A statistical analysis of the impact on security of a protection scheme on the French power system

This paper presents the results of the study of the impact on security of on-load-tap-changers (OLTCs) automatic blocking devices installed in the French Riviera subsystem. These devices were installed to prevent voltage collapses: OLTCs are blocked on one area when the specified nodes voltage go under a predetermined level. Usually, such studies rely on a few simulations chosen by experts. In the present case, the study relied on a dynamic database, composed of the results of simulation of nearly 1500 randomly defined scenarios (operating point and dynamic model hypotheses and contingencies). The simulation model includes detailed units models (AVR and governors) and all automatic protection schemes, including the defense plan. Using this database, several classes of scenarios with different behavior of the OLTC blocking device were identified, the influence of such protection on system security identified, and some improvements proposed.