In article , "T" wrote:
A raised floor server room with 6 servers, fiber optic patch panels, large
control system cabinets and large UPS system, has been recently been plagued
by computer power supply failures. The supplies fail when apparently many
tens of thousands of volts jump from inside the PS around the switching
regulators to the chassis of the supply taking out all the components. This
has happened to 8 supplies so far. A visible blue flash has been witnessed
several times by pewrsons in the room.

The servers so far affected are all sitting on the raised computer center
floor. What ususally happens seems to be when a person enters the 12x20ft
room or gets near a server a large snap is heard and the server is on the
backup redundant PS, if it has not already failed.

We have been adding grounding bonding from all computer case to the bldg
steel, raised floor structure, etc to try to stop this. Its still happening.
The computers are various brands and varoious ages, from 1 week old to 5
years old. The probelm began occuring 2 months ago. The data center was
built 12 years ago.

We are at a loss to figure out how the charge is building up on the inside
of the power supplies. I am thinking about the common power source, via the
power cords Hot, Neutral and Ground conductor.

The green wire should be bonded to the PC case. Apparently the PS regulator
board floats above chassis potential. Apparently a large potential differnce
is building. It jumps a 1 inch gap to the chassis. Burn marks from repeated
arc overs are evindent (the arc that makes it fail is not the 1st time it
occurs!)

The Hot and Nuetral..how could a charge be coming in on these conductors and
getting past the MOVs to build a potential on the boards.

It sounds like your UPS's should take care of everything.
I woulds have the UPS's checked out. I would have building electricians
check things out. I would have installed whole circuit transient protection
at the breaker box feeding the room.

greg