When It Goes Wrong

[westie101]

Possibly due to heavy loads due to the cold weather means the trannys are running at or above maximum for low periods of time.

Sorry, no prize. The Ambleside one was a switchgear explosion, the transformer can be seen in the photos virtually undamaged.

I cannot ever recall an incident where a transformer caught fire due to overload, and in the second incident doubt that two CO2 extinguishers would put out a transformer fire owing to the quantity of oil they contain.

All our distribution transformers are capable of a fairly continuous overload of 136% at this time of year

 

[mfarrow]

All our distribution transformers are capable of a fairly continuous overload of 136% at this time of year

I was told awhile back that there are no oil samples ever taken of transformers on DNO equipment. Is that still true, even under/after overload conditions as described?

Also, the first set of pictures appear to shown a box load of (presumably) ruined fuses next to the burnt out switchgear, on the right. Is this typical of most substations? Ours carry perhaps a set of each type on a rack, but never that many.

 

[westie101]

I was told awhile back that there are no oil samples ever taken of transformers on DNO equipment. Is that still true, even under/after overload conditions as described?

Correct, the only time we taker samples is prior to changing transformers to check for the presence of PCBs.
Experience over the years has decided that oil sampling is rarely needed as we do monitor load and tend not to overload them!

Is this typical of most substations? Ours carry perhaps a set of each type on a rack, but never that many.

We generally don't keep fuses in substations or use them as a store room. Ample supplies are available 24/7 at depots. Why those were there I don't know

 

[TheKeymeister]

I was told awhile back that there are no oil samples ever taken of transformers on DNO equipment. Is that still true, even under/after overload conditions as described?

Correct, the only time we taker samples is prior to changing transformers to check for the presence of PCBs.
Experience over the years has decided that oil sampling is rarely needed as we do monitor load and tend not to overload them!

Interesting, just finished our I&M programme for this year, ours are sampled every 12 years

 

[viewer]

Accepting the need for national park (etc) disguises and the very low failure rate for the equipment, is there any requirement for explosion/fire to be taken into account in the design of the buildings? Most chemical plants would have a structure designed to send an explosion upwards and prevent spillage - so generally something like strong fire resisting walls and a roof with weak panels. Just curious.

 

[westie101]

Accepting the need for national park (etc) disguises and the very low failure rate for the equipment, is there any requirement for explosion/fire to be taken into account in the design of the buildings? Most chemical plants would have a structure designed to send an explosion upwards and prevent spillage - so generally something like strong fire resisting walls and a roof with weak panels. Just curious.

Historically no, as generally anything untoward is contained within the gear (and with a large number of outdoor sites a major failure would be uncontained)
Having said that modern fibreglass enclosures are designed with lifting roofs to vent anything, more to protect the enclosure

 

[Scoby_Beasley]

After all that you end with a preposition.

No wonder the country is in a mess.

After having a chat with my fireman mate yesterday he basically confirmed what westie has said.

The duty officer will arrive on the first pump and make a decision. If the switch gear etc. itself is on fire they would (possibly) use a CO2 extinguisher which every pump will carry. So that would be 30-35 seconds per pump in attendance. Water curtains etc. would be set up to protect adjoining properties. Then its down to the DNO to call the shots.

We then got back to the important business of the day of supping beer, picking losing donkeys and mentally undressing the new barmaid.

 

[bernardgreen]

All our distribution transformers are capable of a fairly continuous overload of 136% at this time of year

Just idle curiosity but what temperatures can a transformer reach in normal operation and in tolerable overload ? I ask as friends saw one that appeared to be steaming when snow was falling on it suggesting it was a bit warm.

 

[JohnW2]

Just idle curiosity but what temperatures can a transformer reach in normal operation and in tolerable overload ? I ask as friends saw one that appeared to be steaming when snow was falling on it suggesting it was a bit warm.

I don't think that's necessarily an indication of an extremely high temperature - it's not ususual to see 'steam' rising from a warm/hot road surface when precipitation falls on it.

Kind Regards, John