, etc.
3. Convert project files to ETAP via DataX
4. LF Data collection: NPs, settings, positions, etc.
5. Model Validation using network & operating info
6. Verifying all allowable limits, V, A, kVA, kW, time, etc.
7. Run 100s of studies
8. Verify acceptance using the LF Analyzer
9. Create Wizard for top most 10-50 studies that show
verification of the worst operating requirements.
10. Create the study report, using CR, OLV, PDF, Excel, …
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Methodology
Non-Linear System
• Calculation Process
 Iterative Calculation
 Assume Load Voltage “VR”
(Initial Conditions)
 Calculate the Current “I”
 Based on Current
Calculate Voltage Drop “Vd”
Assume VR
Calc: I = Sload / VR
Calc: Vd = I * Z
Re-Calc VR = Vs - Vd
 Re-Calculate Load Voltage “VR”
 Re-use “VR” until results are within the specified precision
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Methodology
• Load Flow Calculation Methods
 Newton-Raphson
 Fast in speed, but high requirement on initial values
 First order derivative is used to speed up calculation
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Methodology
• Load Flow Calculation Methods
 Adaptive Newton-Raphson
 Fast in speed, but high requirement on initial values
 First order derivative is used to speed up calculation
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Methodology
• Load Flow Calculation Methods
 Accelerated Gauss-Seidel Method
 Low Requirements on initial values
 Slow in speed
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Methodology
• Load Flow Calculation Methods
 Fast-Decoupled Method
 Two sets of iteration equations: real power – voltage angle,
reactive power – voltage magnitude in speed, but high
requirement on initial values
 Fast in speed, but low in solution precision
 Better for radial systems and systems with long lines
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Methodology
• Possible Convergence Issues
 Negative Impedance
 Zero or Very Small Impedance
 Widely Different Branch Impedance Values
 Long Radial System Configurations
 Improper Initial Bus Voltage Values
 Imbalance of demand/supply in the system
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Load Flow Requirements
• ETAP load flow required data
 General Equipment Data
 Element ID
 Nominal / Rated kV
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Load Flow Requirements
• ETAP load flow required data
 Bus:
 %V and Angle
 Load Diversity Factor
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Load Flow Requirements
• ETAP load flow required data
 Branch in general:
 Branch Z, R, X, or X/R values and units, tolerance, and
temperature, if applicable
 Cable and transmission line, length, and unit
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Load Flow Requirements
• ETAP load flow required data
 Branch in general:
 Branch Z, R, X, or X/R values and units, tolerance, and
temperature, if applicable
 Transformer rated kV and kVA/MVA, tap, and LTC settings
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Load Flow Requirements
• ETAP load flow required data
 Branch in general:
 Branch Z, R, X, or X/R values and units, tolerance, and
temperature, if applicable
 Impedance element base kV and base kVA/MVA
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Exercise
Example-B1
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Exercise
Purpose & Description
• The purpose of this exercise is to introduce the
equipment editor fields for the load flow calculation.
• The Load Flow required data for different elements
are introduced.
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Methodology
Load Type Summary
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Load Types in Power System
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Load Types in Power System
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Load Modeling in ETAP
• Constant Power (kVA) Loads
• Motor loads,
 Constant Power output regardless of voltage
variations - P = T * Rotor Speed
 Induction Motor
 Synchronous Motors
 Lumped Load – Option
• Combination of constant power, current, &
impedance loads with frequency dependencies
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Load Modeling in ETAP
• Example:
 Motor Nameplate Calculation
kWRated
HP  0.7457

PF  Eff
PF  Eff
kVARated
FLA3 
3  kV
kVARated
FLA1 
kV
kVARated 
Mtr 2 : PF  90 %, EFF  85 %
200  0.7457
 194 .95
0.9  0.85
194 .95

 234 .48
3  0.48
194 .95

 406 .14
0.48
k VARated 
FLA3
FLA1
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Load Modeling in ETAP
• Constant Impedance Loads





Static Load
Motor Operated Valve
Lumped Load
Capacitor
Harmonic Filter
• Power & Voltage relation: P  V 2
• In Load Flow Harmonic Filters may be used as capacitive
loads for Power Factor Correction.
• MOVs are modeled as constant impedance loads
because of their operating characteristics.
Load Flow Analysis
© 1996-2008 Operation Technology, Inc. – Workshop Notes: Load Flow Analysis
Slide 44
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Load Modeling in ETAP
• Example (Cont’d):
 Load Calculation
k VA 
( k W ) 2  ( k Var) 2
kW
k VA
k VA

( 3  kV)
k VA

kV
PF 
I 3
I1
Load1 : PF  90 %, kVA  280
kW  59 .6  0.9  252
kVar 
(59 .6) 2  (53 .64 ) 2  122
59 .6
 336 .8
3  0.48
59 .6
I1 
 194 .68
0.48
Load Flow Analysis
I 3 
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Load Modeling in ETAP
• Constant Current Loads
 Current remains constant regardless of
voltage variations
 DC Constant current loads are used to test
Battery discharge capacity
 AC constant current loads may be used to
test UPS systems performance
 DC Constant Current Loads may be
specified in ETAP by defining Load Duty
Cycles
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Load Modeling in ETAP
• Constant Current Loads (Cont’d):
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Exercise
Example-B2
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Exercise
•
•
•
•
Purpose & Description
The purpose of this exercise is to introduce features
such as alert views, load flow reports and load flow
analyzer.
Check voltage and loading conditions.
Voltage regulation
Element sizing
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Loading & Generation
Overview
 Generator Operation Modes
 Renewable Energy
 Motor Operation
 Generic Loads
 Invertors & Chargers
 UPS
 Equipment Limits
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Generator Operation Modes
• Synchronous Generator & Control System
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Generator Operation Modes
• Governor Operating Modes
 Isochronous:
 This governor setting allows the generator’s power output to be
adjusted based on the system demand
 Frequency (speed) is constant per system’s nominal frequency
 Droop:
 This governor setting allows the generator to be Base Loaded, meaning
that the MW output is fixed at
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Generator Operation Modes
• Generator Excitation System
 AVR: automatic voltage regulation
 Feedback voltage from generator terminal
 Comparison of feedback to reference
voltage in AVR unit
 Fixed: fixed excitation (no AVR)
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Generator Operation Modes
• Isochronous Mode
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Generator Operation Modes
• Droop Mode
Loading
@60Hz
Governor
Set Point
0%
A
25%
B
50%
C
75%
D
100%
E
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Generator Operation Modes
• Droop Mode – Equal Settings
 60Hz and constant loading of
400MW
 Equal load sharing
G1 = G2 = 200MW
• Droop Mode – Unequal Settings
 Increase G1 governor setting by
0.3Hz
 G2 governor setting must
decrease by 0.3Hz
 Unequal load sharing
G1 = 150 MW; G2 = 250MW
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Generator Operation Modes
• Unequal Speed Droops
 Initial operating frequency at
60Hz
 Initial loading G1 = G2 = 350MW
• Effect of load variations
 Total increase of load by
350MW
 Frequency drop by 0.5Hz
 Unequal load sharing
G1 = 600MW; G2 = 450MW
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Generator Modes in ETAP
• Generator/Power Grid operating modes used in LF calculation

Swing Mode
 Governor in Isochronous mode
 Automatic Voltage Regulator

Voltage Control
 Governor in Droop Mode
 Automatic Voltage Regulator

Mvar Control
 Governor in Droop Mode
 Fixed Field Excitation (no AVR action)

PF Control
 Governor in Droop Mode
 AVR Adjusts to Power Factor Setting
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Generator Modes in ETAP
• If in Voltage Control Mode, the limits of P & Q are
reached, the model is changed to a constant P & Q
load
Generator Characteristics
Operating
Modes
Exciter
Governor
P
Q
V
δ°
Swing
X
X
√
√
AVR
Isoch
Voltage
Control
√
X
√
X
AVR
Droop
Mvar (PF)
Control
√
√
X
X
Fixed
Droop
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Load Modeling
• Generic Loads
 Exponential Load
 Polynomial Load
 Comprehensive Load
Ppoly  p1V
2
p2 V


p3
a1
Pexp 1  p4 (V ) (1  K pf 1f )
Pexp 2  p5 (V )
a2
(1  K pf 2 f )
P  P0 [ Ppoly  Pexp 1  Pexp 2 ]
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Load Modeling
• Lumped Load Negative Loading
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Generator Limits
• Generator Capability Curve
 Based on generator MVA rating
 Q>0 in lagging mode
 Q<0 in leading mode
 P>0 in generator mode
 P<0 in motoring mode
 Curve AB; Field Heating limit
 Curve BC; Stator Heating
 Curve CD; Stator Core End
Heating
 Point B; Rated Power Factor
 More limitation with no AVR
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Generator Modes in ETAP
• Generator Capability Curve (Cont’d):
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Example
IEEE Example
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Load Flow Toolbar
• Load Flow Toolbar buttons:












Run Load Flow
Auto Run on/off
Halt Current Calculation
Alert View
Report Manager
Load Flow Result Analyzer
Load Flow Comparator
Display Options
Unit Show
Result Options
Voltage Unit Option
Load Terminal Voltages
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Load Flow Study Case
• Study Case - Info Page:
 ID
 Method
 Select the mathematical
calculation method
 Report
 Select the display unit for
reporting
 Options
 Select the method for specifying
initial voltages
 Update
 Select certain fields to updated
as the result of load flow
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Load Flow Study Case
• Study Case - Loading Page:
 Loading Category
 Select specific category to be
considered for the calculation
 Generation Category
 Select specific category to be
considered for the calculation
 Load Diversity Factor
 Charger Loading
 Apply charger loading per
operating load or selected
loading category
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Load Flow Study Case
• Study Case - Adjustment
Page:
 Impedance Tolerance
 Apply positive tolerance for
transformer, reactor and/or
overload heater
 Length Tolerance
 Apply positive tolerance for
cable and/or transmission line
lengths
 Resistance temperature
Correction
 Apply Max. temperature for
cable and/or transmission line
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Load Flow Study Case
• Study Case – Alert Page:
 Loading
 Specify critical/marginal loading
% for alerting
 Bus Voltage
 Specify critical/marginal
over/under voltage limits
 Generator/Power Grid Excitation
 Specify critical/marginal
over/under excitation limits
 Auto Display
 Display alerts automatically
right after load flow run
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Load Flow Study Case
• Allowable Voltage Drop NEC and ANSI C84.1
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Load Flow Study Case
• Protective Device Alerts
Protective Devices
Monitored parameters %
Condition reported
Low Voltage Circuit Breaker
Continuous rated Current
OverLoad
High Voltage Circuit Breaker
Continuous rated Current
OverLoad
Fuses
Rated Current
OverLoad
Contactors
Continuous rated Current
OverLoad
SPDT / SPST switches
Continuous rated Current
OverLoad
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Load Flow Alerts
Load Flow Analysis
© 1996-2009 Operation Technology, Inc. – Workshop Notes: Load Flow Analysis
Slide 72
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Exercise
Example-B3
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Exercise
Purpose & Description
• The purpose of this exercise is to check the operating
limits of the elements
• Propose solutions for under-voltage conditions
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Reports
• ETAP Report Types:
One Line Diagram
Report Types
Remarks
Display (Annotation)
Power Flows
kW, kvar, Amp, PF, etc.
Flow Results
Branch, Source, Load, etc.
Branch Losses
kW + jkvar
Bus Voltage
Magnitude/Angle (kV, V, %)
Load Terminal
Load rated kV or Bus Nom. kV
Voltage Drop
Line, Cable, Load Feeder
UPS/Panel
Average values or per phase
Meters
Ammeter, Voltmeter, Multi-Meter
Text Box
Input Data
All input properties for all equipments
Datablock
Input/output
All the input and output results (future
release)
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Reports
• Example (Bus Voltage Display):
Bus4 voltage in Percent:
kVCalculated  13 .5
V% 
kVNo min al  13.8
kVCalculated
100  97 .83 %
kVNo min al
Bus5 voltage in percent:
kVCalculated  4.03
kVNo min al  4.16
kVCalculated
V% 
100  96 .85 %
kVNo min al
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Reports
• ETAP Report Types:
Report Manager
Report Types
Crystal Report
Remarks
Complete Including all input/output data
Input Only input data
Result Only output results
MS Excel
Ms Word
Summary Including alerts, losses, loading, etc.
PDF
Text
Report Analyzer
Report Types
Table (Grid) of multiple General
reports
Bus Results
Branch Results
Loads
Remarks
Comparison of multiple reports in a table
displaying input/output data based on
different equipment types, ratings, flow
results and specified alerts
(loading/voltage drop)
Sources
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Reports
• Report Manager:
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Reports
• Load Flow Analyzer:
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Reports
• Power Flow Convention:
Element Type
Source
Load
Load Flow Analysis
Active Power (P)
Reactive Power (Q)
Power Flow Convention
+
+
Supply P & Q
+
-
Supply P, Absorb Q
-
+
Absorb P, Supply Q
-
-
Absorb P & Q
+
+
Absorb P & Q
+
-
Absorb P, Supply Q
-
+
Supply P, Absorb Q
-
-
Supply P & Q
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Wizards
• Scenario:
 Create new scenarios / copy
existing scenarios
 Run scenario based on selected
parameters
• Scenario Parameters:
 System (Network, CSD, UGS)
 Presentation
 Revision
 Configuration
 Study Mode
 Study Type
 Study Case
 Output Report
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Wizards
• Study:
 Create new study macro / copy
existing study macros
 Run study macro based on the
order of selected scenarios
• Study Parameters:
 Add an existing scenario to end of
the list
 Insert an existing scenario in
between the list
 Reorder the scenario list
 Activate/deactivate certain
scenarios
 Create selective pause between
the scenario runs
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Wizards
• Project:
 Create new project macro / copy
existing project macros
 Run project macro based on the
order of selected study macros
• Project Parameters:
 Add an existing project macro to
end of the list
 Insert an existing project macro in
between the list
 Reorder the study macro list
 Activate/deactivate certain studies
 Create selective pause between
the study macro runs
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Panel Systems
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Panel System
Panel Boards:
• They are a collection of branch circuits feeding system
loads
• Panel System is used for representing power and
lighting panels in electrical systems
Click to drop once on OLV
Double-Click to drop multiple panels
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Panel System
• Representation:
A panel branch circuit load can be modeled as an internal or
external load
Advantages:
1. Easier Data Entry
2. Concise System
Representation
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Panel System
• Pin Assignment:
Pin 0 is the top pin of the panel
ETAP allows up to 24 external load connections
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Panel System
Assumptions:
• Vrated (internal load) = Vrated (Panel Voltage)
• Note that if a 1-Phase load is connected to a 3-Phase
panel circuit, the rated voltage of the panel circuit is
(1/√3) times the rated panel voltage
• The voltage of L1 or L2 phase in a 1-Phase 3-Wire panel
is (1/2) times the rated voltage of the panel
• There are no losses in the feeders connecting a load to
the panel
• Static loads are calculated based on their rated voltage
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Panel System
• Line to Line Connections
Load Connected Between Two Phases of a
3-Phase System
A
A
B
C
B
C
IB = IBC
IBC
Load
IC = -IBC
LoadB
Angle by which load current IBC lags the load voltage = θ
Therefore, for load connected between phases B and C:
For load connected to phase B
SBC = VBC.IBC
PBC = VBC.IBC.cos θ
QBC = VBC.IBC.sin θ
SB = VB.IB
PB = VB.IB.cos (θ - 30)
QB = VB.IB.sin (θ - 30)
And, for load connected to phase C
SC = VC.IC
PC = VC.IC.cos (θ + 30)
QC = VC.IC.sin (θ + 30)
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Panel System
• Info Page:
NEC Selection
A, B, C from top to bottom or
left to right from the front of the
panel
Phase B shall be the highest
voltage (LG) on a 3-phase, 4wire delta connected system
(midpoint grounded)
3-Phase 4-Wire Panel
3-Phase 3-Wire Panel
1-Phase 3-Wire Panel
1-Phase 2-Wire Panel
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Panel System
• Rating Page:
Intelligent kV Calculation
If a 1-Phase panel is connected to a 3-Phase bus
having a nominal voltage equal to 0.48 kV, the
default rated kV of the panel is set to (0.48/1.732
=) 0.277 kV
For IEC, Enclosure Type
is Ingress Protection
(IPxy), where IP00 means
no protection or shielding
on the panel
Select ANSI or IEC
Breakers or Fuses from
Main Device Library
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Panel System
• Schedule Page:
Circuit Numbers with
Standard Layout
Circuit Numbers with
Column Layout
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Panel System
• Pin Assignment:
₋ First 14 load items in the list are based on NEC 1999
₋ Last 10 load types in the Panel Code Factor Table are user-defined
₋ Load Type is used to determine the Code Factors used in calculating the total panel
load
₋ External loads are classified as motor load or static load according to the element
type
₋ For External links the load status is determined from the connected load’s demand
factor status
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Panel System
• Rating Tab:
Enter per phase VA, W, or
Amperes for this load.
For example, if total Watts
for a 3-phase load are 1200,
enter W as 400 (=1200/3)
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Panel System
• Loading Tab:
For internal loads, enter the % loading for the selected loading category
For both internal and external loads, Amp values are
calculated based on terminal bus nominal kV
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Panel System
• Protective Device Tab:
Library Quick Pick LV Circuit Breaker
(Molded Case, with
Thermal Magnetic Trip
Device) or
Library Quick Pick –
Fuse
will
appear
depending on the
Type of protective
device selected.
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Panel System
• Feeder Tab:
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Panel System
• Action Bottons:
Copy the content of the selected
row to clipboard. Circuit number,
Phase, Pole, Load Name, Link
and State are not copied.
Paste the entire content (of the
copied row) in the selected row.
This will work when the Link
Type is other than space or
unusable, and only for fields
which are not blocked.
Blank out the contents of the entire
selected row.
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Panel System
• Summary Page:
Continuous Load – Per Phase and Total
Non-Continuous Load – Per Phase and Total
Connected Load – Per Phase and Total (Continuous + Non-Continuous Load)
Code Demand – Per Phase and Total
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Panel System
• Output Report
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Panel System
• Panel Code Factors
The first fourteen have fixed formats per NEC 1999
Code demand load depends on Panel Code Factors
Code demand load calculation for internal loads are done
for each types of load separately and then summed up
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Advanced LF Topics
Load Flow Convergence
Load Flow vs. Optimal Power Flow
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Advanced Topics
• Review of Load Flow Study
– Given generation, loading and control settings (Mwgen, Vgen, LTC,
Capacitor Bank, …)
– Solve bus voltages and branch flows
– Check over/under voltage, device overloading conditions
– Reset controls and run Load Flow again
– Iterative process
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Advanced Topics
• Optimal Load Flow Approach
– Given control setting ranges
– Specify bus voltage and branch loading constraints
– Select optimization objectives (Min. P Losses, Min. Q Losses, …)
– Solve bus voltages, branch flows and control settings
– Direct solution
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Advanced Topics
• Control Variables
–
–
–
–
–
–
–
–
Load Tap Changer (LTC) Settings
Generator AVR Settings
Generator MW Generation
Series or Shunt VAR Compensator Settings
Phase Shift Transformer Tap Positions
Switched Capacitor Settings
Load Shedding
DC Line Flow
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Advanced Topics
Objective Function:
• Minimize Real Power Losses
- To minimize real power losses in the system
• Minimize Reactive Power Losses
- To minimize reactive power losses in the system
• Minimize Swing Bus Power
- To minimize real power generation at the swing bus(s)
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Advanced Topics
• Minimize Shunt var Devices
- To minimize var generation from available shunt var control devices
• Minimize Fuel Cost
- To minimize total generation fuel cost
• Minimize Series Compensation
- To minimize var generation from available series var control devices
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Advanced Topics
• Minimize Load Shedding
- To minimize load to be shed from the available bus load shed schedule
• Minimize Control Movement
- To minimize total number of controls
• Minimize Control Adjustment
- To minimize overall adjustment from all controls
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Advanced Topics
• Maximize Voltage Security Index
Voltage Security Index 
 Vi  Vi ,avg 


 dVi 
AllBuses

i
2n
,
Where
Vi ,avg 
Load Flow Analysis
Vi ,max  Vi ,min
2
dVi 
Vi ,max  Vi ,min
2
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Advanced Topics
• Maximize Line Flow Security Index
Line Flow Security Index 
AllBranche
s

i
,
Where
dSi
 Si 
 
 Si 
2n
is the line rating
• Flat Voltage Profile
- Voltage Magnitude difference between all buses is minimum
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Advanced Topics
Constraints:
• Bus Voltage Constraints
• Branch Flow Constraints
• Interface Flow Constraints
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Exercise
• Open LF-Example-A3
• Follow instructions in LF-Example-A3.PDF
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved
Exercise
• Comparison of LF and OPF:
Load Flow Analysis
© 2017, ETAP/Operation Technology, Inc., All Rights Reserved