Switch Gear refers to the combination of switching devices (like circuit breakers, isolators, fuses) and protective devices used to control, protect, and isolate electrical equipment.
A: FUNCTION: Its main functions are :
- Control power flow
- Protect equipment from faults
- Ensure safety during maintenance
- Provide system reliability and flexibility
B: COMPONENTS OF SWITCH GEAR
- Circuit Breakers (CBs) – Automatically interrupt fault current.
- Isolators / Disconnectors – Ensure equipment is completely de-energized for maintenance.
- Fuses – Protect against short circuits.
- Relays – Detect abnormal conditions (overcurrent, earth fault, differential fault, etc.) and trigger circuit breakers.
- Busbars – Distribute electrical power.
- Current Transformers (CTs) & Potential Transformers (PTs) – Measurement and protection inputs.
C: TYPES OF SWITCH GEAR
- Based on Voltage Level
- Low Voltage (LV) Switchgear → up to 1 kV (used in industries/buildings)
- Medium Voltage (MV) Switchgear → 1 kV – 36 kV
- High Voltage (HV) Switchgear → above 36 kV (transmission substations)
- Based on Interruption Medium
- Oil Circuit Breakers
- Air Break Circuit Breakers
- SF₆ Circuit Breakers (gas-insulated, widely used at HV/EHV)
- Vacuum Circuit Breakers (VCB)
D:PROTECTION IN POWER SYSTEM:
Protection ensures safety of equipment and continuity of supply by quickly isolating the faulty section.
E:COMMON PROTECTION SCHEME:
- Overcurrent Protection – For excessive current (phase fault, short circuit).
- Earth Fault Protection – Detects leakage of current to ground.
- Distance Protection – Used in transmission lines, measures impedance.
- Differential Protection – For transformers, generators, motors.
- Overvoltage / Undervoltage Protection
- Underfrequency / Overfrequency Protection
F: DIFFERENCE BETWEEN SWITCH GEAR AND PROTECTION:
- Switchgear = Devices to switch & control power (CB, isolator, busbar, fuse).
- Protection = Schemes & relays that detect faults and operate switchgear to isolate the faulty section.
G: APPLICATIONS:
- Power generation plants
- Transmission & distribution substations
- Industrial power systems
- Commercial buildings & data centers
XOX
SWITCH GEAR AND PROTECTION