Module 6:Medium Voltage Power Circuit Breakers.

Module 6,which is about Medium Voltage Power Circuit Breakers.

By medium voltage, we mean a voltage range of 1000 volts to 38 kV. (Some consider 72.5 kV as the upper end of medium voltage, but we will work with 38 kV for the purpose of this training module.)

Like the other modules in this series, this one presents small, manageable sections of new material followed by a series of questions about that material. Study the material carefully, then answer the questions without referring back to what you've just read. You are the best judge of how well you grasp the material. Review the material as often as you think necessary. The most important thing is establishing a solid foundation to build on as you move from topic to topic and module to module.

Introduction
To understand where the medium voltage power circuit breaker fits into the scheme of things, you need to understand the basics of power distribution in an industrial environment.
An industrial distribution system consists of:

• metering devices to measure power consumption
• main and branch disconnects
• protective devices
• switching devices to start and stop power flow
• conductors

• transformers

Power may be distributed through various Switchgear and Switchboards, transformers and Panelboards. The medium voltage power circuit breaker is found in switchgear assembly. A switchgear assembly controls electric power circuits.

The Circuit Breaker is the main device - the heart - of the switchgear. It provides centralized control and protection of medium voltage power equipment and circuits. Its operation covers load switching, control and fault protection for generators, motors, transformers, capacitors and all types of feeder circuits.

This type of power equipment is normally found in industrial, commercial and electric utility installations. Typical applications include electric utility systems, industrial distribution systems, commercial buildings, municipal pumping stations, and transportation systems.