Power Quality Analyzer Question

[streets]

Hello, it has been some time since I have posted, but I remember where to ask a question when I get stumped. I work for a small government and install / maintain traffic signals. These run on 120vac generally and the load is approximately 4 amps (LED optics.) In with the mix of microprocessors is a unit called a conflict monitor or Management Malfunction Unit (MMU.) It is setup to detect among other things, incoming voltage drops and spikes hitting 96vac and 150vac. You may have seen this on the road, the traffic signals go into an All Red, or Yellow flashing pattern. The MMU is usually pretty good at identifying the sourse of a problem, but the last incident happened so fast (nano seconds) it could not record it.

Would someone please recommend a good piece of testing equipment that will monitor incoming utility voltage over a period of time? The longer the better. I have heard terms such as: A Megger might do it, a Platform Quality Demand Analyzer, and Power Quality Analyzer and so on.

My personal opinion is that there are very fast Brown Outs occuring. I just need a piece of equipment that will prove or disprove that.

Thank you in advance,
Dave

[catchtwentytwo]

Would someone please recommend a good piece of testing equipment that will monitor incoming utility voltage over a period of time? The longer the better. I have heard terms such as: A Megger might do it, a Platform Quality Demand Analyzer, and Power Quality Analyzer and so on

Are you looking for a temporary troubleshooting tool or permanently installed monitoring? How much do you want to spend? Do you want to physically go to the device to get the data or be able to remotely access it?

The MMU is usually pretty good at identifying the sourse of a problem, but the last incident happened so fast (nano seconds) it could not record it.

It sounds like you might be looking for transients as opposed to long-term trending of voltage. Before you look for a product, you need to know what you want to observe. There are a lot of good Power Quality articles available at the Fluke web site including one on Electrical Noise and Transients.
http://us.fluke.com/usen/support/appnotes/default?category=AP_PQ(FlukeProducts)&parent=APP_N OTES(FlukeProducts)

[charlie tuna]

the metrosonics units measure every aspect of the power 32 times per cycle.
you can just keep digging into the data and expanding it over and over. but they are expensive. why not just purchase a small ups unit and install it in front of your four amp load ----------- see if this corrects the problem--if so -- your incoming power quality is the culpert!!

[msb10]

Charlie Tuna,

I've seen you recommend the Metrosonics unit several times. I can't find any information on it. I found a reference that associated them (metrosonics) with Megger. Is this right? Is the unit you are familiar with the Megger PA9Plus, or similar to it?

Thanks,

Matt

[charlie tuna]

msb,
yes, meggar bought out metrosonics ---- and they are the representatives now. they do the certification and repairs also. i have two units and associated ct's from 5 amps thru 4000 amps. i have had them since 1990 and am satisfied with the investment return in rentals and jobs they have made. from time to time i have had to rent additional meters and found them usually very user un-freindly! i remember picking up my first data logger and needing it on site the following day. i also needed a hair cut! i took the tech manual and read enough during my haircut to successfully install and monitor the problem the following day--------and i don't have alot of hair!!! i would charge installation and removal labor, plus $35.00 a day rental and the time it took to download and provide the necessary report. i was hired by other contractors and engineers mainly. in the last few years we provided an increasing number of reports to engineering groups on expansions or add on's! allthough, these meters did harmonics, 95 per cent of the requests were total power calculations.

we have had problems as mentioned above in control panels, like a johnson control panel, and usually the installation of a $110.00 mini ups corrects the problem if it's caused by incoming power.

[msb10]

Thank you for the information. I've rented a couple of similar loggers (RPM and Hioki), and am looking to purchase a unit.

Your comments are very helpful, thanks again.

Matt

[charlie tuna]

msb,
the biggest problem i had with rentals was the rpm units. i was hired to monitor the emergency power usage of a hospital. the required monitor time was ten days. i needed seven data loggers and i rented five units -- three were rpm. at the end of ten days, when we downloaded the information, two of the rpm units were blank!!! all three were set up the same way -- so i called the rental company --- they could not understand what the problem was??? but did wave the rental for the second test period. and offered to walk us through the setup proceedure on the phone which we did. ten days later we had the same problem --- two of the units would not download! at this point i was really pizzed! after they got the meters back, the renter was able to get back into the programs of the two meters and get the information out. they blamed it on the previous renter who had programmed a second monitoring period into the two loggers.... i like the fact that with the metrosonics unit, you know your meter is programmed and recording within a few minutes after it's installation. when you close the cover -- it's done! the hoiki unit i have never used -- but seems user freindly from the adds i see in the trade manuals................. the rpm units are very confusing to me and just as bad to download --- remember, the user friendly issue needs to be in both the setup and download modes ---or software...

[msb10]

The thing that I like about the PA9 over the RPM is the display (well, also the price). With the RPM, you need a laptop to see what is going on with the logging, which I think is awkward. The Hioki looks pretty similar to the PA9.

Thanks again.

[charlie tuna]

also check out the cost of certification and the turn around time -- metrosonics were very good -- when taken over by meggar -- it's customer service is not as good!!! and the cost of ct's is important. the actual print out of the rpm unit is not near as precise as the pa-9...

i forgot to say that whenever i set a data logger, the customer signed off on a liability letter to be responsible for limiting personnel to the metered area and responsible for the meter since most of the time there are open panels or switchboards. we roped everything off and installed danger tape and hung signage of warning -- but you never know??????????? some of the larger buildings changed the lock cylinders to the rooms -- the airport installed hasps and locks to the slab....

the logger's memory determined the length of time it would record and also how much information you asked it to record. we bought the maximum memory package and would normally last about 28 days.

we made it a practice to carry a clamp on ammeter just to check the meter's operation and pre-programming before beginning the recording.

[rick hart]

Going back to the original question and the brown out lasting nano seconds, there comes a point that sampling becomes too fine. The AC voltage already goes to zero 60 times a second so, rule out the short duration voltage sag. You are probably looking at a very sharp voltage transient that is protecting the power supply by shutting itself down.
If this hunch is correct, a good quality TVSS will do the trick. I have had to put TVSS in front of small UPS systems protecting digital control systems that shut down during large ATS transfer- they thought an overvoltage condition was present because of the large switching mpulse