JPS6111042B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas insulated switchgear, and more particularly to a grounding method for a metal case of a composite gas insulated switchgear.

Conventional composite gas insulated switchgear is shown in Figure 1a and b.
It is constructed as shown in FIG. 1, with 1 being a breaker, 2 a bushing, 3 a disconnector, 4 a grounding device, and 5 a current transformer. The outer metal cases of each device are electrically connected. These devices are supported and fixed by legs 6.

As shown in FIG.
It is supported and fixed by insulating it with the earth through a. The outer metal case is connected to the grounding network 9 of the substation via a grounding wire 8 and is grounded at only one point. This grounding method is called one-point grounding. In this method, most of the magnetic field caused by the main circuit current (hereinafter referred to as main circuit current) flowing from the metal case to the conductor fixed via the insulator inside the metal case leaks to the outside of the outer metal case. Put it away. Therefore, the main circuit current is
Under large currents of 8KA, 12KA or more, leakage magnetic fields cause induction disturbances to control equipment, including control cables or relays that control local heating and placement of nearby steel products.

FIG. 1b shows a multi-point grounding system in which the outer metal case is connected to the grounding network 9 of the substation via the grounding wire 8 at two or more points to ground it. In this method, a closed circuit is formed between the outer metal case, the ground point 8, and the ground network 9, and a circulating current flows. There is no problem when the main circuit current is 4 KA or less, but when the current is 8 KA, 12 KA or more, the circulating current is large and there is a risk that the grounding wire 8 and the grounding network 9 will heat up and melt.

The purpose of the present invention was to eliminate the above-mentioned drawbacks, and to provide a gas insulated switchgear in which a large current gas insulated switchgear is grounded at multiple points to improve reliability and safety of the device. be.

The present invention will be explained below with reference to the embodiments shown in FIGS. 2 and 3.

Parts having the same functions as those in FIGS. 1a and 1b are given the same reference numerals. As shown in Figure 2, 1.
2 is a bushing, 3 is a disconnector, 4 is a grounding device, 5
is a current transformer. The outer metal case of each device should have a current carrying capacity and be electrically connected. Then, one or more conductors 11 (hereinafter referred to as sheath conductors) with a current-carrying capacity buried underground approximately parallel to the length direction of the outer metal case are connected to connecting portions 10a and 10b at both ends of the outer metal case. connect,
A closed circuit is created using the outer metal case of the device and the sheath conductor 11. The sheath conductor 11 is connected to a grounding network 9 of an electric station, for example, a substation, at one or more points to be grounded. Furthermore, in order to improve the safety of the device, the outer metal case and the sheath conductor 11 are connected to each other by a grounding wire 8 and grounded.

The above structure has the following effects. That is, as shown in FIG. 3, a circulating current i ₁ that cancels the external magnetic flux Φ ₁ due to the main circuit current I flows through the closed circuit between the outer metal case and the sheath conductor 11, producing a magnetic flux Φi ₁ . Since I and i ₁ have a phase difference of about 180°, the leakage external magnetic flux is reduced to Φ ₁ −Φi ₁ . Almost no current flows through the intermediate grounding wire 8. Therefore, since the leakage magnetic field in the space is reduced, local heating of nearby steel objects and induction disturbances to the control system can be ignored.
In addition, a sheathed conductor 11 buried underground as a closed circuit
, the grounding wire and grounding net will not heat up or melt. Furthermore, since the conductor is buried underground, it also serves as a grounding rod, increasing the safety of the device. It goes without saying that the above can also be applied to the generatrix portion.

As described above, according to the present invention, a plurality of electrically connected metal cases and one or more sheathed conductors with large electric capacity are buried in the ground approximately parallel to the longitudinal direction of the cases, and the sheathed conductors and the metal cases are connected to each other. to form a closed circuit in which circulating current can flow,
By connecting this closed circuit to the ground network at one or more points, the leakage magnetic field is reduced, which prevents damage caused by this magnetic field.Also, by burying a sheathed conductor with a large current capacity, circulating current can cause damage to the ground wire or ground. It is possible to provide a gas insulated switchgear in which the mesh does not melt, the large current insulated switchgear can be safely grounded at multiple points, and the safety and reliability of the device are improved.

[Brief explanation of drawings]

FIGS. 1a and 1b are longitudinal cross-sectional views showing the main parts of a conventional gas-insulated switchgear, and FIGS. 2 and 3 are longitudinal cross-sectional views and electric circuits showing the main parts of the gas-insulated switchgear of the present invention, respectively. It is a diagram. 1... Line disconnector, 2... Bushing, 3... Disconnector, 4... Grounding device, 5... Current transformer, 6...
Legs, 7...Insulator, 8...Grounding wire, 9...Grounding net, 10a, 10b...Connection portion, 11...Sheath conductor.

Claims (1)

[Claims] 1 Gas-insulated switchgear consisting of a plurality of electrically connected metal cases and a live part housed in the cases together with an insulating gas, and a gas-insulated switchgear in which the metal cases are connected to a grounding network provided at an electrical station. A grounded closed circuit for circulating current is formed by connecting the metal case of each case and one or more sheathed conductors buried underground approximately parallel to the longitudinal direction of this case, and this closed circuit and the grounded conductor are connected to each other. A gas-insulated switchgear characterized by being connected to a network at one or more points.