Research And Design Of Comprehensive Power Relay Protection Device Based On Dual CPUs

Microcomputer relaying protection device uses microprocessor to collect the real-time dataof status of power system according to the given algorithm.Then the device determines if thepower system fault occurs or not, the fault character and fault range.Later it will drvie thetripping of circuit breaker or send an alarm signal outside correspondingly. The paper hasdesigned a comprehensive microcomputer relay protection device based on dual processors:TMS320F2808+N78E366A. In the same time, filtering algorithm study, hardware system design,software system development, anti electromagnetic interference analysis and design, deviceperformance test are discussed in this paper detailedly.Research on filtering algorithm mainly compares the performance of different kinds ofmicrocomputer relay protection’s filtering algorithm. Differential full wave Fourier algorithm isput forward by adding a differential segment before the full wave Fourier algorithm,which is ableto eliminate decaying constant current component. This conclusion has been proved by the actualcalculation.With the strict analysis, differential full wave Fourier algorithm is used as the mainfiltering algorithm of the protection device.Meanwhie, the points collected in each cycle is20.The design of hardware system analyses protection CPU unit, analog acquisition unit, digitalinput unit, digital output unit, communication unit, man-machine interface unit and power supplyunit from the hardware selection and schematic analysis. The relization of dual CPU’scommunication, task allocation and peripheral circuit design are also described in this paper.Based on protection function and logic configuration, the development of software systemmainly follows a structured and hierarchical design principles according to the top to down designideas. The paper explores the flow diagram of main program, interrupt service program, faulthandling subroutine, protection subroutine and communication subroutine. And every part isanalyzed in detail description. In order to improve the reliability, the paper discusses and analyze the problem ofelectromagnetic interference of the microcomputer relay protection device. Some specificmeasures for anti-interference are put forward and implemented in the system hardware andsoftware development.Platform for device performance test of microcomputer relay protection device is builtaccording to the simulation test standards.A large amount of test are finished to verify the basicfunction of the device. The conclusions from analysis of the test data shows that themicrocomputer relay protection device’s hardware circuit design is reasonable and softwarefunction is stable and reliable which satisfies the design requirements.It can be expected that with the rapid development of this technology, the new model ofmicrocomputer relay protection device will be more effective and reliable to ensure the safety ofthe grid.