1. What is the function of the on / off buffer of high voltage circuit breaker?

The function of the opening buffer is to prevent the parts of the circuit breaker from being damaged by the huge impact force generated when the spring releases energy.

The function of closing buffer is to prevent the casing from being damaged by the impact force when closing.

2. What is free tripping of circuit breaker?

At any time in the closing process of the circuit breaker, if the protection action connects the tripping circuit, the circuit breaker can be disconnected easily, which is called free tripping. The circuit breaker with free tripping can ensure that the circuit breaker can be quickly disconnected in case of short circuit fault, so as to avoid expanding the scope of accident.

3. What good arc extinguishing performance does SF6 gas have?

SF6 gas has the following good properties:

(1) The arc column has high conductivity, low arc voltage and low energy.

(2) When the AC current passes zero, the dielectric insulation strength of SF6 gas recovers faster, about 100 times faster than that of air, that is, its arc extinguishing ability is 100 times higher than that of air.

(3) SF6 gas has high insulation strength.

4. Why is the outdoor bus joint easy to get hot?

Outdoor bus shall be frequently eroded by wind, rain, snow, sunlight, freezing, etc. All of these can accelerate the oxidation and corrosion of the bus joint, increase the contact resistance and temperature of the joint.

5. What are the phenomena when the system oscillates?

The phenomena of system oscillation are as follows

(1) The pointer of ammeter, voltmeter and power meter in substation fluctuates periodically. If there is tie line, the swing of ammeter is obvious.

(2) The closer to the oscillation center of the system, the greater the voltage swing, and the incandescent lamp turns on and off, which is very obvious.

6. What role does DC system play in substation?

DC system provides DC power supply for control, signal, relay protection, automatic device and emergency lighting in substation. It also provides operating power for the operation. Whether the DC system is safe or not plays a vital role in the safe operation of the substation, which is the guarantee of the safe operation of the substation.

7. What is Internal Overvoltage?

Internal over-voltage is a transient process in which the state of the system changes suddenly due to operation, accident or other reasons. It may be dangerous to the system in this process. These overvoltages are caused by the oscillation and accumulation of electromagnetic energy in the system, so they are called internal overvoltages.

8. Can low voltage AC / DC circuits share one cable? Why?

No, because:

(1) Sharing one cable can reduce the insulation level of DC system.

2. If the DC insulation is damaged, the DC mixed line will cause short circuit or misoperation of relay protection.