Author: Will Morrey
Transformers, switchgear and motor control centers (MCCs) installed decades ago are still running many industrial facilities—often well past the point where OEM replacement parts remain available or protective device settings still match the site’s current fault-current conditions.
The resulting risk isn’t just limited to an unplanned outage. Crews may be working next to equipment where the arc flash incident energy no longer matches the PPE category on the label. Here’s what to watch for, and how a planned replacement can happen without extending a scheduled shutdown.
Warning Signs Your Switchgear, Transformers or MCCs Are Reaching End of Life
Signs that can point to your equipment reaching the end of its life include:
- Unavailable OEM replacement parts
- Thermal imaging showing hot spots at bus connections or breaker contacts
- Declining insulation resistance (Megger) readings across successive tests
- Nuisance tripping with no identifiable operational cause
Obsolete breaker frames and discontinued MCC bucket components are usually the clearest signal that an industrial facility is closer to a legacy MCC upgrade than the maintenance log suggests. If a distributor can’t source the part, the clock has already run out.
IR thermography surveys catch developing hot spots before they cause a failure. Dissolved gas analysis (DGA) trending on oil-filled transformers flags insulation breakdown while it’s still in its early stages. For industrial operators, that trend line is usually the first solid evidence that an aging transformer replacement is coming, well before the unit is forced offline. Enclosure corrosion or moisture ingress points to compromised protection, even when the equipment inside still tests fine.
Why Arc Flash Risk Climbs as Switchgear Ages
Incident energy tends to rise as switchgear ages because degrading insulation and loosening connections increase the odds of an arcing fault. At the same time, the original protective device settings and PPE category on the label may no longer reflect the facility’s current fault-current conditions.
NFPA 70E and IEEE 1584 calculations are only as accurate as the design basis behind them, and that basis can shift with added motor loads, growing utility fault contribution and modified feeder configurations. Without an updated coordination study, that drift goes unnoticed until an incident energy analysis catches up to it, at which point the PPE crews have been wearing may no longer match the actual hazard.
Should You Replace or Refurbish?
Refurbish when the enclosure, bus and insulation are structurally sound and only the breakers, relays or trip units need updating.
Replace when parts are obsolete, the gear can’t be selectively coordinated with modern protective devices or the arc flash incident energy exceeds what available PPE can handle.
A selective coordination study and an incident energy analysis per IEEE 1584, checked against the PPE category boundaries actually in use at the site, are what turn that decision from a judgment call into a documented one.
Replacing Switchgear Without Extending the Shutdown
A compressed shutdown window depends on front-loading two things before the outage starts: a factory acceptance test (FAT) at the equipment manufacturer’s facility, and multiple site investigative visits to verify existing wiring, routing and undocumented field changes.
On a mining client’s conveyor transfer e-house replacement, the driver was a control platform standardization initiative rather than equipment failure. JEPCO coordinated a factory acceptance test between the client, the equipment manufacturer, and our engineering team, and made multiple brownfield site trips to verify existing wiring and undocumented field changes before the shutdown began. Procurement timing and shutdown scheduling were based on what those trips found, so the field crew didn’t uncover surprises mid-outage.
Waiting for a failure to force the decision costs more than a planned assessment does in downtime, PPE that may no longer match the actual hazard and shutdown windows that run longer than they need to. A walkthrough covering thermal imaging, insulation resistance testing and an updated incident energy analysis can provide a factual basis for the replace-or-refurbish call. It can also help scope a shutdown window based on what the equipment actually needs, rather than on guesswork.
FAQs
What are the warning signs that switchgear, transformers or MCCs need replacing?
Unavailable OEM parts, hot spots found by thermal imaging, declining insulation resistance readings and unexplained nuisance tripping are the clearest indicators. However, not every replacement is failure-driven. Some are proactive standardization moves.
Should I conduct an aging switchgear replacement or refurbishment?
You should refurbish if the enclosure, bus and insulation are structurally sound and only components like breakers or trip units need updating. You should replace if parts are obsolete, coordination with modern protective devices isn’t possible or incident energy exceeds available PPE ratings.
How do you replace switchgear without extending a shutdown?
Complete a factory acceptance test at the manufacturer’s facility and conduct multiple investigative site visits before the outage starts, so wiring, routing and undocumented changes are already verified. Procurement and scheduling can also then be built around known conditions.
Will Morrey
Electrical, Instrumentation & Automation Manager
Will Morrey is JEPCO’s electrical, instrumentation & automation manager with a background in industrial I&C spanning oil and gas and mining environments.
