JPS64886B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a grounding device for electrical equipment such as phase-separated gas insulated equipment.

In recent years, due to land issues and environmental harmony, gas insulated equipment, which can be downsized and non-polluting, has come into widespread use. Gas-insulated equipment has a live part housed in a jacket or container, which is insulated by filling it with a highly insulating gas such as SF6 gas, and the jacket is grounded for safety. Grounding of the envelope requires grounding at many points for safety reasons due to the many grounding wires or grounding networks buried underground. However, when grounding is performed at multiple points, a current circulation path is formed between the underground grounding wire, the grounding connection wire, and the outer sheath of the gas-insulated equipment, and due to the magnetic field caused by the current flowing through the conductor of the gas-insulated equipment, An induced current will flow in this circulation path. This current can reach several tens of percent of the current flowing through the device's conductor, causing heat generation in the grounding wire, which is a major problem in high-current devices.

FIG. 1 shows a grounding device for a gas insulated bus bar, which has the simplest structure as a three-phase separated gas insulated electric device. In the figure, 1a, 1b, 1c
is the outer covering, and also serves as a container for filling the interior with a highly insulating gas such as SF6 under pressure of about 3 to 4 atmospheres. 2a, 2b, and 2c are conductors through which the main current of the bus bar flows, and are insulated from the jackets 1a, 1b, and 1c by an insulating gas or a solid insulator (not shown).
3a, 3b, 3c and 4a, 4b, 4c are outer cover 1
Connecting wires for grounding are drawn down from a, 1b, and 1c to the ground, and the adjacent ones of each phase are shown.
The distances between the connection lines 3a, 3b, 3c and 4a, 4c, 4d are determined by a necessary value for safety reasons and cannot be made too large. In the case of a long busbar, it is necessary to lower the connection wires from many points on the jacket, but in Fig. 1, the connection wires 3a, 3b, 3 are typically placed at intervals of length l.
The diagram shows the classifications in which c, 4a, 4b, and 4c have been determined. These connection lines 3a, 3b, 3c,
4a, 4b, and 4c are underground from the part indicated by the symbol E. 5, 6, and 7 are grounding wires forming part of the grounding network, which are laid underground at approximately the same depth.

Now, looking at the a phase, the outer sheath 1a, the connection wire 3
A, 4a grounding wire 5 forms a circulation path, and current mainly flows through the nearest conductor 2a (due to changes in the magnetic field due to alternating current, an induced current flows in this circulation path. Similarly, induced currents flow in the b and c phases.Such induced currents are caused by the number 10 of currents flowing through the conductors 2a, 2b, and 2c.
%, the grounding wires 5, 6, 7 and the connecting wires 3a, 3b, 3c, 4a, 4b, 4c may generate heat and breakage, making it necessary to use large grounding wires, resulting in economical problems. It was a serious problem.

This invention was made in order to eliminate the above-mentioned drawbacks, and by configuring the voltage induced in the jacket of each phase to cancel each other out, the induced current flowing through the jacket and the ground wire To provide a grounding device for electrical equipment with reduced noise.

FIG. 2 shows an embodiment of the invention. In one embodiment of the present invention, the grounding wire 5 connected to the connection line 3a is laid approximately below the A-phase sheath 1a for a distance of approximately l along the longitudinal direction of the sheath, and the grounding wire 5 connected to the connection line 3a It is bent in a direction substantially perpendicular to the longitudinal direction of the jacket so as not to make electrical contact with the jacket 1b, and is connected to the b-phase connection line 4b to be connected to the jacket 1b.
A connecting wire 3b extends from the outer sheath 1b and is connected to a grounding wire 6, and the grounding wire 6, like the grounding wire 5, is buried under the outer sheath 1b at a distance of approximately l and is electrically connected near the adjacent connecting wire 4b. It extends curved in a direction substantially perpendicular to the longitudinal direction of the jacket so as not to contact, and is connected to the c-phase connection line 4c. The connecting wire 4c is connected to the outer sheath 1c, the connecting wire 3c extends from the outer sheath 1c, and the grounding wire 7 is connected to the outer sheath 1c.
The connecting wire 4c is buried approximately at a distance of approximately l below the connecting wire 4c, and is bent approximately at right angles to the longitudinal direction of the jacket so as not to make electrical contact with the connecting wire 4c in the vicinity of the connecting wire 4c.
b and the grounding wires 5 and 6, and is connected to the connecting wire 4a and connected to the outer sheath 1a.

By configuring in this way, the outer cover 1a→
Ground wire 3a→Ground wire 5→Connection wire 4b→Sheath 1b→
Connection wire 3b → ground wire 6 → connection wire 4c → outer sheath 1c →
A closed circuit is formed that connects the connecting wire 3c → the grounding wire 7 → the outer sheath 1a, and for this closed circuit, a, b, c
The voltages induced by the currents flowing through the conductors 2a, 2b, 2c of each phase cancel each other out, and no induced current flows in the closed circuit.

If the gas-insulated busbar is long, lower a number of connecting wires from the outer sheath of each phase at intervals in the longitudinal direction.
By laying the grounding wires between adjacent connecting wires in the same manner as shown in FIG. 2, it is possible to almost eliminate induced current flowing through the jacket, the connecting wires, and the grounding wire.

FIG. 3 shows another embodiment of the invention.
In another embodiment of the present invention, if the distance between adjacent connecting wires 3a and 4a, 3b and 4b, and 3c and 4c is 1, then the grounding wire 5 is connected to the jacket 1a for about 1/3L.
It is arranged in the ground below in the axial direction of the envelope 1a, and then extends in the direction of the b phase approximately perpendicular to the axial direction of the envelope 1a, and is approximately 1/3 l under the envelope 1b in the b phase. The length extends in the axial direction of the sheath 1b, and then under the c-phase sheath 1c, the length of 1/3l extends in the axial direction of the sheath 1c and is connected to the lower end of the connecting line 4c. Similarly, ground wire 6 is 1/3
The distance l is below the outer sheath 1b, and the distance 1/3l is under the outer sheath 1.
Below c, a distance of 1/3l is placed under the jacket 1a and connected to the lower end of the connecting line 4a. Also, the connecting wire 7 is buried under the outer sheath 1c for a distance of 1/3l, under the outer sheath 1a for a distance of 1/3l, and under the outer sheath 1b for a distance of 1/3l, and the lower end of the connecting wire 4b. connected to. Ground wire 5,
Since parts 6 and 7 are buried at approximately the same depth, parts that may cross and come into contact with each other are electrically insulated from each other. Possible ways to insulate them include leaving a little space between them or narrowing the insulator only at the intersections.

By burying the grounding wire in this way, each outer jacket 1a, 1b, 1c connection wire 3a, 3b, 3c, 4
The induced electromotive force due to the three-phase alternating current flowing in the conductors 2a, 2b, 2c becomes extremely small in the circulation path made up of the grounding wires 5, 6, and 7, and almost no circulating current flows.

In addition, between the connecting wires 4a and 8a, 4b and 8b, 4c and 8c, and between the connecting wires 8a and 9a, 8b and 9b,
Also between 8c and 9c, connecting wires 3a and 4a,
Grounding wires 5, 6, and 7 are arranged so that a closed circuit similar to that between 3b and 4b and 3c and 4c is formed.

As described above, according to the present invention, the jacket and the ground wire form a closed circuit so that the induced power cancels each other out, so even if the grounding is performed at many points, there is almost no induced current in the ground wire. Since no current flows, there is no need to make the ground wire large as a countermeasure against induced current. Furthermore, since almost no current flows through the outer sheath of gas-insulated equipment, the amount of heat generated by the equipment is reduced, and even in high-current equipment, the heat dissipation surface area can be reduced, making the equipment more compact and having great economical effects. Moreover, since it can be grounded at multiple points, the rise in potential of the outer sheath is small, making it possible to obtain a safe electrical device.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a conventional grounding device for electrical equipment, and FIG. 2 is a perspective view showing an embodiment of the present invention.
FIG. 3 is a perspective view showing another embodiment of the invention. In the figure, 1a, 1b, 1c are outer covers, 3a, 3
b, 3c, 4a, 4b, 4c are connection lines, 5, 6,
7 is a grounding wire. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] 1. One end of each of the first to third outer sheaths arranged in parallel to accommodate three-phase conductors, and one end of each of the first to third grounding wires buried underground along the said outer sheaths. and connect the other end of the first ground wire and the other end of the second jacket, and connect the other end of the second ground wire and the other end of the third jacket. A grounding device for electrical equipment, characterized in that the other end of the third grounding wire is connected to the other end of the first jacket.