Most of the industrial and even a remarkable part of commercial loads produce harmonic currents, which reduce the power quality level of the system, if not filtered at the closest point to where they are produced. The most economical and simple way of harmonic filtering is to use Harmonic Filters. Harmonic Filter is an equipment consisting of passive circuit elements such as capacitor, reactor and resistor. It is used for reactive power compensation while eliminating unwanted harmonic currents. It provides a low impedance path at one or more specified frequencies in the network, which prevents the currents at those frequencies from flowing to the grid. Moreover, since they also make reactive power compensation, they provide voltage support to the network. They are used mostly in heavy industries such as cement, textile, iron & steel factories, etc. They are preferred over Conventional Compensation due to several reasons, some of which are: - Restrained inrush currents, and - Lower risk of parallel resonance Harmonic filters are often used together with TCR in order to be able to control the reactive power output, and the total system is called an SVC. We have ten years of experience in design and implementation of different type of harmonic filters at residential and distribution voltage levels. - Power quality measurement prior to design, - Equipment selection and impedance calculations with respect to frequency spectrum, - Correct selection of location are some of the important things in the design of harmonic filters to avoid risks of over-currents and over-voltages in the network. Without having knowledge on these, an unqualified and unexperienced implementer may bring harm to both the customer and grid.
