A UK investigator was on the Island yesterday trying to pinpoint the cause of the sudden failure in a Belco switch gear room which plunged the Island into darkness.

The EA Technology expert is trying to cast a broad net over the workings of the Belco plant and will take the findings back to a laboratory.

The independent investigation was launched after last Thursday's fire which led to Island-wide blackouts.

The identity of the investigator has not yet been made public, but a statement about failures in switch gear rooms has been released on the company's web-site.

EA Technology's materials and failure investigations lead consultant, Anne McIntosh, said such failures were often sudden and catastrophic, causing considerable collateral damage to other equipment and sometimes resulting in injury and death.

Ms McIntosh started her explanation into the cause of power plant equipment by saying: "Failures of medium and high voltage electrical assets often make headline news, such as the recent underground cable failure which resulted in 20,000 Liverpool homes being without power, or the transformer failure that left 250,000 Madrid residents in darkness.

"Operators therefore need to be prepared for the possibility of prosecution under Health and Safety regulations, as well as apportioning financial responsibility. Charges may even include corporate manslaughter," she said.

She said the main role of an EA Technology forensic investigator was "to determine the primary cause of each failure and present recommendations for preventing similar occurrences in future".

The reason for a sudden and catastrophic failure of the type which took place in the early hours of last Thursday were many and varied.

"Failures are usually caused by one or more factors, including design, materials selection, fabrication and processing, operating and service conditions, human error, vandalism and illegal activity.

"For example, meticulous examination following a catastrophic failure of an oil filled circuit breaker identified a polyvinylchloride (PVC) ring within the dashpot. Over a period of time, the plasticizers within the PVC leached out into the oil, causing the ring to shrink and harden. This resulted in incorrect operation of the circuit breaker and arcing between the slightly opened male and female contacts. Further arcing occurred, generating explosive gases, which blew the tank lid off. It was recommended that the PVC ring be replaced by a high grade nitrile rubber, which is resilient to oil."

The world-leading UK firm will cast a broad net over the workings of the Belco plant and then take their findings back to a laboratory.

"Initially, a failure investigation should be directed to collecting all the relevant background and historical information," she said. "This information should include reconstruction of the events leading to the failure, manufacturing histories, service records, operational conditions and details of any repairs, maintenance or modifications. This information can be of great help in understanding the failure mechanism."

Electron microscopes and chemical analyses are utilised in their investigations.

And recommendations will be given to Belco to ensure "similar failures do not occur in the future".

"Making sense of the often charred and twisted results of an equipment failure relies on two approaches, used in tandem: sophisticated laboratory techniques, plus expertise in interpreting evidence and patterns of events, based on nearly 40 years of similar investigations," she said.