JPH07220963A - Current transformer - Google Patents

Abstract

PURPOSE:To acquire a current transformer which is mounted on an electric device whose inner conductor is contained in a metallic container and is filled with insulation medium, and is not affected by a grounding current in the metallic container when grounding trouble occurs inside a device of an air-core current transformer for detecting a current of an inner conductor. CONSTITUTION:A projection part is provided to a metallic container 2 and is made a containment part of current transformers 5, 6. The current transformer 5 of air-core type and the current transformer 6 of core type are arranged parallel in the containment part concentrically with an inner conductor. A shield 11 comprised of a non-magnetic conductor is interposed between an outer circumferencial surface of the air-core type current transformer 5 and a side surface in opposition to a side wall of the containment part. Thereby, a current transformer which enables accurate detection of a current of an inner conductor can be acquired with out inducing a voltage in the air-core current transformer in a magnetic field generated by a grounding current flowing deflectingly in a containment part toward a grounding point of a metallic container when a grounding trouble occurs inside a device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current transformer which is mounted on an electric device, such as a gas-insulated electric device, whose main body is housed in a metal container installed in a substation or the like, and which detects a current flowing through an inner conductor. It is about.

[0002]

2. Description of the Related Art As a current detecting means of a gas-insulated electric device, a through-type current transformer in which a winding is wound around an annular iron core arranged concentrically with an inner conductor housed in the center of a metal container. The method of attaching the to a metal container is common. The current transformer is for measurement to detect the current value under normal operating conditions,
There is one for protection that detects a large accident current flowing at the time of an accident, and this current transformer for protection needs to secure some detection accuracy for the accident current, and the cross-sectional area of the iron core corresponds to the accident current. A large one is used so that magnetic saturation does not occur. When the short-circuit capacity of the power transmission system increases, the required cross-sectional area of the iron core becomes enormous, and the weight and the size also increase, which makes it expensive. For this reason, as the capacity of the power transmission system increases, a protectionless current transformer of a non-iron core type that does not use an iron core has come into practical use. The iron-free core current transformer detects a voltage proportional to the magnetic field generated by the current flowing through the inner conductor, and inputs this voltage to the protection system. Good detection is possible, and it is not necessary to increase the dimension even if the target fault current increases.

FIG. 4 shows a conventional embodiment in which an iron core type current transformer for protection and an iron core type current transformer for measurement are arranged in parallel and applied to a gas insulated electric device. In the figure, 1 is an inner conductor arranged in the center of the device, 2 is an inner conductor, and
A metal container 3 filled with an insulating gas is a support fitting for mounting the current transformer, and has a flange for supporting the metal container 2. Reference numeral 4 denotes a housing for a current transformer formed by enlarging a part of the diameter of the metal container 2, and 5 denotes an annular winding core 5a made of a non-magnetic insulating material and a magnetic field generated by a current flowing through the inner conductor 1. An iron-free core type current transformer in which windings 5b are wound so as to interlink, 6 is an iron-core type current transformer made to match the diameter of the ironless core type current transformer 5,
A winding 6b is wound around the iron core 6a formed in a ring shape. Reference numeral 7 is a pressing plate attached to the current transformer 6, 8 is a pressing metal fixture fixed to the support metal fitting 3, and 9 is a bolt for applying a pressing force to the current transformer 6. Reference numeral 10 is a ground lead for grounding the metal container 2.

Ironless core type and iron core type current transformers 5, 6
Is manufactured by matching at least the inner diameter, is inserted into the support fitting 3, is fixed, and is attached to the metal container 2. The arrangement order of the iron-free core type current transformer 5 and the iron-core type current transformer 6 is determined by the protection range in the equipment installation state. The ironless type is on the flange side and on the opposite side. is there.

The operation of the current transformer shown in FIG. 4 in which the non-iron core type current transformer and the iron core type current transformer are arranged in parallel as described above will be described. The iron-core type current transformer can detect a current inversely proportional to the winding ratio through a magnetic flux obtained by multiplying the magnetic field due to the current flowing through the inner conductor 1 by the cross-sectional area of the iron core and the relative permeability. The magnetic flux density is large compared to the magnetic flux density of the ambient magnetic field and is hardly affected by the ambient magnetic field, but in the ironless core current transformer, the magnetic flux density in the winding has no difference from the magnetic flux density of the ambient magnetic field. Therefore, it is sensitive to changes in the ambient magnetic field.

In the configuration of FIG. 4 in which the ironless core type current transformer and the iron-bearing core type current transformer are arranged in parallel and housed in the metal container 2, if a ground fault occurs at point F, the inner conductor 1 and the metal container 2 will occur. Is connected by an arc A, and the ground fault current is the shortest path from the point F of the metal container 2 to the grounded point E via the current transformer housing 4 as shown by the arrow in the figure. , The current distribution in the circular cross section of the metal container 2 is biased toward the grounded point E side. For this reason, the magnetic field generated by the ground fault current is linked to the grounded E-side winding of the metal container 2 of the non-iron core type current transformer 5 and the iron core type current transformer 6, and the iron core type current transformer As described above, it has almost no effect on the transformer 6, but on the ironless core type current transformer 5, the magnetic flux due to the biased ground fault current interlinks with the winding and A voltage proportional to the interlinkage magnetic flux is induced, and a voltage superposed on the voltage induced by the magnetic flux generated by the current flowing through the inner conductor 1 is induced.

For example, when the left side of the ground-faulted point F in FIG. 4 is the power supply side, the ground-fault current does not flow in the internal conductor 1 of the accommodating portion of the current transformers 5 and 6, but from the point F. It is assumed that a voltage is induced in the iron-core type current transformer 5 due to a magnetic field due to a ground fault current that is biased downwardly of the metal container 2 toward the point E, and the protection system malfunctions.

[0008]

Since the conventional iron-free core type current transformer is sensitive to the surrounding magnetic field, an error may occur due to the induced voltage due to the surrounding magnetic field, which may cause the protection system to malfunction. was there.

The present invention has been made to solve the above problems, and an object thereof is to obtain a current transformer which is not affected by the ambient magnetic field.

[0010]

A current transformer according to claim 1 of the present invention comprises a non-magnetic conductor on the outer peripheral surface and at least one side surface of an iron-free core type current transformer which is mounted concentrically with an inner conductor. It is equipped with a shield.

Further, according to a second aspect of the present invention, in the current transformer, a shield made of a non-magnetic conductor is attached to the outer peripheral surface and at least one side surface of the iron-free core current transformer, and these are integrated into an insulating tape or the like. It is fixed by winding.

Further, according to a third aspect of the present invention, there is provided an iron-core type current transformer mounted on a metal container, which has an outer peripheral surface and at least one side surface between the inner peripheral wall of the metal container. A shield material made of a non-magnetic conductor is inserted and attached to a metal container.

According to a fourth aspect of the present invention, there is provided a current transformer group in which a non-iron core type current transformer and a ferrous core type current transformer mounted in a metal container are arranged in parallel. And a shield made of a non-magnetic conductor is inserted between the outer peripheral surface and at least one side surface arranged in parallel with the inner peripheral wall of the metal container and mounted on the metal container.

[0014]

In the current transformer according to the first aspect of the present invention, since the shield made of a non-magnetic conductor is provided on the outer peripheral surface and at least one side surface of the ironless core current transformer, the ambient magnetic field is shielded by the shield. Therefore, the ambient magnetic field does not affect the iron-free core type current transformer.

Further, in the current transformer according to the second aspect of the present invention, a shield made of a non-magnetic conductor is attached to the outer peripheral surface and at least one side surface of the iron-core type current transformer, and these are integrally integrated with an insulating tape or the like. By winding and fixing, the work of inserting the shield at the time of mounting work on the device is eliminated, and the mounting work is simplified.

Further, in the current transformer according to claim 3 of the present invention, the iron core type current transformer mounted on the metal container has an outer peripheral surface and at least one side surface between the inner peripheral wall of the metal container. By interposing the shield made of a non-magnetic conductor, when a ground fault occurs inside the device, the influence of the magnetic field due to the ground fault current flowing unevenly in the metal container disappears.

According to a third aspect of the present invention, there is provided a current transformer group in which a non-iron core type current transformer and a ferrous core type current transformer mounted in a metal container are arranged in parallel. The effect of the magnetic field due to the ground fault current that is biased in the metal container due to the insertion of the shield on the outer peripheral surface and at least one side surface arranged in parallel is not only the iron-free core current transformer but also the iron-core current transformer. Also disappears against.

[0018]

【Example】

Example 1. An embodiment of the present invention will be described below with reference to FIG. In FIG. 1, reference numerals 1 to 10 are the same as or have the same functions as those of the conventional example of FIG. Reference numeral 11 is a shield made of a non-magnetic conductor such as copper or aluminum interposed between the outer peripheral surface of the ironless core voltage transformer 5 and the side wall surface of the current transformer housing portion 4 of the metal container 2. Reference numeral 12 is a shield made of a non-magnetic conductor inserted on the side surface opposite to the side surface facing the flange portion of the housing portion 4 of the iron-free core type current transformer 5.

As described above, since the shield 11 is provided on the side surface and the outer peripheral surface of the storage portion 4 of the iron-free core type current transformer 5 facing the side wall, the ground point E as seen from the current transformer storage portion 4 is provided.
If a ground fault occurs at the point F on the other side,
The iron-core type current transformer 5 is shielded against the magnetic field generated by the ground fault current flowing in the current transformer housing 4 of the metal container 2 in a biased manner, so that there is almost no influence.

The ground-fault current flowing in the metal container 2 is most significantly affected in the portion that flows around the current transformer such as the storage portion with respect to the current transformer, but is also slightly affected in the straight portion. If there is an influence and the detection accuracy is severely required, it is more complete if the shield 12 is provided not only on the outer peripheral surface of the iron-core type current transformer 5 and the side surface facing the side wall of the housing portion 4 but also on the opposite side surface. As a result, the influence of the ground fault current flowing unevenly can be further reduced.

Example 2. In the first embodiment, the shields 11 and 12 provided on the outer peripheral surface and the side surface of the iron-free core type current transformer 5 are interleaved when the current transformers 5 and 6 are attached to the housing portion 4 of the metal container. In the second embodiment, as shown in FIG. 2, one side surface and the outer peripheral surface of the winding 5b wound around the core 5a of the iron-free core type current transformer 5 are non-magnetic conductors having an L-shaped cross section, such as copper. Alternatively, a shield 21 made of aluminum is added, and a shield 22 made of the same material as the doughnut-shaped shield 21 is also added to the other side surface, and the surface is integrally wound and fixed by taping or the like. It is configured to be mounted in the storage unit 4.

With this configuration, the shields 21 and 22
In addition to the effect of being completely unaffected by the magnetic field due to the ground fault current as in the case of the first embodiment, the work of mounting the device on the equipment does not require the work of inserting the shield and the assembly work can be easily performed. Further, since the shields are provided on both side surfaces, it is possible to freely select the polarity at the time of mounting.

Example 3. In the third embodiment, as shown in FIG.
A non-iron core type current transformer 5 and a ferrous core type current transformer 6 are arranged in parallel, and the side faces facing the outer peripheral surface of the arranged current transformer group and the side wall of the storage portion of the metal container are U-shaped in cross section. Shield of non-magnetic conductor such as copper or aluminum 3
It was configured such that it was mounted so as to be surrounded by 1.

With this structure, even if a ground fault occurs inside the equipment and a biased current flows in the metal container 2, the magnetic field due to the current is shielded by the shield 31, so that it is of a non-ferrous core type or a ferrous core type. Both the current transformers 5 and 6 can eliminate the influence of the magnetic field due to the ground fault current.

[0025]

Since the current transformer according to claim 1 of the present invention is provided with the shield material made of a non-magnetic conductor mounted on the outer peripheral surface and at least one side surface of the iron-free core type current transformer. , Almost no influence of the external magnetic field generated around the iron-free core type current transformer, and malfunction due to the external magnetic field can be eliminated.

A current transformer according to claim 2 of the present invention is
Since a shield material made of non-magnetic conductor is attached to the outer peripheral surface and at least one side surface of the iron-free core current transformer, and these are integrally wound and fixed with insulating tape, in addition to being hardly affected by the external magnetic field. As a result, the non-iron core type current transformer and the shield material are handled as a unit during the mounting work on the equipment, so that the mounting work can be easily performed.

The current transformer according to claim 3 of the present invention is
Since a shield material made of a non-magnetic conductor is inserted and mounted on the outer peripheral surface of the iron-free core current transformer and on at least one side surface facing the side wall of the housing of the metal container, a metal container is installed in the event of a ground fault in the equipment It is almost unaffected by the magnetic field due to the ground-fault current that is biased toward.

A current transformer according to claim 4 of the present invention is
A non-ferrous core type current transformer and a ferrous core type current transformer are arranged in parallel, and a nonmagnetic conductor is formed on at least one side surface facing the outer peripheral surface of the parallel arranged current transformer group and the side wall of the storage part of the metal container. Since the shield material is inserted and mounted, the influence of the magnetic field due to the ground fault current that biases the metal container can be eliminated not only for the iron-free core current transformer but also for the iron-core current transformer.

[Brief description of drawings]

FIG. 1 is a sectional view showing a configuration of a current transformer according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a configuration of a coreless current transformer of a current transformer according to a second embodiment of the present invention.

FIG. 3 is a cross-sectional view showing the configuration of a current transformer according to a third embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a configuration of a conventional current transformer.

[Explanation of symbols]

 1 Inner Conductor 2 Metal Container 3 Support Metal 4 Storage Section 5 Ironless Core Current Transformer 6 Iron Core Current Transformer 11 Shield 12 Shield 21 Shield 22 Shield 31 Shield

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Naoto Yamamoto 8-1-1 Tsukaguchihonmachi, Amagasaki City Mitsubishi Electric Corporation Itami Works

Claims (4)

[Claims] 1. A main body of a current transformer including a winding core, which is concentrically mounted on an inner conductor, and which is annularly formed of a non-magnetic insulating material, and a winding wound around the winding core, and the current transformer. A current transformer comprising a shield material made of a non-magnetic conductor attached to the outer peripheral surface and at least one side surface of the main body. 2. A current transformer body comprising a winding core, which is concentrically mounted on an inner conductor, and which is formed annularly by a non-magnetic insulating material, and a winding wound around the winding core, and the current transformer. A shield material made of a non-magnetic conductor provided on the outer peripheral surface and at least one side surface of the main body, the shield material and the current transformer main body are attached, and both are integrally fixed by winding with an insulating tape. A current transformer characterized in that. 3. A winding core formed in an annular shape by a non-magnetic insulator having an inner conductor housed in the center thereof and mounted along the inner circumference of a metal container filled with an insulating medium, and wound around this winding core. A current transformer body composed of a winding and a winding member formed of a non-magnetic conductor on the outer peripheral surface and at least one side surface of the current transformer body and the inner peripheral wall of the metal container. A current transformer characterized in that it is inserted and mounted on the metal container. 4. A winding core formed in a ring shape by a non-magnetic insulator along an inner circumference of a metal container having an inner conductor housed in the center and filled with an insulating medium, and the winding core being wound around the winding core. A current transformer group in which a coreless current transformer consisting of a winding and a cored core current transformer in which a winding is wound around an annular iron core are arranged in parallel, the outer peripheral surface of the current transformer group and the parallel A current transformer, comprising: a shield material made of a non-magnetic conductor, which is interposed between at least one side surface of the metal container and the inner peripheral wall of the metal container.