Computing power of 3 phase system without knowing the load configuration

Question

I am trying to find out the power consumption for a 3 phase balanced system below:

I only have access to the L1, L2, L3 and N connection points at the main connection box and I only know that it is connected to a mixture of 3 phase and single phase loads.

The RMS voltage measurements between each line and natural is as below:

V(L1 to N) = 241.7V

V(L2 to N) = 242.1V

V(L3 to N) = 244.0V

The voltage measurements between each line is as below:

V(L1 to L3) = 420.9V

V(L1 to L2) = 418.7V

V(L2 to L3) = 421.7V

The current measurements were taken using clamp meter and values are as below:

I(L1) = 9.99A

I(L2) = 10.34A

I(L3) = 10.05A

I(N) = 0.45A

Without knowing if the load is Y or Delta, how can I compute the power consumption in this setup?

Answer 1

Without knowing if the load is Y or Delta, how can I compute the power consumption in this setup?

The most important thing is power factor. You may have an RMS voltage and an RMS current but that doesn't tell you what their phase relationship is. For instance, if you connected an inductor across an AC line of 400 volts and the current taken was 10 amps, how much power would be taken from the supply?

Basically, the answer is that the power taken is zero watts. If on the other hand a resistor was used instead of an inductor, the power would be 4000 watts.

So, if you don't know what the load is in terms of R, L and C, you cannot predict power.

I am trying to find out the power consumption for a 3 phase balanced system

You measured this: I(N) = 0.45A and that means that the load isn't balanced. It's not bad but, it ain't perfectly balanced. Given the small variations in your line and phase voltages, you cannot say that the supply is balanced either.