Software Patches

November 9, 2021

Features and Improvements

  • Available Transfer Capability (ATC) Tool: Added new Iteratively Found string CTG_FAIL_ITERATED_OVERLOAD that indicates that the contingency failed to solve at some point during the Iterated Linear Step (IL) then Full CTG method and using the option to iterate on failed contingencies. The Transfer Limit that is reported is the accumulated amount that is possible for which the contingency solves, but the monitored element is overloaded, as determined by a linear step calculation, at this transfer level. Using the iterated method attempts to get as close as possible (within specified tolerances) to the highest transfer amount at which the contingency will solve. This is very similar to a PV nose point.
  • Transient Stability: Added "MW Nominal Tripped" field for tracking and plotting results for loads in transient stability. It will also be recorded for Areas and Zones as a field. This field tracks the Nominal MW Tripped during the entire simulation.
  • Bug Fixes

    • Available Transfer Capability (ATC) Tool: Removed the change made in the 6/22/21 patch for the ATC (IL) then Full CTG solution method that set the new stepsize to (stepsize + stepsize/2) when the stepsize is negative and the monitored element is overloaded. This change does not work in all situations. This was instead fixed by improving the ATC (IL) then Full CTG solution process when iterating on a failed contingency to better handle negative stepsizes and stepsize changes needed to find a solution for the contingency and attempt to reduce the loading on the monitored element to its limit.
    • Sensitivity Calculations: Update the algorithm to determine unnecessary interface element line open elements to also catch buses isolated by contingent interface elements. The isolated buses cause numerical problems in the sensitivity calculations. The algorithm fixes this by removing one of the contingent interface elements. This has no effect on the interface flow because the flow through the bus is still zero, but fixes the numerical problems.