Automated precision alignment of data in a utility monitoring system
First Claim
1. A method of aligning data measured by monitoring devices coupled to a power monitoring system, comprising:
- receiving, at a controller remote from said monitoring devices, reference signal data from a reference monitoring device, said reference signal data representing at least frequency 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 associated with each of said cycles of current or voltage sensed by said reference monitoring device;
receiving, at said controller, second signal data from at least a second monitoring device, said second signal data representing at least said frequency 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 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 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.
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Abstract
A data alignment algorithm that automatically aligns data from multiple monitoring devices to the same zero-crossings at the same point in time. Cycle-by-cycle frequency data is received from each monitoring device and a cross-correlation algorithm is performed to determine a correlation coefficient between a reference monitoring device and another monitoring device. The data of the other monitoring device is shifted by one cycle and another correlation coefficient is calculated by the cross-correlation algorithm. The data of the two monitoring devices is aligned at the point at which the maximum correlation coefficient is calculated or the point at which the correlation coefficient exceeds a threshold value. The clocks of the monitoring devices can also be synchronized at the same point of alignment.
27 Citations
25 Claims
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1. A method of aligning data measured by monitoring devices coupled to a power monitoring system, comprising:
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receiving, at a controller remote from said monitoring devices, reference signal data from a reference monitoring device, said reference signal data representing at least frequency 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 associated with each of said cycles of current or voltage sensed by said reference monitoring device; receiving, at said controller, second signal data from at least a second monitoring device, said second signal data representing at least said frequency 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 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 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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method of automatically aligning data in a power monitoring system, comprising:
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receiving, at a controller, from a first of at least two monitoring devices first signal data corresponding to signal data stored by said first monitoring device, said first signal data representing frequency or amplitude variations in current or voltage from an electric grid measured by said first monitoring device, said first monitoring device storing a first count associated with each of a plurality of cycles of said current or voltage, said controller being remote from said at least two monitoring devices; receiving, at said controller, from a second of said at least two monitoring devices second signal data corresponding to signal data stored by said second monitoring device, said second signal data representing frequency or amplitude variations in current or voltage from said electric grid measured by said second monitoring device, said second monitoring device storing a second count associated with each of a plurality of cycles of said current or voltage measured by said second monitoring device; and aligning said first signal data with said second signal data to a common reference point in said respective current or voltage sensed by said first and second monitoring devices by shifting in increments said second signal data relative to said first signal data until a maximum cross-correlation coefficient is computed by a cross-correlation function that calculates a cross-correlation coefficient at each of said increments and associating said first count associated with said maximum cross-correlation coefficient with said second count associated with said maximum cross-correlation coefficient. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. A power monitoring system for aligning data, comprising:
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a system controller; a first monitoring device having a communications interface coupled to said system controller, a memory, and a controller; and a second monitoring device having a communications interface coupled to said system controller, a memory, and a controller, wherein said system controller is remote from said first and second monitoring devices, wherein 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 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 align 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. - View Dependent Claims (25)
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Specification