Transcript

Introduction to Voltage Regulation Compliance

Good afternoon, everyone and welcome to today’s whitepaper webinar. Today, we’re gonna talk about voltage regulation and the PQ Canvass Voltage Compliance Regulation report. This is a relatively new edition to PQ Canvass, and it gives you a compliance report for steady state voltage regulation, and it goes by ANSI C84.1, which is what most utilities use for governing voltage regulation.

It’s important to understand how this standard works. It’s a very useful standard for utilities in dealing with customers, because often, a power quality complaint is an under-voltage or over-voltage complaint.

Service Voltage Versus Utilization Voltage

One of the key aspects of C84.1 is the concept of the Range A and Range B voltage ranges, and also, service voltage versus utilization voltage. This is a really important concept for utility customers to understand as well.

This standard makes a distinction between the service voltage that a utility supplies at the point of connection, say at the meter base or the service entrance, and the utilization voltage, which is the voltage at the terminals of a piece of customer equipment, say, at the terminals of a motor. The allowable range of voltage extends lower for utilization voltage. This takes into account voltage drop in the building, in the wiring, in the panels and sub-transformers and so forth.

But when utility customers complain about under-voltage, they’re measuring at the terminals of a piece of equipment. That’s not the service voltage that the utility is in control of, and so, understanding that distinction and being able to explain that clearly to a customer is really key in addressing power quality complaints when the voltage at the meter is actually within C84.1 limits.

Range A and Range B

C84.1 defines two ranges for voltage, Range A and Range B. Range A is meant to be met most of the time. This is generally plus or minus 5% of the nominal. 114 volts to 126 volts on a 120 volt basis, but that scales proportionally to other nominals.

Plus or minus 5% is a core concept, and that’s of steady state average voltage. That doesn’t include voltage sags or brief swells. Generally, that’s measured with a five-minute average or a 10-minute average, because this is a steady state average measurement.

It says that utilities should meet this Range A most of the time. It’s intentionally kind of vague about what most of the time means, at least enough to allow the utility to define that. Most utilities go by 95% of the time in a one-week period or in a one-day period, so that allows for a little bit of exceedance, but most of the time it is there. Most of the time isn’t precisely defined, but a lot of utilities go by 95% of the time in compliance.

Range B is for short-term excursions only. For Range B, the allowance for a little bit higher voltage and lower voltage is wider. Instead of plus or minus 5%, it’s a bit wider than that, and this is meant to be for short-term excursions only. It doesn’t define what a short-term excursion is or how often you can do that, but most utilities go by a 5, 10, 15-minute excursion, and infrequently. This is meant to be like alternate circuit configurations or during non-normal conditions. But that does allow some flexibility for that definition.

Running the Report in PQ Canvass

PQ Canvass will run this report at your request on the data you recorded. If you have PV recording and you’ve always recorded voltage, it’ll take the average voltage traces from that recording and re-average it to a rolling 10-minute or 5-minute average, whatever you define.

I’ll jump over to PQ Canvass to show you this. Here, I’ve got a file loaded in PQ Canvass. This was formerly called Analytics. It’s also marked as Compliance in the very latest versions. Click on this and Voltage Regulation is the one we’re gonna be talking about, the C84.1 Regulation Check.

I’m gonna click on that and configure it, and the defaults are to run it over the entire recording session. You can constrain that to a certain time window if that makes sense for your application. You can change the averaging interval. The 5, 10, 15 minutes are the most common values.

Which channels to use? You should, of course, only do this on channels that have line voltage applied to them. If your Channel 4 is measuring neutral to ground voltage, you wouldn’t wanna run a regulation report on that channel.

The connection point is generally gonna be the meter base or service entrance, and whether you want to use Range A or Range B or both. Default is just to have them both checked and run a compliance report against both, but you can limit those. You can also define your short-term excursion time. We default to 10 minutes here, but if you have a different number you wanna use, you can certainly put that in there.

There’s a little bit of allowance for distributed generation. If there’s on-site DG, that allows for a bit higher voltage at the service entrance. So if you wanna check that, you can do that. Once you have your parameters set up, hit Run, and it will go through the strip chart data and compute the compliance report. This generates a PDF that you can then download and view in any sort of PDF browser.

Reviewing the Compliance Report

The report’s run, you can download this, and here is the analytics report for voltage regulation. It starts with a summary of what was analyzed, the time span, because that’s adjustable, the device that was used, the settings that were used for this report, the averaging interval, the short-term excursions. The Range A and B limits are all here, and then the results.

In this situation, we actually failed Range A. It was out of tolerance for 38% of the time for one phase, 25% of the time for the other. So it was significantly out of tolerance for a large amount of time, certainly more than 5%. It says Range A. Range B, we’re even out of tolerance on Range B for a smaller amount of time, but this failed Range A and Range B. This is an actual voltage regulation problem in this recording.

Then we have some informative graphs. Here is that rolling voltage that’s been computed. This graph is shaded where green is the portion within limits. This is the 126 volts, that’s the boundary for the upper end for Range A. This green section is the portion of the graph that passed. This red is the failure. So you can see that over the course of many days, this is about a 20-day recording, we were into the 130-some range of voltage for a good part of a day. So this is a clear failure.

Here we have the actual excursions themselves in tabular format. You can see it’ll tell you the total time you’re out of the range. In this situation, it was quite an extended amount of time, many different excursions. This can also be exported for a numeric analysis.

Then we get to Range B. Here is Range B. Again, Range B is a bit wider. That gives a little bit more of an allowance, but still over the limit even for the extended Range B. So this is a double fail in this situation.

Daily Profile and Histograms

Ideally, the graph is entirely green, which means that you’re in compliance for the entire time and not just 95% of the time. It also gives you a daily profile if there is a daily pattern to that. Here we can see that the overvoltage was primarily during certain times of the night. This would point towards a volt regulator issue, some sort of timing like that, because it’s a very specific time during the night where this is happening.

This daily profile can give you some insight as to what’s actually happening. Technically, you can sort of see this in the strip chart, but it’s much easier to catch a daily pattern when it’s re-graphed as a daily profile. If there is a day or night motif to it, you’d be easier to see this in the daily profile graph.

There are also histograms to give you some insight into the amount of time outside of the window. And there are some observations that might give you some more insight as to the patterns, here talking about the time when it’s mostly out of range. But the bottom line here is this is a clear regulator failure.

Examining the Strip Chart Data

The customer here has a legitimate complaint. They did indeed see that, and if you look in PQ Canvass, we can look at the strip chart data and see that for ourselves. Here is the RMS voltage strip chart. You can see that for almost an entire day, a 24-hour period, there’s a clear step up in voltage and then a clear step back down. This is some sort of regulator issue almost certainly, where you have these giant steps. So this is a legitimate complaint from a customer. The utility is indeed out of compliance.

We even see a little bit over here, a voltage swell that no doubt was captured with waveforms. Here we can see the voltage going up, though we’re already at a fairly high voltage. We’re at 129.4 and we step up to 138. So we are already running very high, already above ANSI C84 before that, and then a voltage swell on top of that, kind of adding insult to injury there. So clearly, voltage regulation is a problem in this recording, and we have the proof right here.

Typical Results and Customer Communication

Hopefully, in most of your files, you’re going to pass ANSI C84.1. In most cases, if a customer is complaining about under voltage, most likely they’re measuring utilization voltage inside their facility, and you make a recording and can clearly show them, well, at the service entrance, the voltage is within normal limits. You can show them the report that you’re within Range A 100% of the time, and they may have a wiring problem inside the building itself or too much drop inside the building.

In the white paper, we have a different example. This one is not quite as high voltage. We’re only going to about 127, 128 volts. Still a failure, but not quite as severe as the one we just saw. But hopefully, in most of your recordings you’re going to be all green, and it’s a matter of showing the customer that voltage is within range at the meter base, which is where you hand over control to them, and then they have an internal problem inside their facility.

Again, this is a feature inside PQ Canvass itself. If you aren’t using PQ Canvass, feel free to let us know and we’ll get you signed up if you want to try it out.

Q&A: Capacitors and Voltage Regulators

Good question. I’ve heard of caps causing regulators to step all the way up and down rapidly. One of our customers has seen this and the voltage is high enough long enough to trip lift station equipment. That’s a very interesting question. So this would be a cap bank energizing or de-energizing or switching in and out and causing a regulator to rapidly go up and down its step.

I hadn’t heard of that. What I’ve seen more commonly is regulators that can’t handle bi-directional power flow. If you have distributed generation on a circuit, the regulator might get confused if the power is flowing in the opposite direction than it expects and it’ll actually tap in the wrong direction all the way to the extent of its adjustment range, making the voltage worse at every tap. I haven’t seen that with capacitors. I would be happy to take a look at a recording and look at that in more detail.

The key there, I would imagine, would be to make sure that the programming on the controller on that voltage regulator is set up correctly so that it’s not being fooled, especially if there’s a bi-directional mode or a cogen mode. Those can make the regulator tap in the wrong direction.

Closing

That’s all the questions we have now. If you have a question later, give us a call anytime at 1-800-296-4120. Or if you’d like to try out PQ Canvass, give us a call or send us an email at support@powermonitors.com and we’ll get you set up. Thanks for attending everyone, and everyone have a great day.