JPH0457053B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] This invention relates to a charging method for a ground fault phenomenon caused by a restriking surge when the charging current of an SF ₆ gas disconnector is stored in a metal container at ground potential together with SF ₆ gas. Concerning current shear break test circuit. [Technical Background of the Invention] In a substation, a disconnector is 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, chopsticks 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 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. do. In addition, disconnectors C, E,
The disconnector I opens and closes the bus bar 1 when the K, N, and wire disconnectors f are open. 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 point of contact opening, 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 _v2 at that time. It remains. Since the power supply voltage v ₂ changes further, restriking occurs again at the interelectrode voltage e ₂ . Below, in the same way, the voltage between electrodes is
Re-ignition is repeated with e ₃ , e ₄ , e ₅ , e ₆ , e ₇ , e ₈ , ...
As the distance between the poles of the disconnector gradually increases, the insulation between the poles of the disconnector, which in many cases is e ₈ > e ₇ >... > e ₂ > e ₁ , recovers and increases to more than twice the peak value of the power supply voltage. If this happens, the restart or disconnection is complete. 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. During restriking, a high frequency current flows between the poles of the disconnector. If the disconnector cuts this high frequency current at the first current zero point as shown at point x in Figure 3b, the voltage on the load side line will remain at the voltage at point y in Figure 3a. 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 peak value of the power supply voltage and the load side line is restriked at the peak value of the power supply voltage of opposite polarity. It has been known that when an SF ₆ gas disconnect switch is re-ignited, the surge voltage generated at that time may cause a ground fault between the poles and the metal container at ground potential. The ground fault voltage at this time is considerably lower than the static withstand voltage when the disconnect switch is open or closed, and when a wire simulating a restriking arc is installed between the poles of the disconnect switch. The arc discharge between the poles of the disconnect switch has a large influence on this. Inside the metal container at ground potential of the SF ₆ gas disconnector is
The disconnect section containing the SF ₆ gas is normally arranged as shown in FIG. 1 is a movable electrode, 2
3 is a movable shield, 3 is a fixed electrode, and 4 is a fixed shield. Re-ignition when the charging current is cut off occurs when the movable electrode 1 is in the middle of opening. Therefore, restriking occurs between the tip of the movable electrode 1 and the fixed shield 4, and occurs in a state where the potential distribution between the electrodes is quite unequal. Therefore, the ground fault phenomenon caused by the restriking surge is affected by the polarity. FIG. 5 is an example of a charging current disconnection test circuit for a conventionally used SF ₆ gas disconnector. 5 is a test SF ₆ gas disconnector (hereinafter referred to as the test disconnector),
6 is a bushing to which the fixed side of the test disconnector 5 is connected, 7 is a bushing to which the movable side of the test disconnector 5 is connected, 8 is a metal container of the test disconnector 5 at ground potential, and 9 and 10 are loads, respectively. side and power supply side capacitors, 11 is a reactor whose one end is connected to the fixed side electrode via the bushing 6, and the other end is connected to one end of the power supply side capacitor 10 and the secondary winding of the transformer 12; 13 is a reactor; An AC power supply is connected to the primary winding of the transformer 12, and 14 is a compensation reactor connected in parallel to the AC power supply 13. In this circuit, the surge voltage at the time of restriking is almost determined by the series circuit of the load side capacitor 9, the reactor 11, and the power supply side capacitor 10. In FIG. 5, the fixed electrode is connected to the reactor 11. However, it has been known that a surge voltage may cause a ground fault between the electrodes and the metal container 8 at ground potential. It is becoming known that polarity has an effect on this ground fault phenomenon. With the recent increase in voltage, it is becoming impossible to ignore this ground fault phenomenon. So, if
Even if we focus on the influence of polarity and consider this ground fault phenomenon for the test disconnector 5 connected and installed as shown in Fig. 5, (a) the test disconnector 5 It was necessary to connect the movable electrode to the reactor 11 by changing the installation method or (b) changing the laying route of the connection line. However, in case (a), it is necessary to dismantle, move, and reassemble the test disconnector 5, and in case (b), in order to support the connection wire and ensure electrical insulation distance,
New supports and a large amount of space will be required. Therefore, with the conventional well-known arrangement, problems occur due to the influence of ground faults as the voltage increases, and if the influence of polarity is taken into consideration, it is necessary to change the connection to connect the movable electrode and the reactor. There was a problem. [Purpose of the Invention] This invention was created in view of the fact that, with the recent increase in voltage, it has become impossible to ignore the ground fault phenomenon between the poles and the metal container at ground potential due to surge voltage.
Focusing on polarity with respect to ground fault phenomena, tests were conducted with the movable electrode connected to the reactor.
It is an object of the present invention to provide a charging current and disconnection test circuit for an SF ₆ gas disconnector, which does not require reconnecting the bushings of the disconnector under test and can therefore reduce the number of test methods. [Summary of the invention] This invention connects an outlet terminal that is electrically connected to the movable side of a test SF ₆ gas disconnector to a reactor connected to the power supply side, and also connects it to the fixed side of the disconnector. The above object is achieved by connecting the output terminal to the load side capacitor connected to the load side. [Embodiment of the Invention] The present invention will be described below with reference to an embodiment shown in FIG. The SF ₆ gas as well as the disconnection section, that is, _the movable electrode 21, the movable shield 22, and the fixed electrode (although not clearly shown in the figure, 23
), store the fixed side shield 24,
Output terminals such as bushings 26 and 27, which are electrically connected to the fixed electrode and movable electrode 21 established in the metal container 28, are electrically connected to the load side capacitor 9 and the reactor 11, respectively.
In other words, the movable side of the disconnector 25 is connected to the reactor 11 on the power supply side, which is different from the above-mentioned conventional example; other than this, the configuration is the same as that in Fig. 5, so the explanation thereof will be omitted here. do. Hereinafter, the operation of the charging current leakage test circuit configured as described above will be explained. When the charging current is interrupted by the SF ₆ gas disconnector 25 under test, the voltage polarity relationship on the load side and the power supply side of the SF ₆ gas disconnector 25 under test is as shown in FIG. Focusing on the case where the power supply side and load side of the disconnector, where the maximum surge voltage occurs, are re-ignited at the power supply voltage peak values of opposite polarity, the polarity relationship can be distinguished between points a and b shown in the figure. Ru. Point a indicates that the load side was re-ignited with negative polarity and the power source side was positive polarity, and point b indicates that the load side was re-ignited with positive polarity and the power source side was negative polarity. Table 1 shows the relationship between the connection state of the disconnector outlet terminal, the polarity of the movable electrode with respect to the fixed electrode when restriking between poles, and the polarity of the restriking surge voltage with respect to the metal container at points a and b. This is what I wrote about.

[Table] On the other hand, Fig. 7 shows how sparks are generated when the disconnector is re-ignited between the poles. Note that the same parts as in FIG. 4 are designated by the same reference numerals, and their explanation will be omitted. In FIG. 7, 5 is SF ₆ gas, 8 is a metal container at ground potential, and when a voltage is applied between the movable electrode 1 and the fixed shield 4, the leader 29 branches from the tip of the movable electrode 1. It occurs like this. When one portion 30 of the branch-like leader 29 reaches the stationary shield 4, restriking occurs between the poles. When restriking occurs, a surge voltage is generated. This surge voltage is applied between a portion 31 of the branch-like reader 29 and the metal container 8 at ground potential. Since the electric field is concentrated at the tip of the leader portion 31, the leader 31 advances and reaches the metal container 8 at the ground potential as shown at 32, causing a ground fault. As mentioned above, the process of restriking between the poles and causing a ground fault due to a surge can be divided into the following two processes in terms of leader development. 1 Evolution of the leader during discharge between poles. 2 Evolution of the leader during a ground fault due to surges occurring as a result of 1). The leader development in 1) above occurs more easily when the movable electrode 1 has a positive polarity with respect to the fixed shield 4 than when it has a negative polarity, and the leader development in 2) above occurs when the surge voltage is applied to the metal container. On the other hand, it occurs more easily when the polarity is positive than when it is negative polarity. this is,
This corresponds to the fact that the breakdown voltage of the unequal electric field of SF ₆ gas is lower in positive polarity than in negative polarity. Therefore, a ground fault is likely to occur due to a restriking surge under the following two polarity conditions. 1 When the polarity of the movable electrode with respect to the fixed electrode is positive during interpole restriking. 2 When the polarity of the restriking surge voltage with respect to the metal container is positive. Incidentally, in Table 1, the above two polarity conditions are satisfied when the connection condition of the disconnector outlet terminal is the connection according to the embodiment shown in FIG. In fact, according to the charging current shedding test results of the SF ₆ gas disconnector 25 under test, the movable electrode 21 was re-ignited with positive polarity with respect to the fixed shield 24, and the surge voltage was with positive polarity with respect to the ground. The ground fault voltage was the lowest when it was re-ignited and the surge voltage was positive with respect to the ground. This is because, as shown in FIG. 5, the movable electrode 21 is connected to the reactor 11 on the power source side. In addition, when conducting a test focusing on the ground fault phenomenon caused by the charging current of the SF ₆ gas disconnector or the restriking surge of the disconnector, it is sufficient to conduct the test focusing on the conditions where the ground fault voltage is the lowest. It is. [Effects of the Invention] According to the present invention, the test can be performed under the conditions where the ground fault voltage is the lowest, so there is no need to change the connection of the disconnector bushing and perform the test as in the past, and therefore the number of steps required for the test can be reduced. We can provide charging current and disconnection test circuits for SF ₆ gas disconnectors.

[Brief explanation of drawings]

Figure 1 is a single-line diagram showing an example of a substation configuration.
Figure 2 is a load-side ground voltage waveform diagram when the charging current is interrupted by a disconnector, Figure 3 is a temporal enlargement of the restriking phenomenon at point a in Figure 2, and Figure 4 is the sample SF. Figure 5 is a schematic diagram showing an example of a conventional charging current disconnection test circuit of the _SF6 gas disconnector, and Figure 6 is a diagram showing the charging current disconnection test circuit of the _SF6 gas disconnector according to the present invention. FIG. 7, a schematic diagram of an embodiment of the test circuit, is an explanatory diagram of sparks when re-igniting between phases of a disconnector. 21...Movable electrode, 22...Movable side shield,
23...Fixed electrode, 24...Fixed side shield, 2
5... Test SF ₆ disconnector, 26, 27... Bushing, 28... Metal container, 29... Leader, 9,1
0...Load side and power supply side capacitors, 11...
Reactor, 12...Transformer, 13...AC power supply, 14...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. , has a fixed electrode inside the fixed side shield together with SF ₆ gas in a metal container at ground potential, a movable electrode that can make contact with and separate from this fixed electrode, and a movable electrode that accommodates this movable electrode when opened, and the fixed side shield. A test SF ₆ gas disconnector has a movable side shield that can be connected to and separated from the disconnector, and an outlet terminal electrically connected to the movable side of the disconnector is connected to the reactor side, and the Charging current and disconnection test circuit for an SF ₆ gas disconnector in which the output terminal electrically connected to the fixed side is connected to the load side capacitor.