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1. (EP1900076) AUTOMATED PRECISION ALIGNMENT OF DATA IN A UTILITY MONITORING SYSTEM
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Claims

1. A method of aligning data measured by monitoring devices (M, 128, 130) coupled to a power monitoring system (120), characterized in that it comprises:

receiving, at a controller (132) remote from said monitoring devices, reference signal data from a reference monitoring device (128), said reference signal data representing at least frequency or amplitude variations in current or voltage from an electric grid measured by said reference monitoring device for a predetermined number of cycles of said current or voltage sensed by said reference monitoring device, said reference monitoring device storing a reference count (212) associated with each of said cycles of current or voltage sensed by said reference monitoring device;

receiving, at said controller (132), second signal data from at least a second monitoring device (130), said second signal data representing at least said frequency or amplitude variations in current or voltage from said electric grid measured by said second monitoring device for a predetermined number of cycles of said current or voltage sensed by said second monitoring device, said second monitoring device storing a second count (212) associated with each of said number of cycles of current or voltage sensed by said second monitoring device; and automatically aligning said reference signal data with said second signal data to a common reference point in said respective current or voltage sensed by said reference monitoring device and said second monitoring device by:

computing a plurality of correlation coefficients each produced by a cross-correlation algorithm (400, 500, 600) based on at least part of said reference signal data and at least part of said second signal data until one of said correlation coefficients produced by said cross-correlation algorithm satisfies a criterion; and

responsive to said one of said correlation coefficients satisfying said criterion, associating said reference count associated with said common reference point with said second count associated with said common reference point.


  2. The method of claim 1, wherein said criterion is whether said one of said correlation coefficients corresponds to a maximum correlation coefficient produced by said cross-correlation algorithm and wherein said common reference point corresponds to a zero crossing.
  3. The method of claim 2, wherein said cross-correlation algorithm is a circular cross-correlation algorithm, a linear cross-correlation algorithm, or a pattern-matching algorithm.
  4. The method of claim 1, further comprising communicating an instruction to said reference monitoring device to buffer said reference signal data for said predetermined number of cycles and communicating an instruction to said second monitoring device to buffer said second signal data for said predetermined number of cycles.
  5. The method of claim 1, further comprising: providing reference time data; receiving first time data from said reference monitoring device; and responsive to said automatically aligning, synchronizing said first time data with said reference time data such that said common reference point occurs at the same time in said first time data and in said reference time data.
  6. The method of claim 1, further comprising: receiving first time data from said reference monitoring device; receiving second time data from said second monitoring device; responsive to said automatically aligning, synchronizing said first time data with said second time data such that said common reference point occurs at the same time in said first time data and said second time data.
  7. The method of claim 1, further comprising: responsive to said automatically aligning, sampling data at the zero-crossing of a reference channel associated with said reference monitoring device; determining via said computer whether the values of said sampled data are zero, negative, or positive; automatically assigning, via said computer, phase notations based on said determining; and displaying information via said computer representing said phase notations to the user.
  8. The method of claim 7, further comprising alerting said user when at least one of said phase notations is misidentified on a phase conductor.
  9. The method of claim 1, wherein said reference monitoring device and said second monitoring device are meters.
  10. The method of claim 1, wherein said frequency variations represented by said first signal data are variations in fundamental frequency or variations in harmonic frequency, wherein said variations are associated with a voltage or a current.
  11. The method of claim 1, wherein said first signal data represents at least amplitude variations and said second signal data represents at least amplitude variations.
  12. A computer readable medium encoded with instructions which, when said instructions are executed by a computer, cause said computer to perform the method of claim 1.
  13. A power monitoring system (120) for aligning data, comprising:

a system controller (132);

a first monitoring device (128) having a communications interface (140) coupled to said system controller, a memory (138), and a controller (134); and

a second monitoring device (130) having a communications interface (140) coupled to said system controller (132), a memory (138), and a controller (134), wherein said system controller is remote from said first and second monitoring devices, characterised in that said system controller is programmed to communicate an instruction to said first monitoring device and said second monitoring device via their respective communications interfaces to store in their respective memories data representing one or both of frequency variations and amplitude variations in respective current or voltage sensed by said first and second monitoring devices from an electric grid (102) on a cycle-by-cycle basis for a predetermined number of cycles of said respective current or voltage sensed by said first and second monitoring devices, wherein a first count associated with each of said cycles is stored in said memory of said first monitoring device and a second count associated with each of said cycles is stored in said memory of said second monitoring device,
receive from said first monitoring device first data corresponding to said data stored by said first monitoring device in its memory,
receive from said second monitoring device second data corresponding to said data stored by said second monitoring device in its memory, and alig
n said first data with said second data to a common reference point in said respective current or voltage sensed by said first and second monitoring devices by shifting in cycle increments said second data relative to said first data until a maximum cross-correlation coefficient is computed by a cross-correlation function that computes a cross-correlation coefficient at each of said cycle increments and associating said first count associated with said maximum cross-correlation coefficient with said second count associated with said maximum cross-correlation coefficient, and

wherein said controller of said first monitoring device is programmed to
receive said instruction via said communication interface of said first monitoring device,
store said first data in said memory of said first monitoring device for said predetermined number of cycles, and
communicate said first data to said system controller via said communication interface.


  14. The power monitoring system of claim 13, wherein said first monitoring and second monitoring devices are meters.