It takes a rather long time to remove a dead zone fault occurring between the breaker on a certain side of the 220 kV transformer and the transformer differential protection mutual inductor by means of the supply side of transformer backup protection action or another side of the transformer circuit breaker tripping. As this is a transformer exit fault

it is likely to cause damage to the transformer. An analysis is made of the fault characteristics during 220 kV transformer fault in dead zones on all sides of the transformer and the related protective action features. By drawing on the principles of currently operating bus differential protection in the tie breaker failure protection and the dead zone circuit breaker failure protection

four protection principle schemes of fast removal of dead zone on each side of 220 kV transformer fault are proposed and rational value taking for the dead zone fault protection transformer short delay is studied.