JP3071309B2 - Electronic watt-hour meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic watt-hour meter for automatically adjusting an error in measured power.

[0002]

2. Description of the Related Art Measurement of an error in an electronic watt-hour meter
A comparison method called RC method is adopted. In this method, as shown in FIG. 2, the power generated from the power generation source 2 is supplied to both the adjusted meter 30 for which the error is to be adjusted and the master meter 3 adjusted by another high-sensitivity measuring device. Is done. Adjusted meter 30 and master meter 3
Measures this power and outputs a proportional pulse and a reference pulse respectively. The weighing pulse from the adjusted meter 30 and the reference pulse from the master meter 3 are respectively used as counters for the adjusted meter of the RC counter 20.
21 and the master meter counter 22 count for a predetermined period. The RC counter 20 displays the respective count values of the adjusted meter counter 21 and the master meter counter 22, and calculates both count display values according to equation (1).
The error of the count display value of the measurement pulse of the adjustment meter 30 with respect to the count display value of the reference pulse of the master meter 3 is calculated.

[0003]

(Equation 1) In this method, the accuracy of the master meter 3 affects the measurement accuracy, but the power generation source 2 does not require high accuracy and stability, and the generated power may vary.

FIG. 3 is a block diagram showing a circuit configuration of the meter 30 to be adjusted. In the figure, the current and voltage components of the power to be measured are converted into signals proportional to the current value and voltage value detected by the current transformer (CT) 31 and the transformer (PT) 32, respectively. The signal from the current transformer 31 and the signal from the transformer 32 via the variable resistor 38 are
The signal is multiplied by a frequency (W / F) converter 33 and converted into a pulse number proportional to the multiplied value. This pulse signal is divided by a frequency divider
After being divided into an appropriate frequency which is easy to count at 34, the frequency is output to the RC counter 20 via an output unit 35, counted by the counter 36, and the counted value is displayed as a measured power value on a display 37. You.

In the case of adjusting the meter to be adjusted 30 configured as described above by the RC method, an error is calculated from the display value of the RC counter 20 after the first error measurement, and the transformer 32 is adjusted based on the error. After manually adjusting the variable resistor 38 connected to the output, an error measurement is performed again to check that the error is within the specified range. If the error is out of the specified range, the adjustment and the error measurement are repeated again to confirm that the error is within the specified range.

[0006]

In the above-described conventional method, since the error is eliminated while manually adjusting the variable resistor, the adjustment takes time and effort, and is inefficient and uneconomical. there were. An object of the present invention is to provide an electronic watt-hour meter capable of automatically and accurately adjusting an error of an electronic watt-hour meter.

[0007]

To achieve the above object, an electronic watt-hour meter according to the present invention comprises a power-frequency conversion means for outputting a frequency signal higher than a frequency corresponding to the power to be measured, a power-frequency conversion means, Difference calculating means for comparing the frequency signal from the converting means and the reference signal to calculate the difference between the two signals, and correcting means for correcting the frequency signal of the power-frequency converting means based on the output signal from the difference calculating means. And a frequency dividing means for dividing the frequency signal corrected by the correcting means.

[0008]

According to the electronic watt-hour meter of the present invention, the power to be measured is supplied to the power-to-frequency conversion means and converted into a frequency higher than the frequency corresponding to the power, and this frequency is compared with the reference frequency to compare the two. Is calculated, and based on the difference,
Since the signal output from the frequency conversion means is corrected, automatic adjustment becomes possible.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an electronic watt-hour meter according to one embodiment of the present invention. The electronic wattmeter shown in FIG. 2 includes the same power generation source 2 and master meter 3 as shown in FIG. 2, and an adjusted meter 1 which is an electronic wattmeter for adjusting an error. The power generated from the power generation source 2 is supplied to both the master meter 3 and the meter 1 to be adjusted. The power source 2 does not require any special precision and stability, and the master meter 3 is adjusted by another high-precision measuring device.

The adjusted meter 1 supplies a current component and a voltage component of the power to be measured from the power generation source 2 to a current transformer (CT) 4 and a transformer (PT) 5, respectively, and the current value and the voltage, respectively. Is converted to a signal proportional to the
It is supplied to a frequency (W / F) converter 6. Although a variable resistor as shown in FIG. 3 is not connected to the output of the transformer 5, the electronic wattmeter does not require adjustment of the variable resistor as in the related art.

The power-frequency converter 6 multiplies a signal proportional to the current value from the current transformer 4 by a signal proportional to the voltage value from the transformer 5, and outputs the output signal having a frequency higher than the corresponding frequency. Correction unit 7 converts to weighing pulse signal
And the correction value calculation unit 11. For example, when the power supplied from the power generation source 2 to the meter 1 is 1 kWh,
When the corresponding frequency is 1 kHz, the frequency of the weighing pulse signal output from the power-frequency (W / F) converter 6 is higher than 1 kHz. Power-frequency converter 6
Is supplied to the frequency dividing unit 8 via the correcting unit 7. The frequency divider 8 divides the signal from the corrector 7 into a signal having a frequency that is easy to count and supplies the signal to the counter 9.
The counter 9 counts the frequency of the signal from the frequency divider 8 and
This counting result is supplied to the display unit 10 and displayed as an electric energy.

On the other hand, the master meter 3 measures the power supplied from the power generation source 2, converts the measured power into a reference pulse signal having a pulse number proportional to the power, and supplies the reference pulse signal to the correction value calculation unit 11 of the meter 1 to be adjusted. I do.

The correction value calculation unit 11 compares the measurement pulse signal supplied from the power-frequency converter 6 of the meter 1 to be adjusted with the reference pulse signal supplied from the master meter 3, and calculates the difference between the two pulse signals, That is, a difference between the number of reference pulse signals of the master meter 3 counted in a predetermined period and the number of measurement pulse signals of the power-frequency converter 6 is calculated. The calculated difference and the number of metering pulse signals of the power-frequency converter 6 counted in the predetermined period are supplied to the correction value storage unit 12 and stored in the correction value storage unit 12. The correction value storage unit
12 is to prevent the stored values from being erased due to power failure, etc.
For example, it is constituted by an EEPROM or the like.

The correction unit 7 calculates a difference between the number of reference pulse signals of the master meter 3 counted in a predetermined period supplied from the correction value storage unit 12 and the number of measurement pulse signals of the power-frequency converter 6, and counts the number of pulses in a predetermined period. The number of pulse signals supplied to the frequency divider is corrected using the number of measurement pulse signals of the power-frequency converter 6 thus obtained. That is, the measurement pulse signal supplied from the power-frequency converter 6 is stored in the correction value storage unit 12.
Counting up to the number of weighing pulse signals supplied from. Also,
Of the weighing pulse signals, the number of weighing pulse signals equal to the difference between the number of reference pulse signals supplied from the correction value storage unit 12 and the number of weighing pulse signals is not supplied to the frequency dividing unit 8, but is counted in the remaining number, that is, during a predetermined period. The number of reference pulse signals of the master meter 3 is supplied to the frequency divider. Note that the correction value storage unit 12 first stores the difference between the number of reference pulse signals of the master meter 3 counted in the predetermined period and the number of measurement pulse signals of the power-frequency converter 6,
In addition, zero is stored in the number of measurement pulse signals of the power-frequency converter 6 counted in the predetermined period, and no correction is performed in this case. Counter 9
Counts the output signal from the frequency divider 8 and displays the count on the display unit 10 as the amount of power.

As described above, since the number of measurement pulse signals of the power-frequency converter 6 is previously set to be greater than the frequency (pulse) signal corresponding to the power, the number of measurement pulse signals is larger or smaller than the number of reference pulse signals. , Either can be automatically adjusted. Although the above embodiment is mainly configured by hardware, it can be similarly configured by replacing it with software.

[0017]

As described above, according to the present invention, the power to be measured is supplied to the power-to-frequency converter to convert it to a frequency higher than the frequency corresponding to the power, and this frequency is compared with the reference frequency. To calculate the difference between the two and correct the output of the power-frequency conversion means based on this difference.
Obtain an electronic watt-hour meter that can be adjusted automatically without manually adjusting the variable resistor as in the past, and that can further reduce adjustment cost and adjustment time and prevent operation errors Can be.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an electronic watt-hour meter of the present invention.

FIG. 2 is a diagram for explaining error adjustment of a conventional electronic watt-hour meter.

FIG. 3 is a configuration diagram of an electronic watt-hour meter showing an example of the meter 30 to be adjusted in FIG. 2;

[Explanation of symbols]

Reference numeral 2: power generation source, 3: master meter, 6: power-frequency (W / F) converter, 7: correction unit, 8: frequency division unit, 11:
Correction value calculation unit, 12... Correction value storage unit.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01R 11/00-11/66 G01R 21/00-22/04

Claims (1)

(57) [Claims] 1. A power-frequency conversion means for outputting a frequency signal higher than a frequency corresponding to the power to be measured, and a frequency signal from the power-frequency conversion means is compared with a reference signal to calculate a difference between the two signals. Difference calculating means, a correcting means for correcting the frequency signal of the power-frequency converting means based on an output signal from the difference calculating means, and a frequency dividing means for dividing the frequency signal corrected by the correcting means. An electronic watt-hour meter having: