Harmonic Filters

Improvement of power quality, energy savings and stabilisation of the power supply

The permanently increasing number of non-linear consumers in our electricity networks cause rising “network impurities”. We talk about network perturbations in a similar way to the way we talk about the environment with its water and air pollution. In an ideal situation, the generators in a power plant produce a pure sinus-shaped current from the output terminal. This sinus-shaped voltage form is regarded as the ideal form of alternating current and any deviation from this form is described as a network perturbations. More and more consumers take a non-sinus-shaped current from the network. The FFT fast-fouriertransformation of these polluted currents results in a wide range of harmonic frequencies which are usually referred to as harmonics.

Harmonics are damaging to electrical networks and can sometimes be dangerous. Connected consumers can suffer in a way which is similar to the unhealthy effect impure water has on the human body. This results in overload, reduced lifespan and under some circumstances can even lead to premature failure of electrical and electronic consumers. Harmonics overloads are the main cause of invisible power quality problems with enormous maintenance costs and investments for the replacement of defective equipments. Excessive network perturbations and the resulting poor power quality can also lead to problems in production processes and can even result in production stoppages.

Tuned passive harmonic filters

In special cases such as in weak (low short-circuit power) networks with simultaneously high harmonic loads (e.g. DC drives or ski lifts) or in cases where the energy supply companies or critical production processes require low THD-U values, which means that a “clean” electricity quality is required (e.g. research centres, semiconductor industries, long process chains...), it may be necessary to achieve more harmonic reductions than standard de-tuned systems can manage.

Tuned filter circuits may be the solution in these cases. Tuned filter circuits are adapted to the harmonic currents which must be absorbed, usually a 5th, 7th and 11th harmonic, and represent very low impedance pathes for these currents with the respective frequencies. These currents are then”sucked off ” and the network is cleaned of damaging harmonic currents.

These currents are then”sucked off ” and the network is cleaned of damaging harmonic currents. Tuned harmonic filters are solutions which are specific to the customer and generally after extensive network analysis individually designed.

Network optimisation with de-tuned PFC systems (harmonic filters) from Janitza® result in the following advantages:

  • Reduction of electricity bills through the elimination of reactive power
  • Reduction of electricity bills through reduced kWh losses
  • Avoidance of resonance problems and significant safety risks
  • Improvement of the general power quality (reduction of THD-U)
  • Saving of maintenance costs
  • Delay or avoidance of new investments through improved utilization of energy distribution systems and equipment
  • Stabilisation of production processes
  • Stabilisation of supply voltage