1. inject oil into transformer or currect transformer 2. by vacuum way, do not pollute ... oil into oil-filled transformers, current transformer, and also used to oil for 110-500kv transformer, canula, on load tap changer ... the upper part of metal expander of the instrument transformer is pumped to high vacuum by vacuum pump, automatic ... 30m Pumping rate of vacuum pump 2L/S Vacuum of vacuum pump ≤666Pa