Electrical Troubleshooting Quiz — March 19, 2019
Over the past three years, the plant has had seven unplanned shutdowns due to cable failures. With each incidence, maintenance also tests the adjacent cables and replaces those if necessary. The plant engineer noticed that about a dozen of the replaced cables have failed during this period. Three of them, four times. The unplanned shutdowns have been very disruptive to production; mostly due to the time it takes to replace the failed cables. So, there is a lot of pressure from upper management to stop the failures.
The plant engineer recently got approval to install a surge protection system at the service, and has asked you if there’s anything else to consider. What would you tell him?
You might start with a question. Why is maintenance testing the cables? There is much more to cable testing than simply performing an insulation resistance test. The plant engineer should hire a qualified electrical testing firm to properly assess cable condition during a shutdown scheduled for this purpose. If maintenance is also installing cables, how do you know they are qualified and aren’t damaging the cables?
It’s nice to finally provide surge protection at the entrance, but typically cable-damaging power anomalies originate mostly inside the facility. This plant needs a surge protection system designed for its power distribution system; it’s going to be multi-tier, with different levels of protection at the different voltage levels.
Identify large motors that start across the line, and consider soft start or VFD control to prevent the cable-damaging effects these motors have.