JPH02118460A - Method and device for detecting current - Google Patents

Abstract

PURPOSE:To detect a current which penetrates a cylinder body by using a Rogowskii coil which is formed by winding a solenoid along the axial curve so that the means sectional area and the number of turns per unit length are constant. CONSTITUTION:The Rogowskii coil 1 of the detector K1 consists of a spool 12 which is formed on a flexible nonmagnetic material such as polystyrene in an annularly curved shape and the annular solenoid 3 which is wound annularly around the spool 2 so that the number of turns per unit length is constant and the mean sectional area is constant in the axial direction of the spool 2. Consequently, magnetic flux density which is substantially proportional to only the zero-phase component of the current to be detected is obtained in the opposite space from the current to be detected abut the magnetic material, so when, for example, the zero-phase current is detected, the zero-phase current which is <=1/200 a load current is detected as the output of the Rogowskii coil. Further, when a normal load current is detected, a fine load current which penetrates the cylinder body can be detected without being affected by the nonlinearity, etc., of an iron core.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a current detection method and a current detector.

[Prior Art] CT' has been proposed as a current detector, and an example of its application is a zero-sequence current detector (hereinafter referred to as ZCT). There is a problem with residual voltage. What is residual voltage?
Even if the three-phase load current or zero-phase component interlinked with 'T' is not included, the output is generated in the current transformer secondary winding as if it were included.

In Japan's high-resistance grounded power distribution system, even if a ground fault occurs, the ground fault current is small, and its zero-sequence current remains at a low level. Therefore, when trying to detect a zero-sequence current using ZCT, the residual voltage becomes noise, significantly deteriorating the S/N ratio, and making detection virtually impossible.
It is impossible with a general ZCT to detect a ground fault current level of about 200 Urr+A1 with respect to a load current of A].

In order to solve this problem, conventional Z CTs have been developed by winding a tape made of a good conductor such as copper or a magnetic material with high magnetic permeability over the negative winding, and by making the core magnetic path elliptical. In addition, the residual voltage is reduced by changing the number of turns of the secondary winding along the longitudinal direction of the core magnetic path. This actually reduces the residual voltage, and the iron core ZCT is actually used for zero-sequence current detection in power distribution systems.

However, the problem is that the proper way to wind the tape to reduce residual voltage, the desirable shape of the magnetic path, the necessary distribution of the secondary winding, etc. can only be obtained through trial and error and after gaining sufficient experience. there were.

This is considered to be because the cause of residual voltage generation is not necessarily clear physically or theoretically. Therefore, for example, it is difficult for power distribution equipment manufacturers to design and manufacture ZCTs based on general magnetic circuit theory, and it is inconvenient that they have to outsource this work to specialized manufacturers.

Furthermore, since it is impossible to open the magnetic path of the completed iron core ZCT, the work of assembling the ZCT to the distribution line becomes troublesome, and there are practical problems in that the locations where the ZCT can be assembled are limited. There were also points. Similar problems as described above occur in CT.

[Problems to be Solved by the Invention] This invention has been made to solve the conventional problems as described above, and in the case of zero-sequence current detection, it is possible to detect It is possible to accurately detect level currents, and its design and manufacture are based on general theory without relying on special know-how, and it can be easily installed on distribution lines. In the case of load currents such as , it is possible to detect minute load currents without being affected by unfavorable characteristics of the iron core, and furthermore, the 4
It is an object of the present invention to provide a current detection method that is flexible even in different locations.

Means for Solving the Problem] To achieve the above object, a first invention provides a cylinder formed of a magnetic material having a thickness such that a magnetizing current generated from a current to be detected is distributed virtually only on the surface. On the outside of the body, a Rogowski coil is wound around the solenoid along its axial center curve so that the average cross-sectional area and the number of turns per unit length are constant, and the coil penetrates into the inside of the segment. The gist of this is to detect the current to be detected.

The gist of the second invention is that the outer periphery of a Rogowski coil formed by winding a coil around a core material made of an insulator is covered with a magnetic case.

The gist of the third invention is that the core material of the Rogowski coil and the magnetic case are each made of flexible materials.

[Function] According to the research conducted by the present inventors, it is believed that the main cause of the residual voltage is that the magnetic flux density that rises above the ZCT iron core due to the normal load current is fixed in the magnetic path, resulting in non-uniformity. Iron cores are originally used for the purpose of eliminating such non-uniformity and creating a uniform magnetic flux density, and thus a constant magnetic flux, within the core magnetic path. However, due to nonlinearity of the core material, local magnetic saturation, magnetic flux density due to the image current on the core relative to the load current, and other factors, magnetic flux flows in and out from the sides of the magnetic path. Therefore, the magnetic flux linkage of the ZCT secondary winding is no longer directly proportional to the algebraic sum of the currents interlinked to the ZCT. This is considered to be the cause of residual voltage generation.

Therefore, in the present invention, the current is detected using a Rogowski coil based on Ampere's circuit integral theorem.

As is well known, this theorem can be written as follows: H is a magnetic field, C is an arbitrary closed curve, and ΣIt+ is a free current interlinking with C (supplied from an external circuit excluding the magnetizing current generated in the magnetic material).

This equation holds true regardless of the presence or absence of a magnetic medium and its type.

As a quantity proportional to the line integral in equation (1), the induced voltage of a ring solenoid, that is, a Rogowski coil, evenly wound in the axial direction of the coil is used. The cross-sectional area of the coil is S, and the vacuum permeability is μ. , the normal vector to the area S is n(//df
fi), the magnetic flux in S is μ.・If S is small enough to be considered old, the induced voltage in the Rogowski coil will be. However, n is the number of turns per unit length in the axial direction of the coil, μ. is the vacuum permeability. From equations (1) and (2), the algebraic sum of currents linked to the coil is given by: By integrating the induced voltage V over time, the algebraic sum of the currents can, in principle, be determined. When the current is a sinusoidal alternating current, ■ and its time integral are also sinusoidal, and the current value is proportional to ■. In such a case, if only the relative value of the current is required, or if it is possible to calibrate the absolute value of the current separately, the time integration in (2) can be omitted.

However, if the Rogowski coil described above is attached to a three-phase load current while being exposed, the residual voltage will be large and low-level zero-phase current detection will occur, as is the case with iron-core ZCTs that are not wrapped with silver tape or magnetic tape. is not possible.

Therefore, in the present invention, a cylinder made of a magnetic material is further interposed between the current to be detected and the Rogowski coil so as to surround this current. Furthermore, this cylinder includes a ring-shaped magnetic case made of double cylinder elements and their ends closed with magnetic material, and a Rogowski coil is housed in the ring-shaped magnetic case, and the current to be detected is applied to the hollow part of the gauge. It may be passed through.

If the magnetic permeability of such a magnetic material is high to a certain extent, magnetizing current will actually occur only on the surface of the magnetic material in the absence of zero-sequence current. This magnetizing current cancels the magnetic flux density generated inside the magnetic body due to the free current, and is generated so that the magnetic flux density in that part becomes zero or a significantly small value (a magnetic field H is generated due to the free current inside the magnetic material).As a result, If the cylinder or cylinder has an annular magnetic material case shape and has an axially symmetrical shape or a shape that does not significantly deviate from the axially symmetrical shape without severe unevenness, the current to be detected with respect to the magnetic material The magnetic flux density in the space on the opposite side becomes significantly uniform.

For example, if the body is an axisymmetric cylinder, the detected current whose algebraic sum is zero and the magnetic flux density generated by the magnetizing current on the inner surface of the cylinder cancel each other out, and a magnetic flux density is generated inside the outer surface of the cylinder. The magnetic current is distributed according to the current to be detected so that the current does not occur, and even if it occurs, its value is extremely small. In this way, when the algebraic sum of the current is zero, for example, the current to be detected or the three-phase load current, when there is no zero-phase flow, the magnetizing current on the outer surface of the cylinder becomes zero, and in the space where the Rogowski coil exists, Either no magnetic flux density occurs, or even if it does, its value is extremely small and does not change much in the longitudinal direction of the Rogowski coil.

Since the magnetic permeability of the space is sufficiently lower than that of the magnetic material, the magnetic flux density remaining in the space where the Rogowski coil is located is sufficiently lower than that inside the cylindrical magnetic material. The magnetic flux density remaining inside the magnetic material is due to the reason stated in the prior art section that the magnetic flux density remains within the circle F! of the magnetic material. : Considered to be considerably non-uniform in one direction.

When the current has a zero-sequence component, the magnetizing current corresponding to the zero-sequence component of the current is distributed in the form of a closed circuit over the inner and outer surfaces of the cylinder. This magnetizing current produces magnetic flux density within the magnetic material, but does not produce magnetic flux density in the space outside it.Therefore, in the space where the Rogoskill coil exists, there is virtually a magnetic flux density proportional to the zero-sequence current of the current to be detected. A magnetic flux density is generated. If the axial symmetry of the cylindrical body or the annular magnetic body case is somewhat disrupted, the magnetizing current associated with the non-zero phase component of the current to be detected may also be partially distributed on the outer surface of the cylindrical body. However, the magnetic flux density and non-uniformity caused by this magnetizing current on the outside of the cylinder are significantly smaller than the magnetic flux density and non-uniformity generated at the same position by the same current component when there is no cylinder, and the Rogowski coil The residual voltage generated is also small.

By combining the magnetic material and the Rogowski coil as described above, a low-level zero-sequence current of about a few tenths of the three-phase load current is detected.

If the current to be detected is not a three-phase load current but, for example, a single-phase load @ current, even a mild load current can be detected without being affected by the unfavorable properties of the magnetic material.

In addition, since the Rogoskill coil is in a magnetic case, it is not affected by disturbances such as external magnetic fields.

Furthermore, the shape of the current detector can be freely changed due to the flexible core material and case.

“Embodiment 1” A first embodiment embodying the present invention will be described below with reference to the drawings.

As shown in FIGS. 1 and 2, a Rogowski coil 1 in a current detector is connected to a winding frame 2 made of a flexible non-magnetic material such as polystyrene curved into an annular shape. On the other hand, the solenoid is constituted by an annular solenoid 3 which is wound in an annular shape so that the number of turns n per unit length is constant and the average cross-sectional area S is constant along the axial direction of the winding frame 2. In addition, the average cross section! By making ffS as small as possible and increasing the number of turns n per unit length, the solenoid 3
It is desirable to increase the output voltage.

The lead wire 4a of the annular solenoid 3 is connected to the core wire of a coaxial cable 5 for measurement, and the lead wire 4b is connected to its outer conductor. The outer surface of the annular solenoid 3 is covered with an electrostatic shield 7, and the electrostatic shield 7 is connected to the outer conductor of the coaxial cable 5.

Note that if the annular solenoid 3 is wound only in one direction of the toroidal direction, for example, in the direction of the arrow A in FIG.
The induced voltage due to the magnetic flux interlinking with the axial center curve of the annular solenoid 3 is also added to the output of the annular solenoid 3, causing an error. In order to eliminate this, it is necessary to wind the annular solenoid 3 in an even number of layers, half of which are wound in the direction of the A arrow, and the remaining half of the layers are wound in the direction of the anti-A arrow. In the case of a single layer or an odd number of layers, a rewind line 6 is provided as shown in FIG. 3 to cancel the magnetic flux interlinking with the axial curve.

The cylindrical body 8, which is loosely inserted concentrically with respect to the Rogowski coil 1, is formed into a cylindrical shape from a magnetic material such as soft iron, and the thickness of the cylindrical body 8 depends on the magnetic permeability of the magnetic material. It is set so that the magnetizing current is distributed virtually only on the surface of the cylindrical body 8. In this example, the thickness is 31II! It is said that the amount of

It is preferable that the axis and length of the cylindrical body 8 be set to be at least several times the cross-sectional diameter of the Rogowski coil 1. If the axial length of the cylindrical body 8 is the above-mentioned value, the Rogowski coil 1 is arranged so as not to be far away from the outer peripheral surface of the cylindrical body 8. Then, the @ wire to be measured is inserted into the insertion hole 10 provided at the axis of the cylinder body 8,
The current flowing through the wire under test is detected.

Note that the winding frame 2 of the Rogowski coil 1 may be formed of a stamp material.

As a first modification of the current detector of the first embodiment, as shown in FIG. The windings of the double-ended Goski coil pieces 1a and lb are connected in series, and the winding frame 2 of the double-ended Goski coil pieces 1a and lb is formed.
It is also possible to form the Rogowski coil 1 by joining them in an annular shape.

In addition, in the modified examples or examples described below, for convenience of explanation, the same reference numerals are given to the same or equivalent components as those described in the above-mentioned first example or other examples,
The explanation will be omitted.

Further, as a second modification of the current detector 1, the windings of a pair of Rogowski coils 1 may be connected in series and closed to the cylinder body 8, as shown in FIG. In this way, it is possible to increase the output.

[Second example Next, a second embodiment will be described with reference to FIG.

The cylindrical body 8 of the current detector 2 has an elliptical cross-sectional shape, and the Rogowski coil 1 also has a cylindrical body 8 corresponding to this cylindrical body 8.
The Rogowski coil 1 is formed into an enlarged similar shape to the cylindrical body 8.
It is located not far from the outer circumferential surface of the

FIG. 7 shows a second modification of the current detector of the second embodiment,
The cylinder body 8 and the Rogowski coil 1 are formed into a racetrack shape. In this second embodiment, the cross-sectional shape of the cylinder 8 is formed so that it does not deviate significantly from an axially symmetrical circular shape, and its surface is formed so that there are no sharp irregularities.

[No. 0 actual example] Next, a third embodiment will be described with reference to FIGS. 8 and 9.

In this embodiment, the cylinder 8 of the current detector 8 is formed of a magnetic material such as soft iron into an annular cylinder case. That is, the cylindrical body 8 includes a first cylindrical body component 8a having an inner circumferential wall of the cylindrical body 8 and an inverted-shaped vertical cross section, and a second cylindrical body constituent member having an inverted curvature shape and an outer circumferential wall of the cylindrical body 8. 8b, and the two cylindrical rod constituent members 8a and 8b are removably connected to each other so as to form a storage space 11. Double cylinder rod component 8
a.

8F) is set to about 31 in this embodiment. A pair of Rogowski coils 1 electrically connected in series are housed in the storage space 11 in parallel.

A detected electric wire (not shown) is inserted into the insertion hole 10 of the cylindrical body 8.

FIG. 10 shows a first modification of the current detector of the third embodiment, in which the cylinder 8 is formed into an annular cylinder case whose planar shape is racetrack-shaped.

That is, the cylindrical body 8 has a racetrack-like planar shape and consists of a first cylindrical member 8a and a second cylindrical member 8b, both end surfaces of which are removably connected with magnetic material. The Rogowski coil 1 differs from the previous embodiment only in that its planar shape is formed into a racetrack shape similar to the cylindrical body 8 so that it is housed within the cylindrical body 8. Note that this planar shape is formed so that the cross-sectional shape of the cylinder 8 does not significantly deviate from the axially symmetrical circular shape, and the surface thereof is formed so that there are no sharp irregularities, as in the modification of the second embodiment. It is something to do.

Although not shown, the planar shape of the cylinder 8 and the Rogowski coil 1 may be oval as in the second embodiment.

FIG. 11 shows a third modification of the current detector of the third embodiment.

In this modification, the cylinder 8 is formed into an annular magnetic case with a circular cross section. That is, the cylinder 8 is constituted by a second cylinder component member 8a, 8b having a circular cross section and a semicircular planar shape, and a second cylinder component member 8a, 8b.
, 8b are connected together in an annular shape by joining flanges 12 to each other and tightening nuts 14 to connecting bolts 13 inserted through the flanges 12. The Rogowski coil 1 is housed in the housing space 11 of the cylindrical body 8.

Now, among the above-mentioned embodiments, 3 is selected as the second modification of the first embodiment and the current detector Kl of the third embodiment, and the operation thereof will be explained.

FIG. 12 shows a simulated three-phase distribution line, and one end of the simulated distribution line is connected to a three-phase power supply E through a three-phase slider SD. The other end of the simulated three-phase distribution line is connected to a balanced Y-type load resistor R, and is also grounded from the load side neutral point N via a variable grounding resistor VR.

On the other hand, one phase on the secondary side of Sliduc SD is the switch SW.
A ground fault can be caused by the ground fault wire F via the ground fault wire F.

In addition, due to the current capacity of the circuit, each phase of the simulated three-phase distribution line is constructed with a three-turn circuit to increase the maximum current value used.

For this simulated distribution line, a t-current detector Kl, 3 is attached to the t-current detector Kl, and in the 0-current detector Kl, 3, a simulated three-phase distribution line as a conductor of the current to be detected is inserted into the insertion hole 10 of the cylinder body 8. A pair of Rogowski coils 1 are installed outside the cylindrical body 8 of the current detector 1 and inside the storage space 11 of the current detector 3.
are arranged in series connection. The outputs of the three Rogosugi coils 1 in each of the current detectors Kl are connected to a synchroscope SY via an amplifier AP.

In this simulated three-phase distribution line, now open the switch SW,
Let the ground fault current I flowing through the ground fault wire F be zero. In this state, the load current I flowing through the resistor R is
change. At this time, the output generated in the Rogowski coil 1 of each current detector Kl is the aforementioned residual voltage. The output amplified by the amplifier AP is read by the synchroscope SY, and the value is as shown in FIG.

As shown in Figure 13, when the current detector is 3 (marked with a * mark), the residual voltage is extremely small and does not depend on the load current I. This residual voltage ■r is likely due to electrostatic noise. Conceivable.

When the current detector is 1 (Δ mark), the residual voltage ■r is similarly small, but it tends to increase somewhat with the load current I. The thickness of the cylindrical body 8 is 2.5[
vn] (mouth seal), 2[11] (X
(marked), the residual voltage proportional to the load current increases as the thickness decreases.

This indicates that as the thickness of the cylinder 8 decreases, the magnetic shielding effect of the cylinder 8 on the magnetic flux density that generates a load current that does not include a zero-phase component weakens.

When this magnetic shielding effect is sufficient, the magnetizing current is distributed only in a portion that is considered to be virtually the surface with respect to the thickness of the cylindrical body 8. The statement "distributed only in the magnetic field" means the above-mentioned magnetizing current distribution. The thickness of the magnetic material at which it can be considered that the magnetizing current is virtually distributed over the surface is physically determined by the magnetic permeability of the magnetic material, and in practice it is determined by the difference between the load current and the minimum value of the zero-sequence current to be detected. Depends on the ratio. Therefore, the thickness of the cylindrical body 8 is not limited to about 3 [1] as in the embodiment of the present application.

On the other hand, when the Rogowski coil 1 is used as a comparative example under the same conditions, the residual voltage Vr is extremely large and the load is directly proportional to the current I.

Next, when the switch SW is turned on and the resistance VR is changed, the output voltages of the Rogowski coils 1a of the current detectors Kl and 3 become as shown in FIG. That is, tK
In the case of 1 in the detector and in the case of 3 in the current detector, at worst, the ground fault current ■.

From a small value of about 10 [mA], the output voltage of Rogowski coil 1 is substantially proportional to the ground fault @ current f, and the ground fault type 'a If is less than 1/2000 of the load current I. Detected with high accuracy. Although not shown in the graph, the thickness of the cylinder 8 of 1 is 25[n11, 2[l'I11] for the current detector.
] and decreases t, f, :: 4 CZ C, the minimum value of ground fault current that can be practically detected increases.

On the other hand, in the case of only the Rogowski coil L without the cylindrical body 8, the output V of the Rogowski coil 1 is not proportional to the ground fault current I, i.e., f, i.e., the zero-sequence current due to the large residual voltage. It shows a completely meaningless value, and zero-sequence current cannot be detected.

Since the current detector Kl, 3 is equipped with the cylindrical body 8, when there is no zero-sequence current, the first cylindrical body component 8a in the current detector 3 is covered A magnetization flow is generated on the inner surface, which is the detection load current side, so that the load current I cancels the magnetic flux density generated outside the inner surface. The sum of this magnetizing current over the inner surface is equal to the algebraic sum of the load current I passing through the cylinder 8.

If the load current has a zero-sequence component, the magnetizing current
Distributed in the form of a closed circuit on the outer surface. This magnetizing current either produces a magnetic flux density within the magnetic material of the cylinder 8, or does not produce any magnetic flux density outside the magnetic material. The magnetic flux density generated outside the cylindrical body 8 is only due to the zero-sequence component of the load current, and the output of the Rogowski coil 1 is proportional to this. When there is no zero-phase component in the negative R current I, the magnetizing current on the inner surface of the cylinder 8 is distributed so as to close at both end surfaces of the cylinder 8, and no magnetizing current is generated on the outside of the cylinder 8. As a result, if there is no zero phase component, no output is produced in the Rogowski coil 1. Constant load current 24
If the circumferential direction component of the magnetic flux density is measured along the outer periphery of the cylinder 8 while maintaining the position [A], the result will be as shown in FIG. 15. In addition,
Vp is the amplified output of magnetic probe MP. When the cylinder 8 is not present, Vp is large and changes drastically in the circumferential direction, but when the cylinder 8 is present, Vp is extremely small over the entire area of O. This may be due to the presence of the cylinder 8 or the residual This shows that it is effective in removing voltage.

Although the cylindrical body 8 described above is formed in one piece, it can also be formed into two halves in the axial direction and formed into a single cylindrical body when assembled to the conductor of the current to be detected.

In addition, in an embodiment in which the cylinder body 8 is formed in a somewhat asymmetrical shape, there is a possibility that a magnetic flux density related to the non-zero phase component of the detected object of 1k 2m will occur in the Rogowski coil 1, but even if it occurs, The size and non-uniformity are small, and according to the principle of the Rogowski coil 1, no output related to such magnetic flux density appears in the Rogowski coil 1, and due to the expansion of the cross section of the Rogowski coil 1. Even if it appears, its value is small and has the advantage that only the zero-sequence current can be detected correctly.

Although each of the embodiments described above was intended to detect zero-sequence current, it can be understood that the present invention is also effective as a current detector for detecting not only zero-sequence V& current but also fault currents such as short circuits.

[Fourth example] Next, a fourth embodiment will be described with reference to FIGS. 16 to 19.

As shown in Fig. 16.17, the Rogowski coil 1 of 4 in the current detector is made of a flexible non-magnetic material such as polystyrene, and attached to the winding frame 2, as in the previous embodiment. The solenoid is constituted by an annular solenoid 3 wound in an annular manner so that the number of turns n per unit length is constant and the average cross-sectional area S is constant along the axial direction of the winding frame 2.

The Rogowski coil 1 has a cylindrical projection 15 formed protrudingly formed on one end surface of the winding frame 2 and inserted into an insertion hole 16 formed on the other end surface, so that the entire Rogowski coil 1 is curved into a track shape. Also, tape 1 is placed around the outer circumference of Rogowski coil 1.
7 is wound around and the annular solenoid 3 is fixed thereby.

Spacers 18 are fixed to the Rogowski coil 1 at predetermined intervals, and the outer periphery of the Rogowski coil 1 in this state is covered with a cylindrical case 19 made of a magnetic material such as a leg. Therefore, the spacer 18 holds the Rogowski coil 18 at a central position with respect to the axial direction of the case 19.

The case 19 is made of knitted Mi wire and has flexibility.

As shown in FIG. 19, the spacer 18 is a pair of spacer pieces 18a obtained by dividing a ring in which a circular through hole 21 is formed into two halves having the same shape.

18b, supporting portions 20a and 20b that hold the case 19 and the Rogowski coil 1 apart, and the through hole 2.
Sandwiching parts 21a and 21b that sandwich the Rogowski coil 1 and extending from the inner circumferential surface of the coil 1;
It is comprised of flanges 22a and 22b that connect both ends of b and supporting parts 20a and 20b.

Further, the flanges 22a, 22b are provided with through holes 23, and screws 24 are inserted into the through holes 23 to assemble and fix the pair of spacer pieces 18a, 18b, so that the clamping portions 21a, 21b can be secured. The Rogowski coil 1 is clamped.

Coupling fittings 25 made of a magnetic material such as iron are fastened to both ends of the case 19 by binding bands 26 so as to be flush with the end surface of the winding frame 2.

The coupling fitting 25 includes a cylindrical portion 27 fixed to the case 19, two storage portions formed through a locking step portion 28 having a larger diameter than the cylindrical portion 27, and a cylindrical portion 27 formed in an overhang on the circumference thereof. It is configured with a fixed flange 30.

The fixing flange 30 is formed with four through holes 31 arranged at 90 degree intervals, and the screws 32 that are not inserted through the through holes 31 are tightened to the nuts 33 to tightly connect the coupling fittings 25 to each other. It's like -λ. Further, a locking protrusion 34 is formed to protrude from the inner circumferential surface of the storage portion 29 of the coupling fitting 25.

Further, a pull-out hole 36 is formed on the outer periphery of the cylindrical portion 27 of one coupling fitting 25 and communicates with the inside thereof.
The Rogowski coil 1 lead wires 4a and 4b are led out to the outside and connected to the coaxial cable 5, and the case 19 is shielded by the coaxial cable 5.

A locking member 3 is provided at each end of the Rogowski coil 1.
5 is fixed, and this locking member 35 is stored in the storage portion 29 of the coupling fitting 25.

As shown in FIG. 20, this locking member 35 consists of a pair of locking pieces 35a and 35b obtained by dividing a ring in which an insertion hole 38 is formed into two halves to have the same shape.
Locking plates 37a and 37b are abutted and locked to the locking step portion 28 of
and a support side wall 39a that protrudes to one side with respect to the locking plates 37a, 37b and is formed along the inner peripheral surface of the insertion hole 38.

39b, and mounting plates 40a and 40b that connect both ends of the supporting side walls 39a and 39b to the locking plates 37a and 37b. Also, the locking plate 37 of the locking piece 35a
A is formed with four parts 43 that engage with locking protrusions 34 formed in the storage part 29 of the coupling fitting 25.

Further, the mounting plates 40a, 40b are provided with through holes 41, and screws 42 are inserted into the through holes 41 to assemble and fix the pair of locking pieces 35a, 35b, thereby supporting the side wall 39a, At 39b, the end of the Rogowski coil 1 and the locking member 35 are fixed flush.

Therefore, by using a flexible material for the case 19 that covers the winding frame 2 and the Rogowski coil 1, the current detector 4 can be freely curved.

As a result, when attaching to power distribution equipment such as distribution lines and switches, it can be formed into a shape that suits the space of the installation location, making installation work easier without having to choose the 9R location. .

Further, by covering the Rogowski coil 1 with a single case made of a magnetic material, the 'rh current can be accurately measured since there is no influence from external disturbances. In particular, when used as a zero-phase current transformer (Z CT ), the output current due to disturbances can be reduced, so even minute ground fault currents can be detected.

Furthermore, because the spacer 18 and the locking member 35 allow the Rogowski coil 1 to be always placed in the center of the case 19 (the place least affected by external disturbances), the current flowing through the distribution line can be accurately measured. be able to.

In this embodiment, in order to arrange the Rogowski coil 1 in the center of the case 19, the spacer 18 and the locking member 35
However, it is also possible to interpose urethane or the like between the Rogowski coil 1 and the case 19.

Note that the present invention is not limited to the above-mentioned embodiments, and can be arbitrarily modified without departing from the spirit of the present invention.

[Effects of the Invention] As described in detail above, the present invention provides a method in which a solenoid is connected to the outside of a cylindrical body formed of a magnetic material having a thickness such that the magnetizing current generated by the current to be detected is distributed virtually only on the surface. Rogowski carp is wound in a ring along its axial curve so that the average cross-sectional area and the number of turns per degree length are constant.
By detecting the current to be detected passing through the inside of the cylindrical body with the cylindrical member, the space on the opposite side of the magnetic material from the to-be-detected t'a is virtually proportional to only the zero-sequence component of the current to be detected. For example, when detecting zero-sequence current, the output of the Rogowski coil is 1/20 of the load current.
It has the revolutionary advantage of being able to detect zero-sequence currents of 00 or less, and when detecting normal load currents, it is possible to detect minute load currents without having to worry about iron core nonlinearity, etc., as in conventional methods. Can be done. Moreover, since the detection of the current to be detected is based on the well-known Ampere's circuit integral theorem and the magnetizing current in a physically clear magnetic material, it does not require any special know-how and is well-known in the field. This has the advantage that engineers can easily design and manufacture current detectors.

Furthermore, according to the current detection method of the present invention, the Rogowski coil can be separated from the cylindrical body even in the finished product stage, unlike the finished product ZCT in which the iron core and the secondary winding are inseparable. Each member can be divided into two parts along the direction of the conductor of the current to be detected. Therefore, it becomes easy to attach the current detector to the distribution line, and the current detector can be attached to other locations than the distribution line, such as inside and outside of an air switch or a waste switch.

Furthermore, by covering the Rogowski coil with a case made of a magnetic material, the current flowing through the power distribution line etc. can be accurately measured since there is no influence from external disturbances.

Furthermore, by forming the case covering the core material and the Rogowski coil from a flexible material, the current detector can be freely curved. As a result, when attached to power distribution equipment such as distribution lines and switches, it can be formed into a shape that suits the space at which it is installed.
Installation work can be made easier without having to choose the location.

[Brief explanation of drawings]

1 to 3 show a first embodiment, FIG. 1 is a partially cutaway front view of the zero-phase current detector of the first embodiment embodying the present invention, and FIG. 2 is a side view of the same. Figure 3 is a plan view of the Rogowski coil, Figures 4 and 5 each show a modification of the first embodiment, Figure 4 is a front view of the Rogowski coil piece, and Figure 5 is a current detection 6 is a plan view of the current detector of the second embodiment, FIG. 7 is a front view of the current detector of a modification of the third embodiment, and FIGS. 8 and 9 are the views of the third embodiment. Fig. 8 is a partially cutaway front view of a current detector, Fig. 9 is an exploded partially cutaway front view of a case-shaped cylinder, and Fig. 10 is a partially cutaway front view of a third embodiment. FIG. 11 is a longitudinal sectional view of an Si detector showing another modification of the third embodiment; FIG. 12 is a partially cutaway front view of a current detector showing a modification; FIG. An explanatory diagram showing a state in which a current detector is attached to a simulated three-phase distribution line, Fig. 13 shows the rl! between load current and residual voltage. Fig. 14 is a graph showing the relationship between the ground fault current and the Rogowski coil output, and Fig. 15 (a) is a graph showing the magnetic flux density outside the cylinder of the first embodiment. 15 ([]) is a graph showing the distribution of magnetic flux density outside the cylinder of the first embodiment,
16 to 20 show the fourth embodiment, FIG. 16 is an enlarged sectional view of the current detector, FIG. 18 is an enlarged perspective view of the coupling fitting, and FIG. 19 is the Rogowski coil inside the case. FIG. 20 is an enlarged perspective view of a spacer that supports the spacer at the center, and FIG. 20 is an enlarged perspective view of the locking member. 1... Rogowski coil, 2... Winding frame, 3... Annular solenoid, 8... Cylindrical body, 19... Case 4 Patent applicant Energy Support Hayashi Shiki Company Agent Patent attorney On 1 ) Hironobu (and 1 other person) Figure 13 Figure 14 Figure 15 (ra) Hiromu 151)

Claims (1)

[Claims] 1. A solenoid is placed on the outside of a cylindrical body made of a magnetic material having a thickness such that the magnetizing current generated by the current to be detected is distributed only on the surface thereof, along the axial center curve of the cylindrical body. A current detection method characterized by detecting a detected current passing through the inside of a cylinder of a Rogowski coil which is wound in an annular manner so that the average cross-sectional area and the number of turns per unit length are constant. 2. A current detector characterized in that the outer periphery of a Rogowski coil formed by winding a coil around a core material made of an insulator is covered with a magnetic case. 3. The current detector according to claim 2, wherein the core material of the Rogowski coil and the magnetic case are each made of a flexible material.