Harmonic Filters are pieces of equipment designed to absorb a high proportion of voltage and current distortion that is produced by a range of modern electrical equipment and effectively clean up the supply.
This harmonic distortion can cause malfunctions of:-
> Electronic equipment
> Failures of Power Factor Correction Capacitors
> Light fittings
> Cable overloads
> Switchgear overloads
> Transformer overloads
> Increased wear in motors and other equipment
Two types of Harmonic filter can be provided
Active Filter – These are power electronic devices that analyses the incoming supply current wave form and injects a current into it, in anti-phase to the measured harmonic, in order to cancel the distortion and return the waveform to sinusoidal.
Passive Filter –Designed for specific harmonic frequencies. A more cost effective alternative.
Harmonic Filters
A harmonic filter is a circuit comprising capacitor, inductor and sometimes resistor. The values selected are designed to form a low impedance path for a particular harmonic frequency. The filter, therefore, absorbs a high proportion of the harmonic generated and removes it from the system. If more than one harmonic is causing problems, a number of individual filter legs, each designed to absorb a specific frequency, are provided.
PQE Ltd. a leading supplier of harmonic filter equipment worldwide with more than ten years experience in this field. we have supplied a very wide range of filters custom built for specific applications operating at voltages from 400V to 33kV, with reactive power outputs from a few kVA to several MVA. Many examples of specific case histories are available on request.
Determination of Harmonic Levels
Through many years of working with harmonics PQE Ltd have developed both experience and expertise in accurately predicting the consequences of connecting harmonic generating loads on to a given Power System. Sophisticated computer models have been developed to enable the design of highly effective harmonic filters, both to eliminate the harmful consequences of harmonics and also to ensure compliance G5/4