Humming 4160 1200A Breaker

[R KVIZ]

We have a 4160V 1200A breaker that has just recently started Humming and it is rather loud. We found it tripped yesterday and we checked the connection after we racked it out and found line and load hot. No discoloration or flash marks. The load on this breaker (490 amp) has not changed in quite awhile. We swapped out the breaker with a spare and still it Hums. We can't seem to find the exact location of the humming.

 

[templdl]

We have a 4160V 1200A breaker that has just recently started Humming and it is rather loud. We found it tripped yesterday and we checked the connection after we racked it out and found line and load hot. No discoloration or flash marks. The load on this breaker (490 amp) has not changed in quite awhile. We swapped out the breaker with a spare and still it Hums. We can't seem to find the exact location of the humming.

Just to clarify, it's a hum and not a buzz. The reason that zI ask is it is not unusual ft or a fastener are structural part to be vibrated because of C current flow through that area because of the mag we tic flux generated by the CV urgent flowing through the breaker. If SD o it may be hard to pinpoint
Since it is MV there are no thermal elements to derate and trip the breaker as there would be CTs driving and electronic trip unit activating the breaker we with a ST.
Obviously it is a draw out with moving and stationary contacts. Which are a good place to review any maintenance procedures.

 

[ATSman]

Because It Doesen't Know The Words

Because It Doesen't Know The Words

Humm.....Something doesn't sound right (pardon the pun ) You state "we can't seem to find the exact location of the humming."
Are you sure it is coming from the breaker? The fact that you replaced it with a spare and still hear it tells me it's not in the breaker.
As Templdl stated there are no thermal or magnetic elements in a MV breaker (as in a LV breaker): the trip unit is either an induction disk or SS protective relay. Inductive Heating (steel frame or structure in the path of the current carrying conductors) can produce a humming sound and excessive heat. With the breaker racked out check to see that a piece of steel has not entered into the current path of the breaker stabs/ fingers.
You found the breaker tripped. Was there any trip flags/ indicators on the relay that would tell what type of fault (LT or Inst) tripped it?
Send us some pics of the breaker and switchgear enclosure.

 

[Jraef]

Maybe it just forgot the words?

Sorry, couldn't resist it... :ashamed: