SYSTEM-AREA OPERATING MARGIN ASSESSMENT AND SECURITY ENHANCEMENT AGAINST VOLTAGE COLLAPSE

The (very) short term reactive power scheduling function, to be adopte d by ENEL Spa, takes into account the voltage stability requirements i n a preventive application of the security function. In this environme nt the procedure determines the voltage collapse distance of the globa l system and of the areas controlled by the Secondary Voltage Regulati on (SVR) both in short (24 hours ahead) and in a very short term (few hours or fractions of hour ahead). The procedure also schedules the co ntrol actions to be taken in emergency states in a preventive way. Are a or system-wise indicators, based on nodal sensitivities and/or eigen (singular) value analysis, provide effective measures of the margins of the system with respect to the risk of voltage collapse and the rel ated corrective actions. Applications of the procedure to the EHV netw ork and to a subtransmission area of the ENEL system are presented in the paper.