Large scale voltage stability constrained optimal VAr planning and voltagestability applications using existing OPF/optimal VAr planning tools

Traditionally in optimal VAr planning, the feasible operation has been tran slated as observing voltage profile criteria ensuring that the system volta ge profile is acceptable for system normal and post contingency conditions [1]. This feasibility definition is not sufficient when considering the VAr planning practice of the utilities concerned with voltage stability proble ms. Presently, these utilities use two reinforcement criteria for VAr addit ions. While for VAr design in the regions the voltage profile criteria is c onsidered, for bulk transmission system VAr resources are designed to guard against voltage instability. This paper reports on the findings of a recen tly completed EPRI project [1] evaluating the existing Optimal VAr planning /OPF tools for voltage stability constrained VAr planning and voltage stabi lity applications. Two of the selected tools were adapted to address these applications on four large scale utility systems (up to 6000 buses). The re sults were also verified using EPRI's voltage stability program (VSTAB). Th e results obtained indicate that OPF/VAr Planning tools can be used to addr ess voltage stability constrained VAr planning and voltage stability applic ations in an accurate way. Additional advantages offered by these tools are ; easier procedures, less computation and avoidance of engineering judgment in identifying the amount of VAr requirement at the candidate sites.