APC UPS High Input Voltage

[ITGURU]

I have several APC UPSs on site. During the normal week/working day I get no alerts of the UPS compensating for high input voltage.

However, evenings and weekends I get several alerts.

Other than turning off the email alert for this particular alert - is there anything else I need to look at which is causing this?

[3s-gtech]

Could be worth getting your supply checked. If it’s not silly high (i.e. outside of the normal range +-20v or so, you can change the alert threshold I think.

[ITGURU]

Could be worth getting your supply checked. If it’s not silly high (i.e. outside of the normal range +-20v or so, you can change the alert threshold I think.

 

here's the monitoring

[3s-gtech]

Big range. It looks like your school’s supply is not really up to scratch - they’re feeding it 250v and under load it’s dropping to below 220v. Not too far off spec (some on here have reported less than 210v) but the variation is big. Are you fed by a fat three phase supply from a substation, or a rusty oil-cooled transformer nailed to a pole?

[ITGURU]

Big range. It looks like your school’s supply is not really up to scratch - they’re feeding it 250v and under load it’s dropping to below 220v. Not too far off spec (some on here have reported less than 210v) but the variation is big. Are you fed by a fat three phase supply from a substation, or a rusty oil-cooled transformer nailed to a pole?

 

3 phase Substation on the school's site! all underground

[ITGURU]

3 phase Substation on the school's site! all underground

 

This is the same UPS on another part of the site. completely different readings.

 

[3s-gtech]

Wow, well that’s good news! It’s not your feed - you have the same sort of setup as us. You may have the phases out of balance in that area, e.g. too much load on one phase over the others. That’s a lot easier and cheaper to fix if so.

[ITGURU]

Wow, well that’s good news! It’s not your feed - you have the same sort of setup as us. You may have the phases out of balance in that area, e.g. too much load on one phase over the others. That’s a lot easier and cheaper to fix if so.

 

It is still worth getting electricians in to explain the situation? Is it something they need to rectify or nothing wrong with these alerts etc?

We have fixed wire testing every 5 years but guess they don't pick up on things like this?

[3s-gtech]

Oh yes, very much this needs looking at and fixing. If the phases are unbalanced, it’s a case of pulling some circuits out of the RCDs in relevant distribution boards and putting them into others. Not difficult, but needs metering to check.

It could be something else, like a poor connection on a busbar or similar, but it certainly needs looking at.

 

Disclosure: we had an issue with one phase (possibly a heat cycle on the connections) - this caused the main feed for that phase (from the substation) to heat up over many years, melt the insulation and arc onto the busbar for another phase. 300A fuse blew across the room [emoji28]

 

Your fixed testing won’t pick up on this - they check the earths, trips/RCDs and connections in the dis boards - not current/voltage testing IME.

Edited February 27, 2022 by 3s-gtech