JP7034484B2 - Clamp sensor and clamp meter - Google Patents

Description

The present invention relates to a clamp sensor that can be applied to a large area structure including a conductor to be measured, and a clamp meter that can detect a current by using the clamp sensor.

When measuring the current of the conductor to be measured (or measuring the leakage current in the circuit) without turning off the circuit power supply, the conductor to be measured is clamped by a clamp sensor, and the current flowing through the conductor to be measured (or the leakage current in the circuit) is measured. ) Is known as a clamp meter that obtains the current value from the magnetic field generated by). If an AC circuit is to be detected, a CT (Current Transformer) type clamp meter that converts the measured current into a secondary current according to the coil turns ratio is widely used (see, for example, Patent Document 1). ). In the CT type clamp meter, in order to block the influence of the magnetic field received from the outside, a method is adopted in which the sensor portion is covered with a shield made of a ferromagnetic material having a large magnetic permeability to forcibly block the external magnetic field (for example). , Patent Document 2).

Further, in a large structure (pillar or the like) including the conductor to be measured, the cross section of the clamp portion has a large area. When measuring the current of such a large-area structure, a Rogowski coil type clamp meter that can clamp the entire structure to detect the current can be used (see, for example, Patent Document 3).

Japanese Unexamined Patent Publication No. 2018-031608 Japanese Unexamined Patent Publication No. 11-295346 Japanese Unexamined Patent Publication No. 2011-174769

However, although the CT type clamp sensor described in Patent Document 1 described above can measure a minute current at the mA level, a standard commercially available product has a clamp diameter of only about 70 mm and a large area including a conductor to be measured. It is not possible to clamp the entire structure with a large diameter. On the other hand, the Rogowski coil (air-core coil) described in Patent Document 2 can clamp a large-area structure including a conductor to be measured with a large diameter, but can measure a low current of 10 A or less (small leakage current, etc.). I can't. In addition, the Rogowski coil type clamp meter cannot adopt a shield structure to block the influence of an external magnetic field.

In electrical maintenance and inspection, it is necessary to measure a minute leakage current (or ground current) to judge whether the insulation state is good or bad, and even if the target is a large-area structure, the minute current is used to judge the insulation state. Need to be possible to measure. Moreover, in the measurement of the minute current by the clamp meter, the detection error due to the influence of the external magnetic field cannot be ignored, and the measurement accuracy is lowered.

Therefore, the present invention can suppress the influence of an external magnetic field without using a metal shield or the like that hinders the enlargement and weight reduction of the clamp diameter, and can detect a minute current flowing through a large-area structure including a conductor to be measured. The purpose is to provide a clamp sensor and a clamp meter.

In order to solve the above problem, in the invention according to claim 1, a connecting core which becomes an annular iron core which surrounds the measured conductor in a non-contact manner by connecting both ends thereof, and a coil can be arranged on the outer periphery of the connecting core. A coil body including a coil body, wherein the coil body has an inner space portion into which the connecting core can be inserted, and from each end portion, a first attachment / detachment end portion and a second attachment / detachment portion of the connection core are attached. An inner coil having a length that allows each end to be exposed and having flexibility that can be reasonably deformed following the deformation of the connecting core, and an inner coil formed by winding a magnet wire around the outer surface of the inner layer tube. A middle layer tube arranged so as to cover the outside of the inner coil, and an outer coil formed by winding a magnet wire around the outer surface of the middle layer tube, and the outer surface side of the coil body is an insulating outer layer tube. In addition to being covered with, a connecting core is inserted in the inner space of the coil body so that the current flowing through the conductor to be measured can be detected simultaneously by the inner coil and the outer coil.

Further, in the invention according to claim 2, in the clamp sensor according to claim 1, the connecting core is made of a high magnetic permeability soft magnetic material, and the first connecting portion and the first connecting portion are respectively at the pair of most separated ends. By using a plurality of connecting prime fields forming the second connecting portion and connecting the first connecting portion and the second connecting portion so as to form a rotatable uniaxial joint, a beaded joint shape with both ends open. It has a connected structure, the first unconnected connecting part in the connecting element at one end is the first detachable end, and the second unconnected connecting part in the connecting element at the other end is the second detachable end. By connecting the first detachable end portion and the second detachable end portion, all the connecting prime fields form an annular iron core that is closed in an annular shape.

Further, according to the third aspect of the present invention, in the clamp sensor according to the second aspect, the connecting prime field of the connecting core is required by laminating a plurality of base materials which are plate materials of high magnetic permeability soft magnetic material. The base material is configured to have a thickness, and the base material has a convex end edge portion that protrudes in an arc shape equidistant from the axial position connected so as to be a uniaxial joint on one end side, and the protruding end edge. A concave end edge portion that is recessed in an arc shape with a curvature equivalent to that of the portion is provided on the other end side, respectively, and the convex end edge portion and the concave end edge portion of the base material are alternately laminated to form a connecting prime field. The first connecting portion and the second connecting portion have a fitting structure in which the convex end edge portion and the concave end edge portion mesh with each other, and each connecting prime field connected by a uniaxial joint has a fitting structure. The base material is characterized in that the convex end edges and the concave end edges of each other can rotate within a required range without interfering with each other.

In order to solve the above problems, the clamp meter according to claim 4 includes the clamp sensor according to any one of claims 1 to 3, and the inner coil and the outer coil of the clamp sensor are used, respectively. It is characterized by providing a measuring device that acquires the detected inner coil measured current value and outer coil measured current value and calculates the current value flowing through the conductor to be measured based on the inner coil measured current value and the outer coil measured current value. And.

Further, according to the fifth aspect of the present invention, in the clamp meter according to the fourth aspect, when the windings of the outer coil and the inner coil are the same and the clamp sensor is not affected by the external magnetic field, the inner coil measurement current is measured. It is characterized in that the value and the measured current value of the outer coil are made to match.

Further, the invention according to claim 6 is the clamp meter according to claim 5, wherein the measuring device is a difference current which is a difference between the outer coil measured current value and the inner coil measured current value acquired from the clamp sensor. The inner correction current value is calculated by using the storage means for storing the calculation formula for obtaining the inner correction current value generated by the external magnetic field acting on the inner coil from the value and the calculation formula of the storage means, and the inner coil measurement current is measured. By subtracting the inner correction current value from the value, the true measured value by the clamp sensor is obtained, and the calculation means for obtaining the current value flowing through the measured conductor from the true measured value is provided.

Further, according to the invention of claim 7, in the clamp meter according to claim 5, the measuring device is a difference current which is a difference between the outer coil measured current value and the inner coil measured current value acquired from the clamp sensor. The outer correction current value is calculated by using the storage means for storing the calculation formula for obtaining the outer correction current value generated by the external magnetic field acting on the outer coil from the value and the calculation formula of the storage means, and the outer coil measurement current is measured. By subtracting the outer correction current value from the value, the true measured value by the clamp sensor is obtained, and the calculation means for obtaining the current value flowing through the measured conductor from the true measured value is provided.

According to the clamp sensor according to the present invention, an annular core having a necessary and sufficient diameter can be formed by a connecting core in which an appropriate number of connecting prime fields are connected according to a large area structure including a conductor to be measured. .. Then, a large-area structure is surrounded with the first attachment / detachment portion and the second attachment / detachment portion of the connecting core open, and the first attachment / detachment portion and the second attachment / detachment portion are connected to form an annular iron core, and a coil is formed on the outer periphery thereof. The coil is arranged by the body. Therefore, if a large-area structure is clamped by a clamp sensor, a secondary current corresponding to the coil turns ratio can be obtained from the inner coil and the outer coil from the change in the magnetic field caused by the alternating current to be detected. The measuring device that acquired the inner coil measured current value and the outer coil measured current value from the clamp sensor calculates the true measured value that corrects the influence of the outer coil and the inner coil from the external magnetic field, and receives the true measured value from the true measured value. Calculate the current value flowing through the measurement conductor. This makes it a clamp meter that can measure minute currents without being affected by an external magnetic field.

It is a schematic block diagram of the clamp meter which concerns on embodiment of this invention. A clamp sensor used for the clamp meter is shown, (a) is a partially missing plan view, and (b) is a partially missing side view. It is a bird's-eye view perspective view of the basic link constituting the connecting core. It is a top view of the base material which constitutes a basic link. It is an assembly explanatory drawing of the basic link using a base material. (A) is a rear view of the basic link. (B) is an enlarged schematic end view of FIG. 6A in the direction of the arrow on the VIb-VIb line. (A) is a plan view of the first basic link and the second basic link connected. (B) is an enlarged schematic end view of FIG. 7 (a) in the direction taken along the line VIIb-VIIb. It is explanatory drawing of the manufacturing process of a coil body. It is explanatory drawing of the assembly process of a clamp sensor. It is a usage method explanatory drawing at the time of measuring the ground current (or leakage current) of a utility pole by the clamp meter which concerns on this embodiment. It is explanatory drawing of the measurement principle by an inner coil and an outer coil.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a schematic configuration of a clamp meter 1, which performs a predetermined calculation based on a clamp sensor 2 that clamps a measured line and a detection current of the clamp sensor 2, and obtains a digital value of the measurement result. It is composed of a measuring device 3 that displays (or an analog value).

The clamp sensor 2 includes a connecting core 4 that becomes an annular iron core that non-contactly surrounds the conductor to be measured by connecting both ends thereof, and a coil holding tube 5 that holds a state in which a coil is arranged on the outer circumference of the connecting core 4. .. As will be described later, the connecting core 4 can be bent and stretched by removing the first detachable end portion 4a and the second detachable end portion 4b. Therefore, when a large-area structure (for example, a utility pole) including a conductor to be measured is surrounded by a clamp sensor 2 and the first attachment / detachment end portion 4a and the second attachment / detachment end portion 4b are connected, an annular iron core surrounding the peripheral surface of the utility pole or the like is formed. can do. The connecting core 4 that has become an annular core functions as a closed magnetic path that efficiently passes the magnetic flux generated by the current flowing through the conductor to be measured.

Further, the coil holding tube 5 has flexibility and insulation that can be reasonably deformed following the deformation of the connecting core 4. Therefore, when the connecting core 4 is closed to form an annular core, the coils in the coil holding tube 5 are also arranged in an annular shape, and the magnetic flux generated by the alternating current flowing through the conductor to be measured concentrates on the annular core. A secondary current flows through the coil of the coil holding tube 5 so as to cancel this change in magnetic flux. Since this secondary current can be obtained as a magnitude corresponding to the turns ratio of the coil in the coil holding tube 5 with respect to the primary current flowing through the conductor to be measured, the detection sensitivity capable of detecting a minute current of about several mA can be obtained. It is easy to set to.

Further, in order to prevent the work of clamping a large-area structure by the clamp sensor 2 from becoming complicated, a first connection guide 6 is provided on the side of the first attachment / detachment end 4a of the connection core 4 in the clamp sensor 2 of the present embodiment. A second connecting guide 7 is provided on the attachment / detachment end portion 4b side. As the first and second connecting guides 6 and 7, a known and existing appropriate structure capable of easily attaching and detaching the first attachment / detachment end portion 4a and the second attachment / detachment end portion 4b can be applied. The connection cable 8 is extended from the first connection guide 6 in the clamp sensor 2 and connected to the measuring device 3.

The measuring device 3 receives a detection signal from a coil (described in detail later) in the coil holding tube 5 via the connection cable 8, and converts the detection signal (voltage signal) into current information by a shunt resistor for current detection. Convert. Further, the measuring device 3 is at least a storage means 31 for storing in advance a calculation formula for calculating the current value flowing through the conductor to be measured from the detected current of the clamp sensor 2, and a calculation means 32 for performing the calculation using this calculation formula. , The display unit 33 for visually displaying the calculation result and the like are provided. In addition, a function for storing the history of measured values, a function for outputting history information to the outside, a voice output function for notifying measurement results and warnings by voice, and the like may be added to the measuring device 3.

The schematic structure of the clamp sensor 2 described above is shown in FIG. The clamp sensor 2 can be used in any direction depending on the orientation of the conductor to be measured, but in the following description, for convenience, the cross-sectional direction that can be clamped by the clamp sensor 2 is the lateral direction (or horizontal direction). The orthogonal direction will be described as the vertical direction (or the vertical direction). Therefore, FIG. 2A shows the inside by cutting out a part of the clamp sensor 2 in the horizontal direction, and FIG. 2B shows the inside by cutting out a part of the clamp sensor 2 in the vertical direction. It is a thing.

The connecting core 4 is, for example, 14 connecting elements, the first basic link 40-1, the second basic link 40-2, ..., the twelfth basic link 40-12, the thirteenth basic link 40-13, and the first. 14 Basic links 40-14 are connected. The first to 14th basic links 40-1 to 40-14 all have the same shape, and are simply referred to as basic links 40 when there is no particular need to distinguish them. These 1st to 14th basic links 40-1 to 40-14 are formed by laminating the base material 41 described later and fixing them with rivets 42, and the first connecting portion 14a and the pair of most separated ends are respectively connected to the first connecting portion 14a. The second connecting portion 14b is formed.

When connecting the first basic link 40-1 and the second basic link 40-2, the second connecting portion 40b in the first basic link 40-1 (this is referred to as the first basic link second connecting portion 40-1b). , And the same) and the second basic link first connecting portion 40-2a are connected by the uniaxial joint connecting portion 43 so as to form a rotatable uniaxial joint. When connecting the second basic link 40-2 and the third basic link 40-3, the second basic link second connecting portion 40-2b and the third basic link first connecting portion 40-3a are connected to the uniaxial joint connecting portion. Connect by 43. The same applies to the case of connecting the third basic link 40-3 to the twelfth basic link 40-12, and thus the description thereof will be omitted. When connecting the twelfth basic link 40-12 and the thirteenth basic link 40-13, the twelfth basic link second connecting portion 40-12b and the thirteenth basic link first connecting portion 40-13a are connected to the uniaxial joint connecting portion. Connect by 43. When connecting the 13th basic link 40-13 and the 14th basic link 40-14, the 13th basic link second connecting portion 40-13b and the 14th basic link first connecting portion 40-14a are uniaxially jointly connected. It is connected by the part 43. By doing so, the connecting core 4 has a beaded connecting structure with both ends open. At this time, the unconnected first basic link first connecting portion 40-1a remains in the first basic link 40-1 which is the connecting prime field at one end, and the 14th basic link which is the connecting prime field at the other end remains. The 14th basic link second connecting portion 40-14b, which is not connected, remains in 40-14.

Therefore, the first basic link first connecting portion 40-1a can be the first detachable end portion 4a, and the 14th basic link second connecting portion 40-14b can be the second detachable end portion 4b. Then, by connecting the first detachable end portion 4a and the second detachable end portion 4b, it is possible to form an annular iron core in which the first to 14th basic links 40-1 to 40-14 are closed in an annular shape. The first basic link 40-1 to the 14th basic link 40-14 are all connected by unifying the directions of the uniaxial joints in the vertical direction, so that the first basic link 40-1 to the 14th basic link are connected. The rotation direction of 40-14 can be restricted horizontally. As described above, if the rotation direction of the first basic link 40-1 to the 14th basic link 40-14 is restricted in the horizontal direction, the connection between the first attachment / detachment end portion 4a and the second attachment / detachment end portion 4b can also be performed. It can be done almost in the horizontal plane.

On the other hand, the coil holding tube 5 holds a coil by using a flexible tube as a coil bobbin. Specifically, the magnet wire 521 is wound around the outer peripheral surface of the inner layer tube 51 to form the inner coil 52 and covered with the middle layer tube 53, and the magnet wire 541 is wound around the outer peripheral surface of the middle layer tube 53 to form the outer coil 54. The coil body 55 is formed. Then, by covering the outer surface of the coil body 55 (the surface on which the outer coil 54 is formed) with the insulating outer layer tube 54, the coil holding tube 5 is formed.

The inner layer tube 51, the middle layer tube 53, and the outer layer tube 56 have flexibility and insulation that can be reasonably deformed following the deformation of the connecting core 4. The inner layer tube 51 has an inner space portion 51b into which the connecting core 4 can be inserted, and has a length that allows the first attachment / detachment end portion 4a and the second attachment / detachment end portion 4b of the connection core 4 to be exposed from each end portion. Is. The inner layer tube 53 and the outer layer tube 56 are also set to have the same length, and each end is covered with an insulating cap 57. From one of the coil holding tubes 5, the inner first leader wire 521a and the inner second leader wire 521b, which are the winding start portion or the winding end portion of the magnet wire 521 constituting the inner coil 51, are pulled out. Similarly, the outer first leader wire 541a and the outer second leader wire 541b, which are the winding start portion or winding end portion of the magnet wire 541 constituting the outer coil 54, are pulled out.

Next, the detailed structure of the basic link 40 constituting the connecting core 4 will be described. FIG. 3 shows the appearance of the basic link 40 which is a connecting prime field. The basic link 40 is a plate material (for example, a thickness of 1 [mm]) of a high magnetic permeability soft magnetic material (for example, permalloy), that is, a first base material 41-1, a second base material 41-2, ..., No. 1 It has a structure in which 6 base materials 41-6 and 7th base materials 41-7 are laminated. In a state where the first base material 41-1 to the seventh base material 41-7 are stacked, they are integrally fixed by the rivet 42 of the caulking fixing method. The first to seventh base materials 41-1 to 41-7 all have the same shape, and are simply referred to as the base material 41 when there is no particular need to distinguish them.

FIG. 4 shows a plane surface of the base material 41 (for example, a surface facing the upper surface 41a). The base material 41 is a long plate material having a gentle arc shape, and is generally an outer arc-shaped edge portion 411 and an inner arc-shaped edge portion 412 which are two sides in the longitudinal direction, and a convex end edge portion 413 which is two sides in the lateral direction. And a concave edge portion 414. For example, assuming an arc of R160 [mm] from the virtual origin O (hereinafter referred to as a virtual center arc), an arc separated from the virtual center arc by about 3.5 [mm] (for example, R163.5 from the origin O). The outer arc-shaped edge portion 411 is formed so as to overlap with the arc (of [mm]). Further, the inner arc-shaped edge portion 412 is formed so as to overlap the arc (for example, the arc of R156.5 [mm] from the origin O) separated from the inside of the virtual center arc by about 3.5 [mm]. Further, the convex end edge portion 413 is provided on one short side of the base material 41 (for example, the left side when viewed from the upper surface 41a or the right side when viewed from the lower surface 41b). Further, the concave end edge portion 414 is provided on the other short side of the base material (for example, the right side when viewed from the upper surface 41a or the left side when viewed from the lower surface 41b). The separation distance between the outer arc-shaped edge portion 411 and the inner arc-shaped edge portion 412 is about 7 [mm] (3.5 [mm] × 2), and the first to seventh base materials 41-1 to 41-7 are used. Since the stacked thickness is also about 7 [mm], the vertical cross section of the basic link 40 in the lateral direction is substantially square.

On the virtual center arc of the base material 41, a first fixing hole 415a, a second fixing hole 415b, and a third fixing hole 415c of φ2 [mm] are provided, respectively. For example, the angle from the origin O to the center of the first fixing hole 415a and the angle from the origin O to the center of the third fixing hole 415c are the same with respect to the virtual line passing through the center of the second fixing hole 415b from the origin O. The opening positions of the first to third fixing holes 415a to 415c are determined so as to be. In this way, when the two base materials 41 are stacked so that the upper surface 41a and the lower surface 41b face each other (when the convex end edge portion 413 and the concave end edge portion 414 are overlapped so as to be opposite to each other). ), All three holes in the two stacked base materials 41 can be matched. That is, when the two base materials 41 are aligned so that the respective second fixing holes 415b communicate with each other, the first fixing holes 415a and the third fixing holes 415c in one base material 41 become the other base material 41. It overlaps with the third fixing hole 415c and the first fixing hole 415a in. At this time, in the two stacked base materials 41, the outer arc-shaped edge portion 411 and the inner arc-shaped edge portion 412 can also be kept in the same state.

Therefore, when the basic link 40 has a structure in which a plurality of (for example, 7) base materials 41 are stacked, the orientations of the base materials 41 can be alternately changed and stacked as shown in FIG. First, the second base material 41-2 with the lower surface 41b facing upward is placed under the first base material 41-1 with the upper surface 41a facing upward. A third base material 41-3 with the upper surface 41a facing upward is layered beneath it. A fourth base material 41-4 with the lower surface 41b facing upward is layered beneath it. A fifth base material 41-5 with the upper surface 41a facing upward is layered beneath it. A sixth base material 41-6 with the lower surface 41b facing upward is layered beneath it. A seventh base material 41-7 with the upper surface 41a facing upward is layered beneath it. The rivet 42 is inserted into the first to third fixing holes 415c penetrating from the first base material 41-1 to the seventh base material 41-7 and fixed by caulking. As shown in FIG. 6, in the rivet 42, the head portion 42a is positioned on the upper surface 41a side of the first base material 41-1 and the shaft portion 42b is inserted into the first to third fixing holes 415a to 415c. , A crimped portion 42c is formed on the lower surface 41b side of the seventh base material 41-7.

The first and second connecting portions 40a and 40b in the basic link 40 formed by laminating the first to seventh base materials 41-1 to 41-7 as described above are both convex end edge portions 413 and concave. The edge portions 414 are alternately overlapped. The first connecting portion 40a has a structure of "concavo-convex unevenness" from the first base material 41-1 to the seventh base material 41-7, and the second connecting portion 40b is formed from the first base material 41-1. The structure becomes "convex, uneven, uneven, uneven" toward the seventh base material 41-7. That is, the first connecting portion 40a and the second connecting portion 40b of the basic link 40 have a fitting structure in which they mesh with each other.

Moreover, the first connecting portion 40a and the second connecting portion 40b of the basic link 40 are connected by the uniaxial joint connecting portion 43 so as to have a convex end edge so as to be a uniaxial joint that can rotate smoothly. The protruding shape of the portion 413 and the recessed shape of the concave end edge portion 414 are set as follows.

A communication hole 416 for connecting by the uniaxial joint connecting portion 43 is provided on the convex end edge portion 413 side of the base material 41. The position of the communication hole 416 is determined so that the arc having a radius r1 substantially overlaps the bulging edge of the convex end edge portion 413 from the center of the communication hole 416 (see each convex end edge portion 413 in FIG. 5). Further, when the two basic links 40 are overlapped in the opposite directions, the arc having a radius r2 from the center of the communication hole 416 adjacent to the concave end edge portion 414 overlaps with the recessed edge of the concave end edge portion 414 (for example). , Each concave edge 414 in FIG. 5). At this time, if "r1 ≦ r2" is set, all the communication holes 416 are in a state where one first connecting portion 40a and the other second connecting portion 40b in the pair of basic links 40 are meshed with each other. The opening position can be adjusted.

In the design of the base material 41 described above, assuming that the convex end edge portion 413 and the concave end edge portion 414 both have an arcuate range close to 180 °, the first connecting portion 40a and the second connecting portion 40a of the pair of basic links 40 are connected. It becomes impossible to rotate while being engaged with the portion 40b. Therefore, it is desirable to appropriately set the arc-shaped range of the convex end edge portion 413 and the concave end edge portion 414 according to the allowable rotation range. It is desirable that the convex edge portion 413 and the concave edge portion 414 have an outer edge shape that is smoothly connected to the outer arc-shaped edge portion 411 and the inner arc-shaped edge portion 412, respectively. If there is a step or acute angle at the connection portion between the convex end edge portion 413 and the concave end edge portion 414 and the outer arc-shaped edge portion 411 and the inner arc-shaped edge portion 412, the connecting core 4 is inserted into the coil holding tube 5. At that time, there is a risk of damaging the inner surface of the inner layer tube 51.

However, in the base material 41 of the connecting core 4 used in the clamp sensor 2 of the present embodiment, the width in the lateral direction (the separation distance between the outer arc-shaped edge portion 411 and the inner arc-shaped edge portion 412) is approximately r1 [mm] ×. It is 2. Therefore, when the arcuate range of the convex end edge portion 413 is set to approximately 180 °, the connection portion between one end of the convex end edge portion 413 and the outer arcuate edge portion 411 and the other end and the inner arc shape of the convex end edge portion 413 are formed. The connection portion with the edge portion 412 is smooth, and no step or the like is generated. On the other hand, chamfering (for example, R1) is applied to the connection portion between one end of the concave end edge portion 414 and the outer arc-shaped edge portion 411 and the connection portion between the other end of the concave end edge portion 414 and the inner arc-shaped edge portion 412. The shape is such that the connections are smooth so that no corners are formed.

Further, when the radius r1 for determining the convex end edge portion 413 and the radius r2 for determining the concave end edge portion 414 are equalized, when the first connecting portion 40a and the second connecting portion 40b of the pair of basic links 40 are connected, Depending on the processing accuracy, it may not be possible to align the opening position of the connecting port 416. Even if the processing accuracy is good and the opening positions of the connecting ports 416 are exactly the same even if "r1 = r2", the convex end edge portion 413 and the concave end edge portion 414 come into surface contact in a long range. If the convex end edge portion 413 and the concave end edge portion 414 are in surface contact with each other, the sliding resistance increases accordingly, which may make the deformation work of the connecting core 4 difficult. However, if the radius r1 of the convex end edge portion 413 is made smaller than the radius r2 of the concave end edge portion 414, the first connecting portion 40a and the second connecting portion 40b are engaged with each other. The facing area is reduced. If the facing area between the first connecting portion 40a and the second connecting portion 40b is reduced, the magnetic resistance at the connecting portion between the base materials 41 may be increased, and the strength at the connecting portion between the base materials 41 may be lowered. Problems are also a concern. Therefore, when the first connecting portion 40a and the second connecting portion 40b of the pair of basic links 40 are engaged, the convex end edge portion 413 and the concave end edge portion 414 are set to such a degree that they make point contact or not. It is desirable to keep it. For example, as shown in FIG. 4, when the radius r1 for determining the convex end edge portion 413 is set to 3.5 [mm] and the radius r2 for determining the concave end edge portion 414 is set to 3.6 [mm], the connection is made. There is no problem in the deformation work of the core 4, and the magnetic resistance does not increase extremely at the connecting portion.

FIG. 7 shows an example of a configuration of a uniaxial joint connecting portion 43 that connects a pair of basic links 40 having a first detachable end portion 4a and a second detachable end portion 4b configured as described above. The first connecting portion 40a and the second connecting portion 40b are engaged with each other to match the opening positions of the communication holes 416 in all the convex end edge portions 413, and the connecting screw 431 is inserted in this state. When the head of the connecting screw 431 is pressed against the upper surface 41a of the first base material 41-1, the screw tip of the 431 appropriately protrudes from the lower surface 41b of the seventh base material 41-7, so that the flat washer 432 and the spring washer It is inserted via a 433 and fastened with a nut 434.

At this time, if the nut 434 is tightened too tightly, smooth rotation between the basic links 40 is hindered, and conversely, if the tightening is too weak, it becomes difficult to maintain the shape of the connecting core 4 itself. Therefore, the clamp sensor 2 The work when clamping the conductor to be measured becomes complicated. Therefore, it is also important to maintain an appropriate fastening state as a function of the uniaxial joint connecting portion 43. For example, after tightening the nut 434 to the connecting screw 431 with a predetermined tightening torque (for example, 1.8 [kgf · cm]), the nut 434 is returned 90 ° to loosen the nut 434 by a certain amount, and the screw lock agent is applied to the nut 434. 435 is applied and fixed in this tightened state. By doing so, it does not hinder the smooth rotation of the basic links 40 and does not make it difficult to maintain the shape of the connecting core 4 itself, so that the handling of the connecting core 4 in the measurement work is improved and the workability is improved. It can also contribute to improvement.

An example of a manufacturing process of the coil body 55 in which the inner coil 52 can be arranged on the outer periphery of the connecting core 4 described above will be described with reference to FIG. First, a flexible / insulating inner layer tube 51 having a cylindrical outer peripheral surface 51a is prepared. The inner layer tube 51 is provided with an inner space portion 51b having a diameter necessary and sufficient for inserting the connecting core 4, and the first connecting portion 40a and the second detachable end portion 4b of the connecting core 4 protrude from both end openings. Is the length of. Further, the inner layer tube 51 is fixed in a straight line by passing the linear metal rod 58 through the inner space portion 51b of the inner layer tube 51 (see FIG. 8A). By doing so, since the rigid metal rod 58 can be set in the shaft-rotating winding machine with the rotating shaft as the rotation axis, the magnet wire 521 is single-layered or multi-layered on the outer peripheral surface 51a of the inner layer tube 51 by the winding machine. The inner coil 52 can be formed by efficiently winding the coil (see FIG. 8 (b)).

After forming the inner coil 52 on the outer peripheral surface 51a of the inner layer tube 51, the middle layer tube 53 is covered so as to cover the inner coil 52, and the magnet wire 541 is wound in a single layer or multiple layers on the outer peripheral surface 53a of the middle layer tube 53. Go and form the outer coil 54 (see FIG. 8 (c)). After that, the inner layer tube 51 is removed from the winding machine and the metal rod 58 is pulled out (see FIG. 8D). In this way, a coil having a double structure consisting of an inner coil 52 formed by winding a magnet wire 521 on the outer surface of the inner layer tube 51 and an outer coil 54 formed by winding a magnet wire 541 on the outer surface of the middle layer tube 53. The body 55 is formed (see FIG. 8 (e)). The winding start portion and winding end portion of the magnet wire 521 and the magnet wire 541 are used as the inner first leader wire 521a and the inner second leader wire 521b, and the outer first leader wire 541a and the outer second leader wire 541b, respectively. be able to.

The coil body 55 formed as described above is inserted into the coil insertion portion 56a of the flexible / insulating outer layer tube 56 (see FIG. 9A) to the outside of the outer coil 54. The surface can be covered with the outer layer tube 56. The outer layer tube 56 has a length similar to that of the coil body 55, and the interpolating portion 56a inside the coil has a diameter necessary and sufficient for interpolating the coil body 55. After inserting the coil body 55 into the outer layer tube 56, insulating caps 57 for ensuring creepage distance are attached to both ends thereof to form the coil holding tube 5 (see FIG. 9B). Next, the connecting core 4 is inserted into the core insertion portion 5a of the coil holding tube 5 (same as the inner space portion 51b of the inner layer tube 51), and the first attachment / detachment end portions 4a and the second attachment / detachment end portions 4a and the second from both ends of the coil holding tube 5 are inserted. The detachable end portions 4b are exposed respectively. Thus, the clamp sensor 2 can be configured (see FIG. 9 (c)).

As shown in FIG. 9C, the first attachment / detachment end portion 4a and the second attachment / detachment end portion 4b are exposed to appropriate lengths at both ends of the clamp sensor 2. Therefore, the conductor to be measured is bent so as to be surrounded by the clamp sensor 2, and the first connecting portion 40a, which is the first attachment / detachment end portion 4a, and the second connecting portion 40b, which is the second attachment / detachment end portion 4b, are fitted and connected. The user may perform the work of making the core 4 into a ring-shaped iron core. However, it is not a very efficient work for the user to visually align the first connecting portion 40a and the second connecting portion 40b. Therefore, in the clamp sensor 2, a first connection guide 6 is provided on the side of the first attachment / detachment end portion 4a so that the first attachment / detachment end portion 4a and the second attachment / detachment end portion 4b can be efficiently fitted and removed. A second connection guide 7 is provided on the side of the second attachment / detachment end portion 4b. The attachment / detachment structure by the first connection guide 6 and the second connection guide 7 is not particularly limited, and a known and existing appropriate attachment / detachment structure may be adopted.

FIG. 10 shows an example of using the clamp meter 1 provided with the clamp sensor 2 configured as described above. The utility pole 9 can be clamped entirely by removing the first connection guide 6 and the second connection guide 7 of the clamp sensor 2 and connecting the first connection guide 6 and the second connection guide 7 while surrounding the utility pole 9. Therefore, the grounding current Ie and the leakage current Ir of the utility pole 9 can be easily measured. Moreover, unlike the Rogoski type clamp sensor, it is possible to measure a minute current of about 0.5 mA to 5 mA. Further, even when the three electric wires are separated from each other in the switchboard in the three-phase three-wire circuit, according to the clamp meter 1 according to the present embodiment, the three separated electric wires are collectively used by the clamp sensor 2. Since it can be clamped, it is possible to measure the minute leakage current in the circuit. Further, even if the three-phase three-wire thick lead-in wire is parallel to the utility pole, according to the clamp meter 1 according to the present embodiment, these lead-in wires can be collectively clamped and the minute leakage current can be measured. ..

When the conductor to be measured is clamped by the clamp sensor 2, the measured value corresponding to the current flowing through the conductor to be measured can be obtained from both the inner coil 52 and the outer coil 54. Moreover, since the number of turns of the inner coil 52 and the outer coil 54 are the same, the current value detected by the inner coil 52 and the current value detected by the outer coil 54 are substantially the same. Therefore, the measuring device 3 should be able to calculate an appropriate current value regardless of whether the detection value of the inner coil 52 or the detection value of the outer coil 54 is used.

However, since the clamp sensor 2 does not have a shielding function against an external magnetic field, if an external magnetic field in the measurement environment acts on the clamp sensor 2, the detected values of the inner coil 52 and the outer coil 54 will be different. The storage means 31 and the calculation means 32 are provided in the measuring device 3 as a function for correcting the measurement error due to such an external magnetic field and performing a highly accurate current measurement. Hereinafter, the principle of being able to correct the influence of an external magnetic field will be described with reference to FIG.

In FIG. 11, when the frequency and amplitude of the alternating current flowing through the conductor to be measured are constant and the magnitude of the acting external magnetic field (alternating current) is changed, the inner coil 52 and the outer coil 54 of the clamp sensor 2 are respectively. It is a characteristic diagram which showed the change of the detected current value. When no external magnetic field acts, the value of the current measured by the inner coil 52 (hereinafter referred to as the inner coil measured current) and the value of the current measured by the outer coil 54 (hereinafter referred to as the outer coil measured current) are both I. [A]. However, when the external magnetic field acts on the clamp sensor 2, the inner coil measured current value and the outer coil measured current value are increased by that amount.

When the external magnetic field acting on the clamp sensor 2 becomes stronger, both the inner coil measurement current and the outer coil measurement current increase, but the outer coil 54, which is closer to the external magnetic field, is more affected, so the outer side. The increase in coil measurement current becomes remarkable. Since the middle layer tube 53 having a constant thickness and the same material is interposed between the inner coil 52 and the outer coil 54, the sensitivity difference between the inner coil 52 and the outer coil 54 with respect to the external magnetic field is constant. That is, the value of the error caused in the inner coil 52 due to the influence of the external magnetic field (hereinafter referred to as the inner corrected current value Ia) and the value of the error caused in the outer coil 54 due to the influence of the external magnetic field (hereinafter referred to as the outer corrected current value Ib). ) Should have a predetermined relationship. Therefore, if an arithmetic expression showing the relationship between the two is specified, the influence of the external magnetic field can be eliminated and the current flowing through the conductor to be measured can be obtained with high accuracy.

For example, if the linearity is extremely strong as in the change characteristics of the inner coil measurement current and the change characteristics of the outer coil measurement current shown in FIG. 11, the inner correction current value Ia and the outer correction current value Ib are determined from the inclination ratios of the two. The relationship can be expressed by a simple arithmetic expression of the proportionality constant k. Even when the inner coil measurement current and the outer coil measurement current change non-linearly, since the sensitivity difference between the inner coil 52 and the outer coil 54 with respect to the external magnetic field is constant, a quadratic function, a cubic function, or the like can be used. It is possible to express the relationship between the two with the arithmetic expression used.

Here, consider the case where the magnitude of the external magnetic field is H [A / m]. The value of the inner coil measured current is IA, which is higher than the true measured value I [A] by the inner corrected current value Ia. That is, "IA = I + Ia". On the other hand, the value of the outer coil measured current is IB, which is higher than the true measured value I [A] by the outer corrected current value Ib. That is, "IB = I + Ib". However, since neither the inner correction current value Ia nor the outer correction current value Ib is unknown, the measured value I cannot be obtained directly from these relational expressions.

Therefore, attention is paid to the difference current value ΔI, which is the difference (IB-IA = Ib-IA) between the outer coil measured current value IB and the inner coil measured current value IA. Since the relationship between the inner corrected current value Ia and the outer corrected current value Ib can be expressed by an arithmetic expression, the relationship between the inner corrected current value Ia and the difference current value ΔI (= Ib-Ia) can also be expressed by an arithmetic expression. That is, the inner correction current value Ia is uniquely determined from the difference current value ΔI, and this calculation formula is set to “Ia = f (ΔI)”. Then, if the calculation formula of "Ia = f (ΔI)" determined according to the characteristics of the clamp sensor 2 is stored in the storage means 31 in advance, the calculation means 32 measures the outer coil measurement current value IB and the inner coil. The inner corrected current value Ia corresponding to the current value IA can be obtained.

The true measured value I can be obtained by subtracting the inner corrected current value Ia from the inner coil measured current value IA. Therefore, the calculation means 32 can obtain the true measured value I by performing the calculation of "IA-f (ΔI)", and the true measurement is performed in a predetermined calculation formula in consideration of the detection sensitivity due to the number of turns of the inner coil 52. By applying the value I, the current value flowing through the conductor to be measured can be obtained.

Since the outer correction current value Ib is also uniquely determined from the difference current value ΔI, the arithmetic expression to be stored in the storage means 31 is “Ib = f (ΔI)”, and the arithmetic means 32 is “IB−f (ΔI)”. The true measured value I may be obtained by performing the operation of. If the true measured value I is obtained, the current value flowing through the conductor to be measured can be obtained by applying the true measured value I to a predetermined arithmetic expression that takes into account the detection sensitivity due to the number of turns of the outer coil 54.

As described above, according to the clamp meter 1 according to the present embodiment, the characteristics of the clamp sensor 2 provided with the inner coil 52 and the outer coil 54 are utilized, and an error due to an external magnetic field is obtained from the inner coil measured current value and the outer coil measured current value. Can be corrected. Therefore, it is possible to suppress the influence of the external magnetic field on the clamp sensor 2 and obtain the current flowing through the conductor to be measured with high accuracy without using a metal shield or the like that hinders the enlargement and weight reduction of the clamp diameter. Clamp meter 1 can be provided.

In the clamp meter 1 of the present embodiment, the number of turns of the inner coil 52 and the outer coil 54 are matched to simplify the calculation formula for obtaining the inner correction current value or the outer correction current value. However, when the clamp sensor 2 must be created by changing the number of turns of the inner coil 52 and the outer coil 54, the detection sensitivity to the magnetic field change and the detection sensitivity to the external magnetic field of the connecting core 4 are different between the two coils. You cannot use the relatively simple arithmetic formula. Therefore, it is necessary to set a complicated calculation formula for obtaining the inner correction current value or the outer correction current value in consideration of the correction requirement for canceling the difference in the detection sensitivities of both coils. Alternatively, if an arithmetic expression is set to convert the number of turns of one coil to the number of turns of the other coil, the converted measured current value when the number of turns of the coils is the same can be obtained. The above-mentioned relatively simple arithmetic expression can be applied as it is.

The embodiment of the clamp sensor according to the present invention and the clamp meter using the clamp sensor has been described above with reference to the accompanying drawings. However, the present invention is not limited to this embodiment, and may be carried out by diverting known and existing equivalent technical means without changing the configuration described in the claims.

1 Clamp meter 2 Clamp sensor 3 Measuring device 31 Storage means 32 Computing means 4 Connecting core 4a 1st detachable end 4b 2nd detachable end 40 Basic link 40a 1st connecting 40b 2nd connecting 43 1 Axial joint connecting 5 Coil holding tube 5a Core inner cavity 51 Inner layer tube 52 Inner coil 521 Magnet wire 53 Middle layer tube 54 Outer coil 541 Magnet wire 55 Coil body 56 Outer layer tube

Claims (7)

A clamp sensor consisting of a connecting core that becomes an annular iron core that non-contactly surrounds the conductor to be measured by connecting both ends, and a coil body in which a coil can be arranged on the outer circumference of the connecting core.
The coil body has an inner space portion into which the connecting core can be inserted, and has a length that allows the first attachment / detachment end portion and the second attachment / detachment end portion of the connection core to be exposed from each end portion. An inner layer tube having flexibility that can be easily deformed according to the deformation of the core, an inner coil formed by winding a magnet wire around the outer surface of the inner layer tube, and an inner coil arranged so as to cover the outside of the inner coil. A middle layer tube and an outer coil formed by winding a magnet wire around the outer surface of the middle layer tube are provided.
The outer surface side of the coil body is covered with an insulating outer layer tube, the connecting core is inserted in the inner space of the coil body, and the current flowing through the conductor to be measured can be simultaneously detected by the inner coil and the outer coil. A clamp sensor characterized by the fact that The connecting core is made of a soft magnetic material having a high magnetic permeability, and a plurality of connecting prime fields having a first connecting portion and a second connecting portion formed at the pair of most separated ends are used, and the first connecting portions of each other are used. And the second connecting portion are connected so as to form a rotatable uniaxial joint to form a beaded connecting structure in which both ends are open, and the unconnected in the connecting prime field at one end. The first attachment / detachment end portion is used as the first attachment / detachment end portion, the unconnected second attachment / detachment end portion of the connecting element at the other end is used as the second attachment / detachment end portion, and the first attachment / detachment end portion and the second attachment / detachment end portion are provided. The clamp sensor according to claim 1, wherein all the connecting prime fields form an annular core that is closed in an annular shape by connecting the two. The connecting prime field of the connecting core is configured by laminating a plurality of base materials, which are plates of a high magnetic permeability soft magnetic material, so as to have a required thickness.
The base material has a convex end edge portion that protrudes in an arc shape equidistant from the axial position connected so as to form a uniaxial joint on one end side, and a circle having a curvature equivalent to that of the convex end edge portion. A concave end edge recessed in an arc shape shall be provided on the other end side, respectively.
By alternately laminating the convex end edge portion and the concave end edge portion of the base material to form the connecting prime field, the first connecting portion and the second connecting portion are mutually laminated with the convex end edge portion. The base material of each connecting prime field having a fitting structure in which the portion and the concave end edge portion are engaged with each other and connected by a uniaxial joint has the convex end edge portion and the concave end edge portion of each other. The clamp sensor according to claim 2, wherein the clamp sensor can rotate within a required range without interfering with each other. The clamp sensor according to any one of claims 1 to 3 is provided.
The inner coil measured current value and the outer coil measured current value detected from the inner coil and the outer coil of the clamp sensor are acquired, respectively, and the measured is performed based on the inner coil measured current value and the outer coil measured current value. A clamp meter characterized by being equipped with a measuring device that calculates the value of the current flowing through the conductor. The outer coil and the inner coil have the same number of turns , and when the clamp sensor is not affected by the external magnetic field, the inner coil measured current value and the outer coil measured current value are matched. The clamp meter according to claim 4. The measuring device is
From the difference current value, which is the difference between the outer coil measured current value and the inner coil measured current value acquired from the clamp sensor, an arithmetic formula for obtaining the inner corrected current value generated by the external magnetic field acting on the inner coil is obtained. A storage means to memorize and
The inner corrected current value is calculated using the calculation formula of the storage means, and the inner corrected current value is subtracted from the inner coil measured current value to obtain the true measured value by the clamp sensor, and the true measurement is performed . An arithmetic means for obtaining the current value flowing through the conductor to be measured from the value, and
The clamp meter according to claim 5, wherein the clamp meter is provided. The measuring device is
From the difference current value, which is the difference between the outer coil measured current value and the inner coil measured current value acquired from the clamp sensor, an arithmetic formula for obtaining the outer corrected current value generated by the external magnetic field acting on the outer coil is obtained. A storage means to memorize and
The outer corrected current value is calculated using the calculation formula of the storage means, and the outer corrected current value is subtracted from the outer coil measured current value to obtain the true measured value by the clamp sensor, and the true measurement is performed . An arithmetic means for obtaining the current value flowing through the conductor to be measured from the value, and
The clamp meter according to claim 5, wherein the clamp meter is provided.

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