277 volt phase dip to 180 volts

[dpm457]

I have a Fluke logging meter set-up in a 4000 amp 277/480v service. One event showed A phase voltage dip to 180.9 volts for 0.327 seconds. Is this dip long enough and low enough to create problems for PC's, UPS, and other electronics? A phase is consistenly running between 267-271 volts, B & C phase 273-276. Amp loads are balanced +- 10%.

 

[ptonsparky]

I have a Fluke logging meter set-up in a 4000 amp 277/480v service. One event showed A phase voltage dip to 180.9 volts for 0.327 seconds. Is this dip long enough and low enough to create problems for PC's, UPS, and other electronics? A phase is consistenly running between 267-271 volts, B & C phase 273-276. Amp loads are balanced +- 10%.

Was this only one event or recurring? If recurring, how often?

 

[dpm457]

Was this only one event or recurring? If recurring, how often?

There have other dips on A phase- down to 238.2 and 193.5 volts. Time from 238.2 to 193.5 is 18.5 hours, from 193.5 to 180.9 is 5.25 hrs.

I cited the 180.9 dip because it was the lowest and longest (duration) that the recorder has picked up. the 238.2 dip lasted 0.076 seconds and the 193.5 for 0.116 seconds.

Thanks!

 

[dpm457]

Was this only one event or recurring? If recurring, how often?

There have been a total of 3 events on A phase during the 4 days of metering.
#1- a dip of 238.2 volts lasting 0.076 seconds
#2- a dip of 193.5 volts lasting 0.116 seconds
#3- a dip of 180.9 volts lasting 0.327 seconds

Time lapse between #1-#2 = 18 hours
Time lapse between #2-#3 = 4.75 hours

 

[ptonsparky]

Are you having problems with the mentioned items?
I am curious but am not the one that can answer your questions.

 

[dpm457]

Yes, but I cannot direclty relate the issues with the data available. I plan having the recorder going for a few months and having POCO investigate potenial problems on their end.

 

[gar]

130628-2420 EDT

dpm457:

Are or can you simultaneously measure current on the three phases along with the voltage recordings.

What is the nature and shape of the voltage dips? What is a comparison of short time voltage fluctuations around the time of the dips? Does the voltage on the bad phase show more fluctuation than the good phases?

How close to the power company owned feeder lines are your voltage tap points? What side of any terminal block or possible point of an intermittent high impedance are the voltage tap points?

.

 

[sparkyrick]

Had a similar case at a local c-store/gas station. One leg of the 120/208V service kept dipping. Poco said their equipment was working fine and it was a problem with the Main in the service. Um, OK. I investigate and take readings, of course, nothing happens while I'm there. The one leg finally drops out completely and the service single phases, knocking out all the three phase equipment. Poco comes back and re-inspects the transformers and finds one bad connection on the HV side that they "missed". Ooops.

 

[iwire]

I have a Fluke logging meter set-up in a 4000 amp 277/480v service. One event showed A phase voltage dip to 180.9 volts for 0.327 seconds. Is this dip long enough and low enough to create problems for PC's, UPS, and other electronics? A phase is consistenly running between 267-271 volts, B & C phase 273-276. Amp loads are balanced +- 10%.

When A dips do B or C rise?

 

[mayanees]

fluke software

fluke software

I think the definitive answer as to whether or not the measured V dip is unacceptable is to look for ITIC (Information Technology Industry Council) violations. That's the standard that replaced the CBEMA (Computer & Business Equipment Manufacturers Association) curve as the waveshape criteria for uninterrupted operation of utilization devices. The Fluke software will identify any violations.

 

[dpm457]

130628-2420 EDT

dpm457:

Are or can you simultaneously measure current on the three phases along with the voltage recordings.

What is the nature and shape of the voltage dips? What is a comparison of short time voltage fluctuations around the time of the dips? Does the voltage on the bad phase show more fluctuation than the good phases?

How close to the power company owned feeder lines are your voltage tap points? What side of any terminal block or possible point of an intermittent high impedance are the voltage tap points?

.

Yes, I'm simultaneously measuring current on all 3 phases. Have not seen relation to amp draw and voltage dips, yet.
I will post info about the shapes and voltage fluctuations tomorrow once I download from the SD card
The POCO xfrmr is 125' or less to the conductor tap points in the main gear. 7 sets of 350kcmil serve the facility

 

[kwired]

If there would be other services supplied by same transformer the problem may be triggered by loads at the other services.

Even if yours is only service on your transformer, same could apply to other loads on the primary lines. Resistance in a connection could be starving you of voltage on a particular phase when a neighboring customer starts a particular load.

 

[ptonsparky]

With 7 sets of 350 I have a hard time thinking it is 'a' bad connection unless it be at a buss splice that was never torqued, which at your loads should have become apparent. Thermal scan?

Are you sure a mouse isn't farting on the meter lead connections?

 

[GoldDigger]

Is this dip long enough and low enough to create problems for PC's, UPS, and other electronics?

Some remote possibilities:
Electronics with really poorly designed power supplies connected only to that phase may malfunction.
UPS with very tight line tolerance may trip, but that should not upset anything on the load side.
Phase loss detectors for motors or other equipment might trip if set on the hairy edge of sensitivity.

I would be more concerned about what was causing it and what might happen if it gets worse than with the direct effects of that dip.

 

[ATSman]

Some remote possibilities:
Electronics with really poorly designed power supplies connected only to that phase may malfunction.
UPS with very tight line tolerance may trip, but that should not upset anything on the load side.
Phase loss detectors for motors or other equipment might trip if set on the hairy edge of sensitivity.

I would be more concerned about what was causing it and what might happen if it gets worse than with the direct effects of that dip.

I am puzzled by your last sentence. Wouldn't the direct effects or "symptoms" lead one to the root cause of the anomaly? :?

 

[GoldDigger]

I am puzzled by your last sentence. Wouldn't the direct effects or "symptoms" lead one to the root cause of the anomaly? :?

Yes. I was just trying to emphasize that even if the observed dip was not causing any effects on utilization equipment (and the OP did not indicate whether there were any), finding the cause would still be important.

Any other observations that accompany the recorded dip could be considered symptoms to help track down the source. But not at this point hypothetical "effects" which would force the problem to be attacked in the first place.

 

[ATSman]

Yes. I was just trying to emphasize that even if the observed dip was not causing any effects on utilization equipment (and the OP did not indicate whether there were any), finding the cause would still be important.

Any other observations that accompany the recorded dip could be considered symptoms to help track down the source. But not at this point hypothetical "effects" which would force the problem to be attacked in the first place.

If you check post #6, DPM does state that it is causing problems with the mentioned loads. Maybe if he gives us more info from the diagnostic history at these loads (UPS, VFD's, etc) we could help him find the cause.

 

[gar]

130702-1552 EDT

Since current is also monitored with voltage and there does not appear to be a current correlation with the voltage dip this means the cause of the dip is not due to his load current and the problem is closer to the source than where the voltage is measured. See post 5:25 PM yesterday.

.

 

[ATSman]

130702-1552 EDT

Since current is also monitored with voltage and there does not appear to be a current correlation with the voltage dip this means the cause of the dip is not due to his load current and the problem is closer to the source than where the voltage is measured. See post 5:25 PM yesterday.

.

That is a valid point and I think you mean post #11 @ 2:25PM.
We had a situation once where this data center had an old Dranetz 845 monitoring both 4000A, 480V mains on a double ended substation. There was a line disturbance showing up on phase A of the voltage waveform at exactly 06:05Hrs every morning. It showed as a glitch (transient) on one cycle of the sine wave but was not load affecting since the duration was so fast it did not change the RMS level for that phase.
The POCO was contacted and a month later the glitch disappeared. We were told that it was caused by a faulty contact
on one of their switches of their power factor correction capacitor bank (12KV) that would switch in at 06:05HRS daily. After the repairs were made they thanked us for bringing to their attention