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When you want to buy switchgears, you should know some basic knowledge(part 3)
December 15 , 2020

When you want to buy switchgears, you should know some basic knowledge for "What? How? Why?" (part 3)


high voltage circuit breaker for home

27、What kinds of circuit breakers are there?

1) Vacuum circuit breaker: Use vacuum as arc extinguishing medium and main insulating medium. The dynamic and static contacts of arc extinguishing are sealed in vacuum arc extinguishing room. There are mainly 10VK and 35KV voltage classes.


2) SF6 circuit breaker: came out late. In the early 1970s, it was widely used. Now it is an advanced equipment of power system. SF6 gas is used as arc extinguishing medium. The breaking capacity is about 10 times higher than common circuit breakers. The advantage is with low arc voltage, short arcing time, the contactor burns less, can operate frequently. The disadvantage is that SF6 is more expensive, need recovery device and the structure is complex. Our country has produced 220KV with SF6 as the main body of the fully enclosed combination electrical appliances.

The main equipment of substation, such as circuit breaker, isolation switch, transformer, lightning arrester and bus, are all installed in sealed container with SF6 gas, which greatly reduces the occupied space of substation.It is the main development direction of ultra high voltage electric appliance.It has been widely used abroad.


3)Air circuit breaker: use compressed air as arc extinguishing medium. Mainly used for ultra high voltage. 380KV has been produced in China. 765KV has been produced abroad.


4) Solid gas-producing circuit breaker: uses fixed medium and is decomposed into gas by the action of arc to blow arc and extinguish the arc.


5) Magnetic blowout circuit breaker: Use magnetic field to blow the arc into the arc extinguishing gate.


28. What is power transformer?

Power transformer is an electrical device for changing voltage (current).It can't change power.

Basic structure: mainly consists of a closed core and two different number of turns around the iron core and coil (winding) of the insulation to each other, in order to reduce the eddy current and hysteresis loss, iron core is coated with insulating paint. The silicon steel sheet with a thickness of 0.35-0.5mm with good magnetic permeability is laminated, which constitutes the primary coil of the closed magnetic circuit in the transformer, called thick coil type primary side, and the secondary coil called pay coil type primary side. The three-phase transformer group connected by a three-phase transformer is the three-phase transformer.


29. What is current transformer?

Current transformer (CT) is an instrument for measuring the high current from the primary side into the low current from the secondary side according to the principle of electromagnetic induction


30. What is voltage transformer?

Basic structure:

Voltage transformer is a special transformer with extended voltage range. The basic structure is the same as ordinary transformer.



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