JPS59209009A - Gas insulated switching device - 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 [Field of the Invention] The present invention relates to a method for grounding a container section in which metal cylinders containing main conductive parts of a gas-insulated switchgear are electrically conductively coupled to each other.

[Prior art and its problems]

Grounding methods for container sections in gas-insulated switchgear include a single-point grounding method in which only one point in the container section is grounded, and a multi-point grounding method in which multiple points are grounded at intervals in the axial direction of the container section. There is. The single-point grounding method maintains each container section of the gas-insulated switchgear at ground potential during continuous operation, and
For example, deterioration of the ground insulation performance of insulating members installed in the container can be easily determined by removing the grounding conductor at the grounding point and connecting a microcurrent measuring device. Although this grounding method facilitates external diagnosis of the functional components housed in the building, it is susceptible to lightning surges during continuous operation, and switching surges caused by re-ignition or re-ignition when switching devices such as disconnectors cut off small currents. When a surge current flows through the metal cylinder of the container section, a transient voltage to the ground due to the product of the inductance of the container section with respect to the ground and the surge current, that is, a so-called sheath surge voltage, separates from the ground point on the container section. There is a risk of electrocution of the operator or dielectric breakdown between, for example, the operating box of a disconnector and the control wiring therein, which are at the same potential as the container. On the other hand, in the case of the multi-point grounding method, the above-mentioned surge current is shunted toward multiple grounding points, so the sheath surge voltage appearing between the container section and the ground is lower, but in this case, the following There are some drawbacks.

FIG. 1(a) shows an example of a conventional container section that is grounded at multiple points. In the figure, reference numerals 2 and 3 each indicate a full-area cylinder constituting the container section 1, which is electrically conductively coupled at a point B via a flexible conductor 4 as shown in FIG. 1 is insulated from the adjacent metal cylinder 6.7 by an insulating sheath 5 as shown in FIG. 1(C). E...
E2 is the ground point in container section 1, respectively. Figure 1 (
As shown in a), when the commercial frequency current ■o flows through the central conductor 9 forming the main current part and the switching device 1o, this ■. An induced current 10+ that cancels out the magnetic flux created around the current path circulates in the direction shown in the figure via the ground point. This induced current ■. ′
Although the size of the container section 1 varies depending on the height above the ground of the container section 1, it is 30 to 80% of the energizing current (2o), and the heat generation of the metal cylinder constituting the container section becomes a problem.

[Objective of the Invention] The purpose of the present invention is to reduce the magnitude of the sheath surge voltage generated in the above-mentioned single-point grounding method, and to prevent heat generation in the metal cylinder of the container section due to the induced current generated in the multi-point grounding method. do.

[Key points of the invention]

This invention involves directly grounding only one point in a container section consisting of metal cylinders that are conductively connected to each other and containing a main conductive part, and at least one point different from the grounding point to ground via a capacitor. In addition to reducing the sheath surge voltage caused by lightning surges and opening/closing surges, it is also possible to suppress the induced current generated by the current flowing during continuous operation and circulating through the container section and multiple grounding points to reduce the sheath surge voltage caused by lightning surges and opening/closing surges. This is intended to prevent heat generation in the metal cylinder during classification.

[Embodiments of the invention]

First, the mechanism of generating a sheath surge voltage in the container section and the principle of reducing the constant pressure of the sheath surge according to the present invention will be explained using the equivalent circuit shown in FIG.

FIG. 2(a) is an equivalent circuit when 82 points in FIG. 1 are not grounded, that is, when one point is grounded, and a rectangular wave voltage U is applied between the center conductor 9 and the grounding point E1. This assumes that the voltage is applied to Ll is ground point B
, and E2, L2 is the inductance within the same range of the container section, and C1 is the inductance between the main conductor and the container section within the same range. The capacitance is actually a distributed constant of five numbers, but here it is simulated by a lumped constant. The current 11 at this time is expressed by the following equation.

l ωl − π7n Due to this league current I, at point 82, v5=L2*
d i, /d t's surge ′rff, pressure: 2 v, = U casω1t ・・・・・・
・・・・・・・・・ (11Ll +L.

appears. In other words, L2 for the peak value U of the applied voltage
The peak value of the sheath surge voltage appears at the ratio of / (Ll +L2). In order to make this voltage as small as possible, it is sufficient to make L2 small. Therefore, by grounding point 82 in Figure 1 and short-circuiting L2 with the ground between El +"'2, we reduced L2. You can get the same effect as .

Therefore, as shown in Figure 2(b), 82 points are connected to the capacitor C.
It is shown by the formula that the same effect as multi-point grounding can be obtained even if the grounding is done through 2. Similarly to Fig. 2(a), the second
The sheath surge voltage v' at 82 points in Figure (b) is determined by the following equation.

Ding T ・・・・・・・・・・・・ (2) Here, L, CI +L2 CI +L2 C2 As is clear from formula (2), the larger C2/CI becomes, the smaller the sheath surge voltage ■1 becomes. . For example, L2/L, -3,C
When calculated under the conditions of 7/C, -10, the maximum value V of ■ is the second
Figure (a) In other words, in the case of single point grounding ■-s

SO, 75U, whereas in the case of two-point grounding in Figure 2(b), namely point E and point 82 grounded via C2, the maximum value of ■1 is V'=
0.180, suppressed to about 1/4
I can see that I got S. Here, since the value of C1 is about several tens/IF/m in the case of a gas-insulated switchgear, a sufficient suppressing effect can be obtained if the value of C2 is about 01 μF.

The impedance for a commercial frequency of 50 Hzt or 5 QHz, which is still 0.1 μF, is approximately 30 kΩ, which is a sufficiently high impedance, so that an induced current generated by the current flowing through the main conductive part and circulating between the container section and the ground point. is suppressed to an extremely small value, and no mold occurs during heat generation in the container section.

Therefore, FIG. 3 shows an embodiment of the present invention. In the figure 2
3 is a metal cylinder containing the switching device 10, and 3 is the center conductor 9.
Jl is a metal cylinder containing a central conductor 9 leading to the exterior, e.g. an outdoor bushing, these cylinders being conductively connected to each other by a flexible conductor 4 to form one container section ing. A grounding net 13 is buried in the ground where the gas insulated switchgear is installed, the metal cylinder 2 is directly connected to this earthing net at point E, and the metal cylinder 3 is connected to the capacitor C2 at point 82.
The trench metal cylinder 11 is connected to the ground network at 81 points via a capacitor C3. By connecting in this way, the sheath surge voltage can be reduced in accordance with the principle described above, and the induced current that heats the metal cylinder of the container section can be suppressed.

In this embodiment, one end of the container section is directly grounded, but the point of direct grounding may be located anywhere within the container section. Also, if the spacing between the multiple grounding points including this directly grounded point is appropriate to reduce the sheath surge 'flf pressure, it is not necessarily necessary to ground all the metal cylinders of the container section, and When each metal cylinder is longer than the appropriate grounding point spacing, it becomes necessary to provide multiple grounding points on one metal cylinder.

〔Effect of the invention〕

As described above, by directly grounding one point in each container section constituting the hermetic container of the gas-insulated switchgear, and by grounding at least one point different from the direct grounding point via a capacitor, the sheath - This reduces electric shock to operators and prevents insulation breakdown between the operating box of equipment such as a disconnector, which is at the same potential as the container, and the low-voltage control wiring inside. Furthermore, since the induced current circulating between the container section and the ground point is suppressed, heat generation in the metal cylinder of the container section can be avoided.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing the generation of bending frequency induced current in an example of a conventional multi-point grounded container section, Fig. 2 is an equivalent circuit to explain the generation mechanism of sheath surge voltage, and Fig. 3 is an explanatory diagram of the present invention. FIG. 2 is an explanatory diagram showing one embodiment of the invention. 2.3.11... Metal cylinder, 4... Flexible conductor, 1゜12... Container division, C,, C,... Capacitor, E
I...direct grounding point, B2. B3...Grounding point grounded via a capacitor. r-person 111, (CI) (b) (c) Figure 1

Claims (1)

[Claims] It is characterized in that only one point in the container section, which is made up of metal cylinders that have built-in main conductive parts and are electrically conductively coupled to each other, is directly grounded, and at least one point different from the grounding point is grounded via a capacitor. Gas insulated switchgear.