JPH0360161B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a neutral point grounding resistance device for grounding the neutral point of a transformer winding via a resistance device.
The purpose of this is to reduce the size of the equipment itself, reduce the installation area of the equipment, improve maintenance safety, and improve maintenance safety.
The aim is also to improve installation workability.

In general, in long-distance power transmission systems and cable power transmission systems, neutral points are grounded to compensate for ground charging capacity, to suppress abnormal voltage in the event of a single line ground fault, to detect elements of a ground fault relay, or to prevent inductive disturbances to communication lines. method is widely adopted, and for this reason, e.g.
As shown in the figure, a neutral point grounding resistance device 1 (hereinafter simply referred to as a resistance device) is connected to a neutral point grounding device 2 of a transformer 2 in a substation that serves as a relay point in the power transmission system.
It is connected to a. Further, a protective fence 3 is provided around the resistance device 1 to ensure safety. Then, the resistance device 1 is arranged in a case 1a.
It consists of a plurality of resistors 4 formed by arranging resistor elements a in a grid pattern, and a required number of resistors 4 are installed within the protective fence 3 via insulators 5. However, since the resistance device 1 generally employs an air insulation method, it is relatively large, and its installation is as shown in FIG.
Since they are installed in a single horizontal row, they require a considerable amount of installation space. On the other hand, in recent years, substation equipment has been made smaller and lighter by using SF 6 gas (hereinafter simply referred to as SF ₆ gas) as an insulating material, as seen in gas-insulated equipment, and the resistance devices mentioned above have become smaller and lighter. 1 is also gradually being developed using SF ₆ gas insulation technology. For example, as shown in FIG. 2, the resistor element a is housed in a closed container 6 filled with SF ₆ gas G, or as shown in FIG. For example, a resistor element a provided with an insulating spacer 7 made of a porcelain heat storage material mixed with alumina powder or the like is housed in a closed container 6 filled with SF ₆ gas G. There is. However, in the former case, when a current is supplied to the resistor element a, the heat corresponding to the resistance of the resistor 4 itself is dissipated as it is, so
The resistor element a and the sealed container 6 must have excellent heat resistance, and on the other hand, if the temperature of the resistor 4 itself increases,
Since the SF ₆ gas G is decomposed to generate decomposed gas such as hydrogen fluoride gas, and the decomposed gas is accumulated in the closed container 6, it has been difficult to raise the temperature of the resistor element. To overcome this drawback, the resistor 4 itself can be made larger to increase its current carrying capacity, but this increases the size of the resistor device 1 and is uneconomical. In addition, in the latter case, the heat generated from the resistor element a can be stored by the insulating spacer 7 interposed between the resistor elements a, so that the resistor 4 itself can be miniaturized and the resistor device 1 can be downsized. On the other hand, due to the heat stored in the insulating spacer 7,
A decomposed gas of SF ₆ gas is generated, and the decomposed gas adheres to the resistor element a and the insulating spacer 7, causing deterioration and damage to the insulating spacer 7 and the like, which may shorten the life of the resistor device 1.

The present invention eliminates the above-mentioned drawbacks and fills the sealed case housing the resistor with a heat insulating material with heat storage and heat insulation functions instead of SF ₆ gas. The purpose of the present invention is to provide a compact and high-performance neutral point grounding resistor device that prevents the generation of decomposed gas inside the case that deteriorates and damages the components of the resistor device due to heat. To explain with reference to FIGS. 4 to 6, 11
Reference numeral 12 indicates a shield case for storing a resistor, which is made into a rectangular box shape by press-forming or welding a metal plate, and 12 indicates a resistor which is housed and held in a grid shape within the shield case 11, and is made of a heat-resistant metal. The element body 12a (for example, a plate made of ferritic special steel) is arranged in a grid shape and the connection points are welded or bent into a grid shape, depending on the required resistance value. It is constructed by stacking and connecting in multiple stages. 12b is the resistor element 12
The connection part a, 13, is a terminal connected to both ends of the resistor 12, and the resistor 12 is housed in a grid shape as shown in FIG. 6 in the shield case 11 with the lid (not shown) removed. Then, the terminals 13 are respectively connected to connection terminals (not shown) of an insulator 14 attached to the side wall of the shield case 11. After that, a heat insulating material 15 made of non-woven fabric with excellent heat resistance such as rock wool or glass wool is stuffed into the shield case 11 to the extent that there are no gaps, and a lid body (not shown) is hermetically welded to the case 11 to form a resistor 16. Configure. 17 is the resistor 16
A tank that stores the required number of stacks of
As shown in FIG. 5, each of the resistors 16 is housed in a tank 17 via an insulator 18, stacked and fixed at a required interval.

In addition, the shield case 11 housing the resistor 12
The upper and lower parts tend to have sharp protrusions due to their manufacturing.As a result, when a lightning surge is applied to the resistor 12, the electric field is concentrated and strengthened at the sharp protrusions of the shield case 11, and the resistor 16, an uneven electric field is generated and a strong electric field is generated, so a shield ring 19 is provided on the top and bottom of the shield case 11 by welding a ready-made pipe to hide the sharp protrusion. Therefore, the uneven electric field due to the sharp protrusion is compensated for and the electric field distribution is relaxed. Further, each resistor 16 housed in the tank 17 is connected to a connecting conductor 2.
Furthermore, the resistor 16 at the top of the tank 17 is connected to the terminal of an insulator 17a provided on the top of the tank 17 via a connecting conductor 20a, and the resistor 16 at the bottom is connected to the side wall of the tank 17. It is connected via a connecting conductor 20b to a terminal of an insulator 17b protruding from the lower part. Then, in the tank 17 mentioned above,
A neutral point grounding resistance device 21 is constructed by filling SF ₆ gas G at a required pressure. As shown in FIG. 4, this resistance device 21 is installed at a required location within the substation, and is connected to the neutral point bushing 22a of the transformer 22 via a cable 23 to the insulator 17.
The terminal of the insulator 17b is connected to the terminal a, and the terminal of the insulator 17b is grounded to the earth via the ground wire 24.

Next, to explain the operation, now the transformer 22
When a current is supplied from the terminal 13 to the resistor 16 from the neutral point bushing 22a of the cable 23 through the connecting conductor 20a, the resistor 12 of each resistor 16 generates heat corresponding to its resistance. This resistor 12
The high heat generated in Heat is dissipated from the outer surface of the gas into the tank 17 at a temperature that does not decompose the SF ₆ gas G. Furthermore, since most of the heat from the resistor 12 is stored in the heat insulating material 15 packed inside the shield case 11, the internal pressure inside the shield case 11 does not increase due to the temperature rise of the resistor 12. . Regarding this point, the test results were conducted using reduced models of the resistor 16 of the present invention in which a heat insulating material 15 was packed inside the shield case 11 and a resistor without any heat insulating material packed in the shield case 11. This will be explained based on the resistor temperature-internal pressure characteristic table shown in FIG. The test was conducted by continuously applying a current of 3000 A to each resistor for 20 seconds once.

As can be seen from the table in FIG. 9, when only the resistor is placed in the container, the temperature θ (indicated by the dashed-dotted line) of the resistor rapidly decreases over time after energization ends. However, the internal pressure P (indicated by the two-dot chain line) increases to the highest level immediately after the end of energization, and thereafter decreases as time passes. This is because the container is sealed, and the air inside the container expands rapidly as the temperature of the resistor increases.

On the other hand, in the resistor 16 of the present invention, since the resistor 12 is surrounded by the heat insulating material 15, the temperature θ ₁ (indicated by the solid line) of the resistor 12 once heated is , its drop is significantly inferior compared to one without surrounding insulation. This is because the area around the resistor 12 becomes high temperature, but most of this heat is stored in the heat insulating material 15, so the temperature inevitably decreases as the distance from the resistor 12 increases. Therefore, once the temperature of the resistor 12 rises, it does not drop suddenly. Furthermore, as described above, the internal pressure P ₁ (indicated by the dotted line) becomes high temperature around the resistor 12, but the temperature does not rise much at a point far from the resistor 12.
Although the overall temperature inside the container 11 increases locally, it does not increase overall, and as a result, the pressure inside the container 11 reaches the 9th level.
As shown by the dotted line in the figure, there is almost no rise. Furthermore, since there is almost no temperature rise as the distance from the resistor 16 increases, the shield case 11
Since the surrounding area is almost the same as when the resistor 12 is not energized, SF ₆ is not decomposed by the heat generated by the resistor 12. Therefore, the shield case 11 and the tank 17 do not need to be made strong because there is almost no internal pressure or generation of decomposed gas.

Moreover, each resistor 1 housed and installed in the tank 17
6, the resistor 12 is surrounded by the shield case 11, and since the shield ring 19 is provided around the sharp protrusion of the shield case 11, the uneven electric field caused by the sharp protrusion is compensated for. Since the electric field distribution in this area can be relaxed by the shield ring 19, the corona generated by the concentration of the electric field can cause the tank 1 to
The SF ₆ gas G in 7 is not degraded or contaminated at all, and therefore the insulation strength can be improved when a lightning surge enters.

In addition, FIG. 7 shows another embodiment of the resistor 16, and its structure is such that a heat-resistant tape-shaped heat insulating material 15 such as glass wool is placed around a resistor element 12a arranged in a grid pattern. After winding multiple layers of ′,
A resistor 1 wrapped with this tape-shaped heat insulating material 15'
2 is housed in a shield case 11, and in the space inside this case 11, for example, an inorganic ceramic fiber (generally made of silica or alumina is used) which has relatively low fluidity, high viscosity, and excellent heat resistance Amorphous silica-alumina short fibers having a composition of 1:1 and produced by the melt fiberization method are called ceramic fibers, and when used, they are kneaded with water and cured by hydration at room temperature. For example, product name
IsoTap, manufactured by Isolite Kogyo Co., Ltd., corresponds to this. ) is filled and solidified,
A heat insulating layer 15a is provided in the case 11 with the resistor 12 buried therein to constitute a resistor 16, and the resistor 1
Even if 2 thermally expands due to energization, the thermal expansion is absorbed by the heat insulating material 15' wound around the resistor 12 to prevent cracks from occurring in the heat insulating layer 15a. A function similar to that of a resistor 16 packed with resistors 15 can be obtained, or as shown in FIG. For example, after filling a filler made of inorganic ceramic fiber with high viscosity and excellent heat resistance, the resistor 12 is energized for a required period of time, and the heat of the resistor 12 causes the filler in the shield case 11 to melt. By heating and solidifying, a heat insulating layer 15b in which the resistor 12 is buried is formed, and a layer corresponding to the thermal expansion of the resistor 12 itself that occurs when the resistor 12 is energized is formed between the heat insulating layer 15b and the resistor 12. (This gap S is created when the expanded resistor 12 contracts.) Even if the resistor 12 expands due to energization, the range will be within the space of the gap S. The present invention can also be achieved even if the resistor 16 is constructed in such a way that no load is placed on the heat insulating layer 15b.

Then, each resistor 16 shown in FIGS. 7 and 8
Needless to say, these are used by being stacked in a tank 17 filled with SF ₆ gas G, as shown in FIG.

As described above, the present invention includes filling a heat-resistant heat insulating material in the shield case housing the resistor, or
Alternatively, a resistor is constructed by filling and solidifying a filler made of inorganic ceramic fiber with high viscosity and excellent heat resistance, and providing a heat insulating layer in which the resistor is buried. A neutral point grounding resistance device is manufactured by attaching pipe-shaped shield rings and stacking them in multiple stages in a tank filled with SF ₆ gas. The resistor is constructed by filling the shield case with a heat-resistant heat insulating material or forming a solid heat insulating layer made of inorganic ceramic fiber, and then airtightly sealing the case, so that current is supplied to the resistor. When the resistor generates heat, the area around the resistor becomes high temperature, but most of the heat is stored in the insulation material or layer.
At a position far away from the resistor, almost no heat is transferred from the resistor, i.e., the overall temperature of the _resistor itself does not increase substantially. The SF ₆ gas is thermally decomposed by the heat from the shield, which increases the internal pressure of the shield case housing the resistor, and the decomposed gas never deteriorates the resistor parts. Even if the case itself has a sealed structure, almost no internal pressure is generated, so there is no danger at all, and the resistor can be used smoothly for a long period of time. Furthermore, the present invention has a structure in which the heat from the resistor is temporarily stored using a heat insulating material, etc., so that the temperature around the container housing the resistor does not increase. It becomes possible to reduce the distance between the resistors, which in turn allows the resistor to be made smaller. Moreover, the miniaturized resistors can be stacked in tiers with narrower spacing in a tank filled with SF ₆ gas (the spacing between each resistor can be adjusted by filling SF ₆ gas). (The insulation distance can be made shorter than that in the air.) Therefore, the neutral point grounding resistance device of the present invention
It has the advantage that it can be significantly smaller than conventional resistor devices, and as a result, the installation area within a substation can be reduced. Furthermore, each resistor installed in stages inside the tank is equipped with a shielding device, so the electric field can be relaxed, and the temperature of the shield case itself does not rise even though the resistor generates heat. In addition to this, the SF ₆ gas inside the tank is not affected by heat at all, so its insulating performance can remain stable for a long time. Moreover, the resistor is used for a short time (several seconds)
Moreover, since there is an interval before the next use, there is no need to rapidly cool down the heat insulating material that stores the heat of the resistor, and the heat is gradually transferred to the shield case via the heat insulating material, etc. Since it is only necessary to dissipate heat, there is no need to consider the mechanical strength or heat resistance of the shield case itself, so the design and manufacturing of the case that houses the resistor can be done easily and economically. Moreover, since the resistor is housed in a tank filled with SF ₆ gas, it can be installed safely and economically without requiring a protective fence at the installation site. It has many excellent features such as.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing the installation state of a conventional neutral point grounding resistance device, Figs. 2 and 3 are longitudinal cross-sectional views of a conventional resistor, and Fig. 4 is a neutral point grounding resistance device of the present invention. 5 is a schematic diagram showing the installation state of the device of the present invention, FIG. 6 is a cross-sectional plan view of a resistor constituting the device of the present invention, and FIGS. 7 and 8 are views of other resistors. FIG. 9, a cross-sectional plan view showing the embodiment, is an explanatory diagram for explaining the thermal characteristics and internal pressure characteristics of the resistor. 11... Container, 12... Resistor, 15... Heat insulating material, 16... Resistor, 17... Tank, 21...
Neutral point earthing resistance device.

Claims (1)

[Scope of Claims] 1. A resistor is constructed by filling a heat-resistant heat insulating material in a case in which a resistor is disposed and airtightly sealing the case, and filling the resistor with sulfur hexafluoride gas. 1. A neutral point grounding resistance device, characterized in that the neutral point grounding resistance device is housed in a layered tank. 2. A resistor with a heat insulating material wound around it is housed in a case housing the resistor, and an inorganic filler with excellent heat resistance is filled and solidified in the case to form a heat insulating layer, and inside this heat insulating layer, A resistor is constructed by airtightly sealing the case with a resistor embedded in it, and the resistor is housed in a tank filled with sulfur hexafluoride gas by stacking and fixing it in layers. Features: Neutral point grounding resistance device. 3 The case in which the resistor is placed is filled with an inorganic filler with excellent heat resistance so that the resistor is buried, and this filler is heated and solidified by the heat generated when the resistor is energized. At least a heat insulating layer is formed, and a booth is formed between the heat insulating layer and the resistor by thermal expansion of the resistor, and the resistor is buried in the heat insulating layer via the booth. The above-mentioned case is airtightly sealed to form a resistor, and the resistor is housed in a tank filled with sulfur hexafluoride gas, which is stacked and fixed in stages. Point earthing resistance device.