Study On Data Processing Method Of On-Line Monitoring Zno Surge Arrestors

It is obvious that the state of Metal-Oxide Arrester (MOA) on-line have to be detected in order to prevent them from abnormal work, especially the resistive component of the continuous leakage current to be detected, which is a good indicator of the MOA condition. Several ways of monitoring the state of a MOA in service have caused some measurement error unexpected. The problem has been highlighted by worldwide researchers in the field because of its great value on both academic theory study and practical application.According to simplified equivalent circuit of ZnO element, the effectiveness of judging the operation conditions of ZnO surge arrester by means of detecting the resistive leakage current is discussed. In this thesis, the conclusion is that the resistive leakage current in the bottom of arrester is weighted average of resistive currents in every part of surge arrester, it reduces the effectiveness of the judgement to large extent. The stray capacitance affects the effectiveness extent of detecting the resistive leakage current to certain extent only. Based on characteristic and equivalent circuit of ZnO element, I analyse the main existing method for on-line monitoring ZnO surge arresters.MOA is disturbed by various factors, such as the harmonic voltage of power network, the hysteretic volt-ampere characteristics and the coupling current components among ZnO surge arrester. The validity of existing methods used to monitor the resistive leakage current of ZnO surge arrester is analysed in this thesis. The resistive leakage current obtained by all of existing methods are influenced by the factors above mentioned and the errors might be rather big under some circumstances. Using the software suggested in the thesis, the correct resistive leakage current can be obtained under disturbing factors above mentioned and be the same as the experimental results.