JP4448080B2 - Current measuring device - Google Patents

Description

The present invention relates to a large number of wires put that current measuring device in between the distribution board such as a cabinet, enclosure closed to form a branch circuit.

  The current measurement method for the current flowing through the electric wire or power cable is provided with a current sensor in which a coil is wound around a ring-shaped core so as to form a closed magnetic circuit in order to eliminate leakage of magnetic flux generated by current flow A so-called electromagnetic induction method is generally used in which a current transformed from a current sensor is taken in and converted.

  On the other hand, regardless of the electromagnetic induction method, the current that flows through the circuit to be measured is converted into a light amount, the light amount is emitted remotely, the received light amount is converted into an electrical amount, and the current value is accurately reproduced by performing temperature correction. A measuring device is disclosed in Patent Document 1.

  In addition, the current is not directly measured, but based on the difference between the temperature of the fluid before the electrical energy loss is transmitted to the heat energy to the electrical component and the temperature of the fluid after the transmission, A measuring device that converts heat energy is disclosed in Patent Document 2.

JP-A-10-19911 JP 2001-238301 A (paragraph numbers [0024], [0028] to [0044]

However, a current sensor using an electromagnetic induction method, in particular, a penetrating CT, requires that an electric wire be passed through a ring-shaped core, and the electric current sensor itself has a large size and shape, and the electric wire forming the branch circuit is not suitable. In order to store and install in a concentrated distribution board, etc., space constraints have mainly arisen.
As a result, the burden of installation work is large and the cost is high, and the current sensor cannot be stored in a distribution board or the like, and current measurement may not be possible for each branch circuit.

  Similarly, a measuring device that forms a circuit such as an optical cable and a light-emitting diode to convert a current into a light amount, or a measuring device that draws a pipe and converts it from heat energy using a fluid as a medium, has an electric wire that forms a branch circuit. It was impossible to install it in a cabinet or housing such as a concentrated distribution board.

  In addition, when performing energy saving, energy management, air conditioning control, etc., it is necessary to acquire current data from a number of locations in the building electrical equipment. Therefore, when measuring up to a branch circuit in a multi-branch circuit such as a distribution board, it has conventionally been necessary to attach a current sensor (such as CT) to all of them.

  However, when current management is performed by installing a plurality of conventional through-type CTs, since the installation is restricted by the shape and the measurement target wires and power cables need to penetrate the CT, the CT is increased. The shortage of the arrangement space, the increase of the cost, and the increase of the construction burden became so remarkable that it was not preferable.

Accordingly, the present invention has been made to solve the above-described problems, and its purpose is to reduce the size of the sensor itself and simplify the construction in a closed space in a cabinet / housing such as a distribution board forming a branch circuit. measure of, certain of all current supplied to the respective branch circuits to provide a current measurable and to that current measuring device at a low cost.

A current measuring apparatus according to claim 1 of the present invention includes a coated surface thermometer that measures a surface temperature value of a cable sheath to be energized, an environmental thermometer that acquires an environmental temperature value near the cable, these coated surface thermometers, An arithmetic processing unit connected to communicate with an environmental thermometer, and a current transformer that measures a current flowing through the cable before branching on the input side, wherein the arithmetic processing unit is a cable before branching on the input side For each of the environmental temperature values, a prediction formula which is a polynomial based on a surface temperature rise value obtained by subtracting the environmental temperature value from the surface temperature values of the cables after the branching on the output side is used for each environmental temperature value. A plurality of registration means for registering, an acquisition means for acquiring the surface temperature value and the environmental temperature value, a reading means for reading out a prediction formula corresponding to the acquired environmental temperature value from a plurality of prediction formulas; Calculating means for calculating a predicted current value by substituting the surface temperature rise value with respect to the prediction equation, and characterized in that it functions by.

The current measuring device according to claim 2 of the present invention is the current measuring device according to claim 1, wherein the plurality of branched cables on the output side are measured by the current transformer based on the temperature by the coated surface thermometer. The estimated current value is obtained by appropriately dividing the current value .

The current measuring device according to claim 3 of the present invention, the current measuring apparatus according to claim 1 or claim 2, wherein the coated surface thermometer, a temperature measurement function unit for measuring the surface temperature values, measured A correction value setting function unit that corrects the surface temperature value, a communication function unit that performs communication via a communication line, and a fixing unit that tightly fixes and fixes the installation surface of the temperature measurement function unit and the covering surface of the cable, The surface temperature value is transmitted via a communication line .

The current measuring device according to claim 4 of the present invention is the current measuring device according to claim 3, wherein the fixing means is a heat conduction that tightly fixes the installation surface of the covering surface thermometer and the covering surface of the cable. and sex material, characterized the sealing layer covering a thermometer, and an adhesive portion that covers the sealing layer, the means der Rukoto by.

The current measuring device according to claim 5 of the present invention is the current measuring device according to claim 3 or 4, wherein the temperature measuring function unit, the correction value setting function unit, and the communication function unit are housed in a case. A packaged surface thermometer integrated by forming a package is characterized.

  According to the present invention, heat that has a correlation with the energization current of the electric wire or power cable is selected as a medium, and a relatively small temperature sensor is provided in place of the large current sensor. In a closed space in cabinets and cabinets such as panels, the sensor itself is downsized and construction is simplified, and a current measurement method and current measurement device that can measure all currents flowing through each branch circuit at low cost are provided. can do.

Hereinafter, the current measurement method and the current measurement device of the embodiment of the present invention will be described collectively. FIG. 1 is a configuration diagram of a current measuring apparatus according to the present embodiment, and FIG. 2 is an internal configuration diagram of a thermometer.
The current measuring device 10 includes a coated surface thermometer 20, an environmental thermometer 30, a bus cable 40, and an arithmetic processing unit 50. An arithmetic processing unit 50 is connected to a bus cable 40 which is a one-line bus to which a plurality of (two in FIG. 1) coated surface thermometers 20 and one or a plurality of (one in FIG. 1) environmental thermometers 30 are connected. The arithmetic processing unit 50 is connected and communicates with the covering surface thermometer 20 and the environmental thermometer 30 to calculate a current from the temperature.

Although the above-mentioned covering surface thermometer 20 and environmental thermometer 30 have different names, they have the same configuration and have a function of being connected to the bus cable 40 for communication. Next, details of the coated surface thermometer 20 and the environmental thermometer 30 will be described.
As shown in FIG. 2, the coated surface thermometer 20 and the environmental thermometer 30 include a temperature measurement function unit 21 (31), a correction value setting function unit 22 (32), a communication function unit 23 (33), and a connector unit 24 (34). ).

  Specifically, the temperature measurement function unit 21 (31) includes a semiconductor thermocouple. This semiconductor thermocouple detects temperature using a phenomenon in which an electromotive force is generated by carrier movement due to a temperature gradient in the semiconductor. By adopting such a semiconductor thermocouple, a minute temperature change of the measurement target can be measured. Then, the temperature measurement value that is an analog signal is A / D converted to a temperature measurement value that is digital data and output.

  The correction value setting function unit 22 (32) has a function of adding a preset correction value to the measured temperature measurement value. Such a correction function, for example, produces an error by comparing the surface temperature (or environmental temperature) from the temperature measurement function unit 21 (31) with the surface temperature (or environmental temperature) measured by another device. In this case, a correction value that is digital data for correcting an error is registered in advance in the correction value setting function unit 22 (32), and thereafter, the temperature that is digital data output from the temperature measurement function unit 21 (31). A predetermined correction value, which is digital data, is added to or subtracted from the measured value and output as an accurate surface temperature value (environment temperature value).

The communication function unit 23 (33) converts the surface temperature value (environment temperature value), which is digital data, into signal data for communication and transmits the data. This data is transmitted to the arithmetic processing unit 50 via the external connector unit 24 (34).
The temperature measurement function unit 21 (31), the correction value setting function unit 22 (32), and the communication function unit 23 (33) are packaged in a flat plate with a resin or the like provided with an external connector unit 24 (34). The covering surface thermometer 20 and the environmental thermometer 30 are formed by integrating in a resin case or a metal case. Such integration has an advantage that the coated surface thermometer 20 and the environmental thermometer 30 can be easily handled, or can be used even under severe environments such as moisture.

In such a current measuring device 10, the bus cable 40 which is a one-wire bus is used, but the communication method is, for example, a communication method using a micro LAN.
Micro LAN is a communication system developed by Dallas Semiconductor. For the covering surface thermometer 20 and the environmental thermometer 30, ID data is registered in the communication function unit 23 (33) for identification. When the arithmetic processing unit 50 transmits the ID data on the bus cable 40, the coated surface thermometer 20 (or the environmental thermometer 30) matching the ID data starts communication, and the arithmetic processing unit 50 receives the data. Finally, the surface temperature value (environment temperature value) is acquired. Further, the surface temperature values (environment temperature values) at a plurality of locations are aggregated through a communication line, and current measurement as described later is performed.

Subsequently, current measurement by such a current measuring device will be described. First, initial calibration is performed. This initial calibration will be described with reference to the drawings. FIG. 3 is an explanatory diagram of initial calibration by the current measuring device, and FIG. 4 is an explanatory diagram of a prediction formula.
A prediction formula is generated to measure a current value as an initial calibration. As a fluctuation factor of the prediction formula, surface temperature and environmental temperature having a correlation with the current value can be considered. Since the environmental temperature is easily affected by external factors (outside temperature, air volume, etc.), it differs depending on the installation position of the sensor, and accurate measurement is usually difficult. However, in the present invention, it is assumed to be placed in a closed space where the temperature hardly changes in the same cabinet or casing such as a distribution board, and it is considered that there is no temperature difference in the closed space, What is necessary is just to acquire environmental temperature.

  As shown in FIG. 3, the variable current power source 1 and the load 2 are electrically connected to a cable 1000 prepared for calibration, and the covering surface thermometer 20 is attached to the cable 1000 in close contact. Prepare the same type of cable as the actual measurement cable. Specifically, it is a VCT (vinyl cabtyre) cable. The VCT cable is a vinyl chloride electric wire for wiring, and can be used even in harsh environments such as outdoors. In the close contact of the coated surface thermometer 20, it is preferable that the coated surface thermometer 20 and the cable 1000 are attached with a heat conductive substance (for example, silicone resin) interposed therebetween. Thereby, the surface temperature of the cable 1000 is efficiently thermally conducted to the temperature measurement function unit 11 in the thermometer 10.

Furthermore, it is preferable to form a seal layer for blocking the temperature from the outside for fixing the coated surface thermometer 20. The seal layer is not particularly limited as long as it has stable physical properties such as polyethylene, cross-linked polyethylene, vinyl chloride, EP rubber, chloroprene rubber, etc., sponge, vinyl, etc. It is desirable to use the same material as the covering layer of the cable 1000 to be used. Further, the sealing layer may be fixedly held on the wiring cable using a fastening band such as an insulating lock made of heat insulating resin or an adhesive. In addition, a heat-shrinkable heat insulating tube having good workability in manufacturing may be used as the sealing layer to maintain the heat insulating performance of the connecting portion.
Such a coated surface thermometer 20 is installed on the cable 1000.
Further, an air conditioner 3 capable of setting the temperature of the entire closed space is installed around the environment thermometer 30.

Next, prediction formula generation will be described.
First, the air conditioner 3 is operated to set the environmental temperature to a predetermined temperature. Further, the variable current power source 1 is operated to pass a current through the cable 1000. At the time of calibration, the surface temperature value of the cable covering surface when no current is flowing through the cable 1000 matches the environmental temperature value. Therefore, this covering temperature value may be used as the environmental temperature value. Temperature measurement is performed under such circumstances. The arithmetic processing unit 50 acquires an environmental temperature value. This environmental temperature value is also the surface temperature value of the cable 1000 in which no current flows. The arithmetic processing unit 50 transmits ID data for specifying the coated surface thermometer 20 to the bus cable 40. The coated surface thermometer 20 that matches the ID data outputs communication data including the surface temperature value, and acquires the surface temperature value at a certain energization current value I _i . Then, a surface temperature increase value T [i] obtained by subtracting the environmental temperature value from the surface temperature value is acquired. Thereafter, the energizing current value I _i is increased by a predetermined step amount (for example, alternating current and the amplitude is 1 ampere) to obtain surface temperature values corresponding to different currents I _i by collecting data and subtracting the environmental temperature. Many surface rising temperature values T _i are obtained. Finally, a prediction formula such as the following formula is generated by using the obtained data of I _i and T _i .

(Equation 1)
I = aT ² + bT + c

The constants a, b, and c are determined by the least square method using a lot of data called I _i and T _i . As shown in FIG. 4, such a prediction formula is such that the energization current value increases as the surface temperature increase value increases, and a correlation between the temperature increase and the current increase has been confirmed. Thus, the prediction equation at a certain environmental temperature T _A is obtained. Subsequently, the environmental temperature value is changed from T _A to T _B to obtain a similar prediction formula. In this way, a plurality of prediction formulas corresponding to a large number of environmental temperature values are registered in advance.

  Subsequently, current measurement using such a current measurement device 10 will be described. For the sake of concrete explanation, the case where it is installed in the cabinet 100 will be described. FIG. 5 is an explanatory diagram of the cabinet, and FIG. 6 is an explanatory diagram of the arrangement of the current measuring device 10. A power supply built-in switch 300, a three-circuit switch 400, a mold discon 500, and a UGS (Ground switch for gas distribution) 600 are connected to the mold bus 200 disposed in the cabinet 100.

  A manual mechanism 700 is connected to the power supply built-in switch 300, and a manual mechanism 700 and an automatic mechanism 800 are connected to the three-circuit switch 400, respectively. These are accommodated in the cabinet case 900. Actually, under the power supply built-in switch 300, the three-circuit switch 400, the mold diescon 500, and the UGS (Ground switch for gas distribution) 600, cables 1000 (FIG. 6) are connected to the power company side and the customer side, respectively. Is connected).

  As shown in FIG. 6, the coated surface thermometer 20 is installed in each cable 1000. Similar to the calibration, a heat conductive material is interposed between the cable 1000 and the coated surface thermometer 20, and the whole is covered with a seal layer. An environmental thermometer 30 is also arranged in the cabinet case 900. Current measurement is performed in such a state.

The arithmetic processing unit 50 first transmits ID data for specifying the environmental thermometer 30 to the bus cable 40. The communication function unit 33 of the environmental thermometer 30 that matches the ID data accesses the temperature measurement function unit 31. The temperature measurement function unit 31 outputs the detected temperature measurement value, and the correction value setting function unit 32 adds or subtracts a predetermined correction value that is digital data to the temperature measurement value that is digital data output from the temperature measurement function unit 31. And output as an environmental temperature value.
The arithmetic processing unit 50 determines one prediction formula based on this environmental temperature value from a plurality of prediction formulas registered at the time of calibration. For example, if an environmental temperature value falls between t1 [° C.] and t2 [° C.], the associated prediction formula is determined.

Subsequently, the arithmetic processing unit 50 transmits ID data for specifying the coated surface thermometer 20 to the bus cable 40. The communication function unit 23 of the coated surface thermometer 20 that matches the ID data accesses the temperature measurement function unit 21. The temperature measurement function unit 21 outputs the detected temperature measurement value, and the correction value setting function unit 22 adds or subtracts a predetermined correction value that is digital data to the temperature measurement value that is digital data output from the temperature measurement function unit 21. And output as a surface temperature value.
The arithmetic processing unit 50 calculates the surface temperature increase value T [1] by subtracting the environmental temperature value from the surface temperature value, and substitutes this surface temperature increase value T [1] for the previous prediction equation as shown in the following equation. Current value I [1] is obtained.

(Equation 2)
I [1] = aT ² [1] + bT [1] + c

  Thereafter, the arithmetic processing unit 50 sends ID data for specifying the other coated surface thermometer 20 and finally performs the same processing to finally increase the surface temperature rise values T [1], T [2],. From [i],..., T [n], current values I [1], I [2],..., I [i],. In this way, the current measuring device 10 estimates the energization current values of all the cables 1000 almost accurately.

Next, another embodiment will be described with reference to the drawings. In this embodiment, more accurate measurement is realized. FIG. 7 is a configuration diagram of a current measurement device according to another embodiment, and FIG. 8 is an explanatory diagram of the arrangement of the current measurement device.
The current measuring device 10 ′ includes a coated surface thermometer 20, an environmental thermometer 30, a bus cable 40, an arithmetic processing unit 50, and a current transformer 60. In this embodiment, compared to the previous embodiment, the current configuration is the same except that a current transformer 60 is added, and the current transformer 60 will be described mainly, and the other configuration is the same as the previous description. A duplicate description is omitted.

The current transformer 60 in this embodiment is attached to the cable 1000 before branching, particularly on the input side. This is because there is a relatively large space around the cable 1000 before branching on the input side, and for example, a through ring of a split type or clamp type current transformer 60 can be attached.
The arithmetic processing unit 50 transmits ID data for identifying the current transformer 60 to the bus cable 40. A communication function unit (not shown) that matches the ID data accesses a current measurement function unit (not shown). A current measurement function unit (not shown) processes an electrical signal from a not-shown penetrating ring and outputs a digital data current value. A correction value setting function unit (not shown) is a current measurement function unit (not shown). The predetermined correction value that is digital data is added to or subtracted from the current value that is digital data output from (1)) and output as a current value.
The arithmetic processing unit 50 uses the input current value as it is as the energization current value I [1]. By using a current transformer, the value of the current flowing through the cable on the input side can be accurately calculated.
In addition, in the plurality of branched cables on the output side that have passed through the power supply built-in switch 300, the three-circuit switch 400, the mold discon 500, and the UGS (ground switch for gas distribution) 600, as described above. The predicted current value is based on temperature.
By configuring in this way, a relatively small thermometer is installed in a place where there is not enough space, and a relatively large current transformer is attached in a place where there is room in the space so that accurate measurement can be performed. be able to.

  Furthermore, using such a current measuring device 10, for example, the trunk line 101 connected to one end of the main switch 104 with respect to the distribution board 102 shown in FIGS. 9A and 9B and FIG. 10. The energizing current value is accurately measured at one location via a current transformer (not shown), and the surface of each branch distribution line 103 connected from the other end of the main switch 104 via the branch switch 105 is covered. A thermometer (not shown) is arranged and taken in, and the energizing current value of the main line 101 is apportioned according to the surface temperature of each branch distribution line 102, whereby each branch distribution line 103 in the distribution board 102 is expensive. Without installing a large number of current transformers, current measurement corresponding to each branch distribution line 103 can be easily performed at low cost.

  The present embodiment has been described above. The current measuring method and the current measuring device according to the present invention replace the conventional current measurement by converting the energization current of an electric wire, a power cable or the like into a surface temperature rise value due to heat generation. In particular, by installing temperature sensors on wires and power cables in cabinets and enclosures such as distribution boards that form branch circuits, the sensors themselves can be miniaturized and construction simplified, and each wire can be manufactured at low cost. Current measurement is possible for power cables.

It is a block diagram of the current measuring device of the best form for implementing this invention. It is an internal block diagram of a thermometer. It is explanatory drawing of the initial calibration by an electric current measuring apparatus. It is explanatory drawing of a prediction formula. It is explanatory drawing of a cabinet. It is arrangement | positioning explanatory drawing of an electric current measurement apparatus. It is a block diagram of the electric current measuring apparatus of another form. It is arrangement | positioning explanatory drawing of an electric current measurement apparatus. FIG. 9A is an explanatory view of a distribution board, FIG. 9A is an external view of the distribution board, and FIG. 9B is an internal view of the inside of the main body in a state where the door of the distribution board is opened. It is a connection diagram inside a distribution board.

Explanation of symbols

1: Variable current power source 2: Load 3: Air conditioner 10: Current measuring device 20: Coating surface thermometer 21: Temperature measuring function unit 22: Correction value setting function unit 23: Communication function unit 24: Connector unit 30: Environmental thermometer 31: Temperature measurement function section 32: Correction value setting function section 33: Communication function section 34: Connector section 40: Bus cable 50: Arithmetic processing section 60: Current transformer 100: Cabinet 200: Mold bus 300: Switch with built-in power supply 400: Three-circuit switch 500: Molded discon 600: UGS
700: Manual switch 800: Automatic switch 900: Cabinet case 1000: Cable 101: Main line 102: Distribution board 103: Branch distribution line 104: Main switch 105: Branch switch

Claims (5)

A coated surface thermometer that measures the surface temperature value of the energized cable sheath;
An environmental thermometer that acquires the environmental temperature value near the cable;
An arithmetic processing unit connected so that these coated surface thermometers and environmental thermometers communicate,
A current transformer that measures the current flowing through the cable before branching on the input side, and
The arithmetic processing unit includes:
For the cable before branching on the input side, means using the measured value by the current transformer,
A registration means for previously registering a plurality of prediction formulas for each environmental temperature value, which is a polynomial expression based on a surface temperature increase value obtained by subtracting the environmental temperature value from the surface temperature value of the cable after branching on the output side;
An acquisition means for acquiring a surface temperature value and an environmental temperature value;
Reading means for reading out a prediction formula corresponding to the acquired environmental temperature value from a plurality of prediction formulas after selection;
A calculation means for calculating a predicted current value by substituting the surface temperature rise value for the read prediction formula;
Current measuring device characterized by functioning as The current measuring device according to claim 1,
In a plurality of branched cables on the output side, a current measuring device is provided with a predicted current value by apportioning the current value measured by the current transformer based on the temperature by the coated surface thermometer. . In the current measuring device according to claim 1 or 2,
The coated surface thermometer is
A temperature measurement function unit for measuring the surface temperature value;
A correction value setting function unit for correcting the measured surface temperature value;
A communication function unit for performing communication via a communication line;
Fixing means for tightly fixing at least the installation surface of the temperature measurement function section and the covering surface of the cable;
With
A current measuring device for transmitting a surface temperature value via a communication line . The current measuring device according to claim 3,
The fixing means includes a thermally conductive substance that tightly fixes the installation surface of the coated surface thermometer and the coated surface of the cable;
A sealing layer covering the thermometer;
An adhesive covering the sealing layer;
Current measuring device comprising a means der Rukoto by. In the current measuring device according to claim 3 or 4 ,
A current measuring device characterized in that the temperature measuring function unit, the correction value setting function unit, and the communication function unit are housed in a case or integrated into a packaged surface thermometer .

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