Automatic monitoring of isolation state in low-voltage distribution network

Abstract

The article discusses the possibility of using the proposed functional isolation monitoring circuit with an additional high-frequency signal of 3500 Hz, introduced into the power network, which allows real-time detection of isolation leakage current not exceeding 8,5 mA. To check the isolation state it was decided to control leakage currents. To do this it is proposed to use the current control device developed by the authors that provides measurement of the currents in the lines and used by consumers. The device makes it possible to determine the magnitude and locations of the unauthorized taking away the power and to transmit the data to the control station wirelessly. It is proposed to extend the functionality of the device by automatically measuring leakage currents when monitoring the isolation state if current exceeds the permissible limits. This can be achieved by introducing a current control device of frequency-dependent selective amplifier of sinusoidal leakage currents that solves the problem of frequency separation and allows the isolation state control without disconnecting users from the network. Early detection and removal of defects of isolation before they become interfacial short circuits and dead ground short circuits will prevent the occurrence of dangerous situations, increase the reliability and service life of electrical networks and ensure uninterrupted power supply of consumers with electricity