Negative and Incorrect values

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1

Negative and incorrect values in 3 phase measurements

Hey I have used iotawatt for 3 phase measurements of my house using derived method.

I have attached pic how I clamped CTs (yhdc sct-013 100 A/ 50mA) to each phase. Here Input 1 is phase A, input 2 is phase B and Input 3 is phase C.

There is 1 hp motor connected to input 1 beside other lighting and fan loads. input 1 showing 456 watts without motor when I switch on motor it jumps to around 840 watts. (I was expecting 456 + 746 = 1202 watts)

Moreover, there is also another 1 hp motor connected to input 2 beside other common loads. so without motor it was around -650 to -700 watts at that time and when I switch on the motor it jumps to -108 watts ( I am not getting this).

I don’t know what

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wrong I have done.I have clamped all CTs in same orientation.
I have checked Allow negative power, reverse checkboxes.
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2

The procedure for setting up derived three phase is documented here.

I can see from the picture that your CTs on Input_1 and Input_2 are not oriented the same. If you l;ook at the arrows on the top of each, I believe Input_1 is pointing away from the main breaker, and Input_2 is pointing toward the main breaker. I can’t see Input_3 well enough to determine it’s orientation.

From there, assigning the three CTs to phases is not arbitrary. Phase A must be the phase that supplies your VT. The documentation offers some advice as to how to determine that, and also how to determine the assignment of the remaining two phases.

Your symptoms are classic incorrect phase assignment/ CT orientation.