What is switch gear. Uses of switchgear. Types of switch gear

 

What is switch gear

Definition of switch gear

Switch gear is the equipment which is used to control, switch on and off and regulate electrical power in the electrical power system. Switch gear consists of fuses, switches, isolator, circuit breaker, relay, potential or voltage transformer, current transformer or CT, lightning arrester, power transformer, tape changer and control panels etc.

Switch gear is located normally in substation and generarating station in electrical system where electrical power is generated and distributed. Control is a must for electrical power for both electrical power requirement and protection. Switch gear is used to switch on a off power according to power requirements as well as for electrical system protection to isolate faulty circuit from the power system in case of failure and faults.

Switch gear is used on both high voltage and low voltage side of the supply system. It is used to energize and DE-energize the power system and equipment form the supply for power requirement, maintenance and isolation in case of any fault and system failure.

Typical switch gear system

Function and uses of switch gear

Consumer equipment is connected to the power system to draw electrical power to perform certain job. In normal conditions a specified amount of current is drawn by the electrical equipment in the system. When fault occurs in the electrical power system, abnormally high current flows through the system. This abnormally high current flow can damage the electrical system equipment like transformer, transmission lines, circuit breaker and power generator. Also this heavy current flow would interrupt the rest of the power system connected to that electrical system. To protect such electrical equipment in the power system like transformer, circuit breaker, generator bus bars and transmission lines from damage, automatic switch gear system is used which is equipped with protective relays and circuit breakers to isolate the circuit in case of any abnormality.

There are certain different relays are connected in the electrical system which are observing line condition all the time. They detects any abnormality on the transmission line. When the fault level exceeds a certain thresh hold level, these relays signals the circuit breaker to break or isolate the circuit. In this way they protects the system from abnormality.

When the fault occurs in the power system, heavy current flow through equipment due to which the equipment get damaged, and the service also get interrupted. So to protect the lines, generators, transformers and other electrical equipment from damage automatic protective devices or switchgear devices are required. In this way the automatic switch gear system isolates the faulty circuit from the healthy circuit or section. The healthy circuit or section continuously in operation and serve without interruption. In this way only faulty circuit is disconnected and no black out for the whole system.

Types of switch gear

There are many types and kinds of switch gear. Switch gear has two types or kind according to construction view point.

• Outdoor type switch gear
• Indoor type switch gear

The outdoor type switch gear is located in open are under the sky. Switch gear for above 66KV  are normally outdoor type. The reason behind this is for high voltage very high insulation is required. The insulation between conductor is normally air. So very big spacing is required between high voltage conductors. Such big spacing needs very large building construction. So in such a case it is more feasible to construct such a switch gear outdoor under the open sky.

Outdoor switch gear

Under 66KV electrical system there is no big issue of insulation and spacing between conductors. For such system indoor switch gear construction is not a big problem. Indoor switch gear units are enclosed in metal panels. They are compact in design. Due to such closed encloser the circuit safety is increased and is easy. Look after is easy for such systems and they are more durable due to weather proofing.

Indoor switch gear

What is inside a switchgear?

Switchgear consists of protection devices like circuit breaker, fusible links, switches, protection relays, bus bars and metering device and equipment for measurement purpose. Switchgear can be outdoor type or indoor type.

What are the different types of switchgear?

According to functionality there are three types of swithgears

• LV or low voltage switchgear
• MV or medium voltage switchgear
• HV or high voltage switchgear

What is a switchgear room?

In electrical control system the switchgear room is the control room that combines the circuit breaker, protection relays, fuses and switches to control electrical power.

What is difference between switchgear and circuit breaker?

Switchgear is a whole system of electrical protection system and control system. Whereas the circuit breaker is a part of switchgear which is used to connect and disconnect the electrical circuit. Circuit breaker works like a high voltage and high current fast switch.

What is HT and LT?

In electrical system HT means high tension and LT means low tension. HV and LV are also used terms for HT and LT. LT or LV is low voltage normally used in our houses and small industries. Whereas HT or HV is the high voltage normally used for transmission of electrical power between cities and countries.

What is MVSG?

MVSG is medium voltage switchgear. Medium voltage is commonly used in industry. Large industrial motors are running on MV which is normally 6KV. To control such power MVSG or medium voltage switch gear is used to switch on and off the system.