Utility power meter "stuck" at 0.707 power factor
Utility power meter "stuck" at 0.707 power factor
(OP)
I'm looking at a power factor correction case and the utility meter almost never reads above 0.707. There are a few measurements higher but most are either 0.707 or they are lower. The loads are all inductive yet the addition of power factor capacitors has caused the kVAR to appear higher and the power factor to appear lower compared to the metering data from before the capacitor bank addition.
The meter readings are from the meter's 15 minute fixed window demand calculations where it will give kVA, kVAR, kW and power factor for each 15 minute period. Is there anything odd the meter might be doing while calculating these demand values?
When using a power logger on site with the equipment running, the average power factor never goes below 0.9 lagging. The power factor curve recorded every second is actually quite flat varying between about 0.92 and 0.94 during the 1/2 hour I was monitoring.
Yet, utility meter data from other days with the equipment running always show a poor power factor never above 0.7 (it's not clear if this is leading or lagging).
Does anyone else believe the meter must simply be connected wrong?
If it's not a connection issue, then what could be the problem?
The meter readings are from the meter's 15 minute fixed window demand calculations where it will give kVA, kVAR, kW and power factor for each 15 minute period. Is there anything odd the meter might be doing while calculating these demand values?
When using a power logger on site with the equipment running, the average power factor never goes below 0.9 lagging. The power factor curve recorded every second is actually quite flat varying between about 0.92 and 0.94 during the 1/2 hour I was monitoring.
Yet, utility meter data from other days with the equipment running always show a poor power factor never above 0.7 (it's not clear if this is leading or lagging).
Does anyone else believe the meter must simply be connected wrong?
If it's not a connection issue, then what could be the problem?






RE: Utility power meter "stuck" at 0.707 power factor
Can you narrow down to whether the error applies to kw or kva (seems like you have enough data for that comparison)
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RE: Utility power meter "stuck" at 0.707 power factor
I can't directly compare the logging and the utility. The utility data was available on-line the next day but it's been off-line for the last few weeks now.
Still, it's just a bunch of motors starting full-voltage running 2 crushers. Any day with the crushers running will be about the same as any other day.
RE: Utility power meter "stuck" at 0.707 power factor
If you just added capacitors without change and measure your PF at the meter location (or close) and got a different measure, they should be the one figuring out what is wrong.
A simple calculation of your loads with typical PF should also give you a good estimate of the PF you should expect (I suppose you did that when sizing the PF correction capacitor)
We may also want to check past bills.
RE: Utility power meter "stuck" at 0.707 power factor
You might have roughly a 20 degree lagging power factor angle corresdponding to pf=0.94 lagging
If you subtract 60 degrees, it looks like -40 degreess power factor angle, which would be 0.76 leading
Or not...
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RE: Utility power meter "stuck" at 0.707 power factor
20 degree angle (0.94 pf) might change to 50 degree angle (0.64 pf). That doesn't quite seem to match as well.
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RE: Utility power meter "stuck" at 0.707 power factor
Had a customer who managed to reduced his utility bill by properly sequencing starting up his motors in the morning.
Also remember that what you see on the utility web site might have been "processed" for billing purposes.
RE: Utility power meter "stuck" at 0.707 power factor
Rafiq Bulsara
http://www.srengineersct.com
RE: Utility power meter "stuck" at 0.707 power factor
Rafiq Bulsara
http://www.srengineersct.com
RE: Utility power meter "stuck" at 0.707 power factor
If so, the meter will read the load MVAR + the tranformer MVAR losses.
RE: Utility power meter "stuck" at 0.707 power factor
RE: Utility power meter "stuck" at 0.707 power factor
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RE: Utility power meter "stuck" at 0.707 power factor
rcwilson - true enough, there are 2 transformers metered on the high side. However, correcting the power factor on the low side should make the high side readings much better, not slightly worse.
jghrist - Yup, the meter seems to have more 0.707 power factor readings than it should, I'm just not sure why the meter would measure kW and KVAR as equal so much of the time. OK, it was doing that a lot before the caps were installed but now the power factor never gets that high.
I'm not getting paid to deal with the utility but I'm still interesting in ideas on what could be causing the problem.
RE: Utility power meter "stuck" at 0.707 power factor
Are they old electromechanical meters?
Back in the day, KVARHrs were measured with a standard KWHr meter with the addition of small phase shifting transformers.
The transformers shifted the phase of the voltage 90 degrees and made the meter respond to quadrature current rather than real current. They were a challenge to connect and the possibility of connection errors was quite high.
Bill
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"Why not the best?"
Jimmy Carter
RE: Utility power meter "stuck" at 0.707 power factor
This peak was defined as actual kW or 90% of kVA, whichever is greater.
So you could be seeing a 'ratcheted' peak amount on your bill, rather than actual.
If you think about it, this system makes some sense, since the utility has to build enough infrastructure, from the transmission right down to the cusotmer service wires, to handle the PEAK requirements of each customer.
As others have said, ask your utility. Its free, and they usually have answers.
RE: Utility power meter "stuck" at 0.707 power factor
Second: the harmonics some time could worse the pf mainly if you try to improve it by means of capacitors. The total or "true" PF accounts for the phase displacement as well as harmonic power. See:
http:
Or:
http://
"There is, however, a growing PF problem that cannot be fixed by adding capacitors to a circuit: switched mode power supplies which are found in personal computers and other electronic devices use rectifiers and switching transistors to regulate voltage.
These nonlinear components produce harmonics that can feed back into the circuit and, if there are a significant number of these devices, overall PF can be reduced. This is becoming a significant concern for utilities because capacitors alone will not fix the problem."
See:
htt