Electric system protection device for transformer substation

The invention provides a electric system protection device for a transformer substation. The electric system protection device for the transformer substation comprises: a first current transformer, a second current transformer, a differential protection unit, and an over-current protection unit. The first current transformer is connected with a high voltage circuit breaker to obtain a first to-be-measured current, selects a transformation ratio of the first to-be-measured current in accordance with a rated current, and outputs a first transformation current; the second current transformer is respectively connected with the first current transformer and a high voltage transformer so as to obtain a second to-be-measured current, selects a transformation ratio of the second to-be-measured current in accordance with the rated current, and outputs a second transformation current; a first port of the differential protection unit is connected with the first current transformer so as to obtain the first transformatio