Harmonics on HV motors

[Deansharafi]

Hi all,
I am investigating power recordings on a site, which does not have considerable sources of producing harmonics. However I see that there are considerable harmonics on the red phase current only which seems strange to me.
There are small harmonics on voltage, which is normal and small harmonics on currents except for the Red phase.
How can this large harmonics be present on current, whereas the voltage of the same phase does not have these. Is it possible? This feature is almost the same throughout the plant. (The main electrical load in the plant are three phase 3.3KV motors).
Typical recordings look like below for the 3rd, 5th 7th harmonics:
Your thoughts please.

Time VA VB VC IA IB IC
10:25:08 3.7 5.9 3 7.1 2.8 2.8
10:25:18 5.2 5.9 3 7.1 1.4 2.8
10:25:28 4.5 6.7 2.2 5.7 1.4 4.3
10:25:38 3.7 6.7 3 5.7 1.4 2.8
10:25:48 4.5 5.9 2.2 5.7 1.4 1.4
10:25:58 5.2 6.7 2.2 4.3 2.8 1.4
10:26:08 4.5 6.7 2.2 19.9 1.4 2.8
10:26:18 5.2 5.9 2.2 9.9 1.4 1.4
10:26:28 5.2 5.9 4.5 5.7 2.8 2.8
10:26:38 3.7 6.7 1.5 11.3 2.8 1.4
10:26:49 4.5 5.9 1.5 28.4 1.4 2.8
10:26:59 3 5.9 1.5 12.8 2.8 1.4
10:27:09 4.5 5.9 3 5.7 1.4 1.4
10:27:19 4.5 5.2 2.2 5.7 0 1.4
10:27:29 4.5 5.9 3 8.5 2.8 2.8
10:27:39 4.5 5.9 2.2 14.2 1.4 1.4
10:27:49 4.5 5.9 3 7.1 2.8 1.4
10:27:59 3.7 5.9 2.2 7.1 2.8 2.8
10:28:09 3.7 6.7 2.2 5.7 2.8 2.8
10:28:19 3.7 6.7 2.2 5.7 1.4 2.8
10:28:29 4.5 5.9 2.2 7.1 1.4 1.4
10:28:39 3.7 5.9 3 7.1 2.8 2.8
10:28:49 3.7 5.2 2.2 27 2.8 2.8
10:28:59 3.7 5.9 3 7.1 1.4 1.4
10:29:09 3 5.9 3 7.1 2.8 1.4
10:29:19 3.7 6.7 2.2 5.7 1.4 2.8
10:29:29 3.7 5.2 2.2 18.4 1.4 2.8
10:29:39 3 5.9 3 5.7 2.8 1.4
10:29:49 4.5 5.2 2.2 5.7 1.4 2.8
10:29:59 3.7 5.9 2.2 7.1 1.4 1.4
10:30:08 3.7 5.2 3 9.9 1.4 1.4
10:30:18 4.5 5.2 3 5.7 2.8 2.8
10:30:28 3.7 4.5 3 5.7 1.4 1.4
10:30:38 3.7 5.2 3 5.7 1.4 1.4
10:30:48 3.7 5.2 3 4.3 2.8 2.8
10:30:58 4.5 5.2 3 5.7 2.8 1.4
10:31:08 4.5 5.9 3 14.2 1.4 1.4

 

[pqsl]

What recorder did you use for these measurements?
What are the units for measurements Volts, Amps or %?
If measurements are Volts, Amps then what are the fundamental or RMS values?
If measurements are in % then is it in % of fundamental or RMS?
More info is needed.
Did you use CT’s VT’s to measure current and voltage?
Is recording instrument reading correctly?

 

[Deansharafi]

The units are volts and amps RMS values. The measurement has been done from CTs and VTs. The fundamental voltage is 3300V and current is 100A. I don't know what sort of recorder has been used.
My question is: can harmonics on current of one phase be so high without affecting harmonics on voltage of the same phase? As you see in the above example harmonics of A phase voltage is same as the other phases, whereas the current harmonics are so high. How can this effect be explained.

Thanks for your thoughts.

 

[pqsl]

One explanation might be that the source is low impedance.
Another is that maybe instrument is not sampling simultaneously voltage and current.
Is this delta system? Is Va actually Va-b?