Power quality transducer for use with supervisory control systems

Abstract

A method and apparatus for detecting power quality or disturbance events, such as voltage swells, sags or impulses, in power signals at remote locations of a power distribution system and for conveying information relating to the power disturbances to a central location. Voltage and/or current signals in electric power lines are monitored and converted to low level analog signals. The low level signals are processed by analog processing circuits or are digitally sampled and processed by digital processing circuits to detect power disturbances. Each power disturbance is characterized according to multiple parameters. The characterization information is encoded into a single signal. This is done by assigning a subset of a range of possible values of the signal to represent a parameter and then assigning a value within each subset of the range to represent another parameter. A sampling system located at the central location periodically samples the encoded signal at each remote location to collect information relating to power disturbances occurring throughout the power distribution system. Because sampling occurs only periodically, the encoded signal maintains its value for an amount of time after a power disturbance is detected that is long enough to ensure that it will be sampled. Then, the encoded signal returns to the level representative of an absence of a power disturbance until the next power disturbance occurs.