Power transformer magnetic flow refers to what

The excitation current of the polemounted transformer is only the transformer side of the power supply winding connected to the differential protection circuit, the excitation current is equivalent to the internal fault of the transformer short-circuit current. Therefore, it will inevitably affect the correct work of longitudinal differential protection. Under normal circumstances, the transformer excitation current is small, usually only the substations and transformers rated current of 3% to 6% or less, so the differential protection circuit of the imbalance current is very small. In the case of external short-circuit, the excitation current will decrease due to the voltage drop of the system. Therefore, the influence of excitation current on the differential protection is often negligible in steady state. In the special case of a sudden increase in voltage, it is possible to generate a large field current which is 6 to 8 times the rated current. This transient process of the transformer excitation current is usually referred to as inrush current