Power Quality as a Whipping Boy

Every so often I get supporting info with a power audit that reads something like this:

“Inordinate number of issues occurring with equipment as compared to other sites and systems. Everyone is in agreement the power sags, but questions if this has an adverse affect on the equipment.”

True Confession: It gives me a little bit of pleasure to find not a single facility or utility voltage sag in the resulting data. Power quality becomes, at times, the convenient excuse for equipment problems that are actually rooted in operator error, inadequate design, improper installation, inadequate servicing, environmental conditions, etc. When people confidently sling around power quality as the one known reason for problems, it’s almost always a good sign there’s something else going on.

Parkview Mains

Facility / utility voltage. We see a local outage, a small drop in voltage during emergency power system testing, and voltage flicker. But no serious voltage sags.

In this case, associated monitoring on the output of a UPS system showed perhaps the real problem – severe voltage sags associated with load switch-on. The UPS is either undersized for the applied load or in need of adjustment or maintenance. Yet another case of the “solution” being part of the problem.

Parkview UPS

UPS Output. Minor voltage drop during equipment operation, and severe voltage sag related to switch-on / inrush, points to a UPS that is undersized or in need of adjustment or maintenance.

Parkview Inrush

Load inrush current, with visible collapse of UPS output.