Research And Implementation Of Shorted Fault Indicator For Electric Grid Based On DSP

With the rapid development of power system,power system networks become more complex increasingly,making various faults occur at random,which is a serious threat to the security and stability of residential electricity consumption.However,short-circuit fault occupies large proportion among all these faults.It is very important to install failure indicator on the power line.However,detection speed and accuracy of fault indicator has been always less than ideal,especially for the judgment for single-phase short-circuit fault.The faults for omissions have often occurred.Therefore,it is important to design a safe and reliable fault indicator with high detection speed,high accuracy.And this paper is mainly designed a fault indicator based on DSP.The first part of this paper is to introduce the background and significance of research and analyze research status and development trend of fault indicators on aboard and domestic.According to the principle of the criterion for fault indication,a set of reasonable criterion for fault indication was selected for the accuracy.In the ground fault criterion,for the problem of extracting the 5th harmonic,the main current harmonic amplitude extraction method is combined with wavelet transform and window Fourier transform.This method divides harmonic amplitude extraction process into two parts.The first part peeling unsteady component in sampled signal through wavelet transform,and the second one is determining each harmonic amplitude through window Fourier transform.According to the result of simulation,the method is proved to be feasible.In data processing,DSP was chosen as CPU for the entire control system after comparison,which simplified the hardware circuit of fault indicator and improved analysis rate of the collected data.The entire system can maintain stable operation and ultra-low power consumption when no line fault exists due to the characteristics of DSP,which is ultra-low-power and relatively stability.The program selected TMS320F28335 as the main chip,comparing with other chips,this type occupies faster data processing speed and the ability to solve the large number of floating-point operation,meantime,controlling the cost and increasing the integration.Depend on the overall hardware structure of the entire control system,hardware design of the system,including schematic and PCB,was completed.Then program flow chart and program was designed by analyzing the functions of fault indicator,achieving the transfer and display of extracting current and voltage power direction,harmonic analysis and fault information.In the end,we tested the prototype of fault indicator on phase fault and ground fault.Experimental results show that the functions of fault indicator achieve to the desired results.