HV LV Switchgear Electrical Knowledge

1. Why is a switchgear called a "complete set" and what cabinet is it composed of

The switchgear is composed of incoming lines, metering, PT, outgoing lines, etc. The cabinet is equipped with primary and secondary components, which must be matched when purchasing, so it is called "complete set".

2. How many levels of power voltage are there in China, and state the role of grading.

It is divided into 500KV, 220KV, 110KV, 35KV, 10KV, 380V, 220V and other levels.

Due to the relationship between voltage and line loss, the higher the voltage, the lower the line loss. In this way, the farther the distance to transmit electricity, the higher the voltage level that needs to be transmitted.

3. Why do I need to unload the voltage (10KV level)? What method can be used to safely unload the voltage?

During a power outage, in order to prevent the capacitor from remaining charged and injuring personnel, it is necessary to remove the voltage.

Method for safe voltage discharge: When opening the cabinet door or screen board, do not directly touch the busbar with your hands. First, use a 10KV test pen to check if there is electricity, then find a wire with one end grounded and one end connected to the front end of the test pen. Use the front end of the test pen to contact the busbar for discharge, and repair can only be carried out after completion to ensure personal safety. Remember this point.

4. What should be the voltage of the 10KV test electricity? What are the differences between domestic and international standards?

Domestic: 42000 volts for cabinet and 48000 volts for fracture;

International: 36000 volts

5. How to understand the meaning of the letters KYN in the switchgear model?

K - Metal enclosed armored type

Y - movable type

N - Indoor

6. What is the function of a pressure relief channel?

If there is an explosion in the cabinet, a strong wave of air will be generated. At this point, if there is a pressure relief channel on the top of the cabinet, the air waves can be discharged from the top without affecting the normal operation of other parts; If there is no pressure relief channel, the air waves will rush towards the weakest point.

7. What are the main primary components that the switchgear should be equipped with?

Circuit breaker, contact base, lightning arrester, zero sequence transformer, current transformer (CT), voltage transformer (PT), high-voltage fuse, etc.

8. What is the function of the ring network switchgear? What does it rely on to protect the transformer?

Its function is to open and close with load, and it relies on high-voltage fuses to protect the transformer.

9. What is the national standard for air insulation distance?

The air distance between phases and ground is required to be 125mm for 10KV.

10. What is the creepage distance of insulation components?

The conductive distance from the high-voltage live side to the ground and crawling along the surface of the insulation component is called the insulation component creep distance. 10KV requires 235mm.

11. What method is used to check if the vacuum switch is vacuum?

Use voltage withstand test for detection. Detect the fracture with 48000 volts.

12. What are the functions of isolation plugs and isolation switches, and what type of cabinet are they used for?

Isolation plug for handcart cabinet; The isolation switch is used to fix the cabinet. Its function is to open and close without load, which is convenient for maintenance.

13. What are the approximate levels of current in the high-voltage cabinet? What level does the load switch belong to?

Divided into three levels: 3150A, 1250A, and 630A. The load switch belongs to the 630A level.

14. What is the function of a high-voltage fuse?

Used for protecting transformers, PT belongs to the category of small transformers.

15. What is the function of a live display?

It serves as an indicator to indicate whether there is high voltage inside the cabinet.

16. What does a program lock do? Where is it installed?

The operation sequence of cabinets is interlocked according to the prescribed procedures to prevent misoperation.

17. What does the grounding switch do?

The grounding switch is installed at the outlet end, which can prevent reverse supply of high-voltage electricity during maintenance and ensure personal safety.

18. What is the function of a valve?

When the handcart is pulled away from the cabinet, prevent people or metal from coming into contact with high-voltage static contacts.

19. Why do busbars need to be glued?

Acting as an insulation, it can reduce the air insulation distance and prevent short circuit accidents caused by small animals entering the cabinet.