ETAP - Load flow and panel rev2014-1

© 2013 ETAP. PROPRIETARY, UNPUBLISHED, & CONFIDENTIAL
Load Flow Analysis
January 2014

Outline
• Load Flow Concept
• Load Flow Requirements
• Load Types in Power System
• Load Modeling in ETAP
• Generator Operation Modes
• Generation Modes in ETAP
• Load Flow Toolbar
• Load Flow Study Case
• Load Flow Analyzer
• Reports
• Wizards
• Panel System

Load Flow Concept
• Load Flow Concept
• Reports
• Wizards
• Panel System

Load Flow Concept
• Load Flow Objectives
 Determine Steady State Operating Conditions
 Size Equipments
 Verify operation conditions based on limits
 Validation of data in steady state condition

Load Flow Concept
• Determine Steady State Operating Conditions
 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

Load Flow Concept
• Size Equipments & Determine Parameters
 Cable
 Capacitor
 Transformer MVA Capacity
 Transformer Tap Setting
 Current Limiting Reactor Ratings
 MCC & Switchgear Current Ratings
 Generator Operating Mode (Isochronous / Droop)
 Generator’s Mvar Demand
 Transmission, Distribution & Utilization kV

Load Flow Concept
• 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

Load Flow Concept
• Validation of data in steady state condition
 Comparison of real time metered data with load flow results

Load Flow Concept
• Load Flow Problem
 Given:
 Power consumption at all buses
 Branch impedances in the network
 Network Topology (Configuration)
 Power production for each generator
 Output:
 Voltage magnitude and angle at all buses
 Power flows on all the branches including power factors
 Losses on all branches

• Non-Linear System
• Calculation Process
 Iterative Calculation
 Assume Load Voltage “VR”
(Initial Conditions)
 Calculate the Current “I”
 Based on Current
Calculate Voltage Drop “Vd”
 Re-Calculate Load Voltage “VR”
 Re-use “VR” until results are within the specified precision
Assume VR
Calc: I = Sload / VR
Calc: Vd = I * Z
Re-Calc VR = Vs - Vd
Load Flow Concept

• 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 Concept

 Adaptive Newton-Raphson
 Fast in speed, but high requirement on initial values
 First order derivative is used to speed up calculation
Load Flow Concept

 Accelerated Gauss-Seidel Method
 Low Requirements on initial values
 Slow in speed
Load Flow Concept

 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 Concept

Load Flow Concept
• Power in Balanced 3-Phase Systems
 Inductive loads have lagging Power Factors.
 Capacitive loads have leading Power Factors.
jQP
IV
SS
IVS
LL
LN




*
13
*
1
3
3 

Lagging Power Factor Leading Power Factor Current and Voltage

• Leading & Lagging Power Factors
 ETAP displays power factor in %
 Leading power factor as negative
 Lagging power factor as positive
Leading
Power
Factor
Lagging
Power
Factor
P - jQ P + jQ
Load Flow Concept

• 3-Phase Per Unit System
 Three phase power equation
 Base calculations
 Per unit calculations
B
2
B
B
B
B
B
MVA
)kV(
Z
kV3
kVA
I


B
actual
pu
B
actual
pu
Z
Z
Z
I
I
I


B
actual
pu
B
actual
pu
S
S
S
V
V
V












ZIV
VIS
3
3
Load Flow Concept












 o
B
n
B
n
B
o
Bo
pu
n
pu
S
S
V
V
ZZ
2

• In ETAP:
 The base rating is SB = 100 MVA
 Base voltage at any point of the system is determined in respect
to the turn ratios of transformers
 To determine base voltage:
 Impedance of transformer in per unit:
Load Flow Concept
2
2
11
BB kV
N
N
kV 
1
BkV
2
BkV
2
pu
pu
R
X
1
R
X
Z
X
















R
X
x
R
pu
pu

• 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 Concept

• Example (cont’d):
 Impedance conversion to 11 MVA base
 “n” stands for new & “O” stands for old values
 The base voltage of the branch impedance (Z1) determined by
transformer turn ratio
06478.0
)14.12(1
)14.12(065.0
X
2pu 

 005336.0
14.12
06478.0
Rpu 
)3538.11115.0(
5
100
5.13
8.13
)06478.01033.5(
2
3
2
jj
S
S
V
V
ZZ o
B
n
B
n
B
o
Bo
pu
n
pu 























 
38.135j15.11Z100Z% pu 
0695.4
31.3
5.13
2N
1N
kV
V
utility
B 




 165608.0
100
)0695.4(
MVA
V
Z
22
B
B 
Load Flow Concept

8.603j38.60Z100Z% pu 
)0382.6j6038.0(
1656.0
)1j1.0(
Z
Z
Z
B
actual
pu 


Load Flow Concept
• Example (cont’d) :
 Load flow report generated by ETAP for branches:

Load Flow Concept
• Exercise-A1

Load Flow Requirements
• Load Flow Overview
• Reports
• Wizards
• Panel System

Load Flow Requirements
• ETAP load flow required data
 General Equipment Data
 Element ID
 Nominal / Rated kV
 Bus:
 %V and Angle
 Load Diversity Factor
 Branch:
 Branch Z, R, X, or X/R values and units, tolerance, and
temperature, if applicable
 Cable and transmission line, length, and unit
 Transformer rated kV and kVA/MVA, tap, and LTC settings
 Impedance base kV and base kVA/MVA

Load Types in Power System
• Reports
• Wizards
• Panel System

Load Types in Power System

Load Modeling in ETAP
• Reports
• Wizards
• Panel System

• Constant Power (kVA) Loads
 Induction Motor
 Synchronous Motors
 Lumped Load
• Power output remains constant regardless of
voltage variations
• Lumped loads are combination of constant
power & constant impedance loads

• Constant Impedance Loads
 Static Load
 Motor Operated Valve
 Lumped Load
 Capacitor
 Harmonic Filter
• Power & Voltage relation:
• 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.
© 1996-2008 Operation Technology, Inc. – Workshop Notes: Load Flow Analysis Slide 31
2
VP 

kV
kVA
FLA
kV
kVA
FLA
EffPF
HP
EffPF
kW
kVA
Rated
Rated
Rated
Rated










1
3
3
7457.0
14.406
48.0
95.194
48.234
48.03
95.194
95.194
85.09.0
7457.0200
%85%,90:2
1
3











FLA
FLA
kVA
EFFPFMtr
Rated
• Example:
 Motor Nameplate Calculation

kV
kVA
I
kV
kVA
I
kVA
kW
PF
kVarkWkVA







1
3
22
)3(
)()(
• Example (Cont’d):
 Load Calculation
16.124
48.0
6.59
69.71
48.03
6.59
97.25)64.53()6.59(
64.539.06.59
6.59%,90:1
1
3
22









I
I
kVar
kW
kVAPFLoad

• 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

• Constant Current Loads (Cont’d):

• Load Type Summary

 Exponential Load
 Polynomial Load
 Comprehensive Load
• Generic Loads

Generator Operation Modes
• Reports
• Wizards
• Panel System

• Synchronous Generator & Control System

• 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)

• 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

• Isochronous Mode

• Droop Mode
Loading
@60Hz
Governor
Set Point
0% A
25% B
50% C
75% D
100% E

• 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

• 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

Generator Modes in ETAP
• Reports
• Wizards
• Panel System

 Swing Mode
 Governor in Isochronous mode
 Automatic Voltage Regulator
 Voltage Control
 Governor in Droop Mode
 Automatic Voltage Regulator
 Mvar Control
 Fixed Field Excitation (no AVR action)
 PF Control
 AVR Adjusts to Power Factor Setting
• Generator/Power Grid operating modes used in LF calculation

• If in Voltage Control Mode, the limits of P & Q are
reached, the model is changed to a constant P & Q
load
Operating
Modes
Generator Characteristics
Exciter Governor
P Q V δ°
Swing X X √ √ AVR Isoch
Voltage
Control √ X √ X AVR Droop
Mvar (PF)
Control √ √ X X Fixed Droop

• Generator Capability
Curve
Q (Mvar)
P (MW)
Rated Operating
Point
S2=P2+Q2
A
B
D
C
Motoring Generating
Lagging
Leading
No AVR
Fast AVR

Field Winding Heating Limit
Armature Winding Heating Limit
Machine Rating (Power Factor Point)
Steady State Stability Curve
• Maximum and Minimum Reactive Power

• Adjusting Steam Flow & Excitation Current

Field Winding
Heating Limit
Machine Rating
(Power Factor Point)
Steady State Stability Curve
• Generator Capability Curve

• Generator Capability Curve
Load Flow Loading Page
10 Different Generation
Categories for Every
Generator or Power
Grid in the System

X
V
)*COS(
X
*VV
Q
)(*SIN
X
*VV
P
X
V
)(*COS
X
*VV
j)(*SIN
X
*VV
jQPI*VS
2
2
21
21
21
21
2
2
21
21
21
21























222
111
VV
VV


Power Flow

Example: Two voltage sources designated as V1 and V2 are
connected as shown. If V1= 100 /0° , V2 = 100 /30° and X = 0 +j5
determine the power flow in the system.
I
var536535.10X|I|
268j1000)68.2j10)(50j6.86(IV
268j1000)68.2j10(100IV
68.2j10I
5j
)50j6.86(0j100
X
VV
I
22
*
2
*
1
21









2
1
0
1
Real Power Flow
Reactive Power Flow
Power Flow
1
2
V E( )
X
sin   
V E( )
X
cos   
V
2
X

0  
The following graph shows the power flow from Machine M2. This
machine behaves as a generator supplying real power and
absorbing reactive power from machine M1.
S
e power does not seem
t. Both generators are
eactive power to the

Reports
• Reports
• Wizards
• Panel System

• Bus Voltage
ETAP displays bus voltage values in two ways
₋ kV value
₋ Percent of Nominal Bus kV
%83.97100%
5.13
min


alNo
Calculated
Calculated
kV
kV
V
kV 8.13min alNokV
%85.96100%
03.4
min


alNo
Calculated
Calculated
kV
kV
V
kV 16.4min alNokV
For Bus4:
For Bus5:
Reports

Reports

Reports
• Lump Load Negative Loading

• Open LF-Example-A1
• Follow instructions in LF-Example-A1.PDF
Exercise

Load Flow Study Case
• Reports
• Wizards
• Panel System

• Transformer Impedance
– Adjust transformer impedance based on possible length variation tolerance
• Reactor Impedance
– Adjust reactor impedance based on specified tolerance
• Overload Heater
– Adjust Overload Heater resistance based on specified tolerance
• Transmission Line Length
– Adjust Transmission Line Impedance based on possible length variation
tolerance
• Cable Length
– Adjust Cable Impedance based on possible length variation tolerance

Adjustments applied
•Individual
•Global
Temperature Correction
• Cable Resistance
• Transmission Line
Resistance

Allowable Voltage Drop
NEC and ANSI C84.1

• Load Flow Alerts

Bus Alerts Monitor Continuous Amps
Cable Monitor Continuous Amps
Reactor Monitor Continuous Amps
Line Monitor Line Ampacity
Transformer Monitor Maximum MVA Output
UPS/Panel Monitor Panel Continuous Amps
Generator Monitor Generator Rated MW
• Load Flow 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
• Protective Device Alerts

If the Auto Display feature is
active, the Alert View Window
will appear as soon as the
Load Flow calculation has
finished.
© 1996-2009 Operation Technology, Inc. – Workshop Notes: Load Flow Analysis Slide 69

• Open LF-Example-B1
• Follow instructions in LF-Example-B1.PDF
Exercise

• Load Flow Example B1
Part 1
© 1996-2009 Operation Technology, Inc. - Workshop Notes: Load Flow Analysis
Slide 71
Exercise

• Load Flow Example B1 Part 2
Exercise

• Under/Over Voltage Conditions must be fixed for proper
equipment operation and insulation ratings be met.
• Methods of Improving Voltage Conditions:
– Transformer Replacement
– Capacitor Addition
– Transformer Tap Adjustment
Exercise

• Create Under Voltage
Condition
– Change Syn2 Quantity to 6.
(Info Page, Quantity Field)
– Run LF
– Bus8 Turns Magenta (Under
Voltage Condition)
• Method 1 - Change Xfmr
– Change T4 from 3 MVA to 8
MVA, will notice slight
improvement on the Bus8 kV
– Too Expensive and time
consuming
• Method 2 - Shunt Capacitor
– Add Shunt Capacitor to Bus8
– 300 kvar 3 Banks
– Voltage is improved
• Method 3 - Change Tap
– Place LTC on Primary of T6
– Select Bus8 for Control Bus
– Select Update LTC in the Study
Case
– Run LF
– Bus Voltage Comes within
specified limits
Exercise

• Vars from Utility
– Add Switch to CAP1
– Open Switch
– Run LF
• Method 1 – Generator
– Change Generator from
Voltage Control to Mvar
Control
– Set Mvar Design Setting to 5
Mvars
• Method 2 – Add Capacitor
– Close Switch
– Run Load Flow
– Var Contribution from the
Utility reduces
• Method 3 – Xfmr MVA
– Change T1 Mva to 40 MVA
– Will notice decrease in the
contribution from the Utility
• MVAR Control
Exercise

• Negative Impedance
• Zero or Very Small Impedance
• Widely Different Branch Impedance Values
• Long Radial System Configurations
• Bad Bus Voltage Initial Values
• Load Flow Convergence
Exercise

Exercise

Advanced LF Topics
Voltage Control
Mvar Control
Load Flow Convergence
Load Flow vs. Optimal Power Flow

• 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
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
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
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)
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
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
Advanced Topics

• Maximize Voltage Security Index
Where,
 




 

AllBuses
i
n
i
avgii
dV
VV
2
,
IndexSecurityVoltage
2
min,max,
,
ii
avgi
VV
V


2
min,max, ii
i
VV
dV


Advanced Topics

• Maximize Line Flow Security Index
Where, is the line rating
• Flat Voltage Profile
- Voltage Magnitude difference between all buses is minimum
 






sAllBranche
i
n
i
i
S
S
2
IndexSecurityFlowLine
iSd
Advanced Topics

Constraints:
• Bus Voltage Constraints
• Branch Flow Constraints
• Interface Flow Constraints
Advanced Topics

Exercise

Exercise
• Comparison of LF and OPF:

Panel System
• Reports
• Wizards
• Panel System

Panel Systems

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
Panel System

A panel branch circuit load can be modeled as an internal or
external load
Advantages:
1. Easier Data Entry
2. Concise System
Representation
Panel System
• Representation:

Pin 0 is the top pin of the panel
ETAP allows up to 24 external load connections
• Pin Assignment:
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
Panel System

Load Connected Between Two Phases of a
3-Phase System
A
B
C
Load
IBC
IC = -IBC
A
B
C
LoadB
IB = IBC
Angle by which load current IBC lags the load voltage = θ
Therefore, for load connected between phases B and C:
SBC = VBC.IBC
PBC = VBC.IBC.cos θ
QBC = VBC.IBC.sin θ
For load connected to phase B
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)
Panel System
• Line to Line Connections

3-Phase 4-Wire Panel
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, 4-
wire delta connected system
(midpoint grounded)
• Info Page:
Panel System

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
• Rating Page:
Panel System

Circuit Numbers with
Column Layout
Circuit Numbers with
Standard Layout
• Schedule Page:
Panel System

₋ 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
• Pin Assignment:
Panel System

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)
• Rating Tab:
Panel System

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
• Loading Tab:
Panel System

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.
• Protective Device Tab:
Panel System

• Feeder Tab:
Panel System

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.
• Action Bottons:
Panel System

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
• Summary Page:
Panel System

• Output Report
Panel System

Code demand load depends on Panel Code Factors
The first fourteen have fixed formats per NEC 1999
Code demand load calculation for internal loads are done
for each types of load separately and then summed up
• Panel Code Factors
Panel System

ETAP - Load flow and panel rev2014-1

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to ETAP - Load flow and panel rev2014-1

Similar to ETAP - Load flow and panel rev2014-1 (20)

Recently uploaded

Recently uploaded (20)

ETAP - Load flow and panel rev2014-1