measure the three phases of one set of parallel conductors ?

[Andy32821]

Hi Everyone,

I use a three-phase power quality meter to check for power problems in commercial facilities.

Many times to measure the current on larger switch boards is impossible with clamp on current transformers and is even sometimes impossible with the flex CTs, because of the many parallel conductors.

If I measure the current of the three phases of one set of parallel conductors will I get true waveform and other quality related measurements?

Is this an acceptable practice?

This would make my life much easier.

Thanks,

Andy

 

[davidbeach]

You won't get revenue quality metering, but you should get a good picture of what is going on in the circuit. If an IR scan doesn't show any obvious problems with the terminations, like one having much higher impedance than the others, you should find that you will be measuring 1/n times the total current flow in the n parallel conductors to within a few percent. If each of the parallel conductors has the same impedance characteristics, with the only difference being a slight difference in length (1% or less ideally), the current from one should be good representation of the currents in the others.

 

[dpc]

I agree with David and have done the same thing myself. If your concern is power quality meassurement, then this approach will work fine as long as you remember to document the test setup.

The IR scan is a good idea, or you can check the current in each conductor with your clamps to assure yourself that current is splitting roughly equally.