Power Quality

What is Power Quality?

Electric energy is one of the most importantproduction factors in modern manufacturingindustry. It is also an important commodityfor the power utility industry. For bothparties, the quality of electric power isbecoming increasingly important. But what isPower Quality?

High Power Quality means a high rate ofefficiency in the networks with a low level ofelectrical disturbances. Electrical disturbancescan be categorized in voltage variations,harmonics, interruptions and unbalance. Herecertain phenomena can be defined, i.e. dips,transients, flicker etc., but also reactive powerbalance, power factor and network losses.

Power Factor Improvement

A high power factor in the network means lowlosses, high voltage stability and good powerflow control. It is achieved by balancing thereactive power consumption in the network byswitching capacitors or reactors. The need forinstallation of capacitor banks and switching

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HARMONIZERspecializes in powerquality measure-ments,evaluation and analysis.

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Diagram 1. Power measurement gives the input needed forcalculating and designing power factor compensation.

Diagram 2. Harmonic measurements are used to define the harmonicdistortion in the network and give the input for calculating harmonicfilter details.

sequences is calculated from network modelsand power flow measurements in the network,see diagram 1.

Harmonic Filtering

The fastest growing power qualityphenomenon is harmonics, much due to theincreasing use of electronic appliances inhouseholds and industrial networks.Harmonics, i.e. voltage and current withhigher frequency than the network fundamen-tal frequency, are generated by non-linearloads, such as frequency converters, rectifiersand power electronics. Harmonic distortion ina network also causes amplification andresonance problems when capacitor banks areinstalled, increasing network losses andproduction disturbances in industrialmachinery.

Harmonic measurement, evaluation andcalculation based on mathematical modelshelp solving these problems. Installations ofpassive or active filters or redesigning existingcapacitor banks into filters are well provenmethods, see diagrams 2 and 3.

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Diagram 3.The network impedance at different frequencies definesthe parallel resonance frequency.

Diagram 4. Measuring transients could be time consuming and difficult,but is usually the only way to solve problems with erratic disturbances.

Transient Elimination

Switching capacitor banks generate transientsthat can cause disturbances and equipmentfailures in production facilities as well as inhome electronic appliances. Transients arealso generated by atmospheric phenomenonlike lightning and network switching.Transients can be a nuisance due to theirirregularity and non-foreseeable nature andthe solution to solve the problem is found onlyafter an extensive analysis, see diagram 4.

HARMONIZER Provides CompleteService

HARMONIZER specializes in providingcomplete Power Quality services forindustrial as well as utility networks. Amongthese services are measurements of:- active and reactive power- power factor- current and voltage variations- harmonics- transients

- etc..

The measurements are performed accordingto applicable standards and the results areanalysed and evaluated with theoreticalmodels and presented in a detailed report. Theresults from the measurements are then usedas input for solving Power Quality problemsor increasing the network efficiency. Thesesolutions include for instance:

- analysing the best location for reactivepower compensation in the network

- calculating switching cycles for opti-mum power flow control in thenetwork

- sizing capacitor banks for shunt- orseries compensation

- calculating and designing harmonicfilters for suppression of harmonicdistortion

- sizing surge arresters for transientover-voltage protection.

For further details on HARMONIZERservices, references or other information,please do not hesitate to call or e-mail.

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HARMONIZER Power Quality Consulting ABLovisagatan 4SE-115 23 STOCKHOLM, SwedenE-mail natan.gothelf@harmonizer.nuPhone +46 8 663 18 69Fax +46 8 662 90 92homepage www.harmonizer.nu

SECAP A04QEEdition 2, 2000-06

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