14. Distribution and Transmission System Reliability Measures

The power system reliability is one of the features of power system quality. The electric utility industry has developed several performance measures of reliability or reliability indices. These reliability indices include measures of outage duration, frequency of outage, number or customers involved or their lost power or energy, and the response time. The distribution and transmission reliability indices include system average interruption frequency index (SAIFI), Transformer SAIFI, equivalent number of interruptions related to the installed capacity (NIEPI), customer interruption, system average interruption duration index (SAIDI), transformer SAIDI, equivalent interruption time related to the installed capacity (TIEPI), customer-minutes lost (CML), customer average interruption duration index (CAIDI), customer total average interruption duration index (CTAIDI), customer average interruption frequency index (CAIFI), average service availability index (ASAI), customers experiencing multiple interruptions (CEMIn), energy not supplied (ENS), average energy not supplied (AENS), average customer curtailment index (ACCI), average system interruption frequency index (ASIFI), average system interruption duration index (ASIDI), average interruption time (AIT), average interruption frequency (AIF), average interruption duration (AID), momentary average interruption frequency index (MAIFI), momentary average interruption event frequency index (MAIFI_E), and customers experiencing multiple sustained interruption and momentary interruption events (CEMSMIn).