Yong Jun

Investigation on hydrophobicity and pollution status of composite insulators in contaminated areas

The usage of silicone rubber insulators in various contaminated areas has increasesd prominently and still keeps rising. In the case of China, more than 90% of the 800000 composite insulators are operating in heavy or medium pollution environments. As the exposure time in the field is prolonged, the change of hydrophobicity and the build-up of pollution layer directly affect pollution performance of the composite insulator. The paper is based on part of the work of a system investigation aiming at inspection and evaluation on pollution performance and aging of the composite insulator in service. More than 40 composite insulators, all made of HTV silicone rubber, were removed from 110 kV-220 kV HV lines. The service time changes from 1 year to 10 years. Hydrophobicity status and pollution status of these insulators are reviewed in the paper. Data from the field provide important references for the research on aging and pollution property and for the build-up of relevant test methods.

Influence of shed profile on the outdoor insulation performance of polymeric insulators

Wet tests, dry tests and artificial pollution tests were carried out to investigate the influence of shed profile and shed arrangement on the outdoor insulation performance of polymeric insulators. The sample insulators characterized almost the same insulation distance but prominently different shed diameter and shed space, therefore various leakage distance on a large scale. Considering the wettability of polymer insulators, both hydrophobic status and hydrophilic status were simulated in the tests. It is found that shed profile and its arrangement have prominent influence on flashover voltage of polymeric insulators under wet and pollution conditions. Moreover, leakage distance is not the sole crucial parameter to describe pollution performance of insulators. Increasing leakage distance in a limited insulation distance by excessively adding the number of shed and enlarging shed diameter may contrarily lower the wet and pollution performance of polymeric insulators.

Detection and processing for ±660 composite insulator abnormal discharge

Composite insulators are used greatly in±660kV DC transmission line, which influenced by external factors such as strong electric field, acid rain or mist, wire load and temperature shock, leading to the degradation of insulator, hydrophobic performance decline and mechanical strength reduction, and furthermore insulator abnormal discharge and other issues are also increasing year by year. In this paper, multi-spectral detection technology is presented firstly, containing visible light, infrared and ultraviolet detection technology. Visible light, infrared and ultraviolet detection technology each has its advantages and disadvantages, and multi-spectral method combine the three effectively, to improve the detection accuracy of composite insulator abnormal discharge obviously through the horizontal and vertical contrast. Discussions from detection principle to conditions are continued. Detecting instrument selection and configuration should be based on unit, equipment, management scope, voltage level and other actual situation, to meet the requirements of accurate detecting. Ideal detection should be carried on at clear night, while the wind speed is 0.5 m/s or less and humidity 85% or less, without electromagnetic interference or background radiation interference, focusing on the umbrella and sheath of composite insulator close to wire. Practice shows that the method can detect abnormal discharge effectively, which are more accurate than signal detection technology. For actual abnormal insulator detected, characteristics of visible image, infrared imaging and UV imaging are described, which are closely interrelated from each other. Composition analysis of surface contamination indicates the presence of water soluble ions in high concentration is primary factor in abnormal discharge. For abnormal discharge problem of composite insulators, the paper also presents a new type of DC composite insulator that uses large-floral-umbrella type, which improves electric field distribution of insulator surface, but also improves the creepage distance. Actual operation shows that such insulators operate in good condition, without abnormal discharge situation.