XFMR is getting warm (pictures)

[aelectricalman]

View attachment C0602-12.BMP

I'm looking for some common reasons why there would be a situation like this. Could the isolators be bad? Notice this is bonded and there looks to be some bleeding. Im not familiar enough with the insides to know if there could be something else going on. thanks for any help.

Click on the link to see the infared pic.

 

[Smart $]

I'm looking for some common reasons why there would be a situation like this. Could the isolators be bad? Notice this is bonded and there looks to be some bleeding. Im not familiar enough with the insides to know if there could be something else going on. thanks for any help.

Those are surge arresters. Click here for a little info on the insides.

If they are not completely "bad", I'll certainly say they are degraded :happyyes:

 

[Hv&Lv]

The second one looks to have been a little hot. What is the date on them? I see the copper tails have aged extremely well unless they have been replaced. I looked at the infared, is this a 25 kV system? I know the arrestors are but the arrestors can be used on a 15 kV system with 25 kV class connectors.
Trying to see when T&B aquired Joslyn...

 

[wirenut1980]

The arrestors certainly appear they are conducting current. Do you have the tools to measure current flow in the tail?

The heating is showing in the MOV's area of the arrestor, but does not show a temperature or relative temperature to the other areas of the arrestor. Is the primary voltage getting anywhere close to the MCOV of the arrestors? What are both of those values? Is the transformer grounded wye-grounded wye?

Some possible causes of this could be:

As others have hinted at, the arrestors are old and need replaced.
connecting line to neutral-rated arrestors on a delta system.
MCOV rating is too close to the system voltage if the system voltage is running higher than nominal.
On a multi-grounded wye primary system, during a single line to ground fault, the unfaulted phase to neutral voltages rise normally less than 125% of nominal, but if the ratio of certain sequence impedances (can't remember off the top of my head) is off, the voltage can rise more than that and get into the MCOV of the arrestors.

I have seen this happen during dry conditions in the summer where the ground resistance is much higher than normal.

 

[aelectricalman]

Im not sure of the date of the xfmr. I think im better off now. Thanks for the help. You guys are always very helpful.

 

[weressl]

View attachment 6965 View attachment 6966

I'm looking for some common reasons why there would be a situation like this. Could the isolators be bad? Notice this is bonded and there looks to be some bleeding. Im not familiar enough with the insides to know if there could be something else going on. thanks for any help.

Click on the link to see the infared pic.

It seems to me that some old surge arrestors were salvaged, perhaps from the previous, failed trasnformer in this place, and forced back into service. Surge arrestors are like check-valves and will leak and eventually fail. The thermal picture is a good indicator that they are 'leaking' and its prime time to replace them (They should NOT have been reused in the first place, if my suspicion is right.)

 

[Hv&Lv]

Im not sure of the date of the xfmr. I think im better off now. Thanks for the help. You guys are always very helpful.

How about the date on the arrestors. They are joclyn arrestors, I can't find out when T&B aquired them.

 

[beanland]

Sustained overvoltage

Sustained overvoltage

You show two surge arresters but not the third. Are all three similar?

If only two are damaged, then there is a reasonable chance that there was a phase-ground fault that caused a neutral voltage shift and this fault was not cleared in a timely fashion. It could have been a broken wire problem where the protection did not see the fault. As a result, the two unfaulted phases were held at high voltage for an extended period of time.

Look at typical manufacturer literature; they provide duration data for specific overvoltage conditions.

These have "failed" and require replacement.