The following preparations should be made:

a. Prepare some clean transformer oil in an amount of 5% - 6% of the oil volume of the transformer;

b. The outlet of the oil-discharging valve at the transformer bottom should match the inlet of the transformer oil purifier;

c. Fill the vacuum tank with clean oil (Dielectric breakdown voltage ≥ 50kV) to 1/2 of the oil gauge mounted on the vacuum separator; if on line regeneration is needed, regenerator must be full of clean oil;

d. Open the oil block cover of the transformer, insert the oil outlet of the transformer oil purifier into the oil breather (below the oil level) and seal the oil breather covering with clean filter paper or film;

e. Insert the oil inlet of the transformer oil purifier into the clean oil;

f. Open the oil-discharging valve at the bottom of transformer to discharge 3% - 5% of the oil (These oil is mainly composed of impurities and water, so it should be discharged and collected separately);

g. While carrying out the above step f, make the transformer oil purifier at high vacuum (not below -0.09Mpa) and immediately replenish oil to the oil level of the transformer’s oil breather;

h. When the 3% - 5% "bad oil" is drained in step f, connect the oil inlet of the transformer oil purifier to the oil-discharging valve of the transformer;

i. Now all are ready for operation.