JPS6260407A - 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] [Technical Field of the Invention] The present invention relates to a gas-insulated switchgear, and in particular to a method for reducing high voltage locally generated inside gas-insulated equipment due to sudden wave surges generated when a lightning arrester operates. Regarding suppressed improvements.

[Technical background of the invention and its problems]

Gas-insulated switchgears have been widely used in recent years as switchgears for high-voltage circuits used in substations.

This gas-insulated switchgear keeps the busbar, circuit breaker, disconnect switch, and other attached equipment insulated with an insulating gas such as SF or gas sealed in a grounded metal container.
It is used as a switchgear for high voltage circuits.

In the substation shown in FIG. 7, the connection between the aerial power transmission line 1a and the gas insulated switchgear 10 is made by the bushing 2, and the inlet port is connected by the bushing 2 to suppress lightning surges from the aerial power transmission line 1a. It is common to install a lightning arrester 3 near the.

This lightning arrester 3 suppresses lightning surges entering the gas insulated switchgear 10 to below the standard impact insulation strength (hereinafter abbreviated as BIL). The bushing 2 is connected to the line disconnector 4, and the circuit breaker 5 is connected to the busbars 8, 9 via busbar switching disconnectors 6, 7, respectively.

When a lightning surge higher than the operating voltage of the arrester 3 enters this circuit from the power transmission line 1a, this lightning surge is suppressed to a certain value or less by the arrester 3, but the surge waveform suppressed by the arrester 3 has a rise It becomes a fast sudden wave. In such a state, as shown in FIG. 8, the lightning surge before being suppressed by the lightning arrester 3 has a waveform 11 shown by a broken line.
Even if the waveform of a general lightning impulse is
Due to the operation of the lightning arrester 3, this surge waveform changes to a sharp step wave like the waveform 12 shown by the solid line.

Gas-insulated switchgear generally has a coaxial structure, and the surge propagating inside it is hardly attenuated. Therefore, when a sudden wave enters the gas-insulated switchgear, this surge repeats round-trip reflection and causes local damage. It is known that high voltages are generated.

In recent gas-insulated switchgear, it has become possible to install superior zinc oxide type lightning arresters in appropriate locations, and significant IL reduction has become a topic of discussion. By reducing BIL, it becomes possible to provide a compact and inexpensive gas-insulated switchgear. At this time, it has been found that there are cases in which the high voltage locally generated within the gas-insulated switchgear described above exceeds the reduced BIL, which is a major problem in the case of low BIL.

[Purpose of the invention]

The present invention has been made in consideration of the above points, and its purpose is to effectively suppress the local high voltage generation within the gas insulated switchgear, enable a reduction in BIL, and further reduce the size of the switchgear. The purpose of the present invention is to provide a gas-insulated switchgear that is less expensive.

[Summary of the invention]

In order to achieve such an object, according to the present invention, a lightning arrester installed at a connection port such as an inlet or outlet from an aerial power transmission line to a gas insulated switchgear is connected to another gas insulated switchgear. By adopting a three-phase all-in-one busbar structure and arranging a surge suppressor in which a magnetic member is arranged in a cylindrical shape inside a grounded metal container of this busbar, BIL can be reduced.
It is characterized by being more compact and cheaper.

[Embodiments of the invention]

An embodiment of the gas insulated switchgear of the present invention will be described below with reference to FIGS. 1 to 4. The same parts as in FIG. 7 are given the same reference numerals.

A bushing 2 is installed for connecting a connection part 1 from an aerial power transmission line 1a, for example, and a lightning arrester 3 is connected to the lower part of the bushing 2.

A surge suppressor 20 is connected from the top of the lightning arrester 3, and the other end of the surge suppressor 20 is connected to the circuit breaker 5 through the grounding device 13 having the grounding operation mechanism 18 and the disconnector 4 having the disconnector operation mechanism 16. It is connected to one outlet, and a voltage transformer 14 is installed in this outlet. Further, the other sunrise portion of the circuit breaker 5 is connected to the live buses 1, 8, and 9, respectively, via bus disconnectors 6 and 7 each having a disconnector operating mechanism 16. Note that the circuit breaker 5 includes a circuit breaker operating mechanism 17 and is installed by a frame 19.

The surge suppressor 20 has a three-phase integrated structure, with three-phase conductors 21.21a and uN (not shown) in a grounded metal container 22.
21b, and these conductors 21.21a, 21b are connected to each phase. A cylindrical magnetic member 23 is formed by stacking a large number of thin donut-shaped plates made of iron, for example, with an insulating sheet in the approximate center of the metal container 22 in a direction along the central axis.
The conductors 21.21a and 21b are configured to penetrate through the hollow part of the cylindrical magnetic member 23.

Next, the operation of the present invention will be described. Magnetic materials generally have a large relative magnetic permeability. For example, iron has μ=s, ooo, and a magnetic flux s, ooo times that in a vacuum is generated. Therefore, if such a magnetic material is installed inside a grounded metal container, the inductance of this portion will become considerably large. For example, outer diameter 100cm, thickness 2cm
m, and the inductance L of a 1 m long iron is μ. :Magnetic permeability in vacuum, μ=5,000, do
: Outer diameter of the magnetic member 23.

di: inner diameter of the magnetic member 23; nn=natural logarithm.

This large inductance is caused by the sudden wave that occurs when the lightning arrester operates (see waveform 12 in Figure 8).
It has the effect of softening.

To further explain this, in the equivalent circuit shown in FIG. 3, the equivalent inductance 27 is the equivalent inductance of the magnetic member 23 given by equation (1), and the equivalent resistance 26 is the characteristic impedance of the gas-insulated switchgear. be. The current flowing through this equivalent resistor 26 represents the surge propagating within the gas insulated switchgear, and 25 represents the source of the surge surge due to the operation of the lightning arrester. Now consider a simple step wave as the surge waveform of the source 25.

Assuming that a step wave is generated at t-O, the current i flowing through the resistor 26 can be found by solving the circuit equation (2) shown in the first order.

di L −+Ri=V (2) Equation (2) that satisfies the initial condition that t 1=0 and n=O (2) where R is the resistance value of the resistor 26, L is the inductance value of the equivalent inductance 27, represents the operating voltage of the lightning arrester.

is given by The change in current i is shown in FIG. 4. In other words, when the vertical axis represents current (A) and the horizontal axis represents time (seconds), current i changes like a curved line. It can be seen that by providing the magnetic member 23 in the surge suppressor 20 in this manner, the waveform entering the gas insulated switchgear is considerably rounded.

In addition, since the sum of the three-phase currents becomes zero for alternating current, no magnetic field is generated by the alternating current, and the cylindrical magnetic member 23 made of magnetic material does not act as an inductance. The cylindrical magnetic member 23 made up of the following does not become saturated.

Next, we will discuss the effects.

The voltage change rate given by equation (3) is maximum when 1=0, but let's find the main frequency components at this point. By differentiating i given by equation (3) with respect to t and substituting 1=0, the following equation is obtained as the current change rate at 1=0.

Changes in the voltage applied to the resistor 26, that is, the resistance value R. Generally, the voltage V with the peak value V and the frequency f is v == V si
It is expressed as n 2 tc ft - (6), and the voltage change rate at 1 = 0 is 0. Assuming that the voltage change rate given by equation (5) and the voltage expansion rate given by equation (7) are equal, If you do, you will get . R=70Ω, L=20μ
If H is substituted, the frequency f becomes 550 kHz. Therefore, the current waveform shown in FIG. 4 includes only frequency components of 550 kHz or less, and even if this surge waveform propagates through the gas-insulated switchgear, high frequencies of 550 kHz or more cannot be generated.

The frequency of the local high voltage that is currently a problem is IMHz.
As described above, if the surge suppressor 20 according to the present invention is installed, high frequencies that cause insulation problems cannot be generated, and IL can be significantly reduced. (Here, the standard impact insulation strength is again abbreviated as BIL.) Here, the surge source 25
As the generated voltage, we assumed a simple step wave with a wavefront length of zero, but in reality, the wavefront length is not zero, as shown in waveform 12 in FIG. The waveform that enters the gas-insulated switchgear has a smoother waveform than the waveform shown in FIG. Further, by making the cylindrical magnetic member 23 made of a magnetic material larger, the inductance becomes larger, and it becomes possible to suppress surges at lower frequencies. In the above explanation, only one phase is considered,
Induction to other phases was not considered. However, even if the influence of other phases is considered, there is no essential difference in the operation and effect of the above embodiments.

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

The same parts and parts having the same functions as those in FIG. 2 are given the same reference numerals. That is, a cylindrical resistor 24 is installed inside a cylindrical magnetic member 23 made of a magnetic material, with both ends thereof electrically connected to a grounded metal container 22. In terms of insulation design, it is preferable that the central axes of the cylindrical resistor 24 and the grounded metal container 22 are aligned.
The resistance value R (Ω) of the resistor 24 in the central axis direction is set to satisfy the following formula.

゛ R≧6L (9) However, L is the inductance of the bus bar 21 due to the magnetic member 23, and the unit is μH. That is, L is the inductance given by equation (1).

When the surge suppressor 20 as described above is installed, the sudden wave surge propagating in the gas-insulated switchgear tends to flow through the case where the inductance is minimized, and for example, the high-frequency surge propagates through the conductor of the coaxial structure. In this case, the current tends to flow outside the inner conductor and inside the outer conductor. Therefore, if the cylindrical resistor 24 is installed inside the grounded metal container 22, the high frequency current tends to flow through the resistor 24 because the inductance becomes small.

A large resistance value is preferred in order to attenuate the high frequency current, but if it is made too large, the high frequency current will no longer flow through the cylindrical resistor 24, but instead will flow through the grounded metal container 22. It was found that there is an optimal resistance value that most effectively attenuates high frequencies. This optimum value can be obtained by considering the equivalent circuit shown in FIG. That is, the resistor 28 indicates the equivalent resistance (resistance value R) of the resistor 24, and the inductance 27 indicates the equivalent inductance (inductance value L) of the cylindrical magnetic member 23 made of a magnetic material given by formula (1). ing. When a current with a frequency of f flows through this parallel circuit, the resistance 28
The power P consumed in is given by the following equation.

However, ■ represents the terminal voltage of the resistor 28.

In equation (10), P is maximum when R = 2πfL
...(11). The frequency of high-frequency surges generated in gas-insulated switchgear is
Although it varies depending on the size and configuration of the gas-insulated switchgear, it is generally known to be a value of I MHz or higher.

By substituting f≧IMHz into equation (11), the following equation is obtained as the value of R.

R≧6L (12) Here, the unit of R is Ω, and the unit of B is μH.

At this time, if L=20μH and the lower limit given by equation (12) is the value of R, then R=120Ω. It can be seen that although the characteristic impedance of the gas-insulated switchgear is approximately 70Ω, it is attenuated. Higher frequencies can be attenuated more effectively.

With such a structure, the resistor 24 exhibits a tamping effect, and the possibility of LC resonance due to the inductance exhibited by the magnetic member 23 is reduced.

In the above explanation, iron was considered as the magnetic material, but other magnetic materials with large μ, such as permalloy, have μ=100,
000. For pure iron, μ = 200,000, and for supermalloy, μ = 1,000,000. A similar effect can be obtained with a smaller cylindrical magnetic member.

In particular, a magnetic material made of a thin plate of pure iron is known to have good high frequency characteristics, and is convenient for the embodiment of the present invention.

〔Effect of the invention〕

As explained above, according to the present invention, a surge suppressing section made of a cylindrical magnetic member is provided at the connection section of the gas insulated switchgear with the aerial power transmission line.

This makes it possible to prevent the generation of local high voltages, which is the biggest problem in reducing BIL, and to reduce BIL. Furthermore, it is possible to provide a gas insulated switchgear that is more compact and inexpensive.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional side view of the gas insulated switchgear of the present invention, Fig. 2 is a cross-sectional side view of the surge suppressor shown in Fig. 1, and Fig. 3 is a schematic diagram of the surge suppressor shown in Fig. 2; FIG. 4 is a step wave response waveform diagram of the surge suppressor in FIG. 3. FIG. 5 is a cross-sectional side view of the main part of another embodiment of the present invention, FIG. 6 is a schematic diagram of the same parts as FIG. 5, FIG. 7 is a single line diagram showing the configuration of a general substation, and FIG. FIG. 8 is a waveform diagram showing the principle of generation of a sudden step wave due to the operation of the lightning arrester shown in FIG. 1... Connection part, 1a... Aerial power transmission line, 2
...Bushing, 3...Surge arrester, 4...
Disconnector, 5... Circuit breaker. 10...Gas insulated switchgear, 13...Grounding device, 2
0... Surge suppressor, 22... Metal container, 23
...Magnetic member, 24...Resistor.

Claims (4)

[Claims] (1) In a gas-insulated switchgear in which a high-voltage conductor is insulated and held in a grounded metal container filled with insulating gas, high voltage is drawn into or out of the gas-insulated switchgear from an aerial power transmission line via a bushing. At the connection part, a lightning arrester is installed at the bottom of the bushing, and a bus bar for connecting a switching device such as a disconnector from the connection part between the bushing and the lightning arrester is of a three-phase all-in-one type. A gas insulated switchgear characterized by having a surge suppressor provided with a cylindrical magnetic member installed inside. (2) The gas insulated switchgear according to claim 1, wherein the surge suppressor is formed of a cylindrical magnetic member or a plurality of magnetic materials formed into a cylindrical shape. (3) The gas insulated switchgear according to claim 1, wherein the surge suppressor is constructed by arranging a cylindrical resistor or a plurality of cylindrical resistors inside a magnetic member. (4) The surge suppressor is formed so that R≧6L, where the inductance L (μH) of the bus bar due to the magnetic member and the resistance value R (Ω) in the direction of the center axis of the high voltage conductor of the resistor Gas insulated switchgear according to scope 3.