Overload Protection for Transformers
Overload Protection for Transformers
(OP)
I might be asking a silly question,
We have a transformer, which is fed from 4160V systrem. On the primary, we have fuse and relay to provide Short circuit and overload protection respectively. On the secondary, we have a circuit breaker(600V) to provide short circuit and overload protection. However, the primary relay is not large enough and overload trip will occur. I am thinking of disabling it since downstream Circuit breaker can provide Overload protection as well, also this is only short period of service, which is about 15mininutes. Any comments would be appreciated.
We have a transformer, which is fed from 4160V systrem. On the primary, we have fuse and relay to provide Short circuit and overload protection respectively. On the secondary, we have a circuit breaker(600V) to provide short circuit and overload protection. However, the primary relay is not large enough and overload trip will occur. I am thinking of disabling it since downstream Circuit breaker can provide Overload protection as well, also this is only short period of service, which is about 15mininutes. Any comments would be appreciated.






RE: Overload Protection for Transformers
Regards
Marmite
RE: Overload Protection for Transformers
Both primary and secondary sides are providing O/L protection. We set primary settings higher than secondary settings.
RE: Overload Protection for Transformers
Alan
"The engineer's first problem in any design situation is to discover what the problem really is." Unk.
RE: Overload Protection for Transformers
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Overload Protection for Transformers
Not needed.
Maybe.. possible only connect PT100 on the transformer ( if is dry) to some monitoring, like to DGPT.
Best Regards.
Slava
RE: Overload Protection for Transformers
I would not choose it for a permanent installation.
In the terms of cost, if you're already forking out money for a 4160 volt installation, the added cost a of a dedicated control power transformer (CPT) is relatively small.
If you're modifying aging equipment to upgrade protection and control, it makes no sense to add several bad failure modes by using a PT to do the CPT's job.
System protection is not well served by compromises of this depth. Most of us in system protection tend to be conservative because most of us are still remembering horror stories that start with "that should be good enough" and "I never expected THAT to happen."
old field guy
RE: Overload Protection for Transformers
RE: Overload Protection for Transformers
By CEC rule #26-252(4) and Table 50 you can use fuses up to 200% of the transformers FLC if the transformer impedance is between 7.5% and 10%.
If the transformer is less than 7.5% impedance you may fuse the primary at 300%.
This is contingent on proper overload protection on the secondary side.
Again from Table 50, For a breaker that is not more than 250% of the rated current of the transformer.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Overload Protection for Transformers
RE: Overload Protection for Transformers
If you want a definite answer, you must tell us:
A> KVA?
B> Wet or dry?
C> Setting of secondary breaker?
D> % Impedance?
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Overload Protection for Transformers
Alan
"The engineer's first problem in any design situation is to discover what the problem really is." Unk.