JP3137523B2 - Current measuring method and current measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring an alternating current flowing through a conductor without contacting the conductor.

[0002] The present invention also relates to a current measuring device for measuring an alternating current using the above-described current measuring method.

[0003]

2. Description of the Related Art As a device for measuring an alternating current flowing through a conductor, there is a so-called clamp meter. The clamp meter includes a magnetic core surrounding a conductor and a magnetic field detecting element such as a Hall element for measuring a magnetic field intensity in the magnetic core. In order to surround the conductor, a magnetic core having a half-cylindrical shape is used.

[0004]

In the conventional clamp meter, since it is necessary to surround the conductor, a space must be provided around the conductor, and measurement cannot be performed if there is an insulating barrier or the like.

[0005] In addition, it is difficult to remotely enclose a conductor with a magnetic core of a clamp meter for a high-voltage bare conductor such as a transmission line or a substation facility, in terms of safety and workability. Now.

The present invention has been made in view of the circumstances of current measurement by the above-described conventional clamp meter, and has a current measurement method in which an AC current can be measured in a non-contact manner by approaching a conductor to be measured. It is an object to provide a method and a current measuring device.

[0007]

In order to achieve the above object, according to the current measuring method of the present invention, two detection coils having the same shape and the same number of windings are supplied to an AC current flowing through a conductor whose current is to be measured. With the same orientation with the coil axis oriented in the direction of the magnetic flux generated by the current, and with the relative distance to the conductor shifted by a predetermined dimension, the two electrodes are brought closer to the conductor and the induced electromotive force induced in the two detection coils is reduced. Each of them is measured and the approach distance between one of the detection coils and the conductor is calculated from the ratio of these two induced electromotive forces, and the bending distance and the induced electromotive force induced in the one detection coil are calculated. From this, the alternating current flowing through the conductor is calculated.

[0008] A rectangular coil having one side parallel to the conductor may be used as the detection coil.

In the current measuring device of the present invention, two detecting coils having the same shape and the same number of turns are provided side by side with the coil axis parallel to a detecting portion which is brought close to a conductor to be measured. A voltage measuring unit that measures a voltage between both ends of a resistor interposed between the output terminals of the two detection coils, and sets the detection unit in a direction of a magnetic flux generated by an alternating current flowing through the conductor; And the relative distance of the two detection coils to the conductor is deviated by a predetermined dimension, and the central processing unit supplies any one of the ratios of the two measured voltages measured by the voltage measurement unit to the central processing unit. An arithmetic processing unit that calculates an approach distance between one of the detection coils and the conductor and calculates a value of the AC current from the approach distance and the measurement voltage by the detection coil; Configured to provide a display unit for displaying the computed AC current value.

Further, the detecting section is provided with an electro-optical converting section for converting an electric signal corresponding to a measured voltage outputted from the voltage measuring section into an optical signal, and connects between the detecting section and the central processing section. The optical signal is transmitted to the central processing unit by an optical fiber cable, and the central processing unit is provided with an optical-electrical conversion unit that reconverts the optical signal into an electric signal and provides the electric signal to the arithmetic processing unit. it can.

[0011]

In the current measuring method according to the first aspect, an AC current is calculated from induced electromotive forces generated in two same detection coils whose relative distance from a conductor to be measured is shifted by a predetermined dimension. it can. In addition, it is only necessary to bring the two detection coils close to the conductor in a non-contact manner to generate an induced electromotive force in the two detection coils, so that the work is easy and the current can be measured if there is a space in one of the conductors. is there.

According to the second aspect of the present invention, since a rectangular coil having one side parallel to the conductor is used as the detection coil, the induction coil generated in the detection coil by the magnetic field generated by the alternating current flowing through the conductor is used. The calculation formula of the electric power is easier than the detection coil of another shape, and the calculation can be easily and quickly performed.

Further, in the current measuring device according to the third aspect, since the device is divided into a detecting unit and a central processing unit, the arithmetic processing in the central processing unit is hardly influenced by a magnetic field near the conductor. .

Further, in the current measuring device according to the fourth aspect, since the optical signal is transmitted between the detection unit and the central processing unit, electric noise does not overlap with the signal in the signal path. . Moreover, in the current measurement of the high voltage charging unit, the detection unit and the central processing unit can be sufficiently separated and electrically insulated, so that the current measurement can be performed safely.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the current measuring method according to the present invention will be described below with reference to FIGS. FIG. 1 is a plan view for explaining the principle of the current measuring method of the present invention, FIG. 2 is a side view of FIG. 1, and FIG. 3 is a flowchart showing the procedure of the current measuring method.

First, the principle will be described with reference to FIGS. The first detection coil 12 and the second detection coil 14 are arranged in a non-contact manner close to the conductor 10 to be measured. These first detection coil 12 and second detection coil 1
Reference numeral 4 denotes a rectangular shape having the same vertical and horizontal dimensions of l ₁ × l _{2 and} the same number of turns N. Moreover, one side of the rectangular shape is parallel to the conductor 10, the relative distance from the conductor 10 is shifted by a predetermined dimension r, and the coil axis is parallel and the posture matches the direction of the magnetic flux generated around the conductor 10. In the drawing, r ₁ and r ₂ are distances from the center of the conductor 10 to the first detection coil 12 and the second detection coil 14, but are unknown.

Therefore, the induced electromotive force e1 generated in the first detection coil 12 is expressed by the following equation ( ₁ ).

(Equation 1) Here, μ ₀ is the vacuum permeability, _Im is the maximum value of the alternating current i,
ω is an angular frequency and can be treated as a known number if the AC current i is a commercial frequency.

Further, the induced electromotive force e2 generated in the second detection coil 14 is expressed by the following equation ( ₂ ).

(Equation 2)

Then, resistors R ₁ and R ₂ are inserted between the output terminals of the first detection coil 12 and the second detection coil 14, respectively, and induced as voltage drops v ₁ and v ₂ of the resistors R ₁ and R _2. The power can be measured individually. Assuming that v ₁ and v ₂ are the effective values, I is the effective value of the alternating current i flowing through the conductor 10, and ω = 2πf, Equation 1 is expressed as Equation 3 and Equation 2 is expressed as Equation 4. Then, if the ratio between v ₁ and v ₂ is obtained, the result becomes Expression 5, and since r ₂ = r ₁ + r, Expression 6 can be rewritten. In Equation 6, the values of v ₁ and v ₂ are obtained from the measurement, and r and ₁₁ are known numbers. Therefore, r ₁ can be obtained by calculation by an extrapolation method or the like.

(Equation 3)

(Equation 4)

(Equation 5)

(Equation 6)

Furthermore, the number 3, can be rewritten as Equation 7, by inserting r ₁ that is calculated on the number 7 using 6, the effective value I of the alternating current i can be calculated.

(Equation 7)

Based on the above principle, the current is measured in the procedure shown in FIG. First, each arithmetic expression and the first detection coil 12 are stored in advance in an arithmetic processing unit such as a microcomputer.
And data l ₁ , l ₂ , r, N,
μ ₀ , f, etc. are set (step). And the first
By folding the detection coil 12 and the second detection coil 14 on the conductor 10, the first detection coil 12 and the second detection coil 14
Induced electromotive forces e ₁ and e ₂ are generated at
Measure v ₁ and v ₂ (step). These v ₁ ,
v ₂ , distance r between conductor 10 and first detection coil 12
₁ is obtained by calculation (step), and the AC current i
An effective value I is obtained by calculation (step). Finally, the effective value I obtained by this calculation is appropriately displayed on the display unit (step).

In the current measuring method of the present invention,
The alternating current i flowing through the conductor 10 such as a high-voltage bare conductor of a transmission line or a substation facility can be measured in a live state.
Moreover, the first detection coil 12 and the second detection coil 14 need only be brought closer to the conductor 10 from one direction, and the conductor 10
No space such as a conventional clamp meter is required around the device. Furthermore, the first detection coil 12 and the second detection coil 14 need only be brought close to each other, and it is not necessary to regulate the approach distance to the conductor 10 to a predetermined size. The operation is easy, and the effect is remarkable in practical use.

Next, a current measuring device used for carrying out the current measuring method will be described with reference to FIG. FIG.
It is a block circuit diagram of one example of a current measuring device of the present invention.

In FIG. 4, the first detection coil 12 and the second
The detection coil 14 is provided in the detection unit 20 in the shape and the posture as described in the current measuring method. The detection unit 20 is further provided with a voltage measurement unit 22 for measuring the voltage across the resistors R ₁ and R ₂ interposed between the output terminals of the first detection coil 12 and the second detection coil 14, respectively. .
A twisted pair or a coaxial cable is used to connect the resistors R ₁ and R ₂ to minimize the influence of noise. Further, the detection unit 20 includes an electro-optical conversion unit 24.
Is provided, and an electric signal output from the voltage measurement unit 22 according to the voltage between both ends of the resistors R ₁ and R ₂ is converted into an optical signal.

The housing of the detection unit 20 is provided with a contact portion of an appropriate shape which is made of, for example, an insulating material and which can be brought into contact with the outer periphery of the conductor 10 so as to easily follow the conductor. When the contact portion is brought into contact with the conductor 10, the first detection coil 1
The second detection coil 14 and the second detection coil 14 may be configured so as to have a desired arrangement and posture with respect to the conductor 10 as shown in FIGS. When the target conductor 10 is extremely high pressure and it is not desirable to make contact with the insulating material, the arrangement and posture of the first detection coil 12 and the second detection coil 14 with respect to the conductor 10 are regulated by other appropriate means. What should be done.

The central processing unit 30 is provided separately from and separate from the detection unit 20, and the detection unit 20 and the central processing unit 30 are provided separately.
Are connected by an optical fiber cable 40 for transmitting an optical signal output from the electro-optical converter 24.
The central processing unit 30 includes an optical-electrical conversion unit 3 that reconverts the optical signal transmitted through the optical fiber cable 40 into an electric signal.
2 are provided. The central processing unit 30 is also provided with an arithmetic processing unit 34, a display unit 36, and a storage unit 38. The electrical signal reconverted from the optical signal is supplied to an arithmetic processing unit 34 including a microcomputer or the like, and the effective value I of the alternating current i flowing through the conductor 10 is obtained by the arithmetic operation described in the above-described current measuring method. The value I is appropriately displayed on the display unit 36 and stored in the storage unit 38 as appropriate. Storing the effective value I as the calculation result in the storage unit 38 is effective for reading out the data at a later date and reconfirming the measurement result.

The detection unit 20 and the central processing unit 30 each have an appropriate driving power supply (not shown). Also,
In the detection unit 20, another coil may be provided, and the induced electromotive force generated in this coil may be used as a driving power supply.

In this configuration, the detection unit 20 exposed to the magnetic flux generated in the conductor 10 and the central processing unit 30 for performing arithmetic processing on the measurement result are separately provided, so that the magnetic field of the central processing unit 30 can be reduced. The adverse effect can be minimized, which can contribute to the improvement of measurement accuracy. Then, the detection unit 20
Since the optical signal is transmitted between the central processing unit 30 and the central processing unit 30 via the optical fiber cable 40, electric noise is not superimposed on the transmission path of the signal, and the measurement accuracy can be improved. In addition, by separating the detection unit 20 and the central processing unit 30, when a remote control rod or the like is used, the detection unit 20 which is lighter than the entire device may be provided at the tip of the remote control rod, and thus the operability is excellent. It will be. Further, the detection unit 20 and the central processing unit 30 can be sufficiently separated and electrically insulated, so that current can be safely measured.

In the description of the above embodiment, the first
Although the detection coil 12 and the second detection coil 14 have been described using rectangular coils, the present invention is not limited to this, and a circular coil, an elliptical coil, a triangular coil, or the like can be used as the detection coil. In these circular coils and the like, it is easy to see that the equations representing the induced electromotive forces e ₁ and e ₂ are different from Equations ₁ and ₂ , respectively, and that the equations for calculating the effective value I of the AC current i are different. Will be appreciated.

In the current measuring method according to the present invention, the distance r ₁ between the first detection coil 12 and the conductor 10 is calculated from the ratio of the induced electromotive force between the first detection coil 12 and the second detection coil 14. In other words, the approach distance to the conductor 10 through which the AC current i flows can be measured, and in other words, the calculated distance can be used to function as a proximity sensor or the like.

Furthermore, in FIG. 3 step, instead of the distance r ₁ between the first detection coil 12 and the conductor 10, the distance r ₂ between the second detection coil 14 and the conductor 10 so as to calculate Of course, it is also good.

[0032]

As is apparent from the above description, in the current measuring method according to the first aspect of the present invention,
An AC current can be measured by approaching the conductor to be measured for current in a non-contact manner. Then, it is sufficient that the conductor can be approached from one side of the conductor, no space is required around the conductor, and the measurement is not hindered by an insulating barrier or the like. In addition, since the approach operation from one side is sufficient and the approach distance is not restricted to a predetermined dimension, the operation required for the measurement is simple, and the operation using the remote control rod or the like is easy. is there.

In the current measuring method according to the second aspect, the arithmetic processing is easy, and accordingly, a microcomputer or the like used as the arithmetic processing unit may be simple, and the arithmetic result of the effective value of the AC current may be reduced. Obtained quickly. In addition, measurement can be performed with an inexpensive device.

In the current measuring apparatus according to the third aspect of the present invention, the detecting section and the central processing section are separated from each other so that the central processing section is located at a position free from the influence of the magnetic field generated in the conductor. Therefore, there is no possibility that an erroneous calculation is performed due to noise mixed in the calculation process, and the reliability of the measurement result is high. Further, the weight of the detection unit approaching the conductor can be reduced, and a detection unit excellent in operability can be configured.

In the current measuring device according to the fourth aspect, since the signal is transmitted by the optical signal, electric noise is not superimposed on the signal transmission path, and the accuracy of the measurement result is high. It will be. In addition, the central processing unit can be sufficiently separated from the detection unit and electrically insulated, so that the current can be measured safely.

[Brief description of the drawings]

FIG. 1 is a plan view illustrating the principle of a current measuring method according to the present invention.

FIG. 2 is a side view of FIG.

FIG. 3 is a flowchart showing a procedure of a current measuring method.

FIG. 4 is a block circuit diagram of an embodiment of a current measuring device according to the present invention.

[Explanation of symbols]

10 the conductor 12 the first detection coil 14 and the second detection coil 20 detector 22 the voltage measuring unit 24 electro - optical conversion unit 30 central processing unit 32 light - electrical converter 34 arithmetic processing unit 36 display unit 40 the optical fiber cable R _{1, R 2} resistance

Claims (4)

(57) [Claims] 1. A detection coil comprising two detection coils having the same shape and the same number of turns in the same position with the coil axis oriented in the direction of a magnetic flux generated by an alternating current flowing through a conductor to be measured, and a relative distance to the conductor. Are shifted by a predetermined dimension, approach the conductor, measure the induced electromotive force induced in the two detection coils, respectively, from the ratio of these two induced electromotive force, one of the detection coil and the A current measurement method comprising: calculating an approach distance to a conductor; and calculating an alternating current flowing through the conductor from the approach distance and the induced electromotive force induced in the one detection coil. 2. The current measuring method according to claim 1, wherein
A current measuring method, wherein a rectangular coil having one side parallel to the conductor is used as the detection coil. 3. A detection unit for approaching a conductor to be measured for current is provided with two detection coils of the same shape and the same number of turns arranged side by side with the coil axes parallel to each other. A voltage measuring unit for measuring a voltage between both ends of a resistor interposed between the output terminals, wherein the coil axis of the detection coil is oriented in a direction of a magnetic flux generated by an alternating current flowing through the conductor, and The relative distance of the two detection coils to the conductor is shifted by a predetermined dimension, and the central processing unit supplies one of the detection coil and the conductor based on a ratio of the two measurement voltages measured by the voltage measurement unit. And an arithmetic processing unit for calculating a value of the AC current from the approach distance and the measured voltage by the detection coil, and calculating the calculated AC current value. Provided Shimesuru display unit, the current measuring device, wherein a. 4. The current measuring device according to claim 3, wherein
An electric-optical conversion unit that converts an electric signal corresponding to a measured voltage output from the voltage measurement unit to an optical signal is provided in the detection unit, and the light is transmitted through an optical fiber cable that connects the detection unit and the central processing unit. Transmitting a signal to the central processing unit;
A current measuring device, wherein the central processing unit is provided with an optical-electrical conversion unit for converting the optical signal into an electric signal again and supplying the electric signal to the arithmetic processing unit.