PowerWorld Simulator version 11. Manual

Solving and Simulating a Case

Calculate MW-Distance

Simulator can estimate MW * Distance quantities for the system’s areas and z ones that result from a specified

transaction. Given a transaction from a specified source to a specified sink, Simulator uses power transfer distribution

factors (PTDFs) to estimate the change in flow for each line in the system that results from the transaction. For each

line, multiplying the line’s change in flow by its length then gives the MW * Distance index for that line. Simulator then

sums the MW * Distance indices by area and by zone to obtain the total MW * Distance for each area and zone in

response to the specified transaction.

Because the MW * Distance calculations use PTDFs, you must access the MW * Distance functionality from the PTDF

Dialog. Once you have calculated PTDFs for a particular transaction by pressing the Calculate PTDFs button, click

the Calculate MW * Distance button to bring up the MW * Distance Calculations Dialog.

The top portion of the MW * Distance Calculations Dialog is used to set the lengths of the lines in the case. Although

line length is represented as a data element in the power flow case, it often is left blank. However, Simulator needs

line length information if it is to calculate MW * Distance indices. Simulator offers a few options regarding the source

of line length information. If you do not have access to line lengths, either from the existing case or an external text

file, Simulator can estimate line lengths for you. It does this by using the Ohms/Length values you specify in the table

for lines of various kV. Simply indicate the voltage levels in the first row of the table, and the corresponding ohms or

reactance per length in the second column. You do not need to differentiate here between English and metric units,

because the calculation is independent of the measurement system. If you want the length estimates calculated using

this table to overwrite any line lengths that may already be present in the case, be sure to check the Always Estimate

Length checkbox; otherwise, the new estimates will set the lengths only of lines whose pre-defined length isn’t greater

than zero. If you want the estimates to populate the lengths of lines in the model so that, when you save the model,

the estimated lengths are saved as part of the model, check the Save Estimates With Case. (This provides a handy

way to set line lengths for a case that might not have any defined.) Note that, in performing these estimates,

transformers are defined as having zero length. If you do not want Simulator to estimate line lengths but instead want

to use the line lengths that are currently stored in memory, check the Do Not Use Length Estimates box. Finally, if

you want to load line lengths from a text file, click the Load Line Lengths from File button. This file can be either

comma- or space-delimited, and each line must have the following fields in the order specified:

From_Bus_Number

To_Bus_Number

Circuit_ID Length

Once Simulator knows how to calculate line lengths, it can calculate MW*distance indices for each area and zone.

Specify the amount of MW that will be transacted in the Size of Transaction textbox. You may use the arrows to

increase or decrease the size of the transaction. Simulator assumes that the transaction is to occur between the

source and sink groups for which you just calculated PTDFs. Press the button labeled Calculate to compute the

indices. Two tables are populated with the results of the calculation, one for areas, and another for zones. Use the

tabs to switch between the two tables. These tables are Case Information Displays and thus share charac teristics and

controls common to all case information displays. Thus, you can sort the tables, add or delete columns, access the

area and zone dialogs, print the tables, and save their content as HTML.

Several options can be set to customize the calculation of MW*Distance. These options are reached from the

MW*Distance Options Dialog.

473

MW-Distance Options

The calculation of MW*Distance quantities can be customized in a number of ways. These options are set from the

MW*Distance Options Dialog.

Include Tie Lines Only

If this box is checked, then the only branches that contribute to the MW*Distance calculation are those that tie two

areas together. Otherwise, both tie lines and lines internal to areas and zones are included in the calculation. In

the latter case, tie lines are assumed to belong to the area that owns the metered end of the branch.

Internal Flows

If you choose to include both tie line flows and flows internal to areas and zones in calculating MW*Distance

quantities, you have two options for how to treat internal flows. You can ignore flows resulting from the transaction

that flow in the reverse direction of the existing flow on a branch by checking the Include flow increases only

checkbox. You can also choose to treat all such counterflows as negative contributions to an area or zone’s MW *

Distance value by checking the Deduct flow reductions checkbox.

Omit Branches

To omit branches f or which the PTDF corresponding to the transaction is less than a specified value, specify a

nonzero percentage in this textbox.

474

Solving and Simulating a Case

Charts

Area Control Error (ACE) Chart

The ACE chart plots the area control error for an area over time. For details on ACE, please see topic Area Control.

To view this display, select Options > Charts > ACE Chart from the main menu in Run Mode, or press the

corresponding button on the Simulation Summary tab of the Area Information Dialog. If you use the main menu to

view this chart, it shows information for the it shows information for the first area in the case. The strip chart starts to

plot the data when you open it, with new data appearing on the left. You can change the scale of either the x -axis (the

time axis) or the y -axis (Scheduled Transactions axis) by right-clicking anywhere on the axis itself and specifying the

new axis limits and number of intervals.

Right-click on the display (except on the axes) to view the display’s local menu. The local menu is used to print the

strip chart, save the strip chart in a file, copy the strip chart to the Window’s clipboard, or change the number of the

area being displayed.

Use the display’s control-menu box to close the display (i.e. the ‘X’ button at the top right corner of the form).

475

Area Load and Generation Chart

The Load and Generation chart plots an area’s load + losses and generation in MW over time. To view this display,

select Options > Charts > Area Load and Generation Chart from the main menu in Run Mode, or press the

corresponding button on the Simulation Summary tab of the Area Information Dialog. If you use the main menu to view

this chart, it shows information for the it shows information for the first area in the case. The strip chart starts to chart

the data when you open it, with new data appearing on the left. You can change the scale of either the x -axis (the

time axis) or the y -axis (Load/Generation MW axis) by right-clicking anywhere on the axis itself and specifying the axis

limits and number of intervals.

Right-click on the display (except on the axes) to view the display’s local menu. The local menu is used to print the

strip chart, save the strip chart in a file, copy the strip chart to the Window’s clipboard, or change the number of the

area being displayed.

Use the display’s control-menu box to close the display (i.e. the ‘X’ button at the top right corner of the form).

476

Solving and Simulating a Case

Area Losses Chart

The Area Losses chart plots an area’s real power losses over time. To view this display, select Options > Charts >

Area Losses Chart from the main menu in Run Mode, or press the corresponding button on the Simulation Summary

tab of the Area Information Dialog. If you use the main menu to view this chart, it shows information for the it shows

information for the first area in the case. The strip chart starts to chart the data when you open it, with new data

appearing on the left. You can change the scale of either the x-axis (the time axis) or the y-axis (Load/Generation MW

axis) by right-clicking anywhere on the axis itself.

Right-click on the display (except on the axes) to view the display’s local menu. The local menu is used to print the

strip chart, save the strip chart in a file, copy the strip chart to the Window’s clipboard, or change the number of the

area being displayed.

Use the display’s control-menu box to close the display (i.e. the ‘X’ button at the top right corner of the form).

477

Area MW Transactions Chart

The Scheduled MW Transactions chart plots the scheduled real power (MW) transactions for an area over time. To

view this display, select Options > Charts > Area MW Transactions Chart from the main menu in Run Mode, or

press the corresponding button on the Simulation Summary tab of the Area Information Dialog. If you use the main

menu to view this chart, it shows information for the it shows information for the first area in the case. The strip chart

starts to chart the data when you open it, with new data appearing on the left. You can change the scale of either the

x-axis (the time axis) or the y-axis (Scheduled Transactions axis) by right-clicking anywhere on the axis itself and

specifying the new axis limits and number of intervals.

Right-click on the display (except on the axes) to view the display’s local menu. The local menu is used to print the

strip chart, save the strip chart in a file, copy the strip chart to the Window’s clipboard, or change the number of the

area being displayed.

Use the display’s control-menu box to close the display (i.e. the ‘X’ button at the top right corner of the form).

478

Solving and Simulating a Case

Area Average Cost Chart

The Average Cost per MWH chart plots the average cost per MWH for an area over time. This value is calculated by

dividing the total cost of operating the area (generation cost + purchased power cost - revenue from power sales) by

the MW load in the area. To view this display, select Options > Charts > Area Average Cost Chart from the main

menu in Run Mode, or press the corresponding button on the Simulation Summary tab of the area information dialog.

If you use the main menu to view this chart, it shows information for the first area in the case. The strip chart starts to

plot the data when you open it, with new data appearing on the left. You can change the scale of either the x -axis (the

time axis) or the y -axis (Scheduled Transactions axis) by right-clicking anywhere on the axis itself and specifying the

new axis limits and number of intervals. Note that as the area’s load increases, the average cost per MWH tends to

increase.

Right-click on the display (except on the axes) to view the display’s local menu. The local menu is used to print the

strip chart, save the strip chart in a file, copy the strip chart to the Window’s clipboard, or change the number of the

area being displayed.

Use the display’s control-menu box to close the display (i.e. the ‘X’ button at the top right corner of the form).

479

Bus View Oneline

Bus View Display

The Bus View Display feature serves as a graphical analog to the text-based Quick Power Flow List. Like the quick

power flow list, the bus view displays enable convenient bus-by-bus navigation through the power system. Moreover,

the bus view display contains much the same information as the items on the quick power flow display. From the bus

view, you can find out a bus’ voltage and angle, the load, shunt compensation, and generation connected to the bus,

and the flows on all lines emanating from the bus. You can also discover the bus’ area and zone affiliations, as well as

the bus’ marginal cost. Moreover, as with the quick power flow lists, you can find out all information about the

elements associated with the bus by directly invoking their associated information dialogs. The advantage of the bus

view displays, however, is that you interact with them in the same, familiar way you interact with oneline diagrams. In

other words, the bus view displays provide the content and maneuverability of the quick power flow lists with the ease

of use of the oneline diagrams.

Along the top of the bus view display resides a panel of controls. The buttons labeled Back and Ahead allow you to

step through the history of buses you have viewed thus far. The next two controls following the Bus label allow to

specify a bus name (in the first text box) or a bus number (in the second text box). If you type a number or name that

does not exist, the bus display will continue displaying the current bus. Following the bus specification fields are two

text boxes displaying the name and number of the bus’ associated area. These two fields are read-only.

Below this top panel sits the actual bus display. The bus you have chosen to inspect, which we shall refer to as the

target bus , is represented by a long, thick black horizontal line. Notice that the bus’ voltage in kV and per unit, its

angle, and its marginal cost are specified to the left of the bus. Any loads and generating loads connected to the

target bus are drawn above the bus symbol, along with their associated annotation. Emanating from the bottom of the

bus symbol are all transmission lines and transformers that connect the target bus to its neighbors. The transmission

line and transformer symbols are equipped with pie charts and annotation identifying flows as measured at the target

bus, as well as arrows to identify the direction of MW flow on the branch. Branches that serve as tie lines are drawn in

green for easy identification. Neighboring buses are represented as filled yellow rectangular regions, with symbol

indicators included if other types of devices, such as loads, generators, etc., are attached. When you drag the mouse

over one of these symbols, it turns into a pointing finger. Clicking the left mouse button when the mouse cursor is in

this shape redefines the target bus to be the bus whose symbol you just clicked. The bus view display is redrawn to

show the same sort of display for the newly chosen target. You can go back to the previously displayed target bus by

clicking the Back arrow, and then return to this record by clicking the Ahead arrow.

It is useful to think of the bus view displays as nothing more than an addition oneline diagram. In other words, you

interact with the objects drawn on the bus view display in the same way you work with objects on a more conventional

Simulator oneline. Right-clicking on any power system object will bring up that object’s local menu, which includes a

link to the object’s associated information dialog. As on a conventional oneline diagram, flows on a bus view display

can be animated. Right-clicking on the bus view display’s background will generate the same local menu as other

oneline diagrams. Again, the bus view display is the quick power flow list in the form of a oneline diagram.

The bus view display can be generated using any of the following methods:

· From the main menu, choose Case Information > Bus View . You will have to specify a bus name or number upon

entry.

· Right click on the bus of interest on the oneline diagram to display the bus’ local menu, and choose Bus View. The

bus view display will open with the selected bus already displayed.

· From any of the case information displays that convey bus information, right click on a record to bring up its local

menu, and choose Bus View Oneline. The bus view dis play will open with the corresponding bus already displayed.

· Click the corresponding toolbar icon on the Options/Info Toolbar.

To switch between the bus view and the main oneline, use the Window menu tree on the main menu. To close the

bus view display, simply close the form using the X button in the top right corner of the bus view display.

Bus View Options

Number of Tiers

The bus view can display one or two "tiers" of buses in the display. Use this selection from the Options menu to

toggle the number of tiers displayed.

Show Hints

When this option is checked, holding the cursor over an object will briefly pop up a hint box containing information

about that object.

Show Serial Buses

480

Solving and Simulating a Case

When putting in the branch connections, the Bus View display will look out into the network and find the next bus

which has more than two neighbors. It will then make this the destination bus for that branch of the Bus View. The

intermediate buses will then be shown in order above the destination branch. This option works especially well in

systems with a lot of multi-section lines.

Show Equivalent Lines

This option indicates to the Bus View display whether or not to include branches representing equivalent circuits as

connections in the display.

Default Drawing Values

Choosing this option will open the Default Drawing Values for New Objects dialog. Changing these options can

change some of the drawing aspects of the bus view, including device color and font size or color.

Open Multiple Bus Views

This option indicates whether to open multiple bus views simultaneously. Choices are never, always, and prompt

for confirmation when a new additional bus view is about to open.

Include Field Labels

Selecting this option will place labels for each displayed field on the bus view diagram.

Change Bus Link Color

Selecting this option will display the color palette to select the color with which the buses linked to the current bus

will be displayed.

Show Field Suffixes

This option specifies whether to display the field values units as suffixes. If this option is not selected, all the fields

will be display as a value without units.

Views

Define Custom View

The fields displayed on the bus view can be customized using this option. Clicking on this option will open a

customization settings display, in which you can add and remove field definitions for the objects on the bus view

display. Customized bus view layouts can be saved with the case for recall, identifiable by a custom bus view

layout name. Custom layouts can also be saved to a file for loading into another load flow case.

Input Data

Switching the bus view to Input Data changes the bus view from displaying system state information to displaying

input data information. For example, switching to Input Data view will display line impedances and limits, generator

minimum and maximum outputs, etc. The default Input Data view fields can be modified using the Define Custom

View customization dialog.

System State

Switching the bus view to System State changes the bus view from displaying Input Data information to displaying

system state information. This will result in line flows being displayed, voltage and angles displayed, etc., of the

current solution state of the system. The default System State view fields can be modified using the Define Custom

View customization dialog.

481

Substation View Oneline

Substation View Display

The Substation View Display feature is analogous to the Bus View Display.

Along the top of the substation view display resides a panel of controls. The buttons labeled Back and Ahead allow

you to step through the history of substations you have viewed thus far. The next two controls following the Substation

label allow to specify a substation name (in the first text box) or a number (in the second text box). If you type a

number or name that does not exist, the substation display will continue displaying the current substation.

Below this top panel sits the actual substation view display.

Just as with the bus view, it is useful to think of the substation view displays as nothing more than an addition oneline

diagram. In other words, you interact with the objects drawn on the substation view display in the same way you work

with objects on a more conventional Simulator oneline. Right-clicking on any power system object will bring up that

objects local menu, which includes a link to the object’s associated information dialog. As on a conventional oneline

diagram, flows on a substation view display can be animated. Right-clicking on the substation view display’s

background will generate the same local menu as other oneline diagrams. The substation view can be generated

using any of the following methods:

· From the main menu, choose Case Information > Substation View. You will have to specify a bus name or

number upon entry.

· Right click on a substation of interest on the oneline diagram to display the substations local menu, and choose

Substation View. The substation view display will open with the selected substation already displayed.

· From any of the Substation Records display, right click on a record to bring up its local menu, and choose

Substation View Oneline. The substation view display will open with the corresponding substation already

displayed.

· Click the corresponding toolbar icon on the Options/Info Toolbar.

To switch between the substation view and the main oneline, use the Window menu tree on the main menu. To close

the substation view display, simply close the form using the X button in the top right corner of the substation view

display.

482

General Tools

Generator Economic Curves

Generator Costs Curves Run Mode Tools

Four characteristic curves describe the efficiency and resulting costs associated with operating a particular generating

unit. These four curves plot

· Fuel Cost

· Heat Rate

· Input-Output

· Incremental Cost

Simulator can display plots of all these curves. To display a particular plot for a generator, right-click on the generator

in Run Mode to display its local menu, and then select the plot you wish to see. The plot will be presented in its own

window. The windows for all plots exhibit identical characteristics. For example, the current operating point is

identified by a red filled circle. Right clicking on an open area of the window displays the plot’s local menu which

allows you to print the plot, save it to a file, or copy it to the clipboard for use in other programs. To adjust the length

and number of intervals shown on an axis, right-click on the axis (not on the numbers) then specify the min and max

display values and number of intervals. To close a plot window, simply click the X button in its top right corner.

The Run Mode generator local menu also provides access to a fifth type of plot curve - the "All Area Gen IC Curves"

plot. This plot simply shows the incremental cost curves and present operating points of all generators in the same

area as the generator on which you clicked.

Fuel Cost Curve

The fuel cost curve specifies the cost of fuel used per hour by the generating unit as a function of the unit’s MW

output. This is a monotonically increasing convex function.

Heat-rate Curve

The heat rate curve plots the heat energy required per MWH of generated electrical output for the generator as a

function of the generator’s MW output. Thus, the heat rate curve indicates the efficiency of the unit over its

operating range. Generally, units are least efficient at the minimum and maximum portions of their MW output

capability and most efficient somewhere in the middle of their operating range. The vertical axis is plotted in

MBtu/MWH and the horizontal axis is plotted in MW. You may interpret the heat rate for a generator producing X

MW as follows: the heat rate indicates the amount of heat input energy per MWH of generation required to produce

X MW of power. The lower this number, the less input energy is required to produce each MWH of electricity.

Input-Output Curve

The input-output curve is derived simply from the heat-rate curve by multiplying it by the MW output of the unit. This

yields a curve showing the amount of heat input energy required per hour as a function of the generator’s output.

Incremental Cost Curve

By multiplying the input-output curve by the cost of the fuel in $/MBTU, one obtains the cost curve for the unit in

$/hr. By taking the derivative of the cost curve, one obtains the incremental cost curve, which indicates the

marginal cost of the unit: the cost of producing one more MW of power at that unit.

484

Run Mode Tools and Options

Find Branches that Create Islands

To find branches that create islands, while in Run Mode select Tools > Branches that Create Islands… from the

menu and the Find Branches that Create Islands Dialog will be displayed. This option is only available in Run Mode.

There are several options for selecting which ac lines to process.

Line Processing Options

All ac Lines

All ac lines in the power system model will be processed.

Use Area/Zone/Owner Filter

All ac lines that meet the defined Area/Zone/Owner Filters will be processed.

Select Area/Zone… to display the Area/Zone/Owner Filters dialog.

Use Selected

All ac lines that have the Selected? field set to ‘YES’ will be processed.

Click Select Lines… to display all ac lines and change the Selected? field.

Meets Filter

All ac lines that meet a selected advanced filter will be processed.

Use the drop down box to select a defined advanced filter or click Define Filter to display the Advanced Filters

for Branch Dialog. This dialog will allow you to define a new advanced filter for a branch or update an existing

f ilter.

By checking Do not display radial lines creating a single bus island those lines that only island a single bus will not

be displayed with the results.

Click Determine Branches to start the processing once all options have been set.

Because the processing of ac lines in a large power system may take some time, there is an Abort button that is

enabled once the line processing has started that will stop the processing at any point.

The list of resulting ac lines that create islands will be displayed under Branches that Create Islands . To show the

list of buses that are islanded by an outage of any line in the list, select a line and the Islanded Buses list will be

populated. Both the Branches that Create Islands list and the Islanded Buses list are case information displays and

have the same local menu options and characteristics of other case information displays.

485

Dynamic Formatting

Dynamic Formatting Overview

The Dynamic Formatting dialog will allow the specification of how a graphical object will be rendered depending on the

power system object that is representing. The graphical object refers to objects in the oneline diagram, in bus and

substation views, as well as to some parameters of the case information displays.

The case and the one-line diagrams will have each a list of Dynamic Formatting settings. The Dynamic Formatting

settings defined in the case are always applied to bus and substation views, and optionally they can be applied to the

case information displays. The one line diagrams will use its own settings, but optionally can use the general settings

defined with the case.

In general, the oneline dynamic formatting settings have a higher priority, followed by the case dynamic formatting

settings, and this can't be reversed. Also, inside each of the list of dynamic formatting settings, a priority can be

specified, so that objects can be rendered according to the settings with the highest priority.

In the case of the oneline diagrams, the dynamic formatting settings will only be applied during Run Mode. However,

these settings can be modified at any time, without regard for the mode.

486

Run Mode Tools and Options

Dynamic Formatting Dialog

The Dynamic Formatting dialog for the active oneline can be accessed by:

Selecting Options > Dynamic Formatting > Active Oneline from the main menu

Selecting Dynamic Formatting (Active Oneline) from the oneline local menu, or

Clicking the Dynamic Formatting for Active Oneline button

on the Options Mode Toolbar.

The Dynamic Formatting dialog for the general case information displays, bus and substation views, and for all

onelines can be accessed by:

Selecting Options > Dynamic Formatting > Case Info / All Views And Onelines from the main menu

Selecting Dynamic Formatting (All Views) from the bus view local menu or the substation view local

menu, or

Clicking the Dynamic Formatting for Case Info / All Views and Onelines button

on the Options Mode

Toolbar.

This dialog presents the following options:

Allow Oneline to use dynamic formatting defined with case

This option will only be available when the dynamic formatting settings correspond to an active oneline. It indicates

whether or not the oneline diagram will use the dynamic formatting definitions specified in the case.

Formatting Active

If this option is unchecked, the dynamic formatting definition will be ignored when the objects are rendered.

Otherwise, it will be applied if there are graphical objects whose characteristics match the rest of the characteristics

defined in this dialog.

Object Type

The type of power system object with graphical representation, such as a bus, a load, a generator, etc.

Criteria

The filter that applies to the object type defined. The Dynamic Formatting settings will apply to the graphical object

only if the corresponding power system object meets the specified filter. If the criteria box is empty, the Dynamic

Formatting settings will assume that all the objects of the specified type meet the criteria.

Force visibility

When this option is checked, the objects will be displayed (assuming the dynamic formatting applies to them)

independently of the visibility of the layer to which such objects belong, and with no regards of the low and high

zoom levels.

Context

In the Context Objects, the user will specify what specific type of graphical objects the dynamic formatting will apply

to. This list view will be populated with the Case Information Display object (if the dynamic formatting definitions set

correspond to the general case), plus the several graphical objects related to the Object Type. (For buses, for

example, it will include the graphical bus, the bus fields, and the bus gauge).

Fields

In the Fields list view, the user will be able to select which fields the dynamic formatting settings will apply to. This

view will be populated only for those c ontext objects with fields, such as the Case Information Display and the

Object Fields.

Show Only Commonly Used Fields

If this option is checked, only a reduced list of selected fields will be displayed. Otherwise, all the fields belonging to

the object w ill be shown.

Characteristics

The characteristics that the user will be allowed to modify dynamically. These include line thickness, style, color,

and background color; font name, size, color, and style; highlight color; surround shape, color and thickness; color

and magnification of the ‘X’ on top of the objects; and blinking color and interval.

487

Run Mode Tools and Options

Difference Flows: Case Types

When using the Difference Flows tool, information shown on oneline diagrams, case information displays, and power

flow lists is governed by which of the three case types is currently being displayed.

The case types available are:

· Base Case - A solved power system that serves as the reference for the difference flows tool. To establish a base

case, set up a solved power system corresponding to the desired operating point. Open the Difference Flows

Dialog and click the button labeled Set Present as Base Case.

· Present Case - The operating point used in the Difference Flows comparison. Note : The Present Case must have

the same numbering scheme as the Base Case for proper operation of the Difference Flows tool. See Topological

Differences for more information.

· Difference Case - The difference between the Present Case and the Base Case values. The values displayed in

the Difference Case are established using the Base Case as the reference.

To toggle between the different case views, open the Difference Flows Dialog and select the desired case type.

Alternatively, you can click the drop-down arrow next to the Difference Flows button on the Run Mode Toolbar and

select the desired case type.

489

Run Mode Tools and Options

Using Difference Flows

To use the Difference Flows tool:

· Set up a solved power system corresponding to a desired operating point. This operating point will be defined as

the Base Case.

· Select Options > Difference Flows from the main menu, Difference Flows from the oneline local menu in Run

Mode, or the Difference Flows button on the Run Mode Toolbar to display the Difference Flows Dialog.

· On the Difference Flows Dialog, click the button labeled Set Present as Base Case. This stores the current

operating point as the Base Case.

· Define the operating point (Present Case) for which to perform the difference flows comparison. The Present Case

may be developed either by modifying the Base Case as desired and re-solving, or by opening a new case using

File, Open Case from the main menu. In the latter situation, the new case that you open must have the same bus

numbering scheme as the Base Case.

· See Difference Flow Case Types for information on toggling between case views. The currently displayed case

type is shown in the PowerWorld Simulator Status Bar. When viewing either the Base Case or Difference Case, the

corresponding status bar display will be highlighted.

Note that the Difference Flows tool can only be used in Run Mode and the status bar will not display a case type while

in Edit Mode.

When showing the Difference Case, most of the fields shown on the onelines and case information displays show the

difference between the present value and its Base Case value. For example, on the Generator Records Display, an

entry of 0.0 in the MW field indicates that the real power output of the generator did not change. An entry of 10.0 in

the MW field indicates that the present real power output of the generator is 10 MW greater than it was in the Base

Case.

At any time during a simulation, you can set the present case as the Base Case by clicking the corresponding button

on the Difference Flows Dialog.

Conversely, if you have made changes to the present case, and you wish to revert to some or all of the base case

values, you can click on the Reset Case… button. When you click this button, the dialog will expand to show you

options for resetting specific types of values to their base case values.

Expanded Difference Flows Dialog

Once you have indicated which types of values you want to reset (by default, all are selected), you can click on the

Reset Present Case to Base Case Values button to complete the process of reverting to base case values. Note:

491

Run Mode Tools and Options

Present Topological Differences from Base Case

The Present Topological Differences from Base Case option provides the users a way to compare the topological

differences between two difference cases in Simulator.

To compare two cases topologically, you must load the first case you wish to use as the reference into Simulator. Use

the Difference Flows tool from Options > Difference Flows (run mode only) to set the case as the base case in

memory. Once the reference case has been stored as the base case, open the second or comparison case into

Simulator. Now if you check the Options menu, you should see the option labeled Present Topological Differences

from Base Case available. Choosing this option will open the dialog to display the topological differences.

Topological Differences Dialog

The Topological Differences Dialog contains five tabs. All but the Summary tab are instances of Case Information

Displays and thus exhibit characteristics and controls similar to other displays.

Summary

A listing of the types of objects in the case. The first column displays the number of NEW devices in the

comparison case that were not in the base case. Alternately, the Removed column displays the number of devices

in the base case that do NOT exist in the comparison case. The third column simply displays the number of items

that were matched between the two cases.

Elements Added

Tabular listings of all objects that exist in the comparison case, but not in the reference case.

Elements Removed

Tabular listings of all objects that exist in the reference case, but are not present in the comparison case.

Elements in Both

Tabular listings of all objects present in both cases.

Create Bus Swap List

493

Governor Power Flow: Options Tab

This section describes the options available on the Options tab of the Governor Power Flow dialog. The dialog is

accessed by selecting Tools > Governor Power Flow.

This tab sheet presents the following controls:

Disable Automatic Generation Control

Disables automatic MW generation changes during the power flow solution.

Island AGC Tolerance

The ACE mismatch tolerance allowed for the Island to be considered solved in terms of generation dispatch.

Island-Based Automatic Generation Control

Select how the generations should be controlled for the dispatch.

Disabled: The area and super area dispatch settings from the case will be used

Use Participation Factors of individual generators: Each generator will have it’s own participation factor, and

will contribute according to its participation factor divided by the sum of all participation factors of all other

generators in the same island.

Calculate Participation Factors from Area Make Up Power Values: Each area can be assigned a "factor" as to

how it should participate towards the generation dispatch in the island. This is similar to participation factors

for generators. Each area can be assigned a factor. The total percentage the area contributes towards the

generation change needed in the island is equal to its individual factor divided by the sum of all area make up

power factors. Then within each area, the generator participation factors determine how the area’s

percentage is made up of available generation within the area. The area make up power values can be set in

the table of areas on the right hand side of the dialog.

Dispatch using an Injection Group: The island dispatch will be made up by a combination of generators and

loads, defined in an injection group that can be selected from the dropdown list.

How should reactive power load change as real power load is ramped?

If you are using an injection group with load as part of the dispatch, then you can specify how the reactive power

load should respond as the real power demand of loads changes with the dispatch. The reactive power can either

be kept at the starting ratio of real and reactive power of the load, or the MVAR amount can change at each load by

a specified power factor.

496

Movie Maker Dialog

The PowerWorld Movie Maker Dialog is opened by selecting Options / Tools > Make Movie from the main menu in

Run Mode.

This dialog features the following controls:

Type of Movie

Two types of movie files can be recorded, AVI files or MPEG files.

Length of Movie

Two options are provided for specifying the length of the movie to record. You can either use the start recording

and pause recording buttons that appear along the bottom of the Movie Maker form, or you can specify that the

movie is to contain a fixed number of slides. A slide is simply one frame of animation. If you check the latter option,

you must also specify the number of slides to include.

Step by Step

Allows you to pause after each frame.

Length of Frame

The Movie Maker works by capturing sequential frames of animation of a oneline diagram. This particular attribute

controls how long each captured frame is kept on the screen during the movie. This duration is expressed in

milliseconds.

Dimensions (pixels)

Controls are provided that allow you to specify the width and the height the movie should assume during playback.

During the record process, the oneline image will be scaled to match these dimensions so that the movie will

preserve the original resolution when replayed.

Pixel Depth

You can choose the quality of the video by adjusting the Pixel Depth.

Miscellaneous

You can choose to stretch or compress the video.

Temporary Folder

Set the location of the temporary storage folder for use while making the movie.

Along the bottom of the dialog is a row of control buttons. From left to right, these buttons are:

New Movie…

Press this button to begin producing a new movie. If you have already used the tool to produce a movie but have

not yet saved it, you will be asked if you would like to save the movie before proceeding. Then, the dialog will be

restored to its original default settings. Notice that this button is disabled until a movie has been recorded and is

stored in memory.

Start Recording

Movie Maker will begin capturing animation frames by launching the animation of the currently selected oneline

diagram and storing each frame in a buffer in memory. If you have chosen to use a fixed number of frames as the

criterion for stopping the recording, then the frame capturing will cease after the specified number of frames have

been saved. Otherwise, you will have to press the Pause recording button. If you press the Start recording

button after having pressed Pause recording button, the new captured frames will be appended to the list of frames

already in memory.

Pause Recording

Use this button to pause the recording process. If you have specified that the movie should include a set number of

frames, you likely will not need to press this button. However, you may, in fact choose to use it. You can then

press the Start recording button again, and the new screen frames will be appended to the list of frames already

stored in memory.

Save Movie

Press this button to store the sequence of frames to a file in AVI video format. Simply provide a name for the

movie, and Movie Maker will transfer the images to the file for later playback.

Play Movie

If you press this button, Simulator will launch your system’s movie player to play the movie you just recorded. If you

have not yet saved the frames to a movie file, you will first be asked to provide a name for the movie file in which to

498

Contingency Analysis

Contingency Analysis: An Introduction

Contingency analysis is a vitally important part of any power system analysis effort. Industry planners and operators

must analyze power systems covering scenarios such as the long-term effects on the transmission system of both new

generation facilities and projected growth in load. Market analysts and planners must make informed decisions

regarding transactions for energy trade - whether that trade is for the next hour or months down the road. PowerWorld

Simulator’s Contingency Analysis tools provide the ability not only to analyze a power system in its base case

topology, but also to analyze the system that results from any statistically likely contingent scenario.

Industry planning and operating criteria often refer to the n-1 rule, which holds that a system must operate in a stable

and secure manner following any single transmission or generation outage. In PowerWorld Simulator, the individual

contingency conditions can also be tailored to cons ist of either a single element (such as the loss of a transmission

line or transformer), or multiple elements (such as the loss of a generator, several buses and a number of branches

simultaneously). See Available Contingency Actions for a complete list of possible contingency actions.

Simulator can be set to use a Full Newton solution or use a DC Load Flow method to analyze each contingency. The

Full Newton approach is not as fast as a DC Load Flow, but the results tend to be significantly more accurate and

allow for gauging voltage/var effects.

The Tutorial is a great place to start learning about using Simulator’s Contingency Analysis Tool. We also recommend

reviewing the Terminology used throughout the Contingency Analysis help files prior to continuing.

500

Contingency Analysis: Terms

Contingency - Contingencies are the basis of the Contingency Analysis tool. A single contingency can contain a

single contingency element (referred to as n-1 contingencies) or multiple contingency elements.

Contingency Action - A statistically likely condition that could occur during power system operation. See Available

Contingency Actions for a listing of actions supported by Simulator.

Model Criteria - Criteria under which a contingency action will occur. For example, the user can specify that a

generation outage only occur if the pre-contingency flow on a line is higher than a specified amount. Simulator allows

you to define Model Criteria, which consist of both Model Conditions and Model Filters. Normally, no Model Criteria

will be specified for a given action.

Contingency Element - Consists of a single Contingency Action and its associated Model Criteria, Status and

Comment (optional). Multiple Contingency Elements can be defined for a single Contingency.

Contingency Definition - A listing of the Contingency Elements assigned to a Contingency.

Global Action - A Global Action is a list of contingency elements that occur for ALL contingencies. The elements

included in a Global Action do not have to be entered as individual elements in each contingency.

502

Run Mode Tools and Options

Contingency Solution Options Dialog

By default, the contingency analysis will use the same options as the power flow algorithm when solving each

contingency. You may also override these options for all contingencies, and/or for a specific contingency. This results

in the ability to set the power flow solution options in contingency analysis at three different levels

1 Contingency Specific Options (see Contingency Definition Dialog)

2 Contingency Analysis Options (see Contingency Options Tab)

3 General Power Flow Solution Options (see Power Flow Solution Options)

When Simulator executes a particular contingency, it will first look at options specified for that contingency. Any

options which are defined for this contingency will be used. Other options set as "use default" will look to the

Contingency Analysis Options. Again, any options which are defined for contingency analysis will be used. Finally,

options marked in the Contingency Analysis Options as "use default" will be set to the same setting as the power flow

solution options.

In order to specify options for a specific contingency, you will click on a button on the Contingency Definition Dialog. In

order to specify options for all contingencies, you will click on a button on the Contingency Options Tab. Both of these

will bring up the Contingency Solution Options Dialog.

This dialog contains many options regarding the power flow s olution. For options which are a numerical value, just

specify a new value to use. For options which are specified by a check-box, the check-box will have three settings:

use options, do no use option, and use default. For a more detailed explanation of each option see the Power Flow

Solution Options.

To set the values to be the same as the present power flow solution options, click the Set same as for Power Flow

button. To set all options back to use default, click the Clear All Settings button.

503

Contingency Case References

Contingency Analysis always stores a Reference State or pre-contingency state. The Reference State stores

information pertaining to:

· Buses

· Switched Shunts

· Limit Groups

· Loads

· Branches

· Generators

· Areas / Super Areas and

· Power Flow Solution Options

See Reference State Information for details on the specific information stored.

The reference state is loaded into memory prior to the execution of each contingency during automatic processing of

the contingency list. This ensures that all contingencies start from a common Base Case. Furthermore, the system is

set back to the reference state following completion of the automatic processing. Note: The system is not restored to

the reference state when the Solve Selected Contingency option is selected from the Contingency Record Display’s

local menu (see Reference State Solution Options for more information).

The reference state is always stored in Simulator after the first instance of opening the contingency analysis form.

Therefore, opening the contingency analysis again may result in a prompt from the program. This prompt will ask you

if you wish to set the contingency analysis reference state to the current state of the system (in case you have made

changes since the last contingency analysis run), or if you wish to keep the existing contingency analysis reference

state (which was set by previously opening the contingency analysis dialog.) Note that if you choose the second

option, any changes you may have made to the case outside of the contingency analysis will be lost, as the reference

state stored with the contingency analysis tool will reset the system state to the reference state.

Click here for information on defining the reference state.

504

Run Mode Tools and Options

Contingency Case References - State Information

Simulator stores the following information with the Contingency Analysis Reference State:

Bus State

· Voltage Magnitude and angle

· Boolean expression stating whether any load exis ts at the bus (this is used because some of the contingency

actions such as "MOVE GEN" will create a fictitious load if there is no generation at the destination bus)

· MW Marginal Cost

Switched Shunt State

· In or out of service

· Nom value Mvar

· Control mode (FIXED/DISCRETE/CONTINUOUS)

· Nom Value MW

· All Setpoint Values

· Description of Blocks

Limit Group State

· Rating sets for normal operation (Line, Interface…A, B, etc…)

Load State

· In or out of service

· Constant power MW and Mvar components of load

· Constant current MW and Mvar components assuming one per unit voltage

· Constant impedance MW and Mvar components assuming one per unit voltage

· MW Scale

· Mvar Scale

· AGC Status

· Min/Max Load MW

Line State

· In or out of service

· Bypassed?

· Transformer Control?

· Tap ratio

· Phase shift

· High/low desired setpoints

DC Line State (& Multi-Terminal DC Line State)

Generator State

· In or out of service

· MW Output

· Mvar Output

· Max/Min MW Output

· Participation Factor

· Max/Min Mvar Output

· Voltage Setpoint

· AGC Status (YES/NO)

· AVR Status (YES/NO)

· Capability Curve

505

Contingency Case References - Reference State Solution Options

When you solve contingencies one at a time, you may choose between the Solve Selected Contingency and Solve

and Set As Reference options from the Contingency Record Display's local menu.

Solve Selected Contingency causes Simulator to first load the reference state into memory then solve the

contingency. Following the solution, the reference state is not restored; the system state then reflects the power

system flows of the post-contingency state. The advantage of this approach is the ability to implement a contingency

and then modify the system looking for possible actions that might mitigate violations caused by the contingency. Be

aware; however, that prior to solving another contingency, Simulator will reset the system state to reference state

thereby removing all modifications made following the previous contingency solution. The user may also automatically

restore the system state to reference state by selecting Other > Restore Reference from the Contingency Analysis

Dialog.

Solve and Set As Reference acts the same as Solve Selected Contingency with one exception. After executing the

contingency, the post-contingency state is automatically set as the reference state. As a result, all subsequent

contingencies will use the post-contingent state as the Reference State.

Click here for details on the specific information stored in the reference state.

Click here for information on defining the reference state.

Contingency Records

Contingency Analysis: Defining Contingencies

There are four options for defining contingencies. The user may: Load Contingencies from a File, Auto Insert

Contingencies, or use the local menu to either Insert contingencies or Quick Insert a Single Element Contingency.

508

Run Mode Tools and Options

Auto Insert Contingencies

Simulator allows you to automatically generate a contingency list containing branch, generator and/or bus outages. To

accomplish this, select Auto Insert Contingencies from the Contingency Analysis Dialog Local Menu or click the Auto

Insert button on the Contingency Analysis Dialog. This opens the Auto Insertion of Contingencies Dialog (shown

below).

When automatically inserting contingencies, you must specify the type, options and naming conventions you want for

the new contingencies. You must also specify whether to delete or retain existing contingencies. Click on the dialog

below to view more information on automatically inserting contingencies.

Auto Insertion of Contingencies Dialog

The Auto Insertion of Contingencies Dialog has the following controls:

Do Insert Contingencies Button

Press the Do Insert Contingencies button to generate the contingency list.

Automatically generate contingency involving a…

The options available in this box define what to add to each automatically inserted contingency element. You can

choose single transmission line, transformer, transmission line or transformer, generating unit, or bus contingencies.

Choosing one of these options results in each contingency containing only one element of the specific type.

509

You can also define contingencies containing multiple outages by checking the Combination of… option, and then

specifying how many of each type of element (Lines, Transformers, and Generating Units) you want considered in

the contingency. When you use the Combination of… option, Simulator will automatically determine all possible

combinations for the element types specified (based on the settings in Options ) and create the contingencies.

Combination contingencies do not currently allow the inclusion of bus contingencies.

Options

When Simulator auto-generates the contingency records for the element types specified, the options in this section

will further determine which elements are included and which elements are ignored.

Delete Existing Contingencies

When checked, any previously existing contingency records will be deleted before any automatically created

contingencies are inserted.

Use Area/Zone Filters

When checked, the elements included in the auto-generated contingencies will be only elements that are within

areas and zones defined in the Area/Zone/Owner Filters dialog. You may edit the Area/Zone/Owner filters by

clicking on the Edit Area/Zone Filters button.

Only include … meeting an advanced filter

When checked, the branches, generators, or buses included in the auto-generated contingencies will be only

those elements meeting conditions outlined by an advanced filter. To set the conditions to be used, click the

respective Define… Filter button.

Only include elements within X buses of bus

When checked, only elements that are electrically within X number of buses from the specified bus will be

included when creating the contingencies. For example, consider bus 1 is electrically connected to bus 2,

which is in turn connected to bus 3. If we specify the bus to be bus 1, and choose to include only elements that

are within 0 buses of bus 1, then the contingency record will include the branch between buses 1 and 2, and if

desired any generators attached to bus 1. However the branch between buses 2 and 3, and any devices

attached to bus 2 and 3, will NOT be included in the contingency, because bus 2 is electrically 1 bus away from

bus 1.

To specify the bus used, you can find the bus by using the search engine. The search engine allows you to

search by name or number. If you know the bus number, choose Sort by Number, and type the bus number in

the search box. If you know the name of the bus, choose Sort by Name, and type the name of the bus in the

search box. If you are not sure of the name of the bus, you can use wildcard characters to search through the

list of buses until you find the desired bus.

How to name the contingencies

This section allow s you to define how each automatically inserted contingency record will be named.

Identify lines using prefix

These four fields allow you to set a specific prefix for generators, lines, transformers and buses so that you can

easily determine what type or types of contingencies are modeled in the auto-generated contingency records.

By default, the prefixes are G for generators, L for lines, T for transformers and B for buses. However, you can

change these prefixes to any character or set of characters you wish.

Identify buses by

This field allows you to specify whether each contingency is labeled using the bus numbers, bus names, or both

as identifiers. Whichever type of identifier you choose here will be combined with the defined prefixes to

uniquely define the individual contingency elements within each auto-generated contingency record.

Include Nominal Voltages

This check-box is used to include the nominal voltage of the bus in the contingency label.

510

Run Mode Tools and Options

Auto Insert Contingencies - How to name the continge ncies

This section allows you to define how each automatically inserted contingency record will be named.

Identify … using prefix

These four fields allow you to set a specific prefix for generators, lines, transformers and buses so that you can

easily determine what type or types of contingencies are modeled in the auto-generated contingency records. By

default, the prefixes are G for generators, L for lines, T for transformers and B for buses. However, you can change

these prefixes to any character or set of characters you wish.

Identify buses by

This field allows you to specify whether each contingency is labeled using the bus numbers, bus names, or both as

identifiers. Whichever type of identifier you choose here will be combined with the defined prefixes to uniquely

define the individual contingency elements within each auto-generated contingency record.

Include Nominal Voltages

This check-box is used to include the nominal voltage of the bus in the contingency label.

511

Loading Contingencies from a File

Simulator can load contingency definitions from a text file. The contingencies may be specified in one of three formats

· Simulator Auxiliary File Format (*.aux) (also see Contingency Subdata)

· Simulator Version 5-7 Contingency File Format (*.ctg) (see the old users manual, or contact PowerWorld

Corporation)

· PTI PSS/E-formatted Contingency Files (*.con).

To load contingencies from a text file, click the Load button on the contingency analysis dialog. A dialog box will be

provided for you to specify the file from which to load the contingency records. Specify the file type in the Files of Type

dropdown box, and select the appropriate file. If contingency records have already been defined for the case with

which you are working, you will be asked if you wish to delete the existing contingencies. Respond affirmatively to

delete the existing contingencies before adding the new ones from the specified files. Otherwise, click No, and the

contingencies loaded from the file will be appended to the already existing list.

512

PowerWorld Simulator version 11. Manual - page 13