Influence of Slight Current of Long Time Continuous Lightning Surge on Operation of Earth Leakage Circuit Breaker

摘要

As earth leakage circuit breakers are being increasingly installed at the service entrances of low voltage consumers, more reports have been made of unnecessary operation (hereinafter called a false operation) induced by lightning at the time of a lightning strike. As such false operations could cause unexpected service interruption to low voltage consumers; counter-measures therefore are an important requirement nowadays. The author has researched the causes of lightning induced surge false operations of earth leakage circuit breakers and their generation mechanism. And as a result of such research, it has been revealed that the magnitude of the electric charge of the lightning induced surge current which flows in the ground return circuit at the time of a lightning strike is largely related to the generation of false operations. However, the wiring in low voltage house wiring is complicated and the mode of lightning induced surges penetrating into the circuit also varies. Therefore, studies were carried out in this thesis on the influence of lightning induced surges with a long wave tail in micro surge currents, which last for a long period of time, on the generation of false operations. These studies disclosed that since the change of current with time (di/dt) at the wave tail of a surge current with a duration of 1 ms or longer, is smaller than that at the wave front, the voltage generated in the secondary side of a zero-phase current transformer is low. It was confirmed from this that an even greater charge will be necessary for the ground return current to cause a false operation than for a surge with a duration of less than 1 ms.