What Is Switchgear And Its Types
Switchgear is an apparatus which is used for switching, controlling and protecting electrical circuits and equipment. The requirement of electric power has increased a lot, so in order to get a continuous power supply. Power system must be protected from large faults and provide protection to machinery and devices .For the continuity of the power supply machinery such as generators and motors are switched on and off many times and the means provide to achieve this is called switchgear.
In general, switchgear is the term including the entire range of switching devices and their combination with associated control, measuring, protecting, and regulating equipment.
Components of switchgears
- Circuit breaker
- Current transformer and potential transformer
- Protective relays
- Measuring instruments
- Surge arrestors
- Miniature circuit breaker
Essential Features Of Switchgears
- Reliability – switchgear is used in a power system to improve the reliability when a fault occurs in system switchgear must isolate the faulty section from the remainder circuit
- Absolutely certain discrimination – if fault occurs in a power system then switchgear must be able to discriminate between the faulty section and healthy section.
- Quick operation – if any fault occurs in a power system then switchgear must be able to act quickly so that no damage is done to the equipment
- Provision for manual control – switchgear must have manual control in case of any electrical or electronic control fail
- Provision for instruments – provisions for the instruments is needed this may be in the form of ammeter, voltmeter.
Classification Of switchgears
- The current rating
- Interrupting rating
- Voltage class- low voltage (less than 1000volts)
Medium voltage (1000 – 36000 volts)
High voltage (more than 36000 volts)
- Insulating medium – air, gas, oil, vacuum
- Construction type – indoor, outdoor, industrial, metal-enclosed, metal-clad…
- Type of current – AC, DC
- By application – transmission system, distribution
- Operating method – manually, motor or solenoid/stored energy
Types of Switchgears:
- Low voltage (LV) Switchgear
- Medium voltage (MV) Switchgear
- High voltage (HV) Switchgear
Low Voltage switchgears:
Generally electrical switchgear rated up to 1 KV is termed as low voltage switchgear.
- Off load electrical isolators
- HRC fuses
- Earth Leakage Circuit Breakers
- Miniature Circuit Breakers
- Molded Case Circuit Breakers etc.
Medium voltage Switchgears:
From 3 KV to 36 KV switchgear system is categorized as medium voltage switchgear or MV switchgear. These switchgears are of many types.
- Metal Enclosed Indoor Type
- Metal Enclosed Outdoor Type
- Without Metal Enclosure Outdoor Type
- Oil Circuit Breakers
- Vacuum Circuit Brakers
The main requirement of MV power network is to interrupt current during faulty condition irrespective of what type of CB is used in the MV switchgear system.
High Voltage Switchgears:
The power system deals with voltage above 36KV, is referred as high voltage. As the voltage level is high the arcing produced during switching operation is also very high. So, special care to be taken during designing of high voltage switchgear. High voltage circuit breaker, is the main component of HV switchgear, hence high voltage circuit breaker should have special features for safe and reliable operation. Faulty tripping and switching operation of high voltage circuit are very rear. Most of the time these circuit breakers remain, at ON condition, and may be operated after a long period of time. So CBs must be reliable enough to ensure safe operation, as when required.
- Miniature Oil Circuit Breakers
- Air Blast Circuit Breakers
- SF6 Circuit Breakers