Harmonic distortion in the distribution system caused by connected loads

NECA Technical has received a number of calls asking about equipment complying to Standard IEC 61000.3.6 which pertains to harmonic distortion in the distribution system that is caused by connected loads.

The authority asks for this as loads that generate harmonics can cause the network voltage to become unstable and distribution transformers to operate at elevated temperatures.

To be able to see harmonics, there is a need for specialised measuring equipment and the ability to be able to interpret the readings. This generally falls into the sphere of electrical engineering. There are two methods of eliminating harmonics if present, this can be done with either passive or active filtering. These filters have to be designed to fit the particular site and its specific values of distortion. Again, generally the scope for an electrical engineer. 

Harmonics can create hot neutral wires with elevated currents which can also create loose connections.

One method an electrician can use to possibly see harmonic issues is to take temperature measurements of the actives and associated neutral wire, and if the neutral wire is hotter than the actives, this could show issues with the installation that would require further investigation as to the cause.

There is the need for manufacturers to design a product that does not produce harmonics. If as electrical contractors, we install quality approved equipment acquired from reputable wholesalers, there should be no problems as compliant equipment will have been built to standards.