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I was reviewing an energy meter specification and I came across neutral current measurement.

What is the importance of neutral current measurement in an energy meter for three phase power supply?

I tried to find the importance, but all I found was that it enhances tamper-detection techniques but does not say how.

Can someone tell me if it is really necessary to have this feature on an energy meter?

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    \$\begingroup\$ Please don't SHOUT in your title! \$\endgroup\$ – Bimpelrekkie Dec 25 '20 at 13:06
  • \$\begingroup\$ Can you link the specification? \$\endgroup\$ – LShaver Dec 25 '20 at 13:21
  • \$\begingroup\$ edmi-meters.com/wordpress/wp-content/uploads/2019/11/… \$\endgroup\$ – miky-1 Dec 25 '20 at 13:29
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    \$\begingroup\$ That link (which should be in the question rather than buried in the comments) doesn't mention neutral current measurement in the context of tamper-detection. \$\endgroup\$ – Transistor Dec 25 '20 at 14:32
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all I found was that it enhances tamper-detection techniques

That's correct.

A 3P e-meter can still operate, and can measure phase currents, without having the neutral connected.

Let's assume the neutral is not connected to the meter. R, S, and T phases pass through the meter and goes to the end user. Any phase-phase combination usages can be logged by the meter. But if the end user brings a neutral then he/she can use any phase with that neutral illegally and the meter will not be able to measure it correctly.

If the meter measures the neutral current then it can compare it with phase currents and can detect any illegal usage. We know that the neutral current is zero in a perfectly balanced system, so this may not work in perfectly balanced systems; but in practice there's always an imbalance. So, measuring the neutral current can work anyways. And it's the cheapest and the easiest-to-apply way for tamper-detection.

PS: Here in Turkey, illegal electricity usages are quite high in south-eastern region. So TEDAŞ (Turkish Electricity Distribution Corp) have been renewing existing 3P e-meters with ones having neutral current measurement.

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  • \$\begingroup\$ Thank you Rohat Kilic ,Do you think it is still necessary for customers who are supplied with a voltage level above 15kv? \$\endgroup\$ – miky-1 Dec 28 '20 at 7:24
  • \$\begingroup\$ @miky-1 I personally have no certain knowledge, sorry. But I think that it totally depends on the requirements of tamper detection. As I mentioned in the example above, if the distributor worries about tampering then neutral current measurement can be a necessity/requirement for them. \$\endgroup\$ – Rohat Kılıç Dec 28 '20 at 11:53

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