Drawbacks of Station Service on Autotransformer 1

[111R]

What are some of the drawbacks of using a small 25-75 kVA station service on an autotransformer tertiary? The tertiary is sized for around 35% of the transformed current rating of the auto. The only load on the tertiary is the station service.

Are there any issues during normal or fault conditions that would make this application undesirable when compared to having station service supplied by a distribution transformer on a nearby feeder?

Thank you

 

[cranky108]

1. When the auto transformer is out of service, so is station power.
2. How do you detect a phase to ground fault on the tertiary?
3. What voltage would you use for lighting arresters?
4. The voltage would be unregulated.
5. A ground fault on the tertiary would stress the other phase insulators, thus they would need to be rated for the phase to phase voltage (larger than the expected voltage).