Pursuant to your comment, I remember being told by a credible source at work
of a retirement gift that the water treatment plant operator gave to one of
the employees at said employee's retirement party. A small burned out bulb for
the graphic panel. It turns out that earlier in said employee's career, he was
changing a graphic panel light bulb on an annunciator panel and shut the
entire water treatment plant down. When the bulb shorted the control fuse blew
at an EDC (Electrical Distribution Center) some distance away, a contactor in
a 480 MCC (Motor Control Center) in that EDC dropped out. This caused the pump
associated with the contactor to stop, and the situation steamrolled in terms
of one system affecting another. Before they knew what was happening, the
entire water treatment system had ground to a halt. It was the very same bulb
that was offered as the retirement present. (as a joke I trust)

There are still systems in existence today at the plant where the inadvertent
grounding of the graphic panel or field pushbutton light would open the
control fuse and hence the MCC contactor would drop out. Most of the systems
are redundant, but when one of the redundant systems is locked out for
service, the loss of the other due to a simple sort caused when replacing the
bulbs can have relatively serious affects. At these times, when possible, I
refrain from replacing indicator bulbs. If I do need to change them, extra
care is taken in the process.

Regards.

In article ,
(WShoots1) wrote:
told my co-workers that the power outage problems occurred after a new
employee at a hypothetical power plant said "hey, what's this switch do?"

LOL About 50 yearsago, I worked in Hughes' airborne radar factory. A new 250 KW
peak system was on the floor for demo to the Air Force. A tunable magnetron was
planned but they weren't yet available, so a standard single frequency one was
used.

Anyhow, while a group of AF suits stood around the demo system, some one in the
group leaned out and depressed the Magnetron Tune button. There was an instant
smoke and fire throughout the wiring harness. Some dummy who drew the diagrams
or some dummy on the production line put in a jumper wire across the + and - 28
volts terminals where the tunable magnetron motor would get its power.
Apparently it was thought the jumper was need to complete the system's 28-volt
circuit.

Bill, K5BY

Never say never.
Nothing is absolute.