Large continuous process plants are increasingly resorting to use of non linear loads (NLL) such as DC drives, variable speed AC drives, UPS, increased electronic controls etc. to improve performance and productivity of their plants. The plant engineers are increasingly facing unfamiliar problems related to power quality (PQ) mainly problem of distortion of fundamental wave shape and associated effects.
Harmonics are as old a phenomenon as the introduction of AC System. Mercury arc rectifiers (MAR) developed in 1920’s and semiconductor controlled rectifiers (SCR) or thyristors developed in 1950’s created harmonics, due to their nature of non-linear loads. However, use of non-linear load was less then (typically less than 5% in 1960), to have any significant impact. But it is now increasing rapidly thus making Power Quality a great concern among plant engineers and associated equipment manufacturers.
Magnified harmonics cause severe stress on the plant & machineries. Electronics are the first to fail being weakest among all, followed by fuse, capacitors, thyristor, CT, Motor etc.
Author: Omer GUL