Power Quality Issues
Power Quality Issues
(OP)
Hello,
I am trying to understand how harmonics from a few new oil wells with large variable speed motors can cause a few residential washers to stop working. They worked fine until a new substation with a delta wye transformer was recently energized. This substation serves the oil wells as well as the problematic residential loads. After some tests and monitoring we believe it is the third harmonic caused by the variable speed motors causing the washers to not work. They work fine when ran from a generator. I am trying to understand how this happens? Also, any recommendations on how to fix the problems would be appreciated. I have found a few power quality filters that may work.
Thanks for any help
I am trying to understand how harmonics from a few new oil wells with large variable speed motors can cause a few residential washers to stop working. They worked fine until a new substation with a delta wye transformer was recently energized. This substation serves the oil wells as well as the problematic residential loads. After some tests and monitoring we believe it is the third harmonic caused by the variable speed motors causing the washers to not work. They work fine when ran from a generator. I am trying to understand how this happens? Also, any recommendations on how to fix the problems would be appreciated. I have found a few power quality filters that may work.
Thanks for any help






RE: Power Quality Issues
Are you working for the home owners, the utility or the oil companies?
The first step is to check the voltage. If this is a simple case of low voltage, then filters may be a waste of time and money.
An oscilloscope check for harmonic content may be a good idea.
If the voltage is good, than shut off the oil well pumps.
It is not permitted in most jurisdictions to cause distortion power factor which will interfere with other users of utility power.
The pumps may be run on generators to maintain production. While on generators, the power quality issues may be investigated, identified and resolved before the pumps are reconnected to the grid.
In many jurisdictions correcting poor quality power to a residential customer is the responsibility of the local utility.
Under many tariffs, if a utility determines that a user is causing high levels of distortion that are affecting other users, then the utility has the right and responsibility to force the problem user to correct the issue at their expense. In extreme cases, the utility may disconnect the problem user.
But, to repeat, check the voltage first. That is a utility issue.
A call to the Utilities regulator may prove productive.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Power Quality Issues
while the washer was under load, it was checked with a Fluke 87 meter to check for min/max voltage deflection, there was less than 1/2 volt. Also, no stray voltage found. Hz is steady at 60 Hz, but other tests/oscope checks ran to show that the 3rd harmonic presence is very high.
RE: Power Quality Issues
Does your utility have standards for maximum allowable distortion at the Point Of Common Coupling? (The connection point of the well pumps)
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Power Quality Issues
The solution is likely a filter, either a tuned harmonic trap or an active filter. The latter is likely to get expensive as the power level rises, and the reliability is lower than a passive solution, but it will adapt well to changing conditions and a varying harmonic profile. The passive filter will be optimised for a specific set of conditions and be less effective as the operating state moves away from that optimised condition. I'd assume that the oil company would pay for mitigation measures in preference to being disconnected from the supply.
RE: Power Quality Issues
Keith Cress
kcress - http://www.flaminsystems.com
RE: Power Quality Issues
RE: Power Quality Issues
What are their sizes, kW or HP?
What exactly are the motors being driven/controlled by? Makes/models would be very useful in getting to the details.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Power Quality Issues
IEEE Std. 519 gives limits on a customer's harmonic current levels. I suggest measuring the harmonic current distortion at the oil well service points. If the distortion exceeds IEEE Std. 519 limits, then you may have a case for requiring the oil well owner to install mitigation of some sort.
RE: Power Quality Issues
it's far more likely that if there are light fixtures or other single phase power supplied electronics in those pump stations, that those are the source of your 3rd order harmonics. It's also possible that the issue causing your appliances to not function is related to common mode noise, not harmonics. If not installed properly, common mode noise inherent in the operation of a VFD can cause all nature of problems with other sensitive electronic systems. Likewise with EMI/RFI issues, also due to a lack of attention to installation details. I would spend more investigation time on those areas rather than harmonics.
"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington
RE: Power Quality Issues
I am trying to understand how harmonics from a few new oil wells with large variable speed motors can cause a few residential washers to stop working. They worked fine until a new substation with a delta wye transformer was recently energized. This substation serves the oil wells as well as the problematic residential loads.
Unless you didn't write this clearly, it appears you are saying the "new" oil wells worked fine and did not cause residential issues - until AFTER installation of a new transformer... Wouldn't that mean the issue is the new transformer and not the oil wells?
Perhaps a simple solution would be to move the residential loads off THIS transformer?
You have been asked to share scope pictures, but it seems you only have max/min digital voltmeter readings? How do you KNOW it is 3rd harmonic noise causing the issues if you have not scoped the voltage yet?
You have been asked for the motor sizes, voltages, vfd model numbers... Lots of folks here know lots of different brands and designs - no telling WHAT will pop up if you share? It is being ASSUMED your VFDs are simple diode front ends - better answers can be given if you share what you actually have? We once had a certain type transformer added to a machine tool installed in a corporate 3 story building and when it turned on all the clocks in the building ran backwards - active front end on the large vfd on the machine... share more?
www.KilroyWasHere<dot>com
RE: Power Quality Issues
As one example of something that should be fixed instead of masked-over with some filter. Many VFDs use 3 diodes and 3 SCRs in the rectifier. The SCRs are first off so the initial turn-on power goes through 3 small diodes and a resistor to charge the bus, using the 3 main rectifier diodes to complete the circuit. Then, once the bus is charged the 3 main SCRs in the rectifier are gated-on to make the full 3-phase rectifier. However, if the gating circuit on one SCR fails then the rectifier has one phase running 1/2 wave rectified.
RE: Power Quality Issues
RE: Power Quality Issues
What is the distribution voltage?
Is the transformer wye well grounded?
Are the distribution transformers line to neutral or line to line?
How far from the sub to the washers?
How far from the sub to the well pumps?
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Power Quality Issues
RE: Power Quality Issues
So in reality, it is as originally stated: both oil pumps with VFDs AND residential dc brushless zero cross detect motor controllers in new washing machines (another assumption) worked fine together UNTIL the transformer was added to the picture.
So it begs for info: WHAT was the exact (details please?) distribution scheme BEFORE the new transformer was added?
www.KilroyWasHere<dot>com