Transformer cooling device maintenance method

The common faults of the cooling device itself are mainly leakage and blockage during operation, which should be dealt with during the usual maintenance and disassembly overhaul.

(1) The maintenance of the radiator is mainly to weld and repair the leaking oil point. When overhauling, open the upper and lower oil collecting chamber covers, remove the grease and sundries in the oil chamber, and then replace the rubber gasket; clean the surface of the radiator. If the dirt is serious, you can use a detergent to clean it. Rinse it with clean water and dry it to prevent water from entering. If necessary, spray paint. Figure 1 shows a schematic diagram of the oil seal check and flush connections for the radiator.

Transformer cooling device maintenance method
Figure 1 – Schematic diagram of oil seal check and flush connections for radiator

1- hook; 2- pressure gauge: 3- radiator: 4- oil heater: 5- container; 6- pressure oil filter; 7- air outlet funnel

In Figure 1, the radiator is connected to the pressure oil filter through the oil pipeline, and the unused joint flange is sealed with a cover plate, and the internal circulation is flushed with qualified insulating oil, and the pressure is tested for leakage. The applied pressure is: 0.05~0.1MPa for chip radiators and 0.1-0.15MPa for tubular radiators.

After installation, the installation direction of the radiator valve should be uniform, with obvious opening and closing signs, and should be in the open position; tighten the steel and other auxiliary parts. In addition, auxiliary equipment such as fans of air-cooled radiators should be overhauled according to regulations.

(2) Overhaul of the forced oil circulating air cooler. The forced oil circulation air cooler mainly checks the oil leakage point and performs welding repair. During maintenance, open the upper and lower end caps to check whether the cooling pipe is blocked. If necessary, replace the gaskets, and replace the gaskets of the air and oil drain plugs. Figure 2 shows the schematic diagram of forced oil circulation cooler leak testing and internal flushing. When there is leakage in the pipeline, the new pipe can be replaced by the expansion method; when the pipes cannot be replaced, the two ends of the leaking pipes can be blocked with tapered brass rods, but the number of blocked pipes should not exceed two per loop, otherwise the cooler should be used with reduced capacity.

The leak test standard is to add 0.25 ~ 0.275MPa pressure for 30min, and the cooler has no leakage.

Transformer cooling device maintenance method
Figure 2 – Schematic diagram of forced oil circulation cooler leak testing and internal flushing

1-cooler; 2-valve; 3-pressure gauge; 4-oil-resistant hose; 5-flange; 6-pressure oil filter; 7-oil-resistant hose and flange; 8- Oil drum (place clean and qualified transformer oil)

After maintenance, clean the outer surface of the cooler, and use 0.1MPa compressed air or water to blow off the dust, insects, grass clippings and other debris blocked between the tube bundles. If the greasy dirt is serious, it can be cleaned with metal cleaner.

(3) Overhaul of the oil circulating water cooler with strong chasing. During maintenance, close the water inlet and outlet valves, and release the stored water; then close the oil inlet and oil outlet valves to release the body storage oil; remove the upper cover, loosen the connecting bolts between the main body and the water chamber, lift out the main body for a comprehensive inspection, and remove scale and grease. Check the steel pipe and end expansion for leaks. If there is leakage, replace or plug the leakage pipe. When blocked, each circuit shall not exceed two, otherwise the cooler should be used with reduced capacity. When the cooler body (without oil pump) is in the upright position for leak detection, the top of the cooler is filled with qualified transformer oil; inject clean water at the inlet of the water chamber, let the water slowly flow out from the water outlet, observe and test, there should be no oil flowers, and then take the oil sample for test, the pressure resistance value should not be lower than the value before injection.

After inspection, replace the gasket and reassemble. The leak test standard is 0.4MPa and the pressure is 30min, and there should be no leakage. To enable the cooler, the submersible oil pump should be started first, and then the water pump should be started. When deactivating the cooler, the water pump should be stopped first, and then the oil pump should be stopped, so that the oil pressure is always higher than the water pressure, and the cooling water is prevented from entering the oil. After the water cooler is out of use, the water valve must be opened to drain the water, and the water inlet valve must be prevented from being loose and the water will continue to be fed.

Read more: Transformer oil treatment