Harmonic Filters

Harmonic filters are used throughout industry for the attenuation of harmonic distortion on electrical power networks.

Enspec Power Ltd (EPL) design and manufacture the VArComp^® range of harmonic filters at all voltage levels (400Vac – 500kVac).

What are harmonics?

Harmonics are multiple integers of a fundamental frequency created by non-linear loads. A waveform is said to be distorted by harmonics when their presence can be measured superimposed upon the fundamental. The nature of non-linear devices is such that the current through them is not proportional to the voltage across them - thus if a sinusoidal voltage is applied to a non-linear device, (eg, VSD, UPS, inverter), then the current that flows will not be sinusoidal.

Using a mathematical technique known as Fourier analysis, it can be shown that the current waveform actually consists of a fundamental component with the same frequency properties as the applied voltage, plus harmonic components at various frequencies.

The detrimental effects of harmonic distortion can be manifested in many different ways depending upon various factors such as the level or amplitude of harmonics present, strength of supply or fault level and impedance of the electrical network. Below are just a few examples of harmonic ill-effects that can all lead to maloperation of components and even premature failure of electrical plant:

Increased heating effect on electrical distribution equipment and cables
Increased electrical insulation stresses - insulation breakdown
Electronic mis-timings: VSD's, robots, computers, etc.
Capacitor overloads - premature failure

Increased maintenance requirements and downtime
Flickering fluorescents
Protective device trippings
Fuse and overload relay operations

Engineering Recommendation G5/4-1

To minimise the effects of harmonic distortion on the UK's electricity distribution network, Engineering Recommendation G5/4-1 produced by the Electricity Association sets out the limits of harmonic distortion values that may be generated by individual electricity users at their point of common coupling (PCC).

EPL can help you to determine, achieve and maintain G5/4-1 compliance.

Accurate harmonic spectrum information and system details from on-site measurements provide the basis for accurate VArComp^® harmonic filter design using the latest in system-modelling computer software.

VArComp^® harmonic filters may be designed to attenuate any level of harmonic distortion dependant upon individual client requirements and in conjunction with G5/4-1 recommendations where necessary.

For more information on harmonic filters, please contact EPL directly .