DETERMINING THE FACT OF A BREAK IN THE NEUTRAL WIRE IN NETWORKS AND ASSESSING THE MAGNITUDE OF POSSIBLE OVERVOLTAGE BASED ON THE ANALYSIS OF CURRENT SIGNALS ONLY

The use of microprocessor technology in automatic circuit breakers for protecting electrical networks allows several different types of protection based solely on the analysis of system currents to be combined in the release mechanism. This paper proposes a method for determining the fact of a zero wire (neutral) break in a four-wire power supply system and calculating possible overvoltage at consumers, based solely on the analysis of load currents at two adjacent moments in time. A formula is derived showing the equality of relative changes in phase currents during a neutral break, based on which the neutral zero offset voltage is determined and an estimate of the magnitude of phase overvoltage is given. To increase the reliability of determining the fact of a neutral break using the method described above, an additional method is proposed, based on the summation discrets of simultaneously counted three phase currents, which allows the fact of a break to be determined directly at the moment of the incident. An algorithm for constructing protection against overvoltage in the event of a neutral break is considered, which can be implemented in the circuit breakers of relay protection.