Modelling the influence of preventive maintenance on protection system reliability performance

Abstract

Protection systems exhibit two important types of failures: failures to operate and unwanted operations. Both failure modes have been introduced in a model description designed for the evaluation of the influence of preventive maintenance on protection system reliability performance. The model description is constructed as a continuous time Markov chain. The system states and the transitions be1,ween states are generated in a general and systematic manner which makes it possible to apply the model description to a lot of different situations. Through an example it is shown that (the quality) of preventive maintenance can have significant influence upon 1 he reliability performance of a given system.

Short Term Reliability Analysis for Protection System with Average Unavailability

“…The instantaneous state probability P(t) with the initial value P(t 0 ) at time t 0 is given by (10). With the increasing number of states, it is difficult to solve the ISP by Laplace transform.…”

“…Based on the assumption of exponential duration for the up and the down states with fixed transition rate, the steady-state unavailability is quantified from the Markov transitions [6][7][8], and the optimal maintenance interval and redundancy setting are studied [9][10][11][12][13]. For power systems, the risk level is related to the time-dependent unit outputs, load demands, and network topology, therefore the short-term reliability evaluation with the period of hours/minutes attracts wide attention.…”

Determination of the optimum routine and self‐checking test time intervals for power system protection considering remote back‐up protection system failure

“…In this state, the protected element and also primary and remote back-up protection systems are under normal conditions. When a fault occurs on the transmission line, the model transfers to state (2); and followed by operation of primary protection system, the protected element is isolated and the model goes to state (9). In state (9), the faulted line is repaired and becomes energised again, and the model returns to state (1).…”

“…The ORTTI of transmission line protection system is determined in [8] by considering monitoring test and the back-up protection system is assumed to have zero failure probability. Repair cost variations are calculated by considering repairs frequency in [9] and effect of primary and back-up protection systems on different repair effectiveness indices are taken in to account. In [10], ORTTI has been determined for several configurations of over-current relay protection whereas back-up protection system is assumed perfect.…”