Passive filters-potentialities and limitations

New topologies for harmonic mitigation and active filters have come a long way and these address the line-harmonic control at the source. These mitigate some of the disadvantages of passive filters, however, for nonliner loads above 1 MW the passive filters are an economical choice. The paper discusses two types of filters: band pass filters and damped filters, which are commonly applied. The operation of these filters is described with respect to the design and system limitations. The operating constraints are then superimposed. The development of this approach shows that there are design limitations and large system changes or modifications can result in higher distortion or even damage to filters in extreme cases. The constraints and limitations that a designer faces in implementing an effective filter design with modern tools of harmonic analysis, measurements and system analysis are discussed. The paper shows that in most distribution systems it is practical and economical to implement passive filter designs, provided the required safeguards are considered.