1 Overview

Differential protection is the main protection of electrical volume to ensure the normal operation of transformer in substation. When the electrical part surrounded by current transformers on each side of the transformer occurs short circuit fault, the protection will quickly remove the fault without delay. If the transformer fault occurs, the differential protection device because of the fault and refuse to move, may cause different degrees of damage to the transformer, or even burn, will greatly affect the safe and stable operation of the power system, in turn, the differential protection device due to fault and misoperation, will cause the abnormal outage of the transformer, affect the power supply of the power system, or even cause the system oscillation, It is very unfavorable to the operation of power system. Therefore, the microcomputer transformer differential protection device failure, should quickly find the reason for processing. This paper discusses the fault cause and treatment of differential protection device of microcomputer transformer in substation.

2 Differential protection device rejection

When the differential protection device is rejected, it is of great harm to the safe operation. This is because the device may be burned if the differential protection device is rejected when an accident occurs. Therefore, it is necessary to determine the cause of the fault and remove the fault according to the fault message and the action of the protection device. Due to different types of transformer busbar connection, so the method of troubleshooting is different, here only describes the general situation.

2.1 General reasons for the refusal of differential protection devices

(1) The functional hard press plate of differential protection device is not put in or the SV soft press plate is not put in;

(2) The setting of differential protection device is wrong;

(3) differential protection device power switch trip;

(4) The positive power supply of hard press plate at the outlet of differential protection device disappears;

(5) TA wire break locking differential protection device;

(6) The power supply board of differential protection device is faulty.

2.2 Inspection and treatment of differential protection device rejection

2.2.1 The hard plate of differential protection function is not put in

If the functional hard press plate of differential protection device is not put in, the staff on duty should verify that the functional press plate has no abnormal voltage to the ground and both ends (or check that the differential protection opening amount is changed from 0 to 1) before putting in; SV platen is not put in, check whether SV switch is put in within the differential protection range (especially pay attention to the internal bridge connection).

2.2.2 The setting of differential protection device is incorrect

If the value setting of the differential protection device is wrong, the staff on duty should first exit all outlet hard press plates (or GOOSE outlet soft press plates) of the jump transformer in the device, and then check and modify the value setting in the differential protection device with the value setting order issued by dispatch (first check the area code of the value setting of the protection device, then check the value setting, and modify the wrong value if found). After the fixed value in the differential protection device is verified to be correct, the personnel on duty should check that there is no abnormal voltage between the outlet press plate and the two ends, and put the outlet hard press plate (or the outlet soft press plate with GOOSE) into the outlet.

2.2.3 Differential protection device power switch trip

If the differential protection device power switch trip, the staff on duty should first use the external meter to check whether there is voltage at the differential protection device power switch into the line terminal, if there is voltage and the voltage value is within the qualified range, it should consider the air switch to the differential protection device short circuit, the staff on duty should give up trying the differential protection device power switch.

2.2.4 Positive power supply of hard press plate at outlet of differential protection device disappears

If the positive power supply of the outlet hard press plate of the differential protection device disappears, the personnel on duty should first measure the voltage to ground at both ends of the outlet hard press plate with an external meter, and find that there is no voltage to ground at both ends. Then it should consider whether the terminal of the outlet hard press plate is loose and not in contact.

2.2.5TA wire break locking differential protection device

If TA wire break lock differential protection device, the staff on duty should notify relevant professionals to deal with.

2.2.6 Differential Protection Device power board is faulty

If the power board of differential protection device is faulty, it shall immediately report the operation mode adjustment and notify the maintenance personnel to arrive at the station immediately.