Harmonic detection and filtering - Schneider Electric

Solutions to attenuate harmonicsEn bref6.1 General solutionsTo limit the propagation of harmonics in the distribution system, a number ofmeasures may be taken, particularly when designing a new installation.There are three different types ofsolutions that may be used toattenuate the effects of harmonics:b modifications to the installationb use of special devices in the powersupply system (inductors, specialtransformers)b filters.6.1.1 Positioning the disturbing loads upstreamin the systemThe overall level of harmonic disturbance increases as the short-circuit powerdecreases.Economic considerations aside, it is therefore preferable to connect the disturbingloads as far upstream as possible (see figure 12a).E95236Figure 12a - Supply of non-linear loads as far upstream as possible (recommended diagram).6.1.2 Grouping the disturbing loadsWhen preparing the single-line diagram, separate where possible the disturbingequipment from the other loads (see figure 12b). Practically speaking, the differenttypes of loads should be supplied by different busbars.By grouping the disturbing loads, the possibilities of angular recomposition areincreased. The reason is that the vector sum of the harmonic currents is lower thantheir algebraic sum.An effort should also be made to avoid the flow of harmonic currents in the cables,thus limiting voltage drops and temperature rise in the cables.E95237Figure 12b - Grouping of non-linear loads and supply as far upstream as possible(recommended diagram).3030