Reason Magazin 2014Q3 Seite 12

Hinweis: Dies ist eine maschinenlesbare No-Flash Ansicht.
Klicken Sie hier um zur Online-Version zu gelangen.

Inhalt

12 Reason ISSUE 3 2014 theLATEST Transformer Failure II In the last issue of Reason we examined the biggest equipment losses among FM Global clients within a five year period 2008 2013 Transformer loss ranked third among the top five losses and cost FM Global clients a combined US 339 million dollars in lost revenue While the numbers prove that trans former loss is a substantial risk for businesses oftentimes business decision makers deem the risk remote and unworthy of attention A recent indoor transformer failure at a 1 6 million square foot 150 000 square meter automotive related manufacturing facility provides an eye opening example of the risks involved in transformer mainte nance and operation and how quickly things can go awry It was mid morning when the piercing sound of fire alarms notified the guardhouse at the automotive facility and the local fire service that something was wrong A mainte nance manager happened to be in the vicinity of the building an unsprinklered two story electrical building which contained four transformers on the top floor each housed in a separate room Despite seeing smoke and hearing a muffled explosion the manager entered the building in an attempt to isolate the problem transformer Unit A and saw thick black smoke engulfing the area At this point the main 63kV supply to the entire plant was interrupted and on site facility firefighters began to deploy on the lower floor Unfortunately despite this rapid response by the maintenance manager and plant firefighters the situation continued to deteriorate A second explosion was felt fol lowed by a fiery burst of an oil fueled flame It took only 15 minutes for the local fire service to arrive and an hour for the blaze to be fully extinguished but the damage was substantial As is often the case with transformer failures the problem began with an internal short circuit and electric arc In this particu lar case a mineral oil insulated transformer suffered an internal arc and ruptured result ing in the fire that destroyed an adjacent transformer and electrical cabinets In situations like these the extremely high temperature of the arc rapidly heats up the insulating fluid which is often com bustible mineral oil The result is a physical explosion of the transformer s outer shell which occurs from the insulating liquid being rapidly heated vaporized and decom posed causing a pressure buildup In this particular instance and others like it the liquid is then ejected as a spray and if ignited forms a fireball capable of forcing open weak construction such as metal doors and hatches as well as igniting cable insulation and any other combustibles in the room Mineral oil leaking from the rupture point can also form a pool fire that may spread to adjacent equipment if ade quate containment is not provided At the automotive plant two access doors to the transformer room were blown out and the interior of both floors of the electrical building was heavily contaminated by smoke and soot with spalling of the concrete A sec ond transformer Unit B became seriously damaged by heat The fire spread through cable insulation and floor penetrations to equipment linked with Unit A and Unit B cir cuit breakers and attached to electrical cabi Numbers prove that transformer breakdowns disrupt business and cost clients millions in revenue