Switchgear - Classification

Classification

Several different classifications of switchgear can be made:

• By the current rating.
• By interrupting rating (maximum short circuit current that the device can safely interrupt)
  • Circuit breakers can open and close on fault currents
  • Load-break/Load-make switches can switch normal system load currents
  • Isolators may only be operated while the circuit is dead, or the load current is very small.
• By voltage class:
  • Low voltage (less than 1,000 volts AC)
  • ** High voltage (more than 1,000 volts AC)
• By insulating medium:
  • Air
  • Gas (SF₆ or mixtures)
  • Oil
  • Vacuum
• By construction type:
  • Indoor (further classified by IP (Ingress Protection) class or NEMA enclosure type)
  • Outdoor
  • Industrial
  • Utility
  • Marine
  • Draw-out elements (removable without many tools)
  • Fixed elements (bolted fasteners)
  • Live-front
  • Dead-front
  • Open
  • non metal enclosed
  • Metal-clad
  • Metal enclosed & Metal clad
  • Arc-resistant
• By IEC degree of internal separation
  • No Separation (Form 1)
  • Busbars separated from functional units (Form 2a, 2b, 3a, 3b, 4a, 4b)
  • Terminals for external conductors separated from busbars (Form 2b, 3b, 4a, 4b)
  • Terminals for external conductors separated from functional units but not from each other (Form 3a, 3b)
  • Functional units separated from each other (Form 3a, 3b, 4a, 4b)
  • Terminals for external conductors separated from each other (Form 4a, 4b)
  • Terminals for external conductors separate from their associated functional unit (Form 4b)
• By interrupting device:
  • Fuses
  • Air Circuit Breaker
  • Minimum Oil Circuit Breaker
  • Oil Circuit Breaker
  • Vacuum Circuit Breaker
  • Gas (SF₆) Circuit breaker
• By operating method:
  • Manually operated
  • Motor/stored energy operated
  • Solenoid operated
• By type of current:
  • Alternating current
  • Direct current
• By application:
  • Transmission system
  • Distribution
• By purpose
  • Isolating switches (disconnectors)
  • Load-break switches.
  • Grounding (earthing) switches

A single line-up may incorporate several different types of devices, for example, air-insulated bus, vacuum circuit breakers, and manually operated switches may all exist in the same row of cubicles.

Ratings, design, specifications and details of switchgear are set by a multitude of standards. In North America mostly IEEE and ANSI standards are used, much of the rest of the world uses IEC standards, sometimes with local national derivatives or variations.