HARMONICS SOURCE

[JAMartinezB]

Hi, I would like to know how to determine whether a customer is generating harmonics or is receiving them from the net.

Something similar like the cause of a voltage drop. If the customer is causing the voltage drop in his inner network, then should be a spike in the current drawn by the customer. But if there isn´t any increase in the current, then the voltage drop is associated with the outside network.

Regards.

 

[PHovnanian]

Measure the voltage THD with no customer loads connected.

You will have to model the customer loads to determine the effect of the level of voltage harmonics seen. Then, measure the current THD actually drawn by the loads and compare that to the levels expected due to the incoming voltage THD. Also, measure how the voltage THD changes due to the loads.

The voltage THD seen on the customer's service is due to current harmonics drawn by all loads (this customer's plus others) fed through a common impedance. However, some loads which do not draw harmonic currents when supplied with a clean sine wave will do so if supplied with high THD voltages. Capacitors are one example. These harmonic currents will, in turn, exacerbate the voltage THD seen, even though it could be argued that they are caused by the supplying system.

Other types of loads (nonlinear) will draw harmonic currents even when supplied with a clean sine wave.