A Study on the Statistical Life Span Estimation of Aged Low-Voltage Circuit Breakers
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ORIGINAL ARTICLE
A Study on the Statistical Life Span Estimation of Aged Low‑Voltage Circuit Breakers Kiseok Jeong1 · Youngseok Kim1 · Chongmin Kim1 · Ohmin Kwon1 Received: 26 February 2020 / Revised: 26 August 2020 / Accepted: 15 September 2020 © The Korean Institute of Electrical Engineers 2020
Abstract In this study, aged low-voltage breakers, including earth leakage breakers (ELBs) and molded case circuit breakers (MCCBs) with high rates of electrical fire occurrences, were collected from a field site and tested according to failure identification test criteria. Based on the International Electro technical Commission (IEC)’s failure judgment test criteria, pass or fail tests include lever repeat operations, the manual trip button for finding mechanical deformations and leakage sensitivity current test, the ELB earth leakage trip time test, and the MCCB overcurrent trip test to verify changes in electrical performance. The fault data obtained from the tests, expressed in years (yr), were analyzed for statistical life span prediction (SLP) using the Weibull distribution probability. The SLP analysis verified the fault data set’s distribution suitability and derived the mean time to failure (MTTF) using the Minitab statistical analysis tool. Sample analysis of aged low-voltage breakers determined that approximately 73% of the samples were found in homes, and their MTTFs were 19–23 year, longer than those suggested in the literature. The predicted life span of an ELB was also approximately 4 yr shorter than an MCCB, possibly due to the mechanical and electrical shock of internal electronic devices caused by the manual trip button test and the deteriorating electrolytic capacitors of some printed circuit boards (PCBs). Keywords Earth leakage breaker (ELB) · Molded case circuit breaker (MCCB) · Statistical life span prediction (SLP) · Failure judgment · Weibull distribution probability · Mean time to failure (MTTF)
1 Introduction Low-voltage (380/220 V) electrical fires account for about 75% of total accidents, and low-voltage breakers like earth leakage breakers (ELBs) and molded case circuit breakers (MCCBs) account for 13% of them [1]. It is difficult to protect and manage low-voltage facilities because the durability or replacement cycle of a low-voltage circuit breaker is often not up to par with high-voltage facilities, which explains its lack of support. Research on efficiently managing lowvoltage electrical facilities, determining replacement timing, and preparing guidelines for reducing electrical fires is required [2]. The proposed life span of an ELB is 15 yr based on the Japan Electrical Manufacturers’ Association’s (JEMA) * Kiseok Jeong [email protected] 1
Electrical Safety Research Institute, Korea Electrical Safety Corporation, 111, Anjeon‑ro, Iseo‑myeon, Wanju‑gun, Jeollabuk‑do, South Korea
survey report on the life span and maintenance of electrical plants in 2006, which was lowered to 11 yr based on an article about improving the life span of low-voltage breakers in 2009 [3, 4]. For MCCB
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