Monitoring in 6–35 kV power networks, location of single-phase ground fault and detection of fault feeder

Abstract

To minimize the negative impact of arc overvoltage in three-phase electrical power system (ES) with the ungrounded or high impedance grounded neutral, it is proposed to monitor transient electromagnetic processes, which will allow evaluating the current condition of the insulation, and in addition, detecting the damaged feeder and a single-phase ground fault zone using telemetry systems. Detection of the damaged feeder (with a single-phase ground fault) using the parameters of the ground fault transient process can be incorrect due to low free oscillations frequencies of electromagnetic instrument voltage transformers (EMVT). The superposition of EMVT free oscillations on the ES oscillations leads to an incorrect determination of the power direction of the first high-frequency oscillations and, as a result, to incorrect detection of the damaged feeder. A more accurate detection of the damaged feeder can be done by the proposed method based on the processing the pre-breakdown voltage of power frequency in the damaged phase. It is shown that the method is suitable for networks with an isolated neutral, as well as grounded through an arc-suppression reactor (ASR) or a high-value resistor.