Current Transformer

Current transformer
High accuracy C800 wound current transformer typically used for revenue metering purpose.

Purpose of current transformer

  • Relays need to know the magnitude of the current flowing in the system. A current transformer fulfills this role – it steps down thousands of amps to (typically) 5A which is then fed to a relay.
  • CT’s establish zone of protection in a power system. You can never have enough of them.
  • They are installed on
    • Bushings of a circuit breaker (donut CT)
    • Bushings of a transformer (donut CT)
    • The line-exit where the ownership changes (stand-alone CT)
    • The location adjacent to EHV live-tank breaker (stand-alone CT)
Current transformer
Current transformer on a breaker bushing
current transformers on line-exit
Current transformers on line-exit (this unit also contains a potential transformer)

Cost of current transformer

365kV 3000:5A MR C800 accuracy CT: ~$30,000

Lead time to procure current transformer

Extra high voltage stand-alone unit: ~1 year

Information on cost and lead time is for your general knowledge only. Contact vendor with your equipment specifications for actual figures.

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