High Voltage Circuit Breakers

Electrical power transmission networks are protected and controlled by high-voltage breakers.

SF6 gas filled and spring mechanism operated CBs are widely used in modern EHT systems

Basic operating principle of these breakers does not vary from any other LV or MV CBs

Sulphur hexafluoride (SF6) gas is a good arc quenching medium due to its low ionization property

SF6 has good insulation properties too

The chambers and the supporting hollow insulators are filled with SF6 gas

In the previous picture, the breaker is operated using a gang operated single mechanism box

CBs with separate operating mechanism box for each pole are also in use.High Voltage Circuit Breakers

SF6 High Voltage Circuit Breakers

MCCB

Moulded case CBs are used for high current application

MCCBs are used to protect single equipment with limited protection requirements

The MCCB shown in the picture is a 100A, 3Phase, 690Volts, 25KA , Curve D

MCCBs are equipped with provision for current adjustment for over load protection

MCCB

Air Circuit Breaker

The most commonly used LVCB

Almost all the low voltage switch gears are equipped with ACBs

Has wide range of protections from Over current to under voltage

There are a number of releases available in the breaker

The releases are connected to relays based in the requirement. Say, for under voltage or earth-fault tripping

Arc quenching is done in the air. No special device is used here except provision for arc elongation

Air Circuit Breaker

Miniature Circuit Breakers (MCBs)

• Miniature Circuit Breakers (MCBs) are generally used for low current application
• This a simple circuit breaker that is used to break the circuit in case of over current
• MCBs are most commonly used in protecting equipment like lamps, heaters, air-conditioners, motors and so on
• MCBs work on the principle of thermo-couple action
• When a current higher than the rated current flows through it, the thermocouple is heated up and trips the MCB
• MCBs are specified as for example : 415 V, TPN (Three Pole Neutral), 32A, 10KA(breaking capacity) and C curve
• There are number of types of MCBs viz :
• 1phase,Single pole
• 1phase 2 pole
• 3 phase 3 pole
• 3 phase 4 pole

Miniature Circuit Breaker – Inner view

1.Actuator lever - used to manually trip and reset the circuit breaker.

2.Actuator mechanism - forces the contacts together or apart.

3.Contacts - Allow current when touching and break the current when moved apart.

4.Terminals

5.Bimetallic strip

6.Calibration screw - allows the manufacturer to precisely adjust the trip current of the device after assembly.

7.Solenoid

8.Arc divider / extinguisher

CLASSIFICATION OF CIRCUIT BREAKERS

Based on Voltage

• Low - Less than 1kV
• Medium - 1kV to 52kV
• High/Extra High - 52kV to 245kV
• EHV - 245KV to 765kV
• Ultra High - Above 765kV

Based on location

• Indoor
• Outdoor

Based on External design

• Dead tank
• Live tank

Based on Interrupting media

• Air break
• Air blast
• Bulk oil
• Minimum oil
• SF6 gas insulated
• Vacuum

Circuit Breakers

A circuit breaker is an automatically-operated electrical switch designed to protect an electrical circuit from damage caused by over load or short circuit.

Its basic function is to isolate the circuit in case of a fault. By interrupting continuity, flow of electricity through the faulty circuit is stopped

Unlike a fuse, which operates once and then has to be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation.

There are different types of circuit breakers. From LV Miniature CBs to 800KV SF6 CBs, we can see wide range of breakers

The circuit breaker serves two basic purposes

Switching during normal operating conditions for the purpose of operation and maintenance.

Switching during abnormal conditions such as short circuit or any other faults... thereby isolating the circuit.

Mini Circuit Breakers

Mini Circuit Breakers from Havells:They help protect your electrical appliances and you against any danger. Make your electrical appliances and home safe by using Circuit Breakers!