Optimal routine test intervals for pilot protection schemes using probabilistic methods

The main purpose of this paper is to estimate the optimal routine test interval (ORTI) and to compare the abnormal unavailability index (AU) for several configurations of pilot protection schemes using the Markov model and event tree method. A Markov model of several protective devices, in which operating statistics are taken into account, are combined to form several pilot protection schemes using the event tree method. The pilot protection scheme and its protected component are combined to complete an inspected system. Then, AU and ORTI for each inspected system are calculated. The results show that the proposed method not only can distinguish the difference of several types of pilot protection scheme in terms of reliability, but also can be used to estimate the appropriate ORTI for each protection scheme. In addition, this study should be employed as a guideline to maintain the specific protection scheme