1)3 to 4 litres of oil needs to be let out before collecting the oil sample.
2) oil sample from Transformer before filtration.
3) The gap between the test electrodes must be 2.5mm.
4) The oil can withstand 40kV for a minute if it is having good dielectric strength. Voltage should be gradually increased from zero.
5) At one point Flash will take place and that point is termed as Bread down Voltage
In Oil filtration process, the oil passes through three chambers in the oil filter.
They are 1.Paper Filter, 2.Heater, 3.Vacuum Chamber
Paper Filter removes carbon particles from the oil. Heater & Vacuum Chamber removes moisture content from the oil. Mainly transformer oil is used for insulation purpose. When the oil contacts with atmospheric air in the conservator, the air moisturize the oil and reduce its dielectric strength. So, the transformer oil should be filtered once in a year. This process should repeat at least for 6 to 7 times.
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