Expert demands cause analysis for future safety
THE DEATH of an employee due to serious burn injuries on October 20 as a result of blast a week earlier at Kalyani Devi power sub-station in Allahabad has prompted an expert of Motilal Nehru National Institute of Technology (MNNIT) Dr HS Goyal to demand an investigation into the possible reasons of the blast and the resulting fire for future safety against similar tragedies.
In the past few months many incidences of blast and fire in the 11 KV oil cooled switchgears and also in transformers have been reported.
"The oil filled switchgear is extensively used for the distribution and utilisation of electrical power. Oil is still used by some manufacturers. However, it has, now, largely been replaced by non-flammable substances, vacuum or air in some countries," say Dr Goyal, assitant professor in the Mechanical Engineering department of MNNIT.
Dr Goyal says that the oil-filled switchgear has a proven record of reliability and performance. "Failures are rare, but when they occur the results are usually catastrophic. Tanks may rupture in a brittle manner resulting in the ejection of burning oil and gas clouds, causing death and serious injury to persons and major damage to plant and buildings in the vicinity of the failed equipment.
Accident experiences reported in Engineering journals report that failure occurs at or shortly after operation of the switchgear," he said.
Dr Goyal said that the way switchgear is operated, its form of construction, the condition in which it is maintained and the circumstances existing at the time of operation to a large extent determine whether the switchgear will perform its duty safely.
"Under a normal situation, the non-conducting transformer oil absorbs heat produced inside the Link box to transformer and dissipates the heat to atmosphere. The moisture content in the oil or the carbon content in oil greatly influences the oil insulation characteristics and hence the resultant rise in temperature and pressure," he said.
Other than the heat generated inside the system due to its own energy source, environmental conditions such as the intensity of microwave radiations may also influence the oil characteristics. "Transformer oil absorbs microwave radiations significantly and that can influence the temperature and pressure inside the tank leading to blast and fire.
In the Kalyani Devi incident, the blast occurred in the morning hours when the load on the system happens to be less than optimum experienced during peak hours and that makes matter more alarming," Dr Goyal said.
He said that the high power microwaves are a reality and most advanced weapons of the developed world are those which cause the damage in a confined region in disguise of a normal system fault.
"Our engineering systems need to be made sensitive enough to diagnose the system failure based accidents from possible high technology sabotage based failures. For that – confidence on system design and maintenance needs to be enhanced by way of ensuring proper quality checks and timely technical audits.
If one sub-station can burst into flames leading to death and injury to attendants— due to unknown cause— similar incidents can not be ruled out without proper safety checks and corrective steps in totality," he warned.
Dr Goyal said that the design and manufacturing firm of the failed component should voluntarily conduct safety checks and should suggest corrective safety measures on similar installations taking the Kalyani Devi incident as an example.
"Proper safety measures against such repetitions should include high temperature alert for tank fluid and microwave alert for the environment.
Unfortunately, in our country the risk of a punitive action against the staff concerned without going into detailed research based investigations hamper even the proper record keeping of such industrial disasters and also restricts the future corrective steps for engineering system safety and that should not happen," he added.
Dr Goyal said that the aim of engineering investigations should not be punishment to staff but it should help in planning system improvement.