Vermin is a term that we use for animals, mostly reptiles and birds which cause significant damage or annoyance. These animals love to set up their house in the nooks and crannies where control and protection wiring are housed. These small creatures try to get inside such nooks and corners and sometimes get stuck in electrical machines/installations thereby causing unbearable damages. Of course, they die too!
In certain plants where we served/visited, we have noticed a mouse, lizard, snake, etc. in Electrical Switchgear and Instrumentation Panels. As a part of service, we check complete Switchgears. HT Panel & LT Panel maintenance is done which includes Relay Testing, Breaker servicing, and testing, control panel cleaning and tightening, CT & PT testing. Switchyard servicing and maintenance in the plants is also done.
Warning: Graphic Content Ahead!!
During the maintenance of one VCB of 11 kV panel board, we found two mice inside the circuit breaker which were dead. The question that comes to our mind is as to how these two mice traveled to an 11 kV bus? If the system wasn’t checked or the maintenance had been neglected, these two mice could have led to the breakdown of the system resulting in lacks or in fact corers of damage. Of course, there could have been a risk of the life of individuals working at the plant as well. Besides, this could have led to the transfer/suspension/termination of the members from the maintenance team as a consequence.
When enquired, the maintenance Engineers said that they had applied aluminum tape and puff seal at various holes inside the panel around 2.5 years back. On investigating further, it was found that while applying aluminum tape for the panel, the person might have forgotten to clean the base where the tape was applied. Improper adhesive contact with the panel could be the reason for mice to enter the panel easily. There were around 50 panels but only one panel was found with this kind of problem leaving an error margin of 2%. However, this could have caused the marginally higher loss.
In another such instance, during maintenance of an 11 kV panel board, we found a dead and half-burnt snake inside the breaker chamber. On being enquired, the maintenance team said that they didn’t get the chance to check the complete panel in the last shut down due to the unavailability of required skilled manpower. They also told us that the limited period of the shutdown and the entire panel cubical was checked 3 years back. In this case, out of 35 panels, only one panel was found where vermin proofing was breached. Again the error margin was of 2% and this too could have caused the marginally higher loss.
The word of caution for all the maintenance team members is to check the Switchgear Panels during every annual shutdown or complete cleaning; servicing and maintenance of HT Panels should be done every 2 years to ensure safety and surety. This type of check on regular intervals is not possible in case of Bus bar as its altogether a different issue and requires heavy planning for the complete blackout.
Almost every plant goes for Relay Testing and Breaker servicing every year through the third party. As part of service and cleaning, control wiring simulation and tightening, cleaning of complete panel cubical (front and rear), CT & PT testing (if needed) should be done. For this, Testing/Service Engineer takes technicians and helpers from the contractor and then with the help of indent cleaner, brush, scrubs, blower, tool kits like screwdriver set, spanner set, etc. gets the task done.
Such instances help us understand the importance of vermin proofing of the panel that must be done appropriately and panels must be checked periodically without fail. Negligence in such cases could pose serious threats to electrical installations and people working at the plant. Besides, this could directly lead to incurring heavy losses in monetary terms too.
About the Author
Avinash Singh is an Electrical Engineer with over 11 years of rich experience in Electrical Maintenance, Installation, Testing, and Commissioning of all major Electrical equipments. He is specialized in bringing down Energy Cost of a Plant by reducing electricity bills and increasing energy efficiency. He also reduces plant breakdown cost by implementing proper maintenance activities during routine and shutdown. Through these Case Studies he shares his experience and challenges faced in his work routine with the readers of Circuit Digest.