Oil Filling Procedure for Power Transformers
1. Preparation:- Ensure all components are properly installed and inspected and Verify that all safety protocols are in place, including grounding and isolation of the transformer.
2. Vacuuming:- Connect the vacuum pump to the transformer ( the upper inlet of the main conservator) or as per manufacturer recommendations. Ensure all valves connected to the main body are open( radiator valves, buchholz valve, etc), and other valves to be closed .>ensure to open the equilibrium valves between the main conservator and the OLTC conservator tank in order to vacuum the OLTC tank at the same time.> ensure all bolts and connections are tightened and torqued before starting.
Vacuum Process:-
1-Start the vacuum pump and monitor the vacuum pressure.Achieve a vacuum level of less than 133 Pa.Maintain the vacuum at minimum level as we can for a specified duration to remove moisture and gases.
2-Monitor the vacuum level to ensure there are no leaks. If leaks are detected, identify and repair them.( A steady increase in pressure indicates a leak)repairs :(Tighten all bolts and fittings at the leak site , and if still leak in a place May be you should replace the gasket)
3.-Oil Filling and Filteration > Making BDV test before filling > Heat the transformer oil to the recommended temperature and filter it to remove impurities by using a filteration machine > Begin filling the transformer with oil under vacuum conditions to prevent air bubbles. and at low speed less than 4000 Litres/Hour> Monitor the oil level and temperature continuously.
>Ensure the oil is filled to the correct level as per the manufacturer’s specifications ( in our transformer the level was 70% of the main conservator Note that you may face problems while filling such as the level stay as it is no change you so you should
A) try hitting the conservator by using a wooden piece because may be the floating element of the Guage may be stuck in someplace.
if that doesn’t work try Solution B👇
B) open the vent valve of the buchholz relay slowly and close the vent again you will notice the level go down again and continue the filling process.after main tank oil filling start filling the OLTC tank.after finishing oil filling connect the other outlet of the filteration machine into the upper point of the main Tank and make filteration circulation (duration 24 hours)after finishing wait about 12 hours until the oil temperature go down and perform these tests
👇Test the oil for dielectric strength BDV test.take 2 samples one of them from the middle and the other from upper point and send it to lap to make a Dissolved Gas Analysis (DGA) to check for any gases dissolved in the oil.No alternative text description for this image