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When you want to buy switchgears, you should know some basic knowledge (part 1)
December 08 , 2020

When you want to buy switchgears, you should know some basic knowledge for "What? How? Why?" (part 1)


removable metal enclosure switchgear


1.Why is switchgear called "complete set"? What kinds of cabinet does it compose of?

Switchgear is composed of incoming line, metering, PT, outgoing line, etc. Primary and secondary Components are installed inside the cabinet, when buying, must form a complete set, so we call "complete set".


2. Why need discharge voltage (10KV class voltage)? How can we discharge voltage safely?

When we cut off the power, the voltage must be discharged in order to prevent the capacitor from remaining power and injuring people.

Safety discharge voltage method: when opening cabinet door or panel, do not touch the bus directly by hand. First, use a 10KV electroprobe to check whether has electricity, and then find a wire, one end connect to ground, and one end to the electroprobe. Use the front end of the electroprobe to contact the bus to discharge, after confirm no electricity, can start to repair it, to ensure personal safety. Keep that in mind.


3. What should be the voltage of the 10KV test electricity? What is the difference between domestic and international standards?

Domestic: cabinet 42kV, fracture 48kV

International: 36kV


4. How to understand the meaning of XGN letters in XGN86 switchgear?

X – box type high voltage switchgear

G – fix type high voltage switchgear

N – indoor high voltage switchgear


5.What is the function of pressure relief channel?

In the event of an explosion, there will be a strong blast of air. At this time, if there is a pressure relief channel on the top of the cabinet, the air blast can be discharged from the top, without affecting the normal work of other parts. If there is no pressure relief channel, the blast will break through the weakest place. And sealed air insulation switchgear can avoid the switchgear air pressure too high.


6.Which main primary components should be assembled in the switchgear?

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


7.What is the function of the switchgear? What can protect the transformer?

Switchgear function is to open and close the transformer with load. It relies on high-voltage fuses to protect the transformer.


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

Air distance between phase to phase and phase to earth, 10KV requires 125mm.


9. How to check whether the vacuum switch is vacuum?

Make withstand voltage test. The fracture test by 48kV voltage.


10. What is the function of isolating plug and isolating switch? What kind of cabinet is it used for?

The isolating plug is use for handcart cabinet, the isolation switch is used for fix type switchgear. Their function are to open and close without load, convenient for maintenance.


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