Power Transformer 1

[Mergoo]

i have had 3 alarms on SEL-387A on the primary of 80/107/133 MVA 362.25 - 34.5kV transformer. The alarms are Sudden pressure main tank, sudden pressure LTC tank and Conservator or LTC low oil. my question is, are they all related? would something common has happened that initiated these alarms?

 

[davidbeach]

I'd guess they are related and that the transformer had a really bad day.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[oldfieldguy]

What's your oscillography look like from the 387?

A quick look at the transformer should give you a good idea about the 'low oil' alarms. It takes a good amount of leakage to reach 'low level'. You should see that easily. If that's the case, the question arises as to what caused that amount of oil to get out. Two possibilities: Internal fault, or a bullet hole or other sign of physical impact.

I'd have an oil sample for dissolved gases headed to the nearest lab by the fastest means available and I would NOT re-energize that transformer until I had a complete battery of tests on the oil AND a function test of the alarm circuits.



old field guy

 

[Mergoo]

unfortunately, i do not have access oscillography as i work remotely with the SCADA team.

but i will go ahead and ask to check oil level and take it from there. but what if we don't have a leakage? could it be faulty Sudden Pressure Relay?

 

[stevenal]

Are the alarm contacts wired to a common DC source? Do you alarm on contact closure or opening?

 

[Palletjack]

All three alarms at once, or these alarms come in over a specific period?
I have had alarms come in and the device turned out to be bad.
But with two sudden pressure alarms and not knowing when they came in I would be wary.
Is this XF still hot?

 

[bacon4life]

It seems unlikely to get all three of those alarms without current relays and/or obvious oil spillage.

Are the contacts from the physical pressure/level switches arranged in a "failsafe" configuration? If so, loss of the DC circuit to the physical switches could trip the SEL relay. I remember having some trouble the first time with this the first time I used an SEL mounted inside the transformer control cabinet.

 

[DTR2011]

Have you checked for DC ground faults? Many of them trace back to a transformer accessory.