A Comprehensive Guide to Home Security Systems:

 

Introduction of switchgear:

The apparatus used for switching,controlling and protection the electrical circuit and equipment is called switchgear.

Features of switchgear:

• complete reliability.
• certain discrimination.
• Quick operation.
• Provision for manual control and instruments.

switchgear Equipments:

1. Switches:
2.  Air break.
3.  isolator.
4.  oil.

Circuit Breaker:

• Air circuit breaker.
• oil circuit breaker.
• ( Sf6 circuit breaker.
•  vacuum circuit breaker.

Circuit Breaker:

INTRODUCTION:

A circuit breaker is a device which can make or break a circuit either manually or  automatically under normal or faulty(short circuit or overload) condition  this process is called circuit breaker.and this is very useful equipment for switching protection of various part of power system.

Operation  OF a Circuit Breaker:

When send the signal to the respective circuit breaker .Now trip coil of circuit breaker will get energised and the moving contact are pulled apart and open the circuit. 

Due to large faulty current, An arc is struck between the fixed and moving parts.This Arc generation is the main function which is to be circuit breaker.

(A)Air blast circuit breaker:

• The circuit breaker employe high pressure air blast as an arc quenching medium.
• The air blas cool the arc and sweeps away the arc product to   atmosphere.
• As compressed air is sued for arc extinction hence are also called compare air circuit breakers.
• Majority of circuit breakers for voltage beyond 110 kv are of this type.hence are must suitable for high voltage.

Construction and working of ABCB:

• At bottom there is a tank which air reservoir with the value.on
• Reservoir here are three hollow insulating columns.On top of each insulator column there is double arc extinguishing chamber.
• The current carrying parts are connected in series.
• As there is brge voltage between the conductor and air reservoir, The assembly of entire extinction is mounted on insulator.

Advantages:

1. Risk of fire is eliminated.
2. High sped operation is achieved.
3. The arcing product are completely removed by the blast.
4. The time for which are persist is short duto to rapid of dielectric strength
5. between contact.so less burning of contacts.
6. duto to lesser arc energy .these are very suitable for condition where frequent 
7. operation  is required.

Disadvantages:

1. Possibility of air leakage at pipe installation.
2. A lot of maintenance is required for the work pressure plant which provides air blast.
3. These breakers are very sensitive to carotenes in the juice rate of the restriking voltage.
4. Due to frequent operation, a high pressure air compressor is necessary.

(B) Oil circuit breaker:

• Transformer oil is mainly used as an arc quenching medium.
• The contact are open under oil and an arc is struck between them.
• The heat produced due to arcc will dissociated the surrounding oil and into gases.
• Mainly hydrogen gas is produced as a result of oil decomposition.
• small amount of methane , Ethylene , Acetylene is also generated.
• The hydrogen gas bubble surrounds the arc and adjacent portion of contacts.
• Arc extinction is oil circuit breakers.
• Hydrogen gas has high heat conductivity and cools the arc.It acids the deionisation of the medium between contact.
• The gas build turbulence in the oil and powerit into the space  between contact, Thus eliminating the arcing products from the arc path.

Application:

• Oil circuit breakers are generally used upto 66 kv.
• TehO CBS have developed for the following voltage ratings:
• 3.6KV,7.2KV,12kv,36kv,72.5kv.

(c)Sulphur HexaFluoride (SF) Circuit Breaker:

•  In SF Circuit Breakers SF gas is used as an are quenching medium.
• SE circuit breakers have been found to be Very effective for high power and high Voltage Services.
• Various types of Circuit breakers (SF) are designed by Various manufacturers danging from 3.6 to 760 KV.
• SF gas is an electronegative gas and has an high tendency to absorb free elections.
•  The negative ion are heavers as compared to free e and they do not get Sufficient energy to lead cumulative ionization in the gas unden a given electric field.

Advantages:

1. There is no risk of fire as the gas is non-flammable.
2. No carbon deposits so insulation problems are eliminated.
3. Very short arcing time.
4. These breakers can interrupt large currents.
5. Silent operation.
6. These breakers are fully enclosed and atmospherically sealed, so they are Especially suitable where there is a risk of explosion such as coal mines.
7. No moisture and dust problems.
8. Requires minimal maintenance.
9. There are minimums associated with current cuts.

(D) Vacuum Circuit Breaker(VCB):

• In these circuit breakers. Vacum of the 10 minus 5 to 10 10 minus to 7 torr  is sud as arc quenching medium.
• It HAS highest insulting strength than any other medium.
• It does the interruption at first current xero.
• Dielectric strength is far better than ant other medium.
• Construction:
• It has an outer envelope made up of glass joined with metallic end caps
• The examingn of the breaker after operation is done through this glas envelope
• When it becomes Milky white.It INDICATES THAT it isn losing vaccum.
• Sputter shield made up of stainless is sud to prevent metal vapour reaching envelop.
• ceramic envelop is used as outer insulting body.
• Advantages:

1. No fire hazards
2. Compact and reliable
3. Have longer life.
4. Less maintenance required.
5. Noiseless operation.
6. No hazardous gas released during or after operation.
7. low arc energy.
8. can withstand lighting surges.

APPLICATIONS:

• useful for remote area due to less need of maintenance.
• These are employed for reactor switching.Transformer switching.capacitor bank switching.
• These are generally used for outdoor application form 22 kv to 66kv.