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                                                         7







                              Harmonic studies of


                             power compensating



                                                   plant










                         7.1   Introduction


                      The use of power electronics-based equipment in high-voltage power transmission
                      and in low-voltage distribution has increased steadily over the last three decades.
                      Notwithstanding their great many operational benefits, they also have increased the
                      risk of introducing harmonic distortion in the power system because several of these
                      devices achieve their main operating state at the expense of generating harmonic
                      currents. In the early days, most applications of this technology were in the area of
                      HVDC transmission (Arrillaga, 1999). However, the SVC which is a more recent
                      development, has found widespread use in the area of reactive power management
                      and control (Miller, 1982). In the last 20 years or so, a substantial number of SVCs
                      have been incorporated into existing AC transmission systems (Erinmez, 1986;
                      Gyugyi, 1988). Many utilities worldwide now consider the deployment of the newest
                      and most advanced generation of power electronics-based plant components,
                      FACTS and Custom Power equipment (Hingorani, 1993; 1995), a real alternative
                      to traditional equipment based on electromechanical technologies (IEEE/CIGRE,
                      1995).
                        Over the years, many adverse technical and economic problems have been traced
                      to the existence of harmonic distortion. Professional bodies have long recognized
                      harmonics as a potential threat to continuity of supply and have issued guidelines on
                      permissible levels of harmonic distortion (IEEE IAS/PES, 1993). However, it is
                      generally accepted that this problem, if left unchecked, could get worse. Hence, great
                      many efforts are being directed at finding new measuring, simulation and cancella-
                      tion techniques that could help to contain harmonic distortion within limits. Sub-
                      stantial progress has been made in the development of accurate instrumentation to
                      monitor the harmonic behaviour of the network at the point of measurement
                      (Arrillaga et al., 2000). However, in planning and systems analysis the problem must
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