Medium Voltage Vacuum Circuit Breaker

A 3D representation of a medium voltage vacuum circuit breaker.

Introduction

This 3D model shows a medium voltage circuit breaker.

3D Model Annotations

Cable Terminations

Cable terminations enter the base of the switchgear via cable ducts. This example shows three cables per phase.

Voltage Transformers

Measures the primary alternating voltage and produces a secondary voltage at much lower voltage; the secondary voltage is proportional to the primary voltage. The secondary voltage can be conveyed to protection relays and other measuring devices at a much lower and more suitable voltage rating.

Current Transformers

Measures the primary alternating current and produces a secondary current at much lower amperage; the secondary current is proportional to the primary current. The secondary current can be conveyed to protection relays and other measuring devices at a much lower and more suitable current rating. Current transformers are a type of instrument transformer.

Earthing Switch

Used to mechanically earth or short circuit an electrical circuit. Earthing switches should be able to carry the rated short-term current without damage occurring to the switch.

Automatic Shutters

Automatic shutters close when the circuit breaker is removed for maintenance or replacement. Closing of the shutters ensures the primary circuit can not be accessed through the circuit breaker compartment. Automatic shutters are an additional feature to protect personnel.

Vacuum Interrupter Chamber

Making and breaking of the electrical circuit occurs within a vacuum chamber. One vacuum chamber is used per phase. The contacts used to open and break the circuit are housed within each vacuum chamber.

Busbar

Busbars are housed within the busbar compartment. Each busbar contains one phase. Busbars are usually constructed of copper or aluminium.

Busbar Compartment

Busbars are housed within the busbar compartment.

Circuit Breaker

This model shows a vacuum circuit breaker. Vacuum insulated circuit breakers are a very common type of medium voltage circuit breaker due to their cost, low maintenance and low environmental pollution impact (they do not contain insulating oil or ozone damaging gases).

Circuit Breaker Compartment

Houses the main breaker equipment used to close and open the electrical circuit. The circuit breaker is removable (physically separable), self-coupling and self-aligning with the primary disconnecting devices.

Metal Clad Switchgear

The entire switchgear is surrounded by a metal casing which is usually earthed.

Low Voltage Compartment

Houses the breaker’s low voltage equipment. Protection relays and other control electronics are housed in the LV compartment.

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