PowerQuality

Power Quality

What is Power Quality?Electric energy is one of the most important  production factors in modern manufacturing  industry. It is also an important commodity  for the power utility industry. For both par- ties, the quality of electric power is becoming  increasingly important. But what is Power  Quality?High Power Quality means a high rate of  efficiency in the networks with a low level of  electrical disturbances. Electrical disturban- ces can be categorized in voltage variations,  harmonics, interruptions and unbalance.  Here certain phenomena can be defined, i.e.  dips, transients, flicker etc., but also reactive  power balance, power factor and network  losses.Power Factor ImprovementA high power factor in the network means  low losses, high voltage stability and good  power flow control. It is achieved by balan- cing the reactive power consumption in the  network by switching capacitors or reactors.  Cover: Q ELECTRIC  specializes in power  quality measure-ments,  evaluation and analysis. Time Dn Frequency Diagram 1. Power measurement gives the input needed for  calculating and designing power factor compensation. Diagram 2. Harmonic measurements are used to define the  harmonic distortion in the network and give the input for calculating  harmonic filter details. The need for installation of capacitor banks  and switching sequences is calculated from  network models and power flow measure- ments in the network, see diagram 1.Harmonic FilteringThe fastest growing power quality phenome- non is harmonics, much due to the increasing  use of electronic appliances in households  and industrial networks. Harmonics, i.e. vol- tage and current with higher frequency than  the network fundamental frequency, are gene- rated by non-linear loads, such as frequency  converters, rectifiers and power electronics.  Harmonic distortion in a network also causes  amplification and resonance problems when  capacitor banks are installed, increasing net- work losses and production disturbances in  industrial machinery.Harmonic measurement, evaluation and cal- culation based on mathematical models help  solving these problems. Installations of pas- sive or active filters or redesigning existing  capacitor banks into filters are well proven  methods, see diagrams 2 and 3. Power 2

Frequency Diagram 3.The network impedance at different frequencies  defines the 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 EliminationSwitching capacitor banks generate transients  that can cause disturbances and equipment  failures in production facilities as well as in  home electronic appliances. Transients are  also generated by atmospheric phenomenon  like lightning and network switching. Tran- sients can be a nuisance due to their irregu- larity and non-foreseeable nature and the  solution to solve the problem is found only  after an extensive analysis, see diagram 4.Q-ELECTRIC Provides Complete ServiceQ-ELECTRIC specializes in providing com- plete Power Quality services for industrial as  well as utility networks. Among these servi- ces are measurements of:-  active and reactive power-  power factor-  current and voltage variations-  harmonics-  transients-  etc..  The measurements are performed according  to applicable standards and the results are  analysed and evaluated with theoretical mo- dels and presented in a detailed report. The  results from the measurements are then used  as input for solving Power Quality problems  or increasing the network efficiency. These  solutions include for instance:-  analysing the best location for reactive     power compensation in the network-  calculating switching cycles for opti-     mum power flow control in the network-  sizing capacitor banks for shunt- or       series compensation-  calculating and designing harmonic       filters for suppression of harmonic       distortion-  sizing surge arresters for transient       over-voltage protection.For further details on Q-ELECTRIC servi- ces, references or other information, please  do not hesitate to call or e-mail.  Impedance Voltage Time 3

Q ELECTRIC Nätkvalitet AB Lovisagatan 4 SE-115 23 STOCKHOLM, Sweden E-mail  [email protected] Phone  +46 8 663 18 69 Fax  +46 8 662 90 92 SECAP A04QE Edition 2, 2000-06 Produced in cooperation with   ABB Capacitors  AB. Printed with an INDIGO digital printing press at Elanders Novum,  Västerås, 0203