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In three phase three wire system, is it necessary to calculate phase wise energy?

As per my knowledge, in three phase three wire system we are concerned about only total power/energy.

But does it have any meaning to calculate & show phase wise energy in three phase three wire system.

Thanks & Regards, Nitin K.

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  • \$\begingroup\$ Sure it has meaning. With single-pole tripping we open one phase to clear faults while allowing the remaining 2 phases (and earth) to transmit power. \$\endgroup\$
    – relayman357
    Commented Feb 26, 2020 at 4:18

2 Answers 2

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In three phase three wire system, is it necessary to calculate phase wise energy?

With only three phases and no access to a star point on the load (if it is a star connected load and there's nothing to suggest that it is) then, it's impossible to calculate power or energy in any of the three parts of the load.

The only method to calculate load power is the two watt meter method and this doesn't distinguish individual phase powers: -

enter image description here

Picture from here.

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  • \$\begingroup\$ I've a energy meter which calculates & updates phase wies energy in 3 phase 4 wire network but in 3 phase 3 wire network, it only calculates & updates total energy ( not phase wise energy). In 3P3W, using two wattmeter method we calculate total power P = P1 + P2. Then in this case we should update P1 & P2 right? In my case it only updating total P. \$\endgroup\$
    – neeteen09
    Commented Mar 3, 2020 at 4:49
  • \$\begingroup\$ You asked: In three phase three wire system, is it necessary to calculate phase wise energy? - and I said no to that question and gave you the reasons. I don't know anything about your energy meter. @neeteen09 \$\endgroup\$
    – Andy aka
    Commented Mar 3, 2020 at 8:04
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Even with a three-wire system it is possible to have unbalanced loads so, yes, phase power may be important. I work on machines where heaters and power supplies are connected phase to phase and some imbalance results.

My house is on a rural supply and all the houses around me are supplied by one single-phase 20 kV transformer. The network company will certainly be interested in monitoring power on each of these circuits eith a view to balancing them out.

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