Voltage data logger

Guys

Does anyone know of a reasonably priced voltage monitor with logging capability?

I am still having freakin' gremlins in my 3ph delta service, and would very much like to somehow identify what might be going on.

Looking to log - something like 1 minute intevals - 4 voltage readings from my service. L1-G, L2-G, L3-G and L1-L2.

Don't need any special precision, a simple 3 digit and no decimals would be plenty enough. Wifi or USB to a dedicated laptop perhaps.
10 years ago I probably would've just build the thing, nowadays ain't got the time or the inclination to do so, but don't want to spend upwards of $3K for a Fluke either.

Thank You

The device is called a power analyzer. There are many brands available, but all are expensive. Unless you deal with these issues very often, purchasing one is not practical. However, these can be leased as well, but you will have to do some searching to find a leasing company near you. Google is your friend.

Some time ago I found a data logger on ebay, wasn't the latest version but did work for what I needed and it was cheap!
Looking at your line monitoring list L1-G, L2-G, L3-G and L1-L2. I assume since you looking at L1-L2, L3 is corner grounded Delta system so why monitor L3-G?
Looking up I seen your in Germany, how is ground referenced in you country?

SeymourDumore said:

Guys

Does anyone know of a reasonably priced voltage monitor with logging capability?

I am still having freakin' gremlins in my 3ph delta service, and would very much like to somehow identify what might be going on.

Looking to log - something like 1 minute intevals - 4 voltage readings from my service. L1-G, L2-G, L3-G and L1-L2.

Don't need any special precision, a simple 3 digit and no decimals would be plenty enough. Wifi or USB to a dedicated laptop perhaps.
10 years ago I probably would've just build the thing, nowadays ain't got the time or the inclination to do so, but don't want to spend upwards of $3K for a Fluke either.

Thank You

Click to expand...

The power Co provided one when I was having voltage trouble.

My personal observation in their use is that they are only useful in determining whether a intermittent fault was due to a power line disturbance or not. For actual sourcing the cause of a power line disturbance, they are pretty useless. I have used Dranetz analyzers extensively in my previous life.

There's a gizmo called a Mooshimeter that sounds odd, but is a serious device. It is stand alone and communicates to a smart phone via BLE. It can measure volts , amps(10 max without a shunt) and ohms. It can read voltage and current simultaneously for power factor and the like. It is 600V Cat III rated, and runs off of 2 AA batteries. The data is recorded to an SD card, and can be viewed on a phone screen real time. The data on the SD card can be downloaded for later analysis. The DAC is 24 bit. Time between readings range from as fast as possible(not sure what that is),1 second, 10 seconds, 1 minute and 10 minutes. A really nice feature is that it can be connected with the equipment off and the enclosure can be closed for safety. It's $125 for one, so for 3 phase it would get fairly expensive.

I've used it for furnace analysis, solar power system analysis, and automotive charging circuit troubleshooting.

There's info at Mooshim Engineering

If you decide it might be useful, I have a skeleton of an excel spreadsheet that will allow offline plotting. PM me if you want a copy.

Used older Dranetz power analyzers are a good deal on Ebay. You just have to get one with the right modules. They are not hard to operate, and are configurable to your measurement criteria.

What are you trying to determine? I have found issues using a Fluke 87 min/max feature. I used to rent the Dranetz power analyzers but even renting they were expensive. But that was over 10 years ago and cheap power analyzers were not really available then. You have many more choices now.

My problem is ground gremlins ( can't describe it any better )
I have a 3ph 240V delta supply, transformer is less than 10' from the building.
Don't have a corner grounded system, rather the building ground is derived by way of 2 ( or more???) ground rods outside the building and brought in via direct bury braided copper conductors.

Last fall I've started having some issues, where a ground short in one of the CNC machine's DC bus propagated throughout the shop and blew out the O/V varistors in two other machines.
Not even on the same panel, let alone common wiring!
Now, all of a sudden my compressor ( Kaeser ) with a "brain" started to complain about random "head back pressure" errors, and the explanation by the Kaeser manual is that the phasing is incorrect.
That can't be? It runs for hours on end without issues and then Bang! Just quits out of the blue.
Then the manual machines ( and I mean Hardinge chuckers and a TOS lathe ) started having random humming while running, exactly like a lost phase would.

So, I started measuring the line voltages: All is well and solid 238-240V between all three.
Ground voltage however makes absolutely no friggin sense!
I know for a fact that when I moved in, I've measured 240-ish between L1 and Ground, and approx 40V from L2-G and L3-G
I also know for a fact that 6 months ago, the very same measurements were ( surprisingly ) almost dead equal between all three lines to ground, about 140V !
Now? It is:
L1-G=239V
L2-G=38V
L3-G=80V

Ground is frozen so cannot start to dig at this time, but absolutely will do in a few weeks and see what condition the ground rods and the braided conductors are in.
In the meantime however ( and might as well for the future ) would like to monitor the lines to see if there is any pattern or reason for the idiotic situation.

Wheels
That mooshimeter looks like a pretty awesome little gadget!
Too bad some of the reviews reek of a manufacturer having some growing pains.
For $125 apiece however, it is absolutely worth taking it for a test drive. If it works, I also don't have any issues spending $500 total for 4 units.

Moonlight
How did you get one from the POCO?
I have a 1200A service and use about $1600/mo worth of it. Might be enough for them to loan one to me for a month or so?

A Delta system has no ground, I have seen applications where in the USA 2 120VAC loads were in series across a 240VAC line from a delta transformer and the common side grounded. It crates what looks like a ground but its not. What is the voltage between L1 and L2?

Sounds to me that you have a bad neutral bond at the service equipment or a bad neutral connection at the utility transformer.

I would guess that you have a center tapped delta service, and the center tap provides your neutral to supply you with 120V for your lights and outlets.

I suggest that you have your utility come out and inspect the neutral connection at the service transformer. Then have a qualified electrician inspect the service equipment connections to insure that the neutral to ground bonding is done correctly and intact.

Your measurements should be done to your neutral bus, not to the ground bus. They should theoretically read the same, but if the bonding is not correct, they will read wildly different, and vary based on what loads are connected at the time.

If you don't have a center tapped delta, then you would need a separate transformer to derive the 120V for your lights and plugs. Most utilities will not provide a ungrounded delta or a corner grounded delta as a standard service.

You would likely be money ahead, to have your connection terminations checked before you spend money on a power data logger. And then still have to check and repair the connections.



SAF Ω

If you really have an intentionally ungrounded delta system, you will have 240V phase to phase, but your phase to ground voltage could be anything between 0 and 240 (and much higher in some cases that I won't to into here). I would have your utility company come check out your transformer to make sure their side is still hooked up properly. Something may have come loose/fallen apart. If it is a true ungrounded delta system, and not an unintentionally ungrounded delta, then...

Draw a triangle on a piece of paper. You can label the vertices (corners) of the triangle A, B, and C. The length of each side is 240, which represents the voltage between A-B, B-C, and C-A. Now put a dot somewhere near the middle of the triangle and label it G. That dot represents ground. As you move that dot around, the distance between it and A, B, and C changes. If you move the G dot closer to A, then the A-G voltage gets smaller, while the B-G and C-G voltage gets larger. That's how the phase to ground voltage on an ungrounded delta system works. Generally, the system capacitance keeps the dot somewhere near the middle of the triangle.

Let's say you have an old tired motor with broken down insulation in your shop. You start that motor for the ba-jillionth time in it's long faithful life, and a bit of insulation falls apart allowing the B phase wire to touch the grounded metal case. You have now moved the B corner of your triangle solidly on top of the G. Now your B-G voltage is zero, while your A-G and C-G voltage is 240.

You now have a grounded delta system instead of an ungrounded delta system. The voltages between phases will remain 240 since the shape of the triangle doesn't change. Only the position of the triangle changes with respect to ground.

Back in the day, ungrounded delta systems were desired because your plant could continue to operate with one phase grounded. These systems usually employ some kind of ground detection scheme to alert you of the situation so you can locate and repair the ground. If you let it go and another phase goes to ground, then you have big problems in the form of a phase to phase fault.

Back when these ungrounded delta systems were all the rage, equipment wasn't all that sensitive to higher phase to ground voltage. As you've seen firsthand, that's not the case with today's equipment. Some VFD manuals specifically tell you not to operate them on an ungrounded system, and I believe I've run across instructions for removing the MOVs from equipment if it's fed from an ungrounded system.

On a grounded wye system, the phase to ground voltage = phase to phase voltage / 1.73. So 480/1.73=277, 208/1.73=120, or in your case, 240/1.73=139V

It's getting late, and I need to go to bed, so I'll wrap this up for now. I don't think digging will solve your problem if the transformer secondary feeding your facility is ungrounded. I would open all of your breakers and measure the incoming L-G voltage. If it seems somewhat balanced,then you can turn one breaker on at a time to see if there's a particular circuit or load throwing things out of whack (or moving your delta (triangle) with respect to the ground reference.

I doubt a power analyzer/recorder will be of much help in your situation. As others have said, you might try your utility company... they'll likely hook one up for you, or at least check their side of the system for problems.

If you do indeed have an ungrounded delta system, I'd recommend installing a grounding transformer with a ground detection system.

SAF responded while I was typing. His advice is good advice.... and also short and sweet.

There are some really smart people on this site.

Guys, not to be disrespectful but ....

Froneck said:

A Delta system has no ground,

Click to expand...

It sure as s..t better have a ground reference!

Sounds to me that you have a bad neutral bond at the service

Click to expand...

Delta has no Neutral!

I would guess that you have a center tapped delta service,

Click to expand...

Huh? How would you center tap a Delta? Where is the center?

(almost sorry I've asked.... )

Huh? How would you center tap a Delta? Where is the center?

Click to expand...

what that means is of the coils has a center tap, and it should be grounded. so phase a and b are 120 volts to "ground" and phase c is 208vac to ground, but there is still 240 between phases.


the disadvantage is that the 120v loads are all on one phase.


anyhow a 3 phase grounding transformer is a zig-zag transformer and they may be hard to find. you can make your own from any three phase 1:1 ratio transformer if you can get access to all the coils to reconnect them correctly, which may not be all that common.


what you are probably supposed to have is a center tapped delta which means the midpoint of two of those phases should be connected to ground as i already described.


the following advice is a hack:

go get a 120v isolation transformer and reconnect the windings in series as an auto transformer, connect it across two phases. connect the midpoint of the transformer to both the ground rods and the neutral of your electrical panel.

if you connect it across the wrong two phases.. when your "ground" or "neutral" wire re-connects you're going to get some sparks somewhere, or you're going to burn up the transformer. but as it is now you don't have a grounded system, so you are taking your chances either way.

SeymourDumore said:

Delta has no Neutral!

Click to expand...

I am trying to learn more about 3 phase power, now I am more confused. The OP appears to be in the USA, so seems pretty sure his plant has 120V outlets. Electrical code requires those outlets have a neutral, and that neutral be bonded to building ground. Assuming this delta 3 phase nas no neutral, and that the three phases "float", so that it is an intentionally ungrounded delta system, either the power user must provide their own 240 to 120 transformer, one side of the 120 becoming the neutral and being bonded to ground, Or subscribe to an additional feed from the power company supplying 220V single phase with 120 V either side of neutral. Is this correct?

RustySparks said:

I am trying to learn more about 3 phase power, now I am more confused. The OP appears to be in the USA, so seems pretty sure his plant has 120V outlets. Electrical code requires those outlets have a neutral, and that neutral be bonded to building ground. Assuming this delta 3 phase nas no neutral, and that the three phases "float", so that it is an intentionally ungrounded delta system, either the power user must provide their own 240 to 120 transformer, one side of the 120 becoming the neutral and being bonded to ground, Or subscribe to an additional feed from the power company supplying 220V single phase with 120 V either side of neutral. Is this correct?

Click to expand...

Lots of locations in the USA have Open Delta service, quite simply 2 single phase transformers connected to 3 phase on the pole and one transformer center tapped, grounded and becomes the Neutral but then one line of the 3 will be much higher above neutral and usually called the Wild Leg and unused for power requiring the use of a neutral connection. A transformer that is Delta wound with a center tapped coil for low voltage use but again it's available only to 2 of the 3 outputs. What the OP has listed is very odd voltages that seem to have been OK at one time.
My son worked for a company that was supplied Delta power, no neutral 3 phase 480VAC. Over the years 240VAC Mercury Vapor lighting was installed in series on the 480VAC lines. The junction was connected in the panel to neutral. Over time that continued and other single phase stuff was added. Naturally the voltage would changed depending on how many of what were connected at one time but as is usual in most companies everything connected is on. But one day one of the Delta lines grounded and that created a situation where all the lights in series connected to the other 2 phases to be now connected to 480VAC and burned up, 1/2 of those in series with the 3rd line went out while the other half burned up. Connections similarly made seriesed to form 120VAC also toasted. Power company was notified and would not change the large Delta Transformer unless it was paid to do so. The company then used transformers to get the voltages needed and rewire what some "Wizzard" did years ago.
I suspect something like that is what the problem is fot the OP.

Froneck said:

Lots of locations in the USA have Open Delta service, quite simply 2 single phase transformers connected to 3 phase on the pole and one transformer center tapped, grounded and becomes the Neutral.

Click to expand...

Thanks good to know. Found a nice video describing this method here:
YouTube

SeymourDumore said:

Guys, not to be disrespectful but ....

It sure as s..t better have a ground reference!

Delta has no Neutral!

Huh? How would you center tap a Delta? Where is the center?

(almost sorry I've asked.... )

Click to expand...

The only way you can have a ground reference on a closed delta, without a center tap, is by grounding one of the corners. Corner grounded delta. But earlier you insisted that that is not what you have.

There are two types of delta configurations that can have a neutral. I provided a drawing with my post of one type, the closed delta with a center tap. That must have whizzed by you.

The second type is similar, an open delta with a center tap. A very common service in older districts, for light commercial 3Φ services. It uses only two transformer pots. The transformer pot for the 1Φ side (the center tap), will normally be much larger than the second one. To carry more 1Φ loads than 3Φ loads, in most installations, but not always. The bank pot sizes depends on the types of connected loads, 1Φ & 3Φ. The pots can be the same size for more 3Φ loads than 1Φ loads.



It seems clear to me that at this point, your unsure what type system you have. Just calling it delta, doesn't differentiate from the 4 types available. Ungrounded, corner grounded, center tapped closed delta, and center tapped open delta. But the readings you mentioned in your posts suggest that you have a center tapped delta, of one of the two varieties.

Another suggestion to prove the point is, that it's likely bad connections or bonding issues, is to measure your voltages at different weather periods. When the ground is water saturated, you will have better conductivity through the earth and hence better voltage readings to ground, and less equipment problems. Worms coming to the surface, to try and escape electrocution, is another symptom. When the earth is frozen or bone dry, the problems will be more prevalent.

I knew that when I replied I would likely get the type of response that I did from you, trying to help. But I mainly did it for other users of the forum. But just put me on ignore, buy some monitoring equipment with Bluetooth, and keep It's all good.

For the other members, I uploaded a video about open delta transformer banks to provide some more insight into their downsides as related to capacity. Utilities liked them, because they saved one transformer pot, but they are not as popular as they once were.

Dropbox - Electrical PE Exam - Open Delta.mp4

SAF Ω