Distributed current and voltage sampling function for an electric power monitoring unit
AssigneeSiemens Energy & Automation, Inc.
InventorsMichael A. Kinney, James T. Cronvich, Wayne M. Zavis
Life of this patent
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Abstract
A low voltage AC electric power monitoring system includes a processor which samples the current and circuit breaker system includes a processor which samples each of the current components at seventeen samples per cycle to obtain current samples representing a single period of the AC power signal. The processor samples the voltage component at different points in the voltage cycle over several cycles to obtain voltage samples representing a single period of the AC power signal.
Claims6
A controller suitable for monitoring electrical power lines which transmit alternating current electric power including a periodic voltage component and a periodic current component, having a predetermined frequency, to a load circuit, said apparatus comprising:
- current sampling means for digitally sampling the current component of the power during a single period thereof, at a rate which produces a number of digital samples sufficient to resolve the current component to the Nth harmonic of said predetermined frequency during each period of said periodic current component, where N is an integer greater than 2;
- and
- voltage sampling means for digitally sampling the voltage component of the power, during a sampling interval which includes multiple periods of the voltage component, at a rate less than the rate used to sample the current component to produce a number of digital samples sufficient to resolve the voltage component to the Mth harmonic of said predetermined frequency during the sampling interval, where M is an integer greater than 2.
A controller suitable for monitoring electric power lines which transmit multi-phase alternating current electric power to a load circuit, wherein each power phase includes a periodic voltage component and a periodic current component, having a common frequency, said controller comprising:
- means for digitally sampling the current component of each phase of the power during a single period thereof, at a rate which produces a number of samples sufficient to resolve the current component of each power phase to the Nth harmonic of the common frequency during each period of said periodic current component, where N is an integer greater than 2;
- and
- means for digitally sampling the voltage component of each phase of the power, during a sampling interval which includes multiple periods of the voltage component, at a rate less than the rate used to sample the current component to produce, during each sampling interval, a number of digital samples sufficient to resolve the voltage component of each phase of the power to the Mth harmonic of the common frequency, where M is an integer greater than 2.
A controller suitable for monitoring electrical power lines which transmit alternating current electric power including a periodic voltage component and a periodic current component, having a predetermined frequency, to a load circuit, said apparatus comprising:
- first sampling means for digitally sampling one of the respective current and voltage components of the power during a single period thereof, at a rate which produces a number of digital samples sufficient to resolve said one component to the Nth harmonic of said predetermined frequency during each period of said one periodic component, where N is an integer greater than 2;
- and
- second sampling means for digitally sampling the other component of the power, during a sampling interval which includes multiple periods of said other component, at a rate less than the rate used to sample said one component, to produce a number of digital samples sufficient to resolve said other component to the Mth harmonic of said predetermined frequency during the sampling interval, where M is an integer greater than 2.
Dependencies are inferred from the claim text.