JPS61177111A - Gas insulated switchgear - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a gas insulated switchgear, and more particularly to a gas insulated switchgear with an improved grounding configuration of a metal case.

[Technical background of the invention and its problems]

In recent years, due to the rapid increase in electricity demand and the difficulty in acquiring land for substation construction, gas insulated switchgear (hereinafter abbreviated as GIS) has come into widespread use, and its voltage class has also increased to 5.
00 kV, and the rated current is 8.0OOA~12
,0OOA. Such a large capacity GIS
A multi-point grounding system is adopted mainly to reduce the influence of the magnetic field caused by the main circuit current.

In the multi-point grounding method, the metal case is grounded at multiple points, and a current-carrying conductor called a phase-to-phase shunt is installed to connect the metal cases of each phase, and a closed loop consisting of these metal cases and the phase-to-phase shunt is formed. The purpose is to reduce the external magnetic field caused by the main circuit current by flowing an induced current having a phase substantially opposite to that of the main circuit current through this closed loop.

In the conventional multi-point grounding system, as shown in FIG. 5, the metal cases 1 of each phase are electrically connected by an interphase shunt, that is, a current-carrying conductor 2. Furthermore, in the case flange insulating section 6 that connects the metal cases 1 to each other via an insulating member,
The induced current flowing through the metal case 1, ie, the sheath current, is prevented from flowing. When current flows in the main circuit, a sheath current with almost the opposite phase to the main circuit current flows through the closed loop formed by the metal case 1 of each phase and the interphase shunt 2, so the external magnetic field due to the main circuit current is significantly reduced. This can prevent local heating of steel, electromagnetic vibration, and induction into control cables caused by external magnetic fields.

In places where the metal container or metal case is electrically connected, even if the metal case is grounded to the substation grounding mesh at multiple points, the impedance of the metal case itself will exceed the circuit consisting of the standing grounding wire and the buried grounding mesh. Since the impedance is significantly smaller than the impedance of

However, at locations where the sheath current becomes significantly discontinuous, such as the case flange insulating portion 6 shown in FIG. 5, the sheath current is divided into the interphase shunt 2 and the ground wire 5. Further, the mesh current path 7 shown by the dotted line is formed in a buried ground mesh buried underground.

In such locations, it is difficult to install an in-phase shunt to bypass the sheath current, since the current carrying capacity of the bellows is smaller than the strength issue, and it absorbs the displacement between the installation location of the external current transformer and the divided foundation. This applies to large displacement expansion joints, etc. This also applies to bushings, cable connections, etc. in that the sheath current becomes discontinuous.

At a point where the sheath current becomes discontinuous, the rate at which the sheath current is divided is determined by the ratio of the impedance of the current-carrying conductor 2 to the impedance of the circuit consisting of the raised grounding wire 5 and the buried grounding mesh.

In particular, in GIS with ultra-high voltage or higher voltage, 3.
The impedance of the latter is low because buried ground meshes are used at intervals of about m.

In addition, especially when the equipment is placed on the foundation surface or near the ground surface, the length of the rising grounding wire 5 is also shortened, and the impedance of the latter becomes further smaller, so that the current flowing into the rising grounding wire 5 becomes larger. In addition, the current value flowing into the buried grounding mesh through the stand-up grounding wire 5 will be close to 30% of the main circuit current in such a case, and when converted to an 8,0OOA rating, it will reach 2.40OA. Wires and ground mesh may become excessively heated.

It is necessary to prevent such a temperature rise in the grounding wire because it leads to a decrease in the strength of the foundation concrete and even cracks.

[Purpose of the invention]

The present invention has been made in consideration of the above points, and an object of the present invention is to provide a gas insulated switchgear having a grounding configuration that reduces the current flowing into the grounding wire.

[Summary of the invention]

In order to achieve such an object, according to the present invention, the position of the stand-up grounding wire provided near the current-carrying conductor located at the outermost part of the closed loop made of the current-carrying conductor connecting the metal cases of each phase is changed to The current flowing into the rising ground wire is reduced by providing a distance at least twice the distance between the axes of the metal case and arranging it inside the closed loop.

[Embodiments of the invention]

Hereinafter, one embodiment of a gas insulated switchgear according to the present invention will be described with reference to FIGS. 1 to 3. The same parts as in FIG. 5 are given the same reference numerals. As shown in FIG. 1, a gas insulated switchgear is constructed by housing a live part inside a metal case and sealing an insulating gas inside the metal case. , lb, and lc are insulated and joined to each other via insulating members at case flange insulating parts 6a, 6b, and 6c, respectively. And each case flange insulation part 6a, 6b, 6c
Standing grounding wire 5a near t5a2; 5bl, 5
b2 ; 5cl and 5c2 are installed at a distance from the installation position of the normal conductor 2, which is a so-called interphase shunt that shorts the metal cases la, lb, and lc of each phase. This distance is the distance d between the axes of the metal case of each phase.
(hereinafter abbreviated as interphase distance).

That is, the rising grounding wire 5 is connected to the phase-to-phase shunt 2 located at the outermost part of the closed loop consisting of the metal case 1 and the phase-to-phase shunt 2, that is, from the position of the phase-to-phase shunt 2 near the case flange insulating part 6, to the phase-to-phase distance d of 2. The mesh current path 7 of the ground mesh is provided inside the closed loop at a distance more than twice that of the current mesh current path 7 of the ground mesh.

Next, the effects of the present invention will be explained. The line diagrams in FIGS. 2 and 3 are shown for the measurement results using the actual 500 gas insulated switchgear.

In Figure 2, the vertical axis shows the rising and grounding line current (%), and the horizontal axis shows D/d, so that D/d is approximately 2 or more, that is, Dad≧
At the time of 2, the rising ground line current decreases.

In addition, in Figure 3, the vertical axis represents the interphase shunt current (%).

If we take the horizontal axis D/d, D/d is approximately 2 or more, that is, D/d.
When d≧2, a curve was shown in which the interphase shunt current (%) was almost saturated.

As shown in Figures 2 and 3, as D/d increases, that is, the position of the stand-up ground wire is located inside the closed loop, the current flowing into this ground wire decreases, and vice versa. It can be seen that the current flowing through the interphase shunt at the outermost part increases.

That is, near the case flange insulating portion 6, the incoming current is divided into the interphase shunt 2 and the rising ground wire 5. For example, the current flowing into the rising ground line 5cl mainly flows through a path from the rising ground line 5c through the grounding mesh current path 7 and from the rising ground line 5c2 to the metal case 1c. This can be easily inferred from the fact that the induced current flowing through the closed loop tends to concentrate at the outermost portion.

That is, the stand-up grounding wire 5c, the grounding mesh current path 7
If the impedance of the circuit consisting of the stand-up grounding wire 5c2 is low, it becomes a bypass circuit for the case flange insulating section 6c, so that a larger closed loop consisting of the metal case 1 and the phase-to-phase shunt 2 can be configured including this bypass circuit. Therefore, since the induced lightning 98 tends to flow more into the outer closed loop as described above, a large current will flow into the bypass circuit.

In order to prevent this, the impedance of the bypass circuit can be increased. That is, as shown in FIGS. 2 and 3, the impedance of the bypass circuit is increased by providing the rising ground line 5 inside the closed loop consisting of the metal case 1, the interphase shunt 2, and the like.

According to test results using an actual device, when D/d becomes 2 or more, the current flowing through the rising ground wire 5 becomes about 7% or less of the main circuit current. In this case, if the rated current is 8000A, the current flowing through the stand-up grounding wire 5 is 8000 x 0.7
= 560A or less, so it is a value that can be handled without any problem by using about two normal startup-ground wires.

Next, another embodiment of the present invention will be described with reference to FIG.

The same parts as in FIG. 1 are given the same reference numerals.

Since the sheath current is also discontinuous in the bushing section, the grounding wire inflow current can be significantly reduced by locating the rising grounding wire 5 inside the closed loop formed by the metal case 1, interphase shunt 2, etc. I can do it. The same thing can also be applied to cable connections.

〔Effect of the invention〕

As explained above, according to the present invention, the position of the stand-up grounding wire provided near the current-carrying conductor located at the outermost part of the closed loop formed by the current-carrying conductor connecting the metal cases of each phase is adjusted to the metal case of each phase. By providing at least twice the distance between the phases and arranging it inside the closed loop,
It is possible to provide a gas insulated switchgear that can reduce the current flowing into the rising ground wire.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of the gas insulated switchgear of the present invention. Figures 2 and 3 show D/d of the gas insulated switchgear of the present invention.
Figure 4 is a perspective view of another embodiment of the present invention, and Figure 5 is a perspective view of a conventional gas-insulated switchgear. It is. 1...Metal case. la, lb, Ic...metal cases for each phase. 2... Current-carrying conductor (interphase shunt). 3... Busbar device of gas insulated switchgear. 5... Standing ground wire. 5ax + 5b1? 5c1j 5a2g 5b2r
5C2 = Startup grounding wire for each phase. 6...Case flange insulation part. 7...Metshu current path. D: Distance between the grounding wire and the current-carrying conductor. d... Distance between axes of metal cases of each phase (distance between phases).

Claims (1)

[Claims] The live part is enclosed in a metal case along with insulating gas.
This metal case is grounded at multiple points, and the metal cases of each phase are connected with a current-carrying conductor to form a closed loop consisting of the metal case and the current-carrying conductor, and the main circuit current is connected to the metal case. In a gas-insulated switchgear that conducts induced currents of almost opposite phase, the position of a rising grounding wire provided near the current-carrying conductor located at the outermost part of the closed loop formed by the current-carrying conductor connecting the metal cases of each phase, A gas insulated switchgear characterized in that the distance from the current-carrying conductor is at least twice the distance between the axes of the metal case of each phase, and the distance is located inside the closed loop.