Estimation of replacement of numerical relay systems from reliability analysis

Reliability Analysis System for Protection Relays (RASPR) is developed by CRIEPI, has been introduced into all of 11 Japanese electric power utilities. RASPR is a powerful tool to study the improvement of maintenance procedure and to investigate the replacement of aged relays based upon the accumulated data. RASPR is mainly composed of the database and the analysis system; in the former part, the equipment data and the failure data can be accumulated. The latter has functions to totalize the various kinds of data, to analyze the reliability, and to analyze the failure rate by Weibull distribution. We have contributed to Japanese electric power utilities through studies on rationalization of maintenance procedure. Already in Japan the period of cyclic testing was extended such as to eight years from six years based on the reliability analysis. This paper describes as follows; 1) the reliability analysis results and Weibull distribution using the accumulated data of 13 years, 2) the estimation of the deterioration for the 1st generation (introduction from about 1985) and the 2nd generation (introduction from about 1994) numerical relays, and 3) the estimation of the replacement of aged numerical relays.