A virtual environment for power quality analysis

The quality of power at the consumer site is affected by (a) temporary disturbances that may originate anywhere in the system and (b) waveform distortion from nonlinear loads. The sources of disturbances are multiple and with varying parameters. For example in many places of the world, the most frequent disturbances originate from lightning activity near electric installations. Lightning may result in flashover causing voltage sags to some portion of the distribution system, voltage swell to other areas, as well as interruption of power. The number of customers affected depends on the design of the system and placement of interruption devices, while the level of voltage sags or swells may depend on the grounding system, size of neutral, etc. In order to study these effects, we have developed the Virtual Power System (VPS). The VPS is a time domain simulation tool, which can simulate the sequence of events due to disturbances and determine the effects of a specific disturbance on specific customers. The paper describes the operation of the VPS and provides examples of disturbance event sequences for a typical power distribution system. The VPS has a Monte Carlo simulation function, which determines measures of power quality at customer loads in a statistical sense. This function can be used to optimize the design of a power distribution system for the purpose of maximizing power quality.