Transient Stability Contingency Element Dialog

See Also

The Transient Stability Contingency Element Dialog is used to specify specific transient stability events and when they occur during the analysis.

Event Description

Drop-down containing a list of all currently defined events. An even description will be created automatically based on the event time, event object, and even action. This drop-down can be used to switch between events and make any necessary modifications.

Object Type

Specify the object type for the event. The type of object chosen will change the type of events that can occur.

Choose the Element

This list will be updated as the Object Type is changed. This list contains all of the available objects for the selected Object Type. Select a specific object from this list for which the event will be applied.

Event Time

Specify the time in seconds at which the event occurs.

Event Type, Event Parameters

The type of event and parameters will change depending on the Object Type chosen. Valid options are:

Bus

Apply Fault

Apply the specified fault type and fault across.

Fault Type - Balanced 3 Phase, Single Line to Ground, Line to Line, or Double Line to Ground.

Fault Across - Solid, with Impedance and specifying PU Resistance and PU Reactance, or with Admittance specifying PU Conductance and PU Susceptance. Starting in Version 19, there are also choices for to Achieve Voltage and To Scale Voltage.

Added in Version 19When choosing any of the unbalanced fault types, then a check box entitled Calculate Effective Impedance from Sequence Networks is made active and an image is shown in the right portion of the dialog depicting how the total effective positive sequence fault impedance is calculated from the driving point sequence impedance at the fault point and the fault impedance. This check box is used in combination with the choice of Fault Across choice below to determine the impedance used to model the fault in the positive sequence network with this calculation being described in the table at the end of this topic.

Added in Version 20, May 14, 2018 patchWhen choosing to Apply Fault, a check box option for Self Clearing Fault is available. To default behavior and previous behavior is represented by not checking this box. This means that when a bus becomes isolated due to opening other branches to isolate this bus, the fault will remain in place. Because the bus is isolated it will not impact the simulation, however if branches are closed back in such that the bus is no longer isolated then the fault will again be there. By checking Self Clearing Fault however, as soon as a fault location becomes isolated the fault will automatically clear itself. It is appropriate to not check this box when modeling a permanent fault such as a tree falling on a line, while it may be appropriate to check this box to model a lightning strike or a wind blowing a tree branch into a line.

Clear Fault

Clear a fault.

Open

Opens all AC lines connected to a bus.

Generator

Open

Open the generator.

Close

Close the generator.

Ramp Values

Ramp the output of the generator as defined by the Action Field. Options for the Action Field are MW Setpoint at Bus, Exciter Setpoint (Vref), Governor Setpoint (Pref), Part. Factor and Rotor Angle (Degrees), Delta Speed (Hz). Specify that the output be ramped By Value or Percentage. Specify the Ramp Duration in seconds at which the ramping lasts.

Set Values

Set the output of the generator as defined by the Action Field. Options for the Action Field are MW Setpoint at Bus, Exciter Setpoint (Vref), Governor Setpoint (Pref), Part. Factor and Rotor Angle (Degrees), Delta Speed (Hz). Specify that the output be set By Value or Percentage.

Change Values

Change the output of the generator as defined by the Action Field. Options for the Action Field are MW Setpoint at Bus, Exciter Setpoint (Vref), Governor Setpoint (Pref), Part. Factor and Rotor Angle (Degrees), Delta Speed (Hz). Specify that the output be chamge ByValue or Percentage.

Enable AGC

Enable AGC on the generator.

Disable AGC

Disable AGC on the generator.

Load

Open, Close

Specify that the load either be opened or closed.

Change Values

Change the output of the load as defined by the Action Field. Option for the Action Field is MW. Specify that the output be set By Value or Percentage.

Set Values

Set the output of the load as defined by the Action Field. Option for the Action Field is MW. Specify that the output be set By Value or Percentage.

Ramp Values

Ramp the output of the load as defined by the Action Field. Options for the Action Field are MW. Specify that the output be ramped By Value or Percentage. Specify the Ramp Duration in seconds at which the ramping lasts.

NOTE: When changing, setting or ramping a load, a new scalar is computed using the initial Real Power of the load. When the load does not has a motor transient model, that scalar is multiplied to the present Real Power to get the desired value. The same scalar is multiplied to the present Reactive Power to compute a new value. The power factor then remain the same during initial load change. When the load has a motor transient model the real power is only modified and the reactive power is not modified thus will react accordingly to the change.

Switched Shunt

Open, Close

Specify that the load either be opened or closed.

Change Values

Change the output of the switched shunt as defined by the Action Field. Option for the Action Field is Nominal Mvar. Specify that the output be set By Value or Percentage.

Set Values

Set the output of the switched shunt as defined by the Action Field. Option for the Action Field is Nominal Mvar. Specify that the output be set By Value or Percentage.

Branches/Transformer

Apply Fault

Apply the specified fault type.

Fault Type - Balanced 3 Phase, Single Line to Ground, Line to Line, or Double Line to Ground

Fault Across - Solid, with Impedance and specifying PU Resistance and PU Reactance, or with Admittance specifying PU Conductance and PU Susceptance. Starting in Version 19, there are also choices for to Achieve Voltage and To Scale Voltage.

Percent Location (near to far) - Specify the location of the fault as a percentage of the distance from the near end of the line. A fault at the near end would be a percentage of 0% and a fault at the far end would be percentage of 100%.

Added in Version 20, May 14, 2018 patchWhen choosing to Apply Fault, a check box option for Self Clearing Fault is available. To default behavior and previous behavior is represented by not checking this box. This means that when a fault location becomes isolated due to either opening both ends of this branch or by opening other branches to isolate a portion of the system, the fault will remain in place. Because the fault location is isolated it will not impact the simulation, however if branches are closed back in such that the fault location is no longer isolated then the fault will again be there. By checking Self Clearing Fault however, as soon as a fault location becomes isolated then the fault will automatically clear itself. It is appropriate to not check this box when modeling a permanent fault such as a tree falling on a line, while it may be appropriate to check this box to model a lightning strike or a wind blowing a tree branch into a line.

Clear Fault

Clear a fault.

Open

Which End - Both Ends, From End Only, To End Only, One Phase Open

Close

Which End - Both Ends, From End Only, To End Only

Bypass, and Not Bypass

Use this option to either Bypass or Not Bypass a branch. Normally we would expect this branch to be a series capacitor or reactor.

Set Values

Use this option to Set Value Type of Line Impedance PU Resistance and PU Reactance or GMD-Induced DC Voltage value.

DC Line

Open

Open the entire DC line.

Injection Group

Open

P or Q - MW, MVAr

Device - Generation, Loads

MW or MVAr - Amount to open. The amount to open will be based on the initial condition of the device (not the transient condition), and devices will be opened in order of highest participation factor to lowest participation until at least the amount specified has been exceeded.

Line Shunt

Open, Close

Specify that the line shunt either be opened or closed.

Transformer

Set Values

Set the value of the transformer as defined by the Action Field. Options for the Action Field are LTC Tap, Phase in Deg, Tap Step Position, Setpoint for Control and Range for Control. Specify that the value be set in the box specified.

Change Values

Change the value of the transformer as defined by the Action Field. Options for the Action Field are LTC Tap, Phase in Deg, Tap Step Position, Setpoint for Control and Range for Control. Specify that the value be set in the box specified.

Enable Auto Control

Enable Auto Control on the transformer.

Disable Auto Control

Disable Auto Control on the transformer.

Area

Ramp Values

Ramp the output of the Areaas defined by the Action Field. Option for the Action Field is Export to Other Area (MW). Specify that the output be ramped By Export MW. Specify the Other Area Number to which the export is happening. Specify the Ramp Duration in seconds at which the ramping lasts.

Enable AGC

Enable AGC on the Area.

Disable AGC

Disable AGC on the Area.

Click this button to accept any changes and close the dialog.

Save

Click this button to save any modifications to the current event. The dialog will remain open.

Insert

Click this button to create a new event with the specified parameters.

Delete

Click this button to delete the current event as defined by the Event Description.

Help

Click this button to open this help topic.

Cancel

Close the dialog without saving any of the changes.

Calculation of the Total Effective Positive Sequence Impedance seen at the fault Point

The check box Calculate Effect Impedance from Sequence Networks was added in Version 19.

Fault Across	Fault Type Choices
	Balanced 3 Phase	Unbalanced Faults: Single Line to Ground, Line to Line, or Double Line to Ground
Solid	A very small impedance is assumed to represent a solid fault. Simulator uses a Fault impedance of Zfault = 0 + j1E-8	You must specify to Calculate Effective Impedance from Sequence Network when choosing to fault across Solid in combination with any unbalanced Fault type. If you do not do this on the dialog box then Simulator will not allow you to close the dialog. If you specify a Solid unbalanced fault in an Auxiliary file without specifying the option to CALCSEQ, then Simulator will assume the option to calculate effective impedance was intended. An appropriate warning message is also written to the message log to indicate that this is being done.
with Impedance but not Calculate Effect Impedance from Sequence Networks	Option will appear to specify the PU Resistance and PU Reactance. This represents the total effective positive sequence impedance seen at the fault point looking into the fault. Note that when choosing Fault Across to be with Impedance and not checking the box Calculate Effective Impedance from Sequence Network, then the Fault Type choice has no effect on the simulation. Users may still choose the Fault Type as it is informational.
with Impedance and Calculate Effect Impedance from Sequence Networks	Not applicable. When choosing a Balanced 3 PhaseFault Type, the check box to Calculate Effective Impedance is not available.	Option will appear to specify the PU Resistance and PU Reactance. This represents the impedance across the fault itself. The total effective positive sequence impedance seen at the fault point looking into the fault is then calculated from the driving point sequence impedance at the fault point and this fault impedance. The image on the right portion of the dialog depicts how this total effect impedance is calculated.
with Admittance	Option will appear to specify the PU Conductance and PU Susceptance which represents the admittance seen at the fault point looking into the fault. An admittance value of 0 - j1E8 would be equivalent to our default fault impedance. Otherwise this option works the same as specifying with Impedance, but instead a user enters a value of admittance.
to Achieve Voltage	Option will appear to specify a PU Voltage. This represents the desired PU voltage at the fault point immediately after applying the fault. PowerWorld Simulator will then automatically determine a fault impedance needed to result in that post-fault voltage. Note that when choosing Fault Across to be to Achieve Voltage, then the Fault Type choice has no effect on the simulation, but remains informational.
to Scale Voltage	Option will appear to specify a Factor. This represents the factor by which it is desired that the PU voltage at the fault point be changed immediately after applying the fault. For example, if the pre-fault voltage is 1.05 pu and and a factor of 0.6 is specified, then the desired post-fault voltage is 0.63 per unit. PowerWorld Simulator will then automatically determine a fault impedance needed to result in that post-fault voltage. Note that when choosing Fault Across to be to Achieve Voltage, then the Fault Type choice has no effect on the simulation, but remains informational.