JPH0361295B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention relates to the re-ignition of an SF ₆ gas disconnector in which a disconnecting section is housed together with SF ₆ gas in a metal container at ground potential when the charging current is interrupted. This invention relates to a charging current shear breakage test circuit for grounding phenomena caused by surges.

[Technical background of the invention]

In substations, disconnectors are opened and closed for the purpose of disconnecting equipment within the substation from the power system and switching circuits. The opening and closing of a disconnector is performed while the adjacent cable breaker is open, and the disconnector switches on and off a minute charging current in a short line within the substation leading to the cable breaker.

Figure 1 shows an example of the configuration of a substation.
BUS1, BUS2 are bus lines, A, B, C, D, E,
F, G, H, I, J, K, L, M, N, O are disconnectors, a, b, c, d, e, f wires and disconnectors, TR
1, TR2 is a transformer, and PL1, PL2, and PL3 are power transmission lines.

In such a configuration, for example, the disconnector A opens and closes the short line m up to the breaker a, and the disconnector D opens and closes the line section n when the disconnector E and the breaker b are open. Open and close. In addition, disconnectors C, E,
When the K, N, and breaker f are open, the disconnector I opens and closes the bus 1.

In those connected in this way, disconnector A
Substations where SF ₆ gas disconnectors are used as ~D are disconnectors A~D and shiya disconnectors a~ as shown in Figure 1.
There are two main types of substations: fully gas-insulated substations, in which all busbars BUS1, BUS2, etc. are housed in a metal container filled with SF ₆ gas, and composite gas-insulated substations, in which only the busbars are overhead wires.

It is known that when the charging current is cut off by a disconnector, many restrikes occur, resulting in a load-side line-to-ground voltage waveform as shown in FIG. That is, the minute charging current is interrupted almost simultaneously with the contact opening point OC, and at that time, the power supply voltage v ₁ at the instant of the interruption remains on the line on the load side. Since the power supply voltage v ₁ is alternating current and changes, the difference between the residual voltage of this line and the power supply voltage is applied between the poles of the disconnector.
At this time, the disconnector is still in the process of opening, and the inter-electrode insulation recovery is not sufficient, and it is re-ignited at the inter-electrode voltage _e1 .
Then, since the capacitance of the line is on the order of several hundred to several thousand picofurads, as soon as the flowing transient current attenuates, a disconnection occurs, and the voltage on the load side line increases to a level equal to the power supply voltage V ₂ at that time. It remains.
Since the power supply voltage v ₂ changes further, restriking occurs again at the interelectrode voltage e ₂ . Thereafter, restriking is repeated in the same manner at interelectrode voltages e ₃ , e ₄ , e ₅ , e ₆ , e ₇ , e ₈ , . . . . As the distance between the poles of the disconnector gradually increases,
In most cases, e ₈ > e ₇ >...e ₂ > e ₁ , but once the insulation between the poles of the disconnector recovers and the power supply voltage reaches more than twice the peak value, the re-ignition and disconnection will be completed. .

A surge voltage is generated during these restrikes. For example, the phenomenon of re-ignition occurs at point a in Figure 2, and if this is expanded in time and conceptually shown, the third
It will look like the figure. The surge voltage at this time has a high frequency because the line on the load side that is opened and closed is short, and in many cases, its fundamental vibration reaches several hundred KHz.

At the time of restriking, a high frequency current flows between the poles of the disconnector. If the disconnector disables this high frequency current by x in Figure 3b
When the current is cut off at the first zero point as shown in the dot,
The voltage on the load side line remains at the voltage at point y in figure a. However, this does not occur in real systems. When the transient current at the time of restriking has sufficiently attenuated, a break occurs, and after the voltage on the load side line matches the power supply voltage, the break occurs. Many restrikes occur when the charging current is cut off by a disconnector, but the maximum residual voltage on the line is the peak value of the voltage on the power supply side. When considering the maximum restriking surge, it is sufficient to consider when the power supply side is restriked at the current voltage peak value and the load side line is restriked at the opposite polarity power supply voltage peak value.

In order to quickly cut off the charging current of a disconnector that exhibits the above-mentioned phenomenon in an actual system, a charging current cutoff test circuit shown in FIG. 4 has been used. 1 is the SF ₆ gas disconnector under test, 2 is the load side capacitor,
3 is a transformer, and 4 is a short circuit generator. The load-side capacitor 2 simulates the capacitance of the load-side line of the disconnector 1, and the value of the capacitance is determined by the value of the charging current to be opened and closed.

However, it has been known that when the SF ₆ gas disconnector 1 is re-ignited, a ground fault may occur between the poles and the metal container at ground potential due to the surge voltage generated at that time. The ground fault voltage at this time is considerably lower than the static withstand voltage when the disconnect switch 1 is open or closed, and when a wire simulating a restriking arc is installed between the poles of the disconnect switch 1. The arc discharge between the poles of the disconnector 1 has a large influence on the circuit phenomenon.

Focusing on the ground fault phenomenon caused by a restriking surge when the charging current of SF ₆ gas disconnector 1 is interrupted, in order to conduct a test equivalent to the actual system, it is necessary to calculate the surge voltage that occurs during restriking. It must be made equivalent to the actual system.
However, this is difficult with the conventional charging current shear break test circuit shown in FIG. That is, the frequency of the restriking surge is mainly determined by the inductance of the load-side capacitor 2, transformer 3, and short-circuit generator 4. Since the inductance of the transformer 3 and the short-circuit generator 4 is large, the frequency of the surge becomes slower than that of the actual system. In this case, the frequency of the high-frequency current at the time of restriking also slows down, making it easier to cut off the high-frequency current. As mentioned above, in Figure 3, a break occurs at the first current zero point of the high-frequency current at the time of restriking,
This is because a voltage higher than the peak value of the power supply voltage may remain on the load side of the disconnector.

[Purpose of the invention]

The purpose of this invention is to obtain a charging current disconnection test circuit for a ground fault phenomenon caused by a restriking surge when the charging current of an SF ₆ gas disconnector is interrupted, which is equivalent to an actual system.

[Summary of the invention] In order to achieve the above object, this invention
The sum of the capacitance of the load-side capacitor connected to the load side of the SF ₆ gas disconnector and the stray capacitance of the bushing of the disconnector connected to this is calculated as the sum of the capacitance of the load-side capacitor connected to the load side of the SF 6 gas disconnector, and the stray capacitance of the bushing of the disconnector connected to the reactor connected to the power supply side of the disconnector. The capacitance of the power supply side capacitor connected to the power supply side of the disconnector shall be at least twice the stray capacitance of the bushing of the disconnector connected to the first and second bushings of the disconnector. The present invention is characterized in that the stray capacitance is five times or more the sum of each stray capacitance and the capacitance of the load-side capacitor.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings. Fig. 5 is a schematic diagram showing an embodiment of a charging current breakage test circuit for an SF ₆ gas disconnector according to the present invention, and Fig. 6 is a schematic diagram showing a surge voltage generated at the time of restriking in the same embodiment. The equivalent circuit of the part that determines most of the parts is shown.

In the figure, a test SF ₆ gas disconnector 12 has a disconnecting section housed together with SF ₆ gas in a metal container at ground potential, and a bushing electrically connected to the disconnecting section, which will be described later, in the metal container. A load side capacitor 13 having a capacitance Cl is connected between the bushing 18 of the disconnector 11 and the ground, and the AC power source 14 is connected to the primary terminal of the load side capacitor 13, and the secondary terminal is connected to the bushing 17 of the disconnector 11. It is a transformer connected to the earth. 15 is a reactor connected between the bushing 17 and one terminal on the secondary side of the transformer 13; 16 is a power supply side capacitor with a capacitance Cs connected between both terminals on the secondary side of the transformer 13; 1
9 is a reactor for compensating the charging current (leading current) connected in parallel to the AC power source 14, and 17 and 18 are bushings of the disconnector 11, and their stray capacitances are C ₁ and C ₂ . ing. Then, the capacitance Cl, Cs of the load side capacitor 12 and the power supply side capacitor 16, the stray capacitance C ₁ of the disconnector 11,
The following relationship is established between C and ₂ .

When C ₂ +Cl=nC ₁ and Cc=m (C ₁ +C ₂ +Cl), n≧2 and m≧5.

This configuration is based on the following points. In other words, in the real system
In order to conduct a test simulating the restriking surge of an SF ₆ gas disconnector, it is necessary to know the magnitude multiple and waveform of the restriking surge in the actual system. For this purpose, digital calculations were performed for a total of 64 disconnectors at nine substations, including fully gas-insulated substations and combined gas-insulated substations, with different layouts. In each calculation, we calculated the case where the load side and the power supply side were re-ignited at power supply voltage peak values of opposite polarity, respectively, so that the maximum surge voltage was generated. A typical example of the surge voltage waveform obtained by calculation is shown in FIG. In this way, the fundamental oscillation frequency of the surge voltage is several hundred K.
Often in Hz. FIG. 8 summarizes the calculation results of the surge multiple at the end of the disconnector. In this way, a maximum surge voltage of 2.3 times was calculated.
In FIG. 5, it is possible to generate a voltage 2.3 times higher than several hundred KHz at the time of restriking as follows. In Figure 6, the peak value of the power supply voltage is
Assuming E ₀ , the voltage on the load side is −E ₀ and the voltage on the power source side is −E 0 .
Consider the case of restriking at E ₀ . Almost simultaneously with the restriking, the voltages of Cl, C ₂ and C ₁ become El′=C ₂ +Cl−C ₁ /Cl+C ₁ +C ₂ E ₀ (1). Then, the series circuit of Cs, L, Cl+C ₁ +C ₂ starts to vibrate. This situation is shown in FIG.
The maximum value Vmax of overvoltage is given by equation (2).

Vmax=2C ₀ /Cl′ (E ₀ +El′)−El′ (2) However, Cl′=Cl+C ₁ +C ₂ and C ₀ =CsCl′/Cs+Cl′.

Here, C ₂ +Cl=nC ₁ , Cs=m(C ₁ +C ₂ +Cl)=
mCl', equation (2) becomes Vmax=E ₀ {2m/m+1(1+n-1/n+1)-n-1/n+1}...(3). For n with m as a parameter
When Vmax is calculated, FIG. 10 is obtained, and when Vmax is calculated for m using n as a parameter, FIG. 11 is obtained. As can be seen from these Figures 10 and 11, n is about 2 or more, and m
If it is set to about 5 or more, a surge voltage of 2.3 times or more can be generated. Note that the frequency of the surge voltage can be set to several hundred KHz by changing the value of the inductance L.

[Effects of the Invention] According to the invention described above, the re-ignition surge caused by the disconnector that occurs at the end of the disconnector in a fully gas-insulated substation and a composite gas-insulated substation in an actual system is suppressed when the charging current is interrupted. By simulating the voltage and focusing on the ground fault phenomenon of SF ₆ gas disconnectors, we can provide a charging current and disconnection test circuit for SF ₆ gas disconnectors that is equivalent to the actual system.

[Brief explanation of drawings]

Figure 1 is a single line diagram showing an example of a substation, Figure 2
The figure shows the load-side line-to-ground voltage waveform diagram when the short line's minute charging current is cut off by a disconnector in the same example.
Fig. 3 is a temporally enlarged view to explain the restriking phenomenon at point a in Fig. 2, and Fig. 4 is a diagram showing an example of a conventional SF ₆ gas disconnector charging current break test circuit. ,
Fig. 5 is a diagram showing a charging current breakage test circuit of the SF ₆ gas disconnector according to the present invention, and Fig. 6 is a part of the same embodiment that determines most of the surge voltage generated at the time of restriking. Fig. 7 is a diagram showing a typical example of the restriking surge waveform obtained by digital calculation of the disconnect switch of the substation in the actual system, and Fig. 8 shows the restriking surge voltage in the actual system. A diagram showing the calculation results of the surge multiple for 64 cases of 9 substations, Figure 9 is a diagram to explain the surge voltage waveform of the test circuit shown in Figure 5, and Figure 10 is the test circuit shown in Figure 5. A diagram showing the relationship between surge voltage and circuit constants,
FIG. 11 is a diagram showing the relationship between the surge voltage and circuit constants of the test circuit shown in FIG. 5. 11... Test SF ₆ gas disconnector, 12... Capacitor, 13... Transformer, 14... AC power supply, 15
...Reactor, 16...Capacitor, 17,1
8...butsuthing, 19...compensation reactor.

Claims (1)

[Claims] 1 Connect an AC power source to the primary terminal of the transformer, connect a power supply capacitor in parallel to the secondary terminal of the transformer, and connect a reactor and a load capacitor in series between both terminals of this power supply capacitor. , a test SF ₆ gas having a disconnecting section housed together with the SF 6 gas in a metal container at ground potential, and having first and second bushings attached to the metal container and electrically connected to the _{disconnecting} section. A disconnector is connected between the load-side capacitor and the reactor, and the sum of the capacitance of the load-side capacitor and the stray capacitance of the bushing to which the load-side capacitor is connected is calculated by connecting the reactor to the capacitor. The stray capacitance of the bushing should be at least twice the stray capacitance of the bushing, and the capacitance of the power supply capacitor should be the sum of the stray capacitance of each of the first and second bushings and the capacitance of the load capacitor. A charging current and disconnection test circuit for an SF ₆ gas disconnector characterized by increasing the charging current by more than 5 times.