Line Outage Distribution Factors Dialog

 

The LODF Dialog enables you to control and to view the results of Line Outage Distribution Factor calculations. You access this dialog by selecting Sensitivities > Line Outage Distribution Factors (LODFs) from the Run Mode ribbon group on the Tools ribbon tab in Run Mode only.

Two LODF dialogs are allowed to be opened simultaneously, but when doing this Simulator forces one dialog to show a Single LODF calculation, while the second dialog shows the LODF Matrix.

The dialog has the following options:

Output Option

Choose Single LODF to calculate only the sensitivities related to the status change of a single transmission line. Choose LODF Matrix to calculate a matrix of sensitivities.

For Single LODF: Specify Near Bus, Far Bus

Specify the line whose status modification you would like to determine sensitivities to. The direction of the near/far chosen is important. Switching the near and far bus around will change the sign of all the LODF sensitivities.

For Single LODF: Action

Check Outage Sensitivities to determine sensitivities for the outage of a line.

Check Closure Sensitivities to determine sensitivities for the closure of a presently outaged line. The LODF might better be named a Line Closure Distribution Factor (LCDF) in this case.

For LODF Matrix: Specify Lines to Process (Outage or Closure) and Lines to Monitor

Lines to Process and Lines to Monitor

Choose which lines to process and which lines to monitor by choosing either all AC lines, only those that meet the area/zone/owner filters, only lines with Selected field set to YES, or only those lines that meet an Advanced Filter. The lines to monitor can also be set the same as the lines selected for processing.

Do not monitor lines that are open can be checked to exclude lines that are presently open from the monitoring. This option only affects that lines that are being monitored.

Monitor Branches in Interfaces

Check the Monitor Interfaces (will add branches to the Lines to Monitor) checkbox to include interfaces in the monitoring. By including interfaces, the individual lines that are monitored as part of the interface will be added to the list of monitored lines. Contingency elements within interfaces are ignored. This option does not change the format of how the results are reported.

After choosing Calculate LODFs, each row of the results represents the line being outaged/closed. Each column of the results represent the line begin monitored and the corresponding LODF/LCDF for that line.

Linear Calculation Method

Linearized AC

This calculation method is not available for LODF sensitivities.

Lossless DC

Uses the DC power flow approximation.

Lossless DC with Phase Shifters

Check this to include the impact of phase shifter controllers with the Lossless DC calculation. By checking this, it is assumed that operating phase shifters will maintain their control requirements after the line outage.

The Lossless DC methods will be affected by the DC Power Flow Model settings in Power Flow Solution: DC Options. Click on the DC Model Options button to open the dialog that sets these options.

Line Closure Options

Status Options Added in version 20

This drop down will only be enabled if the power flow case has branches with Branch Device Type of Breaker or Load Break Disconnect. Line closure sensitivities are calculated by modeling power injections at the terminals of the line being closed. These calculations can only be done if the terminals are in energized islands. When using a full topology case that models switching devices such as Breakers and Load Break Disconnects to open and close branches, the terminals of the branch being studied in a line closure sensitivity will never be energized. This means that the line closure sensitivities cannot be determined. If the calculations are modified to model the power injections at the energized terminals of the switching devices instead, the line closure sensitivities can be calculated. This option allows selection of where the power injections are modeled for line closure sensitivities:

Line Status

This option means that the branch being studied will change its own status to open it rather than using other switching devices. This occurs in a case without switching devices or when studying the closure of a switching device. Use the terminals of the branch being studied for closure sensitivities. If the branch is open because breakers or other switching devices have been opened to disconnect the branch, the line closure sensitivities cannot be calculated and will all be 0.

Breaker Status

Use this option to transfer the calculation of line closure sensitivities to the energized terminals of Breakersthat have been opened to disconnect a line. This calculation can only be done if breakers are strictly in series with the line being studied.

Breaker and Load Break Disconnect Status

Use this option to transfer the calculation of line closure sensitivities to the energized terminals of Breakersand Load Break Disconnects that have been opened to disconnect a line. This calculation can only be done if switching devices are strictly in series with the line being studied.

Calculate based on post-closure flow (LCDF) and Calculate based on pre-closure flow (MLCDF)

Added in version 19, build on May 31, 2017

A line closure sensitivity determines the percentage of the post-closure flow on a line that will show up on another line. Because these sensitivities are calculated while the line is open, it is often more convenient when linearly determining the impact of a line closure, or multiple line closures, to use a sensitivity that is based on the pre-closure flow on the line. The pre-closure flow on a line is just the line flow calculation using existing system voltages and angles and ignoring the status of the line.

If comparing a linear sensitivity calculation and resulting flow changes against actual system changes, it is often most convenient to use the sensitivity based on the post-closure flow. This value is referred to as the Line Closure Distribution Factor (LCDF). This value will also correspond to the LODF of the line once it is closed and the linear impact of opening the line is calculated. When doing calculations that determine the actual flow changes on other lines caused by closing a line, it is often most convenient to use the sensitivity based on the pre-closure flow of the line. This can be easily calculated from the present voltages and angles in the case. This value is referred to as the Modified Line Closure Distribution Factor (MLCDF).

Calculate LODFs

Click this to calculate the LODFs and update the display.

Advanced LODF Calculation

Opens the Advanced LODF Calculation dialog for setting additional options for the calculation.

 

LODFs Tab

After calculating a LODF Matrix, each row of the results represents the line being outaged/closed. Each column of the results represent the line being monitored and the corresponding LODF/LCDF for that line.

When calculating LODFs for a single branch, This tab contains a table showing a list of the lines in the case. Since this table us another variety of the Case Information Displays, you may interact with it in a familiar manner. Click on any of the field headings to sort by that field. Right-click on the display to call up the display’s local menu. From the local menu, you can print the violations, copy the violation records to the Windows clipboard for use with another application, modify the format and content of the listing, view the information dialog of the respective element, and view the Quick Power Flow List or Bus View Display.

The default fields for the tab are as follows:

From Bus Number and Name

From bus number and name of the monitored line.

To Bus Number and Name

To bus number and name of the monitored line.

Circuit

Two-character identifier used to distinguish between multiple lines joining the same two buses.

% LODF

The LODF value for the monitored line.

From MW, To MW

The present MW flows on the monitored line at the from bus and the to bus.

From CTG MW, To CTG MW

The projected MW flows after the change in line status on the monitored line at the from bus and the to bus.

 

Interface LODFs

This tab lists LODFs for interfaces. These LODFs are calculated based on the LODFs of the individual branches that comprise the interface. Only monitored branches are included, and any contingency elements within the interface are ignored.

After calculating a LODF Matrix, each row of the results represents the line being outaged/closed. Each column of the results represent the interface being monitored and the corresponding LODF/LCDF for that interface.

The default fields for this tab when calculating a single LODF/LCDF are as follows:

Number

This is the number of the given interface.

Name

This is the name of the given interface.

% LODF

This is the LODF value for the interface. This is calculated from the LODFs of the individual branches that comprise the interface. This is simply a sum of the branch LODFs based on the direction that the branch is defined in the interface and the monitored direction of the branch in the interface. Any contingency elements within the interface are ignored.

Interface MW Flow

The present MW flow on the interface.

This flow will include the impact of contingency elements within the interface if the Monitor/Enforce Contingent Interface Elements option found with the General tab of the Power Flow Solution page of the Simulator Options dialog is set to enforce interface contingent elements during the power flow solution.

CTG MW

The projected MW flow on the interface based on outaging the specified branch.

This flow ignores the impact of any contingency elements within the interface. It only includes the estimated post-contingency flow on branches that are monitored as part of the interface.