Posted By Paul Bellis Hi Has anyone carried out a study at all or have any data as to the probability of a catastrophic failure of a transformer in a substation environment. This is in regard to carrying out a risk assessment for operatives working near to (not on) an energised transformer for short periods. Any info would be appreciated on any size Tx or any examples of such failure would be interesting. thanks

Posted By Robert K Lewis This link is to an Australian report of a transformer explosion. http://www.energy.com.au...substation+fire+main.pdf Fire followed by explosion is the normal route to the best of my knowledge. Thus managing fire risks seem to be the obvious control measure. Certainly if there is a catstrophic explosion those close by will suffer major injury and death. Minor failures can lead to fire so these must be anticipated and fire precautions be available immediately in the work area - not in the compound or elsewhere. Bob

Posted By Robert. Depends on the work near the Tx and if there is a chance that the TX or power cables can be damaged, tampered with etc insomuch that the cooling oil is delberately drained or the cooling vanes punctured or the whole thing vandalised to steal copper, alluminium etc. Stuff like that can cause the sub to overheat and then subsequently explode. That, then is devastiating, so check security.

Posted By Paul Bellis Thanks Mitch -will do. what I am looking it is routine entry by authorised persons in the subs -nor working directly on any tx items -but conducting other routine works -and happen to be near the tx. I would asses the likelihood as being low (of a tx catastrophic failure) at this point - but looking for data to back this up -obviously they would be conducting an on site RA before entry - looking for signs of distress or any unusual sounds/smells etc - all equipment serviced and maintained, all FRA and other assessments in place. If the outcome of the RA is high -then perhaps I will be looking at erecting a blast mesh/screen where appropriate, but at present I feel its a LOW risk of a TX explosion -unless anyone knows anything else?

Posted By R Joe You could try ENA (Energy Networks Association), DTI engineering branch (failures reported to them) and HSE (local electrical inspector - ditto). Won’t the substation owner have assessed this both from an operative and public safety, and security of supply perspective, and have information about Tx hours of use Vs failures underpinning their approach to maintenance?

Posted By G M The risk of a transformer or any electrical plant in a substation suffering a catastrophic failure is very very low. As an example Utility companies will ‘happily’ carry out major refurbishments involving dozens of people on site for months at a time with transformers etc still live. As part of the employees training to ensure competence for accessing the substation they will have been advised of how to work safely in that environment. The main point is to spend as little time as you need to in the site and be aware of anything unusual (sounds, smells etc). Beware of any stats that you do get as most failures of kit that I am aware of usually occur shortly after installation or maintenance. Another way to look at it is that if the transformer did suddenly and catastrophically fail it would probably destroy everything within a 100m of it so any measures you could implement would be useless anyway! What kind of work is it that you are going to carry out? A more significant risk is something like induced voltage which has unfortunately caused several deaths over the past few years.

Posted By Garry Homer I have spent decades working alongside transformers without a worry as the chance of one going bang while you are there is very remote. I think I was at a higher risk driving to the substations! Apart from being suitably trained for the usual hazards and logged on to site so if there is a problem on the network, it will not be re energised before you confirm you are outside the substation. You need to use your senses, sight, smell, touch, hearing. The tank should look a regular shape - no bulges or damage to the cooling fins. No oil spill. Nothing should smell hot - hot paint aroma, hot oil etc. If there is a sweet smell be take care as the transformer or some other equipment could contain PCBs so ask the owner. Transformer tanks or connection boxes should not be hot to touch. You get used to the transformer noise so you should notice a change in tone or a completely different noise - never a bubbling noise. Sometimes the noise can be simply a metal ownership label that is loose! - No ticking noises associated with spark discharges. Large transformers have automatic voltage regulation equipment fitted to them that changes the winding ratios using a switching device. These can be very noisy and may startle you if you have never been near one before. Takes a few seconds for the hum to steady after one of these operates. All that said, if it goes wrong, it will be a bloody big bang with hot oil etc spilling forth. An uncontrolled release of heat, light and sound. I have seen a few twisted remains but an investigation usually reveals a cause. If the maintenance is good, then perhaps you will not have a problem. The 'few' is from a system containing thousands. Stats used to be logged by the Electricity Association but that has now disappeared. We used to get feedback on suspect equipment from a national database of incidents or things found during maintenance. If a warning was issued against certain equipment, then access to subs with that gear was halted until everything was inspected. Incidents had only to be reported to the DTi etc if debris was ejected beyond the perimeter of the substation. If the substation contained all the blast material then it was not reportable to the DTi.

Posted By Garry Homer Just to add a little more. If someone turns up to do some switching, then leave the building. Switchgear only usually goes bang when operated, unless the roof is leaking and water has found its way into the switchgear! Garry

Posted By steven n About time too I wondered how long it would be!!!