RU2252424C2 - Watt-hour meter - Google Patents

Abstract

FIELD: electric instrument engineering.

SUBSTANCE: meter has phase wire current-to-voltage converter, phase wire power-to-frequency converter, zero wire power-to-frequency converter, indication unit and power source. Two magnetically-connected LC circuits are used for galvanic decoupling voltage and current circuits of meter.

EFFECT: reduced phase error of meter; reduced self-consumption of meter.

2 cl, 1 dwg

Description

State of the art

The electromechanical induction electric meters (watt-hours) are widely known, which consist of electromagnetic systems of current and voltage, a movable aluminum disk and a reading device [1]. These counters have fundamental disadvantages:

- rapid wear of the supports, which leads to an increase in the moment of friction and, as a result, underestimation of electricity;

- low accuracy;

- poor protection against theft of electricity;

- large own electricity consumption.

Recently, electronic watt-hour counters are increasingly being used, which consist of measuring converters of voltage and current to an intermediate value (most often voltage or magnetic flux), converters of active power to frequency, single-tariff or multi-tariff readout devices, and transformerless power sources based on capacitor voltage dividers [2]. These meters do not have the first two drawbacks (wear of the poles and low accuracy), but other drawbacks (high own consumption and poor protection against theft of electricity) remain. It is especially difficult to protect electronic meters from theft of electricity through an "artificial zero wire." In this case, an unscrupulous consumer receives unaccounted-for electricity through standard (ordinary) and “artificial zero wire”, which most often uses a water pipe or a central heating battery.

When using a capacitor voltage divider in the power supply, another fundamental drawback of the electronic meter appears - the galvanic connection between the current and voltage circuits. This drawback does not allow for group and, therefore, high-performance metrological certification of meters without additional high-precision voltage transformers.

SUMMARY OF THE INVENTION

The authors propose a new solution, free from the above disadvantages, when implementing watt-hour meters.

The aim of the invention is to create a new watt-hour meter by using two converters (5, 6) of current to voltage, of which one (5) is included in the phase wire of the line under voltage U _a , and the second (6) in the neutral wire, under the potential of the earth.

For galvanic separation of the voltage and current circuits of the meter and reduce its phase error, two magnetically coupled LC circuits are used. Information about the voltage at the load (12) in the form of voltage U _n through a magnetically connected circuit L ₁ C ₁ is fed to the inputs of the power converters (3, 4) in the frequency of the neutral and phase wires, respectively. Each power to frequency converter (3, 4) performs a mathematical operation of multiplying the load voltage by the corresponding current and power factor, followed by a linear conversion of the result of multiplication (i.e., power) into the frequency F _a in the converter (4) and into the frequency F _o in converter (3). Both frequencies F _a and F _o are supplied to a frequency comparison device (7), which in the case of F _a ≥ F _o passes the signal to one output of the device (7), and in the case of F _o > F _a to the other. From the corresponding output of the device (7), the signal enters the controllable frequency divider (9). For the case F _a ≥ F _o, a nominal frequency division coefficient is set in the divider (9). From the output of the controlled frequency divider (9), the signal enters the reading device (10), where electric energy is displayed in a single-tariff or multi-tariff mode.

In the most common case of theft of electricity through an "artificial neutral wire 11", an unscrupulous consumer at the entrance of the object (apartment, house, cottage) swaps the phase and neutral wires and tries to get unaccounted-for energy through a normal neutral wire 0, to which phase voltage U _a is now applied , and "artificial neutral wire 11", which uses a water pipe or central heating battery. In this case, there is no signal from the output of the power converter to the frequency (4), i.e. F _a = 0, and the signal F _o from the output of the converter (3) is, therefore, F _o > F _a . In this case, the signal from the comparison device (7) is supplied to a controlled frequency divider (9) from another output (F _o > F _a ) and is divided in the device (9) in such a way that energy greater than that is taken into account on the reading device (10) that an unscrupulous consumer has stolen. Thus, penalties are automatically imposed on an unscrupulous consumer.

During the operation of the channel F _o > F _{a, the} counter signals the unauthorized receipt of electricity by the fact that the LED (8) lights up and the indication “Prohibition” appears.

The second magnetically coupled circuit L ₂ C _{2 is} used to supply voltage to the stabilized rectifier (1), the output voltage of which U _n supplies the electronic components of the meter.

The use of two magnetically coupled circuits L ₁ C ₁ , L ₂ C ₂ allows, firstly, to galvanically separate the voltage circuit and the counter current circuit, and secondly, to provide resonance at the input of the power source with the circuits L ₁ C ₁ , L ₂ C ₂ (2), which significantly reduces the counter’s own consumption and its phase error.

Literature

1. Ilyukovich A.M. Electric meters (theory, calculation and design), Gosenergoizdat, 1963.

2. A low cost watt-hour energy meter based on the AD 7755 (AN-559).

A.Collins, W.Koon.A Tamper - resistant watt-hour energy meter based on the AD7751 and two current sensors (AN-563).

W.Koon.A Tamper - resistant watt-hour energy meter based on the AD7751 with a current transformer and a low resistant shunt (AN-574).

Firm Analog Devices. World Wide Web Site: http: // www. analog, com.

List of drawing figures

1. The block diagram of the watt-hour meter on one page with the accepted notation:

1 - stabilized rectifier;

2 - power source;

3 - power converter of the neutral wire to the frequency;

4 - power converter phase wire to frequency;

5 - converter of phase wire current into voltage;

6 - converter of the current of the neutral wire to voltage;

7 - a device for comparing frequencies;

8 - LED;

9 - controlled frequency divider;

10 - readout device single-rate or multi-rate;

11 - artificial zero wire;

12 - load;

L ₁ C ₁ , L ₂ C ₂ - magnetically coupled circuits;

U _a - phase wire voltage;

U _n is the supply voltage;

U _H is the voltage at the input of the power converters in the frequency;

F _a is the output frequency of the phase-to-frequency power converter;

F _o - output frequency of the power converter of the neutral wire to the frequency;

0 - zero wire.

Claims (2)

1. The watt-hour meter is single-phase, consisting of a phase-to-voltage current converter, a zero-wire current-voltage converter, a phase-to-frequency power converter, a zero-wire power converter, a frequency comparison device, a controlled frequency divider, single-tariff or multi-tariff readout device and power source, characterized in that each power to frequency converter performs a mathematical operation of multiplying the load voltage by a corresponding th current, the outputs of the power converters of the phase wire and the neutral wire to the frequency are connected to the inputs of the frequency comparison device, the outputs of which are connected to the inputs of the controlled frequency divider, from the output of which the signal is supplied to the reading device, the power source is connected to the voltage circuit through two magnetically coupled LC circuit, while the inductance winding of the first circuit is connected in parallel with the counter voltage circuit, its capacitor is connected to one of the inductance taps, the second LC circuit is connected to the input bilizirovannogo rectifier, and separate winding of the second circuit is connected to the inputs of power converters in the frequency of the phase conductor and the neutral conductor in frequency. 2. The watt-hour meter is single-phase according to claim 1, characterized in that the controllable frequency divider is configured to change the division ratio of the output frequency upward when the output frequency of the zero-wire power converter exceeds the output frequency of the phase-wire power converter.