Diagnóstico de contatos de disjuntores baseado na resistência dinâmica de contato e Lógica Fuzzy.

Abstract

This thesis presents a new methodology for evaluation of high voltage circuit breaker contacts, based on the dynamic resistance measurement (DRM) and fuzzy logic. In the DRM tests, a resistance curve is generated, contemplating resistance values referring to the main and arcing contact regions. The tests were performed with minimum oil circuit breaker (MOCB) of 800 A/15 KV/ 12,5 KA, 630 A/ 17,5 KV/ 12,5 Ka and 2.000 A/ 72,5 KV/ 31,5 KA, and a SF6 circuit breaker of 1.650 A/72,5 KV/ 25 KA. To perform the DRM test, a measurement system has been designed and developed, which consists of a 4-channel digital oscilloscope, a stationary battery of 12 V/ 220 Ah, resistors to limit the current from the battery, current and voltage sensors and a personal computer. The system is able to determine the dynamic resistance values since the beginning of the contact opening process until total separation. In this research, an algorithm was developed to extract from the DRM curves, the characteristic parameters: main contact resistance and arcing contact resistance. A FUZZY logic based system was also developed in order to estimate the contacts degradation level as a function of the DRM parameters. From the obtainned results, it was observed that the contact degradation level is directy proporcional to the resistance values, allowing an accurate diagnosis of the main and arcing contacts condition. The application of FUZZY logic allowed the estimation of the contacts degradation level.