Research on DC grounding finder to effectively prevent microcomputer protection malfunction caused by one-point grounding of secondary circuit

Abstract

The problem of protection malfunction caused by one-point grounding of the secondary circuit has received extensive attention, which have been updated in several domestic industrial standards, but the problem of microcomputer protection malfunction due to one-point grounding of the secondary circuit still occurs frequently during operation. According to the analysis, with the comprehensive promotion of microcomputer protection, low-power operating element have been used on a large scale, which makes the grounding resistance of the DC system larger. The relevant parameter setting, principle design and specification requirements of the original DC grounding finder have not been taken into account, which leads to frequent occurrences of secondary equipment malfunction in the DC grounding search process. In-depth analysis of the typical grounding situation showed that the detection resistance value of the existing DC grounding finder is too small, and when both positive and negative electrodes are grounded with high resistance, protection malfunction caused by DC grounding finder may occur. According to the asymmetric characteristics of existing secondary circuits, an asymmetric DC grounding finder was designed, with a strong anti-protection malfunction ability, it was verified by actual measurement that the detection sensitivity of the instrument on ground resistance was improved by more than 50%.