适应波达时刻不确定性及较低采样率的新能源送出线路就地暂态量主保护判据OA北大核心CSTPCD

Asymmetric ground fault accounts for more than 90%of all line faults,and ground distance protection plays an irreplaceable role in dealing with such faults.However,with the high penetration of new energy,it has become a consensus that the performance of various traditional single-ended power-frequency based protection has significantly declined.The protection criterion based on the line mode vs zero mode wave velocity difference of fault components only needs to use the arrival time information of the fault initial traveling wave theoretically,which allows it to become a simple and reliable single terminal quantity fast protection criterion.Until now,it has been successfully applied in the DC power grid.However,when trying to apply this type of protection to the AC power grid,it is discovered that numerous adverse factors,such as the steep wavefront,hinder accurate determination of the wave arrival time.The reliance on high sampling rates and other factors result in an excessively large fuzzy discrimination zone,rendering this protection unsuitable for most lines,except for extremely long ones.Accurately identifying the wave arrival time is a complex nonlinear problem,and employing artificial intelligence-based methods for identification presents a feasible solution..In order to solve the above problems,a new single-ended transient based main protection criterion is proposed in this paper.First,the relationship between the arrival time and waveform is analyzed,and it is pointed out that this relationship can be mapped by machine learning.Next,Gaussian process regression(GPR)is introduced,the sample set is obtained after preprocessing the initial traveling wave data,and the GPR prediction model is input for training.Then,according to the model evaluation index,the optimal training model is obtained to output the highly reliable linear zero mode wave time of arrival difference.By this means,the protection criterion based on traveling wave modulus transmission time difference can be realized.Finally,on the basis of PSCAD simulation tests,the validity and universality of the proposed protection criterion are verified.Furthermore,the criterion is tested using field measured data to verify its practicality.This work provides a new solution for the improvement of single-ended transient based protection under the new energy AC system.