Microprocessor device installation limitations based on harmonic distortion

Microprocessor-based devices such as personal computers (PCs) are known to produce nonlinear loading in electrical power systems. This produces harmonic distortion in the system which, by IEEE Standard 519, must be limited to a preset value. This distortion limitation produces, in turn, a maximum limitation on the number of microprocessor-based devices which can be allowed to load the system. In the present work, a mathematical model is developed which allows this maximum limit to be computed based on two important system ratios. These are the peak current ratio (linear to nonlinear fundamental) and the harmonic distortion ratio (maximum total load harmonic distortion to PC harmonic distortion). The model allows for easy analysis of an existing facility to determine an upper limit on the number of identical microprocessor-based devices which can be installed without exceeding a preset level of total harmonic distortion in the electrical power system