12.47kV - 480V delta-wye xfmr being backfed. How to protect mains?

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JedahB

Member
Location
Greenwood, IN
Hello. I have a situation at I have a 500HP motor/dynamometer being used in regen mode so it is generating power instead of consuming. The concern that was brought up is how to protect our main and xfmr in our substations when we have power flowing backwards from our motor. I do not think removing the ground strap on the primary is applicable in this situation as is recommended by power gen manufacturer because the transformers are being use as intended and then occationally have power flowing back through them.

How do I protect my mains in the sub from tripping with this situation?
I am new to his forum so I am not sure what other information is needed. Thank you all very much for the assistance.
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R

rcwilson

Senior Member
Location
Redmond, WA
If your motor is protected per code by an overload relay, fuses or circuit breaker, and the transformer, main breaker and circuit to the motor is adequate for running a 500 HP motor, your system is protected when the motor is generating. If the motor regenerates more power than your facility draws from the utility, you could be violating utility regulations and have to add protection similar to a solar panel inverter or wind turbine to prevent backfeed to the utility.

Don't remove any grounds from the transformer. The neutral to ground bond is needed for safety and proper operation of the power system.
 
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JedahB

Member
Location
Greenwood, IN
Thank you very much for the replies.
The xfmr and the circuits powering the motor are adequetely size and are protected. The concern is at the substation that feed a good number of these regen motors. The fear is we will generate so much power with the motors that the substation xfmr will be damaged or we will trip the main breaker in the sub.


Phil, I apologize, but what is POCO?
 
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