Transformer seconday side Breaker
Transformer seconday side Breaker
(OP)
a 750KVA ANN transformer secondary side breaker is ordered with a 1000AMp LTP and fixed LTD . This is 1.4 times more than Tx FLA at 600V. Breaker is rated for 100% rated name plate operation.
Two issues is first the primary S&C fuse at 25KV does not coordinate with a 25 AMp fuse ( they touch at LTD) and the bigger size would violate the ESA ruels for more than 1.5 times of primary amps.
Does the consulatnt pick a wrong size breaker?
I dont think the breaker would provide adequate transformer protection with that size breaker.
Two issues is first the primary S&C fuse at 25KV does not coordinate with a 25 AMp fuse ( they touch at LTD) and the bigger size would violate the ESA ruels for more than 1.5 times of primary amps.
Does the consulatnt pick a wrong size breaker?
I dont think the breaker would provide adequate transformer protection with that size breaker.






RE: Transformer seconday side Breaker
RE: Transformer seconday side Breaker
RE: Transformer seconday side Breaker
NDC,LSIG, Non adjustable Rating Plug 1000
RE: Transformer seconday side Breaker
The question is if that size breaker is aequte for transformer protection.
RE: Transformer seconday side Breaker
RE: Transformer seconday side Breaker
RE: Transformer seconday side Breaker
Is this a padmount transformer? If so, they're usually equipped with internal primary fuses. Standard here are
RTE Bay-0-Net 358C 25 A.
If you really want to lower the LT pick-up, you can replace the 1000 A rating plug with a 800 A, for a better overload protection.
RE: Transformer seconday side Breaker
you are right. it is rated at 80%. so does this mean in SKM I have to use a 800 plug instead of 1000 Amp plug to count for 800A ratings. by the way LTD is also fixed.
RE: Transformer seconday side Breaker
The 1000 A breaker will still have a time-current curve based on the 1000 A trip plug and related LT pickup settings.
RE: Transformer seconday side Breaker
The Long Time Delay is fixed at 1 x rating plug and 12 sec delay.
BTW, your trip unit seems to be a RMS310. If you can adjust
both SDT pick-up and delay, then the SDT has a flat caracteristic. If there's only one knob to select STD
pick-up, then the delay is fixed at 100 msec and has a I2t caracteristic.
Those are tricky ones...