Purpose of voltage transformers
- Relays need to know the magnitude of the voltage in the system. A voltage transformer fulfills this role – it steps down thousands of volts to 67V/115V which is then fed to a relay. At high voltage 138kV and above, VT’s are built using capacitors and a small aux transformer. At 69kV and below, they are wound.
- Typically installed on
- Each bus section
- Transmission line exit (typically for sync check)
- High voltage side of the power transformer
Cost of voltage transformer
- 345kV-67V/115V 0.6WXYZ accuracy-burden: ~$10,000
- 138kV-67V/115V CCVT: ~$5,500
- 14.4kV-120V wound VT: ~$1,000
Lead time to procure voltage transformer
- ~16 weeks for high voltage unit
- ~4 weeks for medium voltage unit
Information on cost and lead time is for your general knowledge only. Contact vendor with your equipment specifications for actual figures.