JP2015141829A - power cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power cable in which out growth can be suppressed with a simple structure.SOLUTION: Provided is a power cable comprising: a first cable part; and a second cable part connected to the first cable part along an axial direction. The first cable part includes a first conductive part, and the second cable part includes: a second conductive part composed of the material same as that of the first conductive part; and a wire rod provided along an axial direction in the second conductive part and composed of a material having a higher Young's modulus and a lower linear expansion coefficient than the material composing the second conductive part.

Description

  The present invention relates to a power cable.

  The power cable includes, for example, a conductive portion, an insulating layer that covers the outer periphery of the conductive portion, and a coating layer that covers the outer periphery of the insulating layer. Such a power cable is used as, for example, an underground transmission line for high-voltage power, and is laid in a limited space such as in a pipeline. When power is supplied to the conductive portion, the power cable extends in the axial direction due to thermal expansion and contraction. The extension that cannot be absorbed in the restricted space in the pipeline is absorbed by the bent deformation portion (offset portion) of the power cable provided in the manhole.

  Further, when there is an inclination or the like in the pipeline, the power cable may slide down due to this thermal expansion and contraction. Such slipping is greatly influenced not only by the mass, length, and temperature change of the power cable, but also by the linear expansion coefficient. If the region where the temperature change is large and the thermal expansion and contraction does not occur, that is, the immovable region disappears, the power cable slides down. For this reason, an anti-skid device or the like that holds the power cable using a spring or weight may be attached to the power cable.

  Here, the extension length (extension amount) of the power cable is a cross-linked polyethylene insulated vinyl sheath cable that has become the mainstream nowadays compared to the oil-filled paper insulated power cable (OF cable: Oil Filled Cable) that has been used conventionally. (Crosslinked polyethylene insulated PVC sheathed cable: CV cable) is longer.

  For this reason, for example, when there is a change in the system of an existing line where an OF cable has been used, or when there is a reason for renewal such as an accident response or aged disposal, there is room to absorb the extension length of the CV cable in the manhole size, etc. There may not be. In such a case, the actual situation is that it has to be updated with an OF cable as before.

  Thus, for example, Patent Document 1 discloses a power cable in which a linear body is spirally wound around the periphery of a power cable body and snake-like deformation is assisted along the winding of the linear body. Patent Document 1 describes that the deformation to the snake shape suppresses the extension in the axial direction and suppresses the extension from the pipeline to the manhole.

  For example, Patent Document 2 discloses a power cable in which a segment constituting a copper conductor or a part of a stranded wire is combined with another conductor having a bending rigidity different from that of the copper conductor, such as aluminum. According to Patent Document 2, in such a power cable, the conductor is deformed in a spiral shape as the temperature rises due to energization, so that the extension in the axial direction is suppressed, and the extension from the pipeline into the human hole is suppressed. It is described.

Japanese Patent Laid-Open No. 03-102713 Japanese Patent Laid-Open No. 02-139806

  However, as in Patent Document 1, for example, there is a possibility that the snake shape is not easily formed only by winding a linear body around the power cable body. For this reason, complicated additional measures such as applying tension to the linear body or forming the linear body so as to periodically have a thick portion and a thin portion in the length direction may be required. In addition, since a part of the outer shape is spiral and the cross section of the power cable is not circular, cable processing and laying may be difficult.

  For example, as in Patent Document 2, if a material such as aluminum having a different electrical resistance from the copper conductor is used for a segment or a part of the stranded wire, the electrical resistance as a whole may be increased.

  In addition, as described above, if a slip prevention device using a spring or a weight is attached to the power cable in order to suppress slipping of the power cable due to an inclination in the pipeline, the size of the human hole may increase. There is.

  The objective of this invention is providing the electric power cable which can suppress extension by a simple structure.

According to a first aspect of the invention,
A first cable portion;
A second cable portion connected to the first cable portion along the axial direction;
With
The first cable part has a first conductive part,
The second cable portion is
A second conductive portion made of the same material as the first conductive portion;
A wire rod made of a material provided in the second conductive portion along the axial direction and having a Young's modulus larger than that of the material constituting the second conductive portion and a small linear expansion coefficient;
A power cable is provided.

According to a second aspect of the invention,
The pipe length is L, the Young's modulus of the first cable part is E, the area of the first conductive part of the first cable part is A, the linear expansion coefficient of the first cable part is α ₁ , and the inside of the pipe line The length of the second cable portion laid in the axial direction is L ₂ , the linear expansion coefficient of the second cable portion is α ₂ , the friction coefficient is μ, the unit weight of the first cable is W, the temperature change width T, and the ratio of the extension length to the extension length of the power cable not including the wire rod is equal to or less than a predetermined ratio r ₀ (%), the second cable portion laid in the pipe line the length L ₂ in the axial direction, the power cable according to the first aspect is provided which satisfies the equation (1) below.

According to a third aspect of the invention,
The line length is L, the linear expansion coefficient of the first cable part is α ₁ , the axial length of the second cable part installed in the pipe line is L ₂ , and the linear expansion of the second cable part When the coefficient is α ₂ and the ratio of the extension length to the extension length of the power cable not including the wire is not more than a predetermined ratio r ₀ (%), the second cable laid in the pipe line axial length L ₂ of the parts are the power cable according to the first or second aspect satisfies the following formula (2) is provided.

According to a fourth aspect of the invention,
Wherein the predetermined ratio r ₀ is provided a power cable according to the second or third aspect is 96%.

According to a fifth aspect of the present invention,
When the pipe length is 300 m, the linear expansion coefficient of the first cable part is 20 × 10 ⁻⁶ / ° C., and the linear expansion coefficient of the second cable part is 12 × 10 ⁻⁶ / ° C., The power cable according to any one of the first to fourth aspects is provided, in which the second cable portion laid on the shaft has an axial length of 24 m or more.

According to a sixth aspect of the present invention,
The second cable part has a hollow part provided in a central part of the second conductive part and extending in an axial direction of the second conductive part,
As for the said wire, the electric power cable in any one of the 1st-5th aspect inserted in the said hollow part is provided.

According to a seventh aspect of the present invention,
The power cable according to any one of the first to sixth aspects is provided in which at least a part of an outer surface of the wire rod is in contact with the second conductive portion.

According to an eighth aspect of the present invention,
The power cable according to any one of the first to seventh aspects is provided in which the second cable portion is disposed on both ends of a pipeline with the first cable portion interposed therebetween.

According to a ninth aspect of the present invention,
The power cable according to any one of the first to eighth aspects, in which at least a part of the second conductive portion is in a meandering state when energizing the first conductive portion and the second conductive portion. .

According to a tenth aspect of the present invention,
The first conductive part and the second conductive part are copper conductors,
The power cable according to any one of the first to ninth aspects, wherein the wire is an invar wire.

  ADVANTAGE OF THE INVENTION According to this invention, the electric power cable which can reduce the amount of extension with a simple structure is provided.

It is a schematic diagram which shows the state of the installation of the power cable which concerns on one Embodiment of this invention. (A) is sectional drawing orthogonal to the axial direction of the 1st cable part of the power cable which concerns on one Embodiment of this invention, (b) is the 2nd cable of the power cable which concerns on one Embodiment of this invention. It is sectional drawing orthogonal to the axial direction of a part. It is a stress-distance distribution figure in case a power cable is comprised only by the 1st cable part. It is a stress-distance distribution figure in the electric power cable which concerns on one Embodiment of this invention. It is a figure which shows the extension length ratio with respect to the length of the axial direction of a 2nd cable part. It is a figure which shows the length of the axial direction of the 2nd cable part with respect to the linear expansion coefficient of a 2nd cable part when an extension length ratio will be 96%.

<One Embodiment of the Present Invention>
(1) Structure of power cable A power cable according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a cross-sectional view orthogonal to the axial direction of the power cable 1 according to the present embodiment. Fig.2 (a) is sectional drawing orthogonal to the axial direction of the 1st cable part of the power cable which concerns on this embodiment, FIG.2 (b) is the 2nd cable part of the power cable which concerns on this embodiment. It is sectional drawing orthogonal to an axial direction.

  The power cable 1 of the present embodiment includes a first cable portion 10 and a second cable portion 20 that is connected to the first cable portion 10 along the axial direction and has a smaller linear expansion coefficient than the linear expansion coefficient of the first cable portion 10. And comprising. Details will be described below.

(overall structure)
As shown in FIG. 1, the power cable 1 is a power cable for underground transmission, and is laid in, for example, an underground conduit 920. The power cables 1 adjacent in the axial direction are connected by a cable connecting portion (connection box) 30 provided in a manhole 940. The cable connecting portion 30 is, for example, a one-piece type rubber unit.

  In addition, the power cable 1 is installed in a state bent in an S shape between the opening of the conduit 920 and the cable connection portion 30. This bent portion is referred to as “offset portion 40”. When the power cable 1 thermally expands and contracts, the offset portion 40 is deformed to absorb the expansion and contraction of the power cable 1. Note that the curvature radius of the offset portion 40 is set based on the extension length of the power cable 1 from the pipe 920 that is expected when the power cable 1 extends, and the human hole 940 is set based on the curvature radius of the offset portion 40. The axial length of is set.

  The power cable 1 according to this embodiment includes two types of cable parts (first cable part 10 and second cable part 20). The 1st cable part 10 and the 2nd cable part 20 are provided between the two adjacent cable connection parts 30, and are mutually connected along an axial direction. For example, the second cable part 20 is arranged symmetrically with the first cable part 10 sandwiched between the both ends of the conduit 920. The second cable portion 20 is connected to the cable connecting portion 30 in a state where the offset portion 40 is formed at the portion exiting from the conduit 920.

  Here, the Young's modulus of the second cable part 20 is larger than the Young's modulus of the first cable part 10, and the linear expansion coefficient of the second cable part 20 is smaller than the linear expansion coefficient of the first cable part 10. Thereby, extension of the 2nd cable part 20 among electric power cables 1 is controlled. Details of the arrangement of the first cable portion 10 and the second cable portion 20 will be described later.

(First cable part)
As shown in FIG. 2A, the first cable portion 10 of the power cable 1 is configured as a cross-linked polyethylene insulated PVC sheathed cable (CV cable). Specifically, the first cable part 10 includes, for example, a first conductive part 110, a first binder 130, a first internal semiconductive layer 140, a first insulating layer 150, a first external part from the center side to the outside. A semiconductive layer 160, a first shielding layer 172, a first pressing tape 174, a first water shielding layer 176, and a first sheath (covering layer) 180 are provided.

  The first conductive portion 110 includes a plurality of segments 110s made of, for example, pure copper (C) or a copper alloy and having a cross-sectional shape such as a trapezoid or a sector. Here, for example, the first conductive portion 110 includes six segments 110s having a fan-shaped cross section. Each segment 110s may be formed by twisting a plurality of strands made of pure copper or copper alloy. Each segment 110s may have a plurality of layers from the inside to the outside.

  A first binder 130 made of metal tape and insulating paper such as kraft paper is provided on the outer periphery of the first conductive portion 110. Part of the insulating paper constituting the first binder 130 is also inserted between the segments 110 s of the first conductive unit 110.

  In addition, for example, the first internal semiconductive layer 140 is made of a semiconductive resin composition containing an ethylene-vinyl acetate copolymer and the like and a conductivity imparting agent such as carbon black. The first insulating layer 150 is made of crosslinked polyethylene. The first external semiconductive layer 160 is made of the same semiconductive resin composition as the first internal semiconductive layer 140. The first shielding layer 172 is configured by combining an annealed copper wire. The first pressing tape 174 is made of a non-woven tape, a polyester tape or the like when there is no water shielding layer, and a semiconductive tape when there is a water shielding layer. The water shielding layer 176 is made of an aluminum laminate tape or the like. The first sheath 180 is made of vinyl chloride.

(Second cable part)
As shown in FIG. 2B, the second cable portion 20 of the power cable 1 is configured as a CV cable having a linear expansion coefficient smaller than that of the first cable portion 10. Specifically, the second cable portion 20 includes, for example, a second conductive portion 210 including a wire 220 having a small linear expansion coefficient, a second binder 230, a second internal semiconductive layer 240, from the center side to the outside. A second insulating layer 250, a second external semiconductive layer 260, a second shielding layer 272, a second pressing tape 274, a second water shielding layer 276, and a second sheath (covering layer) 280 are provided.

  The second conductive unit 210 is made of the same material as the first conductive unit 110, for example. For example, the second conductive unit 210 includes a plurality of segments 210s having a sector or sector shape in cross section. In addition, the second conductive unit 210 is connected to the first conductive unit 110 without a break, and the diameter of the second conductive unit 210 is equal to the diameter of the first conductive unit 110.

  In addition, a hollow portion 210 w extending in the axial direction of the second conductive portion 210 is provided in the center portion of the second conductive portion 210. The wire 220 is inserted into the hollow part 210w of the second conductive part 210. The wire 220 is provided along the axial direction of the second conductive portion 210 by being inserted into the hollow portion 210 w of the second conductive portion 210. The innermost diameter of the hollow part 210w is equal to the diameter of the wire 220. Thereby, the wire 220 is inserted in a dense state in the hollow portion 210w, and at least a part of the outer surface of the wire 220 is in contact with the inner wall of the second conductive portion 210.

The wire 220 is made of, for example, a material having a Young's modulus larger than that of the material constituting the second conductive portion 210 (and the first conductive portion 110) and a small linear expansion coefficient. Specifically, the wire 220 contains iron (Fe) and nickel (Ni) at a predetermined ratio, and is, for example, an invar wire. For example, the wire 220 is configured by a single invar wire or by twisting a plurality of invar wires. In addition, the Young's modulus of copper used for the second conductive portion 210 is 3 × 10 ³ kgf / mm ² , and the linear expansion coefficient is 20 × 10 ⁻⁶ / ° C., while the invar used for the wire 220 is The Young's modulus is 16.5 × 10 ³ kgf / mm ² and the linear expansion coefficient is 3 × 10 ⁻⁶ / ° C. Note that the composition ratio of Fe: Ni in Invar is 63.5: 36.5.

  In addition, the second binder 230, the second inner semiconductive layer 240, the second insulating layer 250, the second outer semiconductive layer 260, the second shielding layer 272, the second pressing tape 274, and the second shielding shield in the second cable portion 20. The water layer 276 and the second sheath 280 are respectively the first binder 130, the first inner semiconductive layer 140, the first insulating layer 150, the first outer semiconductive layer 160, and the first shielding layer 172 in the first cable portion 10. The first pressing tape 174, the first water shielding layer 176, and the first sheath 180 are made of the same material. Further, the portions of the second cable portion 20 other than the wire material 220 are connected from the first cable portion 10 without any breaks.

(Arrangement of the first cable part and the second cable part)
Next, the arrangement of the first cable portion 10 and the second cable portion 20 in the axial direction will be described.

As shown in FIG. 1, the length of the pipe 920 in the axial direction (pipe length) is L, the length of the first cable part 10 in the axial direction is L ₁ , and the axial direction of the second cable part 20 to the (total) length and _{L 2.}

As described above, the second cable portion 20 is disposed on both ends of the pipe 920 with the first cable portion 10 interposed therebetween. Thereby, in the part close | similar to the offset part 40, the extension of the electric power cable 1 is suppressed. Here, the 2nd cable part 20 is symmetrically arrange | positioned on both sides of the 1st cable part 10, and the length of the one end side of the pipe line 920 of the 2nd cable part 20 is L < ₂ > / 2. The length L ₂ of the second cable section 20 is set as follows.

Here, the Young's modulus of the first cable portion 10 E, the cross-sectional area of the first conductive portion 110 of the first cable portion 10 A, the linear expansion coefficient of the first cable portion 10 and alpha _1, The second cable The Young's modulus of the part 20 is E ₂ , the cross-sectional area of the second conductive part 210 of the first cable part 20 is A ₂ , the linear expansion coefficient of the second cable part 20 is α _2, and the wire 220 in the second cable part 20 The Young's modulus is E _inv , the cross-sectional area of the wire 220 is A _inv , and the linear expansion coefficient of the wire 220 is α _inv .

At this time, the linear expansion coefficient alpha ₂ of the second cable section 20 is expressed by the following equation (3).

Linear expansion coefficient alpha ₂ of the second cable section 20 is determined by measuring the elongation out length of the second cable section 20 for the above-mentioned or be calculated from equation (3), or a temperature change width t.

Specifically, for example, the Young's modulus E of the first cable portion 10 (approximately equal to the Young's modulus of the first conductive portion 110) is 3 × 10 ³ kgf / mm ² , and the first conductive portion 110 of the first cable portion 10 is used. the cross-sectional area a is 2000 mm ^2, linear expansion coefficient alpha ₁ of the first cable portion 10 is approximately 20 × ^{10 -6} / ° C., the wire 220 is made of invar, Young's modulus _{E inv} of the wire 220 in the second cable section 20 As described above, when 16.5 × 10 ³ kgf / mm ² , the cross-sectional area A _inv of the wire 220 is 102 mm ² , and the linear expansion coefficient α _inv of the wire 220 is 3 × 10 ⁻⁶ / ° C. as described above, According to Equation (3), the linear expansion coefficient α ₂ of the second cable portion 20 is approximately 16.5 × 10 ⁻⁶ / ° C. or less (12 × 10 ⁻⁶ / ° C. when the second cable portion 20 is manufactured and measured). Degree).

Here, let us consider the extension length (m ₀ ) of the power cable in the case where the power cable includes only the first cable portion and does not include the wire material.

FIG. 3 is a stress-distance distribution diagram when the power cable includes only the first cable portion 10. In FIG. 3, the horizontal axis indicates the distance x, and the vertical axis indicates the stress. Note that the upward direction of the vertical axis indicates shrinkage, and the downward direction of the vertical axis indicates extension. Further, in FIG. 3, mu is the friction coefficient, W is the power cable weight per unit length of the (first cable portion 10) (kg / m), t is the temperature change width (° C.), _{S 1} is the stress - Distance It is a shaded area (thermal stress area) of the distribution diagram. As described above, E is the Young's modulus of the first cable portion 10, A is the cross-sectional area of the first conductive portion 110 of the first cable portion 10, and α ₁ is the linear expansion coefficient of the first cable portion 10.

When the extension length that this power cable extends to one side is m ₀ ,
m ₀ = S ₁ / EA (4)
Further, S _1, the stress - is determined as the area of the hatched portion of the trapezoidal in distance distribution diagram,
_{S 1 = LEAαt / 2-μWL} 2/4 ··· (5)
Therefore, m ₀ is expressed by the following formula (6) from the formulas (4) and (5).

  In addition, Formula (6) is equal to the formula which assumed no fixed area in the power cable technology handbook (Denki Shoin) p679.

  Next, the extension length (m) of the power cable 1 according to this embodiment will be considered.

FIG. 4 is a stress-distance distribution diagram in the power cable according to the present embodiment. 4, the horizontal axis indicates the distance x, the vertical axis indicates the stress, the upward direction of the vertical axis indicates contraction, and the downward direction of the vertical axis indicates extension, as in FIG. In FIG. 4, W ₂ is the weight (kg / m) per unit length of the second cable portion 20, S ₁ ′ is the hatched area of the first cable portion 10 in the stress-distance distribution diagram, and S ₂ ′. Is the shaded area of the second cable portion 20 in the stress-distance distribution diagram. As described above, A ₂ is the cross-sectional area of the second conductive portion 210 of the second cable portion 20, and α ₂ is the linear expansion coefficient of the second cable portion 10. Further, the length of one side of the second cable section 20 was set to _{M (= L 2/2)} . Further, the friction coefficient of the second cable portion 20 is equal to the friction coefficient μ of the first cable portion 10, and the Young's modulus (E ₂ ) of the second cable portion 20 is equal to the Young's modulus E of the first cable portion 10. did.

When the extension length that the power cable 1 according to the present embodiment extends to one side is m,
m = S ₁ ′ / EA + S ₂ ′ / EA ₂ (7)
S ₁ ′ and S ₂ ′ are obtained as the area of the hatched portion of the trapezoid in the stress-distance distribution diagram,
_{S 1 '= LEAα 1 t /} 2-μWL 2 / 4- (MEAα 1 t + μWM 2 -2μW 2 M 2) + μWLM-μW 2 LM ··· (8)
S ₂ ′ = MEA ₂ α ₂ t-μW ₂ M ² (9)
Therefore, m is represented by the following formula (10) from the formulas (7) to (9).

At this _time, EA 2 = EA, since it can be approximated as a .mu.W ₂ = .mu.W, also by a M _{= L} 2/2, equation (10) is given by the following equation (11).

Here, the extension length ratio r (%), which is defined as the ratio of the extension length m of the power cable 1 according to the present embodiment to the extension length m ₀ of the power cable not including the wire, is expressed by the following formula (12 ).
r = m / m ₀ × 100 (12)
By substituting Equations (6) and (11) into Equation (12), the extended length ratio r is obtained as in Equation (13) below.

Elongation out length ratio r is less than a predetermined ratio _{r 0} (r ≦ _{r 0)} axial length _{L 2} of the second cable section 20 required for using Formula (13), the following formula (1) It is required as follows.

When the length in the axial direction of the second cable portion 20 required when it is assumed that there is no frictional force is L ₂ ′, L ₂ ′ is obtained from the equation (1) by the following equation (14).
L ₂ ′ ≧ (100−r ₀ ) α ₁ L / (100 (α ₁ −α ₂ )) (14)

On the other hand, the axial length L ₂ of the second cable section 20 required when considering the frictional force, the axial direction of the second cable section 20 required when it is assumed that there is no frictional force in a predetermined condition The length of the second cable portion 20 in the axial direction required when considering the frictional force is approximately 0.8 times the length L ₂ ′ (L ₂ = 0.8L ₂ ′). L ₂ is, from the equation (14) obtained by the following equation (2).

The predetermined ratio r ₀ for the extension length ratio r is, for example, a measurement error when 100-r ₀ measures the extension length of the power cable 1 in the human hole 940, or a predetermined ratio to this measurement error. It is set to be a value multiplied by. Since the measurement error occurs when the extension length of the power cable 1 is measured, the suppression effect of the extension length of the power cable 1 cannot be easily determined unless there is an effect of suppressing the extension length of the power cable 1 beyond the measurement error. Because. Specifically, the measurement error when measuring the extension length of the power cable 1 is about 2%, and the predetermined ratio r ₀ for the extension length ratio r is 100−r _{0 which} is twice this measurement error. For example, 96% is set so as to be (4%).

As described above, in line 920, line length L, a second cable section 20, for example the total length of the axial direction L ₂ are arranged so as to satisfy the above formula (1) or (2) The In addition, since the 2nd cable part 20 is connected to the cable connection part 30 in the state from which the offset part 40 was formed in the part which went out from the pipe line 920, when the length (the bending part is extended) of the offset part 40 when the length) was l _OS, the total length of the axial direction of the second cable section 20 required in between two adjacent cable connection 30 is L _{2 +} 2l _OS.

Specifically, for example, the pipe length L is 300 m, the linear expansion coefficient α ₁ as the entire first cable portion 10 is 20 × 10 ⁻⁶ / ° C., and the linear expansion as the entire second cable portion 20. When the coefficient α ₂ is 12 × 10 ⁻⁶ / ° C., when the predetermined ratio r ₀ with respect to the extended length ratio r is 96%, the second length necessary for the extended length ratio r to be equal to or less than the predetermined ratio 96%. axial length _{L 2} of the cable 20, considering the frictional force equation (1) and the equation (2), it is not less than 24m (i.e. more than one 12m). Since the length l _OS of the offset part 40 is about several meters (3 m or more and 10 m or less), the total length of the second cable part 20 in the axial direction may be 34 m or more.

  Thus, even if the wire rod 220 made of invar is not combined with the entire length of the power cable 1, the effect of sufficiently suppressing the extension of the power cable 1 can be obtained. Further, the extension length ratio r of the power cable 1 is reduced to more than twice the measurement error (2%) of the extension length of the power cable 1 when the extension length ratio r is 96% or less. It can be noticed prominently.

(2) Manufacturing method of power cable Next, the manufacturing method of the power cable 1 which concerns on this embodiment is demonstrated.

For example, a wire 220 made of, for example, a single invar wire is prepared in advance. The wire 220 may be configured by twisting together a plurality of invar wires. At this time, depending on the pipe length of the conduit 920 for laying the power cable 1 L, forming a plurality of wires 220 having a 2L ₂ or more in length.

Next, a plurality of strands made of pure copper, a copper alloy, or the like are twisted to form six segments 110s having a fan-shaped cross section. The first conductive portion 110 is formed by twisting the segments 110s. At this time, the length of the first conductive portion 110 in the axial direction is set to L ₁ in accordance with the pipe length L of the pipe 920 laying the power cable 1.

Next, the cross-sectional shape is changed from the segment 110s of the first conductive portion 110 to form the six segments 210s having a fan-shaped or fan-shaped cross section, and the hollow portion 210w is formed at the center of the segment 210s. When the segments 210s are twisted together, the wire material 220 made of invar wire prepared in advance is inserted into the hollow portion 210w formed at the center of the segment 210s. Thereby, the second conductive portion 210 is formed. In this case, the axial length of the second conductive portion 210 and the length and equal L ₂ or more lengths of wire 220.

As described above, the first conductive portions 110 having the axial length L ₁ and the second conductive portions 210 having the axial length L ₂ or more are continuously and alternately formed.

  Next, an inner semiconductive layer (140, 240), an insulating layer (150, 250) made of polyethylene resin, and an outer semiconductive layer (160) are covered so as to cover the outer periphery of the first conductive portion 110 and the second conductive portion 210. 260) are extruded sequentially or simultaneously in three layers. Next, the intermediate body of the power cable 1 is put into a heating furnace heated to a predetermined crosslinking temperature, and the polyethylene resin in the insulating layers (150, 250) is thermally crosslinked. Next, an outer semiconductive layer (160, 270) is covered with an annealed copper wire or the like to form a shielding layer (172, 272). Next, a pressing tape (174, 274) is wound around the outer periphery of the shielding layer (172, 272). Next, a water shielding layer (176, 276) is formed by winding an aluminum tape around the outer periphery of the pressing tape (174, 274). Next, a sheath (180, 280) made of, for example, polyvinyl chloride is further extruded on the outer periphery of the water shielding layer (176, 276).

  As described above, the power cable 1 according to this embodiment is manufactured.

(3) Effects according to the present embodiment According to the present embodiment and its modifications, the following one or more effects are achieved.

(A) According to the present embodiment, the power cable 1 includes the first cable portion 10 and the second cable portion 20 having a linear expansion coefficient smaller than that of the first cable portion 10. The second cable part 20 is provided along the axial direction in the second conductive part 210, which is made of the same material as the first conductive part 110, and constitutes the second conductive part 210. And a wire composed of a material having a Young's modulus larger than the material and a smaller linear expansion coefficient. In other words, the wire 220 having a small linear expansion coefficient is included in a part of the power cable. Thereby, extension can be suppressed by a simple structure.

  Here, when the first conductive part 110 and the second conductive part 210 of the power cable 1 are energized, the temperature of the first conductive part 110 and the second conductive part 210 rises, so that the first conductive part 110 and the second conductive part 210 increase. 2 The conductive part 210 extends. The first cable portion 10 extends as a whole so as to follow the first conductive portion 110 when the first conductive portion 110 extends. On the other hand, the second cable portion 20 is prevented from extending in the axial direction as follows.

  As described above, the wire 220 inserted into the second conductive portion 210 is made of a material having a Young's modulus and a smaller linear expansion coefficient than the material constituting the second conductive portion 210. As a result, the extended length of the wire 220 is shorter than the extended length of the second conductive portion 210.

  At this time, the second conductive portion 210 bends so as to meander with respect to the axial direction. The second insulating layer 250 and the like provided on the outer periphery of the second conductive unit 210 meander so as to follow the second conductive unit 210. Accordingly, the entire second cable portion 20 can meander. Thereby, the extension by the 2nd electroconductive part 210 is absorbed and the extension to the axial direction of the 2nd cable part 20 is suppressed.

  In addition, when the stress between the second conductive portion 210 that extends in the axial direction and the wire rod 220 that extends in the axial direction and the wire 220 that extends in the axial direction is balanced, the extension by the second conductive portion 210 occurs. May be absorbed. That is, the extension of the second cable portion 20 in the axial direction can be suppressed while the second cable portion 20 does not meander.

  In this way, the extension of the second cable portion 20 of the power cable 1 is suppressed. Therefore, the extended length of the power cable 1 as a whole can be adjusted according to the axial length of the second cable portion 20.

  As described above, according to the present embodiment, it is possible to provide a power cable that can suppress extension by a simple structure.

(B) According to the present embodiment, the bending radius of the offset portion 40 can be maintained at or above the allowable bending radius.

  Here, the extension of the power cable 1 from the pipe 920 that could not be absorbed as described above is absorbed by the deformation of the offset portion 40. The longer the extended length of the power cable 1, the smaller the bending radius of the offset portion 40. For example, the allowable bending radius of the offset portion 40 is set to 10D or more, for example, where D is the outer diameter of the power cable 1.

  According to the present embodiment, the bending radius of the offset portion 40 can be maintained at or above the allowable bending radius by suppressing the power cable 1 from extending from the pipe line 920.

(C) According to the present embodiment, by providing the second cable portion 20, it is possible to sufficiently secure a region in which thermal expansion and contraction does not occur even when a temperature change occurs, a so-called immobile region. Thereby, even when the pipe line 920 is inclined, the power cable 1 is less likely to slip. Therefore, for example, it is not necessary to attach an anti-skid device or the like that suppresses slipping using a spring or weight in the human hole 940 to the power cable 1, and the power cable 1 is laid even if the human hole 940 is small. It becomes possible.

(D) According to this embodiment, the power cable 1 can be easily replaced with an existing OF cable.

  Here, the extension length of the conventional CV cable is longer than the extension length of the OF cable. For this reason, when a conventional CV cable is replaced with an existing OF cable, the bending radius of the offset portion may become smaller than the allowable bending radius set in the existing line due to extension when energized. Moreover, there is a possibility that slipping in the inclined pipe line is likely to occur. Therefore, when laying a conventional CV cable on the track, the manhole must be enlarged so that the bending radius of the offset portion when energized is greater than the allowable bending radius and so that a slip-off prevention device can be installed. I must. Thus, there is a possibility that the conventional CV cable is difficult to lay on the line where the OF cable is already installed.

  On the other hand, according to the present embodiment, the extension length of the power cable 1 when energized can be equal to or less than the extension length of the OF cable. Thereby, when the power cable 1 according to the present embodiment is replaced with an existing OF cable, the bending radius of the offset portion is maintained to be equal to or larger than the allowable bending radius set in the existing line. Sliding in the inclined pipeline is suppressed. Moreover, it is not necessary to enlarge the human hole. Therefore, the power cable 1 according to the present embodiment can be easily replaced with an existing OF cable.

  Furthermore, in this embodiment, the cross-sectional area of the electroconductive part (110,210) of the power cable 1 can be expanded so that it may become equal to the cross-sectional area of the hollow tube used as the path | route of the oil in OF cable, for example. Thereby, the power transmission capacity of the power cable 1 according to the present embodiment can be made larger than the power transmission capacity of the OF cable. In addition, by replacing the power cable 1 according to the present embodiment with an existing OF cable, it is possible to eliminate the oil supply facility associated with the OF cable from within the track.

(E) According to this embodiment, the axial length L ₂ of the second cable portion 20 which is laid in a conduit 920 satisfies the above formula (1) or formula (2). Thereby, the extension length ratio r defined as the ratio of the extension length m of the power cable 1 according to the present embodiment to the extension length m ₀ of the power cable not including the wire may be set to a predetermined ratio r ₀ or less. it can. That is, when the length L ₂ in the axial direction of the second cable 20 satisfies the formula (1) or the formula (2), the extension of the power cable can be recognized more significantly than the power cable not including the wire. It is possible to suppress the ejection.

(F) According to the present embodiment, at least a part of the outer surface of the wire 220 is in contact with the inner wall of the second conductive portion 210. When the second conductive portion 210 extends, a frictional force is generated between the wire 220 and the second conductive portion 210. Thereby, extension of the 2nd electric conduction part 210 to wire rod 220 is controlled, and it is controlled that the 2nd cable part 20 extends entirely.

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

  In the above-described embodiment, the wire 220 is made of Invar wire, but the wire may be made of, for example, carbon fiber, aramid fiber such as Kevlar (registered trademark) manufactured by DuPont.

  Further, the shape and number of segments, the number of layers, the arrangement, the number and arrangement of inserted wires described in the above-described embodiments and modifications are merely examples, and are not limited thereto.

  In the above-described embodiment, the power cable 1 in which the wire material 220 such as the invar wire is combined with the CV cable has been described. However, the present configuration may be applied to an OF cable and other cables.

  Moreover, although the above-mentioned embodiment demonstrated the case where the 2nd cable part 20 was arrange | positioned on both ends of the pipe line 920 on both sides of the 1st cable part 10, the 2nd cable part is laid in the pipe line. The power cable may be provided at least in part in the axial direction of the power cable. For example, the second cable portions may be arranged in a distributed manner in the axial direction of the power cable.

  Moreover, although the above-mentioned embodiment demonstrated the case where the 1st cable part 10 and the 2nd cable part 20 were formed continuously, a 1st cable part and a 2nd cable part are connected by cable connection parts, such as a rubber unit. It may be connected.

  Next, examples according to the present invention will be described in comparison with comparative examples.

(1) Examples and Comparative Examples As examples of the present invention, the axial length L _{2 of} the second cable portion and the cross-sectional area A _{inv of the} wire are respectively set so that the nominal voltage is 154 kV as follows. Several different power cables were made.
(Power cable)
Length (pipe length) L 300m
(First cable part)
Nominal cross-sectional area A of the first conductive part A 2000 mm ²
17mm thickness of the first insulating layer
The thickness of the first sheath 5.5mm
Young's modulus E 3 × 10 ³ kgf / mm ^{2 of} the first cable part
Linear expansion coefficient α ₁ 20 × 10 ⁻⁶ / ° C. of the first cable part
Friction coefficient of the first cable part μ 0.4
Weight per unit length of the first cable part W 26kg / m
(Second cable part)
Nominal cross-sectional area A ₂ 2000 mm ^{2 of} the second conductive part
Section area A _inv of wire rod (invar) 22 mm ² or more and 138 mm ² or less Thickness of second insulating layer 17 mm
Second sheath thickness 5.5mm
The second weight per unit length of the second cable section which is equal to the μ of the first cable portion friction coefficient of the cable portion W ₂ a which was equal to E Young's modulus E ₂ first cable portion of the second cable portion 1 of the axial length of the second cable section which is equal to the _{W 1} of the cable section _L 2 2m or 60m or less

  Moreover, the power cable which does not contain a wire as a comparative example was produced. That is, the power cable of the comparative example is configured similarly to the configuration of only the first cable portion of the example. The length (pipe length) L of the power cable of the comparative example was 300 m.

(2) Evaluation of power cables (measurement of linear expansion coefficient)
When the cross-sectional area A _inv of the wire is different, the linear expansion coefficient α ₂ of the second cable portion is different. Therefore, it was measured linear expansion coefficient alpha ₂ for each of the second cable cut cable portions only examples. As a result, the linear expansion coefficient α ₂ of the second cable portion in the power cable of the example was 11.5 × 10 ⁻⁶ / ° C. or more and 16.5 × 10 ⁻⁶ / ° C. or less.

(Extension length ratio)
When the temperature change width t is 65 ° C., the wire rod is not included by substituting the condition of the above-described embodiment and the comparative example and the linear expansion coefficient α ₂ of the second cable portion into the above equation (13). It was calculated elongation out length ratio r, defined as the ratio of the elongation out length m of the power cable embodiment for stretching out length m ₀ of the power cable of the comparative example.

(3) Results FIG. 5 is a diagram showing the extension length ratio r with respect to the axial length L ₂ of the second cable portion 20. As shown in FIG. 5, in the power cable according to the embodiment, the extension of the power cable is suppressed by providing the second cable portion 20 in the pipe length L, and the extension length ratio r is 2 decreases monotonically with respect to the axial length L ₂ of the cable section 20. By adjusting the length L ₂ axial direction of the second cable section is adjustable stretch out length m as a whole a power cable, it can be seen that adjusting the elongation out length ratio r.

Further, as the linear expansion coefficient alpha ₂ of the second cable section is reduced, the inclination of the elongation-out length ratio r with respect to the axial length L ₂ of the cable portion 20 is steep. It can be seen that the smaller the linear expansion coefficient α ₂ of the second cable portion, the greater the extension length ratio r can be reduced with the shorter axial length L ₂ of the second cable portion 20.

Here, FIG. 6 is a diagram showing the length L ₂ of the second axial direction of the second cable portion to the linear expansion coefficient alpha ₂ of the cable portion when extended out length ratio r is 96%. The solid line curve in FIG. 6 indicates the length L ₂ in the axial direction of the second cable portion with respect to the linear expansion coefficient α ₂ when r ₀ = 96 (%) is substituted into Equation (1) considering the frictional force. It is a function. Further, the broken line curve in FIG. 6 indicates the axial direction of the second cable portion with respect to the linear expansion coefficient α ₂ when r ₀ = 96 (%) is substituted into the equation (14) when it is assumed that there is no friction force. Is a function of length L ₂ ′. The extension length ratio r of 96% or less means that the extension length ratio r is reduced to at least twice the measurement error (2%) of the extension length of the cable in the human hole. .

The horizontal axis linear expansion coefficient alpha ₂ of second cable section is in Figure 6, varies according to the cross-sectional area of, for example, wires. For this reason, the length in the axial direction of the second cable portion 20 necessary for the extension length ratio r to be equal to or less than the predetermined ratio r ₀ (96%) according to the linear expansion coefficient α ₂ of the second cable portion. L ₂ also changes.

As shown by the solid line in FIG. 6, the second length necessary for the extension length ratio r to be equal to or less than a predetermined ratio r ₀ (96%) with respect to the linear expansion coefficient α ₂ of the second cable portion. axial length L ₂ of the cable 20 can be seen to increase monotonically. In other words, the smaller the linear expansion coefficient α ₂ of the second cable part, the longer the length ratio r in the extension direction, the smaller the predetermined ratio r ₀ (96%) or less. L ₂ becomes shorter. Further, when the region length L ₂ is greater in the axial direction of the second cable portion 20 than the curve in the figure can be a stretch out length ratio r predetermined ratio r _{0 (96%)} or less.

Further, in FIG. 6, in the above-mentioned condition, a second axial direction of the cable portion of the length L ₂ function (solid curve) in consideration of the frictional force, the second cable on the assumption that there is no frictional force About 0.8 times the function (dashed curve) of the axial length L ₂ ′ of the portion (L ₂ = 0.8L ₂ ′). Therefore, when the frictional force is taken into consideration, the axial length L ₂ of the second cable portion 20 necessary for setting the extended length ratio r to be equal to or less than the predetermined ratio r ₀ (96%) is expressed by the above formula. (2).

  As described above, according to the embodiment, it is possible to provide a power cable capable of suppressing extension by a simple structure.

DESCRIPTION OF SYMBOLS 1 Electric power cable 10 1st cable part 20 2nd cable part 30 Cable connection part 40 Offset part 110 1st electroconductive part 110s Segment 130 1st binder 140 1st internal semiconductive layer 150 1st insulating layer 160 1st external semiconductive layer 172 First shielding layer 174 First pressing tape 176 First water shielding layer 180 First sheath 210 Second conductive portion 210s Segment 210w Hollow portion 220 Wire rod 230 Second binder 240 Second internal semiconductive layer 250 Second insulating layer 260 First 2 external semiconductive layer 272 second shielding layer 274 second pressing tape 276 second water shielding layer 280 second sheath 920 conduit 940 human hole

Claims (10)

A first cable portion;
A second cable portion connected to the first cable portion along the axial direction;
With
The first cable part has a first conductive part,
The second cable portion is
A second conductive portion made of the same material as the first conductive portion;
A wire rod made of a material provided in the second conductive portion along the axial direction and having a Young's modulus larger than that of the material constituting the second conductive portion and a small linear expansion coefficient;
A power cable characterized by comprising: The pipe length is L, the Young's modulus of the first cable part is E, the area of the first conductive part of the first cable part is A, the linear expansion coefficient of the first cable part is α ₁ , and the inside of the pipe line The length of the second cable portion laid in the axial direction is L ₂ , the linear expansion coefficient of the second cable portion is α ₂ , the friction coefficient is μ, the unit weight of the first cable is W, the temperature change width T, and the ratio of the extension length to the extension length of the power cable not including the wire rod is equal to or less than a predetermined ratio r ₀ (%), the second cable portion laid in the pipe line The power cable according to claim 1, wherein the axial length L ₂ satisfies the following expression (1).

The line length is L, the linear expansion coefficient of the first cable part is α ₁ , the axial length of the second cable part installed in the pipe line is L ₂ , and the linear expansion of the second cable part When the coefficient is α ₂ and the ratio of the extension length to the extension length of the power cable not including the wire is not more than a predetermined ratio r ₀ (%), the second cable laid in the pipe line axial length L ₂ of the parts, the power cable according to claim 1 or 2, characterized by satisfying the equation (2) below.

Power cable according to claim 2 or 3 wherein the predetermined ratio r ₀ is equal to or 96%. When the pipe length is 300 m, the linear expansion coefficient of the first cable part is 20 × 10 ⁻⁶ / ° C., and the linear expansion coefficient of the second cable part is 12 × 10 ⁻⁶ / ° C., The power cable according to any one of claims 1 to 4, wherein an axial length of the second cable portion laid on the cable is 24 m or more. The second cable part has a hollow part provided in a central part of the second conductive part and extending in an axial direction of the second conductive part,
The power cable according to claim 1, wherein the wire is inserted into the hollow portion. The power cable according to claim 1, wherein at least a part of the outer surface of the wire is in contact with the second conductive portion. The power cable according to any one of claims 1 to 7, wherein the second cable portion is disposed on both ends of a pipeline with the first cable portion interposed therebetween. 9. The electric power according to claim 1, wherein at least a part of the second conductive portion is in a meandering state when energizing the first conductive portion and the second conductive portion. cable. The first conductive part and the second conductive part are copper conductors,
The power cable according to claim 1, wherein the wire is an invar wire.

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