Research On Correlation Among Equivalent Salt Deposit Density, Relative Humidity And Leakage Current In Artifically Polluted Insulators

Pollution flashover is one of serious accidents that damage safety of power system, anti-pollution flashover is the key point of power department. Recently, pollution flashover accidents in China happen continuously, which is a severe threat to safety operation of power system. Success ratio of reclosing by pollution flashover accidents is quite low, producing outage in large area and long time, the loss electric quantity can reach tens of thousands even tens of millions degree electric, by and large, the damage by large area outage during pollution flashover can not be estimated.Leakage current has close relationship with development procession of pollution flashover, whose variation characteristics can synthetical reflect influence on pollution flashover by each factors, so it has significant meaning to research on leakage current for anti-pollution flashover. Recently, research on leakage current domestic and overseas is quite a lot, but most of them are limited to relationship between leak of leakage current and pollution flashover voltage, factors such as relationship between salt density, relative humidity has not been deeply researched on.Leakage current measurement method on contaminated insulator at different humidity was introduced in this paper.Factors effecting leakage current measurement were approached such as transformer capacity,measuring instruments,sampling resistor,grounding mode of shielding,humidifying duration,etc. Based on the above, test research is done from five aspects: (1) character of leakage current by 7×XP-70 under normal atmospheric conditions; (2) influence on leakage current by operation voltage, temperature difference and frog under saturation humidity;(3) relationship among leakage current of 3×XP-70, equivalent salt deposit density and relative humidity; (4) relationship between leakage current of 5×XP-70 and equivalent salt deposit density; (5) relationship between leakage current waveform and discharge phenomena. Results illustrate that: operation voltage, temperature difference, frog and shape of insulators all have relationship with leakage current, maximum value of leakage current by 3×XP-70 insulators increase by linear relationship with equivalent salt deposit density, increase by nonlinear relationship with relative humidity. Relative humidity has huge influence on leakage current of insulators, so air relative humidity at the time should be taken into account when monitoring leakage current online, which reflects surface pollution conditions of insulator.