Metering equipment for capturing sub cycle transients 3

[rockman7892]

I had posted a little while ago that we are experiencing several issues in our facility that we believe are a result of voltage transiens originating either from outside our facility or coming from within our facility.

In an effort to analyze some of these transients I want to try to capture them on some sort of power metering device. I believe some or most of these transients are sub cycle transients lasting less than 1/2 cycle in duration in which case most relays or metering equipment are not quick enough to capture these transients.

Does anyone know of a good power meter for capturing these sub-cycle transients? I would want something that could provide an osilography of the transient as well a indicate magnitude and durations. I would want something that I could permenantly install and put on our SCADA network for viewing present and past events.

Does anyone have any experience with a particular unit?

Does anyone know if the Multilin 750 relay, or Multilin PQMII Power monitor is capable of this?

 

[racobb]

Have you tried Satec, ElectroIndustries, or Bitronics for permanent installations?

Metrosonics or Power Monitors for portable units?

Alan

 

[rbulsara]

There are many, RPM 1750 for example. Look up Astromed also.
You may want to call up Dranetz/RPM or Fluke or the like.
Also try speaking to some electrical testing company folks in your area.

Rafiq Bulsara

http://www.srengineersct.com

 

[dpc]

The PQM meter has this capability. For permanent installation there are a lot of options. The Schneider/Square D ION meters (formerly PML) have a very wide range of power quality monitoring capability - and a bit of steep learning curve.

There are numerous other options, including Schweitzer, Electro Industries, and others.



David Castor

http://www.cvoes.com

 

[QBplanner]

Even you get meters installed. How will you tell between "outside our facility or coming from within our facility" without knowing the information of the scheduled or forced outages from both facilities.

 

[rbulsara]

The catch is that most power metes captures require software to view them in full detail, such as those part of a power monitoring systems. The "free' versions may not get you the details you want. Check with the vendors on that or ask for a demo.

Rafiq Bulsara

http://www.srengineersct.com

 

[davidbeach]

With knowledge of both currents and voltages at a point, it is fairly easy to determine whether or not a disturbance originates on the source or load side of that point. It's still not trivial, but no longer essentially impossible as it would be if only voltage is known.

 

[rockman7892]

Thanks guys.

I looked a little deeper at the PQMII and it appears it is possible to see these subcycle transients with the relays "Trace Memory" setup.

I'm going to try to set this up next week to see if I can catch some of these transients, and I will post my findings.

I'm going to look into someo of the other devices mentioned above.

 

[QBplanner]

"it is fairly easy to determine whether or not a disturbance originates on the source or load side of that point."
It also depends on the type of the loads. Some indu. facilities in the system I work have there own Co-gen and big motors adjacent with the others.
To me the most interesting job in power system is to do a post-disturbance analysis. It is not a easy job.

 

[rockman7892]

I was able to capture a transient yesterday with my PQMII, meter and have attached the waveform. I have some issues I need to resove with the display of the of the data (missing Vc phase, and not Vb reading) but I think the waveforms that are captured might give enough of a sample.

This meter is set up on one of our 4.16kV feeders, and I set the trigger on the meter to trigger at 110% of nominal voltage. This trigger occured at 5:31 EST yesterday evening, and at this time there were no other large loads starting or stopping.

Does anything obvious come to anyones mind when looking at these waveforms? Could this possibly be capacitor switching from outside the facility? Can you tell as davidbeach said weather or not the transients originates within the facility or is coming from outside?

 

[rockman7892]

Sorry forgot attachment

 

[davidbeach]

Where in the system was this taken?

If Ia and Va are the same phase (I doubt it) then you have about 0 for your power factor, but an inductor can't have the currents you show.

 

[rbulsara]

Looks more like a source transfer, using a static switch for example.

Rafiq Bulsara

http://www.srengineersct.com

 

[davidbeach]

If those were voltage channels at the top, and there were no current channels, I'd be inclined to agree. But the only load that could go through that type of change without much larger current transient would be a purely resistive load and that would have a much different power factor.

 

[rockman7892]

Thanks for the responses guys.

The meter that I am looking at is located on a feeder breaker on our main 5kV switchgear lineup after the utility transformer. The secondary of the utility transformer is a 4.16kV wye config, feeding a main breaker on this switchgear lineup. On this lineup there are about (8) feeder breakers. I only did a quick setup on the one feeder breaker attached for the I knew the area it served was having problems. I went ahead and set up the PQM's on the main breaker and the rest of the feeder breakers as well to look for this transient.

All of the PQM's are conntect to the same PT which has an open detla secondary, and all of the PQM's have their own CT's for the respective feeder circuit.

davidbeach, why are saying that it looks like we have a power factor of 0? Is it because the phase shift between the Ia and Va waveforms are about 30deg, and since Va is actually the Vab vector then the actual Va vector will be shifted 30deg which will put it in phase with the Ia current as shown? The p.f. for the downstream circuit is about .86 or so and when I glanced at the phasors everthing looked ok. I'll have to look again. I'm curious why the show the voltage a Va as opposed to the actual Vab?

I guess even with the phasors possibly wrong it there is no doubt a transient that is occuring do you guys agree?

Rbulsara what makes you think this is a source transfer? Is this a typical characteristic? I'd be interested to hear davidbeach's reasoning as well as to why he would expect larger currents or think this would have to be a resistive load? Wouldn't a p.f. of 0 indicate a resistive load?

I will continue to monitor and post results.

 

[rbulsara]

rockman:

Because it is very similar to captures I have seen for STS transfers on resistive loads. At voltage waves are just slightly off by a few degrees, on either side of the "transient". A disturbance in the same source, will not have that phase angle difference. Again, I am not drawing conclusions, just pointing out similarity. Knowledge of the actual system is needed to make definitive comments.

Rafiq Bulsara

http://www.srengineersct.com

 

[rockman7892]

rbulsara

I looked closely and I see what you are saying about the voltage waves being a few degrees off. It appears that after the event, the voltage wave was shifted forward in time.

So are you suspecting that this was some sort of transfer that transfered to a second source that was slightly leading the origional one at the time of transfer?

How can you tell from these waveforms weather or not the transient originated outside of the plant?

 

[jghrist]

You can't really tell from the waveform where the transient originated. If it is a transfer related transient like it looks, then it is unlikely to be on the utility system. Transfer of sources is a rare event on the utility distribution system.

 

[rockman7892]

We only have one transfer source in our system which is downstream of this switchgear lineup. I know for a fact that this transfer switch did not operate at this time for it only operates in an emergency case.

 

[rbulsara]

Anther telling sign of a source transfer is the fact that all three line current waves show the "distortion". I would think if you had captured all three line voltages, they all would have shown a similar break. Most unintentional transients would be only on one or two of the phases, not all three at the same time of the same type/magnitude.

You need to dig further upstream of the system.

Rafiq Bulsara

http://www.srengineersct.com