Research On Application Of Online Insulation Monitoring System For Capacitive Apparatus Based On Wavelate Analysis And Improved Harmonics Analysis Algorithm

High voltage capacitive apparatus plays a very important role in power systems, on-line monitoring of the insulation condition for capacitive apparatus can ensure the reliability by finding out the latent troubles and preventing accidents, and is the most important approach that ensure power system running safely, steadily and reliably. Dielectric loss angle is an important parameter to reflect its insulation condition, present algorithms of calculating dielectric loss angle which is very subject to the influence of electric noise and harmonic often have great errors, and them can't meet requirements for the real-time monitoring of high voltage capacitive apparatus. Therefore, it is important to develop a improved algorithm with high precision and stability.Based on the analysis and comparison of diversified algorithms of capacitive apparatus's insulation online supervision, an algorithmic routine of dissipation factor based on wavelet analysis and improved harmonic algorithm is presented, considering influence of electric noise and harmonic. Firstly, since low pass filter can't differentiate between high frequency part of useful signal and high frequency part of noise, Wavelet threshold de-noising method reducing the white noise from the signal collected by on-line monitoring system is proposed. Furthermore, wavelet function, decomposition level, threshold value and threshold function are selected, according to characteristic of the signal collected by on-line monitoring system. Secondly, based on the analysis of diversified algorithms of dielectric loss angle, an improved algorithm based on calibrated integration interval by linear interpolation and trapezoidal integration or Simpson integration which replaced the rectangular integration is presented. The problem, measurement accuracy will be influenced by leakage error when the sampling frequency was not synchronous with power network signal's frequency, is solved.Finally, a software of on-line monitoring system for high voltage capacitive apparatus based on LabVIEW is developed, using wavelet analysis and improved harmonic algorithm. The simulation results and experimental results verify the effectiveness of the new algorithm.And this algorithm has the positive meaning for enhancing system performance.