Study on the Discharge Characteristic and Detection Method on the Faulty of Distribution Insulators

The porcelain insulators are widely used in distribution network of China. In order to attach overhead cables on it, the binding wires are used. As the binding wires are bonded on the top of insulator, the discharges can be found in this particular area in some certain circumstances. Once these discharges are formed, they will evolve into insulator flashover and finally cause a single-phase earth fault if the discharge is not prevented. It can be argued that the single-phase earth fault is a serious problem in our distribution network. Meanwhile, the discharge occurs in the top of insulators will also generate disturbing noises and give disruptive influences to the residents nearby. However, if the fault can be prevented from the very beginning by detecting the discharges in advance, none of above will happen. The reliability of distribution network will be improved dramatically. It is clearly to see that a major feature of these partial discharges is their long duration. This paper firstly focuses on the faults of insulator due to its largest quantity and significant fault rate in distribution network. According to the feedback from the distribution network on-site maintenance team, the insulating layer of overhead conductor is often ablated by flashover arcs which are usually generated under the binding wire on the insulators. Therefore, the simulations and experimental study to explain the mechanism of these insulator discharges are performed. This research is based on artificial pollution tests, and the discharges in different conditions/environments (i.e. pollution level, moist, damage and scratch) are reproduced. With ultrasonic, UHF and partial discharge measurement, the relationship between discharge radiation (i.e. ultrasonic and UHF) and partial discharge level in different environment is obtained. According to the obtained relationships, a method of monitoring equipment ageing is discussed.