JPS6332005B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas-insulated line connection bus that connects overhead lines and electrical equipment.

Recently, the application range of high-voltage power equipment using gases with excellent insulating properties such as SF ₆ gas has been expanded, and in particular high-voltage substations or switchyards, overhead The wire 1 is connected to a bushing 2, a gas-insulated connection busbar 3, and a disconnection section 5.
In many cases, a system connected to a substation or switchyard 6 is constructed through a substation or switchyard 6.

Conventionally, lightning arresters have been used for the purpose of surge overvoltage protection in high-voltage substations or switchyards, but in systems with connection buses on the line side as described above, when the disconnection section 5 is open, the overhead line 1 Since the connection bus bar cannot be protected in the event of a surge entering from
To protect this, lightning arresters 7 are installed at the end of the line as shown in Figure 2.
A method is used in which the connection bus bar 3 is protected from overvoltage by adding the following.

The problem with protecting the line-side connection bus from surges using a surge arrester at the line end is that when the connection bus becomes longer and the distance between the lightning arrester installation point 8 and the disconnection point 9 becomes greater, the surge protection between the surge arrester and the disconnection point 9 becomes longer. There is a possibility that the voltage at the disconnection point 9 may rise abnormally due to the round trip reflection. In particular, with gas-insulated busbars, the busbar is housed in the ground tank 4 and is gas-insulated, so there is almost no loss, and there is no surge voltage attenuation or waveform distortion, so the waveform of the intruding wave from the overhead line 1 is In the case of a steep rise in the potential at the disconnection point 9, the rise in potential at the disconnection point 9 increases to about twice the protection voltage of the lightning arrester 7, and the overvoltage protection effect of the surge arrester 7 becomes almost ineffective in the vicinity of the disconnection point 9. In order to protect this connection bus bar, a lightning arrester must also be added to the disconnection point 9. In the case of a longer connection busbar, a plurality of lightning arresters may even be required at the midpoint of the connection busbar 3, making it difficult to economically apply a long line-side connection busbar.

The present invention has been made to solve these problems.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

That is, as shown in FIG. 3, a capacitor 10 with a capacity of C (μF) is added to the line end 8 of the connection bus 3 together with a lightning arrester 7. The effect of this capacitor is to reduce the wave front steepness of the intruding wave surge by the surge impedance Z and capacitance C of the overhead line 1, and to reduce the rise time of the surge wave between the connection point 8 and the disconnection point 9 of the connection bus 3. The goal is to make the time sufficiently longer than the round trip time. By the way, the capacitance C of the capacitor 10 required to suppress the potential at the disconnection point 9 to less than about 1.2 times the protection level of the lightning arrester 7 is
(μF) is the surge impedance Z of the overhead line
(Ω), the surge propagation speed v (m/μs), and the length l (m) between the connection point 8 and the disconnection point 9 of the connection line are roughly given by the following equation.

C>5×l/v・Z (μF) In a general system, Z is 300 to 400Ω and v is 300m/
μs, C>50×l (pF) That is, by adding a capacitor of approximately 50 pF per meter of length of the connected bus in parallel to the lightning arrester 7, the surge voltage on the connected bus can be limited to a sufficiently low level.

As described above, according to the present invention, it is possible to perform surge protection that is much more economical and highly reliable than adding a lightning arrester near the disconnection point or at the intermediate point of the connection bus bar.

Note that the additional capacitor does not necessarily have to be attached to the end of the line, but can also be placed at the midpoint of the connection bus. However, in this case, it must be noted that since the surge impedance Z of the connection bus bar is smaller than that of the overhead line, the required capacitance increases in inverse proportion to the value of Z.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of a system connected from overhead lines to a substation or switchyard through a gas-insulated connection busbar, Figure 2 is an explanatory diagram of a system in which a lightning arrester is installed to protect the connection bus from surges, FIG. 3 is an explanatory diagram showing a system using connection bus bars, which is an embodiment of the present invention. Note that the same reference numerals in the figures indicate the same or corresponding parts. In the figure, 1 is an overhead line, 3 is a connection busbar, 4 is a ground tank, 5 is a disconnection section, 6 is a substation or switching station (electrical equipment), 7 is a lightning arrester, and 10 is a capacitor.

Claims (1)

[Claims] 1. A gas-insulated device housed in a container filled with insulating gas, one end connected to an overhead line and a lightning arrester for surge protection, and the other end connected to electrical equipment via a disconnector. In the connection bus for the line, the steepness of the wave front of the intruding wave surge is reduced, and the rise time of the surge wave is made sufficiently longer than the time it takes for the surge to travel back and forth from one end of the connection bus to the connection with the disconnector. A gas-insulated line connection bus bar, characterized in that a ground capacitor for the purpose of the connection is connected to the one end of the connection bus bar. 2 The ground capacitor has a capacity C, where C>K・l/V・Z K: Constant, l: Length of the connection bus between the overhead line and the disconnection section, V: Propagation speed of surge waves on the connection bus, Z The gas-insulated line connection busbar according to claim 1, characterized in that it has the following: surge impedance of an overhead line.