Importance

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Abstract

Electronic electricity meter, in which the electrical energy consumed by a load is evaluated using a signal indicative of voltage supplied to the load and a signal indicative of load current. The load current signal is derived from an estimated load current value produced by a current transformer (4). The meter includes a memory (9) storing one or more constants from equations indicative of how current transformer phase and ratio errors vary as primary current varies. An adjusted value for the load current is produced by calculating the phase and/or ratio error using the stored constants and the estimated load current value and correcting the estimated load current value to eliminate the error. Alternatively, the meter includes a memory (9) storing a plurality of values of phase error and/or ratio error for a respective plurality of primary current values of the current transformer of predetermined configuration. The estimated load current value is used to select from the storing means (9) a value of phase error and/or ratio error for one of said plurality of primary current values corresponding to the estimated value of primary current. The load current value is corrected using the selected value of phase and/or ratio error.

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First Claim