Estimation of station blackout frequency in FBTR

Full text: In this paper, station blackout (SBO) frequency is computed as a function of blackout duration based on available data in FBTR. The frequency of loss of offsite power (LOSP) at FBTR is found to be 5.2/year. The data on the LOSP and failure data on feeders and transformers at FBTR are used to arrive at the frequency of LOSP as a function of down time for single feeder and double feeder cases. The non-recovery probability of offsite power failure with time is well represented by exponential distribution for times less than 2 h and Weibull distribution beyond 2 h. The unavailability of onsite emergency power supply was evaluated using Markov method and fault tree method and is 1.0E-2 and 3.34E-3 respectively. Using the above data and the non-recovery probability of DG, frequency of SBO at FBTR with single feeder and double feeder cases, for different time durations were evaluated. It is found that the frequency of station blackout at FBTR with double feeder computed using Markov method is ∼10-4 /yr for 11 h and 10-5 /yr for 19 h duration. With one feeder out of service the SBO frequency is more by a factor 5. Sensitivity study done with respect to DG repair time and common cause failure indicate that the results in the magnitude of SBO could be uncertain by a factor of ten. The uncertainty is less for shorter SBO duration and more for longer SBO duration