US 5,059,896 AGranted

Electronic watthour meter

AssigneeGeneral Electric Company

InventorsWarren R. Germer, Maurice J. Ouellette, Mehrdad N. Hagh, Bertram White

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Abstract

An electronic watthour meter is digitally configurable to operate as several different types of watthour meters for metering electrical energy from a variety of different electric utility services. Automatic scaling of line input currents is provided to scale the voltage input to an analog to digital converter over selected ranges such that low level and high level input signals are measured in an optimum range. A digital signal processor is employed to calculate values for metered electrical energy and output pulses, each proportional to a quantum of energy flowing in the circuit being metered. The processor calculates the value of DC offset errors inherent in the various analog circuits of the meter and uses that value in the calculation of metered electrical energy to compensate for such offset errors. The meter employs automatic and manually initiated test functions for testing the operation of the processor and other critical circuits in the meter.

Claims16

Dependent claims

A meter, comprising:

(a) means for processing current and voltage values proportional to current and voltage samples from conductor means;
(b) converter means for providing, to said processing means, the current value proportional to samples of current flowing in the conductor means and the voltage value proportional to the voltage of the conductor means;
(c) multiplexer means for providing, to said converter means, samples of an analog signal proportional to current from the conductor means and samples of an analog signal proportional to voltage from the conductor means;
and
(d) type select means for selectively configuring said meter as one of a plurality of types of meter configurations, said select type means comprising,
(i) first clock means for providing, to said multiplexer means, a plurality of first clock signals to selectively effect the transfer, into said converter means, of current samples from the conductor means in accordance with a selected type of meter configuration;
(ii) second clock means for providing, to said multiplexer means, a plurality of second clock signals to selectively control the sequence of sampling voltage on the conductor means to selectively effect the transfer of voltage samples into said converter means, the sequence of sampling voltage, and the transferring thereof, being in accordance with the type of meter configuration selected.

4 more elements

A method of operating a meter to generate a measurement of reactive energy, the meter comprising converter means for converting analog signals proportional to current flow in, and voltage across conductor means to current and voltage words respectively having values proportional to the instantaneous magnitudes of the samples current and voltage, said method comprising the steps of:

(a) sampling, repetitively, current and voltage words from said converter means;
(b) placing, at prescribed intervals at the time of sampling, a voltage word in delay means;
(c) checking the output of the delay means at each sampling;
(d) increasing the value of integrator means by a value proportional to the product of the last sampled current word and a delayed voltage word from the delay means;
(e) comparing the present value of the integrator means with a prescribed threshold value, the prescribed threshold value being determined based on a pre-selected meter configuration;
(f) repeating steps (b) through (e) until the value of the integrator means is at least equal to the prescribed threshold value;
and
(g) generating a pulse representative of a quantum measurement of reactive energy, the quantum of measurement being a function of time that it takes a voltage word to pass from its input to its output.

5 more elements

A type select means for a meter, the meter comprising processing means for processing current and voltage values proportional to current and voltage samples from conductor means, and sampling means for providing, to said processing means, the current value proportional to samples of current flowing in the conductor means and the voltage value proportional to the voltage of the conductor means, said type select means comprising:

first clock means for providing, to said sampling means, a plurality of first clock signals to selectively effect the transfer of current samples from the conductor means in accordance with a selected type of meter configuration;
and
second clock means for providing, to said sampling means, a plurality of second clock signals to selectively control the sequence of sampling voltage on the conductor means to selectively effect the transfer of voltage samples in accordance with the type of meter configuration selected.

Dependencies are inferred from the claim text.