Harmonic Filters
Harmonic Filters are pieces of equipment designed to absorb a high proportion of the 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:-
- Failures of Power Factor Correction Capacitorsv
- Cable, Transformer and Switchgear overloads
- Malfunction of electronic equipment
- Increased wear in motors and other equipment
- Problems for neighbouring consumers
- Light fitting failures
P.Q.E. design and manufacture harmonic filters. Through on-site harmonic measurements, we provide accurate harmonic filter design which will reduce harmonic distortion to a level within the G5/4 limits.
We are a leading supplier of Harmonic Filters worldwide with many years of experience in this field. We have supplied a wide range of Harmonic Filters custom built for specific applications operating at voltages from 400V to 33KV.
Active Filter or Passive Filter?
Active Filters will remove virtually all distortion. This type of filter is series connected. It measures the waveform distortion continuously and used power electronics to generate a current waveform which is identical but anti-phase to that which it is monitoring. When this is injected into the supply it cancels the distortion and the mains input is restored to an almost pure sinewave.
Active Filters are available in a wide range of ratings and can be used on any LV system. When correctly rated, active filters will cope with future additions to harmonic generating loads.
Passive Filter – These are designed to remove specific harmonics rather than the full spectrum of distortion. Normally used to eliminate problems and achieve compliance with the distortion limits specified in Engineering Recommendation G5/4. Generally more cost effective than Active Filters.
Passive filters are one or more circuits comprising capacitor, inductor and sometimes resistor. The values selected are designed to form low impedance paths for specific harmonic frequencies. The harmonic filter, therefore, absorbs a high proportion of the harmonics generated and removes them from the system.
P.Q.E. can advise you which of these harmonic filters will best suit your needs and will custom design the filter to fit your requirements.
Engineering Recommendation G5/4
If harmonics were limited to the site generating them, only the producer would suffer the ill effects. Unfortunately, this isn’t the case – distortion is ‘exported’ onto the mains supply and often causes problems for neighbouring consumers.
Electricity suppliers have a duty to provide ‘clean’ power, i.e. without distortion. They can’t do this when their consumers generate harmonics which pollute the mains.
G5/4 was produced to set limits on the amount of distortion which is acceptable. It specifies limits for harmonics at the incoming mains: total harmonic voltage distortion and the maximum acceptable current of each harmonic.
It is believed that distortion at or below the levels stipulated should not have adverse effects upon other consumers’ electrical equipment nor should it cause overloading of the distribution system.
G5/4 may have unfortunate consequences for new consumers: if distortion of the mains supply is already at or close to the limits, they are obliged to fit harmonic filtration if they intend to install V/S drives or other harmonic generators. Effectively, they are paying for the mess caused by others.
What Can Be Done?
PQE can design and build harmonic filtration equipment to reduce distortion to acceptable levels, ie below G/4 limits which will eliminate failures and malfunctions and remove the liability which exists when those limits are exceeded.
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Harmonic Filters What Are Harmonics?
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