Application Research About The Distributed Bus Protection That Bases On Drection Principle In Medium-voltage Power Grid

As one of the most important devices of substation, bus and its protection play a big role in reliable and secure operation of power system. The main target of bus protection is the pursuit of perfect performance, high reliability. This paper takes a sort of bus protection which bases on instant fault power direction as its subject investigated, and starts the studies surrounding the effect of practically running on electric network, the range in point, and performance expending of this bus protection device.Comparing the traditional bus protection, the bus protection based on instant fault power direction has some merits as follow: using self adapting sinusoidal filter to achieve self adapting fault pre-startup, and uses this pre-startup signal to ensure the sensitivity of reflecting bus fault; using sinusoidal approximation processor to confirm the fault startup, and uses this signal to ensure the reliability of bus protection; using proportional brake method to ensure the bus protection unable to misaction when fault out of protected area; using fault current direction to judge and deal with the situation of fault out of protected area of bus change to fault inside, or happening TA fault-line; solves fault power direction according to phase , settle the problems of traditional bus protection which is not according to phase. Distributed hardware structure is adopted for bus protection based on instant fault power direction, it takes the zero-crossing point of voltage as synchronous reference signal, and based on frequency locking and phase locking , using DSP synchronously collect the data of each distance unit; using CPLD to construct data communication server.Contraposing TA saturation will bring serious effect to traditional bus protection, this paper advances a method which can avoid the effect of TA saturation, it seek the instantaneous phase of fault current in 5ms after fault, thereby gain the instantaneous fault power direction of fault phase. Physical simulation of bus protection based on instant fault power direction is conducted under different locations and types of faults, whose results are promising.