| Leakage is major fault form in underground power supply system,about 70%in the total fault.Not only does it cause physical electrocution accident,will form a single-phase to ground,and then developed into a short-circuit between each phase, resulting in the arc can cause gas and dust explosion.The use of leakage protective device is mainly used to prevent leakage of the economic losses and personal injury caused by fire,so it is extensive used.The selective leakage protective system can give out alarming signal or out off the fault branches selectively when the leakage fault happens,and the non-fhult branches are working normally.It can reduce the power-off range and be facilitate to look for the fault,shorten the power-off time,and raise the reliability of power distrbution.The current selective leakage protection system is mainly use of the principle of the size of zero-sequence current and zero-sequence current direction in underground. This principle is more difficult to meet the requirements of selective when a line in lines far longer than others(the distributed capacitance is less the same as distributed capacitance of the total system).Protection device may occur the phenomenon of refusal to move,can not be good to complete the purpose of protection.Based on the actual leakage protective system for underground power supply system,this paper advance a scheme which based on additional DC power supply and direction of zero sequence power,and dsPIC30F4012 is the core.And introduce the realization of protection device based on this scheme.The device use the principle of additional DC power supply in main feeding switch,use the principle of direction of zero sequence power in branch feeding switch,and use faster PROFIBUS and Optical Fiber Communication Technology in the device.It can improve action capability and Anti-interference capability of the leakage protective device for power supply system in underground.
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