Compared with general circuit breakers, Earth Leakage Circuit Breaker applicable to harmonics and surge has earth leakage current detecting characteristic which hardly occurs unnecessary tripping against harmonic waves and surge. For harmonic waves, an active filter is provided in the leakage detecting electronic circuit, and therefore superimposed harmonics are eliminated without interfering with little earth leakage detecting signal of fundamental frequency. This is why the earth leakage current detection is hardly affected by earth leakage of harmonics. For surge, we use a proprietary "DPDC surge discriminating circuit" which eliminates unwanted operation such as earth leakage current to surge absorber installed between the ground for induced lighting and overcurrent protection ,but keeps ground detecting performance.