Analysis and discussion on switch electrical anti-trip circuit

1 Introduction

With the continuous application of new technologies, how to deal with

Usually, domestic protection devices use switch operation boxes and circuit breaker interfaces. The operation circuit is designed according to the principles of domestic hydraulic, electromagnetic and other operating mechanisms. The operation circuit has an electrical anti-trip relay. If the relevant electrical circuit is not properly technically processed, the most common problem is that the anti-trip relay of the switch device itself does not return to excitation, the red and green signal lights are all on, and the switch cannot be closed. Take the switch itself with anti-trip as an example in Figure 2. When the switch is in the open position, the negative electricity passes through the internal anti-trip relay K1 of the switch and the auxiliary contact S1 of the circuit breaker to the 107 position. If the parameters are not properly matched, it will usually cause the jump relay WJ and the anti-trip relay K1 to be excited, and the phenomenon is that the red and green signal lights are all on. Because the anti-trip relay K1 has a self-holding contact, the anti-trip relay on the switch device does not return after the switch is opened, and it cannot be closed again. In view of the above problems, the main reasons for the abnormality of the circuit are the dual anti-trip and the mismatch of the relay voltage coil parameters. The solution to the problem is to disconnect the starting coil of the anti-trip relay in the switch mechanism and cancel the electrical anti-trip circuit in the switch mechanism.

3. Switch anti-bounce analysis of contact shunt protection mode

In distribution substations of voltage levels such as 10 kV (6 kV), GL electromagnetic relays and contacts are generally used for shunt tripping when the scale is small. In the event of a fault, the current transformer is used to trip through a special release instead of the switch operation control circuit. Therefore, its anti-tripping structure cannot use the anti-tripping circuit with a good operating power supply mode, and a new structure of the switch anti-tripping circuit is required.

This simple treatment in Figure 3 was once widely used in power distribution substations, but with the widespread use of energy-saving lamps (such as AD11), the indicator light circuit often causes the anti-trip relay 1ZJ to be unable to lose magnetism and reset, resulting in the switch being unable to close again. In order to solve this problem, one approach is to use a dedicated anti-trip relay to achieve parameter coordination with the signal indicator light, which has a good effect. Another approach is to change the indicator light start circuit. The common treatment method is shown in Figure 4.

The green indicator light is activated by the switch position auxiliary contact. Although it can prevent the anti-tripping relay from losing magnetism, the signal indicator light cannot accurately indicate the integrity of the tripping and closing circuit, causing trouble to on-site operators. There are certain defects in the circuit design.

In view of the contact de-shunting protection method, we have conducted an in-depth analysis of the problems existing in the switch anti-tripping circuit. The key to the problem is the parameter matching problem between the signal light and the anti-tripping relay. The problem occurs when the switch is in the open position. If the processing method in Figure 5 is adopted, the auxiliary contact of the switch position adopts double breakpoints, and the auxiliary contact of the switch is used to cut off the power supply of the green signal light, which can effectively solve the abnormal problem caused by the matching problem of the anti-tripping relay and the green light parameters when the switch is in the closed position. At the same time, the signal light can meet the monitoring function of the closing circuit, and the secondary circuit changes are small and do not increase the cost of other equipment. Through the application in specific engineering practice, the problems existing in the switch anti-tripping circuit are effectively solved, and good results have been achieved.

4 Conclusion

Preventing switch tripping is of great significance to ensuring the safe production of power systems. How to deal with the anti-tripping interface problem between protection devices and switchgear, and how to make the switch electrical anti-tripping circuit more reasonable and perfect are still of great importance and practical significance today when computer technology is continuously applied to power systems.