WO2018055664A1 - Three-phase through-type current transformer - Google Patents

Three-phase through-type current transformer Download PDF

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Publication number
WO2018055664A1
WO2018055664A1 PCT/JP2016/077650 JP2016077650W WO2018055664A1 WO 2018055664 A1 WO2018055664 A1 WO 2018055664A1 JP 2016077650 W JP2016077650 W JP 2016077650W WO 2018055664 A1 WO2018055664 A1 WO 2018055664A1
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WIPO (PCT)
Prior art keywords
phase
current transformer
type current
gap
current
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PCT/JP2016/077650
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French (fr)
Japanese (ja)
Inventor
誠治 片岡
知英 岩澤
真人 米田
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株式会社 東芝
東芝エネルギーシステムズ株式会社
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Application filed by 株式会社 東芝, 東芝エネルギーシステムズ株式会社 filed Critical 株式会社 東芝
Priority to PCT/JP2016/077650 priority Critical patent/WO2018055664A1/en
Priority to JP2018540248A priority patent/JP6571290B2/en
Publication of WO2018055664A1 publication Critical patent/WO2018055664A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
    • G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
    • G01R15/18—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F38/00—Adaptations of transformers or inductances for specific applications or functions
    • H01F38/20—Instruments transformers
    • H01F38/38—Instruments transformers for polyphase ac
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02B—BOARDS, SUBSTATIONS OR SWITCHING ARRANGEMENTS FOR THE SUPPLY OR DISTRIBUTION OF ELECTRIC POWER
    • H02B13/00—Arrangement of switchgear in which switches are enclosed in, or structurally associated with, a casing, e.g. cubicle
    • H02B13/02—Arrangement of switchgear in which switches are enclosed in, or structurally associated with, a casing, e.g. cubicle with metal casing
    • H02B13/035—Gas-insulated switchgear

Definitions

  • the embodiment of the present invention relates to a three-phase through-type current transformer that converts the magnitude of a current of each phase of a three-phase alternating current.
  • a current transformer is a device that is used for current detection and converts the magnitude of the current.
  • a through-type current transformer is conventionally known.
  • the through-type current transformer includes an annular core through which a single-phase conductor penetrates and a secondary winding wound around the annular core, and the conductor functions as a primary winding by at least one turn of the annular core.
  • the magnitude of the current input to the primary winding is converted according to the winding ratio of the primary winding to the secondary winding, and the magnitude of the current converted from the secondary winding is converted to the secondary winding. Is output to the device connected to.
  • a three-phase through type current transformer that converts the magnitude of a three-phase alternating current is known.
  • a three-phase through-type current transformer is a current transformer constructed by housing three through-type current transformers in a single case, and a single-phase conductor is placed on the annular core of each through-type current transformer. It penetrates as a primary winding.
  • the external magnetic field generated by a large current flowing in one phase does not magnetize the other two-phase annular cores uniformly, but locally magnetizes them.
  • the induced current increases due to partial saturation of.
  • the magnetic flux changes from the residual magnetic flux as a starting point, so that the induced current increases rapidly depending on the phase of the voltage when the current is applied. Therefore, in order to suppress the induced current, it is necessary to suppress the influence of the external magnetic field and the residual magnetic flux.
  • Embodiments of the present invention have been made to solve the above-described problems, and an object of the present invention is to provide a three-phase through-type current transformer that can suppress an induced current.
  • the three-phase feedthrough current transformer of the present embodiment has three feedthrough current transformers that convert the magnitude of a single-phase current in a single container.
  • This is a phase through current transformer and has the following configuration.
  • the through-type current transformer includes an annular core in which a single-phase conductor passes through a hole, and a secondary winding wound around the annular core.
  • the annular core has a first gap provided at a location where the magnetic saturation occurs due to a magnetic field generated by an accident current flowing through the conductor passing through the other annular core, and an equidistant position based on the location. And a second gap provided in the structure.
  • (A) is sectional drawing of the three-phase penetration type current transformer which concerns on 3rd Embodiment
  • (b) is a perspective view of the three-phase penetration type current transformer which concerns on 3rd Embodiment. It is sectional drawing of the three-phase penetration type current transformer which concerns on other embodiment. It is sectional drawing of the three-phase penetration type current transformer which concerns on other embodiment.
  • FIG. 1 is a cross-sectional view of a three-phase through current transformer according to this embodiment.
  • the present embodiment is a three-phase collective through-type transformer comprising three through-type current transformers 10a to 10c for converting the magnitude of a single-phase current and one containing body 3. It is a fluency.
  • the through-type current transformers 10a to 10c have the same configuration, respectively, and the secondary windings (non-circular windings) wound around the outer circumferences of the annular cores 2a to 2b and the annular cores 2a to 2c so as to be evenly distributed. As shown).
  • the through-type current transformers 10a to 10c are connected to a protective relay via a secondary winding.
  • the annular cores 2a to 2c are magnetic bodies having an annular shape and have a hole in the center.
  • the conductors 1a to 1c through which a single-phase current flows pass through the center of the hole.
  • the accommodating body 3 is a bottomed cylindrical body made of a metal such as aluminum or iron and accommodates three through-type current transformers 10a to 10c.
  • the through-type current transformers 10a to 10c are arranged in the housing 3 so that the conductors 1a to 1c are located at the vertices of an equilateral triangle.
  • each of the annular cores 2a to 2c is disposed in the container 3 so that the center of the annular cores 2a to 2c is located at the apex of the regular triangle.
  • the annular cores 2a to 2c have nearest points P and Q (thick line portions in FIG. 1) that are the closest to the other two annular cores 2a to 2c. Note that openings are provided at both ends of the housing 3 for the conductors 1a to 1c to pass therethrough.
  • the annular cores 2a to 2c are provided with gaps 4a to 4c at locations where the magnetic saturation occurs due to the magnetic field generated by the accident current flowing through the conductors 1a to 1c passing through the other annular cores 2a to 2c.
  • Gaps 5a to 5c are provided at equal positions.
  • the gaps 4a to 4c and 5a to 5c are portions where the magnetic permeability decreases in the annular cores 2a to 2c.
  • the number of the gaps 4a to 4c and 5a to 5c is not particularly limited, and may be three or more. Here, two gaps are provided in each of the annular cores 2a to 2c.
  • the gaps 4a to 4c are provided between the closest points PQ of the annular cores 2a to 2c where the gap is provided and the other two annular cores 2a to 2c.
  • the gaps 4a to 4c are provided at the center position between the closest points PQ. It has been.
  • the gaps 5a to 5c are provided at positions facing the gaps 4a to 4c.
  • the gaps 5a to 5c are rotated by 180 ° around the centers of the annular cores 2a to 2c. In this embodiment, it is a position facing the center position between the closest points PQ. Therefore, for example, in the annular core 2a, the clockwise magnetic path length from the gap 4a to the gap 5b is equal to the counterclockwise magnetic path length.
  • each of the annular cores 2a to 2c is provided with only one gap 4a to 4c and one gap 5a to 5c, so that a total of two gaps are provided.
  • each of the annular cores 2a to 2c includes three You may make it provide the above gap.
  • FIG. 2 is a diagram showing a distribution of external magnetization generated when a large current flows in one phase in a conventional three-phase through current transformer. Note that no gap is provided in the annular cores 102a to 102c of the conventional three-phase through current transformer.
  • FIG. 3 is a diagram showing a distribution of an external magnetic field generated when a large current flows in one phase in the three-phase through current transformer according to the present embodiment.
  • the direction of the magnetic flux is reversed between the magnetic fluxes 8b and 8c in the inner part, which is the part closest to the conductor 1a, and the outer magnetic fluxes 9b and 9c in the opposite part, and a current difference generated by the magnetic flux 8b and the magnetic flux 9b.
  • the induced current flows through the conductors 1b and 1c due to the current difference generated by the magnetic flux 8c and the magnetic flux 9c.
  • the annular iron cores 2b and 2c are partially saturated, the excitation impedance rapidly decreases and the current increases. Therefore, even if the difference between the magnetic fluxes 8b and 9b and the magnetic fluxes 8c and 9c is small, the difference current increases and the induced current increases. Resulting in. In other words, if there is a residual magnetic flux in the annular cores 2b and 2c, the magnetic flux changes starting from the residual magnetic flux, so that the induced current increases depending on the phase of the voltage when the power is turned on.
  • the magnetic flux density is reduced by providing low magnetic permeability gaps 4a to 4c at locations where the magnetic flux density is increased to increase the magnetic resistance, and Gaps 5a to 5c are provided at positions facing the locations to balance the magnetic fluxes 8b and 9b with the magnetic fluxes 8c and 9c. If the gaps provided in the annular iron cores 2a to 2c are only the gaps 4a to 4c, the magnetic flux density of the magnetic fluxes 8b and 8c can be reduced by the gap, but the magnetic flux density of the magnetic fluxes 9b and 9c. Is not effective, and the balance of the magnetic flux in the annular cores 2b and 2c is lost, so that the induction current cannot be reduced.
  • the point where the magnetic flux density of the annular cores 2b and 2c is highest is the closest point P to the conductor 1a in the annular core 2b, and the closest point to the conductor 1a in the annular core 2c. Q. For this reason, it is desirable to provide the gap 4b at the nearest point P and the gap 4c at the nearest point Q.
  • a large current such as an accident current may flow not only in the conductor 1a but also in the conductors 1b and 1c.
  • the closest point P to the conductor 1b in the annular iron core 2c is the place where the magnetic flux density is the highest. Therefore, the gap 4c is preferably provided at the closest point P.
  • the gap 4c is provided between the closest point P and the closest point Q of the annular core 2c when a large current flows through any of the other conductors 1a and 1b when viewed from the through-type current transformer 10c.
  • the gap 4c is provided at the center position between the closest contacts PQ, and the magnetic flux density is reduced and the induced current is reduced regardless of whether a large current flows through the conductor 1a or a large current flows through the conductor 1b.
  • An effect can be obtained.
  • the induced current can be reduced by about 10% at the maximum of the conventional three-phase feedthrough current transformer, and there is almost no influence on the error characteristics.
  • the three-phase feedthrough current transformer of this embodiment is a three-phase feedthrough in which three feedthrough current transformers 10a to 10c for converting the magnitude of a single-phase current are housed in one container 3.
  • the through-type current transformers 10a to 10c are two-phase current transformers 10a to 10c in which single-phase conductors 1a to 1c are wound around the annular cores 2a to 2c and the annular cores 2a to 2c.
  • the annular cores 2a to 2c include gaps 4a to 4a provided at locations where they are magnetically saturated by a magnetic field generated by an accident current flowing in the conductors 1a to 1c passing through the other annular cores 2a to 2c. 4c and gaps 5a to 5c provided at equidistant positions with the relevant point as a base point.
  • the annular cores 2a to 2c are arranged so that the centers thereof are located at the vertices of equilateral triangles, and the gaps 4a to 4c are respectively the annular cores 2a to 2c provided with the gaps 4a to 4c.
  • the annular cores 2a to 2c and the other two annular cores 2a to 2c are provided between the closest points PQ, and the gaps 5a to 5c are provided at positions facing the gaps 4a to 4c.
  • the gaps 4a to 4c are provided at locations where magnetic saturation is most likely to occur, so that the magnetic flux density at the locations can be reduced, and an accident current flows by providing the gaps 5a to 5c at equidistant locations with the locations as base points.
  • the magnetic flux can be balanced so as to cancel out the same direction of the magnetic flux around the conductor, and the induced current can be reduced.
  • the gaps 4a to 4c are provided at the central position between the closest contacts PQ, and the gaps 5a to 5c are provided at positions facing the central position.
  • the central position between a closest point PQ of one annular core 2a to 2c and the other two annular cores 2a to 2c is any of the conductors 1a to 1c penetrating the other two annular cores 2a to 2c. Even when an accidental current flows, the magnetic flux density can be reduced. Accordingly, the magnetic flux density at the position can be reduced by providing the gaps 4a to 4c at the position.
  • the gaps 5a to 5c are provided at positions facing the center position, the magnetic flux in the annular cores 2a to 2c can be balanced. As a result, the induced current can be reduced even if an accident current flows through any of the conductors 1a to 1c.
  • the annular cores 2a to 2c are provided with only one gap 4a to 4c and one gap 5a to 5c.
  • the minimum number of gaps 4a to 4c and 5a to 5c are provided, it is possible to prevent the error characteristics of the three-phase through-type current transformer from deteriorating and to reduce the manufacturing cost for providing the gaps. It is possible to improve economy.
  • FIG. 4A is a cross-sectional view of the three-phase through current transformer according to the second embodiment
  • FIG. 4B is a perspective view of the three-phase through current transformer according to the second embodiment.
  • FIG. 1A and 4B in the present embodiment, a shielding plate 13 is provided in the housing 3 between the phases of the through-type current transformers 10a to 10c.
  • the shielding plate 13 is a Y-shaped plate.
  • the shape of the shielding plate 13 is a Y-shape here, and the plate portions that shield the through-type current transformers 10a to 10c of the shielding plate 13 are connected on the center side.
  • the shielding plate 13 is fixed to the wall surface of one end of the bottomed cylinder of the container 3 by welding, screw fastening, or the like.
  • the plate-like portion of the shielding plate 13 is located in the middle between the phases.
  • the shielding plate 13 does not necessarily have to be connected at the center side like the Y-shape, and as shown in FIG. 11, plate-like bodies 15a to 15c are respectively provided between the through-type current transformers 10a to 10c. It may be arranged.
  • the shielding plate 13 is made of a conductor having a conductivity of 35 ⁇ 10 6 S / m or more. Such a conductor can be configured as a metal such as aluminum, copper, or an aluminum alloy.
  • the shielding plate 13 has a thickness of 5 mm or more and a height that is at least that of the through-type current transformers 10a to 10c.
  • an eddy current 10 centered on the magnetic field 12 is generated by the external magnetic field 12 in the plate-like portion that separates the through-type current transformer 10b and the through-type current transformer 10c of the shielding plate 13, and the external magnetic field
  • the magnetic field 11 is generated in the direction to cancel 12, the influence of the external magnetic field 12 on the through-type current transformers 10 b and 10 c can be reduced, and the induced current generated from the influence of the ground fault current of the other phase is reduced. Can do. Similar effects can be obtained when a ground fault current flows through the conductors 1b and 1c.
  • FIG. 6 is a diagram showing the results of magnetic field analysis in the three-phase through current transformer (with a shield plate) of the present embodiment
  • FIG. 7 is a diagram of a conventional three-phase through current transformer (without a shield plate). It is a figure which shows the result of a magnetic field analysis. 6 and 7 show the results of magnetic field analysis when an accidental current of 40 kA is passed through the conductor 1a.
  • the annular cores 102a to 102c in FIG. 7 are not provided with the gaps 4a to 4c and 5a to 5c.
  • the gray coloring of the annular cores 2a to 2c in FIG. 6 and the annular cores 102a to 102c in FIG. 7 indicates the magnetic flux density, and the darker the color, the higher the magnetic flux density. It can be seen that the annular cores 2a to 2c in FIG. 6 are generally less colored than the annular cores 102a to 102c in FIG. 7, and the magnetic flux density is reduced.
  • FIG. 8 is a graph showing the relationship between the accident current and the induced current when the conductivity and thickness of the shielding plate 13 are changed.
  • the annular cores 2a to 2c have an outer diameter of 29 cm, an inner diameter of 19 cm, and a height of 10 cm.
  • the three-phase through-type current transformer has a diameter of 62 cm and a height H (see FIG. 4B) of 62 cm.
  • the height H is perpendicular to the diameter direction and is the size in the extending direction of the conductors 1a to 1c.
  • the conductivity, thickness, and material of the shielding plates of Examples 1 to 3 and Comparative Examples 1 to 3 shown in FIG. 8 are as follows.
  • Example 1 is copper having a conductivity of 60 ⁇ 10 6 S / m and a plate thickness of 8 mm
  • Example 2 is copper having a conductivity of 60 ⁇ 10 6 S / m and a plate thickness of 5 mm
  • Example 3 is An aluminum alloy having a conductivity of 35 ⁇ 10 6 S / m and a plate thickness of 5 mm.
  • Comparative Example 1 has no shielding plate
  • Comparative Example 2 has a conductivity of 60 ⁇ 10 6 S / m and copper with a plate thickness of 3 mm
  • Comparative Example 3 has a conductivity of 35 ⁇ 10 6 S / m, a plate It is a 3 mm thick aluminum alloy.
  • the heights of the shielding plates in Examples 1 to 3 and Comparative Examples 2 and 3 are equal to or higher than the through-type current transformer.
  • Comparative Example 2 having a thickness of 3 mm can prevent malfunction of the protective relay even when the accident current becomes 40 kA, as in Examples 1 to 3, but the shielding effect is weak and the partial saturation start current changes. There wasn't.
  • a shielding plate 13 is provided between the phases of the through current transformers 10a to 10c.
  • the shielding plate 13 is made of a conductor having a conductivity of 35 ⁇ 10 6 S / m or more, has a thickness of 5 mm or more, and has a height that is at least the height of the through-type current transformers 10a to 10c.
  • the shape of the shielding plate 13 is Y-shaped, but three shielding plates may be provided one by one between the phases. It is considered that the shield plate 13 having a higher conductivity and a larger area is more likely to cause a circulating current to flow through the shield plate 13 and has a higher canceling effect with respect to the external magnetic field. Even if they are not connected at the center as in the case of a letter, an effect equivalent to the effect of suppressing the induced current of the Y-shaped shielding plate 13 can be obtained.
  • the third embodiment will be described with reference to FIG.
  • the third embodiment is the same as the basic configuration of the first embodiment.
  • the third embodiment is a modification of the shielding plate 13 of the second embodiment.
  • only differences from the first embodiment and the second embodiment will be described, and the same parts as those in the first embodiment and the second embodiment will be denoted by the same reference numerals and detailed description thereof will be omitted. .
  • FIG. 9A is a cross-sectional view of the three-phase through current transformer according to the third embodiment
  • FIG. 9B is a perspective view of the three-phase through current transformer according to the third embodiment.
  • shielding cylinders 14a to 14c are provided instead of the shielding plate 13 of the second embodiment. That is, shielding cylinders 14a to 14c that cover the current transformers 10a to 10c are arranged around the through-type current transformers 10a to 10c.
  • the shielding cylinders 14a to 14c have a cylindrical shape, and the conductors 1a to 1c and the annular iron cores 2a to 2c are located inside the cylinder. Therefore, the through-type current transformers 10a to 10c are shielded from other phases.
  • the shielding cylinders 14a to 14c are made of a conductor having an electrical conductivity of 35 ⁇ 10 6 S / m or more, have a thickness of 5 mm or more, and a height that is higher than that of the through-type current transformers 10a to 10c.
  • the influence of the external magnetic field is a problem peculiar to the three-phase alternating current caused by the fact that the conductors 1a to 1c are three-phase collective and the distance between the conductors 1a to 1c is short, and according to this embodiment, it is effectively dealt with. be able to.
  • the first to third embodiments are based on the premise that the conductors 1a to 1c are arranged at the vertices of the equilateral triangle. As described above, the conductors 1a to 1c may be arranged in parallel on the same plane. In this case, the gaps 4a to 4c and 5a to 5c are provided on the same straight line.
  • the position of the gaps 4a and 4b is the place where the magnetic flux density is highest in the other phase, but the gaps 4a and 4b are provided at the places. Magnetic flux density can be reduced. Further, since the gaps 5a and 5b are provided at positions opposed to the gaps 4a and 4b, in other words, at the equidistant positions with respect to the positions of the gaps 4a and 4b, the magnetic fluxes in the same direction are canceled out in the respective annular cores 2a and 2b. The induced current can be reduced.
  • the gaps 5b and 4c become gaps provided at the magnetic saturation point, and the function of the gap provided in the annular core 2b is larger in any of the conductors 1a and 1c. It can be reversed by current flow.
  • the shielding plate 13 only needs to be positioned between the phases, and does not need to be provided in the middle between the conductors 1a to 1c.
  • the shielding plate 13 provided between the conductors 1a and 1b may not have the same distance between the conductor 1a and the conductor 1b.
  • the shielding plate 13 is Y-shaped, but may be T-shaped.

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  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
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Abstract

Provided is a three-phase through-type current transformer with which an induction current can be suppressed. The three-phase through-type current transformer comprises three through-type current transformers 10a to 10c that are contained in a single container 3 for converting the magnitude of single-phase current. The through-type current transformers 10a to 10c are provided with annular cores 2a to 2c having single-phase conductors 1a to 1c penetrating through holes therein, and secondary winding wires wound around the annular cores 2a to 2c. The annular cores 2a to 2c include gaps 4a to 4c provided at locations where magnetic saturation occurs due to a magnetic field generated by an accidental current that has flowed through the conductors 1a to 1c penetrating through the other annular cores 2a to 2c, and gaps 5a to 5c provided at equally arranged positions with respect to the locations as base points.

Description

三相貫通形変流器Three-phase through current transformer
　本発明の実施形態は、三相交流の各相の電流の大きさを変換する三相貫通形変流器に関する。 The embodiment of the present invention relates to a three-phase through-type current transformer that converts the magnitude of a current of each phase of a three-phase alternating current.
　変流器は、電流検出に用いられ、電流の大きさを変換する機器である。この変流器の種類として、従来から貫通形変流器が知られている。貫通形変流器は、単相の導体が貫通する環状鉄心と、当該環状鉄心に巻回された二次巻線とを備え、導体が環状鉄心を少なくとも１ターンして一次巻線として機能し、一次巻線に入力された電流の大きさが、一次巻線と二次巻線の巻線比に応じて変換され、二次巻線から変換された大きさの電流が、二次巻線に接続された機器に出力される。また、三相交流の電流の大きさを変換する三相貫通形変流器が知られている。三相貫通形変流器は、１つのケースに貫通形変流器を３つ収納して構成された変流器であり、各貫通形変流器の環状鉄心に、単相の導体がそれぞれ一次巻線として貫通してなる。 A current transformer is a device that is used for current detection and converts the magnitude of the current. As a type of this current transformer, a through-type current transformer is conventionally known. The through-type current transformer includes an annular core through which a single-phase conductor penetrates and a secondary winding wound around the annular core, and the conductor functions as a primary winding by at least one turn of the annular core. The magnitude of the current input to the primary winding is converted according to the winding ratio of the primary winding to the secondary winding, and the magnitude of the current converted from the secondary winding is converted to the secondary winding. Is output to the device connected to. Further, a three-phase through type current transformer that converts the magnitude of a three-phase alternating current is known. A three-phase through-type current transformer is a current transformer constructed by housing three through-type current transformers in a single case, and a single-phase conductor is placed on the annular core of each through-type current transformer. It penetrates as a primary winding.
特開平０５－１７５０６２号公報JP 05-175062 A
　従来の三相貫通形変流器において、当該変流器に保護継電器が接続されている場合、例えば一相に地絡電流相当の大電流が流れた際、この地絡電流により発生する外部磁界の影響で健全な二相に誘導電流が流れてしまい、保護継電器が誤動作する可能性がある。 In a conventional three-phase through-type current transformer, when a protective relay is connected to the current transformer, for example, when a large current corresponding to a ground fault current flows in one phase, an external magnetic field generated by the ground fault current As a result, an induced current flows in two healthy phases, and the protective relay may malfunction.
　特に、三相貫通形変流器において、一相に大電流が流れることにより発生する外部磁界は、他の二相の環状鉄心を均一に磁化させるのではなく、局所的に磁化させ、環状鉄心が部分飽和することで誘導電流が増加するという問題があった。また、環状鉄心に残留磁束がある場合、その残留磁束を起点に磁束が変化するため、電流投入時の電圧の位相によっては誘導電流が急増する。従って、誘導電流を抑制するためには、外部磁界の影響と残留磁束を抑制する必要があった。 In particular, in a three-phase through-type current transformer, the external magnetic field generated by a large current flowing in one phase does not magnetize the other two-phase annular cores uniformly, but locally magnetizes them. There is a problem that the induced current increases due to partial saturation of. Further, when there is a residual magnetic flux in the annular iron core, the magnetic flux changes from the residual magnetic flux as a starting point, so that the induced current increases rapidly depending on the phase of the voltage when the current is applied. Therefore, in order to suppress the induced current, it is necessary to suppress the influence of the external magnetic field and the residual magnetic flux.
　本発明の実施形態は、上記のような課題を解決するためになされたものであり、誘導電流を抑制することのできる三相貫通形変流器を提供することを目的とする。 Embodiments of the present invention have been made to solve the above-described problems, and an object of the present invention is to provide a three-phase through-type current transformer that can suppress an induced current.
　上記の目的を達成するために、本実施形態の三相貫通形変流器は、単相の電流の大きさを変換する貫通形変流器を１つの収容体に３つ収容してなる三相貫通形変流器であって、次の構成を有する。
（１）前記貫通形変流器は、単相の導体が孔を貫通する環状鉄心と、前記環状鉄心の周囲に巻回された二次巻線と、を備える。
（２）前記環状鉄心は、他の前記環状鉄心を貫通する前記導体に流れた事故電流により発生する磁界によって磁気飽和する箇所に設けられた第１のギャップと、前記箇所を基点に等配位置に設けられた第２のギャップとを含み構成されている。 In order to achieve the above object, the three-phase feedthrough current transformer of the present embodiment has three feedthrough current transformers that convert the magnitude of a single-phase current in a single container. This is a phase through current transformer and has the following configuration.
(1) The through-type current transformer includes an annular core in which a single-phase conductor passes through a hole, and a secondary winding wound around the annular core.
(2) The annular core has a first gap provided at a location where the magnetic saturation occurs due to a magnetic field generated by an accident current flowing through the conductor passing through the other annular core, and an equidistant position based on the location. And a second gap provided in the structure.
第１の実施形態に係る三相貫通形変流器の断面図である。It is sectional drawing of the three-phase penetration type current transformer which concerns on 1st Embodiment. 従来の三相貫通形変流器において、一相に大電流が流れたときに発生する外部磁化の分布を示す図である。In the conventional three-phase through type current transformer, it is a figure which shows distribution of the external magnetization which generate | occur | produces when a large current flows into one phase. 第１の実施形態に係る三相貫通形変流器において、一相に大電流が流れたときに発生する外部磁界の分布を示す図である。It is a figure which shows distribution of the external magnetic field which generate | occur | produces when a large current flows into one phase in the three-phase penetration type current transformer which concerns on 1st Embodiment. （ａ）は、第２の実施形態に係る三相貫通形変流器の断面図であり、（ｂ）は、第２の実施形態に係る三相貫通形変流器の斜視図である。(A) is sectional drawing of the three-phase penetration type current transformer which concerns on 2nd Embodiment, (b) is a perspective view of the three-phase penetration type current transformer which concerns on 2nd Embodiment. 第２の実施形態に係る三相貫通形変流器の作用を説明するための図である。It is a figure for demonstrating the effect | action of the three-phase penetration type current transformer which concerns on 2nd Embodiment. 第２の実施形態の三相貫通形変流器（遮蔽板あり）における磁界解析の結果を示す図である。It is a figure which shows the result of the magnetic field analysis in the three-phase penetration type current transformer (with a shielding board) of 2nd Embodiment. 従来の三相貫通形変流器（遮蔽板なし）における磁界解析の結果を示す図である。It is a figure which shows the result of the magnetic field analysis in the conventional three-phase penetration type current transformer (without a shielding board). 遮蔽板の導電率、厚みを変えた場合の事故電流と誘導電流との関係を示すグラフである。It is a graph which shows the relationship between the accident electric current at the time of changing the electrical conductivity and thickness of a shielding board, and an induced current. （ａ）は、第３の実施形態に係る三相貫通形変流器の断面図であり、（ｂ）は、第３の実施形態に係る三相貫通形変流器の斜視図である。(A) is sectional drawing of the three-phase penetration type current transformer which concerns on 3rd Embodiment, (b) is a perspective view of the three-phase penetration type current transformer which concerns on 3rd Embodiment. 他の実施形態に係る三相貫通形変流器の断面図である。It is sectional drawing of the three-phase penetration type current transformer which concerns on other embodiment. 他の実施形態に係る三相貫通形変流器の断面図である。It is sectional drawing of the three-phase penetration type current transformer which concerns on other embodiment.
［１．第１の実施形態］
　［１－１．構成］
　以下では、図１～図３を参照しつつ、本実施形態に係る三相貫通形変流器について説明する。図１は、本実施形態に係る三相貫通形変流器の断面図である。図１に示すように、本実施形態は、単相の電流の大きさを変換する３つの貫通形変流器１０ａ～１０ｃと、１つの収容体３と、を備えた三相一括貫通形変流器である。 [1. First Embodiment]
[1-1. Constitution]
Hereinafter, the three-phase through current transformer according to this embodiment will be described with reference to FIGS. 1 to 3. FIG. 1 is a cross-sectional view of a three-phase through current transformer according to this embodiment. As shown in FIG. 1, the present embodiment is a three-phase collective through-type transformer comprising three through-type current transformers 10a to 10c for converting the magnitude of a single-phase current and one containing body 3. It is a fluency.
　貫通形変流器１０ａ～１０ｃは、それぞれ同一の構成であり、環状鉄心２ａ～２ｂと、環状鉄心２ａ～２ｃの外周に全周等配となるように巻回された二次巻線（不図示）とを備える。貫通形変流器１０ａ～１０ｃは、本実施形態では、二次巻線を介して保護継電器と接続されている。環状鉄心２ａ～２ｃは、円環状形状を有する磁性体であり、中央に孔を有する。当該孔の中心部には、単相の電流が流れる導体１ａ～１ｃがそれぞれ貫通している。 The through-type current transformers 10a to 10c have the same configuration, respectively, and the secondary windings (non-circular windings) wound around the outer circumferences of the annular cores 2a to 2b and the annular cores 2a to 2c so as to be evenly distributed. As shown). In the present embodiment, the through-type current transformers 10a to 10c are connected to a protective relay via a secondary winding. The annular cores 2a to 2c are magnetic bodies having an annular shape and have a hole in the center. The conductors 1a to 1c through which a single-phase current flows pass through the center of the hole.
　収容体３は、例えばアルミニウムや鉄などの金属からなる、両端が有底の円筒体であり、３つの貫通形変流器１０ａ～１０ｃが収容される。図１に示すように、貫通形変流器１０ａ～１０ｃは、導体１ａ～１ｃが正三角形の頂点に位置するように収容体３内に配置されている。換言すれば、環状鉄心２ａ～２ｃの中心が正三角形の頂点に位置するようにそれぞれ収容体３内に配置されている。そのため、環状鉄心２ａ～２ｃには、他の２つの環状鉄心２ａ～２ｃと最も近接する箇所である最近接点Ｐ，Ｑ（図１中の太線部分）がある。なお、収容体３の両端には、導体１ａ～１ｃが貫通するための開口が設けられている。 The accommodating body 3 is a bottomed cylindrical body made of a metal such as aluminum or iron and accommodates three through-type current transformers 10a to 10c. As shown in FIG. 1, the through-type current transformers 10a to 10c are arranged in the housing 3 so that the conductors 1a to 1c are located at the vertices of an equilateral triangle. In other words, each of the annular cores 2a to 2c is disposed in the container 3 so that the center of the annular cores 2a to 2c is located at the apex of the regular triangle. For this reason, the annular cores 2a to 2c have nearest points P and Q (thick line portions in FIG. 1) that are the closest to the other two annular cores 2a to 2c. Note that openings are provided at both ends of the housing 3 for the conductors 1a to 1c to pass therethrough.
　環状鉄心２ａ～２ｃには、他の環状鉄心２ａ～２ｃを貫通する導体１ａ～１ｃに流れた事故電流により発生した磁界によって磁気飽和する箇所にギャップ４ａ～４ｃが設けられ、当該箇所を基点に等配位置にギャップ５ａ～５ｃが設けられている。ギャップ４ａ～４ｃ、５ａ～５ｃは、環状鉄心２ａ～２ｃにおいて透磁率の低下する部分である。ギャップ４ａ～４ｃ、５ａ～５ｃの数は、特に限定されるものではなく、３以上でも構わないが、ここでは、環状鉄心２ａ～２ｃにそれぞれ２つのギャップが設けられている。 The annular cores 2a to 2c are provided with gaps 4a to 4c at locations where the magnetic saturation occurs due to the magnetic field generated by the accident current flowing through the conductors 1a to 1c passing through the other annular cores 2a to 2c. Gaps 5a to 5c are provided at equal positions. The gaps 4a to 4c and 5a to 5c are portions where the magnetic permeability decreases in the annular cores 2a to 2c. The number of the gaps 4a to 4c and 5a to 5c is not particularly limited, and may be three or more. Here, two gaps are provided in each of the annular cores 2a to 2c.
　ギャップ４ａ～４ｃは、当該ギャップが設けられる環状鉄心２ａ～２ｃと他の２つの環状鉄心２ａ～２ｃの最近接点ＰＱ間に設けられ、本実施形態では、当該最近接点ＰＱ間の中央位置に設けられている。ギャップ５ａ～５ｃは、ギャップ４ａ～４ｃに対向する位置に設けられており、各環状鉄心２ａ～２ｃにおいて、ギャップ４ａ～４ｃを基点にすると、環状鉄心２ａ～２ｃの中心周りに１８０°回転した位置であり、本実施形態では、最近接点ＰＱ間の中央位置に対向する位置である。そのため、例えば、環状鉄心２ａにおいて、ギャップ４ａからギャップ５ｂまでの右回りの磁路長と左回りの磁路長は等距離となる。 The gaps 4a to 4c are provided between the closest points PQ of the annular cores 2a to 2c where the gap is provided and the other two annular cores 2a to 2c. In this embodiment, the gaps 4a to 4c are provided at the center position between the closest points PQ. It has been. The gaps 5a to 5c are provided at positions facing the gaps 4a to 4c. In each of the annular cores 2a to 2c, when the gaps 4a to 4c are used as a base point, the gaps 5a to 5c are rotated by 180 ° around the centers of the annular cores 2a to 2c. In this embodiment, it is a position facing the center position between the closest points PQ. Therefore, for example, in the annular core 2a, the clockwise magnetic path length from the gap 4a to the gap 5b is equal to the counterclockwise magnetic path length.
　本実施形態では、各環状鉄心２ａ～２ｃにギャップ４ａ～４ｃとギャップ５ａ～５ｃとをそれぞれ１つのみ設け、合計２つのギャップを設けるようにしたが、各環状鉄心２ａ～２ｃは、３つ以上のギャップを設けるようにしても良い。 In this embodiment, each of the annular cores 2a to 2c is provided with only one gap 4a to 4c and one gap 5a to 5c, so that a total of two gaps are provided. However, each of the annular cores 2a to 2c includes three You may make it provide the above gap.
［１－２．作用］
　本実施形態に係る三相貫通形変流器の作用について、図２及び図３を用いて説明する。図２は、従来の三相貫通形変流器において、一相に大電流が流れたときに発生する外部磁化の分布を示す図である。なお、従来の三相貫通形変流器の環状鉄心１０２ａ～１０２ｃには、ギャップが設けられていない。図３は、本実施形態に係る三相貫通形変流器において、一相に大電流が流れたときに発生する外部磁界の分布を示す図である。 [1-2. Action]
The operation of the three-phase through-type current transformer according to the present embodiment will be described with reference to FIGS. FIG. 2 is a diagram showing a distribution of external magnetization generated when a large current flows in one phase in a conventional three-phase through current transformer. Note that no gap is provided in the annular cores 102a to 102c of the conventional three-phase through current transformer. FIG. 3 is a diagram showing a distribution of an external magnetic field generated when a large current flows in one phase in the three-phase through current transformer according to the present embodiment.
　まず、従来の三相貫通形変流器では、導体１ａに事故電流などの大電流が流れると、図２に示すように、一相の導体１ａの周囲に外部磁界７が発生し、他の二相を貫通する。このとき、他の二相の環状鉄心２ｂ、２ｃは、通電相である導体１ａに最も近い部分及びその対向部の磁束密度が高くなり、その位置で部分飽和が起きやすくなる。このように部分飽和が生じると誘導電流が増加してしまう。 First, in a conventional three-phase through current transformer, when a large current such as an accident current flows through the conductor 1a, an external magnetic field 7 is generated around the one-phase conductor 1a as shown in FIG. It penetrates two phases. At this time, in the other two-phase annular cores 2b and 2c, the magnetic flux density of the portion closest to the conductor 1a which is the energized phase and the facing portion thereof is high, and partial saturation is likely to occur at that position. When partial saturation occurs in this way, the induced current increases.
　また、導体１ａに最も近い部分である内側部分の磁束８ｂ、８ｃと、その対向部分である外側の磁束９ｂ、９ｃとでは磁束の方向が逆になり，磁束８ｂと磁束９ｂによって発生した電流差、磁束８ｃと磁束９ｃによって発生した電流差で、各導体１ｂ、１ｃに誘導電流が流れる。また、環状鉄心２ｂ、２ｃが部分飽和すると励磁インピーダンスが急激に低下し、電流が増加するため、磁束８ｂ、９ｂと磁束８ｃ、９ｃの磁束の差がわずかでも差電流が大きくなり誘導電流が増加してしまう。つまり、環状鉄心２ｂ、２ｃに残留磁束があると、当該残留磁束を起点に磁束が変化するため、電源投入時の電圧の位相によっては誘導電流が増加してしまう。 In addition, the direction of the magnetic flux is reversed between the magnetic fluxes 8b and 8c in the inner part, which is the part closest to the conductor 1a, and the outer magnetic fluxes 9b and 9c in the opposite part, and a current difference generated by the magnetic flux 8b and the magnetic flux 9b. The induced current flows through the conductors 1b and 1c due to the current difference generated by the magnetic flux 8c and the magnetic flux 9c. Further, when the annular iron cores 2b and 2c are partially saturated, the excitation impedance rapidly decreases and the current increases. Therefore, even if the difference between the magnetic fluxes 8b and 9b and the magnetic fluxes 8c and 9c is small, the difference current increases and the induced current increases. Resulting in. In other words, if there is a residual magnetic flux in the annular cores 2b and 2c, the magnetic flux changes starting from the residual magnetic flux, so that the induced current increases depending on the phase of the voltage when the power is turned on.
　これに対し、本実施形態では、図３に示すように、磁束密度の高くなる箇所に低透磁率のギャップ４ａ～４ｃを設けて磁気抵抗を大きくすることで磁束密度を低減させ、かつ、当該箇所と対向する位置にギャップ５ａ～５ｃを設けて、磁束８ｂ、９ｂと磁束８ｃ、９ｃとをバランスさせている。仮に、環状鉄心２ａ～２ｃに設けられるギャップが、ギャップ４ａ～４ｃのみである場合、磁束８ｂ、８ｃの磁束密度は、当該ギャップにより低減することが可能であるが、磁束９ｂ、９ｃの磁束密度の低減には効果がなく、環状鉄心２ｂ、２ｃ内における磁束のバランスが崩れてしまうため、誘導電流の低減は期待できない。 On the other hand, in the present embodiment, as shown in FIG. 3, the magnetic flux density is reduced by providing low magnetic permeability gaps 4a to 4c at locations where the magnetic flux density is increased to increase the magnetic resistance, and Gaps 5a to 5c are provided at positions facing the locations to balance the magnetic fluxes 8b and 9b with the magnetic fluxes 8c and 9c. If the gaps provided in the annular iron cores 2a to 2c are only the gaps 4a to 4c, the magnetic flux density of the magnetic fluxes 8b and 8c can be reduced by the gap, but the magnetic flux density of the magnetic fluxes 9b and 9c. Is not effective, and the balance of the magnetic flux in the annular cores 2b and 2c is lost, so that the induction current cannot be reduced.
　なお、導体１ａに大電流が流れる場合、環状鉄心２ｂ、２ｃの磁束密度が最も高くなる箇所は、環状鉄心２ｂでは導体１ａとの最近接点Ｐであり、環状鉄心２ｃでは導体１ａとの最近接点Ｑである。このため、ギャップ４ｂは最近接点Ｐに設け、ギャップ４ｃは最近接点Ｑに設けることが望ましい。但し、事故電流などの大電流が流れるのは、導体１ａに限らず、導体１ｂ、１ｃにも流れる可能性がある。例えば、導体１ｂに大電流が流れる場合、環状鉄心２ｃにおいて、導体１ｂとの最近接点Ｐが、磁束密度が最も高くなる箇所となる。そのため、ギャップ４ｃは、最近接点Ｐに設けることが好ましい。 When a large current flows through the conductor 1a, the point where the magnetic flux density of the annular cores 2b and 2c is highest is the closest point P to the conductor 1a in the annular core 2b, and the closest point to the conductor 1a in the annular core 2c. Q. For this reason, it is desirable to provide the gap 4b at the nearest point P and the gap 4c at the nearest point Q. However, a large current such as an accident current may flow not only in the conductor 1a but also in the conductors 1b and 1c. For example, when a large current flows through the conductor 1b, the closest point P to the conductor 1b in the annular iron core 2c is the place where the magnetic flux density is the highest. Therefore, the gap 4c is preferably provided at the closest point P.
　このように、貫通形変流器１０ｃから見て、他の導体１ａ、１ｂのいずれに大電流が流れた場合でも、環状鉄心２ｃの最近接点Ｐと最近接点Ｑとの間にギャップ４ｃを設けることで、磁束密度の低減効果及び誘導電流の低減効果を得ることができる。本実施形態では、最近接点ＰＱ間の中央位置にギャップ４ｃを設け、導体１ａに大電流が流れた場合も、導体１ｂに大電流が流れた場合も、磁束密度の低減効果及び誘導電流の低減効果を得ることができる。本実施形態によれば、誘導電流は最大で従来の三相貫通形変流器の１０％程度低減することが可能であり、かつ、誤差特性への影響はほとんどない。 In this way, the gap 4c is provided between the closest point P and the closest point Q of the annular core 2c when a large current flows through any of the other conductors 1a and 1b when viewed from the through-type current transformer 10c. Thereby, the effect of reducing the magnetic flux density and the effect of reducing the induced current can be obtained. In the present embodiment, the gap 4c is provided at the center position between the closest contacts PQ, and the magnetic flux density is reduced and the induced current is reduced regardless of whether a large current flows through the conductor 1a or a large current flows through the conductor 1b. An effect can be obtained. According to the present embodiment, the induced current can be reduced by about 10% at the maximum of the conventional three-phase feedthrough current transformer, and there is almost no influence on the error characteristics.
［１－３．効果］
（１）本実施形態の三相貫通形変流器は、単相の電流の大きさを変換する貫通形変流器１０ａ～１０ｃを１つの収容体３に３つ収容してなる三相貫通形変流器であって、貫通形変流器１０ａ～１０ｃは、単相の導体１ａ～１ｃが孔を貫通する環状鉄心２ａ～２ｃと、環状鉄心２ａ～２ｃの周囲に巻回された二次巻線と、を備え、環状鉄心２ａ～２ｃは、他の環状鉄心２ａ～２ｃを貫通する導体１ａ～１ｃに流れた事故電流により発生する磁界によって磁気飽和する箇所に設けられたギャップ４ａ～４ｃと、当該箇所を基点に等配位置に設けられたギャップ５ａ～５ｃとを含み構成するようにした。 [1-3. effect]
(1) The three-phase feedthrough current transformer of this embodiment is a three-phase feedthrough in which three feedthrough current transformers 10a to 10c for converting the magnitude of a single-phase current are housed in one container 3. The through-type current transformers 10a to 10c are two-phase current transformers 10a to 10c in which single-phase conductors 1a to 1c are wound around the annular cores 2a to 2c and the annular cores 2a to 2c. And the annular cores 2a to 2c include gaps 4a to 4a provided at locations where they are magnetically saturated by a magnetic field generated by an accident current flowing in the conductors 1a to 1c passing through the other annular cores 2a to 2c. 4c and gaps 5a to 5c provided at equidistant positions with the relevant point as a base point.
　特に、本実施形態では、環状鉄心２ａ～２ｃは、その中心が正三角形の頂点に位置するようにそれぞれ配置され、ギャップ４ａ～４ｃは、当該ギャップ４ａ～４ｃが設けられる環状鉄心２ａ～２ｃの、当該環状鉄心２ａ～２ｃと他の２つの環状鉄心２ａ～２ｃとの最近接点ＰＱ間に設け、ギャップ５ａ～５ｃは、ギャップ４ａ～４ｃに対向する位置に設けるようにした。 In particular, in the present embodiment, the annular cores 2a to 2c are arranged so that the centers thereof are located at the vertices of equilateral triangles, and the gaps 4a to 4c are respectively the annular cores 2a to 2c provided with the gaps 4a to 4c. The annular cores 2a to 2c and the other two annular cores 2a to 2c are provided between the closest points PQ, and the gaps 5a to 5c are provided at positions facing the gaps 4a to 4c.
　これにより、最も磁気飽和が起きやすい箇所にギャップ４ａ～４ｃを設けるので当該箇所における磁束密度を低減できるとともに、当該箇所を基点に等配位置にギャップ５ａ～５ｃを設けることにより、事故電流が流れる導体を中心として同方向の磁束を打ち消し合うようにバランスさせることができ、誘導電流を低減させることができる。その結果、三相貫通形変流器が保護継電器に接続される場合には、当該保護継電器の誤動作を防止することができる。 As a result, the gaps 4a to 4c are provided at locations where magnetic saturation is most likely to occur, so that the magnetic flux density at the locations can be reduced, and an accident current flows by providing the gaps 5a to 5c at equidistant locations with the locations as base points. The magnetic flux can be balanced so as to cancel out the same direction of the magnetic flux around the conductor, and the induced current can be reduced. As a result, when the three-phase through type current transformer is connected to the protective relay, malfunction of the protective relay can be prevented.
（２）ギャップ４ａ～４ｃは、最近接点ＰＱ間の中央位置に設け、ギャップ５ａ～５ｃは、当該中央位置と対向する位置に設けるようにした。これにより、誘導電流の低減効果を得ることができる。特に、ある一つの環状鉄心２ａ～２ｃの、他の２つの環状鉄心２ａ～２ｃとの最近接点ＰＱ間の中央位置は、他の２つの環状鉄心２ａ～２ｃを貫通する導体１ａ～１ｃのいずれに事故電流が流れた場合でも、磁束密度を低減させることができる位置である。従って、当該位置にギャップ４ａ～４ｃを設けることで当該位置における磁束密度を低減させることができる。さらに、中央位置と対向する位置にギャップ５ａ～５ｃが設けられているので、環状鉄心２ａ～２ｃ内の磁束のバランスを取ることができる。これにより、誘導電流は、何れの導体１ａ～１ｃに事故電流が流れても誘導電流を低減させることができる。 (2) The gaps 4a to 4c are provided at the central position between the closest contacts PQ, and the gaps 5a to 5c are provided at positions facing the central position. Thereby, the effect of reducing the induced current can be obtained. In particular, the central position between a closest point PQ of one annular core 2a to 2c and the other two annular cores 2a to 2c is any of the conductors 1a to 1c penetrating the other two annular cores 2a to 2c. Even when an accidental current flows, the magnetic flux density can be reduced. Accordingly, the magnetic flux density at the position can be reduced by providing the gaps 4a to 4c at the position. Further, since the gaps 5a to 5c are provided at positions facing the center position, the magnetic flux in the annular cores 2a to 2c can be balanced. As a result, the induced current can be reduced even if an accident current flows through any of the conductors 1a to 1c.
（３）環状鉄心２ａ～２ｃは、ギャップ４ａ～４ｃとギャップ５ａ～５ｃをそれぞれ１つのみ設けるようにした。これにより、最小限の数のギャップ４ａ～４ｃ、５ａ～５ｃしか設けないので、三相貫通形変流器の誤差特性の悪化を防止することができるとともに、ギャップを設けるための製造コストを削減でき、経済性を向上させることができる。 (3) The annular cores 2a to 2c are provided with only one gap 4a to 4c and one gap 5a to 5c. As a result, since the minimum number of gaps 4a to 4c and 5a to 5c are provided, it is possible to prevent the error characteristics of the three-phase through-type current transformer from deteriorating and to reduce the manufacturing cost for providing the gaps. It is possible to improve economy.
［２．第２の実施形態］
　［２－１．構成］
　第２の実施形態は、図４～図８を用いて説明する。第２の実施形態は、第１の実施形態の基本構成と同じである。以下では、第１の実施形態と異なる点のみを説明し、第１の実施形態と同じ部分については同じ符号を付して詳細な説明は省略する。 [2. Second Embodiment]
[2-1. Constitution]
The second embodiment will be described with reference to FIGS. The second embodiment is the same as the basic configuration of the first embodiment. In the following, only differences from the first embodiment will be described, and the same parts as those in the first embodiment will be denoted by the same reference numerals and detailed description thereof will be omitted.
　図４（ａ）は、第２の実施形態に係る三相貫通形変流器の断面図であり、図４（ｂ）は、第２の実施形態に係る三相貫通形変流器の斜視図である。図４（ａ）及び図４（ｂ）に示すように、本実施形態では、収容体３内に、貫通形変流器１０ａ～１０ｃの相間に遮蔽板１３が設けられている。 FIG. 4A is a cross-sectional view of the three-phase through current transformer according to the second embodiment, and FIG. 4B is a perspective view of the three-phase through current transformer according to the second embodiment. FIG. As shown in FIGS. 4A and 4B, in the present embodiment, a shielding plate 13 is provided in the housing 3 between the phases of the through-type current transformers 10a to 10c.
　遮蔽板１３は、Ｙ字型形状の板状体である。遮蔽板１３の形状は、ここではＹ字型形状とし、遮蔽板１３の各貫通形変流器１０ａ～１０ｃを遮蔽する板部分が中心側で繋がる形状である。遮蔽板１３は、収容体３の有底円筒の一端部の壁面に、溶接やネジ締結等により固定されている。遮蔽板１３の板状部分は、ここでは、相間の真ん中に位置している。 The shielding plate 13 is a Y-shaped plate. The shape of the shielding plate 13 is a Y-shape here, and the plate portions that shield the through-type current transformers 10a to 10c of the shielding plate 13 are connected on the center side. The shielding plate 13 is fixed to the wall surface of one end of the bottomed cylinder of the container 3 by welding, screw fastening, or the like. Here, the plate-like portion of the shielding plate 13 is located in the middle between the phases.
　なお、遮蔽板１３は、Ｙ字型のように必ずしも中心側で繋がっている必要はなく、図１１に示すように、各貫通形変流器１０ａ～１０ｃ間に板状体１５ａ～１５ｃがそれぞれ配置されていても良い。 The shielding plate 13 does not necessarily have to be connected at the center side like the Y-shape, and as shown in FIG. 11, plate-like bodies 15a to 15c are respectively provided between the through-type current transformers 10a to 10c. It may be arranged.
　遮蔽板１３は、導電率が３５×１０６Ｓ／ｍ以上の導電体からなる。このような導電体としては、アルミニウム、銅、アルミニウム合金などの金属として構成することができる。遮蔽板１３は、その板厚が５ｍｍ以上であり、高さが貫通形変流器１０ａ～１０ｃの高さ以上である。 The shielding plate 13 is made of a conductor having a conductivity of 35 × 10 6 S / m or more. Such a conductor can be configured as a metal such as aluminum, copper, or an aluminum alloy. The shielding plate 13 has a thickness of 5 mm or more and a height that is at least that of the through-type current transformers 10a to 10c.
　［２－２．作用］
　本実施形態の三相貫通形変流器の作用について、図５～図８を用いて説明する。図５に示すように、導体１ａに例えば一線地絡電流が流れたとすると、導体１ａの周囲に外部磁界１２が発生し、遮蔽板１３の板部分を貫通する。そうすると、例えば、遮蔽板１３の貫通形変流器１０ｂと貫通形変流器１０ｃとを隔てる板状部分には、外部磁界１２によって当該磁界１２を中心とした渦電流１０が発生し、外部磁界１２を打ち消す方向に磁界１１が発生し、貫通形変流器１０ｂ、１０ｃへの外部磁界１２の影響を低減させることができ、他相の地絡電流の影響から発生する誘導電流を低減することができる。導体１ｂ、１ｃに地絡電流が流れた場合も同様の作用効果を得ることができる。 [2-2. Action]
The operation of the three-phase through current transformer of this embodiment will be described with reference to FIGS. As shown in FIG. 5, for example, when a one-line ground fault current flows through the conductor 1 a, an external magnetic field 12 is generated around the conductor 1 a and penetrates the plate portion of the shielding plate 13. Then, for example, an eddy current 10 centered on the magnetic field 12 is generated by the external magnetic field 12 in the plate-like portion that separates the through-type current transformer 10b and the through-type current transformer 10c of the shielding plate 13, and the external magnetic field The magnetic field 11 is generated in the direction to cancel 12, the influence of the external magnetic field 12 on the through-type current transformers 10 b and 10 c can be reduced, and the induced current generated from the influence of the ground fault current of the other phase is reduced. Can do. Similar effects can be obtained when a ground fault current flows through the conductors 1b and 1c.
　図６は、本実施形態の三相貫通形変流器（遮蔽板あり）における磁界解析の結果を示す図であり、図７は、従来の三相貫通形変流器（遮蔽板なし）における磁界解析の結果を示す図である。図６及び図７は、導体１ａに４０ｋＡの事故電流を流した場合の磁界解析の結果である。なお、図７の環状鉄心１０２ａ～１０２ｃには、ギャップ４ａ～４ｃ、５ａ～５ｃは設けられていない。図６の環状鉄心２ａ～２ｃ及び図７の環状鉄心１０２ａ～１０２ｃのグレーの着色は、磁束密度を示しており、色が濃くなる程、磁束密度が高いことを示している。図６の環状鉄心２ａ～２ｃは、図７の環状鉄心１０２ａ～１０２ｃに比べ、全体的に着色が薄まっており、磁束密度が低減していることが分かる。 FIG. 6 is a diagram showing the results of magnetic field analysis in the three-phase through current transformer (with a shield plate) of the present embodiment, and FIG. 7 is a diagram of a conventional three-phase through current transformer (without a shield plate). It is a figure which shows the result of a magnetic field analysis. 6 and 7 show the results of magnetic field analysis when an accidental current of 40 kA is passed through the conductor 1a. The annular cores 102a to 102c in FIG. 7 are not provided with the gaps 4a to 4c and 5a to 5c. The gray coloring of the annular cores 2a to 2c in FIG. 6 and the annular cores 102a to 102c in FIG. 7 indicates the magnetic flux density, and the darker the color, the higher the magnetic flux density. It can be seen that the annular cores 2a to 2c in FIG. 6 are generally less colored than the annular cores 102a to 102c in FIG. 7, and the magnetic flux density is reduced.
　図８は、遮蔽板１３の導電率、厚みを変えた場合の事故電流と誘導電流との関係を示すグラフである。環状鉄心２ａ～２ｃは、外径が２９ｃｍ、内径が１９ｃｍであり、高さが１０ｃｍである。三相貫通形変流器の大きさは、直径が６２ｃｍ、高さＨ（図４（ｂ）参照）が６２ｃｍである。なお、高さＨは、直径方向と直交し、かつ、導体１ａ～１ｃの延び方向の大きさである。図８に示す実施例１～３及び比較例１～３の遮蔽板の導電率、厚み、素材は次の通りである。実施例１は、導電率６０×１０６Ｓ／ｍ、板厚８ｍｍの銅であり、実施例２は、導電率６０×１０６Ｓ／ｍ、板厚５ｍｍの銅であり、実施例３は、導電率３５×１０６Ｓ／ｍ、板厚５ｍｍのアルミニウム合金である。比較例１は、遮蔽板なしであり、比較例２は、導電率６０×１０６Ｓ／ｍ、板厚３ｍｍの銅であり、比較例３は、導電率３５×１０６Ｓ／ｍ、板厚３ｍｍのアルミニウム合金である。なお、実施例１～３及び比較例２、３の遮蔽板の高さは貫通形変流器以上である。 FIG. 8 is a graph showing the relationship between the accident current and the induced current when the conductivity and thickness of the shielding plate 13 are changed. The annular cores 2a to 2c have an outer diameter of 29 cm, an inner diameter of 19 cm, and a height of 10 cm. The three-phase through-type current transformer has a diameter of 62 cm and a height H (see FIG. 4B) of 62 cm. The height H is perpendicular to the diameter direction and is the size in the extending direction of the conductors 1a to 1c. The conductivity, thickness, and material of the shielding plates of Examples 1 to 3 and Comparative Examples 1 to 3 shown in FIG. 8 are as follows. Example 1 is copper having a conductivity of 60 × 10 6 S / m and a plate thickness of 8 mm, Example 2 is copper having a conductivity of 60 × 10 6 S / m and a plate thickness of 5 mm, and Example 3 is An aluminum alloy having a conductivity of 35 × 10 6 S / m and a plate thickness of 5 mm. Comparative Example 1 has no shielding plate, Comparative Example 2 has a conductivity of 60 × 10 6 S / m and copper with a plate thickness of 3 mm, and Comparative Example 3 has a conductivity of 35 × 10 6 S / m, a plate It is a 3 mm thick aluminum alloy. The heights of the shielding plates in Examples 1 to 3 and Comparative Examples 2 and 3 are equal to or higher than the through-type current transformer.
　図８に示すように、比較例１、３は、事故電流が３５ｋＡ超を超えると、誘導電流により保護継電器が誤動作する可能性があるレベルを超えてしまう。特に、遮蔽板なしの比較例１では、事故電流が２５ｋＡ付近より誘導電流が増加、つまり部分飽和が始まっていく。これに対し、実施例１～３では、誘導電流の抑制効果が大きい。板厚が５ｍｍ以上、高さが貫通形変流器の高さ以上、導電率が３５×１０６Ｓ／ｍ以上の導電体からなる遮蔽板１３を設けた場合、環状鉄心２ａ～２ｃの部分飽和開始電流（図９では、事故電流２５ｋＡ）を１．２倍以上の裕度を持たせることができる。事故電流が４０ｋＡとなっても、保護継電器の誤動作を防止することができることが確認できる。一方、厚さが３ｍｍの比較例２は、実施例１～３と同様に、事故電流が４０ｋＡとなっても保護継電器の誤動作を防止できるが、遮蔽効果が弱く、部分飽和開始電流に変化がなかった。 As shown in FIG. 8, in Comparative Examples 1 and 3, when the accident current exceeds 35 kA, the level at which the protective relay may malfunction due to the induced current is exceeded. In particular, in Comparative Example 1 without the shielding plate, the induced current increases from around 25 kA, that is, the partial saturation starts. On the other hand, in Examples 1 to 3, the effect of suppressing the induced current is large. When the shielding plate 13 made of a conductor having a plate thickness of 5 mm or more, a height of a through-type current transformer or more and a conductivity of 35 × 10 6 S / m or more is provided, the portions of the annular cores 2a to 2c The saturation start current (accident current 25 kA in FIG. 9) can have a margin of 1.2 times or more. It can be confirmed that the malfunction of the protective relay can be prevented even when the accident current becomes 40 kA. On the other hand, Comparative Example 2 having a thickness of 3 mm can prevent malfunction of the protective relay even when the accident current becomes 40 kA, as in Examples 1 to 3, but the shielding effect is weak and the partial saturation start current changes. There wasn't.
　［２－３．効果］
　本実施形態に係る三相貫通形変流器は、貫通形変流器１０ａ～１０ｃの相間に、遮蔽板１３を設けた。遮蔽板１３は、導電率が３５×１０６Ｓ／ｍ以上の導電体からなり、厚みが５ｍｍ以上、高さが貫通形変流器１０ａ～１０ｃの高さ以上とした。これにより、導体１ａ～１ｃのいずれか一相に地絡電流などの大電流が流れて外部磁界が発生しても、遮蔽板１３に外部磁界を打ち消す磁界が発生するので、他相の貫通形変流器１０ａ～１０ｃへの外部磁界の影響を低減することができ、誘導電流の抑制効果を得ることができる。 [2-3. effect]
In the three-phase through current transformer according to the present embodiment, a shielding plate 13 is provided between the phases of the through current transformers 10a to 10c. The shielding plate 13 is made of a conductor having a conductivity of 35 × 10 6 S / m or more, has a thickness of 5 mm or more, and has a height that is at least the height of the through-type current transformers 10a to 10c. As a result, even if a large current such as a ground fault current flows in any one of the conductors 1a to 1c and an external magnetic field is generated, a magnetic field that cancels the external magnetic field is generated on the shielding plate 13. The influence of the external magnetic field on the current transformers 10a to 10c can be reduced, and the effect of suppressing the induced current can be obtained.
　本実施形態では、遮蔽板１３の形状をＹ字型としたが、３枚の遮蔽板を相間にそれぞれ１枚ずつ設けるようにしてもよい。遮蔽板１３の導電率が高く、その面積も広い方が当該遮蔽板１３に循環電流が流れやすく、外部磁界との打ち消し効果が高いと考えられるが、３枚の遮蔽板をバラバラに設け、Ｙ字のように中央で繋がっていなくても、Ｙ字型の遮蔽板１３の誘導電流の抑制効果と同等の効果を得ることができる。 In the present embodiment, the shape of the shielding plate 13 is Y-shaped, but three shielding plates may be provided one by one between the phases. It is considered that the shield plate 13 having a higher conductivity and a larger area is more likely to cause a circulating current to flow through the shield plate 13 and has a higher canceling effect with respect to the external magnetic field. Even if they are not connected at the center as in the case of a letter, an effect equivalent to the effect of suppressing the induced current of the Y-shaped shielding plate 13 can be obtained.
［３．第３の実施形態］
　［３－１．構成］
　第３の実施形態は、図９を用いて説明する。第３の実施形態は、第１の実施形態の基本構成と同じである。また、第３の実施形態は、第２の実施形態の遮蔽板１３の変形例である。以下では、第１の実施形態及び第２の実施形態と異なる点のみを説明し、第１の実施形態、第２の実施形態と同じ部分については同じ符号を付して詳細な説明は省略する。 [3. Third Embodiment]
[3-1. Constitution]
The third embodiment will be described with reference to FIG. The third embodiment is the same as the basic configuration of the first embodiment. The third embodiment is a modification of the shielding plate 13 of the second embodiment. In the following, only differences from the first embodiment and the second embodiment will be described, and the same parts as those in the first embodiment and the second embodiment will be denoted by the same reference numerals and detailed description thereof will be omitted. .
　図９（ａ）は、第３の実施形態に係る三相貫通形変流器の断面図であり、図９（ｂ）は、第３の実施形態に係る三相貫通形変流器の斜視図である。本実施形態では、第２の実施形態の遮蔽板１３に変えて、遮蔽筒１４ａ～１４ｃを設ける。すなわち、貫通形変流器１０ａ～１０ｃの周囲に当該変流器１０ａ～１０ｃを覆う遮蔽筒１４ａ～１４ｃが配置される。遮蔽筒１４ａ～１４ｃは、ここでは、円筒形状であり、当該円筒内部に導体１ａ～１ｃ及び環状鉄心２ａ～２ｃが位置するため、各貫通形変流器１０ａ～１０ｃは、他相から遮蔽される。遮蔽筒１４ａ～１４ｃは、導電率が３５×１０６Ｓ／ｍ以上の導電体からなり、厚みが５ｍｍ以上、高さが貫通形変流器１０ａ～１０ｃの高さ以上である。 FIG. 9A is a cross-sectional view of the three-phase through current transformer according to the third embodiment, and FIG. 9B is a perspective view of the three-phase through current transformer according to the third embodiment. FIG. In the present embodiment, shielding cylinders 14a to 14c are provided instead of the shielding plate 13 of the second embodiment. That is, shielding cylinders 14a to 14c that cover the current transformers 10a to 10c are arranged around the through-type current transformers 10a to 10c. Here, the shielding cylinders 14a to 14c have a cylindrical shape, and the conductors 1a to 1c and the annular iron cores 2a to 2c are located inside the cylinder. Therefore, the through-type current transformers 10a to 10c are shielded from other phases. The The shielding cylinders 14a to 14c are made of a conductor having an electrical conductivity of 35 × 10 6 S / m or more, have a thickness of 5 mm or more, and a height that is higher than that of the through-type current transformers 10a to 10c.
　［３－２．作用・効果］
　本実施形態の遮蔽筒１４ａ～１４ｃを設けることにより、第２の実施形態の作用効果に加えて、小型化及び低コスト化を図ることができる。すなわち、従来から、外部磁界の影響を低減させ、鉄心の部分飽和を抑制する方法として、貫通形変流器の相間距離の拡大、鉄心断面積の拡大、及びシールド巻線の追加などの方法が知られているが、これらの方法は、収納スペースを拡大させるものであり、大型化及び高コストであるという問題があったが、本実施形態によれば、三相貫通形変流器の小型化及び低コスト化を図ることができる。外部磁界の影響は、導体１ａ～１ｃが三相一括であり、導体１ａ～１ｃ間の距離が近いことから生じる三相交流特有の問題であり、本実施形態によれば、効果的に対応することができる。 [3-2. Action / Effect]
By providing the shielding cylinders 14a to 14c of the present embodiment, in addition to the effects of the second embodiment, it is possible to reduce the size and cost. That is, conventionally, as a method for reducing the influence of the external magnetic field and suppressing the partial saturation of the iron core, there are methods such as increasing the interphase distance of the through-type current transformer, increasing the cross-sectional area of the iron core, and adding a shield winding. Although known, these methods increase the storage space, and have the problems of large size and high cost. According to this embodiment, the three-phase through-type current transformer is small. And cost reduction can be achieved. The influence of the external magnetic field is a problem peculiar to the three-phase alternating current caused by the fact that the conductors 1a to 1c are three-phase collective and the distance between the conductors 1a to 1c is short, and according to this embodiment, it is effectively dealt with. be able to.
［４．その他の実施形態］
　本明細書においては、本発明に係る複数の実施形態を説明したが、これらの実施形態は例として提示したものであって、発明の範囲を限定することを意図していない。以上のような実施形態は、その他の様々な形態で実施されることが可能であり、発明の範囲を逸脱しない範囲で、種々の省略や置き換え、変更を行うことができる。これらの実施形態やその変形は、発明の範囲や要旨に含まれると同様に、請求の範囲に記載された発明とその均等の範囲に含まれるものである。 [4. Other Embodiments]
In the present specification, a plurality of embodiments according to the present invention have been described. However, these embodiments are presented as examples and are not intended to limit the scope of the invention. The above embodiments can be implemented in other various forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the invention described in the claims and equivalents thereof, as long as they are included in the scope and gist of the invention.
（１）他の実施形態としては、第１乃至第３の実施形態では、導体１ａ～１ｃが正三角形の各頂点に位置するように配置されていることを前提としたが、図１０に示すように、導体１ａ～１ｃが同一平面上に並列して平行するように配置されていても良い。この場合、ギャップ４ａ～４ｃ、５ａ～５ｃは、同一直線上に設けられる。 (1) As another embodiment, the first to third embodiments are based on the premise that the conductors 1a to 1c are arranged at the vertices of the equilateral triangle. As described above, the conductors 1a to 1c may be arranged in parallel on the same plane. In this case, the gaps 4a to 4c and 5a to 5c are provided on the same straight line.
　例えば、導線１ｃで事故電流相当の大きな電流が流れると、他相においてはギャップ４ａ、４ｂの位置が最も磁束密度が高くなる箇所であるが、当該箇所にギャップ４ａ、４ｂが設けられているので磁束密度を低下させることができる。さらにギャップ４ａ、４ｂに対向する位置、言い換えるとギャップ４ａ、４ｂの箇所を基点に等配位置にギャップ５ａ、５ｂを設けているので、各環状鉄心２ａ、２ｂ内に同方向の磁束を打ち消し合うようにバランスさせることができ、誘導電流を低減させることができる。 For example, when a large current corresponding to the accident current flows through the lead wire 1c, the position of the gaps 4a and 4b is the place where the magnetic flux density is highest in the other phase, but the gaps 4a and 4b are provided at the places. Magnetic flux density can be reduced. Further, since the gaps 5a and 5b are provided at positions opposed to the gaps 4a and 4b, in other words, at the equidistant positions with respect to the positions of the gaps 4a and 4b, the magnetic fluxes in the same direction are canceled out in the respective annular cores 2a and 2b. The induced current can be reduced.
　なお、導体１ａに事故電流相当の大きな電流が流れた場合、ギャップ５ｂ、４ｃが磁気飽和する箇所に設けられたギャップとなり、環状鉄心２ｂに設けたギャップの機能は導体１ａ、１ｃのいずれに大きな電流が流れるかで反転し得る。 When a large current corresponding to the accident current flows in the conductor 1a, the gaps 5b and 4c become gaps provided at the magnetic saturation point, and the function of the gap provided in the annular core 2b is larger in any of the conductors 1a and 1c. It can be reversed by current flow.
（２）第２の実施形態では、遮蔽板１３は、相間に位置していれば良く、導体１ａ～１ｃ間の真ん中に設けられる必要はない。例えば、導体１ａ、１ｂ間に設けられた遮蔽板１３は、導体１ａとの距離と導体１ｂとの距離が等しくなくても良い。また、第２の実施形態で遮蔽板１３はＹ字型形状としたが、Ｔ字型形状としても良い。 (2) In the second embodiment, the shielding plate 13 only needs to be positioned between the phases, and does not need to be provided in the middle between the conductors 1a to 1c. For example, the shielding plate 13 provided between the conductors 1a and 1b may not have the same distance between the conductor 1a and the conductor 1b. In the second embodiment, the shielding plate 13 is Y-shaped, but may be T-shaped.

Claims (6)

  1. 　単相の電流の大きさを変換する貫通形変流器を１つの収容体に３つ収容してなる三相貫通形変流器であって、
    　前記貫通形変流器は、
    　単相の導体が孔を貫通する環状鉄心と、
    　前記環状鉄心の周囲に巻回された二次巻線と、
    　を備え、
    　前記環状鉄心は、他の前記環状鉄心を貫通する前記導体に流れた事故電流により発生する磁界によって磁気飽和する箇所に設けられた第１のギャップと、前記箇所を基点に等配位置に設けられた第２のギャップとを含み構成された三相貫通形変流器。     A three-phase through-type current transformer comprising three through-type current transformers for converting the magnitude of a single-phase current in one container,
    The through-type current transformer is
    An annular core with a single-phase conductor passing through the hole;
    A secondary winding wound around the annular core;
    With
    The annular core is provided at equidistant positions with a first gap provided at a location where magnetic saturation is caused by a magnetic field generated by an accident current flowing through the conductor passing through the other annular core, and the location as a base point. A three-phase through-type current transformer configured to include the second gap.
  2. 　前記環状鉄心は、その中心が正三角形の頂点に位置するようにそれぞれ配置され、
    　前記第１のギャップは、当該ギャップが設けられる前記環状鉄心の、当該環状鉄心と他の２つの前記環状鉄心との最近接点間に設けられ、
    　前記第２のギャップは、前記第１のギャップに対向する位置に設けられた、請求項１記載の三相貫通形変流器。     The annular cores are respectively arranged so that the center thereof is located at the apex of an equilateral triangle,
    The first gap is provided between the closest points of the annular core in which the gap is provided, between the annular core and the other two annular cores,
    The three-phase through current transformer according to claim 1, wherein the second gap is provided at a position facing the first gap.
  3. 　前記第１のギャップは、前記最近接点間の中央位置に設けられ、
    　前記第２のギャップは、前記中央位置と対向する位置に設けられた請求項２記載の三相貫通形変流器。     The first gap is provided at a central position between the closest contacts;
    The three-phase through current transformer according to claim 2, wherein the second gap is provided at a position facing the center position.
  4. 　前記環状鉄心は、前記第１のギャップと前記第２のギャップをそれぞれ１つのみ設けられた請求項１～３のいずれかに記載の三相貫通形変流器。 The three-phase through-type current transformer according to any one of claims 1 to 3, wherein the annular iron core is provided with only one each of the first gap and the second gap.
  5. 　前記貫通形変流器の相間には、遮蔽板が設けられ、
    　前記遮蔽板は、導電率が３５×１０６Ｓ／ｍ以上の導電体からなり、厚みが５ｍｍ以上、高さが前記貫通形変流器の高さ以上である請求項１～４のいずれかに記載の三相貫通形変流器。     Between the phases of the through-type current transformer, a shielding plate is provided,
    The shield plate is made of a conductor having a conductivity of 35 × 10 6 S / m or more, has a thickness of 5 mm or more, and has a height that is not less than the height of the through-type current transformer. A three-phase through-type current transformer as described in 1.
  6. 　各前記貫通形変流器に前記貫通形変流器を覆う遮蔽筒が設けられ、
    　前記遮蔽筒は、導電率が３５×１０６Ｓ／ｍ以上の導電体からなり、厚みが５ｍｍ以上、高さが前記貫通形変流器の高さ以上である請求項１～４のいずれかに記載の三相貫通形変流器。     Each through-type current transformer is provided with a shielding cylinder that covers the through-type current transformer,
    5. The shield cylinder is made of a conductor having an electrical conductivity of 35 × 10 6 S / m or more, has a thickness of 5 mm or more, and has a height that is equal to or higher than the height of the through-type current transformer. A three-phase through-type current transformer as described in 1.
PCT/JP2016/077650 2016-09-20 2016-09-20 Three-phase through-type current transformer WO2018055664A1 (en)

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JPS5568604A (en) * 1978-11-13 1980-05-23 Siemens Ag Electric energy supply device with through type current transformer
JPS5822970A (en) * 1981-08-03 1983-02-10 Midori Anzen Kk High sensitivity zero-phase current detecting method by 3 current transformer system
JPH01293512A (en) * 1988-05-20 1989-11-27 Mitsubishi Electric Corp Instrument current transformer of gas insulation apparatus
JP2000156327A (en) * 1998-11-20 2000-06-06 Toko Electric Corp Through type current transformer
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