Over the past few years, your insulation resistance testing program has identified a large number of cables that need replacing. The plant manager called you into his office to discuss this. He said he’d been at three other plants with similar programs and they also found cables that need replacing. The difference is in the sheer numbers. He told you, “Something is damaging those cables beyond normal wear and tear. I want you to find it and fix it.”
Where do you begin?
This problem may have multiple causes, but the two most likely are:
- Power events. If you don’t already have a power monitoring system, ask the plant manager to help you requisition one. Install sensors at major loads, not just at the main switchgear. Use portable power analyzers to walk down power quality from the service to various points of use.
- Grounding and/or bonding errors. Conduct a grounding and bonding survey; bond all (noncurrent-carrying) metallic objects and remove load side grounds.
Here are two other actions you should take:
- Look closely at your surge protection system.
- Identify large motors that start across the line; consider soft starters or VFDs for them.
