Contingency Vulnerable Areas / Loadpockets

Overview
CVA determines all subnetworks within a given region of interest and buffer zone that can experience voltage instability. All areas composed of subsets of subnetworks that can experience cascading voltage instability are also identified. The subset of these areas that experience voltage instability for contingencies identified by VCCS are also determined and are called loadpockets. The contingencies that produce voltage instability in each loadpocket are also identified.

Structure
  • Determines loadpockets that contain one or more subnetworks that experience local or cascading voltage instability at the point of non-solution
  • Design or operation planning solutions must look to split these structurally determined areas into smaller areas where the consequence of voltage instability would be less onerous
  • Determines loadpockets such that increase in active loading in the loadpocket causes the same cascading voltage instability as the contingencies that are associated with the load pocket
  • Determines loadpockets such that a V-Q curve at a bus in the largest subnetwork in the loadpocket causes the same cascading voltage instability of subnetworks as the contingencies associated with producing voltage instability in that area
  • Provides a definition of areas and loadpockets that allows systematic testing of the reactive loading or reactive reserves of each of the nested subnetworks belonging to the loadpocket as a measure of proximity to cascading voltage instability in the loadpocket
Issue Diagnosis
  • For a non-solving contingency, computes the point of non-solution which occurs after an increasing percentage of the contingent equipment is removed
  • Determines the control region where voltage instability within the load pocket is initiated and should be arrested at the point of non-solution. Other programs determine control regions by focusing on the immediate vicinity of the contingency rather than addressing the structural cause of the instability
  • Determines the subnetwork where voltage instability is initiated for any load pocket. These structurally determined initiating subnetworks are vital to understanding and mitigating voltage instability, yet traditional methods are unable to locate them
  • Determines the problematic initiating subnetworks that belong to virtually every area and must be addressed via posturing control to assure robustness of the design or operation plan. These problematic areas are associated with structural weakness that can not be identified by traditional methods
  • The load, the number of buses and the number of generators in a loadpocket should be small and design and operation planning solutions must be prioritized for these important areas
  • Provides a definition of areas or loadpockets after postured control that provides a measure of security for the contingencies that solve and are associated with the loadpocket or area
  • Determination of areas and loadpockets by CVA provides for more accurate P-V and V-Q measures of proximity to voltage instability for solving contingencies that are close to voltage instability or for non solving contingencies after postured/preventative control