JP2005149759A - Low-voltage lead-in wire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-voltage lead-in wire capable of preventing an ignition or disconnection accident due to a discharge phenomenon on the surface of a core wire insulator by improving tracking resistance, and allowing the core wire to be easily identified by touching an insulating coating. <P>SOLUTION: Surfaces of the insulators 15 of the core wires 12 and 13 in this low-voltage lead-in wire 1 are formed into continuous forms of cross-sectional shapes where a plurality projections 16 are circumferentially formed at predetermined intervals to provide continuous uneven shapes to core wire surfaces; and the core wires adjacent to one another by being intertwined with one another are brought into a state that spaces are formed between the respective core wires 11, 12 and 13 by making outside surfaces on the other side adjacent to a part of a groove 17 between the projections 16 on one side to secure a large insulation creeping distance for each core wire, whereby tracking resistance is enhanced, discharge caused by a tracking phenomenon and the carbonization of the insulator associated with the carbonization are prevented from easily occurring, damage and a crack on the insulator 15 hardly leads to an arc short circuit, and a risk of a ignition or disconnection accident is reduced, so that reliability is enhanced. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a low-voltage lead-in wire used for power supply in a section from a low-voltage distribution line to a building, and particularly relates to a low-voltage lead-in wire excellent in tracking resistance and handling properties.

  Among electric wires and cables used for power supply, two or more strands or individual cores are used as outdoor low-voltage lead-in wires that are installed or installed between the low-voltage distribution line and the customer's building. There is a flat DV electric wire arranged in parallel, and the one using vinyl chloride resin as an insulator is common.

  In each of the strands of the low-voltage lead-in wires that are twisted together, the insulators that cover the conductors are made of different colored resins so that they can be identified. If these insulators are made of a resin other than black, that is, a resin that does not contain carbon, these insulators have a smaller ultraviolet blocking effect than black resin-containing insulators that contain carbon. Oxidative degradation is likely to occur, and cracks due to degradation were likely to occur under sunlight. As cracks and scratches in the insulator progress, the conductor is partially exposed.

  On the other hand, in such an electric wire, when the surface of the insulator is wet or fouled, a leakage current flows along the surface of the insulator, and the surface is locally dried along with the evaporation of moisture due to the generated Joule heat. As a result, the electric field becomes irregular, and a local micro discharge with minute light emission called scintillation occurs, and a tracking phenomenon occurs in which a part of the insulating material is decomposed by the heat accompanying this discharge and carbide is generated. Sometimes it happened. This phenomenon is more likely to occur when dust containing salt accumulates on the wire surface.

  When a tracking phenomenon occurs in two or more low-voltage lead-in wires, the carbide generated from the insulator has a high conductivity, so the leakage current between the core wires flows through it, and the electric field concentrates in the vicinity, scintillation, carbide generation This process is promoted and carbides grow further. Soon, the space between the core wires is covered with a highly conductive carbide, and a leakage current always flows.

  When there is a conductor exposed portion due to cracks or scratches on the surface of the insulator in the portion where the core wires of the low-voltage lead-in wire are close to each other, when the carbide has grown due to the tracking phenomenon in the vicinity of the conductor exposed portion When appropriate moisture is supplied to the surface of the insulator due to light rain, drizzle, mist, condensation, etc., scintillation (spark discharge) occurs and induces arc discharge between exposed portions of the conductor. When the deterioration of the insulator progresses to a state where the arc discharge is continuously generated, the conductor is softened and melted by the heat of the arc discharge, cannot withstand the installation tension, and is disconnected.

  For the problem of deterioration of such a low-voltage lead-in electric wire, an insulating layer made of black resin further containing carbon is disposed outside the insulator of a predetermined color covering the conductor, and the deterioration of the insulator is prevented. An example of a low-voltage lead-in electric wire that enables identification of each core wire at the end is disclosed in Japanese Patent Laid-Open No. 2002-324443.

  On the other hand, the tracking phenomenon can occur due to the adhesion of salt and moisture to the surface of high-voltage insulated wires, and there is a problem that the insulation performance deteriorates and the life of the wires is shortened. In recent years, various types of electric wires have been proposed in which a conductive portion is less likely to be formed on the surface of the insulator and can prevent deterioration of the insulator due to the tracking phenomenon. As an example, Japanese Patent Laid-Open No. 2000-133048 has been proposed. JP-A-2001-52535 and JP-A-2002-358839.

The conventional electric wires shown in each of the above publications are insulated electric wires having a resin in which a metal hydroxide is blended with a polyolefin-based or rubber-based resin as an outermost insulator, and have a sufficient resistance against mechanical strength. The tracking property is improved, the insulation performance is stable over a long period of time, and the occurrence of the tracking phenomenon is prevented.
JP 2002-324443 A JP 2000-1333048 A JP 2001-52535 A JP 2002-358839 A

  The conventional cable is configured as described above, and in the case of the conventional low-voltage lead-in wire shown in Patent Document 1, although it is strong against deterioration due to ultraviolet rays, the insulator may be damaged or damaged by various factors other than ultraviolet rays. Cracks may occur, and the progress of these may cause partial exposure of the conductor. Cases where this exposed conductor part is formed are: (1) If a strong wind such as a typhoon hits the electric wire with a flying object such as tin, and (2) it is mistakenly caused by dragging the electric wire during construction. There are cases where scratches are made, and (3) cases where the insulator is scraped by friction due to contact with other electric wires after construction.

  Vinyl chloride resin insulators commonly used for conventional low-voltage lead-in wires have excellent workability such as lead-out, but are easily scratched and easily worn, and are resistant to tracking. Because the performance is remarkably inferior, in the case of two or more low-voltage lead-in wires that use vinyl chloride resin as the insulator, if the exposed conductors due to scratches are formed on the two cores that are close to each other, they will be wet. Due to the tracking phenomenon that occurs in the state, the insulator further deteriorates, and there is a problem that the rate at which arc discharge occurs between the exposed portions of the conductor and leads to disconnection becomes extremely high.

  On the other hand, the conventional tracking-resistant insulated wires shown in Patent Documents 2 to 4 are high-voltage wires formed by covering a plurality of insulated core wires with an insulator made of a tracking-resistant composition. It is not considered as a low-voltage lead-in wire that is twisted or integrated in parallel, but simply by diverting the same material used for the insulator to the insulator of the low-voltage lead-in wire Strength and tracking resistance will be insufficient, and it will not be possible to stop the progress of scratches and cracks caused by various factors during and after construction. If the conductor is partially exposed, the tracking phenomenon that occurs between the two adjacent conductors eventually induces an arc discharge between the exposed conductors, and breakage of the arc due to the arc discharge occurs. There is a problem that the insurance property is high.

  The present invention has been made to solve the above-mentioned problems, and can improve tracking resistance and prevent ignition and disconnection accidents due to a discharge phenomenon on the surface of the core insulator, and can be easily touched with an insulating coating by hand. An object of the present invention is to provide a low-voltage lead-in electric wire that can identify a core wire.

  The low-voltage lead-in electric wire according to the present invention is a low-voltage lead-in electric wire obtained by twisting a plurality of insulated core wires, and at least one of the core wires having a predetermined outer diameter R has a surface circumferential direction angular range φ. A cross-sectional shape in which n protrusions having a height L from the outer diameter position are arranged at equal intervals in the circumferential direction of the surface, or a shape portion in which at least a predetermined length is continued in the longitudinal direction of the core wire The two core wires adjacent to each other in the twisted state are adjacent to the outer periphery of the other core wire at the groove position between the projecting portions in one core wire, The distance d between the core wire outer surface positions on the line connecting the conductor centers of the core wires with the shortest distance is set to 0.1 (mm) ≦ d ≦ R / 2.

  Thus, in the present invention, the insulator surface of at least one core wire in the low-voltage lead-in wire is formed in a continuous state having a cross-sectional shape in which a plurality of protrusions are provided at predetermined intervals in the circumferential direction, and is continuous with the surface of the core wire. Each of the cores that are twisted and adjacent to each other are provided with a gap between the cores with the outer surface of the other core wire adjacent to the groove portion between the protrusions of the one core wire. By making the insulation creepage distance between the lines larger than in the case of a simple circular cross-sectional shape, the tracking resistance can be improved, and the discharge due to the tracking phenomenon and the resulting carbonization of the insulator are unlikely to occur, and various factors It is almost impossible to lead to an arc short circuit between the exposed parts of the conductor due to scratches and cracks in the insulator, and the risk of ignition and disconnection accidents can be reduced and reliability can be improved.

  In addition, in the low-voltage lead-in electric wire according to the present invention, if any one of the core wires has a circular cross-sectional shape without projections and there are a plurality of other core wires, the number n of each projection and In other words, the protrusions are formed as cross-sectional shapes in which the circumferential angle ranges φ of the protrusions are different from each other.

  In this way, in the present invention, one of the core wires is formed into a circular cross section, and when there are a plurality of remaining core wires, the core wire is formed with a different cross-sectional shape, and the outer shape of each core wire is set to each core. By making the wires different from each other, the core wires can be easily identified visually or tactilely, and even if the colors are the same, the core wires can be reliably identified, and the cores such as conductor exposure, phase confirmation during connection, installation or inspection can be confirmed. Various workability for the wire can be greatly improved.

  Further, in the low-voltage lead-in electric wire according to the present invention, if necessary, at least one of the core wires has a groove width in an angle range δ smaller than the circumferential angle range φ of the protrusion on at least one surface of the protrusion portion, and One or a plurality of grooves having a groove depth l smaller than the height L from the outer diameter position of the protrusion are continuously formed in the longitudinal direction of the core wire in a parallel state.

  As described above, in the present invention, a separate groove is provided in a continuous protrusion portion on the surface of the core wire, and the insulation creepage distance in the core wire is further increased, so that the discharge caused by the tracking phenomenon and the carbonization of the insulator accompanying this are caused. It is even less likely to occur, eliminating the risk of arc shorts between exposed conductors, improving safety and reliability, and the presence of small grooves increases core line discrimination and leads to work core lines. Mistakes in handling are less likely to occur.

  Further, the low-voltage lead-in electric wire according to the present invention is a low-voltage lead-in electric wire formed by twisting a plurality of insulated core wires, and is closest to one or more core wires on the outer peripheral surface of each core wire in a twisted state. Alternatively, one or a plurality of juxtaposed ridges that engage each other between the core wires are formed in a plurality of substantially spiral continuous portions, respectively, while the ridge portions are respectively disposed on the plurality of core wires. In this method, the number of the protrusions is made different for each core wire.

  As described above, in the present invention, the ridges are formed in the substantially spiral portion of the surface of each core wire that is in the vicinity of the other core wires in the twisted state of the core wires, and the ridge portions are connected to each other between the core wires. In addition, by keeping twisted together while securing a certain amount of spacing between the core wires, the insulation creepage distance between the core wires is made larger than in the case of a simple circular cross-sectional shape, thereby improving tracking resistance. In addition, the discharge due to the tracking phenomenon and the resulting carbonization of the insulator are unlikely to occur, and there is almost no possibility of an arc short circuit due to the scratches and cracks of the insulator due to various factors, reducing the risk of ignition and disconnection accidents And improve reliability. Furthermore, by changing the number of ridges for each core wire and making the outer shape of each core wire different, the core wire can be easily identified visually or tactilely, even if the color is the same, It can be identified, and various operability with respect to the core wire such as conductor exposure, connection, laying, or phase confirmation during inspection can be greatly improved.

  Further, the low-voltage lead-in electric wire according to the present invention is a low-voltage lead-in electric wire formed by twisting a plurality of insulated core wires, forming one or a plurality of protrusions continuous in the longitudinal direction on at least one core wire surface, When at least one of the strands of the core wire is positioned at a predetermined interval based on the twisting pitch between the core wires that are adjacent to each other in the aligned state, and the strips are respectively disposed on the plurality of core wires In this method, the number of the protrusions is made different for each core wire.

  As described above, in the present invention, a protruding portion that is continuous in the longitudinal direction of the core wire is formed on the surface of the core wire, and any one of the core wires every predetermined length between the adjacent core wires in a twisted state. As a state in which the ridge portion is located, a portion where the interval between the core wires is widened by the intervention of the ridge portion is secured for each predetermined length, so that water attached to the surface of the core wire flows down from the core wire. In this case, some of the water flows down through the wide space between the core wires, and this water can wash away the dust in the gaps between the core wires, so that the dust can be separated from the core wires together with the water. It is hard to become a deposit on the surface of the core wire, can improve tracking resistance and prevent the formation of a conductive path on the surface of the core wire due to the tracking phenomenon, and the risk of an arc short circuit and the accompanying ignition or disconnection accident Can be significantly reduced. Furthermore, by changing the number of ridges for each core wire and making the outer shape of each core wire different, the core wire can be easily identified visually or tactilely, even if the color is the same, It can be identified, and various operability with respect to the core wire such as conductor exposure, connection, laying, or phase confirmation during inspection can be greatly improved.

  Further, the low-voltage lead-in electric wire according to the present invention is a flat low-voltage lead-in electric wire obtained by integrating a plurality of insulated core wires in parallel and adjacent to each other with the same material as the insulator of the core wire. A bridge portion that integrally connects the matching core wires is provided, and openings are arranged at predetermined intervals in the longitudinal direction of the core wire in the bridge portion.

  As described above, in the present invention, an opening is provided in the bridge portion between the parallel core wires, and a hole through which water or the like can pass is secured between the core wires for each predetermined length. When the water adhering to the surface flows down from the core wire, a part of it flows through the opening of the bridge part, and this water can wash away the dust attached to the gap between the core wires. It can be separated from the wire, and it is difficult for dust to adhere to the surface of the core wire, and it can improve tracking resistance and prevent the formation of a conductive path on the surface of the core wire due to tracking phenomenon. And the risk of breakage accidents can be significantly reduced.

  Moreover, the low-voltage lead-in electric wire according to the present invention forms the insulator of the core wire with a material in which a metal hydroxide is blended in a predetermined ratio at least with an olefin-based or rubber-based base resin.

  As described above, in the present invention, an olefin-based or rubber-based resin is used as an insulator, and a metal hydroxide is blended therein to provide high insulation performance, thereby improving tracking resistance and improving the surface resistance. The formation of the conductive path can be prevented, and even if the insulator is scratched or cracked, the risk of arc discharge between the exposed portions of the conductor is low, and it is possible to make it difficult to cause an ignition or disconnection accident. Furthermore, even if the insulator is burnt, the crystal water of the metal hydroxide is ejected, exerting a fire extinguishing action that takes away the generated Joule heat and dissipates it to the surroundings, making the insulator difficult to burn, and ejecting crystal water It is possible to prevent the progress of the tracking phenomenon by suppressing the growth of the carbide that becomes the conductive path by blowing away the carbide with the momentum of the evaporation gas.

  Moreover, the low-voltage lead-in electric wire according to the present invention forms the insulator of the core wire with a material in which at least a metal hydroxide is blended in a predetermined ratio with an olefin base resin containing high-density polyethylene as necessary. .

  As described above, in the present invention, an olefin-based resin containing high-density polyethylene is used as an insulator, and a metal hydroxide is blended therein to provide high insulation performance, while being resistant to wear and scratches. By making it an excellent insulator, in addition to improving tracking resistance, it is difficult to cause scratches on the surface that tend to get wet and dust, and it is difficult to cause discharge, and it is also a factor that leads to disconnection Scratches that reach one of the conductors are less likely to enter, and safety and reliability can be further improved. Furthermore, even if the insulator is burned, the crystal water of the metal hydroxide is ejected and given a fire extinguishing action that takes away the generated Joule heat and dissipates it to the surroundings, making the insulator difficult to burn and the ejected crystal water It is possible to prevent the progress of the tracking phenomenon by suppressing the growth of the carbide that becomes the conductive path by blowing away the carbide with the momentum of the evaporation gas.

(First embodiment of the present invention)
A first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a sectional view of a low-voltage lead-in electric wire according to the present embodiment, and FIG. 2 is a schematic perspective view of the low-voltage lead-in electric wire according to the present embodiment.

  In each of the drawings, the low-voltage lead-in wire 1 according to the present embodiment is formed by twisting three insulated core wires 11, 12, and 13 having a predetermined outer diameter R, and two of the core wires 12, 13 is formed by continuously forming a cross-sectional shape in which a plurality of protrusions 16 are arranged at equal intervals on the outer periphery of the core wire in the longitudinal direction, and the conductor centers of the core wires 11, 12, 13 are connected at the shortest distance. This is a configuration in which a predetermined distance d is secured between the positions of the outer surfaces of the core wires on the line.

  The core wires 11, 12, and 13 have a configuration in which an insulator 15 is coated on the outer side of the central conductor 14. One of the core wires 11, 12, and 13 (core wire 11) has a circular cross-sectional shape without protrusions, and the other core wires 12 and 13 have a circumferential angle range φ and the number of protrusions of each protrusion 16, respectively. It is a structure formed as a surface shape in which n is different from each other. The core wire 12 has a cross-sectional shape in which n = 4 projections 16 protruding at a predetermined height L from the outer diameter position over the circumferential angle range φ = 70 ° are arranged in the circumferential direction at equal intervals in the longitudinal direction. It is the structure formed. The core wire 13 has a cross-sectional shape in which n = 6 protrusions 16 protruding at a predetermined height L from the outer diameter position over the circumferential angle range φ = 30 ° are arranged at equal intervals in the circumferential direction of the surface, and is continuously arranged in the longitudinal direction. It is the structure formed.

In the twisted state of the cores 11, 12, and 13, the two adjacent cores are arranged so that one core is adjacent to the outer periphery of the other core at the position of the groove 17 between the protrusions 16. In addition, a predetermined distance d is generated between the outer positions of the core wires on the line connecting the centers of the conductors 14 of the core wires 11, 12, and 13 with the shortest distance. The distance d is set to 0.1 (mm) ≦ d ≦ R / 2, and the insulation creepage distance between the core wires 11, 12, 13 is larger than that of a simple circular cross-sectional shape. Note that the angular range θ of the circumferential direction of the groove 17 between the protrusions 16 is:
θ = 360 ° / n−φ
However, the possible range of the angle range θ of the groove 17 is
θ <2tan ⁻¹ [R {(3R / 2 + d) (R / 2 + d)} ^−1/2 / 2]
It becomes. Further, the height L of the protrusion 16 is determined using the circumferential angle range θ of the groove 17.
L = R [2- {1-3 tan ² (θ / 2)} ^1/2 ] {1 + tan ² (θ / 2)} ^−1/2 / 2-R / 2 + d / cos (θ / 2)
It is represented by

  The insulator 15 is obtained by blending a metal hydroxide with an olefin-based resin containing high-density polyethylene having excellent wear resistance and scratch resistance, and is difficult to cause scratches reaching the conductor 14 and leads to disconnection. In addition to being able to reduce, the property of having excellent tracking resistance as compared with the vinyl chloride resin provided in the olefin resin can further improve the reliability. Moreover, carbon black etc. are mix | blended with the insulator 15, and the weather resistance required when using it outdoors for a long term is ensured. Furthermore, this insulator 15 is recyclable by using a thermoplastic, non-crosslinked material, and does not generate harmful gas even if incinerated, in addition to having a small burden on the environment, Since the heat-resistant temperature is higher than that of vinyl chloride resin, it is possible to increase the allowable current and to reduce the wire size.

  The metal hydroxide blended in the insulator 15 is mainly magnesium hydroxide or aluminum hydroxide, and may be blended in combination of only one type or in combination of two or more types of metal hydroxides. The total blending ratio of the metal hydroxide is 50 to 180 parts by weight with respect to 100 parts by weight of the olefin base resin. When the blending ratio is less than 50 parts by weight, the flame retardancy and tracking resistance are lowered. When the blending ratio is more than 180 parts by weight, the insulation performance and mechanical properties are lowered.

  Such metal hydroxide causes the moisture contained in the metal hydroxide to evaporate by diffusing the heat contained in the metal hydroxide against the Joule heat generated by leakage current flowing through the surface of the insulator 15 and the heat generated by local discharge. In addition, it has the property of being decomposed by electric discharge or heat while dissipating carbides with the simultaneously generated gas to suppress the progress of the tracking phenomenon. The metal hydroxide also has the effect of making the insulator 15 difficult to burn, supplements the properties of olefin-based resins such as polyethylene that are easy to burn, and has sufficient flame retardancy as an insulating material for low-voltage lead-in wires drawn into houses. It can be secured.

  Next, the tracking phenomenon suppression state of the low-voltage lead-in wire based on the above configuration will be described. A predetermined interval is secured between the cores 11, 12, and 13 by projections 16 that are continuous in the longitudinal direction on the surface of the insulator 15 and arranged at a predetermined interval in the circumferential direction, and between adjacent cores Since the creepage distance of the insulation is large, the tracking resistance is high and the risk of arc short-circuiting is very small. However, if the insulator 15 surface is covered with dust or deposits containing moisture or salt, it is insulated. When the surface of the body 15 becomes wet or fouled, a leakage current flows along the surface of the insulator 15.

  When moisture partially evaporates due to Joule heat generated by this current, when a part of the surface of the insulator 15 is locally dried, the current path is interrupted and discharge is generated. However, when this heat is applied to the metal hydroxide contained in the insulator 15, the crystal water of the metal hydroxide is ejected and taken away to dissipate the surroundings, making the insulator 15 difficult to burn. Thus, the generation of carbides is suppressed, and the carbides are blown off and dissipated with the momentum of the evaporating gas of crystal water to suppress the growth of carbides that become conductive paths, thereby preventing the progress of the tracking phenomenon.

  On the other hand, these two or more twisted low-voltage lead wires require identification of the core wires for phase confirmation in inspection work, work that exposes conductors during installation, connection, etc. 1, the number of the protrusions 16 is different for each of the cores 11, 12, and 13 so that the cores can be identified based on the difference in the outer shape of the cores, and a desired core can be easily visually and tactilely sensed. You can identify and work. Even when black insulators containing carbon black are used for all the cores to ensure weather resistance, the cores can be identified without any problem.

  As described above, the low-voltage lead-in electric wire according to the present embodiment forms the surface of the insulator 15 of the two core wires 12 and 13 in a continuous state having a cross-sectional shape in which a plurality of protrusions 16 are provided at predetermined intervals in the circumferential direction. The core wire surface is provided with a continuous concavo-convex shape, and the adjacent core wires are twisted and adjacent to each other with the other outer surface adjacent to the groove 17 portion between the one protrusions 16 so that there is a space between the core wires. In addition, since the insulation creepage distance between the cores 11, 12, and 13 is set larger than that in the case of a simple circular cross-sectional shape, the tracking resistance can be improved, and the discharge caused by the tracking phenomenon and the insulator 15 associated therewith. Is less likely to cause carbon short-circuiting and hardly causes an arc short circuit due to scratches and cracks in the insulator 15 due to various factors, thereby reducing the risk of ignition and disconnection accidents and increasing reliability.

  In addition, in the low voltage | pressure lead-in electric wire which concerns on the said embodiment, it is set as the structure which provides the processus | protrusion 16 part which continues in a longitudinal direction on the surface of the insulator 15 of the core wires 12 and 13 by the circumferential direction predetermined space | interval. As shown in FIG. 3, one or a plurality of grooves 18 having an angle range δ smaller than the circumferential angle range φ of the protrusion 16 and a groove depth l smaller than the height L of the protrusion 16 are arranged in the protrusion 16 portion. It can also be configured to be continuously formed in the longitudinal direction of the core wire, and the insulation creepage distance in the core wire can be further increased, and the discharge caused by the tracking phenomenon and the carbonization of the insulator accompanying this are less likely to occur. The risk of arc shorting between exposed conductors can be eliminated, safety and reliability can be improved, and the presence of the small grooves 18 increases the identification of the cores, so that the cores can be handled during work. Mistakes are less likely to occur.

  Moreover, in the low voltage | pressure lead-in electric wire which concerns on the said embodiment, although it is set as the structure which forms the processus | protrusion 16 part on the surface of the insulator 15 of the core wires 12 and 13 as a protrusion shape continuous in a core wire longitudinal direction, it is not restricted to this. Alternatively, the protrusion 16 may be formed as an intermittent shape in which protrusions having a predetermined length are repeatedly arranged at predetermined intervals in the longitudinal direction of the core wire. Further, when the protrusions 16 are continuously formed in a ridge shape, a part of the continuous protrusions 16 are connected to other adjacent protrusions 16 for each predetermined length, and the portions between the protrusions 16 are not continuous grooves but at predetermined intervals. It can also be set as the shape by which a recessed part is arrange | positioned.

  Moreover, in the low voltage | pressure lead-in electric wire which concerns on the said embodiment, it is set as the structure which makes the number of protrusions and arrangement | positioning states differ between the core wires 11, 12, and 13, and can identify core wires by the difference in an external shape, In addition, it is possible to adopt a configuration in which identification can be made by adding a color band for identification in the longitudinal direction of the insulator 15 or marking on the surface of the insulator 15. Further, as an identification method other than the above, in order to identify by the color of the insulator 15, a configuration may be adopted in which a colored insulating material having two or more insulators 15 and colored in the outermost layer to improve the weather resistance is applied.

(Second embodiment of the present invention)
A second embodiment of the present invention will be described with reference to FIGS. FIG. 4 is a sectional view of the low-voltage lead-in electric wire according to the present embodiment, and FIG. 5 is a side view of the low-voltage lead-in electric wire according to the present embodiment.

  In each of the drawings, the low-voltage lead-in electric wire 2 according to the present embodiment is formed by twisting three insulated core wires 21, 22, and 23 each consisting of a conductor 24 and an insulator 25. , 23 are one or a plurality of parallel states in which the core wires are engaged with each other at two substantially spiral continuous portions closest to each other in the twisted state with the other two core wires on the outer peripheral surface of each core wire. The protrusions 26 are respectively formed, and the number of the protrusions 26 is different for each of the core wires 21, 22, and 23.

Of the three core wires 21, 22, and 23, the core wire 21 has a configuration in which two ridges 26 that are substantially spirally arranged in a row are formed at predetermined intervals in the circumferential direction. The core wire 22 has a configuration in which the ridges 26 that are continuous in one row and the ridges 26 that are continuous in a two-row parallel state are formed at predetermined intervals in the circumferential direction. Furthermore, the core wire 23 is configured such that two sets of protruding ridge portions 26 that are continuous in a two-row parallel state are formed at predetermined intervals in the circumferential direction. A groove 27 is formed between the ridges 26 arranged in parallel in two rows, and this is a mechanism for engaging one row of ridges 26 in other core wires, and each of the core wires 21, 22, In the twisted state 23, the protrusions 26 and the grooves 27 are engaged with each other, and the distance between the core wires is kept constant.
The composition of the insulator 25 is the same as that of the first embodiment, and a description thereof will be omitted.

  Next, the tracking phenomenon suppression state of the low voltage lead-in wire according to the present embodiment will be described. A predetermined interval is secured between the core wires 21, 22, 23 by the protrusions 26 that are continuously engaged with each other in a substantially spiral shape on the surface of the insulator 25, and insulation between the adjacent core wires 21, 22, 23 is achieved. Since the creepage distance is large, the tracking resistance is high, and the risk of arc short-circuiting is extremely small. Also, as in the first embodiment, the insulator 25 is made of olefin base resin with metal hydroxide. Even if dust containing moisture or salt adheres or accumulates on the cable surface and the surface of the insulator 25 is wetted or fouled, and a leakage current flows along the surface of the insulator 25, the conductive path The progress of the tracking phenomenon can be prevented by suppressing the formation and growth of carbides.

  As described above, the low-voltage lead-in electric wire according to the present embodiment forms the ridge portion 26 at the substantially spiral portion of the surface of each of the core wires 21, 22, and 23, which is a portion close to the other core wire in the twisted state of the core wires. Then, the protrusions 26 are engaged with each other between the core wires, and are twisted and integrated while securing a certain distance between the core wires 21, 22, and 23, and the insulation creepage distance between the core wires is reduced to a simple circle. Since the cross-sectional shape is larger than that in the case of the cross-sectional shape, the tracking resistance is improved, and the discharge caused by the tracking phenomenon and the carbonization of the insulator 25 are less likely to occur. There is almost no connection from cracks to arc shorts, reducing the risk of fire and disconnection accidents and increasing reliability. Furthermore, by changing the number of the ridges 26 for each of the core wires 21, 22, 23 and making the outer shapes of the core wires 21, 22, 23 different, it becomes possible to easily identify the core wires by visual or tactile sensation, Even if the colors are the same, the core wire can be reliably identified, and various operability for the core wire such as conductor exposure, connection, laying, or phase check during inspection can be greatly improved.

(Third embodiment of the present invention)
A third embodiment of the present invention will be described with reference to FIGS. FIG. 6 is a cross-sectional view of the low-voltage lead-in electric wire according to the present embodiment. 7 is a side view of the low-voltage lead-in electric wire according to the present embodiment, and FIG. 8 is a cross-sectional view of each of AA, BB, and CC in FIG.

  In each of the drawings, the low-voltage lead-in electric wire 3 according to the present embodiment is a low-voltage lead-in electric wire formed by twisting and integrating three insulated core wires 31, 32, 33 each composed of a conductor 34 and an insulator 35. The protrusions 36 of the core wires 32, 33 are formed between the adjacent core wires 31, 32, 33 in a twisted state by forming the protrusions 36 continuous in the longitudinal direction of the core wires on the surfaces of the two core wires 32, 33. While the part 36 is positioned at a predetermined interval based on the twisting pitch, the number of the protrusions 36 is different for each of the core wires 32 and 33.

Of the three core wires 31, 32, 33, the core wire 31 is configured to have a general circular cross-sectional shape without protrusions. Moreover, the core wire 32 is a structure in which one continuous protrusion 36 is formed. Furthermore, the core wire 33 has a configuration in which two continuous protrusions 36 are formed at positions symmetrical with respect to the center of the core wire. When the cores 31, 32, and 33 are twisted together, the protrusions 36 are interposed at predetermined intervals in the longitudinal direction between the respective cores, and the interval between the adjacent cores is increased at the protrusion 36 intervening portion. It is a mechanism to do.
The composition of the insulator 35 is the same as that of the first embodiment, and a description thereof will be omitted.

  Next, the tracking phenomenon suppression state of the low voltage lead-in wire according to the present embodiment will be described. The protrusions 36 that are continuous in the longitudinal direction on the surface of the insulator 35 are interposed between the core wires 31, 32, and 33 at predetermined lengths in a twisted state. A gap is secured at each of the 36 interpositions, and a part of the water adhering to the surface of the core wire can flow down there, and the dust attached to the surface of the core wire is washed away by this flowing water and is not directly deposited on the surface. A state is obtained. In this way, it is possible to prevent the surface of the insulator 35 from being wetted or soiled and shifting to a state in which a leakage current flows along the surface of the insulator 35. In addition to the fact that the insulation creepage distance between the adjacent core wires 31, 32, 33 is increased, the insulator 35 is blended with an olefin base resin and a metal hydroxide as in the first embodiment. It has high tracking resistance, and even if the surface of the insulator 35 is wet or fouled and leakage current flows along the surface of the insulator 35, the generation and growth of carbide that becomes a conductive path is suppressed and the tracking phenomenon is suppressed. Progress can be prevented and the risk of arc short-circuit is very small.

  As described above, the low-voltage lead-in electric wire according to the present embodiment forms the protrusions 36 continuous in the longitudinal direction of the core wires on the surfaces of the core wires 32 and 33, and between the adjacent core wires and the core wires in the twisted state. As a state in which the protruding portion 36 of any one of the core wires is positioned for each predetermined length, a portion where the interval between the core wires is widened with the intervention of the protruding portion 36 is ensured for each predetermined length. When water adhering to the surfaces of the core wires 31, 32, and 33 flows down from the core wires, a part of the water flows through a wide portion between the core wires, and this water can wash away dust attached to the gap between the core wires. As a result, dust can be separated from the cores 31, 32, and 33 together with water, and the dust is less likely to adhere as deposits on the surfaces of the cores 31, 32, and 33. Prevents the formation of a conductive path on the core surface, The risk occurs of fire or accidental disconnection due to this can be significantly reduced. Also, by changing the number of the protrusions 36 for each core wire and making the outer shapes of the core wires 31, 32, 33 different, the core wires can be easily identified visually or tactilely, and the colors are the same However, the cores 31, 32, and 33 can be reliably identified, and various operability of the cores such as exposure of the conductor 34, connection, laying, or phase check during inspection can be greatly improved.

(Fourth embodiment of the present invention)
A fourth embodiment of the present invention will be described with reference to FIG. FIG. 9 is a schematic perspective view of the low-voltage lead-in electric wire according to the present embodiment.
In FIG. 9, the low-voltage lead-in wire 1 according to the present embodiment is obtained by integrating three insulating core wires 41, 42, and 43 each made up of a conductor 44 and an insulator 45 into a flat shape, Between each core wire, it is provided with a bridge portion 46 that integrally connects the adjacent core wires with the same material as the insulator 45, and the opening portions 47 are arranged in the bridge portion 46 at predetermined intervals in the longitudinal direction of the core wire. is there.
The composition of the insulator 45 is the same as that of the first embodiment, and a description thereof will be omitted.

  Next, the tracking phenomenon suppression state of the low voltage lead-in wire according to the present embodiment will be described. Openings 47 are secured at predetermined intervals in the longitudinal direction between the core wires 41, 42, 43, and a part of the water adhering to the core wire surface can flow down through the openings 47, and the core surface The state where the dust attached to the surface is washed away and is not directly deposited on the surface can be obtained. In this way, it is possible to suppress the surface of the insulator 45 from being wetted or soiled and shifting to a state where a leakage current flows along the surface of the insulator 45. Further, as in the first embodiment, the insulator 45 is a mixture of an olefin-based resin and a metal hydroxide, and the surface of the insulator 45 is wet or fouled and leaks along the surface of the insulator 45. Even when a current flows, it is possible to prevent the progress of the tracking phenomenon by suppressing the generation and growth of carbides that become conductive paths.

  As described above, the low-voltage lead-in electric wire according to the present embodiment is provided with the opening 47 in the bridge portion 46 between the core wires 41, 42, and 43 so that water or the like can pass between the core wires every predetermined length. Since the hole is secured, when the water adhering to the surface of the core wires 41, 42, 43 flows down from the core wire, a part of the water flows down through the opening 47 of the bridge portion 46, and the core wire 41, Dust in the gap between 42 and 43 can be washed away, and the dust can be separated from the core wire together with water, making it difficult for the dust to adhere to the surface of the core wire as a deposit, and tracking with improved tracking resistance. It is possible to prevent the formation of a conductive path on the surface of the core wire due to the phenomenon, and to significantly reduce the risk of an arc short circuit and the accompanying ignition or disconnection accident.

  The low-voltage lead-in wires according to the first to fourth embodiments have a configuration in which the number of cores is three, but this is not restrictive, and a predetermined number of cores are appropriately twisted. It can also be set as the structure used as a low voltage | pressure lead-in electric wire, uniting together or carrying out a predetermined number in parallel.

The evaluation result which compared the low-voltage lead-in electric wire which concerns on this invention about the low-voltage lead-in electric wire similar to the past, tracking resistance, etc. is demonstrated.
For three examples with different structures of the low-voltage lead-in electric wire according to the present invention, electric wires were actually manufactured, and the tracking resistance was compared with the conventional products. As a first example, a two-core stranded low-voltage lead-in electric wire formed by twisting one of the two core wires formed with a continuous ridge portion in the longitudinal direction was used. In addition, as a second embodiment, one row or two that engage each other between the core wires at the substantially spiral continuous portion closest to each other in the twisted state with the other core wires on the outer peripheral surfaces of the two core wires. A two-core stranded low-voltage lead-in electric wire in which ridge portions in a column parallel state were formed and the core wires were twisted while engaging the ridge portions with each other was used. Furthermore, as a third embodiment, a two-core flat low-voltage lead-in electric wire having an opening at the bridge portion between the core wires was used.

  Further, as a first comparative example, a two-core twisted conventional low-voltage lead-in wire was used, and as a second comparative example, a two-core flat-shaped conventional low-voltage lead-in wire was used. In addition, each of the low-voltage lead-in electric wires of the example and the comparative example is a two-core low-voltage lead-in wire using two core wires in which a hard copper wire having a diameter of 2.6 mm serving as a conductor is coated with a 1 mm-thick insulator. It is an electric wire.

A comparative test for tracking resistance was performed on each sample of each of the examples and comparative examples. As for tracking resistance, since it is necessary to simulate the phenomenon from the actual start of the tracking phenomenon to the disconnection, the upper surface of the insulator of the 2-core wire was scraped off at the same location of the 2-core wire with a knife or the like. A flaw simulating the crack of the part and the insulator was made, and the test solution was sprayed in a state where AC 200 V was applied between the two core wires, and the tracking generation time and the elapsed time until disconnection were examined. In addition, when it did not disconnect even if 100 hours passed, the test was complete | finished at that time. Since the test liquid has adhesion of salt and dust in the field, the liquid specified in the tracking resistance test of JIS C 3005 is equivalent to the fouling liquid specified in the JCAA B001 fouling flash test. What mixed powder (The liquid which mixed 40 g of powders with 2 g of sodium chloride and 1 ml of polyoxyethylene nonylphenyl ether in 1 l of water) was used. In addition, spraying was performed as appropriate with reference to the degree to which the surface of the evaluation portion of each sample can be kept wet as a spraying condition.
Table 1 shows the results of the comparative test conducted as described above.

  From Table 1 above, although tracking occurred immediately after the start of the test for each sample of each example and comparative example, the first to third examples were broken even after 100 hours. Thus, it can be seen that sufficient disconnection prevention performance is obtained due to structural features.

  Subsequently, for two different examples of the insulator material of the low-voltage lead-in electric wire according to the present invention, an electric wire was actually manufactured and each characteristic was compared with the conventional product. As a fourth example, a low-voltage lead-in electric wire having an insulator made of a material in which 70 parts by weight of magnesium hydroxide and aluminum hydroxide were combined with 100 parts by weight of an olefin base resin was used. Further, as a fifth embodiment, 70 parts by weight of 100 parts by weight of the olefin-based resin is made of high-density polyethylene, and a low-pressure lead in which an insulator is made of a material containing a total of 70 parts by weight of magnesium hydroxide and aluminum hydroxide. Electric wires were used. Further, as a third comparative example, a low-voltage lead-in wire using a conventional polyvinyl chloride resin as an insulator was used. Note that each of the low-voltage lead-in wires in each of the above-described examples and comparative examples has two cores in which two core wires formed by coating a hard copper wire having a diameter of 2.6 mm serving as a conductor with an insulator having a thickness of 1 mm are twisted together. Is a low-voltage lead-in wire.

  About each sample of each said Example and a comparative example, the abrasion resistance, damage resistance, tracking resistance, and the flame retardance comparison test were done. Each test method is shown below. First, regarding the wear resistance, the number of revolutions until the conductor appeared was examined with a load of 3 kg based on the wear test of JIS-C-3005.

  For scratch resistance, set the wire above the wire in a state where the wire is tilted 45 ° from the horizontal and a load of 5 kg is attached to the top or side of the 1 mm thick steel plate so that the iron plate can pierce the wire surface. Then, the height at which the iron plate was dropped was changed with reference to the position in contact with the electric wire, and the strength of the impact (energy) at which the scratch reaching the conductor entered was examined.

The tracking resistance is examined in the same manner as in the comparative tests of the first to third embodiments with different structures, and the description is omitted. Moreover, about the flame retardance, the test based on the 60 degree inclination test of a JIS-C-3005 flame retardance test was implemented and investigated.
Table 2 shows the results of the comparative tests conducted in the manner described above.

  From Table 2, it can be seen that the low-voltage lead-in wire in the fifth example is extremely superior to other examples in terms of wear resistance and scratch resistance. As for tracking resistance, the comparative example generates a tracking phenomenon immediately after the start of the test, whereas in the fourth and fifth examples, tracking does not occur and disconnection occurs even after 100 hours. It turns out that it has sufficient tracking resistance. On the other hand, regarding the flame retardancy, it can be seen that all samples have sufficient self-digestibility.

  As a result, in the low-voltage lead-in wire, the twisted type is provided with a protrusion on the core wire, and the flat type is provided with an opening in the bridge portion between the core wires, so that disconnection based on tracking is unlikely to occur. It was confirmed that In addition, it was confirmed that excellent tracking resistance can be obtained by using an olefin base resin blended with a metal hydroxide as an insulator material. Furthermore, it has been confirmed that excellent wear resistance and scratch resistance can be obtained when an olefin base resin containing high density polyethylene is used.

It is sectional drawing of the low voltage | pressure lead-in electric wire which concerns on the 1st Embodiment of this invention. It is a schematic perspective view of the low voltage | pressure lead-in electric wire which concerns on the 1st Embodiment of this invention. It is sectional drawing of the other low voltage | pressure lead-in electric wire which concerns on the 1st Embodiment of this invention. It is sectional drawing of the low voltage | pressure lead-in electric wire which concerns on the 2nd Embodiment of this invention. It is a side view of the low voltage | pressure lead-in electric wire which concerns on the 2nd Embodiment of this invention. It is sectional drawing of the low voltage | pressure lead-in electric wire which concerns on the 3rd Embodiment of this invention. It is a side view of the low voltage | pressure lead-in electric wire which concerns on the 3rd Embodiment of this invention. FIG. 8 is a cross-sectional view of each of AA, BB, and CC in FIG. 7. It is a schematic perspective view of the low voltage | pressure lead-in electric wire which concerns on the 4th Embodiment of this invention.

Explanation of symbols

1, 2, 3, 4 Low voltage lead-in wire 11, 12, 13 Core wire 14 Conductor 15 Insulator 16 Protrusion 17 Groove 18 Groove 21, 22, 23 Core wire 24 Conductor 25 Insulator 26 Projection portion 27 Groove portion 31, 32, 33 Core wire 34 Conductor 35 Insulator 36 Projection portion 41, 42, 43 Core wire 44 Conductor 45 Insulator 46 Bridge portion 47 Opening portion

Claims (8)

In a low-voltage lead-in electric wire formed by twisting a plurality of insulated core wires,
Among the core wires having a predetermined outer diameter R, at least one core wire has n protrusions having a height L from the outer diameter position at equal intervals in the surface circumferential direction over the surface circumferential angle range φ. The cross-sectional shape is continuously formed in the longitudinal direction of the core wire, or at least a predetermined length of the continuous shape portion is repeatedly arranged at predetermined intervals in the longitudinal direction of the core wire,
Two adjacent core wires in a twisted state are adjacent to the outer periphery of the other core wire at the groove position between the protruding portions of one core wire,
A low-voltage lead-in electric wire characterized in that an interval d between the outer surface positions of the core wires on a line connecting the conductor centers of the core wires with the shortest distance is 0.1 (mm) ≦ d ≦ R / 2. In the low-voltage lead-in electric wire according to claim 1,
Any one of the cores has a circular cross-sectional shape without protrusions,
When there are a plurality of other core wires, the low-voltage lead-in wire is formed as a cross-sectional shape in which the number n of each protrusion and / or the circumferential angle range φ of the protrusions are different from each other. In the low-voltage lead-in electric wire according to claim 1 or 2,
At least one of the cores has a groove width in an angle range δ smaller than the circumferential angle range φ of the protrusion and a groove depth smaller than a height L from the outer diameter position of the protrusion on at least one surface of the protrusion portion. A low-voltage lead-in electric wire, characterized in that one or a plurality of grooves to be l are formed continuously in the longitudinal direction of the core wire in a parallel state. In a low-voltage lead-in electric wire formed by twisting a plurality of insulated core wires,
One or a plurality of parallel spiral protrusions that engage each other between the core wires at one or more substantially spiral continuous portions closest to each other in a twisted state on the outer peripheral surface of each core wire A low-voltage lead-in electric wire characterized in that, when each ridge is formed on each of a plurality of core wires, the number of the ridges is different for each core wire. . In a low-voltage lead-in electric wire formed by twisting a plurality of insulated core wires,
One or a plurality of ridges continuous in the longitudinal direction are formed on the surface of at least one core wire, and at least one of the core wires is twisted between adjacent core wires in a twisted state. The low voltage lead-in electric wire is characterized in that, when the protrusions are arranged on a plurality of core wires, the number of the protrusions is different for each core wire. . In a flat low-voltage lead-in wire that is made by integrating a plurality of insulated core wires in parallel,
Between each core wire, comprising a bridge portion that integrally connects adjacent core wires with the same material as the insulator of the core wire,
An opening is arranged at predetermined intervals in the longitudinal direction of the core wire in the bridge portion. In the low-voltage lead-in electric wire according to any one of claims 1 to 6,
A low-voltage lead-in electric wire, wherein the insulator of the core wire is formed of a material in which a metal hydroxide is blended at a predetermined ratio with at least an olefin-based or rubber-based resin. In the low-voltage lead-in electric wire according to any one of claims 1 to 6,
A low-voltage lead-in electric wire, characterized in that the insulator of the core wire is formed of a material in which at least a metal hydroxide is blended in a predetermined ratio with an olefin base resin containing high-density polyethylene.