The structural principle and working process of the safety valve of the high-voltage circuit breaker operating mechanism.

The pressure relay is mainly installed on the hydraulic operating mechanism and compressed air operating mechanism of the circuit breaker. It has multiple pairs of electrical contacts, which are mainly used to control the starting and stopping of the operating mechanism motor, the blocking of the circuit breaker, and the corresponding alarm signals. The action value of each contact of the pressure relay is preset, and its action is only related to the pressure of the measured medium, not its temperature.

1. The structure of the pressure relay. Take the liquid pressure relay as an example, its structure is shown in Figure 1. It is mainly composed of multi-through body, plunger, guide sleeve, column sleeve, combined spring, valve needle, travel switch, etc. and various parts in the valve body.

Figure 1 Structure of a liquid pressure relay

1- travel switch; 2- valve needle; 3- valve; 4- screw; 5- combination spring; 6-spring seat; 7- valve body

2. The working process of the liquid pressure relay. The hydraulic pressure relay has multiple pairs of electrical contacts to control the start and stop of the motor respectively, and output instructions or alarm signals to lock the circuit breaker to open, close, and reclose. When the pressure increases or decreases, the plunger drives the valve needle to move up or down, and the corresponding travel switch electrical contacts are activated at different pressure values, so as to realize the use of pressure to control the output of related instructions and alarm signals. In addition, a spare travel switch contact is also provided for users' special purposes.

3. The working process of the gas pressure relay. The structure of the pressure relay used in the compressed air operating mechanism is different from that in the hydraulic mechanism. The 63AG in the secondary control loop is the contact that controls the motor. When the air pressure drops to a specified value, the 63AG contact closes, automatically starts the air compressor to suppress pressure, and sends out an automatic air supplement signal; when the air pressure rises to When the rated pressure is specified, it automatically stops the operation of the air compressor, and the air supplement signal automatically disappears. 63AL is the contact to lock the circuit breaker. When the air pressure drops to a certain value, the 63AL contact automatically locks the circuit breaker and sends a lock signal; when the air pressure rises to the specified pressure value, the lock is automatically released. The blocking signal is also released by itself. 63AR is the contact of the recloser of the blocking circuit breaker. Generally, only one pressure-reducing closed contact is given (the pressure-reducing open contact can also be given). When the air pressure drops to a certain value, the 63AR contact will block the circuit breaker's complete reclosing operation sequence (ie: minute -0.3s-closing and opening) to ensure two openings during the reclosing process , The air pressure will not drop too low. Generally, the 63AR contact only gives the signal of reclosing lock, and does not directly control the circuit breaker. Usually, the user uses this contact to perform related control through different wiring methods. When the air pressure rises to the specified pressure value, the reclosing lock signal is automatically released.