Medium Voltage Circuit Breaker (CB) Classification.

Medium Voltage Circuit Breaker (CB) Classification.

Circuit breaker (CB) is a device used to protect electrical equipment into over current or short circuit fault. It has make and breaks the circuit on-load conditions.

Medium Voltage Circuit Breaker (CB).

The current flow in a conductor always generates heat. The greater the current flow, the hotter the conductor. Excess heat is damaging to electrical components. High levels of heat cause the insulation to breakdown and flake off, exposing conductors. Excessive current is referred to as over current. An over current may result from overload, short circuit, or ground fault.

A medium voltage breaker performs the following functions:

Allows buses and components to be energized and De-energized as needed during the normal switching operation.
When a system component develops a short circuit or other problem activating a protective relay, it must interrupt current and voltage to associated loads and from power sources to protect the system.

Model of GIS Switch Gear Unit

Classifications of Circuit Breaker:

Circuit breakers are classed or referred to by their voltage size and arc extinguishing method.

Voltage Class:

Circuit breakers are grouped by voltage classes that are normally defined as LOW, MEDIUM, and HIGH.

Low Voltage (0-600V): Generally includes Molded Case Breakers, Power Metal clad breakers and the new design large molded frame power breakers.
Medium Voltage (600V through 15KV): this includes 4160V, 6.9KV and 13.8KV. Sometimes 34KV breakers are included.
High Voltage (Above 15KV): These are usually breakers associated with transmission and the first line step down coming off the transmission.

Arc Extinguishing:

All circuit breakers have contacts, and when the contacts separate during an opening operation they draw an arc, assuming that power is flowing through the device. The electric arc forms between the contacts and is drawn out in length as the contacts open.

Therefore, circuit breakers require a device to control or remove the arc; the 4 common mediums used to extinguish an arc during breaker contact separation are Oil, Air, Gas, and opening in a Vacuum.

Oil Circuit Breakers (OCB).
Air Circuit Breaker (ACB).
Air Blast Circuit Breaker.
Gas Circuit Breakers.
Vacuum Circuit breakers.

According to the operating mechanism:

Spring operated circuit breaker.
Pneumatic circuit breaker.
Hydraulic circuit breaker.

Medium Voltage Circuit Breaker (CB) Classification: