Power Factor Correction
What is Power Factor Correction?
Reactive power is necessary for the generation of electromagnetic fields. Because these fields continuously develop and reduce, the reactive power fluctuates between producers and users. In contrast to active power, reactive power they cannot be used i.e. cannot be converted into another form of energy and strain the electricity supply network and the production equipment (generators and transformers). Furthermore, all energy distribution systems must be constructed larger for the allocation of reactive currents.
It is, therefore, necessary to reduce the same amount of occurring inductive reactive power near to the consumer with a capacitive reactive power. This process is called compensation. During compensation, the ratio of reactive power in the network reduces by the reactive power of the power capacitor or the PFC system. The energy generation systems and the energy transmission systems are, therefore, discharged from reactive currents.
What can be done to combat reactive power?
Energy supply companies invoice the reactive consumption whereby significantly increased costs usually occur. Reactive power compensation systems reduce the high costs for extra reactive consumption and offer the following additional advantages:
- Reduced electricity invoices through lower reactive power costs
- Reduced Ohm losses which means lower kWh consumption
- Discharge of transformers, cables and supply systems
- Increased lifespan of electrical distribution systems
- Active environment protection through the reduction of CO2 emissions
- Improved utilization of networks i.e. additional consumers (kWh) can be connected
- Voltage stabilisation (reduced apparent current reduces the voltage drops)
Harmonic filters More information to harmonic filtersImprovement 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.
What can you do to improve your power quality?
There are different solutions for the restriction of harmonic currents which are caused by non-linear consumers which can therefore contribute to the improvement of power quality.
I. De-tuned PFC systems (passive, de-tuned filter)
Passive filters and de-tuned PFC systems are some of the traditional measures. In de-tuned PFC systems, power capacitors are switched to the network individually or in groups and are regulated according to the power factor. Low-pass filters with a de-tuning factor, which is more or less dependent upon a broadband filter effect (towards high frequencies), is generated through the filter circuit reactors which are connected to the capacitor in series. This means that the occurrence of resonance is avoided and some harmonics are reduced from the network.
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
II. Tuned 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.
Tuned harmonic filters are solutions which are specific to the customer and are not listed in this catalogue as standard products. Please contact our sales department or download our “power quality” questionnaire from the internet.
III. AHFI – Active Harmonic Filter
Passive PFC systems are only capable of compensating a few selected harmonics. Depending upon the network conditions, passive PFC systems tend towards resonance and can become overloaded. Active harmonic filters serve the purpose of reducing harmonics caused by non-linear consumers and provide highly dynamic reactive power according to requirements. Active harmonic filters are connected parallel to the harmonic producers. The AHFI analyses the range of harmonics produced by the non-linear consumers and feeds a counter-phase harmonic compensation current into the network. This means that the corresponding harmonic distortions are neutralised at the connection point.
In addition to the good filter effect due to the high bandwidth and the excellent peak current properties of the AHFI, the extremely high dynamics (i.e. rapid reaction to changing harmonic loads) is one of the fundamental advantages of the AHFI active harmonic filter. Due to the higher costs in direct comparison with passive filter solutions, active filters are mainly used in the following cases:
In systems in which no, or only limited, additional capacitor power may be installed (power factor close to 1)
Clearly defined harmonic level (THD-U) e.g. critical production with long process chains (chemical industry, semiconductor production)
High neutral conductor currents (e.g. 3rd harmonic)
Unsymmetrical load on networks
High dynamic of the harmonic distortion and reactive power
Highest harmonic distortion or weak grids
Typical areas of application
- Oil, gas and steel industry
- Water treatment
- Cement and automobile industry
- Paper industry
- Tooling machines, drive technology (frequency converter, servo applications,DC drives, DC supplies)
- Welding machines
- USV systems, computer centres (computer and network connections)
- Banks and data centres
- Elevator industry, tunnel supplies (ventilation)
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