Study on Reliability Test Method of Over-load Relay

Over-load relay is widely used for electrical motor protection. Its reliability is becoming more and more important. This paper studies the reliability test method of over-load relay. According to the operation and failure modes of over-load relay, the protective success ratio is adopted as a reliability characteristic value. Based on the reliability estimation method and the sampling theory, the time or failure curtailed test plan is chosen and the sampling and checking plan is designed. By use of the test theory and method and taking the factual application of over-load relay into account, the reliability test process of overload relay is determined. In addition, using the reliability tester developed by ourselves, the reliability test for typical products is carried out.