PT's fuse blown

[lume7006]

Hello everybody,

We have found some PT's installed in 230 kV that apparently have no problem, however, their fuses have been blown.
I looked at their name plate data and they are no capacitive.

Based on your experiences, any clues about the possible reasson of this fault?

Best Regards

 

[waross]

The PTs may be failing.
There may have been a voltage transient which saturated the PTs resulting in overcurrent.
Loose or corroded fuse clips.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Marmite]

A fault on the cabling between the VT and the relay panel/metering?
A mistake by someone doing some testing causing an inadvertent short?

Regards
Marmite

 

[jghrist]

Primary or secondary fuse?

 

[dpc]

If these are primary fuses - these small amperage high voltage fuses are somewhat fragile and prone to problems.

David Castor

http://www.cvoes.com

 

[Marmite]

Can you get 230KV VT's with primary fuses? I've only ever come across high voltage VT's with secondary fuses, which will protect the VT from faults on the secondary wiring downstream. I doubt that a 230kV primary fuse would adequately protect the VT even if it was technically achievable.
Regards
Marmite

 

[DTR2011]

I had the same question as Marmite. Typically, HV PT's are included in some kind of zone protection.

I would carefully check the secondary circuits.

 

[rasevskii]

I agree with smallgreek. I have never seen, during my previous time in the field, a 220Kv fuse (or 110Kv for that matter), such PTs are always directly connected on the HV side. Is it possible to even manufacture a 220Kv fuse? Unless it is under oil...

Secondary fuses are standard (or a MCB) located in a box as close to the PT as possible. The LV conductors between the PT and the box are unprotected, therefore as short as possible.

rasevskii

 

[jghrist]

I agree that a primary fuse would be highly unusual, but why would the OP assume that a blown secondary fuse would indicate a problem with the VT, not a problem in the secondary circuit?