Selection of a Ground-Fault Feeder Using a High-Frequency Transient Component

Medium-voltage electric networks (ENs) with an inefficiently grounded neutral in many countries of the world have significant total lengths, numbering hundreds of thousands and even millions of kilometers. Due to the large length of ENs, various kinds of damage occur in them, the most common of which are single-phase ground faults (SPGFs). Although this mode is quite acceptable, since it does not interrupt the power supply, the search and repair of insulation damage is inevitable. To select a damaged feeder, zero-sequence currents are usually used, which are measured by means of zero-sequence current transformers (ZS CTs). In cases in which such transformers are not available, it is proposed to use an alternative method in which selection is carried out according to the intensity of transients in the simplest sensors installed in the middle part of the feeders. The essence of the method lies in registering high-frequency transient oscillations that occur in sensors when electromagnetic waves with a steep front are incident on them, formed in the EN during the SPGF. The greatest intensity of the transient process occurs in the sensor of the damaged feeder. Information from transmission line measuring devices (sensors) is collected by telemeasurement channels and processed in the simplest way in the processing unit (center). The proposed method is fundamentally suitable for ENs with any method of ineffective grounding of the neutral. An experiment conducted on a 10-kV air power station demonstrated the operability of the proposed method.