JPS6040681B2 - Fluid-insulated lightning arrester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a lightning arrester used for absorbing surges in a power system, and particularly to a fluid-insulated type lightning arrester.

Lightning surges and switching surges that occur in power systems can threaten the electrical insulation strength of the power system, and in order to suppress and absorb these surges that occur in power systems, various current-reducing devices have been put into practical use. The area around the area is mirror-like, where fluid-insulated type counterfeits using SF6, insulating oil, etc. are often used.

The advantage of using a fluid-insulated type of protection equipment is that, like other high-voltage equipment, the separation distance required for insulation is reduced by 4 mm.
The aim is to make the direct bag smaller and more reliable. In addition, over the past few years, metal oxide nonlinear resistors such as zinc oxide, which have significantly large tortoise force nonlinearity, have been developed, and the series gap, which was indispensable for conventional earth protection equipment, has also been developed. A gapless resistor, which does not require a gapless resistor, has been developed which uses only a non-linear resistor as an internal element. Two recent developments in current resistors have led to the development of fluid-insulated gapless resistors. A typical example of such a fluid-insulated gapless lightning selector is shown in FIG. That is, a cylindrical metal container 2 coaxially surrounds a cylindrical non-linear resistance assembly 1.
, an insulating spacer 3 that holds the high voltage side of a non-linear resistance assembly, and a high-pressure insulating fluid 4, such as SF6, is sealed in a cylindrical metal container 2 kept airtight. However, the biggest problem with such fluid-insulated gapless earth arresters is that the alternating current voltage of the power system that is constantly applied to the earth arrester causes non-uniformity to occur along the lines of electric force 5 shown by the dotted lines in Figure 2. Since a displacement current flows between the linear resistance assembly 1 and the cylindrical metal container 2, the higher the voltage side of the nonlinear resistance assembly 1, the more leakage current always flows, and the higher the voltage side of the nonlinear resistance assembly 1, the lower the voltage. It deteriorates faster than the sides.

Therefore, it is necessary to provide a margin in the overall life design so that even the high voltage side of the nonlinear resistance assembly 1, which deteriorates the fastest, will operate normally for a certain period of time, and to provide an electrostatic shield on the high voltage side of the nonlinear resistance assembly 1. Measures are taken to reduce the displacement flow by installing a
However, the power transmission main lines of power systems require a particularly high degree of reliability over a long period of several decades, so in addition to the measures mentioned above, it is also necessary to detect and determine deterioration of earth arresters through periodic inspections. Particularly in gapless lightning arresters, a constant increase in leakage current causes thermal runaway of the nonlinear resistor assembly 1, so a method must be adopted that detects and determines the deterioration of the lightning arrester based on the degree of increase in constant leakage current. From the above, it can be understood that in order to detect and judge the deterioration of a fluid-insulated gapless resistor, it is necessary to constantly measure the leakage current on the high voltage side of the non-contact wire resistance assembly 1, which deteriorates the fastest. The method of constantly measuring the leakage current at the arrester grounding terminal 7 shown in Figure 2 ignores the displacement current flowing between the nonlinear resistance assembly 1 and the cylindrical metal container 2, so it is the quickest method. There is a drawback that the deterioration on the high voltage side of the deteriorating nonlinear resistance assembly 1 cannot be directly measured.

Since the leakage current of the nonlinear resistance assembly 1 for gapless earth arrester is always on the order of A, it is significantly smaller than the mA order of the displacement current flowing between the nonlinear resistance assembly 1 and the cylindrical metal container 2. Even if the high voltage side portion of 1 deteriorates and the leakage current in that portion constantly increases, there is almost no change in the leakage current measured at the earth arrester grounding terminal 7, and no deterioration is detected at all. The present invention has been made in order to overcome the drawbacks of the above-mentioned conventional methods regarding constant leakage current measurement for determining the inferiority of fluid-insulated earth arresters, particularly fluid-insulated gapless earth arresters. To accurately detect and judge the deterioration of a lightning arrester by directly measuring the leakage current of the high voltage side part of the nonlinear resistor assembly 1, which deteriorates the fastest, while the earth arrester is still installed in the power system. This was done with the aim of obtaining a fluid-insulated electrical protection device layer.

A first embodiment of the invention is shown in FIG. The metal foil 6 is attached to the inner wall of the cylindrical metal container 2 while being electrically insulated from the cylindrical metal container 2. However, as shown in the cross-sectional view of FIG. 4, the rise of the metal foil 6 is caused by lines of electric force directed from the top end of the high voltage part of the nonlinear resistance assembly 1 mainly composed of metal oxide toward the cylindrical metal container 2. It is also pasted on the bottom of the cylindrical metal container 2, and these are electrically connected to the lightning arrester grounding terminal 7 at the lower end of the non-linear resistance assembly 1. In short, the metal foil 6 receives all the electric lines of force 5 directed from the non-linear resistance assembly 1 toward the cylindrical metal container 2, and all of the displacement current flowing between the non-linear resistance assembly 1 and the cylindrical metal container 2 is grounded to the lightning arrester. Create a structure where it flows into terminal 7. With the above structure, as shown in FIG. The current flowing into the space surrounded by is only the current from the high voltage side of the non-linear resistance assembly 1, and the current flowing out from this space is only the current from the earth resistor grounding terminal 7, and according to Kirchhoff's law, These two currents become equal.

Thus, as described above, a metal foil is attached so as to be electrically insulated from the inner wall of the cylindrical metal container 2 so as to receive all the electric lines of force 5 directed from the nonlinear resistance assembly 1 toward the cylindrical metal container 2. In a fluid-insulated gapless earth arrester having a structure in which the metal foil 6 is electrically connected to the earth resistor grounding terminal 7, the current flowing through the earth arrester earthing terminal 7 is the high voltage of the non-linear resistance assembly 1 which deteriorates the fastest. Since it is directly equal to the leakage current that always flows to the side, by measuring this, it is possible to most accurately detect and judge the deterioration of the earth protector. A cross-sectional view of a second embodiment of the invention is shown in FIG.

In this embodiment, the electrostatic shield 8 is used to reduce the displacement current flowing between the non-linear resistance assembly 1 and the cylindrical metal container 2. In this case, the largest amount of leakage current flows constantly, causing rapid deterioration. is the part of the non-linear resistance assembly 1 directly below the electrostatic shield 8. Therefore, as shown in FIG. 5, the metal foil 6 is placed on the cylindrical metal container 2 so as to receive all the electric lines of force 5 directed from the non-linear resistance assembly 1 on the low voltage side toward the cylindrical metal container 2 from directly below the electrostatic shield 8. If the metal foil 6 is electrically insulated and attached to the inner wall of the shield, the metal foil 6 is electrically connected to the earth arrester ground terminal 7, and the current of the earth arrester earth terminal 7 is measured, the electrostatic shield 8 which deteriorates the fastest can be found. It is possible to constantly know the leakage current in the portion of the non-linear resistance assembly 1 directly under the non-linear resistor assembly 1, and deterioration can be detected and determined. A third embodiment of the invention is shown in FIG.

This is different from the first embodiment described above, in that the metal foil electrically insulated and pasted on the inner wall of the cylindrical metal container 2 is a strip of metal foil 9 parallel to the non-linear resistance assembly 1. This strip-shaped metal foil 9 is used when the fluid-insulated gapless earth arrester is almost completely coaxially symmetrical. Although the strip metal foil 9 cannot receive all the electric lines of force directed from the non-linear resistance assembly 1 to the cylindrical metal container 2, since the freeloader is almost completely coaxially symmetrical, as shown in FIG. The angle at which the strip metal foil 9 looks at the central axis of the nonlinear resistance assembly 1 is 0 (
degree), the current of the earth arrester grounding terminal 7 and the current of the strip-shaped metal foil 9 are calculated as 1 pair 360/8 by the calculation intensifier 11.
If the current is measured by analog addition at a ratio of As in the example, the leakage current of the high voltage side portion of the nonlinear resistance assembly 1 can be measured at all times. This method using the strip-shaped metal foil 9 requires only a small area for pasting the metal foil, and is industrially advantageous. In addition, a non-linear resistance assembly 1 like the deformed strip metal foil 10 in FIG.
If the inside of the strip-shaped metal foil is changed along the direction of It is possible to determine the weighted average of the leakage current constantly flowing through each part of the body 1 according to the change in the strip-shaped metal foil 9, and it is also possible to know the average deterioration of the non-linear resistance assembly 1. A fourth embodiment of the invention is shown in FIG.

This is a method of attaching a group of rectangular metal foil pieces 12 with an appropriate area to the inner wall of a cylindrical metal container 2 along the non-linear resistance assembly 1 in an electrically insulated manner, similar to the third embodiment. Current and earth arrestor grounding terminals 7 of these rectangular metal foil pieces group 12
The currents are multiplied by an appropriately selected proportionality constant using an arithmetic intensifier 11, and then added. By appropriately selecting this proportional constant, the leakage current at any position of the nonlinear resistance assembly 1 and an arbitrary weighted average of the leakage current can be obtained, and information regarding the deterioration of any part of the nonlinear resistance assembly 1 can be obtained. can be obtained. As explained in the above four embodiments, the effect of the present invention is to easily reduce the leakage current flowing through the high voltage side portion of the non-linear resistance assembly of the fluid-insulated gapless surge arrester, which has been considered difficult compared to the conventional type. The reason is that it can be measured while it is installed in the power system.

This method allows for accurate inspection and evaluation of the deterioration of the earth arrester by directly measuring the leakage current flowing to the high voltage side of the non-linear resistance assembly, which deteriorates the fastest, and can be used for judgment and implementation of the electric arrest test of fluid-insulated gapless arresters. This greatly contributes to reducing deterioration accidents in the field. The present invention has been explained using a fluid-insulated gapless armature device as an example because its effect is most remarkable, but the present invention can also be used to measure the leakage current on the high voltage side of a conventionally used fluid-insulated gapless arrester. can be adopted.

Furthermore, it is clear that the method of the invention can be used to measure the current on the high voltage side of a high impedance element in which the displacement current between the metal container and the grounded metal container cannot be ignored. In short, all the electric lines of force from the high-impedance element toward the metal container are received by the metal foil, and the combined value of the current in the metal foil and the current on the ground side of the high-impedance element gives the current on the high-voltage side of the high-impedance element. be. Furthermore, the principle of measuring the displacement current flowing between the nonlinear resistance assembly 1 and the cylindrical metal container 2 explained in the first to fourth embodiments is based on the type of insulating fluid 4 filled in the cylindrical metal container 2. S is not affected by the insulating fluid.
An insulating gas such as F6, dry air, nitrogen or an insulating liquid such as electrical insulating oil can be used.

[Brief explanation of drawings]

Figure 1 is a diagram of a typical fluid-insulated gapless crab avoider.
Figure 2 is a cross-sectional view of a typical fluid-insulated gapless earth arrester, Figure 3 is a diagram of a fluid-insulated gapless earth arrester using the metal foil of the present invention, and Figure 4 is a cross-sectional view of a typical fluid-insulated gapless earth arrester using the metal foil of the present invention. FIG. 5 is a sectional view of a fluid-insulated gapless arrester with static crab shield using the metal foil of the present invention, and FIG. 6 is a cross-sectional view of a fluid-insulated gapless arrester using the metal foil of the present invention. A diagram of a fluid-insulated gapless lightning selector using foil, Figure 7 is an explanatory diagram of measurement of leakage current on the high voltage side of a non-linear resistor assembly using the strip metal foil of the present invention, and Figure 8 is a diagram of the present invention. A diagram of a fluid-insulated gap type earth arrester using the rectangular metal foil group of the present invention, and FIG. 9 is an explanatory diagram of measurement of leakage current in an arbitrary part of a nonlinear resistance assembly using the rectangular metal foil group of the present invention. It is. 1...Non-linear resistance assembly, 2...Cylindrical metal container, 3...Insulating spacer, 4...
...Insulating fluid, 5... Lines of electric force, 6... Metal foil,
7...Grounding terminal. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9

Claims (1)

[Scope of Claims] 1. In a fluid-insulated lightning arrester in which an internal element of a lightning arrester housed in a metal container is insulated with an insulating fluid, the lightning arrester is configured to receive electric lines of force from the internal element of the arrester toward the metal container, and A fluid insulation device in which a metal foil is attached to the metal container while being electrically insulated from the container, the current flowing through the metal foil is extracted to the outside of the metal container, and leakage current of an internal element of the lightning arrester is detected based on the value of the current. type lightning arrester. 2. The fluid-insulated lightning arrester according to claim 1, wherein the internal element of the lightning arrester does not include a series discharge gap and is an internal element for a so-called gear press arrester. 3. The fluid-insulated lightning arrester according to claim 1, wherein the metal foil is electrically connected to the ground terminal on the low voltage side of the internal element of the lightning arrester, and leakage current is detected via this ground terminal. 4. The fluid-insulated type according to claim 1, wherein the metal foil is a strip-shaped metal foil having a constant width along the internal element of the arrester, and a terminal is drawn out from the strip-shaped metal foil separately from the arrester grounding terminal. Lightning arrester. 5. A deformed strip metal foil in which the width of the strip metal foil changes along the internal elements of the arrester, and a terminal is drawn out from the deformed strip metal foil separately from the arrester grounding terminal. Fluid-insulated lightning arrester. 6 The metal foil is a group of rectangular metal foils, and the rectangular metal foil group is attached to the inner wall of the metal container along the internal elements of the lightning arrester in an electrically insulated manner with respect to the metal container. 2. The fluid-insulated lightning arrester according to claim 1, wherein a terminal group is drawn out separately from the lightning arrester grounding terminal. 7. The fluid-insulated lightning arrester according to claim 1, which is fluid force SF_6, dry air, an insulating gas such as nitrogen, or an insulating liquid such as electrical insulating oil.