Power monitoring equipment or services

[buzzbar]

Hi,
I did a service call recently for a bank. They said that they have 'blown' 5-6 power supplies on various desktop computers throughout the bank. We went there, and tested the power, opened up the panel, checked all of the connections in the panels, and everything looked fine.

It's a large bank, so we didn't have time to open up every receptacle box to check for an open neutral, or other bad connections, but all receptacles tested out fine.

I was thinking that we could setup a 'power monitoring' device that would show over a 24-hour period to see if there were any voltage fluctuations. Does anyone have any experience with such equipment? If so, did you rent it? Buy it? Or hire a company that specializes in this?

Any input would be appreciated.

Thanks!

Andy

 

[MasterTheNEC]

@buzzbar

I have very limited experience with this. However, I do have one experience that I can share. In order to monitor a situation where fluxing voltage was a concern the local POCO installed a device to measure the voltage changes and current draw averages over a 30 day period. This was done by calling the POCO and having it set up. Now, keep in mind that the XFMR was utility owned so it was in question. If the bank owns the XFMR as the service point then a call to the POCO may not help but it is just a suggestion.

Sorry I could not be of more assistance. There are some "engineers" on here who may have more in-depth details to add.

 

[zbang]

How old were the computers? Older desktops had a voltage selector on the PS while many newer ones, and pretty much all laptops, are good for 100-240v. A loose neutral on 120/240 or 120/208 wouldn't kill one of those. Has anything else toasted?

 

[mayanees]

Power quality monitoring

Power quality monitoring

Andy,
To look at the Utility source voltage, you could rent a Power Quality monitor like the Fluke 1735 and connect it at the service point. I go to Dave Gibson at Intellirents. He can walk you through the CT and PT requirements. Leave the metering connected for a period of time, say 7 days. Download the profiles, and the Fluke software does an analysis for conformance with the new ITIC or old CBEMA curves to flag any anomalies.
Similarly you could use it inside the building on panels in the problem area and note Power quality parameters like Harmonics, and V/I distortions. In order to find a problem you may need to do some device switching to recreate whatever scenario caused the problem. The Fluke does waveform pre- and post-event capture that helps in locating possible source problems.
The best thing about it is that the metering software makes you look good by flagging problems and even recommending solutions. But make sure your rental company contact is knowledgeable. Dave from Intellirents bends over backwards to help, from pre-rental assistance, to day-of support in the field. I don't mean to sound like an advertisement, but I do highly recommend the guy.

 

[ATSman]

Utility Line Voltage Transients

Utility Line Voltage Transients

Hi,
I did a service call recently for a bank. They said that they have 'blown' 5-6 power supplies on various desktop computers throughout the bank. We went there, and tested the power, opened up the panel, checked all of the connections in the panels, and everything looked fine.

It's a large bank, so we didn't have time to open up every receptacle box to check for an open neutral, or other bad connections, but all receptacles tested out fine.

I was thinking that we could setup a 'power monitoring' device that would show over a 24-hour period to see if there were any voltage fluctuations. Does anyone have any experience with such equipment? If so, did you rent it? Buy it? Or hire a company that specializes in this?

Any input would be appreciated.

Thanks!

Andy

We have investigated many incidents where customer equipment was damaged due to voltage transients coming from the 12KV utility line. One was traced to a faulty switch blade on a Power Factor Correction Capacitor Bank. Every time at around 6:00AM when the switch would operate it sent a voltage spike that traveled thru the line and the stepdown transformer to the 208V or 480V customer's equipment. The spike punctures the insulation causing fuses to blow and rectifier PCB's to fry. Another time the PFCCB shorted to ground intermittently wiping out (40) rectifier modules causing $250,000 equip damage, alone.
A Line Disturbance Analyzer is the only way to capture these very quick impulses (micro-seconds) such as mentioned by others. We still use a Dranetz 658 meter which give good graphics of the wave (not like the newer Flukes!)
Once the culprit is identified you can contact the POCO for resolution. Then you can recommend that the customer have SPD's (surge protection) installed all over their distribution system to help mitigate the problem.

 

[buzzbar]

How old were the computers? Older desktops had a voltage selector on the PS while many newer ones, and pretty much all laptops, are good for 100-240v. A loose neutral on 120/240 or 120/208 wouldn't kill one of those. Has anything else toasted?

As far as I know, nothing else has been 'toasted'. It seems odd to me that only the computers were damaged.

 

[cadpoint]

I'm at a plant now that tests panels all the time.

What no one is mentioning is that based on the panel layout your
equipment might be hanging out of the panel and the panel is not
completely closed but a physical barrier is erected and flagged off.

 

[bob]

Had something similar. The several of the people had some old adding machines on their desk. Every time they hit the
add key, the machine put out a 300 volt spike. After a few of these, the mother board died. Had no problem with
the power supplies.

 

[DonP520]

Damage to Computer Power supply's

Damage to Computer Power supply's

How old is the building? I was the general forman on the new construction for an Apple tecksupport call center and during the finial computer testing prior to operations. There was a issue that the computers were going down intermittently. The cause affect found was a small refrigiator under a desk was causing the intermittent issue, but a bond on XO in the Transformer to the case, the paint was not removed to allow a good bond. Every time the frig cycled it caused a voltage drop to 60 volts. Hope this helps Good luck!

 

[Timbert]

As far as I know, nothing else has been 'toasted'. It seems odd to me that only the computers were damaged.

Seems odd to me too. Although computers tend to make up the majority of electronic equipment in an office environment.

Is there something else in common with the PCs? Such as the network? I doubt it would cause power supply faults but you have to wonder. Is there a common UPS or subpanel? Do they have any surge suppression? are the MOVs still OK?

Another thought would be the age of the PCs. Could all of these PCs neared their end-of-life together? If it's a large enough bank and lets say the PCs were ordered as a lot they could begin dying similar deaths. I remember the power supply on my personal computer died and when I went online there were a lot of complaints about that power supply model dying at 2-1/2 years old (too bad for the manufacturer as they had 3-year warranties--which they did honor).

Don't get me wrong I think looking at the incoming power is the right thing to do, just keep looking for something that explains why it seems to be limited to the computers.