| With the rapid development of China’s industry, local air pollution is increasinglyserious. Since the nineteen ninties, large area catastrophic power grid fog flashoverevents occurred frequently in a large range in the country, which is a serious threat tothe safe operation of power system. Although some influences of the fog to the outerinsulation are mentioned in some reference materials, but at present, there is no enoughinformation researching on influences the of natural fog to the insulation of electricalequipment. Accroding to theoretical analysis, simulative and natural tests in the fog ofrod-plane short air gaps, This paper researched on the AC(DC) discharge characteristicsof rod-plane short air gaps.Discharge characteristic of the air gaps in natural fog are researched in this papermainly by laboratory simulation tests and natural environmental test. By simulatingnatural fog environment in the artificial climate chamber,5~15cm rod-plane air gapsfog discharge tests were studied under AC voltage. By the establishment of the10cmrod-plane air gap spacing field model under35kV AC voltage, this paper usedCOMSOL simulation software to analyse the influences of dewdrops, water film andwater droplets on the stick electrode to the rod-plane air gaps discharge characteristics;The natural tests were researhed on5~20cm rod-plane short air gaps discharge underdifferent AC(DC) voltages, the influences of environment temperature, natural fogvisibility on rod-plane short air gaps discharge characteristics are analyzed.Laboratory simulative tests and simulation results show that: the water content ofthe fog can largely impact the gap discharge voltage, when the fog water content is inthe range of1~3g/m~3, the discharge voltage increases with the increase of fog watercontent. When the fog water content is in the range of3~4g/m~3, the discharge voltagedecreases with the increase of fog water content. The discharge voltage decreases withthe increase of fog water conductivity, and the impact inreases with the increase of fogwater content. The fog water content is higher, the complex dielectric constant of thedischarge gap increases more with with the increase of fog water conductivity.Simulation research results show that: with the increase of the fog water content,the droplets on the surface of electrode end can lead to serious distortion of the spatialdistribution of surface electric field, and the water droplets is bigger, the electric fielddistortion is more serious, leading to enhanced local electric field, and the maximumfield strength increases, which promotes the development of discharge, so that therod-plane gap AC discharge voltage drops.The natural fog tests show that: natural fog rod-plane air gaps AC dischargevoltages and positive DC discharge voltages are both linear with the gap distance, and are a relationship of negative index power function with the environmental temperature,also a relationship of positive index power function with the natural fog water content. |
