JP2014007042A - Power cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power cable structure including a wire shield 6 formed by winding spirally multiple conductors 6a with a gap on an outer semiconducting layer 4, to suppress disturbance in wire-shield conductors and demonstrate sufficient shielding performance of the wire shield.SOLUTION: A wire shield 6 is covered with tape 9 so that there are exposed parts and unexposed parts in each conductor 6a. Thereover, resin is extruded to form a sheath 8, to form resin-entering parts and no-resin-entering parts between the conductors. In the resin-entering parts, it is possible to avoid disturbance of the conductors 6a, and in the no-resin-entering parts, the condition of electrical conduction between an outer semiconducting layer 4 and the wire-shield conductors 6a is maintained good.

Description

  The present invention relates to a power cable having a wire shield.

  FIG. 5 shows an example of a conventional wire shield power cable. This cable has a conductor 1 in the center, an inner semiconductive layer 2, an insulator 3, and an outer semiconductive layer 4 provided thereon, and a cushion layer 5 formed by winding a semiconductive cloth tape thereon. A wire shield 6 is provided by spirally winding a large number of conductive wires (an annealed copper wire) 6a at intervals, and a resin sheath 8 is provided after a pressing tape 7 is wound (see Non-Patent Document 1). In this cable, an external semiconductive layer 4 and a semiconductive cushion layer 5 are interposed between the insulator 3 and the wire shield 6, and since they have appropriate conductivity, the insulator 3 and the wire shield 6 are connected. This prevents partial discharge at

  However, in this cable, since the conducting wire 6a of the wire shield 6 is only pressed from above by the holding tape 7, when the cable is bent, the conducting wire 6a is disturbed, for example, offset or buckled. There was a problem that it was easy.

  As a solution to this problem, a power cable as shown in FIG. 6 is known. This cable has the same structure within the wire shield 6 as that of the cable of FIG. 5, but the sheath is provided between the wire shield conductors 6 a by extruding the resin sheath 8 without providing a pressing tape on the wire shield 6. A resin is introduced (see Patent Documents 1 and 2). If it does in this way, since conducting wire 6a is restrained by sheath 8, disorder of conducting wire 6a when a cable is bent can be controlled.

  5 and 6 show the case where the semiconductive cushion layer 5 is provided on the external semiconductive layer 4, but the semiconductive cushion layer 5 is not provided and the external semiconductive layer 4 is not provided. In some cases, the wire shield 6 may be provided directly on.

Microfilm of actual application No.59-34442 (No.60-147112) Microfilm of actual application No.59-166210 (No.61-80530)

Page 173 of Electric Power Cable Technology Handbook

  However, the power cable in which the sheath resin is inserted between the conductors of the wire shield has the following problems. That is, in order to allow sheath resin to enter between the conductors of the wire shield, the resin pressure is adjusted so that the resin enters moderately between the conductors when the heated and pressurized resin is extruded as a sheath in the crosshead of the extruder. There is a need to. At this time, if the sheath resin completely wraps around the conductive wire, the conductive wire and the semiconductive cushion layer (external semiconductive layer in the absence of this) are insulated by the sheath resin, so that the charging current and the current at the time of the accident are Since it does not flow from the cable core to the wire shield, it cannot function as a shield. In addition, when the resin does not enter between the conductors, the conductor is not sufficiently restrained by the sheath resin, and the conductor is likely to be disturbed when the cable is bent.

  As described above, the power cable in which the sheath resin is inserted between the conductors of the wire shield has a problem even if the resin enters between the conductors too much or too little, and the adjustment is difficult.

  In view of the above-described problems, an object of the present invention is to provide a power cable in which the wire shield is less likely to be disturbed and the wire shield can exhibit a sufficient shielding performance.

  In order to achieve the above object, the present invention provides a power cable having a wire shield formed by spirally winding a large number of conductive wires on an external semiconductive layer or a semiconductive cushion layer provided thereon. Cover the wire shield with tape so that the exposed and unexposed portions of each conductor are formed, and then form a sheath by extrusion coating the resin on the wire shield so that the sheath resin enters between the conductors. This is characterized in that no part is provided.

  In the present invention, the tape is preferably vertically attached on a wire shield.

  In the present invention, the tape may be spirally wound on the wire shield in a direction opposite to the spiral direction of the conductor or in the same direction as the spiral direction of the conductor at a pitch different from the spiral pitch of the conductor.

  In the present invention, the tape may be spirally wound on the wire shield in a direction opposite to the spiral direction of the conductive wire and in the same direction.

  In the present invention, the tape may have a hole so that a portion where the conductive wire is exposed when the wire shield is covered is formed.

  In the present invention, the ratio of the portion where the wire shield is not covered with the tape is 30% to 80%, assuming that the case where the wire shield is completely covered with the tape is 0% and the case where there is no tape is 100%. It is preferable.

  According to the present invention, since the sheath resin sufficiently enters between the conductors in the portion where the conductor of the wire shield is not covered with the tape, the conductor is restrained by the sheath resin, and the disturbance of the conductor can be prevented. Since the sheath resin does not enter between the conductors where the conductor is covered with the tape, it is possible to maintain a good electrical continuity between the external semiconductive layer or the semiconductive cushion layer provided thereon and the wire shield conductor. it can. For this reason, it is possible to obtain a power cable in which the wire shield is hardly disturbed and the wire shield can exhibit a sufficient shielding performance.

(A) is the side view which shows one Example of the power cable which concerns on this invention in the step-peeled state, (B) is the BB sectional drawing of (A). The side view which shows the other Example of the power cable which concerns on this invention in the step peeling state. The side view which shows the further another Example of the power cable which concerns on this invention in the step peeling state. (A) is a side view showing still another embodiment of the power cable according to the present invention in a stepped state, (B) is a plan view of the tape used for the cable of (A). Sectional drawing which shows an example of the conventional electric power cable. Sectional drawing which shows the other example of the conventional electric power cable.

  Example 1 FIG. 1 shows an example of the present invention. In the figure, 1 is a conductor, 2 is an internal semiconductive layer, 3 is an insulator, 4 is an external semiconductive layer, and 6 is a wire shield in which a large number of conductors 6a are spirally wound on the external semiconductive layer 4 at intervals. is there. A characteristic of this power cable is that a tape 9 is vertically attached on the wire shield 6 with an interval in the circumferential direction (the number of tapes is arbitrary, but two in the illustrated example), and a resin is extrusion coated thereon. Thus, the sheath 8 is formed.

  When the tape 9 is vertically attached on the wire shield 6 with an interval in the circumferential direction, a portion where the wire 6a of the wire shield is exposed and a portion which is covered with the tape 9 and not exposed are formed. When the sheath 8 is extrusion-coated thereon, the sheath resin enters the gap between the conductors 6a in the portion where the conductor 6a is exposed, and is blocked by the tape 9 in the portion where the conductor 6a is not exposed, so that the sheath resin does not enter between the conductors 6a. .

  On the other hand, since the conductor 6a is spirally wound, the tape 9 is vertically attached in the longitudinal direction of the cable. Therefore, each conductor 6a and the tape 9 intersect each other, and each conductor 6a is connected in the longitudinal direction ( When viewed in the spiral direction), a section in which the resin enters between the conductive wires and a section in which the resin does not enter are alternately repeated. As a result, each conductor 6a is prevented from moving by the resin in the section where the resin enters between the conductors, and maintains a good electrical conduction state with the external semiconductive layer 4 in the section where the resin does not enter. When viewed from the full length, the wire shield conductor 6a is less likely to be disturbed, and the wire shield 6 can exhibit sufficient shielding performance.

  When the resin sheath 8 is extrusion-coated on the wire shield 6, the resin pressure may be adjusted so that the resin sufficiently wraps around the individual conductors 6a. Since a portion for preventing the resin from entering is formed on the tape 9, a delicate pressure adjustment is unnecessary, and the resin sheath can be easily covered by extrusion.

  In this embodiment, the case where the wire shield 6 is provided directly on the external semiconductive layer 4 has been described. However, the same configuration can be used when a wire shield is provided on the external semiconductive layer via a semiconductive cushion layer. Yes (same in the following examples).

Next, the trial production and test results of the power cable (22 kV, 600 mm ² ) of this example will be described. The material and size of each part are as follows.
・ Conductor: Circular compression type annealed copper stranded wire Diameter of about 30mm
・ Inner semiconductive layer: Semiconductive polyolefin resin blend Thickness 1mm
・ Insulator: Cross-linked polyethylene, 6mm thick
・ External semiconductive layer: Semiconductive polyolefin resin blend Thickness 1mm
・ Wire shield: Annealed copper wire 1.2mmφ × 40 helix pitch 145mm (3 times the core diameter of wire shield layer) Right-handed outer circumference 152mm
・ Tape: Non-woven fabric, thickness 0.2mm, various widths, 2 sheets vertically ・ Sheath: Polyvinyl chloride, thickness 3.5mm, cable outer diameter 56mm

  Varying the width of the tape, the tape opening ratio (the percentage of the part where the wire shield is not covered with tape is 0% when it is completely covered with tape, and 100% when there is no tape) Prototype cable.

First, the resistance value between the wire shield and the external semiconductive layer was measured for each cable, and the resistance ratio of each cable was determined based on the resistance value when the tape opening ratio was 0%. In order to maintain the electrical characteristics of the power cable, the resistance ratio between the wire shield and the external semiconductive layer was determined to be a non-defective product (○) when the resistance ratio was 2.0 or less, and the defective product (×) when the resistance ratio was greater than 2.0.
The calculation method of the resistance ratio is as follows.
Resistance ratio = (resistance value between the wire shield of the prototype cable and the external semiconductive layer) ÷ (resistance value between the cable shield of the prototype cable and the external semiconductive layer that differs only in that the tape opening ratio is 0%)
Cables that differ from the prototype cable only in that the tape opening rate was set to 0% were procured from off-the-shelf products.

  Next, the state of buckling of the wire shield after the cable was repeatedly wound around the mandrel having a diameter four times the outer diameter of the cable (repeated bending test) was examined. After the repeated bending test, the part where the wire shield was bent sharply abruptly was judged to be buckled (×), and the part where the wire shield was bent sharply abruptly was judged to be buckled (O). . The results are shown in Table 1.

  According to this test result, it is understood that the tape opening ratio is preferably 30 to 80%.

  <Embodiment 2> FIG. 2 shows another embodiment of the present invention. In the figure, the same parts as those in FIG. The characteristic of this power cable is that the tape 9 is spirally wound on the wire shield 6 in the circumferential direction at intervals in the circumferential direction (the number of tapes is arbitrary but 2 in the illustrated example). Sheet), and a sheath 8 was formed by extrusion coating of resin thereon.

  When the tape 9 is spaced apart in the circumferential direction on the wire shield 6 and spirally wound (gap winding) in the direction opposite to the spiral direction of the conductor 6a, the portion where the conductor 6a of the wire shield is exposed and the tape 9 are covered. There are unexposed areas. When the sheath 8 is extrusion-coated from above, the sheath resin enters the gap between the conductors 6a in the portion where the conductor 6a is exposed, and the sheath resin does not enter between the conductors 6a because the sheath 9 is blocked by the tape 9 in the portion where the conductor 6a is not exposed. .

  Therefore, as in Example 1, when each conductor 6a is viewed in the longitudinal direction (spiral direction), a section where the resin enters between the conductors and a section where the resin does not enter are alternately repeated. The same effect as in Example 1 can be obtained.

  Prototype a power cable different from that of Example 1 in that the wire shield 6 was applied at a spiral pitch of 230 mm (5 times the core diameter of the wire shield layer) and the tape 9 was spirally wound as described above. It was confirmed that a similar effect was obtained.

  In this embodiment, the case where the tape 9 is spirally wound in the direction opposite to the spiral direction of the conductor 6a has been described. However, the tape 9 is spirally wound with the spiral pitch being different in the same direction as the spiral direction of the conductor. In such a configuration, the same effect as that of the first embodiment can be obtained.

  <Embodiment 3> FIG. 3 shows still another embodiment of the present invention. In the figure, the same parts as those in FIG. The characteristic of this power cable is that a plurality of (four in the illustrated example) tapes 9 are wound on the wire shield 6 in the circumferential direction with different spiral directions (spiral winding). The sheath 8 was formed by extrusion coating of resin thereon. In this case, it is preferable that the spiral pitch of the tape 9 spirally wound in the same direction as that of the conductor 6a is different from that of the conductor 6a.

  Even in such a configuration, when each conductor 6a is viewed in the longitudinal direction (spiral direction), the section in which the resin enters between the conductors and the section in which the resin does not enter are alternately repeated. 1 can be obtained.

  Prototype a power cable different from that of Example 1 in that the wire shield 6 was applied at a spiral pitch of 230 mm (5 times the core diameter of the wire shield layer) and the tape 9 was spirally wound as described above. It was confirmed that a similar effect was obtained.

  Example 4 FIG. 4A shows still another example of the present invention. In the figure, the same parts as those in FIG. The characteristic of this power cable is that a tape 9 having holes 10 as shown in FIG. 5B is spirally wound on the wire shield 6 without any interval in the circumferential direction, and a resin is extrusion coated thereon. Thus, the sheath 8 is formed.

  If it does in this way, the conducting wire 6a will be exposed in the hole 10 part of the tape 9, and resin will enter between conducting wires, and the conducting wire 6a will be covered with the tape 9 in the part which does not have the hole 10, and resin will not enter between conducting wires. For this reason, as in each of the above embodiments, when each conductor 6a is viewed in the longitudinal direction (spiral direction), the section where the resin enters between the conductors and the section where the resin does not enter are alternately repeated. The same effect as in the first embodiment can be obtained.

Next, the trial production and test results of the power cable (22 kV, 600 mm ² ) of this example will be described. The materials and sizes of the conductor, the inner semiconductive layer, the insulator, the outer semiconductive layer, the wire shield, and the sheath are the same as those of the prototype cable of Example 1. The tape was 0.2mm thick and 50mm wide with a circular hole punched out. This tape was wrapped 5mm in the width direction and spirally wound. By changing the hole diameter and pitch of the tape, we prototyped cables with various tape opening ratios. For each cable, as in the case of Example 1, the resistance ratio of each cable based on the resistance value when the tape opening ratio was 0% was obtained, and a repeated bending test was performed. Even in this test, the same result as in Example 1 was obtained, and it is preferable that the tape opening ratio be 30 to 80% in order to secure the electrical characteristics as a power cable and to keep the bending characteristics good. I understood.

  In this embodiment, the case where the perforated tape 9 is spirally wound (wrapped or closely wound) on the wire shield 6 without spacing in the circumferential direction has been described. However, the perforated tape 9 is spaced in the circumferential direction. Spiral winding (gap winding) may be performed with a gap between them, or they may be added vertically without spacing in the circumferential direction or at intervals.

1: Conductor 2: Inner semiconductive layer 3: Insulator 4: Outer semiconductive layer 6: Wire shield 6a: Conductor 8: Resin sheath 9: Tape 10: Hole

Claims (6)

  In a power cable having a wire shield formed by spirally winding a large number of conductive wires on an external semiconductive layer or a semiconductive cushion layer provided thereon, each of the conductive wires is exposed to the wire shield. Covering with tape so that the part and the unexposed part can be formed, and forming a sheath by extruding the resin on it, providing a part where the sheath resin enters and a part where it does not enter between the conductors Power cable.   The power cable according to claim 1, wherein the tape is vertically attached on the wire shield.   2. The tape according to claim 1, wherein the tape is spirally wound on the wire shield in a direction opposite to the spiral direction of the conductor or in a direction different from the spiral pitch of the conductor in the same direction as the spiral direction of the conductor. Power cable.   2. The power cable according to claim 1, wherein the tape is spirally wound on the wire shield in a direction opposite to and in the same direction as the spiral direction of the conductor.   The power cable according to claim 1, wherein the tape has a hole so that a portion where the conductive wire is exposed when the wire shield is covered is formed.   The ratio of the portion where the wire shield is not covered with tape is 30% to 80% when 0% is when it is completely covered with tape and 100% when there is no tape. The power cable according to claim 1.

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