Intermittant Power Interuptions (see photos)

lu302dan

Member
One of our professional buildings is getting power glitches 3 times a week on average causing the backup generator to pick up the load. This building contains our IT dept and has servers as well as other communication equipment. As you can see in the photos, power is remaining constant, but amperage is dumping to nearly zero for a brief period. The metering device was installed at the main 800 amp switchboard on the breaker feeding the generaters transfer switch. The utility company is supplying us with 120/208Y power from a pad mounted transformer within 25 feet of the main electrical room. The utility company has checked out their transformer and informed us that the problem is not from the utility. I suspect a neutral problem somewhere or maybe the main switchgear's grounding electrode conductor has gone bad or been compromised somehow? We have loked for visual signs of problems by opening up all covers on the switchgear as well as all panels throughout the building. No obvious signs of problems. Looking for some experts here that have had similar problems! We have scheduled to have an infrared thermal scan done to the building.

Thank you

Dan B

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brian john

Senior Member
Location
Leesburg, VA
Forget the grounding and grounding electrode issue as it relates to this issue.

The 3 phase 4 wire ATS (transfer switch) will not start the generator on a neutral issue, the ATS's on the normal side senses phase to phase voltage.

There has to be a voltage issue, the ATS WILL NOT START without a voltage issue.

I would suspect an issue with the ATS controls, but

Who is doing your investigation if you are not utilizing a firm familiar with such problems you may well be wasting time.

Have you had an infrared (IR) inspection?

Have the investigating firmed performed maintenance on the gear, performed a fall of potential test (FOP) from the utility line side terminations to the load terminations of the switchboard.

HAs the ATS been serviced, tested, IR'd FOP.

From what you have posted it seems there is quite a bit of investigation missing, just connecting a recorder is not going to be a solution if there is not additional trouble shooting going on.
 
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lu302dan

Member
Further investigating.

Further investigating.

Cashman has inspected ,checked settings and serviced the transfer switch http://www.cashmanequipment.com/Service-Contacts.htm and found no issues. An IR scan of all electrical distrubution is scheduled. The utility company has their recording equipment installed at the service entrance and will be monitoring as long as needed. If you look at the photos, you will see that it shows a drop in amperage during the glitch when the generator last kicked on and transferred load, but the photo shows no drop in voltage?
 

brian john

Senior Member
Location
Leesburg, VA
Cashman has inspected ,checked settings and serviced the transfer switch http://www.cashmanequipment.com/Service-Contacts.htm and found no issues. An IR scan of all electrical distrubution is scheduled. The utility company has their recording equipment installed at the service entrance and will be monitoring as long as needed. If you look at the photos, you will see that it shows a drop in amperage during the glitch when the generator last kicked on and transferred load, but the photo shows no drop in voltage?

Is this the utility report or yours? If this is the utilities, I would expect to see this. If this is your report I suspect the CT's may be on the load of the ATS while the voltage leads are on the line side of the ATS.
 

brian john

Senior Member
Location
Leesburg, VA
All connection points were made at the utility metered section before the transfer switch.
The los of load is due to the transfer of the ATS (I assume) and the ATS is a normal sensing device if normal.utility voltage deviates the ATS senses this and transfers, since this is a hot to hot transfer the transfer is fast but still results in a loss of voltage to the loads.

Then the data is pretty much not pertinent to any investigation other than to prove it is not utility. 95% (maybe higher) of all PQ issues are customer related.

What it is not based on limited knowledge off the problem.

Utility or utility related
A Grounding issue
Most likely not a neutral issue (The ATS is sensing and transferring on phase to phase sensing)

What it maybe

A lose phase connection ahead of the normal sensing
A lose phase sensing lead in the ATS
A defective ATS

I outlined above how I would locate this.

Monitor the ATS LINE SIDE voltage, when the issue occurs and if you see no voltage drop move the leads
Measure the line side sensing at the voltage connections at the control board for the ATS of voltage sensing relays.
 

lu302dan

Member
Transfer switch

Transfer switch

Because the chart does not show any dip in voltage on any of the phases and the dip in amperage is reflecting the transfer of power from utility to generator, I believe that we have a fault transfer switch. Although it was inspected and adjusted by Cashman, I still believe that their is a faulty component within the switch. It is an older transfer switch (8years old). Rather than trying to repair it again we will probably replace it entirely. Sorry guys, we need to fix the problem before the snow flys!
 

brian john

Senior Member
Location
Leesburg, VA
It is most likely not the ATS switch, it is as I said early on the ATS controls or where the controls sensing leads connect to the ATS. IF this is a larger ATS, the easiest and most cost effective thing to do would be to replace the control panel.
 

ATSman

Senior Member
Location
San Francisco
One of our professional buildings is getting power glitches 3 times a week on average causing the backup generator to pick up the load. This building contains our IT dept and has servers as well as other communication equipment. As you can see in the photos, power is remaining constant, but amperage is dumping to nearly zero for a brief period. The metering device was installed at the main 800 amp switchboard on the breaker feeding the generaters transfer switch. The utility company is supplying us with 120/208Y power from a pad mounted transformer within 25 feet of the main electrical room. The utility company has checked out their transformer and informed us that the problem is not from the utility. I suspect a neutral problem somewhere or maybe the main switchgear's grounding electrode conductor has gone bad or been compromised somehow? We have loked for visual signs of problems by opening up all covers on the switchgear as well as all panels throughout the building. No obvious signs of problems. Looking for some experts here that have had similar problems! We have scheduled to have an infrared thermal scan done to the building.

Thank you

Dan B

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First of all the recorder should be monitoring 3 phase voltage not current since, as Brian mentioned, that's what the ATS monitors. The fact that the load current is not dropping to zero and you are monitoring at the service entrance tells me that the line voltage fluctuations are not great enough to cause the ATS to transfer the load to generator( not utility related.)
The symptom you describes indicates that the voltage sensing relay (older ATS) or V sensing circuit in the microprocessor (newer ATS) has an intermittent problem or is out of adjustment. We call it nuisance transferring when the ATS starts the generator and transfers load without reason. We find this to be a common problem and I would bet you lunch on it.
Tell us what the make and model # of the ATS and photos of the ATS control panel would not hurt so we can make recommendations.
 

ATSman

Senior Member
Location
San Francisco
Because the chart does not show any dip in voltage on any of the phases and the dip in amperage is reflecting the transfer of power from utility to generator, I believe that we have a fault transfer switch. Although it was inspected and adjusted by Cashman, I still believe that their is a faulty component within the switch. It is an older transfer switch (8years old). Rather than trying to repair it again we will probably replace it entirely. Sorry guys, we need to fix the problem before the snow flys!
Ok, sorry I did not see the voltage on the chart. But everything I stated earlier still applies.
Your assumption that the problem is in the ATS is on the money.
Depending on the rating (amps) of the switch (and whether bypass type or not) it may make more sense to repair it (rather than replace it) and have proper preventive maintenance performed to restore it to proper operation.
 

robbietan

Senior Member
Location
Antipolo City
One of our professional buildings is getting power glitches 3 times a week on average causing the backup generator to pick up the load. This building contains our IT dept and has servers as well as other communication equipment. As you can see in the photos, power is remaining constant, but amperage is dumping to nearly zero for a brief period. The metering device was installed at the main 800 amp switchboard on the breaker feeding the generaters transfer switch. The utility company is supplying us with 120/208Y power from a pad mounted transformer within 25 feet of the main electrical room. The utility company has checked out their transformer and informed us that the problem is not from the utility. I suspect a neutral problem somewhere or maybe the main switchgear's grounding electrode conductor has gone bad or been compromised somehow? We have loked for visual signs of problems by opening up all covers on the switchgear as well as all panels throughout the building. No obvious signs of problems. Looking for some experts here that have had similar problems! We have scheduled to have an infrared thermal scan done to the building.

Thank you

Dan B
we had an experience here with overly sensitive ATS protection. the ATS would start the generator in the event of a voltage sag. we would normally recommend a time delay (2 seconds) to the ATS protection setting to avoid nuisance trips
 
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