I. Failure analysis of relay protect

1. Current mutual inductance saturation fault

The saturation degree of the current transformer to the relay protection of the power system is very large. With the increase of terminal capacity of power distribution system equipment, if a short circuit occurs, the short circuit current will be very large. If the system is shorted near the terminal equipment area, the current may be at or close to 100 times or more the single rated current of the current transformer. Under normal short-circuit conditions, the current transformer error increases with the increase of the multiple of the primary short-circuit current. When the current rate disconnection protection reduces the sensitivity, it can prevent the action. In a line short circuit, since the current of the current transformer is saturated, and the secondary current sensed again is small or close to zero, the fixed-time overcurrent protection device cannot expand. When the overcurrent protection action of the outlet line of the power distribution system causes the protection action of the incoming line of the power distribution system, the entire power distribution system will be shut down.

2. Improper selection of switch protection device

The choice of switch protection device is very important. At present, most of the substations are located in high-load areas, that is, the power supply and transmission methods are as follows: Foshan Substation. For switch stations that have not yet realized relay protection automation, more load switches or relay protection device systems should be used in combination with them as switch protection devices.

relay test and measure equipment

II. Methods and measures to deal with faults of relay protection system

1. Common treatment methods of relay protection faults

1) Substitution method

Replacing the faulty unit with a complete unit and judging the quality of the faulty unit can quickly reduce the scope of fault finding;

2) Reference method

Find out the fault point of abnormal equipment by comparing the relevant technical parameters of normal equipment and abnormal equipment. This method is mainly used to detect wiring errors and faults in which the test value is inconsistent with the expected value in the process of constant value detection. When the secondary wiring cannot be restored correctly after modification and equipment replacement, refer to the wiring of similar equipment. In the relay calibration, if it is found that the test value of the relay is far from the set value, it is not easy to judge whether the characteristics of the relay are good or not, and the calibration value on the relay should be adjusted. The same instrument can be used to measure other similar relays in the same circuit for comparison;

3) Short connection method

A section or part of a circuit is short-circuited with a short circuit to determine whether the fault is within the short-circuit range or elsewhere, thereby determining the fault range. This method is mainly used for electromagnetic lock failure, open current loop, no action of switching relay, and judging whether the contacts of switching switches such as control are in good condition.

2. Measures to ensure the normal operation of relay protection enterprises

Reasonable personnel allocation to ensure smooth scheduling and assistance of personnel, clarify personnel work objectives, and ensure normal operation of power. According to the classification, maintenance, accident analysis, regular verification, defect treatment, reward and punishment of relay protection equipment; secondary equipment condition monitoring method, easy to use Realize the state monitoring of relay protection of comprehensive automatic substation.