Earth leakage breaker and method for controlling earth leakage breaker

A method for controlling an earth leakage breaker formed between three-phase electrical lines and a single-phase load connected to two electrical lines of the three-phase electrical lines, the method comprising:

• a first step of detecting a zero-phase current generated in a zero current transformer formed in the three-phase electrical lines;
• a second step of detecting whether electric leakage or ground fault has occurred according to whether the detected zero-phase current is greater than or equal to a predetermined set value;
• a third step of detecting voltages of each of the two electrical lines when ground fault is detected as a result of the detection in the second step;
• a fourth step of detecting whether there is an electrical line in which voltage has dropped by predetermined level or more based on a result of the voltage detection in the third step;
• and
• a fifth step of tripping contact points between the two electrical lines and the single-phase load based on a result of the detection in the fourth step,
• wherein the second step is a step of,
• when a magnitude of the detected zero-phase current is greater than or equal to a predetermined set value, determining that the zero-phase current is caused by ground fault, and
• when the magnitude of the detected zero-phase current is less than the predetermined set value, determining whether the electric leakage has occurred by comparing a predetermined threshold value for determining whether the electric leakage has occurred with a voltage value of a voltage signal according to the magnitude of the detected zero-phase current.

An earth leakage breaker system, comprising:

• at least one single-phase load supplied with power from two electrical lines among three-phase electrical lines;
• at least one trip unit formed between a single-phase load and the two electrical lines supplying power to the single-phase load and configured to trip contact points between the single-phase load and the two electrical lines supplying power to the single-phase load upon receiving a trip control signal;
• and a system control unit connected to a zero current transformer formed on the three-phase electrical lines and configured to receive a result of detecting voltages of electrical lines connected to each of single-phase loads from the at least one trip unit to thereby transmit the trip control signal to a part of the at least one trip unit based on the received voltage detection result, wherein the system control unit is configured to, when a magnitude of the detected zero-phase current is determined to be less than a set value by comparing the magnitude of the detected zero-phase current with the predetermined set value, determine whether the zero-phase current is generated due to electric leakage based on a threshold value for determining whether the electric leakage has occurred, and when the zero-phase current is determined to be generated due to the electric leakage, transmit a trip control signal to all of the at least one trip unit.