JPH0520969B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a power conduit busbar, and particularly to a conduit busbar having characteristics of attenuating steep wave surge voltage.

[Technical Background of the Invention and Problems Therewith] In recent years, gas-insulated switchgears have been frequently used as switchgears for high-voltage circuits used in substations. This is done by storing the busbar, cable breaker, and other attached equipment in a metal container, and then
This metal container is highly stable, inert, nonflammable,
_SF6 gas, which is odorless, harmless, and has a dielectric strength 2 to 3 times that of air, is sealed and used as a switchgear for high voltage circuits.

In such a gas-insulated switchgear, when a circuit breaker or a disconnector operates to disconnect or connect a circuit, a discharge occurs between the electrodes. The surge voltage generated by this discharge is sometimes twice the rated value.
It can be more than double, and the time to reach the peak value of the first wave is less than 100ns, resulting in a high-frequency vibration wave.
In addition, the coaxial structure used for the conduit busbar has extremely good frequency characteristics, allowing voltages with frequencies up to 1 GHz to propagate with almost no attenuation, so surges can be connected directly to the gas-insulated switchgear without attenuation. and other equipment such as transformers, bushings, etc.

Next, the effects of such high frequency voltages on other devices will be explained using a transformer as an example. That is, as shown in Fig. 6, in a conventional GIS type substation, a transformer connected to a gas-insulated switchgear has a winding 2 wound around an iron core 1 of the transformer, and these are insulated. It is housed in a tank 3 filled with oil. Further, the tank 3 is provided with a cooler 4 for cooling the insulating oil and a conservator 5 for preventing deterioration of the insulating oil. Further, the high-voltage lead wire 6 from which the winding 2 is drawn out from a part of is connected to an oil/gas bushing 8 via an oil duct 7, and is further connected to an oil/gas bushing 8 through an oil duct ₇ .
It is connected to a gas insulated switchgear (not shown) by a high voltage central conductor 10 housed in the gas line busbar duct 9. Note that a lightning arrester 11 is provided in the oil duct 7.

In a transformer connected to a gas-insulated switchgear having such a configuration, when the gas-insulated switchgear operates and a high-frequency surge with an extremely high rise is generated, the surge passes through the conduit busbar as described above. applied to the transformer. With regard to the response of transformer windings when such high-frequency surges with high wave front steepness are applied, high-cell cap disc windings, which have excellent impulse voltage resistance characteristics and are often used as high-voltage windings, are used. wire (high series capacitance winding)
We will explain the case when using . That is, when a high frequency surge voltage as described above is applied to the high cell cap disk winding, the potential distribution is not improved even though the high cell cap winding has a large series capacitance. In other words, as shown in Figure 7, the series capacitance is such that the voltage is half (N/2 = 8) of the total turns (N = 16) of the first turn of the first stage and the second stage. However, in the case of a steep wave surge voltage, before the voltage wave that entered the first turn reaches the next turn where N/2 is applied, The peak value will be reached in the first turn. In this way, the improvement of the potential distribution, which is the aim of the high-cell cap disk winding, becomes meaningless in the case of a steep surge voltage. This pointless boundary varies depending on the voltage and capacity of the winding, but it is said that the time required to reach the negative peak value of the first wave is about 0.5 μS or less.

Next, it will be explained whether the lightning arrester 11 can operate and protect the transformer when a high frequency surge is applied. That is, FIG. 8 shows a waveform diagram of steep wave voltages at various parts when the gas-insulated switchgear is activated and a high-frequency surge enters the conduit busbar. First, a steep wave voltage with a voltage peak value of E is oil/gas bushing 8.
Fill the ground capacitance C ₀ with lightning arrester 11
reaches the terminal. At this time, due to the ground capacitance _C0 of the bushing, the peak value of the steep wave voltage becomes slightly smaller E', and the wave front steepness also becomes slightly smaller. In addition, since current flows in the arrester 11 according to its v-i characteristic, the voltage is suppressed below the limiting voltage of the arrester 11, and its peak value becomes E''. Since the wave front steepness does not change in any way, the winding distribution of steep wave surge voltage cannot be improved.

[Object of the Invention] The present invention was proposed in order to solve the above-mentioned drawbacks of the conventional pipeline busbar, and its purpose is to operate a gas-insulated switchgear in a GIS substation. To provide a conduit busbar capable of attenuating high-frequency surges to the extent that the high-frequency surges generated by the high-frequency surges do not cause dielectric breakdown in transformers and other connected equipment.

[Summary of the Invention] The conduit busbar of the present invention reduces the applied surge by disposing a dielectric material around a high-voltage center conductor disposed in a duct, the loss of which increases as the frequency of the applied surge increases. It is designed to significantly attenuate high frequency surges.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be specifically described with reference to FIGS. 1 and 2. Note that the same members as those of the conventional conduit busbar shown in FIG. 6 are designated by the same reference numerals, and the description thereof will be omitted.

In this embodiment, the SF ₆ gas line busbar duct 9
A dielectric material 20 whose loss increases as the frequency of the applied surge increases is attached via a high-resistance metal or semiconductor 21 to a portion around the high-voltage central conductor 10 disposed inside. The dielectric 20 is also in contact with the ground conductor 22 of the SF ₆ gas line busbar duct 9 via a high-resistance metal or semiconductor 21 . The thickness of this high-resistance metal or semiconductor 21 is approximately the skin depth of the material at 1MHz (for example, in the case of tungsten)
180μm) and is attached by methods such as plating or vapor deposition.

In the conduit busbar of this embodiment having such a configuration, the characteristic surge impedance of the coaxial conduit busbar is expressed as Z ₀ =138/√·log ₁₀ (b/a). Here, a is the diameter of the high voltage central conductor 10, b is the diameter of the ground conductor 22, and εr is the relative dielectric constant of the material between the high voltage central conductor 10 and the ground conductor 22. For example, if BaTiO ₃ is used as the dielectric 20, εr≈3000, and if the gas is SF ₆ at 1 atmosphere, εr≈1. The ratio of the surge impedance Z ₁ where BaTiO ₃ is present and the surge impedance Z ₂ where SF ₆ is present is Z ₂ /Z ₁ =55. In other words, an impedance mismatch occurs in this part, and the high frequency voltage V ₀ passing through the pipe with SF ₆ ,
When the current I ₀ reaches a place where BaTiO ₃ is present, the high frequency voltage becomes 1/28V ₀ and the current becomes 55/28I ₀ . Furthermore, since the resistance loss is given by RI ² , the resistance loss increases approximately four times in the region where BaTiO ₃ is present. Moreover, this BaTiO ₃
In a certain area, high resistivity tungsten, nichrome, molybdenum, etc. is applied to the metal surface constituting the high-voltage center conductor 10 and the ground conductor 22 at 1MHz.
Because it is vapor-deposited or plated to about the skin depth, the loss becomes even greater, and the attenuation of high-frequency surges becomes extremely large. Moreover, BaTiO ₃ has hysteresis in electric field E and electric flux D, as shown in FIG. The area surrounded by this curve is a loss, and since the magnitude is constant regardless of the frequency, the loss increases in proportion to the frequency. However, since commercial frequencies have low frequencies, there is almost no loss. By inserting a ferroelectric material into the conduit in this way, only high frequencies can be attenuated due to resistance loss on the surface of the conduit and hysteresis loss inside the ferroelectric material. As a result, dangerous high-frequency surge voltages are no longer applied to the transformer and bushings.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and it is possible to use a polymer such as paper, whose loss angle (tan δ) increases as the frequency increases, as a dielectric material, and a ferroelectric material as a dielectric material. As in the case, the resistance loss in the conductor increases, and in addition, as the frequency increases, tan δ increases, so the loss increases and the attenuation of high frequencies increases, which protects equipment such as transformers and bushings from high frequency surges. be able to.

Further, the shape of the dielectric 30 disposed around the high-voltage central conductor 10 may be configured so that it contacts only the central conductor 10, as shown in FIG. Generally, when a high frequency wave propagates in a coaxial pipe filled with SF ₆ gas, the electric field has a shape as shown in Figure 4. When a material with a high dielectric constant is arranged coaxially around the high-voltage central conductor 1, the electric field is generated as shown in Figure 5.
0 to the ground conductor 22, but propagates only through the interior of the dielectric 30. As a result, at high frequencies, the resistive loss in the conductor increases, and the hysteresis loss or tanδ loss in the dielectric occurs, and the first
The same effects as in the embodiment shown in the figure can be obtained.

[Effects of the Invention] As described above, according to the present invention, as the frequency increases, the material around the high-voltage central conductor, such as ferroelectric material or paper,
By installing a dielectric material that increases tanδ, it is possible to sufficiently reduce high-frequency electrical energy and attenuate high-frequency surges to the extent that equipment such as transformers and bushings does not cause dielectric breakdown due to high-frequency surges. This has the effect of providing an inexpensive and highly reliable conduit busbar.

[Brief explanation of the drawing]

FIG. 1 is an enlarged cross-sectional view of the main part showing an embodiment of the conduit busbar of the present invention, FIG. 2 is a diagram showing the relationship between electric field and electric flux showing hysteresis loss of a ferroelectric, and FIG. 3 is a diagram of the present invention. FIG. 4 is a schematic diagram of a high-frequency electric field propagating through a conventional pipe bus, and FIG. 5 is a schematic diagram of a high-frequency electric field in another embodiment of the present invention. Schematic diagram of electric field, Figure 6 is conventional GIS
Figure 7 is a typical configuration diagram of a transformer's high-cell cap winding, and Figure 8 is a schematic diagram of a high-frequency surge propagating through a GIS substation. 1...Transformer core, 2...Winding, 3...Tank, 4...Cooler, 5...Conservator, 6...
...High pressure lead wire, 7...Oil duct, 8...Oil/gas bushing, 9...SF ₆ gas pipe busbar duct,
10... High voltage center conductor, 11... Lightning arrester, 20...
...Dielectric material, 21... High resistance metal or semiconductor, 22
...Ground conductor, 30...Dielectric material.

Claims (1)

[Claims] 1. A dielectric material whose loss increases as the frequency of the applied surge becomes higher is disposed around a high-voltage center conductor disposed in the duct of the gas-insulated conduit busbar. Conduit busbar. 2. The dielectric is arranged so as to be in contact with both the high-voltage center conductor and the ground conductor, and a high-resistance metal or semiconductor is arranged between the dielectric and the center conductor and between the dielectric and the ground conductor. A pipe busbar according to claim 1, characterized in that: 3 The dielectric is BaTiO ₃ or BaTiO ₃
The pipe busbar according to claims 1 and 2, which is made of a material to which a small amount of SrTiO ₃ , BaSnO ₃ or CaTiO ₃ is added, or is made of NaNO ₂ , PbZrO ₃ or SbSI. 4. The pipe busbar according to claims 1 and 2, wherein the dielectric material is a comonomer such as paper or cellulose, or a polymer having a side chain.