PM5110 - Phase loss practice - question

[sesa213753]

Hi,

Here we have a case:

Some students bought 2 meters to do Transformer practices (in a University). So they are doing examples of phase loss, but what happens is when they quit one phase, the meter doesn't show 0v, instead shows 40v (approx), that happens with all combinations.

They are waiting to have

V1     120

V2      0

V3     120

and what they have

V1     123

V2     40

V3     123

They are using 3ph4w

Do we have an answer for this behavior ?

best regards

[ganesh_azzo_com]

Hi Jorge, Yes i have seen this behavior. When you use 2 phase wiring, it's no more 3ph4w, it should be programmed in delta. Hope this helps the students.

[sesa77557]

Hi People, is this correct?

I mean, in a real case installation (not a demo for University), if we lose one phase Customer is expecting to see V2 =0 V and not 40 V without changing the cabling setting... Am I right?

Have a nice day!

Roberto

[sesa213753]

Hi, we need an official answer that WHY this happens, they are doing a final work for the University and they have to answer with a letter of our side.

[sesa44646]

Jorge, if you want an official answer you need to submit a technical support case. The Solutions Expert Community is intended for peer-support and communication between Schneider field personnel, Schneider registered Partners and our marketing and engineering staff. You may get an answer here, but we can't guarantee it will happen in the time you need, or be 'official'. Often people do get the answers they need, but a technical support case is the only guarantee.

[Daniel_Brandao · Accepted solution]

Hi Jorge,

In some situations, voltage readings may be present on the power monitor high impedance voltage inputs without any electrical connection to a voltage source. These harmless “phantom” (also known as “ghost” or “stray”) voltage readings are usually caused by the capacitive coupling of voltages through the auxiliary (control) power supply of a PMD, and are exposed on the high input impedance of the measuring instrument. This phenomenon is usually observed on ungrounded PMDs (i.e. on “protective class II” devices without functional ground (earth) connections).

The phantom voltage is a physical phenomenon involving voltage coupling through very small values of capacitance, and therefore it cannot supply enough current to energize a load or cause harmful physiological effects to a person coming in contact with such phantom voltage.

This is a known situation and it happens with all "protective class II" devices without functional ground, including our competitor's meters. This is the safest way to design power meters, but the downside is the presence of these phantom voltages. Fluke does have a product that can take the effect of phantom voltages out of the equation and has released a white paper on the topic: http://www.testequipmentdepot.com/application-notes/pdf/multimeter/fluke-117-drives-the-ghosts-out-o...

I am working on a white paper to better explain the issue and I will also release a kB article to tech support soon. Please contact me by email if you need more information.

Daniel

[sesa213753]

Thank you

[sesa213753]

Hi you´re right.