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)
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.