JPH01304679A - Arrester for power transmission cable - Google Patents

Abstract

PURPOSE:To make large amount of electric charge in some ten thousand coulomb possible to pass in a 0.5-1.0 cycle period of operation frequency without causing destruction phenomenon by making a vacuum gap device as a series composing element in which electric current by lightning passes. CONSTITUTION:A lightning arresting element 6 is connected between a pylon and a power transmission cable either having an air gap G1 between them or not. The lighting arresting element 6 is formed by placing an upper electrode 18 and a lower electrode 19 which are kept having a gap between them and being in the opposite side in series in the inside of a vacuum insulating container 16. An electric current by lighting is conducted through the gap. The passable electric charge can be heightened by forming a gap having a long insulating distance and a relatively small surface area due to the phase of electric field formation in a gap in a high vacuum and pinch effect of a large electric current. Passing of electric current by lighting is succeeded by cutting off an electric current of an operational frequency from a power transmission cable within 1 cycle.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention was installed on the ground. It is installed between the above-mentioned above-mentioned above-mentioned above-mentioned tower and an overhead power transmission line that is suspended from a above-mentioned above-mentioned above-mentioned power transmission line which is suspended from a above-mentioned above-mentioned power transmission line through an insulator at a high position above the ground, which is at ground potential, and runs almost parallel to the ground. The present invention relates to an improvement in a lightning arrester for a power transmission line, which prevents lightning accidents in a power transmission system by allowing a lightning current to pass therethrough and blocking current at an operating frequency flowing from the overhead power transmission line following the passage of the lightning current.

[Conventional technology]

As this type of lightning arrester, one shown in FIG. 3 or 4 is known. In the case of FIG. 3, the lightning protection element 6, which has a resistance element containing zinc oxide as a main component built into the insulator tube, is fixed to the arm 1a of the steel tower 1 through the metal fitting 2. , this lightning arrester element 6 and the air gap G1 formed between the lower metal fitting 6a of the lightning arrester element 6 and the rod electrode 7 attached to the lower metal fitting 3m of the suspension insulator 3 suspending the power transmission line 4. It constitutes a lightning arrester for electric wires, and makes it possible to retransmit power even if the lightning arrester element 6 should fail. Figure 4 shows the 3rd stage, taking into consideration the installation of the lightning arrester.
5a in these figures shows a case where the air gap Gl in the figures is omitted and the lightning arrester for a power transmission line is configured only with the lightning arrester element 6.

5b has been conventionally attached. This is an arc horn for maintaining a suspended insulator, and is a guide path for the arc foot point when the arc tries to leave the suspended insulator due to the electromagnetic force based on the shape of the current path including the arc when the surface of the suspended insulator flashes. By forming the arc foot point and staying at the tip of the arc,
The operation of these lightning arresters will be explained below, in which a short arc separates from the suspended insulator and serves to protect the suspended insulator from thermal damage.

In FIGS. 3 and 4, if there is no lightning arrester, for example, if tower 1 is struck by lightning, the ground potential of the entire tower will rise due to the product of the lightning current and the ground resistance of the tower's pedestal. If the difference between the electric potential of the power transmission line and the ground potential is large, a flash fault occurs between the arc horns 5a and 5b, and a one-wire ground fault current flows to the power transmission line 4, and this ground fault current is interrupted by the circuit breaker at the transmission end substation. The operation of power transmission line $4 will stop, causing a power supply failure. This also applies when the power transmission line 4 is struck by lightning and a flash short circuit occurs between the arc horns 5a*5b. However, as shown in Fig. 3, the aerial gear bu
, in series, or in which the air gap is omitted as shown in Figure 4, no discharge occurs between the arcing horns, and the lightning current flows through the lightning arrester element 6. The alternating current at the operating frequency that flows from the transmission line following the current, so-called follow-on current, is interrupted within 0.5 to 1.0 cycles due to the non-linear characteristics of the resistance element mainly composed of zinc oxide, so it is difficult to transform. The circuit breakers at the substation do not operate (the circuit breakers at the substation have relays set so that they do not operate unless the current continues for about 5 + cycles), so there is no power supply failure and a stable power supply. can be realized.

@Figure 5 is a longitudinal sectional view showing the structure of the lightning protection element 6 shown in Figures 3 and 4. A resistance element 8 whose main component is zinc oxide is housed in an insulating cylinder 9, and a compressor is inserted between the upper 7 flange LOa which is screwed into the insulating cylinder 9 airtightly and the upper end surface of the fine layer of the resistance element. The resistive element is firmly held between the upper flange 10a and the lower 7 flange 10b via the spring 11. In the figure, reference numeral 12 is cast molded so as to tightly surround the outer peripheral surface of the insulating cylinder 9. It is an insulator made of an organic insulating material with flexibility similar to rubber. A plurality of pressure relief holes 13 are provided in the insulating tube 9 to prevent the lightning protection element from exploding and scattering in the event that the resistor element 8 is destroyed.

As explained above, the conventional lightning arrester has as its constituent element a lightning arrester element that performs follow-on current interruption using a resistance element containing zinc oxide as a main component.

[Problem to be solved by the invention]

As described above, the problems with the lightning arrester for a power transmission line whose component is a lightning arrester element that performs follow-on current interruption using a resistance element whose main component is zinc oxide are as follows. In other words, according to the results of systematic lightning observation conducted by research institutions, the lightning current that occurs in the summer reaches a magnitude of several hundred kA, but the duration is several tens of microseconds, so the amount of charge passing through it is several tens of kiloamps. The resistance is on the order of coulombs, and even conventional resistance elements mainly made of zinc oxide can withstand this. However, the lightning currents that occur in winter on the Sea of Japan side reach several hundred kA in size, have a long duration of several 613 seconds, and have been observed to have a passing charge of several hundred coulombs. In some cases, the amount of zero-pass charge is about 1000 times that of summer lightning, so the so-called absorbable energy is limited to a few tens of coulombs.Resistance elements mainly made of lead oxide are suitable for lightning arresters that can be used on power transmission lines on the Sea of Japan side. is in a state where it is not possible to configure the
Power supply failures still occur frequently.

The object of the present invention is to provide a power transmission line that has a high resistance to lightning current heat and can pass several hundred coulombs of charge 1 without being destroyed, and can cut off follow-on current in 0.5 to 1.0 cycles. 711N device configuration.

[Means to solve the problem]

In order to solve the above-mentioned problem, according to the present invention, it is installed on the ground. It is installed between the above-mentioned above-mentioned above-mentioned above-mentioned above-mentioned tower and an overhead power transmission line that is suspended from the above-mentioned above-mentioned above-mentioned power transmission line which is suspended from the above-mentioned above-mentioned power transmission line through an insulator at a high position above the ground and runs almost parallel to the above-mentioned ground from the above-mentioned above-mentioned power transmission line which is at ground potential. A lightning arrester for a power transmission line is configured to allow a lightning strike current to pass therethrough and, following the passage of the lightning strike current, interrupt a current at an operating frequency flowing from the overhead power transmission line to prevent a lightning strike accident in the power transmission system. A vacuum gap device provided with a discharge gap in a vacuum container is provided as a series component through which the lightning current passes.

[Effect]

The present invention focuses on the point that the various performances required of such a lightning arrester for power transmission lines can be most appropriately achieved by a vacuum gap device. As is well known, the degree of vacuum is 10-10-
A discharge gap in a high vacuum of 3ffi or more has an extremely high constant discharge pressure regardless of the pressure. For example, when a uniform electric field with a gap length of 1 ml is formed using @ and others,
It shows a discharge voltage of 7kV.

Therefore, it is required when the transmission 'wL voltage is between 66 kV and 154 kV. For a discharge voltage of about 270 kV to 630 kV or less, it is possible to cope with this with a gap length of about 20 m or less, assuming that a quasi-equal electric field is formed between the gap electrodes. In addition, since the lightning current during discharge, which is the main object of the present invention, is a discharge current in a vacuum, it is theoretically not subject to any size restrictions.Moreover, such a large current has the effect of shrinking the diameter due to its own pinch effect. Therefore, a lightning strike current with a large peak value and a long duration can easily pass through a vacuum vessel of a practical size with a relatively small diameter. Furthermore, the AC current interrupting ability is
Since the insulation recovery after passing the current zero point in vacuum is extremely fast, even the simplest gap structure can generate several thousand amperes, and if the electrode structure magnetically drives the arc between the gaps, even larger currents can be generated. Blocking is possible. Since the single-wire ground fault current in a power transmission system with a transmission voltage of 66 kV to 154 kV is several hundred amperes or less, it can be interrupted by a gap electrode with a simple structure. Therefore, by using a discharge gap device with a long external insulation distance but a relatively small diameter as a series component of a lightning arrester, it becomes possible to provide an economical and lightweight lightning arrester for a power transmission line with a large amount of charge that can pass through. Note: ■ The vacuum gap device configured in this way is connected to the air gap G as shown in Fig. 3.
1, if a capacitor with a capacitance of several tens of pF or more is connected in parallel to the vacuum gap device, almost all of the voltage applied between the power transmission line 4 and the tower 1 can be removed. Since it depends on the air gap G1, the gap length of the air gap G can be set independently of the vacuum gap device, which is convenient in practice when configuring a lightning arrester whose components are manufactured by different manufacturers. can get. Also, send 'Z
If a lightning strike to a line crosses two or three wires of the transmission line, the magnitude of the follow-on current will be the magnitude of the short circuit current, and the insulation recovery of the vacuum gap will be small.
If a shock is expected, a gap electrode is built-in.゛By combining short vacuum gap devices in multiple stages and connecting capacitors with the same capacitance in parallel to each vacuum gap device to equalize the voltage shared by each vacuum gap, it is possible to eliminate multiple lines in winter. It becomes possible to create a lightning arrester that can withstand lightning strikes. In addition, when this multi-stage vacuum gap device is used in series with the air gap Gl as shown in Fig. 3, the series capacitance of the capacitor connected in parallel to each unit vacuum gap device is as described above. It plays the same role as the parallel capacitor in the single-type odor-air gap device, and does not require any new additional capacitor.

〔Example〕

FIG. 1 shows a first embodiment of a vacuum gap device according to the present invention. An upper electrode 18 and a lower electrode 19 are disposed facing each other in the axial direction by passing through an upper flange 17a and a lower flange 17b, respectively, which hermetically seal both end surfaces of the insulating container 16.

Each of these electrodes is surrounded by a cylindrical metal shield n having the same potential as the same-shaped seven flange 17a at the tip of a metal round bar, to prevent disturbance of the electric field between the electrodes due to the external conductor. The numeral ``addition'' indicates a bellows, which is used when adjusting the discharge gap length by factory testing. After the adjustment is completed, the lower electrode 19 is fixed to the lower 7 flange 17a. Note that reference numerals 21, 23, and 24 in the figure indicate a sealing section for sealing off the inside of the insulating container 16 to a vacuum, a terminal formed on the upper electrode 18, and a terminal formed on the lower electrode 19, respectively.

Upper flange 27Jl that airtightly seals both end surfaces of 4.

An upper electrode portion and a lower electrode device are fixed to each of the lower 7 flange 27b so that the gap length between the disc-shaped electrode surfaces facing each other in the axial direction is within a predetermined dimensional difference, and an insulating container is further provided with an upper electrode portion and a lower electrode device. A capacitor I having the same capacitance is connected between the upper flange 27a and the lower 7 flange 2'7b on the outside. Each unit vacuum gap device formed in this way is fixed to the upper and lower flanges using metal fittings 31 and 32.
are connected in multiple stages (two stages in this example) in the axial direction using A rod electrode that constitutes the electrode is fixedly installed. In this case, the parallel capacitor addition of the unit vacuum gap device forms a parallel capacitor of the entire multi-stage vacuum gap device in the series direction.

〔Effect of the invention〕

As described above, according to the present invention, a lightning arrester for a power transmission line is constructed by configuring a vacuum gap device having a discharge gap in a vacuum container as a series component through which lightning current passes, so that the following effects can be achieved. be.

+11 It is said to be winter lightning that occurs on the Sea of Japan side. A power transmission line that can reliably pass a lightning strike current with a discharge charge of several hundred coulombs in a practical size, and that can cut off the operating frequency current that flows from the transmission line within one cycle after this passage. It is now possible to provide an evacuation N device.

It is essential for lightning arresters installed on transmission line towers to be lightweight, but vacuum gap devices installed on the tower side only have a small number of parts because they only allow discharge between the gap electrodes. Moreover, since the inside of the insulating container is a vacuum, this requirement can be easily satisfied.

(3) For the reason stated in item 2 above, it is possible to economically construct a lightning arrester for a power transmission line.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view showing a first embodiment of a vacuum gap device structure constituting a lightning arrester for power transmission lines according to the present invention;
The figure is a partial vertical cross-sectional view showing the second embodiment, FIGS. 3 and 4 are explanatory diagrams showing different configurations of conventional lightning arresters for power transmission lines, and FIG. It is a longitudinal cross-sectional view which shows the structural example of the lightning protection element shown in FIG. 1... Steel tower, 3... Power transmission line (overhead power transmission line), 6...
・Lightning protection element, 16.26...Insulating container, 18.28・
...Top electrode, 19, 29...Bottom electrode, δ, 35
···vacuum. Figure 1 Figure 3

Claims (1)

[Claims] 1) The above-mentioned overhead power transmission line is installed between the above-mentioned steel tower and an overhead power transmission line that is suspended from a steel tower at ground potential and is suspended at a high position above the ground via an insulator and runs approximately parallel to the ground plane. Or, in a lightning arrester for a power transmission line, which reacts to a lightning strike on a steel tower and allows the lightning current to pass through, and following this passage, interrupts the current at the operating frequency flowing from the overhead power transmission line to prevent a lightning strike accident in the power transmission system. A lightning arrester for a power transmission line, characterized in that the lightning arrester for a power transmission line has a vacuum gap device provided with a discharge gap in a vacuum container as a series component through which the lightning current passes.