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Dear All,

I’m working on ADE7880 based 3phase 4wire static electricity meter. Meter configuration 240V, 100A Ct ratio = 2500. How to detect missing neutral tampering situation in PSM0 mode. Please give me details

Regard

Rajamani

• Hi Rajamani,

To detect a missing Neutral situation you will need to monitor the voltage, if the RMS voltage goes lower then it should for the line (for example less than 10% of Vnom) and there is still RMS current being measured then this would be a missing neutral situation. On the ADE7880 you can set a voltage sag threshold. Just make sure the ADE7880 does not lose power so that the RMS can be monitored.

Regards,

Dlath

• Dear Dlath,

I checked But not working.It is very urgent one. voltage sag used under and over voltage temper

Normal Input (with neutral wire):

R phase = 240.01v and 5A

Y  phase = 240.03v and 5A

B  phase = 240.01v and 5A

Without Neutral wire:

DE value

R phase  = 250.9v and 5A

Y  phase = 238.02v and 5A

B  phase = 236.76v and 5A

Each and every phase different voltage.  How can i detect a missing Neutral situation

• Hi Rajamani,

I can suggest two more options and you can check which one works for you.

1. Using the ANGLEx registers to measure the angle between each of the voltage you can see if the Neutral is cut or not. In your first example above without the cut Neutral, the angles should measure 120 degrees and this measurement should always be stable as it comes from the utility. Then in the second example, the angle between the voltages comes out to <RY = 116.4, <YB = 122.2, and <RB = 116.9. This way you know that the Neutral is now floating and it has been cut.
2. The other way would be to monitor your power supply. Most typically the power supply is on the neutral creating a DC voltage of 9 to 24V, then there is an LDO which brings it down to 3.3V. If you monitor the higher DC voltage of 9-24V, then you can see when the supply is about to go down because the neutral was cut. This gives you some short amount of time to take action.

Regards,

Dlath

• Hello dlath,

We are also trying to detect Neutral loss using ADE7880. As suggested above, we tried reading ANGLEx register when neutral loss is simulated. But the values in ANGLEx registers does not change much to differentiate neutral loss from normal condition. We normally(without neutral loss) got the readings as <RY = 116, <YB = 122, and <RB = 122, hence we are unable to identify. Is there any other way to differentiate neutral loss?

Thanks and Regards,

Omkar