Hazardous materials


FOCUS


Photo Credit: Shutterstock When a fire does occur, it can put a


transformer out of action, in addition to causing serious damage to the surrounding equipment. This can be particularly devastating in highly populated areas, where transformers can feed critical assets such as schools or hospitals. Additionally, this could cause a risk to business continuity, potentially causing major disruption and delay to operations.


Transformer failure


Fire and transformer failures are commonly linked, but the failures themselves are caused by a number of factors. Transformer failures are usually caused by a combination of electrical, mechanical or thermal issues. According to insurer FM Global, mechanical and electrical failures of components are the main cause of unplanned outages in power transmission and distribution in Europe. The most common factors in transformer


failure include lightning/power surges; overloading; inadequate maintenance; loose electrical and mechanical connections; insulation deterioration; criminal damage; and moisture ingress. In addition, the condition of the


transformer plays a significant role in failure. For example, an overloaded transformer with a well maintained insulating fluid is much less


likely to fail than the same unit that has had little or no maintenance. Over the past 10-15 years, the second leading cause of failure has been insulation deterioration, which is also linked to moisture ingress, since water accelerates the ageing of cellulose paper. Fire is a common outcome of these failures – and this is a result of the hydrocarbon based mineral oil being used as a dielectric and cooling agent. Failure of a piece of transformer equipment, such as an oil filled bushing or onload tap changer, can lead the bulk oil in the ignition tank to ignite. A fire event, caused by this ignition of flammable insulation oil, will cause catastrophic failure of the transformer.


Risk mitigation


While mineral oil still makes up the vast majority of the transformer fluid market share, there is an alternative that minimises the risk of fire. Ester fluids are a fire safe and biodegradable alternative to mineral oil, and are increasingly being chosen by power utilities and end users to minimise fire risk. Unlike mineral oil, the relatively high fire point and low calorific value of esters ensure that they will not sustain fire under all transformer fault conditions. No fires have been reported since the use of esters started almost 40 years ago.


www.frmjournal.com APRIL 2018 29


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