Setting Calculation Method of Microcomputer Protection for Main Transformer of Coal Mine

A setting calculation method of microcomputer protection for mine-used main transformer was introduced with an example of a main transformer of a large-scale coal mine. Firstly, the short-circuit current was accurately calculated by normalized value method and verified by MVA method, then setting values of differential protection and standby protection were calculated separately. The practical running result showed that the setting method can cut off fault point sensitively, reliably, quickly and choicely.