Electric force measuring device

Abstract

To provide an electric energy measurement device that can measure an electric energy by a simple configuration even if using a current sensor connected to ground and an insulated current sensor.SOLUTION: A single phase three-line type is adapted for the present invention. A shunt resistor SR is a current sensor that is arranged in a distribution line L1, and connected to ground, and a current sensor CS is a current sensor that is arranged in a distribution line L3, and insulated. A voltage detection unit 11 is configured to detect an application voltage with respect to a distribution line L2 as an inter-line voltage V12 with the distribution line L1 as a reference potential, and a voltage detection unit 12 is configured to detect an application voltage with respect to the distribution line L3 as an inter-line voltage V13 with the distribution line L1 as the reference potential, and detect a voltage subtracting the inter-line voltage V12 from the inter-line voltage V13 as an inter-line voltage V23 with respect to the distribution line L2. An electric energy is calculated, using a current each current sensor detects and inter-line voltages V12 and V23.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an electric power measurement device that can perform electric power measurement with a simple configuration even when using a grounded current sensor and an insulated current sensor.

Background Art

[0002] Electric power is calculated using the current and voltage of a distribution line. For example, Patent Document 1 discloses a wattmeter including a voltage measurement unit that continuously measures the voltage of a circuit, a current measurement unit that continuously measures the current of the circuit, and a wattage measurement unit that measures the electric power based on the voltage measurement value obtained by the voltage measurement unit and the current measurement value obtained by the current measurement unit.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, as the current sensor used in the electric power measurement device, an insulated one such as a magnetic sensor is used. Since insulation parts are required for this insulation, the device configuration of the current sensor becomes complicated, and device assembly is not easy. Here, a current sensor using a shunt resistor only has a shunt resistor interposed in the current bar, and the device configuration is simple. However, even a shunt resistor requires insulation parts, and the device configuration becomes complicated. Therefore, if a current sensor using a shunt resistor is grounded, that is, non-insulated, for current measurement, the device configuration becomes simple.

[0005] However, when a current sensor using a shunt resistor is grounded, the distribution line on which the shunt resistor is arranged becomes the reference potential, and there are cases where the line-to-line voltage required for power measurement cannot be measured.

[0006] When insulated current sensors are used, for example, as shown in Figure 6(a), in a single-phase three-wire distribution line, voltage is applied to distribution lines L1 and L3, while the neutral distribution line L2 is connected to ground and no voltage is applied to it. An insulated current sensor CS1 is placed on distribution line L1, and an insulated current sensor CS3 is placed on distribution line L3, and current sensors CS1 and CS3 measure the currents of distribution lines L1 and L3, respectively. Then, a voltage detection unit (not shown) measures the line voltage V21 of distribution line L1 relative to a reference potential and the line voltage V23 of distribution line L3 relative to a reference potential.

[0007] However, when a current sensor using a shunt resistor SR connected to ground is placed on the distribution line L1, as shown in Figure 6(b), the distribution line L1 becomes the reference potential. As a result, the applied voltage on the distribution line L3 is measured as the line voltage V13 with the distribution line L1 as the reference potential, and it is not possible to measure the applied voltage to the neutral line, the distribution line L2, making it impossible to perform accurate power measurement.

[0008] The present invention has been made in view of the above, and aims to provide an energy measuring device that can measure energy with a simple configuration even when using a grounded current sensor and an isolated current sensor. [Means for solving the problem]

[0009] To solve the above-mentioned problems and achieve the objective, the present invention provides an energy measuring device that measures energy by providing a first current sensor and a second current sensor to a first distribution line and a second distribution line, respectively, which are excluding the third distribution line corresponding to the neutral line in a single-phase three-wire power supply system, wherein the first current sensor is connected to ground and measures the first current of the first distribution line, the second current sensor is insulated and measures the second current of the second distribution line, and the first distribution line is used as the reference potential to apply a first applied voltage to the third distribution line to the third distribution line. The device is characterized by comprising: a first voltage detection unit that detects a line voltage of 1; a second voltage detection unit that detects a second applied voltage to the second distribution line, calculates a third applied voltage by subtracting the first applied voltage from the second applied voltage, and detects the third applied voltage as the second line voltage to the third distribution line; and an energy calculation unit that calculates a first energy amount based on the first current and the first line voltage, calculates a second energy amount based on the second current and the second line voltage, and calculates a total energy amount by adding the first energy amount and the second energy amount.

[0010] Furthermore, the present invention relates to an energy measuring device that measures energy by providing a first current sensor and a second current sensor to a first distribution line and a second distribution line, respectively, which are other than the third distribution line corresponding to the neutral line in a single-phase three-wire power supply system, wherein the first current sensor is connected to ground and measures the first current of the first distribution line, the second current sensor is insulated and measures the second current of the second distribution line, and the first voltage detection unit detects the first applied voltage to the third distribution line as the first line voltage to the third distribution line, with the first distribution line as the reference potential, and the first The device is characterized by comprising: a second voltage detection unit that detects a second applied voltage to the second distribution line using the distribution line as a reference potential; an arithmetic processing unit that calculates a third applied voltage by subtracting the first applied voltage from the second applied voltage detected by the second voltage detection unit, and outputs the third applied voltage as the second line voltage to the third distribution line; and an energy calculation unit that calculates a first energy amount based on the first current and the first line voltage, calculates a second energy amount based on the second current and the second line voltage, and calculates a total energy amount by adding the first energy amount and the second energy amount.

[0011] Furthermore, the present invention is characterized in that, in the above invention, the first current sensor is a current sensor using a shunt resistor.

[0012] Furthermore, the present invention is characterized in that, in the above invention, a three-phase three-wire system is used in which voltage is applied to the third distribution line to supply power, and the amount of energy is measured by a two-power meter method using the first current and the first line voltage, and the second current and the second line voltage.

[0013] Furthermore, the present invention relates to an energy measuring device that measures energy by providing a first current sensor, a second current sensor, and a third current sensor to the first, second, and third distribution lines, respectively, of a three-phase four-wire power supply system, excluding the fourth distribution line corresponding to the neutral line, wherein the first current sensor is connected to ground and measures the first current of the first distribution line, the second current sensor and the third current sensor are insulated and measure the second current of the second distribution line and the third current of the third distribution line, respectively, and includes a first voltage detection unit that detects the first applied voltage to the fourth distribution line as the first applied voltage to the fourth distribution line with the first distribution line as the reference potential, and a second voltage detection unit that detects the second applied voltage to the second distribution line as the second applied voltage to the first distribution line with the first distribution line as the reference potential. The power calculation unit comprises: a voltage detection unit; a third voltage detection unit that detects a third applied voltage to the third distribution line as the third applied voltage to the first distribution line, using the first distribution line as the reference potential; a voltage obtained by changing the sign of the first applied voltage as the first line voltage of the first distribution line with the fourth distribution line as the reference potential; a value obtained by subtracting the first line voltage from the second applied voltage as the second line voltage of the second distribution line with the fourth distribution line as the reference potential; a value obtained by subtracting the first line voltage from the third applied voltage as the third line voltage of the third distribution line with the fourth distribution line as the reference potential; and a power calculation unit that calculates the total power based on the first current and the first line voltage, the second current and the second line voltage, and the third current and the third line voltage. [Effects of the Invention]

[0014] According to the present invention, energy measurement can be performed with a simple configuration even when using a grounded current sensor and an isolated current sensor. [Brief explanation of the drawing]

[0015] [Figure 1] Figure 1 is an explanatory diagram illustrating the concept of voltage detection in an energy measuring device according to an embodiment of the present invention. [Figure 2] Figure 2 is a schematic diagram showing the configuration of an energy measurement device according to an embodiment of the present invention. [Figure 3] Figure 3 is a schematic diagram showing the configuration of an energy measuring device, which is a modified embodiment of the present invention. [Figure 4] Figure 4 is an explanatory diagram illustrating the concept of voltage detection using a three-phase, three-wire system. [Figure 5] Figure 5 is an explanatory diagram illustrating the concept of voltage detection using a three-phase four-wire system. [Figure 6] Figure 6 is an explanatory diagram illustrating voltage detection using a conventional single-phase three-wire system. [Modes for carrying out the invention]

[0016] Hereinafter, embodiments for carrying out this invention will be described with reference to the attached drawings.

[0017] Figure 1 is an explanatory diagram illustrating the concept of voltage detection in an energy measuring device according to an embodiment of the present invention. In Figure 1, a single-phase three-wire system is used, and energy measurement is performed by installing shunt resistors SR and current sensors CS, respectively, on distribution lines L1 and L3, which are not the neutral distribution line L2, among the distribution lines supplying power from power source SP. The current sensor using shunt resistor SR is connected to ground and measures the current of distribution line L1. The current sensor CS is insulated and measures the current of distribution line L3.

[0018] Here, since the current sensor using the shunt resistor SR is grounded, the potential P1 of the power distribution line L1 becomes the reference potential. The power distribution line L2 functions as a neutral line and no voltage is applied. The line voltage V12 between the power distribution line L1 and the power distribution line L2 is measured with the potential P1 of the power distribution line L1 as the reference potential. Here, the line voltage V23 between the power distribution line L2 and the power distribution line L3 cannot be directly measured, but since the line voltage V13 between the power distribution line L1 and the power distribution line L3 can be directly measured, the value obtained by subtracting the line voltage V12 from the line voltage V13 is measured as the line voltage V23. Thereby, the amount of power supplied to the power distribution lines L1 and L3 can be calculated.

[0019] FIG. 2 is a schematic diagram showing the configuration of the power amount measuring device 1 according to an embodiment of the present invention. This power amount measuring device 1 measures the power supplied in a single-phase three-wire system, similar to that shown in FIG. 1. The voltage detection unit 11 receives the reference potential which is the potential P1 of the power distribution line L1, and the applied voltage P12 on the P1 side of the power distribution line L1 via the wiring L12 from the midpoint potential of the resistors R1 and R2. The voltage detection unit 11 subtracts the reference potential from the applied voltage P12 on the P1 side by the differential amplifier 13, calculates the differential voltage of the applied voltage P12 on the P1 side with respect to the reference potential, and outputs this differential voltage as the line voltage V12.

[0020] On the other hand, the voltage detection unit 12 receives the applied voltage P12 on the P1 side via the wiring L4 connected to the wiring L12, and the applied voltage P13 on the P3 side of the power distribution line L3 via the wiring L23 from the midpoint potential of the resistors R3 and R4. The voltage detection unit 12 subtracts the applied voltage P12 on the P1 side from the applied voltage P13 on the P3 side by the differential amplifier 14, calculates the differential voltage of the applied voltage P13 on the P3 side with respect to the applied voltage P12 on the P1 side, and outputs this differential voltage as the line voltage V23.

[0021] The current detection unit 21 detects the current flowing through the power distribution line L1 using the shunt resistor SR. The current detection unit 21 measures the potential difference across both ends of the shunt resistor SR, and divides this potential difference by the resistance value of the shunt resistor SR to detect the current. The current detection unit 22 detects the current flowing through the power distribution line L3 using the current sensor CS. For example, when the current sensor CS is a magnetic sensor, the current detection unit 22 inputs the induced voltage induced by the current flowing through the power distribution line L3, and detects the output voltage corresponding to this induced voltage as the current flowing through the power distribution line L3.

[0022] The electric energy calculation unit 30 calculates the electric energy supplied to the power distribution line L1 using the current output by the current detection unit 21 and the line voltage V12 output by the voltage detection unit 11, calculates the electric energy supplied to the power distribution line L3 using the current output by the current detection unit 22 and the line voltage V23 output by the voltage detection unit 12, adds these electric energies, calculates the total electric energy in a single-phase three-wire system, and outputs it from the output terminal T.

[0023] In this embodiment, since the current sensor connected to the ground can be arranged to calculate the electric energy, there is no need to provide an insulating component for the current sensor, and the configuration of the electric energy measuring device 1 becomes simple. Note that the current sensor connected to the ground may be arranged on the power distribution line L3 side as well.

[0024] <Modification Example> FIG. 3 is a schematic diagram showing the configuration of an electric energy measuring device 2 which is a modification example of the embodiment of the present invention. In this modification example, instead of the P1-side applied voltage P12, the reference potential which is the potential P1 of the power distribution line L1 is input to the differential amplifier 14 via the wiring L5 in the voltage detection unit 12. Then, the differential amplifier 14 subtracts the reference potential which is the potential P1 of the power distribution line L1 from the P3-side applied voltage P13, and outputs the P3-side applied voltage P13 with respect to this reference potential as the line voltage V13. On the other hand, the voltage detection unit 11 is the same as in the embodiment, and outputs the P1-side applied voltage P12 with respect to the reference potential as the line voltage V12.

[0025] The arithmetic processing unit 15 then subtracts the line voltage V12 output by the voltage detection unit 11 from the line voltage V13 output by the voltage detection unit 12, and outputs this subtraction result as the line voltage V23 of the distribution line L3 relative to the distribution line L2. The arithmetic processing unit 15 then outputs the line voltage V12 output by the voltage detection unit 11 and the calculated line voltage V23 to the energy calculation unit 30.

[0026] The power calculation unit 30, similar to the embodiment, calculates the amount of power supplied to the distribution line L1 using the current output by the current detection unit 21 and the line voltage V12 output by the calculation processing unit 15, calculates the amount of power supplied to the distribution line L3 using the current output by the current detection unit 22 and the line voltage V23 output by the calculation processing unit 15, adds these amounts of power to calculate the total power for the single-phase three-wire system, and outputs it from the output terminal T.

[0027] In the above embodiment, the voltage detection units 11 and 12, which are hardware components, calculated the line voltages V12 and V23, respectively. In this modified example, the voltage detection units 11 and 12, which are hardware components, output the line voltages V12 and V13, respectively. Then, the calculation processing unit 15, which is software component, calculates the line voltage V23 by subtracting the line voltage V12 from the line voltage V13. The calculation processing unit 15 then outputs the line voltages V12 and V23 to the energy calculation unit 30.

[0028] Although the above embodiments and modifications describe an energy measurement device for single-phase three-wire power lines, the invention is not limited to this and can also be applied to energy measurement devices for three-phase three-wire power lines.

[0029] In a single-phase three-wire system, no voltage is applied to the distribution line L2, but in a three-phase three-wire system, voltage is applied to the distribution line L2. In power measurement in a three-phase three-wire system, the amount of energy can be measured by determining the line voltages V12 and V23. That is, the energy calculation unit 30 can measure the amount of energy using the two-wattmeter method, using the current output by the current detection unit 21, the line voltage V12 output by the voltage detection unit 11, the current output by the current detection unit 22, and the line voltage V23 output by the voltage detection unit 12.

[0030] Figure 4 is an explanatory diagram illustrating the concept of voltage detection using a three-phase, three-wire system. As shown in Figure 4(a), conventionally, it was possible to directly detect the line voltage V21 relative to the potential P1 of distribution line L1 and the line voltage V23 relative to the potential P3 of distribution line L3, using the potential P2 of distribution line L2 as a reference. However, as shown in Figure 4(b), when a ground-connected current sensor is placed on distribution line L1, the potential P1 of distribution line L1 becomes the reference potential, making it impossible to directly determine the line voltage V23 between the potential P2 of distribution line L2 and the potential P3 of distribution line L3.

[0031] Therefore, in a three-phase three-wire system, just like in a single-phase three-wire system, the line voltage V23 can be obtained by subtracting the line voltage V12 (voltage applied to P1 side P12) from the line voltage V13 (voltage applied to P3 side P13).

[0032] Furthermore, the above embodiments and modifications can also be applied to a three-phase four-wire system. In a three-phase four-wire system, a first current sensor, a second current sensor, and a third current sensor are provided on the first, second, and third distribution lines, respectively, of the distribution lines that supply power, excluding the fourth distribution line corresponding to the neutral line, to measure energy consumption. In this three-phase four-wire energy consumption measuring device, the first current sensor is connected to ground and measures the first current of the first distribution line, while the second and third current sensors are insulated and measure the second current of the second distribution line and the third current of the third distribution line, respectively.

[0033] On the other hand, with respect to voltage, the system includes a first voltage detection unit that detects a first applied voltage to a fourth distribution line as the first applied voltage to the fourth distribution line, using the first distribution line as the reference potential; a second voltage detection unit that detects a second applied voltage to a second distribution line as the second applied voltage to the first distribution line, using the first distribution line as the reference potential; and a third voltage detection unit that detects a third applied voltage to a third distribution line as the third applied voltage to the first distribution line, using the first distribution line as the reference potential. Furthermore, the system includes an energy calculation unit that calculates the total energy based on the first current and the first line voltage, the second current and the second line voltage, and the third current and the third line voltage, by subtracting the first line voltage from the second applied voltage as the first line voltage of the first distribution line with the fourth distribution line as the reference potential, by subtracting the first line voltage from the second applied voltage as the second line voltage of the second distribution line with the fourth distribution line as the reference potential, and by subtracting the first line voltage from the third applied voltage as the third line voltage of the third distribution line with the fourth distribution line as the reference potential.

[0034] Figure 5 is an explanatory diagram illustrating the concept of voltage detection using a three-phase four-wire system. As shown in Figure 5(a), conventionally, it was possible to directly detect the line voltage V01 relative to the potential P1 of the first distribution line, the line voltage V02 relative to the potential P2 of the second distribution line, and the line voltage V03 relative to the potential P3 of the third distribution line, using the potential P0 of the fourth distribution line as a reference. However, as shown in Figure 5(b), when a ground-connected current sensor is placed on the first distribution line, the potential P1 of the first distribution line becomes the reference potential, making it impossible to directly determine the line voltages V02 and V03 between the potential P2 of the second distribution line and the potential P3 of the third distribution line.

[0035] Therefore, in a three-phase four-wire system, line voltages V02 and V03 can be determined in the same way as in a three-phase three-wire system. First, the line voltage V01 of the first distribution line (potential P1) with the fourth distribution line as the reference potential is obtained as the voltage obtained by changing the sign of the line voltage V10 of the line voltage at potential P0 with potential P1 as the reference potential. Next, the line voltage V02 of the second distribution line (potential P2) with the fourth distribution line as the reference potential is obtained by subtracting the line voltage V10 from the line voltage V12 of the second distribution line (potential P2) with the fourth distribution line as the reference potential. Furthermore, the line voltage V03 of the third distribution line (potential P3) with the fourth distribution line as the reference potential is obtained by subtracting the line voltage V10 from the line voltage V13 of the third distribution line (potential P3) with the fourth distribution line as the reference potential.

[0036] It should be noted that the configurations illustrated in the above embodiments and modifications are functionally schematic and do not necessarily have to be physically represented as shown. In other words, the forms of distribution and integration of each device and component are not limited to those shown, and all or part of them can be functionally or physically distributed and integrated in any unit according to various usage situations. [Explanation of Symbols]

[0037] 1,2 Electric energy measuring device 11,12 Voltage detection unit 13,14 Differential amplifier 15. Arithmetic Processing Unit 21,22 Current detection unit 30 Electric energy calculation section CS,CS1,CS3 Current sensor L1~L3 distribution line L4, L5, L12, L23 wiring P1~P3 potential P12 P1 side applied voltage P13 P3 applied voltage R1~R4 resistance SP power supply SR shunt resistor T output terminal V01, V02, V03, V12, V10, V13, V23 Line voltage

Claims

[Claim 1] An energy measuring device that measures energy consumption by providing a first current sensor, a second current sensor, and a third current sensor, respectively, on the first, second, and third distribution lines, excluding the fourth distribution line corresponding to the neutral wire, in a distribution line that supplies power in a three-phase four-wire system, The first current sensor is connected to ground and measures the first current of the first power distribution line. The second current sensor and the third current sensor are insulated and measure the second current of the second power distribution line and the third current of the third power distribution line, respectively. A first voltage detection unit that uses the first distribution line as a reference potential and detects the first applied voltage to the fourth distribution line as the first applied voltage to the fourth distribution line, A second voltage detection unit that uses the first distribution line as a reference potential and detects the second applied voltage to the second distribution line as the second applied voltage to the first distribution line, A third voltage detection unit that uses the first distribution line as a reference potential and detects the third applied voltage to the third distribution line as the third applied voltage to the first distribution line, A power calculation unit calculates the total power based on the first current and the first line voltage, the second current and the second line voltage, and the third current and the third line voltage, by subtracting the first line voltage from the second applied voltage as the first line voltage of the first distribution line with the fourth distribution line as the reference potential, by subtracting the first line voltage from the second applied voltage as the second line voltage of the second distribution line with the fourth distribution line as the reference potential, by subtracting the first line voltage from the third applied voltage as the third line voltage of the third distribution line with the fourth distribution line as the reference potential, and by subtracting the first line voltage from the third applied voltage as the third line voltage of the third distribution line with the fourth distribution line as the reference potential, An energy measuring device characterized by being equipped with the following features.

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