Study On Improving Operational Reliability Of Microcomputer Relay Protection For Zhaocun Substation

The microprocessor based protective relay works in serious electromagnetic environment of the substations. It simmunity level and reliability is more important to the safe and reliable operation of the power systems. The microprocessor based protective relay has exceeded the concept of the traditional protective relay. The trends for the microprocessor based protective relay are the computerization, artificial intelligence, networking, the integration of protective relay, control & measuring and data communication technologies. The computer hardware and software design has been more complicated.With regard to EFT/B's forming mechanism, the process of forming EFT/B caused by a switch operation is studied at first. Then, the restrike and extinction model of adisconnecting switch's arc is built with EMPT ATP codes. EFT/B caused by adisconnecting switch's cutting off in ductive or capacitive load is simulated in the primary circuit of power system. Counter measures of MOV(Metal Oxide Varistor), RC and phase-control switch technology are used to inhibit the primary circuit EFT/B. EFT/B's forming mechanism in the secondary circuit is studied through experiments. It's discovered that EFT/B coupled into a relay's coil interferes with DC power supply of microprocessor protection devices badly. And a model of output relay is built. The method of electromagnetic shielding is simulated to cut off EFT/B's path from the relay's contact to its coil.This paper abserved and compared the voltage waveform of each detected point by the oscilloscope. The transmission path of the transient disturbance in Zhaocun electric substation is found out. And then method of enhance the anti-interference level of microcomputer relay protection device is defined. The algorithm based on datamining technology is tested to predict and analyze the electromagnetic environment to fasubstation. Simulations to test the quantitive study of EMI (Electro-magnetic Interference) source and its coupling path is proceeded. The planeis tested to be correct and feasible.