PM8000 display of other voltage when wired single phase

[Yarom]

Hello,

I have a PM8240 in which I wanted to demo for one of our sales guys.  They wanted to see how the measurents can be read.

I connected a unit I have with 230VAC control supply. I took V1 and VN from the same supply to show a Voltage reading on the meter's display, Webpage and ION Setup.

I set the Volts Mode to Single.

PT Pri = Sec

CT left as is - no current being injected.

For some reason, I get a reading on Vb, a little more than half of V1.  See the images.

VLL (Vll ab (V)) = 115.10

Vln a (V) = 233.90 [the right reading]

VIn b (V) = 132.47 [Where does this come from?]

V L-N Average = 183.19 [average of a and b]

I wanted to see if this is normal so connected PM5350P and PM2200 that I have as well.  Both have Power System option 1PH2W LN, which is the way wired them, identical to PM8240.  Both of the low end PM's showed only the 230V measurement.

What am I missing? I am trying to find the details about what SINGLE (Volts Mode) means in the manual. Is there some internal capacitor that is causing the reading? If so, why would the unit not be programmed such that it should disregard that value and display only V1 N?

If I may, I have a secondary question - what is the difference between U and V? I am seeing some answers online but none are concrete.

Thank you.

Yarom

[Mehran_Mehrnia · Accepted solution]

Hi @Yarom 

There is one phenomenon called Phantom Voltage which is also called as Ghost voltage.

Here is an article that clarifies the Phantom Voltage Phenomenon(Voltage readings on unconnected voltage input), which can be observed in meters without ground connections like the PM8000 and PM5000.

The Phantom Voltage phenomenon is a normal artifact of the design and is known as Phantom Voltage. This means that in some installations, protective class II PMDs (Power Monitoring Devices) without earth (ground) connections may exhibit 'phantom voltage' readings on unconnected voltage inputs.

Phantom Voltage can be seen on PM8000 and PM5500 series meters that do not have Earth terminal.

In the following FAQ, you will find additional detailed information regarding phantom voltages. The FAQ includes the Schneider Electric Technical Reference Phantom Voltage White Paper 7EN52-0331-01, entitled 'Phantom Voltage Readings on Power Monitoring Devices (PMDs).’

https://www.se.com/eg/en/faqs/FAQ000133551/

In PM5500, we can minimize the displayed phantom voltage by adding the ground module into the meter. 

Please refer to the Ground Module Installation Guide for more details. The commercial reference for the ground module is "METSEPM55GRMD".

https://www.se.com/ca/en/download/document/NVE30698/

https://www.se.com/ca/en/download/document/METSEPM55GRMD_3D/

Regarding the second question, if you check the Display Option Module in ION Reference -> Display Option Module, -> Setup Registers -> Measurement Symbols, you will see the symbol of phase to phase and phase to neutral in IEEE mode are Vll and Vln however in IEC mode are U and V:

Best Regards,

-Mehran

L3 Expert Advanced metering

[Yarom]

Thank you so much for that! That makes perfect sense. We assumed there must be some capacitance and because it is not grounded, there is nowhere for the V to go.

The question now becomes, if we know about this and that it is an issue with type 2 power meters, how come can we not have it programmed to recognize the false reading and cancel it out?

Or, for this meter (PM8240), is there somekind of safe and acceptable wiring we can do to avoid the ghost reading?  Otherwise, we have to send a note to each one mentioning this issue and to ignore the reading.

(We found the same issue at a VIP - Datacenter that has over a dozen units and some have this type of reading.)

[Mehran_Mehrnia]

Hi @Yarom 

You're welcome.

As verified by the PM8000 offer manager, Phantom voltages may appear unusual, but the meter displays all measured voltages to prioritize safety. Since it can't distinguish between harmless phantom voltages and potentially dangerous ones, suppressing them could pose risks. It's up to safe electrical practices to verify whether a voltage is truly hazardous.

You can implement a workaround by activating an alarm when abnormal conditions are detected e.g., voltage present when the breaker is open by using digital inputs to read breaker status signals and correlate them with voltage readings.

If eliminating phantom voltage readings is essential, please contact your local Schneider Electric representative for available solutions.

Best Regards,

-Mehran

L3 Expert Advanced metering

[Charles_Murison]

Hello @Yarom 
If I am not mistaken, your wiring is V1 only connected to a voltage source correct?
For PM8000 meter, did you connect V2 to V3 to VN?

If V2 and V3 connected to VN, do you still see a voltage on V2?

Regards,

Charles

[Yarom]

Hi Charles,

I connected V1 to L and VN to N only. I did nothing with V2 and V3.

So I have this:

Are you suggesting I should wire like this:

 (Interesting how in the instruction sheet we only see the options:

And not 1PH2W LN.

BR

Yarom

[Yarom]

Hi Charles,

I took your suggestion and applied my second drawing where I connect to N and jumper V2 and V3 terminal to N.  That seems to solve the issue:

Is this what should have been? Is that what I should have understood from the Instruction Sheet that showed 1PH 2W LL?

Is this what clears the issue as the "Phantom Voltage White Paper" that Mehran provided?

Best regards,

Yarom