Oil hazards When a fire does occur, it can put a
transformer out of action, as well as 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.
Mitigate the risk
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. Compared to mineral oil, the relatively high fire point and low calorific value of esters mean 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. The fire point of ester fluids – which represents the lowest temperature at which the vapour of the fuel will burn for at least five seconds after ignition – is greater than 300°C. Ester fluids provide a much more sizeable
buffer between ignition and the ambient air temperature, providing vital protection against fire. Even when ester fluids are inside a transformer in a hot climate, their temperature
would have to rise by at least 170°C to ignite – a massive 130°C more than mineral oils.
Regional fit
Different climates bring different challenges for transformers, and extremes of both hot and cold can pose a failure – and fire – risk. In the Middle East, for example, overheating transformers pose a constant threat to utilities. One such event occurred in July 2017, when a transformer fire at the Saudi Aramco Mobile Refinery at Yanbu in Saudi Arabia was caused by hot weather. On this occasion, the fire was quickly contained, but the extreme temperatures in the region lead to the threat of a far more destructive blaze being ever present. Elsewhere in the Middle East, transformers in
Kuwait are designed for an ambient temperature of 58°C – this is the air that is used to cool the transformer fluid down before it is returned to the transformer. Once back inside, the temperature of the liquid can reach 100°C in a large transformer, or even as high as 130°C in a small transformer – only some 40°C below the fire point for mineral oils. This means that a fault or a hot spot in the transformer would only need to cause a modest increase in temperature to ignite.
Greener option
The benefits of ester fluids extend beyond minimising fire risk. Unlike mineral oils, they
FOCUS
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