something strange happened during a storm with my UPSes

[raphael75]

In our home office room we have 1 UPS that has 2 desktop computers plugged into it, and another UPS on a separate outlet that has 1 desktop computer plugged into it. Yesterday we had a rain storm, but there was no thunder or lightning. All of a sudden, both UPSes shut down and the one that has the 2 computers plugged into it, those 2 computers shut off.

There was also a very loud POP sound, but I couldn't tell where it came from.

I checked the circuit breaker, and it did NOT trip.

The lights flickered slightly but didn't go off for more than half a second or less.

I was able to turn both UPSes back on, and all the computers seem to be working as if nothing happened.

Do you have any idea what might have happened, or if I should have an electrician check this out?

Any idea what the POP sound was?

 

[andre_luis]

Many of these cheap UPSs operate by default having the output connected directly to the mains input via an internal relay, which means that the minor noise in the mains will pass almost entirely to the power supply of your PC; in other words, these equipment meet the cost requisite, but not the protection; For a slightly safer scheme, consider a double conversion isolated UPS.

 

[BradtheRad]

Possibilities:

* During the rainstorm lightning struck a high voltage distribution wire several miles away (distant enough for the thunder to fade). It caused a surge which shut down your UPS units so that they acted as a surge protector. (If it were a blackout or brownout then its function is to supply power.) Since everything works normally then nothing further is needed.

* Do you have a spark arrestor anywhere? Near a tv antenna lead? In the circuit breaker box? An air conditioner exposed to the outdoors? A buildup of static charge might spark with a popping or snapping noise. This wouldn't shut down your UPS but be another sign you had an electrical event cause several more events.

 

[D.A.(Tony)Stewart]

A good UPS won't shut down with a line transient and always supply battery powered inverter output.
I don't know if your have tested your UPS's for power disturbances, brown-outs or interruptions, but now would be a good time to test them with breaker interruptions and service it for fused open protective components.

A pop is an overvoltage arc in air or across an MOV or capacitor from an excess voltage line transient. Good line filters can greatly attenuation kV line transient ought to be std. features of a good UPS.

Florida has the highest lightning strike rate in the US and many power poles have lightning antenna on top. Otherwise, the power meter is rated for 6 kV ionization clamp for over 100 kA but lower transients can sneak thru and some designs only protect to 3kV or 4kV. Good line filters greatly attenuate. Protection to 6kV or 8kV impulse of X [J] demands advanced designs.