JP5848693B2 - Ground fault disaster prevention department and ground fault disaster prevention method - Google Patents

Description

  The present invention relates to a ground fault disaster prevention unit and a ground fault disaster prevention method for an OF cable, and more particularly, to a ground fault disaster prevention unit and a ground fault disaster prevention method applied to a terminal portion of an OF cable.

  An oil-filled power cable (OF cable: Oil Filled Cable) including a conductive core wire and an insulating material coated on the outer periphery of the conductive core wire and impregnated with insulating oil is used for, for example, underground transmission lines of high-voltage power It is used. Once a ground fault occurs due to a dielectric breakdown between the conductor portion of the OF cable and the ground, the oil in the OF cable may explode due to arc discharge accompanying the ground fault, causing a secondary disaster such as a fire. In order to suppress secondary disasters caused by ground faults, various disaster prevention measures have been taken for OF cables.

  For example, Patent Literature 1 discloses a ground fault prevention method for directly wrapping a complicated structure with an aramid fiber sheet having good followability with respect to a connecting portion for connecting OF cables and an offset portion provided in the vicinity thereof. Yes. Thus, it is possible to withstand the explosion pressure generated at the time of ground fault, shut off the air, and suppress the subsequent fire.

  Further, for example, Patent Document 2 discloses a method for obtaining the number of overlapping sheets required to obtain sufficient strength when overlapping aramid fiber sheets and wrapping a connection portion of an OF cable. According to Patent Document 2, the number of sheets can be calculated based on the gasification expansion energy KW (MJ) given to the oil in the OF cable by arc discharge.

Japanese Patent No. 3663103 Japanese Patent No. 4575895

  As for the OF cable, it is desirable to take a disaster prevention measure for the terminal portion as well as the connecting portion. However, the peripheral structure of the end portion of the OF cable is more complicated. For example, the end portion of the OF cable is accommodated in the space inside the gantry, and is connected to the end connection portion that connects the OF cable to various electric devices and the like. There are a wide variety of connection forms of the terminal portions, the shape and size of the gantry, and the installation locations and installation environments are also different.

  It has been difficult to apply a method of directly wrapping an end portion of an OF cable having such a complicated peripheral structure with an aramid fiber sheet or the like as in Patent Document 1, for example.

  In addition, for example, a difficulty is also recognized in wrapping the entire peripheral structure including the gantry with an aramid fiber sheet or the like. In a test in which a ground fault is generated in a simulated manner, even if a number of sheets of aramid fiber sheets that should have sufficient strength based on the calculation method of Patent Document 2 are stacked, they cannot withstand the explosion pressure caused by the ground fault. It has become.

  The objective of this invention is providing the ground fault disaster prevention part and ground fault disaster prevention method which can be applied to the termination | terminus part of OF cable which takes a complicated periphery structure.

According to a first aspect of the invention,
A pedestal for accommodating the terminal portion of the OF cable, which includes a conductive core wire and an insulating material coated on the outer periphery of the conductive core wire and impregnated with insulating oil;
A tear-resistant sheet provided so as to surround the outer surface of the gantry,
The material, thickness and number of tear resistant sheets are:
A ground fault energy KW for gasifying and expanding the oil impregnated in the insulating material of the OF cable by arc discharge;
Provided is a ground fault prevention unit determined based on combustion energy B when oil impregnated in the insulation material of the OF cable reacts with oxygen in the gantry and burns explosively. .

According to a second aspect of the invention,
The ground fault energy KW (MJ) is
An average value W (MW) of the electric power of the arc discharge;
Of the electric power of the arc discharge, the ratio β of the electric power involved in the gasification expansion of the oil impregnated in the insulating material of the OF cable,
The following equation (1) defined by the constant k related to the gasification expansion of the oil:
KW = k × β × W × 4.19 (1)
Sought by
The constant k related to the gasification expansion of the oil is
Specific gravity C ₀ (kg / m ³ ) of the oil;
Gas constant G (m / k) of the oil;
A gas temperature Gt (° C.) of the oil;
The following formula (2) defined by the energy Gq (kcal / kg) required for gasification of the oil:
k = (C ₀ × G / 9.8) × {Gt / (4.186 × Gq)} (2)
Is a constant that combines various constants by
The combustion energy B (MJ) is
A volume V (m ³ ) inside the frame;
The following formula (3) defined by the maximum calorific value Q (MJ / mol) of the oil,
B = 0.407 × V × Q (3)
The ground fault disaster prevention part as described in the 1st aspect calculated | required by is provided.

According to a third aspect of the invention,
The tear-resistant sheet is provided with the ground fault disaster prevention unit according to the first or second aspect made of an aramid fiber.

According to a fourth aspect of the invention,
The tear-resistant sheet is provided with a ground fault disaster prevention unit according to any one of the first to third aspects, which is made of an aramid fiber in which a layer containing a weather-resistant resin is formed.

According to a fifth aspect of the present invention,
A fixing plate abutted against the surface of the tear resistant sheet;
Any of the first to fourth aspects, comprising: a fixing screw that sandwiches the tear-resistant sheet with which the fixing plate is brought into contact between the fixing plate and the gantry and is fixed to the gantry together with the fixing plate. The ground fault disaster prevention department of crab is provided.

According to a sixth aspect of the present invention,
The ground fault disaster prevention part in any one of the 1st-5th aspect provided with the non-return valve which discharge | releases the atmosphere inside the said base will be provided when the pressure inside the said base exceeds a predetermined value.

According to a seventh aspect of the present invention,
The ground fault disaster prevention unit according to any one of the first to sixth aspects, comprising a reinforced plastic plate that is installed on the floor on which the gantry is installed and has strength to withstand the ground fault energy KW and the combustion energy B. Is provided.

According to an eighth aspect of the present invention,
A ground fault disaster prevention method that is performed on a terminal portion of an OF cable that is housed in a gantry and includes a conductive core wire and an insulating material that is coated on an outer periphery of the conductive core wire and impregnated with insulating oil,
A tear-resistant sheet is provided so as to surround the outer surface of the gantry,
When providing the tear-resistant sheet on the mount,
A ground fault energy KW for gasifying and expanding the oil impregnated in the insulating material of the OF cable by arc discharge;
Based on the combustion energy B when the oil impregnated in the insulating material of the OF cable reacts with oxygen in the gantry and burns explosively, the material, thickness, number of sheets of the tear resistant sheet A ground fault disaster prevention method is determined.

  ADVANTAGE OF THE INVENTION According to this invention, the ground fault disaster prevention part and ground fault disaster prevention method which can be applied to the termination | terminus part of OF cable which takes a complicated periphery structure are provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing of the ground fault disaster prevention part which concerns on one Embodiment of this invention, and a ground fault disaster prevention method, Comprising: (a) is a model which illustrates the periphery structure of the termination | terminus part of OF cable before a ground fault disaster prevention method is applied. It is a figure and (b) is a schematic diagram which illustrates the structure of the ground fault disaster prevention part after the ground fault disaster prevention method is applied to the structure of (a). It is a figure which shows a mode that the tear-resistant sheet | seat of the ground fault disaster prevention part which concerns on one Embodiment of this invention is fixed to a mount frame, Comprising: (a) is a cross-sectional perspective view, (b) is sectional drawing. It is a mimetic diagram illustrating the OF cable concerning one embodiment of the present invention.

<One Embodiment of the Present Invention>
The ground fault disaster prevention method according to an embodiment of the present invention is applied to a terminal portion of an oil-filled power cable (OF cable: Oil Filled Cable). Moreover, in this embodiment, the peripheral part including the terminal part of the OF cable to which the ground fault disaster prevention method according to this embodiment is applied is referred to as a ground fault disaster prevention unit.

(1) Peripheral structure of terminal part of OF cable First, an example of the peripheral structure of the terminal part of the OF cable before the ground fault disaster prevention method according to the present embodiment is applied will be described with reference to FIG. . FIG. 1 is an explanatory diagram of a ground fault disaster prevention unit 1 and a ground fault disaster prevention method according to an embodiment of the present invention, in which (a) shows an end portion 100c of an OF cable 100 before the ground fault disaster prevention method is applied. It is a schematic diagram which illustrates a surrounding structure.

  As illustrated in FIG. 3, the OF cable 100 includes, for example, a conductive core wire 101 and an insulating material 103 that is coated on the outer periphery of the conductive core wire 101 and impregnated with an insulating oil 102 (that is, impregnated with the oil 102). And comprising. The insulating material 103 is further covered with an insulating covering material (sheath) 104. As the insulating material 103, for example, insulating paper such as kraft paper is used. The insulating oil 102 is, for example, an alkylbenzene-based synthetic oil or mineral oil, and is impregnated in the insulating material 103 of the OF cable 100 while being constantly pressurized to a pressure equal to or higher than atmospheric pressure. The OF cable 100 is used, for example, for an underground transmission line of high-voltage power.

  FIG. 1A illustrates a peripheral structure in the case where the termination portion 100 c of the OF cable 100 is connected to the termination connection portion 200.

  As illustrated in FIG. 1A, the peripheral structure of the terminal portion 100c of the OF cable 100 includes a gantry 10 made of steel or the like. The gantry 10 has, for example, a rectangular upper plate 10 u and a substantially rectangular parallelepiped-shaped several meter cubic including four side walls 10 s each supporting four sides of the upper plate 10 u with the floor surface F on which the gantry 10 is installed as a base. It is formed in a box shape. On the four side walls 10 s corresponding to the outer surface of the gantry 10, for example, rectangular window portions 10 w that communicate the inside 10 h and the outside of the gantry 10 are provided. A terminal connection part 200 for connecting the terminal part 100c of the OF cable 100 to various electric devices and the like is accommodated in the interior 10h of the box-shaped gantry 10.

  The end portion 100c of the OF cable 100 whose periphery is covered with the protective tube 100p is connected to the lower end of the end connection portion 200. That is, the OF cable 100 is inserted into the interior 10h of the gantry 10 so as to penetrate the floor surface F on which the gantry 10 is installed, for example, from below the gantry 10, and the terminal portion 100c is connected to the terminal connector 200.

The upper end of the terminal connection part 200 is attached to the lower surface of the upper plate 10u of the gantry 10, for example. A conductor lead bar (not shown) that is electrically connected to the conductive core wire provided in the OF cable 100 protrudes from the upper end of the terminal connection part 200, and further passes through the upper plate 10u of the gantry, so It is connected to equipment. A conductor lead bar protruding from the upper plate 10 u is covered with an insulating insulator 300, and the periphery is filled with an insulating gas such as sulfur hexafluoride (SF ₆ ) gas.

  As described above, the OF cable includes insulating oil, insulating paper, or the like in its structure, and is used, for example, for transmitting high-voltage power. For this reason, once a ground fault occurs due to insulation breakdown between the conductor portion of the OF cable and the ground, the oil in the OF cable explodes due to arc discharge, and the sparks of the arc discharge ignited and the insulating paper are scattered around. May cause a secondary disaster such as a fire. Accordingly, various disaster prevention measures have been taken for connection portions and the like for connecting OF cables as in Patent Documents 1 and 2 described above.

  However, the end portion of the OF cable has a very complicated peripheral structure such as being housed inside a frame or the like. Further, the peripheral structure of the end portion 100c of the OF cable 100 shown in FIG. 1 (a) is merely an example, and the connection form of the end portion, the shape and size of the pedestal, etc. vary widely, The installation environment also varies widely, such as indoors or outdoors where the work space is not so large. Therefore, it has been difficult to apply the methods as disclosed in Patent Documents 1 and 2 as they are.

  Therefore, in the present embodiment, the ground fault disaster prevention unit and the ground fault disaster prevention method described below can be applied to a terminal part of an OF cable having a complicated peripheral structure.

(2) Ground fault disaster prevention part First, the ground fault disaster prevention part 1 which concerns on this embodiment is demonstrated using FIG.1 (b) and FIG. FIG. 1B is a schematic diagram illustrating the structure of the ground fault disaster prevention unit 1 after the ground fault disaster prevention method is applied to the structure of FIG. Drawing 2 is a figure showing signs that tear resistant sheet 20 of ground fault disaster prevention part 1 concerning this embodiment is fixed to mount 10, and (a) is a section perspective view and (b) is a section view. It is.

(Outline of the Earth Fault Disaster Prevention Department)
For example, as illustrated in FIG. 1B, the ground fault disaster prevention unit 1 according to the present embodiment surrounds the gantry 10 that houses the terminal portion 100 c of the OF cable 100 in the interior 10 h and the outer surface of the gantry 10. A tear resistant sheet 20 provided.

  That is, for example, a rectangular tear-resistant sheet 20 that is sufficiently larger than the window portion 10w is bonded to the window portion 10w provided on each of the four side walls 10s of the gantry 10. Specifically, the four sides of the tear-resistant sheet 20 are fixed by the fixing member 30 to a portion corresponding to the window frame of the side wall 10 s that borders the window portion 10 w with a certain degree of hermeticity. Details of the fixing member 30 will be described later.

  The tear-resistant sheet 20 is made of a tear-resistant material, that is, a material that is difficult to tear (not easily torn) so as to withstand the explosion pressure generated at the time of ground fault, and has high tensile strength, pressure resistance, and impact resistance. In addition, it has high flame resistance and heat resistance to withstand the combustion and heat generated at the time of ground fault. As a material having such characteristics, the tear resistant sheet 20 is made of, for example, an aramid fiber. An aramid fiber is a wholly aromatic polyamide fiber, and is a lightweight and flexible non-conductive organic fiber.

  However, the aramid fiber mentioned here is merely an example, and the material and the like of the tear resistant sheet 20 are determined based on the energy that the tear resistant sheet 20 receives due to the ground fault explosion pressure. Details of such energy will be described later.

  Further, the tear resistant sheet 20 is formed with a layer containing a weather resistant resin. The layer containing a weather resistant resin is a layer formed by impregnating or coating the tear resistant sheet 20 with a weather resistant resin such as polyvinyl chloride (PVC). Alternatively, the weather resistant resin is a layer formed in a sheet shape or a film shape and attached to the surface of the tear resistant sheet 20. In addition, the layer containing a weather resistant resin can be variously formed by a method suitable for the material. Further, the layer containing the weather resistant resin is at least on the surface of the tear resistant sheet 20 facing the outside of the mount 10 or on the surface of the outermost tear resistant sheet 20 in the case where a plurality of tear resistant sheets 20 are used. What is necessary is just to be provided.

  Moreover, the ground fault disaster prevention part 1 is equipped with the non-return valve 40 which discharge | releases the atmosphere of the inside 10h of the mount 10, for example in the outer surface of the mount 10, when the pressure inside the mount 10 exceeds a predetermined value. The check valve 40 is configured as, for example, a spring-type pressure release valve that is normally closed by a spring load. When the pressure in the gantry 10 suddenly increases due to a ground fault explosion pressure or the like, the spring load is removed by the pressure and the valve is opened, and the pressure in the gantry 10 is released to alleviate the pressure increase in the gantry 10. It is configured as follows.

  As the check valve 40, various types of check valves, pressure release valves, etc., such as a lift method, a swing method, a ball method, a butterfly method, and a wafer method, can be used. Further, as shown in FIG. 1B, the installation position can be the outer surface of any one of the side walls 10s, or can be installed on the upper surface of the upper plate 10u.

  Moreover, the ground fault disaster prevention unit 1 is installed on the floor surface F on which the gantry 10 is installed, and has the strength to withstand the energy of the explosion pressure generated at the time of the ground fault, that is, the ground fault energy KW and the combustion energy B described later. A reinforced plastic plate 50 is provided. As the reinforced plastic plate 50, for example, a polymer-concrete fiber reinforced plastic (PFRP) plate in which resin concrete (polymer concrete) and fiber reinforced plastic are combined can be used.

  As described above, the ground fault disaster prevention unit 1 according to the present embodiment is configured.

(Fixing member)
In FIG. 2, the detail of the fixing member 30 which fixes the tear-resistant sheet | seat 20 to the mount frame 10 is shown.

  As shown in FIG. 2, the fixing member 30 that fixes the tear-resistant sheet 20 to the gantry 10, for example, abuts the metal plate 31 as a fixing plate that comes into contact with the surface of the tear-resistant sheet 20 and the metal plate 31. Bolts 32b and nuts 32n as fixing screws for fixing the tear resistant sheet 20 to the gantry 10 together with the metal plate 31, and a wire 33 as a core part passing through the folded part 20r where the end of the tear resistant sheet 20 is folded; Is provided.

  Among the fixing members 30, the tear-resistant sheet 20 with the metal plate 31 in contact with the surface borders the metal plate 31 and the window portion 10 w of the gantry 10 with the end portions of the four sides folded back. It is sandwiched between a portion corresponding to the window frame of the side wall 10s. A wire 33 is passed through a folded portion 20r that is inside the folded line of the tear resistant sheet 20. In FIG. 2, the folded back side of the tear-resistant sheet 20 faces toward the gantry 10 side, but it may face in the opposite direction.

  In portions where the metal plate 31, the tear resistant sheet 20, and the side wall 10s of the gantry 10 overlap, a plurality of through holes (not shown) are provided at equal intervals at positions corresponding to each other. That is, the plurality of through holes are provided along the long axis direction of the long metal plate 31. Further, the tear-resistant sheet 20 is provided along the end portions of the folded four sides, and is provided along the window frame portion of the side wall 10 s of the gantry 10.

  Bolts 32 b are inserted into the plurality of through holes so as to penetrate the gantry 10, the tear resistant sheet 20, and the metal plate 31 from the inside of the gantry 10, for example. Further, from the outside of the gantry 10, that is, from above the metal plate 31, a nut 32n is fitted into the bolt 32b. As described above, the tear-resistant sheet 20 is fixed to the gantry 10 together with the metal plate 31 by the bolts 32b and the nuts 32n.

  Here, specific numerical values relating to the bolts 32b used are exemplified. As the bolt 32b, for example, a bolt having a strength classification of 4.8 or more and a screw thickness of 12 mm (nominal diameter: M12) according to JIS standards can be used. Moreover, the pitch (interval) between each volt | bolt 32b can be 100 mm or less, for example. The pitch between the bolts 32 b can be defined by the distance between the through holes provided in the side wall 10 s of the gantry 10, the tear resistant sheet 20, and the metal plate 31.

  FIG. 2 shows a case where one tear-resistant sheet 20 is bonded to one side wall 10s. However, if necessary, a plurality of tear-resistant sheets are stacked on one side wall 10s. In some cases, the sheet 20 is laminated.

  That is, in the above configuration, in addition to the material and thickness of the tear-resistant sheet 20, the number of sheets to be superimposed is determined as necessary so as to obtain a strength that can withstand the explosion pressure during a ground fault. The energy of the explosion pressure at the time of the ground fault is calculated based on the ground fault energy KW and the combustion energy B described later. When it is calculated that a plurality of sheets need to be overlapped, for example, the tear-resistant sheet 20 is sandwiched between the metal plate 31 and the gantry 10 by the number of sheets to be overlapped.

  As described above, the ground fault prevention unit 1 according to the present embodiment is configured in the terminal end portion 100c of the OF cable 100.

(3) Grounds for material, thickness, and number of tear-resistant sheets Next, ground fault energy KW and combustion energy B, which are grounds for determining the material, thickness, and number of sheets to be stacked, will be described. To do.

  In the above-mentioned Patent Document 2, the configuration in which the box-shaped trough covering the connection portion of the OF cable is wrapped with an aramid fiber sheet, and the number of aramid fiber sheets necessary to obtain sufficient strength at this time are arced. Describes a method of calculating based on the energy KW (MJ) given by.

  However, when the calculation method according to Patent Document 2 is applied to the above-described configuration in which a tear-resistant sheet is provided on the outer surface of the gantry and an aramid fiber sheet is used as the tear-resistant sheet, the number of sheets to be superimposed is simulated. In the generated test, the aramid fiber sheet was not able to withstand the explosion pressure caused by the ground fault, and the aramid fiber sheet was broken.

  As a result of intensive studies, the present inventors have conceived that the energy received by the tear-resistant sheet 20 according to the present embodiment due to the explosion pressure due to the ground fault is captured by the concept of the following explosion energy E (MJ). Based on this explosive pressure energy E (MJ), the material, thickness, and number of overlapping sheets of the tear-resistant sheet 20 are determined so that the explosive pressure due to the ground fault can be sufficiently resisted.

  That is, the explosive pressure energy E was impregnated in the ground fault energy KW that gasifies and expands the oil 102 impregnated in the insulating material 103 of the OF cable 100 by arc discharge and in the insulating material 103 of the OF cable 100. It is calculated based on the combustion energy B when the oil 102 is explosively burned by reacting with oxygen in the gantry 10.

  For example, when a ground fault occurs in the interior 10h of the gantry 10 in which the terminal portion 100c of the OF cable 100 is accommodated, the oil 102 that has been impregnated in the insulating material 103 of the OF cable 100 by receiving a part of the electric power of the arc discharge. Suddenly gasifies and expands (primary explosion). At the same time, instantaneous and explosive combustion of the oil 102 occurs (secondary explosion). Such a rapid gasification expansion and instantaneous and explosive combustion of the oil 102 become an explosion pressure that the tear resistant sheet 20 receives during a ground fault. In the present embodiment, the material of the tear resistant sheet 20 is based on the explosion energy E taking into account the combustion energy B when the oil 102 is explosively burned together with the ground fault energy KW that gasifies and expands the oil 102. Determine thickness, number of overlays.

  As described above, in Patent Document 2, the required number of aramid fiber sheets is calculated based on the gasification expansion energy KW (MJ) given to the oil in the OF cable by arc discharge. Energy B was not taken into account. However, in the above-mentioned Patent Documents 1 and 2, there is only a very small gap in the trough kept airtight with the aramid fiber sheet. Therefore, even if the oil of the OF cable burns instantaneously in the trough, the air in the trough and the amount of oxygen contained in the air are extremely limited and are immediately extinguished by the suffocation effect by the aramid fiber sheet. . Therefore, sufficient strength to withstand the explosion pressure at the time of the ground fault has been obtained without taking into consideration the combustion energy B considered to have a small contribution to the explosion pressure at the time of the ground fault.

  However, in the ground fault disaster prevention unit 1 according to the present embodiment, the gantry 10 has a substantially rectangular parallelepiped shape of, for example, several meters cubic. Thus, the volume of the interior 10h of the gantry 10 is so large that it cannot be compared with the trough, and the air in the gantry 10 and the amount of oxygen contained in the air become enormous. Therefore, when the oil 102 burns by consuming oxygen in the gantry 10, a huge amount of combustion energy B is generated by explosive combustion. Therefore, as described above, the combustion energy B needs to be taken into consideration in order to obtain a structure that can sufficiently withstand the explosion pressure during a ground fault.

(Equation for calculating ground fault energy)
The calculation formula of the ground fault energy KW is shown below.

Ground fault energy KW (MJ) is
An average value W (MW) of arc discharge power,
The ratio β of the electric power involved in the gasification expansion of the oil impregnated in the insulation material of the OF cable out of the electric power of the arc discharge,
The following formula (1) defined by the constant k related to the gasification expansion of the oil:
KW = k × β × W × 4.19 (1)
Is required.

  Here, the average value W of arc discharge power is, for example, the power of arc discharge of the so-called ground fault first wave, which arcs to the ground due to dielectric breakdown between the conductor portion of the OF cable 100 and the ground and reaches the ground fault. It is an average value of and fluctuates depending on the size of the ground fault. Due to the first ground fault wave, for example, the protective tube 100p covering the end portion 100c of the OF cable 100 is broken.

  Moreover, the oil 102 in the insulating material 103 of the OF cable 100 is rapidly gasified and expanded by the first ground fault wave. That is, a part of electric power of arc discharge is used as energy for gasification expansion. The ratio β is a ratio of electric power used (participated) in gasification expansion.

Also,
The constant k related to the gasification expansion of the oil is
Specific gravity C ₀ (kg / m ³ ) of the oil,
The gas constant G (m / k) of the oil,
The gas temperature Gt (° C.) of the oil,
The following formula (2) defined by the energy Gq (kcal / kg) necessary for the gasification of the oil:
k = (C ₀ × G / 9.8) × {Gt / (4.186 × Gq)} (2)
Is a constant obtained by combining various constants.

(Calculation formula of combustion energy)
The calculation formula of the combustion energy B is shown below.

Combustion energy B (MJ) is
Volume V (m ³ ) inside the gantry,
The following formula (3) defined by the maximum calorific value Q (MJ / mol) of the oil,
B = 0.407 × V × Q (3)
Is required.

Here, the combustion energy B assumes, for example, that all the oxygen in the gantry 10 is consumed and the oil 102 in the OF cable 100 is combusted. Therefore, the calorific value per mol (/ mol), which is the maximum calorific value Q of the oil 102 in the OF cable 100, is multiplied by the consumed oxygen amount. As the amount of oxygen consumed, 9.35 (mol) obtained by converting the volume% of oxygen contained in the air per unit volume (/ m ³ ) into the number of moles, and further per mole (/ mol) The coefficient is 0.407 divided by 23 (mol) which is the number of moles of oxygen necessary for the combustion of the oil 102.

  In the above description, as the volume V of the interior 10h of the gantry 10 increases, the amount of oxygen in the gantry 10 increases and instantaneous and explosive combustion is promoted. However, the combustion pressure that reaches the tear-resistant sheet 20 decreases as the space increases. Conversely, as the volume V decreases, the amount of oxygen in the gantry 10 decreases and combustion is suppressed, but the combustion pressure easily reaches the tear resistant sheet 20. Therefore, the volume V of the interior 10h of the gantry 10 has a volume where the combustion energy E is maximum.

  Further, a tear resistant sheet 20 is provided on the outer surface of the gantry 10 with a certain degree of hermeticity. Therefore, in the above, after the oxygen in the gantry 10 is consumed, the inflow of new oxygen from the outside of the gantry 10 is suppressed, the inside of the gantry 10 is digested, and combustion spreads outside the gantry 10 (fire spreads). ) Is suppressed.

(Calculation formula of explosive pressure energy)
The calculation formula of the explosion energy E is shown below.

Explosive pressure energy E (MJ) is
Taking into account the contributions k1 and k2 of the respective energies, the following equation is obtained by adding the ground fault energy KW obtained by the above equation (1) and the combustion energy B obtained by the above equation (3). (4),
E = k1 × KW + k2 × B (4)
Is required.

  Based on the above formulas (1) to (4) defined as described above, the material, thickness, and number of overlapping sheets of the tear resistant sheet 20 are determined.

  As described above, the explosion energy E varies depending on the size of the ground fault, the type of the oil 102 included in the OF cable, the volume of the interior 10h of the gantry 10, and the like. That is, the material, thickness, and number of overlapping sheets of the tear resistant sheet 20 are determined by using the size of the ground fault, the type of oil 102, the volume in the gantry 10, and the like as variables.

(4) Ground fault disaster prevention method The structure of said ground fault disaster prevention part 1 is obtained by the ground fault disaster prevention method which concerns on this embodiment. That is, the ground fault disaster prevention method according to the present embodiment is performed on the terminal end portion 100c of the OF cable 100 housed in the interior 10h of the gantry 10 illustrated in FIG. In the ground fault disaster prevention method according to the present embodiment, the tear resistant sheet 20 is provided so as to surround the outer surface of the gantry 10.

  At this time, the grounding energy KW for gasifying and expanding the oil 102 impregnated in the insulating material 103 of the OF cable 100 by arc discharge and the oil 102 impregnated in the insulating material 103 of the OF cable 100 are the base 10. The material, thickness, and number of tear resistant sheets 20 are determined based on the combustion energy B when explosively combusting by reacting with the oxygen therein. A layer containing a weather resistant resin may be formed on the outermost surface of the tear resistant sheet 20.

  Further, when the tear resistant sheet 20 is provided on the gantry 10, the fixing member 30 is used. That is, the wire 33 is passed through the folded portion 20r where the end portion of the tear resistant sheet 20 is folded. The tear resistant sheet 20 is sandwiched between the metal plate 31 and the gantry 10. A bolt 32b is inserted so as to penetrate the gantry 10, the metal plate 31, and the tear resistant sheet 20, and a nut 32n is fitted.

  Further, a check valve 40 is provided on the outer surface of the gantry 10 to release the atmosphere inside the gantry 10 when the pressure inside the gantry 10 exceeds a predetermined value.

  Moreover, the reinforced plastic board 50 which has the intensity | strength which can withstand the ground fault energy KW and the combustion energy B is installed in the floor surface F in which the mount frame 10 is installed.

  The order in which these methods are performed does not depend on the order described above.

(5) Effects according to the present embodiment According to the present embodiment, the following one or more effects are achieved.

(A) In other words, in this embodiment, the tear resistant sheet 20 is provided so as to surround the outer surface of the gantry 10 that houses the terminal portion 100c of the OF cable 100 in the interior 10h. Thus, since the entire frame 10 covers the end portion 100c of the OF cable 100, it can be applied to the end portion 100c of the OF cable 100 having a complicated peripheral structure.

(B) Moreover, in this embodiment, the tear-resistant sheet | seat 20 is used, without using the plate-shaped member etc. which have rigidity, for example. Thereby, when a ground fault occurs, for example, the tear-resistant sheet 20 bends to the outside of the gantry 10, so that it is possible to absorb the impact of the explosion pressure while allowing the explosion due to the explosion pressure to some extent. Therefore, an explosion or the like due to a ground fault can be contained in the gantry 10 more reliably.

(C) Moreover, in this embodiment, the material, thickness, and number of sheets of the tear resistant sheet 20 are determined based on the ground fault energy KW and the combustion energy B. Moreover, said Formula (1)-(4) is used at this time. This provides sufficient strength to withstand explosive pressure, including instantaneous and explosive combustion, for example in a gantry 10 that has a much larger amount of oxygen than in the trough.

  As described above, the volume V of the interior 10h of the gantry 10 has a volume where the combustion energy E is maximum. The present inventors provided an aramid fiber sheet as a tear-resistant sheet on the outer surface of the gantry having such a volume, and conducted a ground fault simulation test. At this time, specifications such as the number of overlapping sheets were determined based on the calculation method of Patent Document 2 and the formulas (1) to (4) according to the present embodiment, and the result of the simulation test was obtained for each specification.

  According to this, in the specification based on Patent Document 2, the aramid fiber sheet was broken because it could not withstand the explosive combustion that occurred in the gantry having a large amount of oxygen. On the other hand, in the specification based on this embodiment, the aramid fiber sheet did not break.

(D) Moreover, in this embodiment, the material, thickness, and number of sheets of the tear resistant sheet 20 are determined based on said Formula (1)-(4). This takes into account variables that are sometimes different, such as the size of the ground fault included in the above formulas (1) to (4), the type of oil 102 contained in the OF cable 100, the volume of the interior 10h of the gantry 10, and so on. Therefore, the structure can withstand explosion pressure more reliably.

(E) Moreover, in this embodiment, the tear-resistant sheet | seat 20 consists of an aramid fiber. In this way, by using a material having not only tear resistance, high tensile strength, pressure resistance, and impact resistance, but also flame resistance and heat resistance, it can withstand combustion and heat generated in the event of a ground fault. Fire spread to the outside can be suppressed.

(F) Moreover, an aramid fiber is a nonelectroconductive organic fiber. Therefore, higher safety is ensured at the terminal portion 100c of the OF cable 100 used for power transmission of high-voltage power, for example, during normal times and when arc discharge occurs due to a ground fault.

(G) Moreover, in this embodiment, the tear resistant sheet 20 consists of an aramid fiber in which the layer containing a weather resistant resin was formed. Thereby, for example, even when the gantry 10 is installed outdoors or the like, the tear resistant sheet 20 can be provided with weather resistance, and the life can be extended.

(H) In the present embodiment, the tear resistant sheet 20 is sandwiched between the metal plate 31 and the gantry 10 and fixed to the gantry 10 together with the metal plate 31. Thereby, for example, even if the tear resistant sheet 20 receives a ground fault explosion pressure and bends to the outside of the gantry 10, the periphery of the through hole of the tear resistant sheet 20 into which the bolt 32b is inserted is pressed by the metal plate 31. . Therefore, it can suppress that the tear-resistant sheet | seat 20 is pulled with the volt | bolt 32b, and tears from a through-hole as a starting point.

(I) Moreover, the metal plate 31 is brought into contact with and the tear-resistant sheet 20 is fixed to the gantry 10, whereby the sealing property of the tear-resistant sheet 20 to the gantry 10 can be further improved. Therefore, it is possible to suppress the scattering of the explosion caused by the ground fault from spreading to the outside of the gantry 10 and the spread of combustion due to the inflow of new oxygen.

(J) In this embodiment, a bolt 32b having a strength classification of 4.8 or more and a nominal diameter of M12 according to the JIS standard is used. Further, the pitch (interval) between the bolts 32b is set to 100 mm or less. As a result, it has been confirmed that the above-described performance can be sufficiently obtained at least in a ground fault simulation test.

(K) Moreover, in this embodiment, when the pressure of the inside 10h of the gantry 10 exceeds a predetermined value, the check valve 40 that releases the atmosphere of the inside 10h of the gantry 10 is provided. Thus, when a ground fault explosion pressure occurs, the pressure in the gantry 10 can be quickly reduced, and the impact of the explosion pressure on the tear resistant sheet 20 can be reduced.

(L) Moreover, in this embodiment, the reinforced plastic board 50 which has the intensity | strength which is installed in the floor surface F in which the mount frame 10 is installed, and withstands ground fault energy KW and combustion energy B is provided. Thereby, it is suppressed that the floor surface F in which the mount frame 10 is installed is damaged or deform | transformed by the ground fault explosion pressure, combustion, etc., and the floor surface F can be protected.

<Other Embodiments of the Present Invention>
As mentioned above, although embodiment of this invention was described concretely, this invention is not limited to the above-mentioned embodiment, It can change variously in the range which does not deviate from the summary.

  For example, in the above-described embodiment, the ground fault disaster prevention unit 1 and the ground fault disaster prevention method that are mainly applied to the peripheral structure of the terminal end portion 100c of the OF cable 100 illustrated in FIG. The ground fault disaster prevention unit and the ground fault disaster prevention method according to the present invention can be applied to terminal portions having various different peripheral structures.

  In the above-described embodiment, one or a plurality of stacked tear-resistant sheets 20 are attached to one side wall 10s of the gantry 10, but the present invention is limited to such a configuration. Absent. For example, a long tear-resistant sheet may be wound around the gantry as many times as necessary, or the outer surface of the gantry may be covered with a cylindrical tear-resistant sheet. Further, the tear-resistant sheet may be folded into four, eight, or zigzag folds.

  In the above embodiment, the OF cable 100 is illustrated in FIG. 3, but the structure of the OF cable to which the present invention is applied is not limited thereto. For example, not only a single core cable having one conductive core wire 101 as shown in FIG.

  Moreover, the layer containing the weather resistant resin formed in the tear resistant sheet 20 according to the above-described embodiment, the check valve 40 provided on the outer surface of the gantry 10, and the reinforced plastic plate provided on the floor surface F on which the gantry 10 is installed 50 or the like is not an essential requirement of the present invention.

DESCRIPTION OF SYMBOLS 10 Base 10h Inside 10s Side wall 10u Top plate 10w Window part 20 Tear resistant sheet 30 Fixing member 31 Metal plate (fixing plate)
32b Bolt 32n Nut 33 Wire 40 Check valve 50 Reinforced plastic plate 100 OF cable 100c Termination portion 100p Protection tube 200 Termination connection portion 300 Insulator F Floor

Claims (8)

A pedestal that houses therein a terminal portion of an OF cable that includes a conductive core wire and an insulating material coated on the outer periphery of the conductive core wire and impregnated with insulating oil ; and a window provided on a side wall ;
A tear-resistant sheet provided so as to close the window of the gantry,
The material, thickness and number of tear resistant sheets are
A ground fault energy KW for gasifying and expanding the oil impregnated in the insulating material of the OF cable by arc discharge;
The oil impregnated in the insulation material of the OF cable is determined based on combustion energy B when it explosively burns by reacting with oxygen in the gantry ,
A ground fault disaster prevention unit configured to contain explosion pressure in the gantry by bending the tear resistant sheet when an explosion occurs due to a ground fault. The ground fault energy KW (MJ) is
An average value W (MW) of the electric power of the arc discharge;
Of the electric power of the arc discharge, the ratio β of the electric power involved in the gasification expansion of the oil impregnated in the insulating material of the OF cable,
The following equation (1) defined by the constant k related to the gasification expansion of the oil:
KW = k × β × W × 4.19 (1)
Sought by
The constant k related to the gasification expansion of the oil is
Specific gravity C ₀ (kg / m ³ ) of the oil;
Gas constant G (m / k) of the oil;
A gas temperature Gt (° C.) of the oil;
The following formula (2) defined by the energy Gq (kcal / kg) required for gasification of the oil:
k = (C ₀ × G / 9.8) × {Gt / (4.186 × Gq)} (2)
Is a constant that combines various constants by
The combustion energy B (MJ) is
A volume V (m ³ ) inside the frame;
The following formula (3) defined by the maximum calorific value Q (MJ / mol) of the oil,
B = 0.407 × V × Q (3)
It is calculated | required by these, The ground fault disaster prevention part of Claim 1 characterized by the above-mentioned. The ground fault disaster prevention unit according to claim 1 or 2, wherein the tear resistant sheet is made of an aramid fiber. The ground fault disaster prevention part according to any one of claims 1 to 3, wherein the tear resistant sheet is made of an aramid fiber in which a layer containing a weather resistant resin is formed. A fixing plate abutted against the surface of the tear resistant sheet;
A fixing screw that sandwiches the tear-resistant sheet with the fixing plate abutted between the fixing plate and the gantry and fixes the fixing plate together with the fixing plate to the gantry. The ground fault disaster prevention part in any one of 4. The ground fault disaster prevention unit according to any one of claims 1 to 5, further comprising a check valve that releases an atmosphere inside the mount when a pressure inside the mount exceeds a predetermined value. The ground according to any one of claims 1 to 6, further comprising a reinforced plastic plate that is installed on a floor on which the gantry is installed and has strength to withstand the ground fault energy KW and the combustion energy B. Tangle Disaster Prevention Department. A ground fault that is accommodated in a base having a window provided on a side wall, and that is performed on a terminal end portion of an OF cable that includes a conductive core wire and an insulating material that is coated on an outer periphery of the conductive core wire and impregnated with insulating oil. A disaster prevention method,
A tear-resistant sheet is provided so as to close the window portion of the gantry,
When providing the tear-resistant sheet on the mount,
A ground fault energy KW for gasifying and expanding the oil impregnated in the insulating material of the OF cable by arc discharge;
Based on the combustion energy B when the oil impregnated in the insulating material of the OF cable reacts with oxygen in the gantry and burns explosively, the material, thickness, number of sheets of the tear resistant sheet to determine,
A ground fault disaster prevention method characterized in that, when an explosion occurs due to a ground fault, the explosion resistant sheet is bent to contain the explosion pressure in the gantry .

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