Running the Contingency Analysis

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To run the contingency analysis means to model and solve one or more contingencies from the case’s current contingency list. Simulator’s Contingency Analysis Dialog gives you several options for running the contingency analysis. You may:

To run the complete contingency list, do any one of the following:

To pause the contingency run once it has started, click either Pause Run at the bottom of the Contingency Analysis Dialog. To resume a paused contingency run, click the Continue button . Finally, to terminate a contingency run, click the Abort button next to the Pause/ Continue button. The status indicator will inform you of the run’s current state.

To solve a single contingency, identify its violations, and then leave the system in this post-contingency, select the contingency you wish to model in the Contingency Records Display, right-click to invoke the display’s local menu, and select Contingency records > Solve Selected Contingency. (Realize that prior to solving another contingency, Simulator will reset the system state to the reference state).

To solve a single contingency and set it as the reference (starting) case for further contingency analysis activity, select the contingency you wish to model in the Contingency Records Display, right-click to invoke the display’s local menu, and select Contingency records > Solve and Set As Reference. Simulator will model the selected contingency, flag its violations, and leave the resulting case in memory so your future work will affect the post-contingency system rather than the original pre-contingency state. See Contingency Case References for more information.

When selecting the Solve and Set as Reference option, a warning dialog will appear that allows you to verify if this is the action that you really want to take. Selecting Yes will continue with this action. Selecting No will abandon this operation. Selecting Yes to All will specify that you no longer want to see this dialog and the next time you call this action it will occur with no prompt and the action will occur. The Yes to All option will remain in effect until the contingency analysis dialog is closed. Once the dialog is re-opened again and this option is selected, the warning dialog will appear again.

The Refresh Displays After Each Contingency checkbox is used to force a refresh of the counters after each contingency, which may slow down processing of the contingency set (accordingly, this box is unchecked by default to maximize solution speed).

 

How Each Contingency is Implemented

Each contingency is processed in the same manner. All of the actions that are defined with the contingency itself are combined with the actions of all Remedial Actions that are not set to be skipped and all Global Actions if using the global action list. Regardless of the origin of the action, the actions are processed in an order and manner based on their action Status and other settings as described below.

Added in Version 20

At the beginning of the process while the system state is still in the contingency reference state (base case state), any Arming Criteria specified with a Remedial Action or Remedial Action Element where the Arming Status is CHECK is evaluated to determine if the Remedial Actions or Remedial Action Elements are armed. Only Remedial Action Elements that are armed can have their actions implemented during the processing described below. Remedial Actions and Remedial Action Elements can also be armed if their Arming Status is ALWAYS or their Arming Criteria is not specified. In order or a Remedial Action Element to be applied during the solution process, it must be armed and the Remedial Action to which is belongs must also be armed.

Persistent option was added in Version 19

Normally after any contingency element, Remedial Action Element, etc. is applied during this solution process, it will not be applied again. The exception to this is actions that are marked as Persistent = YES.

 

Contingency Processing Order Based on Status and Calculation Method

The following describes the order in which the different action statuses are evaluated and when the actions are applied. This process is only applicable when the Calculation Method is set to Full Power Flow and solving the ac power flow or when using Iterated Linear Analysis. Differences in the process when using these two methods are noted.

  1. Various post-contingency settings for Generator and Switched Shunt controls may be changed for the contingency solution as described in Generator Post-Contingency AGC, Generator Maximum MW Response, Generator Line Drop and RCC, and Contingency Options: Switched Shunt Response. For any InjectionGroup with a CTGOutageIntertie defined [Added in Version 24], if there are any online generator, load, or shunt objects in the initial case then we flag that InjectionGroup for use in Step 5 below.
  2. Apply ALWAYS, unconditional actions (actions with no Model Criteria except for SOLUTIONFAIL actions), and true CHECK actions
  3. Update topology (branch and bus status and derived status)
  4. Apply true TOPOLOGYCHECK actions
    • TOPOLOGYCHECK actions wssith the smallest Time Delay will be applied
  5. [Added in Version 24]For any InjectionGroups flagged in Step 1, if all generator, load, and shunt objects in the InjectionGroup are not opened, then also open the branch or interface specified as the CTGOutageIntertie.
  6. Store reference state for use if solution failure occurs and SOLUTIONFAIL actions existc
  7. Solve power flow (For full ac analysis, the power flow is actually solved here. For iterated linear analysis, the linear estimates of branch flows are determined for branches that are being monitored in a linear contingency state.)
    • SOLUTIONFAIL actions were Added in Version 19
    • If the power flow solution fails and any SOLUTIONFAIL actions are available, the reference state in step 6 is restored and any true SOLUTIONFAIL actions with the smallest Time Delay are then applied
    • If any SOLUTIONFAIL actions are applied, the process will go back to step 6 and repeat (This loop will abort after 100 solution failures)
    • If there is still a solution failure, abort the contingency process and report failure
  8. Apply true POSTCHECK actions and true TOPOLOGYCHECK actions
    • TRANSIENT actions will also be evaluated
    • CUSTOMMONITORs with Trip action will be evaluated Added in version 19, build on December 23, 2016
    • TRANSIENT, CUSTOMMONITOR, POSTCHECK, or TOPOLOGYCHECK actions with the smallest Time Delay will be applied
    • TRANSIENT models and CUSTOMMONITORs are only included when doing full ac analysis
  9. Repeat steps 3-8 until no more POSTCHECK, TOPOLOGYCHECK, CUSTOMMONITOR, or TRANSIENT actions are done (This loop will abort after 100 iterations)

Contingency Processing Order Based on Action

Within a given processing step as described above in the Contingency Processing Order Based on Status and Calculation Method section multiple actions can be applied. When more than one action is applied at the same time, the Element Type and Action Type of the contingency element determine the order in which they applied. The following list gives details of this order:

  1. Element Type = Abort
  2. Element Type = Branch, Bus, Interface, Series Capacitor, 3-Winding Transformer, or DC Line and Action Type = Close
  3. Element Type = Generator, Load, Switched Shunt, Injection Group, Line Shunt, or DC Converter and Action Type = Close
  4. Element Type = Branch, Generator, Load, Switched Shunt, Interface, Injection Group, Series Capacitor, Phase Shifter, DC Line, DC Converter, Substation, or Script and Action Type = Move, Set To, or Change By
  5. Element Type = Generator, Load, Switched Shunt, Injection Group, Line Shunt, DC Converter, or Substation and Action Type = Open
  6. Element Type = Branch, Bus, Interface, Series Capacitor, 3-Winding Transformer, or DC Line and Action Type = Open
  7. Element Type = Area and Action Type = Set To