Most electrical transmission and distribution systems have been designed to operate at the fundamental frequency only and the presence of non-linear loads often stress distribution equipment and can disrupt normal power supply operation.
Effects of Harmonics
Cause transformers derating and/or overheating
Reduces overall electrical system power factor e.g. PF0.6 (Energy wastage)
Generators unable to switch on or Capacitor Bank burnt
Cause Overheating to cables resulting in possible short circuit
Interference to communication equipment – resulting in data loss
The harmonic components of order 3 (150 Hz) in three-phase systems become homopolar, for instance: They converge on the neutral conductor and overload it. In the absence of the neutral, circulating currents may occur inside the three-phase appliances, connected in triangular form, generating dangerous overloads in this situation as well.
In single-phase systems, personal computers are classic examples of heavily-distorted loads with a high content of 3rd order harmonics which, as described above, will have an effect on the neutral. The conductor must, therefore, be sized appropriately, otherwise overheating will occur, thus reducing its life and quality.
They can cause failure of PLC, DCS, computer, and other sensitive low voltage power supplies.
Harmonic currents can be improved by installing Active Harmonic Filtering (AHF) equipment. To learn more about our Active Harmonic Filters, click on the products above or contact us to receive the best assistance from our Technical Sales Engineers.Customers with Variable Speed Drives
The Rural Network Harmonics Standard affects all customers that have connections with a cumulative VSD load exceeding 20kW.
The Standard was revised and updated during January 2014. In addition to new installations of Variable Speed Drives (VSD's), effective from 20 January 2014, all existing connections with a cumulative VSD load exceeding 20kW are required to have a harmonic filter installed (or similar mitigation).