Reason Magazine 2014 Quartal 2 Seite 15

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though mechanical or chemical action can gradually degrade insulation resulting in a damaging internal short circuit Overload ing water and air leakage into the trans former will result in the insulation degra dation process speeding up If the failure results in internal arcing the insulating oil in the transformer can sometimes be rapidly heated and vaporized resulting in sudden pressure increases capable of rupturing the transformer shell and spraying the oil onto surrounding equipment and buildings Min eral oil is the most common liquid insulation and when released during an arcing event will ignite and burn as either a spray or large pool fire Shuzhen Xu FM Global senior engi neering specialist for engineering stan dards says it is important to be mindful of all of the issues that can help prevent trans former losses ranging from greater care in transporting and installing transformers to regular inspection and ongoing testing and maintenance Improper transportation and installation can compromise the mechanical integrity of a transformer leading to trans former premature failure she notes Testing is really about trying to detect invisible deficiencies happening inside that could lead to trouble she adds Detection can lead to proper preventive action before a failure occurs she says She notes It is important to include bushings and tap changers attached to transformers too when it comes to maintenance They can fail and sometimes their failure can cause serious trouble to the transformer Xu says one more factor to assess when considering potential transformer failures is the electri cal protection system for transformers The electrical protection system is not only the first defense line to help control transformer failure consequences but is critical to pro tecting the transformer from external threats It needs to be properly maintained in order to fulfill this very important function Although forestalling electrical prob lems is generally the most critical focus related to transformers there are other actions that can help reduce potential losses according to Glenn Mahnken FM Global senior engineering specialist for engineer ing standards For instance he says mitiga tion steps for fire can substantially reduce the impact of a transformer failure It is important to ensure adequate space separa tion or fire barriers between transformers and structures so that damages that might occur as a result of transformer failure can be isolated as much as possible he explains TRANSFORMER CHECKLIST To avoid transformer losses FM Global recommends performing proper maintenance and regular testing To determine the risk for each transformer consider taking into account the following factors Water spray protection in the event of a fire is also helpful in limiting the damage severity And of course making use of FM Approved transformer insulation fluids can substantially reduce potential fire problems Conventional mineral oil is ignitable so when a transformer develops problems such as arcing or a short circuit it can lead to a rupture followed by fire notes Mahnken That s why it s important to have electrical protection in place he notes and to use FM Approved fluids For many years FM Approvals a sub sidiary of FM Global has taken a role in examining and approving fluids for trans former operations that can help to reduce the fire and explosion hazards associated with transformers while also simplifying associ ated fire protection These fluids are listed in the Approval Guide which is available online at approvalguide com FM Global Property Loss Prevention Data Sheet 5 4 Transformers also provides extensive guidance on transformer loss pre vention in general And of course notes Mahnken FM Global loss prevention con sultants can provide detailed site specific advice and assistance The criticality of the transformer The lead time required to replace or repair the transformer The fire exposure presented by the transformer to buildings and equipment The effect of transformer failure on system integrity and reliability The service requirements of the transformer The condition of the transformer Source FM Global Property Loss Prevention Data Sheet 5 4 Transformers available online at fmglobal com datasheets ISSUE 2 2014 Reason 15 theLATEST