Branch circuit monitor power measurement
First Claim
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1. A method of compensating for a phase error when measuring electricity, said method comprising the steps of:
- (a) sampling an alternating current voltage at a voltage sampling time;
(b) repeating step (a) at a voltage sampling rate;
(c) at a current sampling time, sampling a current, said current sampling time temporally independent of said voltage sampling time; and
(d) determining a phase error compensated voltage corresponding to said current sample, said phase error compensated voltage determined from at least one voltage sample obtained at a time increment offset by a phase error interval from said current sampling time, said phase error interval quantifying a temporal shift of said sampled current relative to said voltage, said temporal shift characteristic of a sensor used to obtain said current sample.
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Abstract
In a digital branch circuit monitor, compensation for the phase error is accomplished by selecting a voltage sampled at a time temporally offset from the sampling time of the current by an interval quantifying the phase shift of the secondary current relative to the primary current that is characteristic of a current transformer.
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Citations
20 Claims
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1. A method of compensating for a phase error when measuring electricity, said method comprising the steps of:
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(a) sampling an alternating current voltage at a voltage sampling time; (b) repeating step (a) at a voltage sampling rate; (c) at a current sampling time, sampling a current, said current sampling time temporally independent of said voltage sampling time; and (d) determining a phase error compensated voltage corresponding to said current sample, said phase error compensated voltage determined from at least one voltage sample obtained at a time increment offset by a phase error interval from said current sampling time, said phase error interval quantifying a temporal shift of said sampled current relative to said voltage, said temporal shift characteristic of a sensor used to obtain said current sample. - View Dependent Claims (2, 3, 4, 5, 6, 7, 9, 10)
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8. A method of measuring power of an alternating current, said method comprising the steps of:
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(a) sampling a voltage of said alternating current at a voltage sampling time; (b) repeating step (a) at a voltage sampling rate; (c) at a current sampling time, sampling a secondary current induced in a current transformer by a primary current, said current sampling time temporally independent of said voltage sampling time; (d) repeating step (c) at a current sampling rate; and (e) computing a product of at least one sample of said current and a magnitude of a voltage sampled at a time temporally offset by a phase error interval from said current sampling time of said at least one sample of said current, said phase error interval quantifying a temporal shift of said secondary current relative to said primary current that is characteristic of said current transformer. - View Dependent Claims (11, 12, 13)
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14. A meter for measuring electricity, said meter comprising:
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(a) a voltage sensor; (b) a current transformer; (c) a memory storing at least one current magnitude and a corresponding phase error interval characteristic of said current transformer, said phase error interval quantifying a temporal shift of said primary current relative to a secondary current induced in said current transformer when one of said primary current and said secondary current is of said current magnitude; and (d) a data processing system for executing at least one program instruction, said program instruction causing said data processing system to; (i) sample an alternating current voltage at said voltage sensor at a voltage sampling time; (ii) repeat step (d) (i) at a voltage sampling rate; (iii) at a current sampling time, sample a secondary current induced in said current sensor, said current sampling time temporally independent of said voltage sampling time; (iv) repeat step (d) (iii) at a current sampling rate; and (v) determine a product of at least one current sample and a voltage measured at a time offset by said phase error interval from said current sampling time. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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Specification