If your facility has gone a long stretch without an electrical failure, taking that as a sign everything is in good shape is a reasonable thing to do. It is also one of the least reliable conclusions available to you. Electrical equipment doesn't degrade in ways anybody can watch from the floor, so the quiet is not telling you what it appears to be telling you.
What the quiet leaves out
- Nothing has failed recently. Nothing is being measured either.
- A transformer can run above its rated temperature for years with no outward sign.
- Switchgear past its design life still closes and still carries load.
- Nobody is tracking operations counts on the breakers.
- Equipment age against rated service life isn't recorded anywhere anyone could find it.
- Every incident-free quarter reads as one more confirmation that things are fine.
The cost of a surprise
When it does come it tends to come at a bad time, and getting back is slow. Large power transformers and custom switchgear routinely carry lead times in months, and on some equipment past a year. A transformer that failed without warning is not a same-week repair. It is an outage of unknown length, because the part that ends it is sitting on somebody else's manufacturing schedule.
Which is the part worth sitting with. A predictable failure turns into an emergency only because nothing was in place to flag it early.
How this equipment actually fails
It holds right up until it doesn't, and looking fine is exactly what failing equipment does.
A transformer running above its rated temperature rise doesn't announce the strain. It carries the load day after day while the heat eats insulation life, and nothing about that is visible from outside. Aging switchgear and protective relays running past design life behave the same way.
The signals are there. Operating temperature against nameplate, dissolved gas readings in oil-filled units, infrared scans that show a hot connection before it opens, insulation resistance trending the wrong way, how often protection has operated. All of that exists whether anyone is looking or not. The difficulty is that judgment leans on recent experience, recent experience here is silence, and the actual risk is a function of condition and age.
The facilities that don't get caught
Facilities that don't get surprised are the ones that went looking before the equipment had any reason to give them a warning. That is something you can put in place rather than something you have to be lucky about.