Electricity metering with a current transformer
First Claim
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1. A method for a power meter for measuring a load current in a conductor of said power meter, the method comprising the steps of:
- (a) said power meter determining a phase error correction factor corresponding to a root mean of the square of a load current from a first plurality of sampled currents;
(b) said power meter determining a root mean of the square of a load current from a second plurality of sampled currents;
(c) said power meter computing a phase adjusted root mean of the square load current from said root mean of the square of the load current for said second plurality of sample currents and said phase error correction factor;
(d) said power meter providing an indication of the value of said adjusted load current.
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Abstract
The data storage and processing resources required for an electric meter are reduced by basing the selection and application of phase error correction on a root mean square load current flowing through the meter.
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Citations
17 Claims
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1. A method for a power meter for measuring a load current in a conductor of said power meter, the method comprising the steps of:
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(a) said power meter determining a phase error correction factor corresponding to a root mean of the square of a load current from a first plurality of sampled currents; (b) said power meter determining a root mean of the square of a load current from a second plurality of sampled currents; (c) said power meter computing a phase adjusted root mean of the square load current from said root mean of the square of the load current for said second plurality of sample currents and said phase error correction factor; (d) said power meter providing an indication of the value of said adjusted load current. - View Dependent Claims (7)
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2. A method for a power meter for measuring a load current in a conductor of said power meter, the method comprising the steps of:
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(a) said power meter determining a first root mean of the square load current from a first plurality of sample currents; (b) said power meter determining a second root mean of the square load current from another plurality of sample currents; (c) said power meter determining a phase correction factor corresponding to said first root mean of the square load current; (d) said power meter determining a phase corrected root mean of the square load current from said second root mean of the square load current and said phase correction factor; (e) said power meter providing an indication of the value of said load current. - View Dependent Claims (3, 4, 5, 6)
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8. A method for said power meter of measuring current in an electrical distribution system for a power meter, said method comprising the steps of:
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(a) said power meter periodically sampling a secondary current in a winding of a current transformer; (b) said power meter calculating an assumed load current from said sample secondary current; (c) said power meter repeating steps (a) and (b) for a first plurality of samples of said secondary current; (d) said power meter calculating a first root mean of the square of said assumed load currents from said first plurality of samples; (e) said power meter repeating steps (a) and (b) for a second plurality of samples of said secondary current; (f) said power meter calculating a later root mean of the square of said assumed load currents from said second plurality of samples of secondary current; (g) said power meter determining a phase correction factor corresponding to said first root mean of the square assumed load current, (h) said power meter calculating an adjusted load current from said later root mean of the square assumed load current and said phase correction factor; (j) said power meter providing an indication of the value of said adjusted load current. - View Dependent Claims (9, 10, 11)
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12. A meter for measuring a load current in a conductor of a power meter, the meter comprising:
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(a) a current transformer including a primary winding and a secondary winding, said load current inducing a secondary current in said secondary winding; and (b) a data processing system that; (i) periodically samples said secondary current; (ii) calculates a first root mean of the square of assumed load currents from a first plurality of samples of said secondary current; (iii) determines a phase correction factor corresponding to said first root mean of the square assumed load current; (iv) calculates a second root mean of the square of assumed load currents from a temporally later second plurality of samples of said secondary current; and (v) calculates a phase adjusted load current from said second root mean of the square assumed load current and said phase adjustment factor; (c) said meter providing an indication of the value of said adjusted load current. - View Dependent Claims (13, 14, 15, 16, 17)
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Specification