WindMil 101 - Engineering Analysis Software

WindMil 101
Bill Kersting
Distribution System Modeling and Analysis
•  Primary purposes of the first two editions.
–  Define terms used in defining “loads”.
–  Present approximate methods for voltage drop and power losses.
–  Develop models
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OH and UG lines
Step type voltage regulators
Some three-phase transformer connection models, including center tapped
Introduction to the Ladder Technique for power-flow analysis
Third Edition
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Complete models for all standard three-phase transformer connections with and without center tapped
transformers.
Add the use of WindMil.
–  Student version downloaded.
–  Homework problems that compare models developed by hand and the same model developed in
WindMil.
–  Major assignment at the end of the book to allow the students to run power-flow analysis on the small
test feeder and fix any problems.
•  Node voltages not within ANSI requirements.
–  Apply step voltage regulators.
–  Install shunt capacitors.
•  Add single-phase center tapped transformers with secondary to test feeder.
A tutorial has been developed for the students to use in developing an understanding how the component
models are applied and used in WindMil.
Problem 4.1 – Overhead Three-Phase Line
Set Spacing Matrix
Compute Primitive Impedance Matrix
Kron Reduction
Display Homework 4.1 and 5.1 Results
System 1
WindMil Assignment:
12.47 kV line-to-line source. The “Bus Voltage” should be set
to 120 Volts. Z+ = 8.4 + j21.4 Ohms, Z0 19.0 + j44.9 Ohms.
Connect to a node and call it Node 1
A 5000 ft. long overhead three distribution line as defined in
Problem 4.1 Call this line OH-1.
Connect a node to the end of the line and call it Node 2
A wye connected unbalanced three-phase load is connected to
Node 2 and is modeled as constant PQ load with values of:
Phase a-g: 1000 kVA, Power factor = 90 % lagging
Phase b-g: 800 kVA, Power factor = 85 % lagging
Phase c-g: 1200 kVA, Power factor = 95 % lagging
Determine the voltages on a 120 volt base at Node 2 and the
current flowing on the OH-1 line
Start WindMil and Click File/New
Click on EQDB/Use Different Equipment
Define Location of Data Base
Click Preferences/System Preferences
Click on Modeling and Select 50 C
Click on View/Display Options
Click on General and Select One Line Diagram
and Schematic Symbols
Define Size of Symbols
Start System 1 by Selecting Add Source
Click on the source icon and then on navigate
Click on New and Input Source Data
Define Source Voltages
Connect Node 1 to the Source
Connect an OH Line to Node 1
Input Necessary Data as Shown
Select the Desired Conductor from the ACSR List
Define Line Construction Spacings
Give the Construction a Name
Select Conductor Distances
Input xy Coordinates for Phase and Neutral Conductors
don’t Click on Assume Full Transposition
Define the Phasing
Connect Node 2 to the End of the OH Line
Click on Node 2 to Start Defining the Loads
Click New and type in equipment name
Set the Y-PQ load as shown
Input the Load kW and kvar Values
Before Running Select Voltage Drop/Settings and Don’t
Click Assume Transposition. Click apply and run.
Use Calculated Data Box to Display Node Voltage
Node 2 Voltages on 120 Volt Base
Create a User Defined box
Click on New to create a new user defined box
Name the template. Browse though the fields to select Thru Amps. Drag Thru
Amps over to the Selected Variables box.
Click on Thru Amps. In Display in select Polar, In Units select
Amps or Volts. Click on OK.
Displayed will be the template name and the current values for the
OH line. Click OK to return to the diagram.
Data Box for line currents displayed
Double click on OH 1 and then editor. Click on Impedance to
display the Z and Y matrices for the line.
Summary
System 2
Problem 4.3
System 2
Results for System 2
System 3
Concentric Neutral Data
Create the Concentric Neutral Cable
Define Construction for Two Phase UG
Connect Node 4 to the End of the UG Line
Define the Constant Current Delta Load
Display Results
Node 4 Line-to-Line Voltage
System 4
The regulator needs to be placed between the source and Node 1. To do this click on the
x as shown with line 1 below. Then click on the regulator. This sets up the installation
of the regulator after the source.
Click on the source and hold the left key down and drag down and to the right to install
the regulator between the source and Node 1.
Double click on the regulator. Change the name to Reg 1. Also rotate the phases so that
ACB is the phasing.
Set the Voltage Level to 122 Volts. Select “1-Ph with all phases the same”. Click in the
Regulator Size Definition box.
Click on New and type in the name for the single-phase regulator.
Type in the CT Rating, Amps Rating, % Boost and the Total Bandwidth. Click OK.
Notice that the 7200 Volt, 1 phase regulator is in the Regulator Equipment List.
Click in the box shown and click on Set Regulation. This is the first step in having
WindMil compute the required R and X settings for the compensator.
After selecting “Set Regulation” click on the regulator and then click the Analysis icon
on the menu bar and then click on Analysis Manager.
The window will appear as shown below. If the Regulator Name is blank click on “Add
All Regulators” and Reg 1 will be shown. Click on the arrow in the Load Center box to
display possible Load Center locations. Select Node 2. Click on Regulator Limit
Settings.
After clicking on Regulator Limit Settings verify that the Most Desirable Voltage is set to
122 volts and “Unbalanced” is clicked. Also make sure that the R and X maximum
settings are not zero. Click on LDC Rules.
After clicking on LDC Rules this window appears. Click on “Use Line Drop
Compensation” and the button “Hold Load Center at Most Desirable Voltage”. Click on
Apply & Run.
WindMil has computed the R and X settings that should hold the voltages at Node 2 to
between 121 and 123 volts.
Select “Voltage Drop” and then the Analysis/Analysis Manager. Make sure that the
Regulator is set to “Step”. Click on Apply & Run.
The Voltage Drop analysis has been performed. To display the regulator taps a new user
defined box needs to be created. Click on Reg 1 the User-defined Data Box and then on
Define.
Click on New, type in the Template Name. Scroll down the list until “Regulator
Equipment” is found. Drag this over to the Selected Variables box. Click on OK.
To specify the tap settings click on Edit Template.
Scroll down the Field list until Regulator Num Steps is found. Drag over for phase A, B
and C. Change the name of the user defined box to “Reg Taps”. Click on OK.
After running voltage drop select Reg 1 to display the user defined data box Reg Taps. It
is also good to use the Calculated Data Box at Node 2 to demonstrate that the voltages
are within the range 121 to 123 volts.
To compute the R and X settings by hand it is necessary to run Voltage Drop for a
balanced run with lines transposed. Open Analysis Options and click on Assume
Transposition and click None on Regulators.
Click on Analysis Settings and click the Balanced button. Click Apply & Run.
Use the user defined boxes to display the actual voltages at Nodes 1 and 2 and the actual
current in the line. Note that the voltages and currents are balanced so the line Z needs
to only be calculated for phase a.
Compensator Settings
•  WindMil using Set Regulation: Z = 1.6 + j5.1 Volts
•  Mathcad computation: Z: 1.5 + j4.7 Volts
•  The two values are very close. WindMil uses a slightly different method to
compute the required compensator R and X settings.
Summary Systems 2,3 and 4
•  A single-phase OH line was added to System 1 to created System 2.
•  An underground concentric neutral cable was created and used to create a
two phase UG line to add to System 2 to create System 3.
•  The steps to install a three-phase Y-Y connected step regulator bank was
demonstrated. This was added to System 3 to created System 4.
•  The necessary steps to have WindMil compute the needed compensator R
and X settings was demonstrated.
•  WindMil was run with the regulators holding the Node 2 voltages within
the desired voltage limits.
•  The steps to compute the R and X compensator settings were demonstrated.
System 5 Assignment. As before, save System 4 as System 5.
•  WindMil Assignment
•  Use System 4 to build this new System 5. A 5,000 kVA delta-grounded
wye substation transformer is to be connected between the source and Reg
1. The voltages for the transformer are 115 kV delta to 12.47 kV grounded
wye. The impedance of this transformer is 8.06 % with an X/R ratio 8. By
installing this substation transformer be sure to modify the source so that it
is 115,000 V rather than the 12.47 V. Follow the steps in the User’s
Manual on how to install the substation transformer.
•  When the transformer has been connected run Voltage Drop.
•  What are the node voltages at Node 2?
•  What taps has the regulator gone to?
•  Why did the taps increase when the transformer was added to the system?
System 5 requires that the substation transformer be connected between the source and
the regulator. In order to make room for this addition a feature in WindMil will be
demonstrated. Click on the black arrow in the toolbar and then click and hold on Node 1
and drag it to the right.
Moving Node 1 will produce this display. Repeat the process to move Reg 1 up and to the
right.
Moving Reg 1 leaves room to install the substation transformer and an additional
node. The names on the elements can be moved by clicking on the name and then
dragging it to the desired position.
Follow the same procedures as before to add the substation transformer. Connect a node
between the transformer and the regulator.
Double click on the transformer symbol and select D-Y Grd as the connection. Type in
115000 for the Rated Input Voltage and 12470 for the Rated and Nominal Voltages.
Click on the box next to Phase A to define the transformer.
Click on New and type in the name of the transformer.
Select “Three Phase Transformer” from the drop down list. Type in the impedance and
kVA values.
Double click on the source symbol in order to create the required 115,000 kV source.
Click on the Impedance Code box.
Click on New and type in the Name of new equipment. Click OK.
Even though the 115 kV system equivalent impedances are not needed for the voltage
drop studies they can be entered at this time and will be used in short circuit studies.
Click on Impedance Code Max and select the 115,000 kV source. Change the name of
the source. Type in the 115000 as the nominal L-L voltage. The computer will calculate
the Nominal L-G voltage. Click Close and run Voltage Drop.
The results show that the Node 2 voltages are still within the limits of the 122 desired
voltages. Note that the regulator taps have changed after the substation transformer was
added.
Assignment 6. As before, save System 5 as System 6. Note in the assignment below that
the impedance of the 15 kVA transformer has been changed to a more realistic value
than that given in the book.
Click on the transformer symbol and connect to Node 2. Double click on the transformer
connected to Node 2. Click on the box for Phase A of Impedance Definition.
Click on New and type in the name of the transformer.
Select Single Phase Transformer from the drop down list. Type in the impedance and
rating of the transformer. Click OK.
Change the name of the transformer. Type in 240 volts as the rated and nominal output
voltages. Click Close.
Connect Node 5 to the Mt. Transformer.
Connect a motor to Node 5 by clicking on the motor symbol in the menu bar and then
click on Node 5 and drag out a little ways.
Double click on the motor. Type in Total Motor HP to be 25. Click on “Advanced
Model”. Change the name and input the Total Motor HP. Type in the Rated LL Volts
and click on the box next to Motor Conductor.
Click on New and name the motor. Click OK.
Set the current capacity to 60 amps. Click the Motor Impedance box, click the Ohms
button and then input the stator, rotor and shunt impedances. Click OK.
Click on Fixed Slip. Input the specified slip and select Running from the Motor drop
down list.
Run voltage drop. The results are shown below. The kW and kvar flow on the motor is
displayed using the PQ Flow user defined data box.
Summary
•  It was shown how to “move” elements on the circuit.
•  A substation delta-grounded wye transformer was connected between the
source and the voltage regulator.
•  A distribution ungrounded wye-delta three phase balanced transformer
bank was installed.
•  A three-phase induction motor was installed using the advanced model and
a fixed value of slip. The Load kW is computed.
–  If a fixed Load kW is specified, the operating slip is computed.
–  If you input a negative slip, the induction machine becomes a
generator.
System 7
All of the necessary data is given
Source Node
1
2
abc
3
3'
c
a
b
4
abc
8
c
9
7
c
a
b
c
a
12
4'
a
10
5
13
a
6
11
Assignment 7
Assignment 8
Assignment 8 (cont.)
Wrap Up
•  Step-by-step for the creation of simple systems.
•  Demonstrate methods to display results.
•  Add a step voltage regulator bank and demonstrate WindMil
and hand method for computing the R and X settings.
•  Add a 115kV source system with substation transformer.
•  Finally
–  Create a 13 node system.
–  Solve a variety of problems.