Research On Selectivity Leakage Protection Theory And Application For Underground Low Voltage Distribution Network

The selectivity leakage protective system can give out alarming signal or cut off the fault branches selectively when the leakage fault happens, and the non-fault branches are working normally. It can reduce the power-off range and be facilitate to look far the fault, shorten the power-off time, and raise the reliability of power distribution. Based on the actual leakage-protection system for underground low voltage distribution networks, this paper advance a new scheme which based on additional DC power supply and direction of zero sequence power, and PIC16F877A is the core. And introduce the realization of protection device based on this new scheme. This device use the principle of additional DC power supply in main feeding switch, and use the principle of direction of zero sequence power in branch feeding switch. It can improve action capability of Leakage-protection for low voltage distribution networks, consequently improve security of Underground work.