Many Electricity boards put the pressure on one of their cleaning problems by using PressureJet high pressure washer in their specially designed equipment to clean high voltage transmission line insulators or live wire insulator cleaning.

TRANSMISSION LINE POLLUTION

Several countries suffer from four types of pollution: industrial, marine (salt), desert and dust pollution. The dust pollution occurs in semi-arid climates where the ground is not completely covered by grass or trees, and the topsoil becomes very dry and is scattered by the wind. It also occurs during construction.

Pollution accretion on dry insulators can result in an insulator flashover. Dry insulators normally have low conductivity, but rain or early morning dew can cause contaminated insulator surfaces to be conductive. The contaminated areas heat up, creating dry bands that occur due to the heating effect of the leakage current. These dry bands interrupt the continuity of the leakage current, and when the voltage gradient exceeds the air breakdown voltage levels, arcing takes place bridging the dry bands leading to a flashover.

Any conventional means of cleaning this residue from the insulators would mean shutting down the lines and interrupting service to homes, offices, schools and businesses.

PressureJet hot line insulator washing truck, which is capable of carrying 4000 to 12000 liters. Each truck is equipped with a hydraulically-actuated boom, 75 to 100 feet long, which is used to get the nozzle close enough to the insulators for effective cleaning of hot wire insulator cleaning.

Time for set-up must be kept to an absolute minimum. The special trucks, built to PressureJet high pressure washer’s specifications, have hydraulic leveling jacks at the rear corners, which are controlled by the boom operator. A unit can be set up quickly, which is critical, considering the many hundreds of set-ups necessary each day for a truck.

Thanks to a unique nozzle developed by the PressureJet engineers, an insulator can be washed in only 15 seconds from just one location without any power interruption.

CLIMATIC CONDITIONS

Prior to upgrading the line from 132 kV to 400 kV, these small outages had no major effect on the line. But, following the upgrade to 400 kV, the voltage stress was significantly higher. As soon as the insulators became wet, bridging of the dry bands occurred, resulting in significant reductions in the overall effective creepage distance. Hence, moisture on the insulators caused significant flashovers to occur along the line, which led to the major blackout. Flashovers and resulting blackouts continued to plague the 400-kV line..

For many years, different contractors greased insulators or used manual dry cleaning to reduce pollution buildup, but these methods were expensive in terms of manpower and outage time. Furthermore, in the last decade, a number of 400-kV and 132-kV transmission lines have been built. Many a time, the transmission lines built. Have anti-fog insulators, whose inner surfaces are difficult to clean using manual methods. Picture shows a polluted insulator before and after cleaning.

227 lpm - 50 bar

Before cleaning		After cleaning

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