Through on-site commissioning of differential digital protection,compared with normal method,single differential protection,zero sequence differential protection and bus differential protection ratio restraint characteristic test method are analyzed and studied and then,some simple, and practical test method and conventional convenience commissioning methods are given.

Discussion on implementation of zero-sequence protection for transformer;

The end earth fault of big power source and long line makes zero-sequence protection appearing serious problem that protecting refused to move because the voltage of zero-sequence is low,and become a new difficult point that zero-sequence protection in practical application.

Study on the misoperation mechanism of zero sequence protection of grounding transformer on low resistance grounded 10 kV system;

It analysed influence and contermeasure of 10 kV neutral point earthing through minute resistance,and put forwards some ways of minute resistance value choice and zero sequence protection allocation.

The influence to the bus equivalent zero sequence impendance and zero sequence protection from the different neutral point earthing mode of the transformer s 110 kV side were specifically analyzed.

The TN-S protective zero terminating in construction site;

This text summarizes the protective zero terminating system of the electric equipments.

Through the analysis of the working principle the danger of breaking of the protective zero line is declared and the advantage of reduplication ground protection is points out.