Studies On The Error Mitigation Method Of On-Line Insulation Monitoring System Of MOA

The measurement precision of dielectric loss angle is a key factor of the performance of on-line monitoring system of metal-oxide arresters. The causes of data error of on-line insulating monitoring system for MOA are introduced in the paper. Questions about harmonic interference and surface contamination in on-line monitoring insulation system of MOA are stated, this paper will research on how to improve the measurement precision of dielectric loss angle.For the effect of harmonic interference in on-line monitoring insulation system, a new method of improving correlation coefficient calculating is presented, which has advantage of high precision. This new method firstly designs a notch filter to process the signal and secondly uses the correlation coefficient calculating to calculate the dielectric loss angle. Moreover, a harmonic interference error correction method based on BP neural network is presented for for modifying dielectric loss angle.This method is used to identify the nonlinear relation between 3nd, 5th harmonic and dielectric loss angle modified value △δ through BP network, finally the adjusting dielectric loss angle model based on BP network is gained. The dielectric loss angle modified value △δ ,which can be got from the adjusting model, is used to modify the measured value of dielectric loss angle. The results from tests and simulation show that the two methods above-mentioned have a good results on eliminating harmonic interference error.Contraposing the effect of MOA surface contamination on measuring dielectric loss angle, The salt mist artifi cial pollution test is presented, by which we can research on the relation between surface contamination degree and dielectric loss angle measurement error. Functional relation between the dielectric loss angle modified value and salt deposit density (SDD) is obtained though least square method. By this functional relation, the adjusting dielectric loss angle model based on least square method is gained. we can get the modifiedvalue of dielectric loss angle from it. This method is testified to have advantage of high precision for measuring dielectric loss angle and to have good effect on eliminating measurement error which is imposed by surface contamination through experiment in laboratory.