| The online monitoring technology has been continuously used to ensure the safe operation of the power grid and electrical equipments such as Metal Oxide Surge Arrester(MOA)—an important guarantee of power grid’s safe operation. Meanwhile, the monitoring technology is now transforming from traditional routing inspection into online monitoring, and the working status of MOA is inspected by the online monitoring system in real time. Since MOA is usually used outdoor, its online monitoring is subject to various factors. Hence, the study on factors affecting the online monitoring of MOA to explore the criterion for faults of MOA is very necessary.This paper conducts detailed research into the criterion for identifying the insulation fault of 110 k V MOA. The orthogonal variable based screening algorithm for MOA resistive current is adopted. This algorithm is capable of extracting resistive current just when the total current is monitored by the online monitoring system. In this case, the problem caused by the difficulty in extracting current from a voltage transformer(TV) with the presence of MOA is well solved, and this is really cost-saving. Moreover, its accuracy has been proved through a series of experiments conducted in this research.After the establishment of platform in the lab for the experiments, the AC Current Leakage Experiments are carried out to MOA with varied patterns under the simulated condition of normal voltage fluctuation. Then, the information about the fluctuation of total current and resistive current collected by the online monitoring system under the circumstance of normal voltage fluctuation is analyzed, and finally, the influence of normal voltage fluctuation upon the online monitoring of MOA is presented.The effects of three environmental factors as temperature, humidity and pollution on the online monitoring of MOA are also studied. Typical dump surface of MOA and various environmental temperatures are simulated, and MOA online monitoring system is applied to supervise the changes of total current and resistive current. Next, the curve reflecting the changes of total current and resistive current of MOA grounded on different temperatures and damping levels is obtained. Besides, the effects of different pollution levels of MOA surface on the online monitoring results are investigated through the pollution experiments of MOA surface.As regards Y10W-108/281 MOA with porcelain cover, fresh water is infused to MOA to simulate the internal damping condition. Furthermore, resistance furnace is applied to heat MOA valve disc to simulate the burn-in fault of MOA. The curves illustrating the change trend of I75%U1m A, total current and resistive current in line with the humidity level and burn-in degree are drawn with the results gathered from the online monitoring system and DC Current Leakage Experiments. A certain pattern of MOA is identified as having faults if I75%U1m A value reaches 50 u A. According to this point, the values of total current and resistive current collected under the online monitoring system of this MOA are achieved. Consequently, the criterion identifying the faults as damping and burn-in of MOA is found.In order to eliminate the effects of environmental factors on the earth-sized on-line monitoring based on BP neural network algorithm for ceramic coat earth-sized Y10W-108/281 defect diagnosis model is established, the model is verified by the simulation can effectively eliminate the interference of environmental factors accurate judgment earth-sized was flawed. |
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