CN114744461B

CN114744461B - Manufacturing method of control cable head

Info

Publication number: CN114744461B
Application number: CN202210659221.4A
Authority: CN
Inventors: 林浩勤; 黄杨明; 冼建能; 苏志伟; 张泽良; 魏宜华; 莫荣辉; 邓健强; 陈挺求; 邵剑文; 吴小将; 伍燕咏; 彭将翔; 赵雪
Original assignee: Foshan Power Supply Bureau of Guangdong Power Grid Corp
Current assignee: Foshan Power Supply Bureau of Guangdong Power Grid Corp
Priority date: 2022-06-13
Filing date: 2022-06-13
Publication date: 2022-09-06
Anticipated expiration: 2042-06-13
Also published as: CN114744461A

Abstract

The invention relates to the technical field of control cables, in particular to a manufacturing method of a control cable head, which comprises the following manufacturing steps of S1, insulation detection; s2, sequentially stripping the outer sheath, the steel tape armor, the inner sheath and the copper shielding layer of the control cable to form a step shape; s3, manufacturing a shielding grounding wire: s3.1, stripping partial insulating skins of the first grounding wire and the second grounding wire, exposing copper wires, and winding and welding the copper wires of the first grounding wire on the steel belt armor; winding the copper wire of the second grounding wire on the copper shielding layer and welding; s3.2, respectively wrapping fixed outer skins at the welding position of the first grounding wire and the steel tape armor and the welding position of the second grounding wire and the copper shielding layer; s4, manufacturing a heat shrinkable sleeve, respectively installing an inner heat shrinkable sleeve and an outer heat shrinkable sleeve, and leading free ends of the first ground wire and the second ground wire out of a port of the outer heat shrinkable sleeve; the invention effectively solves the problem of unreliable connection between the grounding wire and the wire core, improves the operation reliability of the control cable and eliminates potential safety hazards.

Description

Manufacturing method of control cable head

Technical Field

The invention relates to the technical field of control cables, in particular to a manufacturing method of a control cable head.

Background

The control cable is widely applied to a traditional transformer substation, an intelligent transformer substation and a modular transformer substation, can transmit various control signals, is used for telecommunication or power transmission, and guarantees safe and reliable operation of a power system.

However, the abnormal operation of the power system caused by the manufacturing process problem of the control cable head often occurs, so that serious potential safety hazards exist, the control cable head manufactured by the existing manufacturing process has large contact resistance due to unreliable grounding wires and wire cores, the problem of local overheating after current impact occurs, the insulation performance of the control cable is damaged, and the potential safety hazards are increased.

Disclosure of Invention

The invention provides a manufacturing method of a control cable head for overcoming the defects in the prior art, effectively solves the problem of unreliable connection between a grounding wire and a wire core, improves the operation reliability of a control cable, and eliminates potential safety hazards.

In order to solve the technical problems, the invention adopts the technical scheme that: a manufacturing method of a control cable head comprises the following manufacturing steps:

s1, insulation detection: before laying a control cable, suspending two ends of the control cable, and respectively testing insulation resistances between wire cores and between the wire cores and a shielding layer by using an insulation resistance meter;

s2, stripping off the control cable head: sequentially stripping the outer sheath, the steel strip armor, the inner sheath and the copper shielding layer of the control cable to form a ladder shape, and confirming that each stripping cut is clear in level and flat and smooth;

s3, manufacturing a shielding grounding wire:

s3.1, stripping partial insulating skins of a first grounding wire and a second grounding wire, exposing copper wires, winding the copper wires of the first grounding wire on the steel strip armor, and welding the ends of the wound copper wires of the first grounding wire on the steel strip armor; winding the copper wire of the second grounding wire on the copper shielding layer, and welding the end of the wound copper wire of the second grounding wire on the copper shielding layer;

s3.2, respectively wrapping fixed outer skins at the welding position of the first grounding wire and the steel tape armor and the welding position of the second grounding wire and the copper shielding layer;

s4, manufacturing a heat-shrinkable sleeve:

s4.1, stripping off part of the fiber layer of the control cable to expose the wire core;

s4.2, installing an inner heat-shrinkable sleeve, wherein the inner heat-shrinkable sleeve sequentially covers the fiber layer, the copper shielding layer, the inner sheath and the steel strip armor;

and S4.3, installing an outer heat shrinkable sleeve, covering the inner heat shrinkable sleeve and part of the outer sheath, and leading the free ends of the first ground wire and the second ground wire out of the port of the outer heat shrinkable sleeve respectively.

Further, the copper wires of the first and second ground lines in step S3.1 are respectively processed as follows:

(a) dividing the copper wire of the first grounding wire into two beams, namely a first copper wire and a second copper wire, reversely winding the first copper wire and the second copper wire on the steel strip armor respectively, and screwing and welding the ends of the wound first copper wire and the wound second copper wire on the steel strip armor;

(b) dividing the copper wire of the second grounding wire into two beams, namely a third copper wire and a fourth copper wire, reversely winding the third copper wire and the fourth copper wire on the copper shielding layer respectively, and screwing and welding the ends of the wound third copper wire and the wound fourth copper wire on the copper shielding layer.

Further, when the first ground wire and the second ground wire are welded, heat insulating sheets need to be inserted between the steel tape armor and the inner sheath, and between the copper shield layer and the fiber layer.

Further, the insertion depth of the heat insulating sheet is not less than 8 mm.

Further, the heat insulation sheet is a bamboo sheet or a wood sheet.

Further, in step S4.2, the following steps are also included:

and winding a polyvinyl chloride wrapping tape on the control cable before installing the inner heat-shrinkable sleeve.

Further, when the inner heat-shrinkable sleeve and the outer heat-shrinkable sleeve are installed, the processing temperature is 100-120 ℃.

Further, the free end of the first ground wire is led out from the outer heat shrinkable sleeve towards one end of the outer sheath, and the free end of the second ground wire is led out from the outer heat shrinkable sleeve towards one end of the wire core.

Further, the first ground wire and the second ground wire respectively adopt a plurality of strands of yellow-green annealed copper wires with wire diameters not smaller than 4 mm.

Further, in step S3, the method further includes the following steps:

and after the first grounding wire and the second grounding wire are welded, carrying out intermediate special inspection on the control cable according to the requirements of hidden engineering.

Compared with the prior art, the invention has the following beneficial effects:

the invention provides a manufacturing method of a control cable head, which comprises the following manufacturing steps:

s2, stripping off the control cable head: sequentially stripping the outer sheath, the steel strip armor, the inner sheath and the copper shielding layer of the control cable to form a step shape, and confirming that each stripping cut is clear in level, flat and smooth;

s3, manufacturing a shielding grounding wire:

s4, manufacturing a heat-shrinkable sleeve:

s4.3, installing an outer heat shrinkable sleeve, wherein the outer heat shrinkable sleeve covers the inner heat shrinkable sleeve and part of the outer sheath, and the free ends of the first ground wire and the second ground wire are respectively led out from the port of the outer heat shrinkable sleeve;

when the invention is used for manufacturing a control cable head, in the step S3 of manufacturing a shielding grounding wire, a first grounding wire and a second grounding wire are respectively wound on a steel tape armor and a copper shielding layer, the ends of the first grounding wire and the second grounding wire are respectively welded after winding, and then a fixed sheath is wrapped at the welding position after welding, wherein the first grounding wire and the second grounding wire are wound for increasing the contact area of the first grounding wire and the second grounding wire with the steel tape armor and the copper shielding layer respectively, the welding ends are used for increasing the connection firmness of the first grounding wire and the second grounding wire with the steel tape armor and the copper shielding layer respectively, the fixed sheath is wrapped for further improving the connection firmness of the welding position and avoiding the virtual connection of the grounding wires, and the manufacturing method comprising the fixed sheath through winding and welding improves the connection reliability of the grounding wires and the anti-interference capability and avoids the damage to the insulating property of the control cable, the potential safety hazard of the control cable in operation is eliminated, and meanwhile, the manufacturing process is simple, the requirement on the technical level of operators is low, and the implementation is convenient.

Drawings

FIG. 1 is a process flow diagram of the present invention;

FIG. 2 is a schematic structural view of the control cable of the present invention after peeling;

fig. 3 is a schematic structural view of welding a first ground wire and a second ground wire in the present invention;

fig. 4 is a schematic structural view of the present invention for installing the inner heat shrinkable sleeve and the outer heat shrinkable sleeve.

Reference numerals: 1-an outer sheath; 2-steel tape armoring; 3-inner sheath; 4-a copper shield layer; 5-a fiber layer; 6-wire core; 7-a first ground line; 8-a second ground line; 9-internal heat-shrinkable sleeve; 10-external thermal shrinkage sleeve.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The invention is described below in one of its embodiments with reference to specific embodiments. Wherein the showings are for the purpose of illustration only and are shown by way of illustration only and not in actual form, and are not to be construed as limiting the present patent; to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.

Examples

The control cable is used for transmitting control and measurement signals and the like, and mainly comprises a wire core, an insulating layer, a shielding layer, a sheath layer and the like; the cable core is usually made of nonferrous metals with excellent conductivity such as copper and the like and is used for controlling the current or electromagnetic transmission function of the cable; the insulating layer is coated on the periphery of the control cable core and used for insulating, so that the current transmitted by the control cable is prevented from leaking to the outside, the normal transmission function of the control cable core is ensured, and the safety of external objects and human bodies is ensured; the shielding layer is an electromagnetic isolation screen and is used for resisting interference; when the control cable head is manufactured, the cut of each layer structure needs to be guaranteed to be smooth and flat, otherwise, the insulating layer is easy to be punctured, and danger is caused.

As shown in the figure, the manufacturing method of the control cable head comprises the following manufacturing steps:

s1 Cable insulation detection

Before laying the control cable, performing insulation detection on the control cable, firstly confirming that two ends of the control cable are suspended, testing insulation resistances between the cores of the control cable and between the cores and a shielding layer by using a 1000V insulation resistance meter, wherein the insulation resistance values are all larger than the specification of 10M omega, discharging after the test is finished, and temporarily wrapping the cores of the control cable stripped by the test by using an insulation adhesive tape to prevent the cores from being affected with damp;

s2, stripping the control cable head, sequentially stripping the outer sheath, the steel tape armor, the inner sheath and the copper shielding layer of the control cable to form a ladder shape, and confirming that each stripping cut is clear in level, flat and smooth to avoid damaging the insulating layer of the control cable;

s3 manufacturing a shielded ground wire

S3.1, stripping partial insulating skins of the first grounding wire and the second grounding wire, exposing copper wires, winding the copper wires of the first grounding wire on a steel strip armor, and welding the ends of the wound copper wires of the first grounding wire on the steel strip armor; winding a copper wire of a second grounding wire on the copper shielding layer, welding the end of the copper wire of the wound second grounding wire on the copper shielding layer, leading out the free ends of the first grounding wire and the second grounding wire towards the same side of the control cable respectively, and connecting the free ends of the first grounding wire and the second grounding wire on the equipotential copper bar and the primary copper bar respectively;

s3.2, respectively wrapping fixed outer skins at the welding position of the first grounding wire and the steel tape armor and the welding position of the second grounding wire and the copper shielding layer, and fixing the welding positions again to prevent virtual connection;

s4: making heat-shrinkable sleeves

S4.1 stripping off the fiber layer

After the grounding wire is welded, stripping off the innermost insulating fiber layer remained on the control cable, and stripping off the rest fillers to expose the wire core;

s4.2, installing an inner thermal shrinkable sleeve

Selecting an internal heat-shrinkable sleeve with a proper specification according to the outer diameter size of the control cable; covering the fiber layer, the copper shielding layer, the inner sheath and the steel tape armor by the inner heat shrinkable sleeve in sequence, performing heat shrinkage on the inner heat shrinkable sleeve by using an electric air cylinder, and fixedly installing the inner heat shrinkable sleeve;

s4.3, installing an external thermal shrinkable sleeve

Selecting an outer heat shrinkable sleeve with a proper specification according to the outer diameter of the control cable; covering the inner heat shrinkable sleeve and part of the outer sheath which is not stripped by the control cable by the outer heat shrinkable sleeve, ensuring that the notches of the inner heat shrinkable sleeve and the outer heat shrinkable sleeve which face the wire core end are flush, then performing heat shrinkage on the outer heat shrinkable sleeve by using an air duct, and fixedly mounting the outer heat shrinkable sleeve;

it should be noted that, when the control cable head is manufactured, in the step S3, in manufacturing the shielding ground wire, the first ground wire and the second ground wire are respectively wound on the steel tape armor and the copper shielding layer, the ends of the first ground wire and the second ground wire are respectively welded after winding, and then the welding position is wrapped with the fixing sheath, wherein the first ground wire and the second ground wire are wound for increasing the contact area between the first ground wire and the second ground wire and the steel tape armor and the copper shielding layer respectively, the welding ends are used for increasing the connection firmness between the first ground wire and the second ground wire and the steel tape armor and the copper shielding layer respectively, the wrapping fixing sheath is used for further improving the connection firmness at the welding position and avoiding the ground wire from generating virtual connection, and the manufacturing method including winding, welding and fixing the sheath improves the connection reliability and the anti-interference capability of the ground wire, the damage to the insulating property of the control cable is avoided, the potential safety hazard in the operation of the control cable is eliminated, meanwhile, the manufacturing process is simple, the requirement on the technical level of operators is low, and the implementation is convenient; and after the first grounding wire and the second grounding wire are welded, the fiber layer is stripped, so that the wire core is protected, and the wire core is prevented from being damaged during welding.

Further, the manufacturing step of peeling off the control cable head in step S2 is as follows:

s2.1 stripping off the outer sheath

Determining stripping and cutting positions of the control cable according to the wiring heights of the cabinet, the screen and the box terminal strip, marking with a pen, and cutting with a knife at the stripping and cutting positions to form transverse circumferential cutting, wherein the cutting is required to be regular; then, longitudinally cutting the cable from the transverse cut to the other end of the control cable, and taking down the outer sheath; the cutter used when the outer sheath of the control cable is stripped is moderate in force and cannot be too violent, so that the shielding layer, the insulating sheath and the core fiber layer of the control cable are prevented from being damaged;

s2.2 stripping steel strip armor

The method comprises the following steps of using a straight screwdriver to pick up the tip position of a steel armor belt, using a wire cutter to clamp the tip position of the steel armor belt, measuring the steel belt armor from the cut of an outer sheath, preferably measuring the length of 10-12 mm, using oblique-nose pliers to rotatably cut the steel armor belt by 360 degrees, stripping the rest of the steel belt armor, wherein the cut is smooth and flat to prevent the control cable from being punctured by uneven cuts;

s2.3, stripping off the inner sheath

Measuring the inner sheath from the steel strip armor cut, preferably measuring the length of 2-3 mm, performing transverse circumferential cutting by using a power knife, longitudinally cutting to the other end of the control cable from the transverse cut, taking down the rest inner sheaths, paying attention to the depth of the held knife during cutting, and ensuring that the cut is orderly and regular along the section direction of the wire core, so as to avoid damaging the copper shielding layer and the fiber layer of the wire core;

s2.4 stripping the copper shielding layer

Twisting the copper shielding layers reversely by hands to break and loosen the copper shielding layers, measuring the copper shielding layers from the notches of the inner sheath, preferably measuring the lengths of 10-12 mm, cutting off the redundant copper shielding layers by using inclined-nose pliers, and taking off the copper shielding layers, wherein the notches of the copper shielding layers are neat to prevent the notches from being uneven and stabbing the fiber layers of the cable core;

s2.5 post-stripping inspection of cables

After the outer sheath, the steel strip armor, the inner sheath and the copper shielding layer of the control cable are sequentially stripped, an operator should perform self-checking on the stripped control cable head, the stripped control cable is guaranteed to be clear in each layer, the cut is smooth and flat, the wire core is not damaged and scratched, the control cable is checked in advance, timely correction is facilitated, loss is reduced, the control cable is checked again after being completely manufactured, and rework and time and labor consumption are required if problems exist.

In order to further improve the connection stability of the ground wire, prevent the virtual connection, and eliminate the potential safety hazard, this embodiment respectively performs the following processing on the copper wires of the first ground wire and the second ground wire in step S3.1:

(a) dividing a copper wire of a first grounding wire into two beams, namely a first copper wire and a second copper wire, reversely winding the first copper wire and the second copper wire on the steel band armor respectively, and screwing and welding the ends of the wound first copper wire and the wound second copper wire on the steel band armor;

(b) and dividing the copper wire of the second grounding wire into two beams, namely a third copper wire and a fourth copper wire, respectively reversely winding the third copper wire and the fourth copper wire on the copper shielding layer, and screwing and welding the ends of the wound third copper wire and the wound fourth copper wire on the copper shielding layer.

It should be noted that the copper wires of the first grounding wire are divided into the first copper wires and the second copper wires, and the first copper wires and the second copper wires are reversely wound on the steel tape armoring, so that the connection between the first grounding wire and the steel tape armoring is more stable, the first grounding wire is not easy to loosen or slide from the steel tape armoring, the connection firmness of the first grounding wire and the steel tape armoring is further improved, the virtual connection between the first grounding wire and the steel tape armoring is avoided, the operation of the control cable is unstable, and the operation of the second grounding wire is the same.

Further, when welding the first ground wire and the second ground wire, the method includes the steps of:

in this embodiment, a 200W soldering iron is preferred for soldering;

(i) during welding, performing heat insulation protection measures on the control cable, respectively inserting heat insulation sheets between the steel strip armor and the inner sheath and between the copper shielding layer and the fiber layer, wherein the insertion depth of the heat insulation sheets is not less than 8mm, and removing the heat insulation sheets after welding is completed; the heat insulation sheet is used for thoroughly separating the steel strip armor from the inner sheath and the copper shielding layer from the wire core respectively, so that heat is only released on the shielding layer in the soldering process, and the inner wire core and the insulating layer are prevented from being damaged;

(ii) after welding is finished and before the thermal shrinkable sleeve is manufactured, a welding worker can perform special intermediate inspection on the control cable according to the concealed engineering requirement according to the welding condition of the grounding wire, so that no welding damage and no deformation of the wire core are ensured, the control cable is confirmed to be intact and firm in welding point, and otherwise, a cable head needs to be manufactured again; the welding post is inspected, so that the defects of the control cable head can be found in time, the control cable head can be modified and re-manufactured in time, and the phenomenon that the control cable head is reworked again after the whole post-manufacturing process is completed is avoided, and time and labor are wasted.

Further, the heat insulation sheet in the embodiment preferably uses bamboo sheets or wood sheets, on one hand, the bamboo sheets and the wood sheets are convenient to process, the manufacturing size of the heat insulation sheet is convenient to adjust according to the size of the control cable, and on the other hand, the heat insulation performance of the bamboo sheets and the wood sheets is good, and the cost is low.

Further, when the thermal shrinkable sleeve is manufactured, the method also comprises the following steps:

before the inner heat-shrinkable sleeve is installed, a plurality of layers of polyvinyl chloride wrapping tapes are wound on the control cable head, and then the inner heat-shrinkable sleeve is installed for further protecting the control cable head, preventing water and moisture and fixing the ground wire.

Further, when the fiber layer is stripped, the fiber layer is measured from the notch of the copper shielding layer, the length of the fiber layer is preferably measured to be 2-3 mm in the embodiment, in addition, the total length from the notch of the outer sheath to the notch of the fiber layer is measured to be less than 30mm, and the allowance is reserved;

further, the length of the inner heat shrinkable sleeve in the embodiment is preferably cut to be 30mm, so that the inner heat shrinkable sleeve completely covers the outer sheath cut to the control cable at the cut section of the fiber layer, the length of the outer heat shrinkable sleeve is preferably cut to be 60mm, so that the outer heat shrinkable sleeve completely covers the inner heat shrinkable sleeve and part of the outer sheath, and the ports of the inner heat shrinkable sleeve and the outer heat shrinkable sleeve facing the wire core are aligned, so that the control cable head is flat and the process is attractive.

Furthermore, the temperature of the head of the inner heat-shrinkable sleeve and the head of the outer heat-shrinkable sleeve is controlled to be 100-120 ℃, so that the control cable head is uniformly heated, and the manufactured control cable head is plump, smooth and attractive in process.

Further, in this embodiment, the free end of the first ground wire is led out from the outer heat shrinkable sleeve towards one end of the outer sheath, and the free end of the second ground wire is led out from the outer heat shrinkable sleeve towards one end of the wire core.

It should be noted that, in this embodiment, the free ends of the first ground wire and the second ground wire may be respectively led out, that is, the free end of the first ground wire on the steel tape armor is led out toward the direction of the outer sheath, the free end of the second ground wire on the copper shielding layer is led out toward the direction of the wire core, and the connection positions of the first ground wire and the second ground wire are respectively connected to the equipotential copper bar and the secondary copper bar of the substation, which is favorable for improving the anti-interference performance of the control cable. Wherein, first earth connection and second earth connection adopt the stranded yellow green annealed copper line that the line diameter is not less than 4mm respectively, guarantee safe in utilization.

In the description of the present invention, it should be understood that if there is an orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", etc. based on the orientation or positional relationship shown in the drawings, it is only for convenience of describing the present invention and simplifying the description, but it is not intended to indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and are not to be construed as limiting the present patent, and the specific meaning of the terms may be understood by those skilled in the art according to specific circumstances. In addition, if there is a description of "first", "second", etc. in an embodiment of the present invention, the description of "first", "second", etc. is for descriptive purposes only and is not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In addition, the meaning of "and/or" appearing throughout is to include three juxtapositions, exemplified by "A and/or B" including either scheme A, or scheme B, or a scheme in which both A and B are satisfied.

It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. This need not be, nor should it be exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention or any other related technical fields directly/indirectly applied thereto shall be included in the protection scope of the present invention.

Claims

1. A manufacturing method of a control cable head is characterized by comprising the following manufacturing steps:

s3, manufacturing a shielding grounding wire:

s4, manufacturing a heat-shrinkable sleeve:

s4.3, installing an outer heat shrinkable sleeve, wherein the outer heat shrinkable sleeve covers the inner heat shrinkable sleeve and part of the outer sheath, and the free ends of the first ground wire and the second ground wire are respectively led out from the port of the outer heat shrinkable sleeve; and (3) respectively processing the copper wires of the first grounding wire and the second grounding wire in the step (S3.1) as follows:

dividing the copper wire of the first grounding wire into two beams, namely a first copper wire and a second copper wire, reversely winding the first copper wire and the second copper wire on the steel strip armor respectively, and screwing and welding the ends of the wound first copper wire and the wound second copper wire on the steel strip armor;

dividing the copper wire of the second grounding wire into two beams, namely a third copper wire and a fourth copper wire, reversely winding the third copper wire and the fourth copper wire on the copper shielding layer respectively, and screwing and welding the ends of the wound third copper wire and the wound fourth copper wire on the copper shielding layer; and when the first grounding wire and the second grounding wire are welded, heat insulation sheets are inserted between the steel tape armor and the inner sheath and between the copper shielding layer and the fiber layer.

2. The method of claim 1, wherein the depth of insertion of the thermal spacers is not less than 8 mm.

3. The method according to claim 2, wherein the heat insulation sheet is a bamboo sheet or a wood sheet.

4. The method for manufacturing a control cable head according to claim 1, further comprising, in step S4.2, the steps of:

5. The method of claim 4, wherein the inner heat-shrinkable sleeve and the outer heat-shrinkable sleeve are mounted at a processing temperature of 100 ℃ to 120 ℃.

6. The method of claim 1, wherein the free end of the first ground wire is routed from the outer heat shrink sleeve toward an end of the outer sheath, and the free end of the second ground wire is routed from the outer heat shrink sleeve toward an end of the core.

7. The method for manufacturing a control cable head according to claim 6, wherein the first ground line and the second ground line respectively employ a plurality of strands of yellow-green annealed copper wires having wire diameters not smaller than 4 mm.

8. The method of claim 1, further comprising the step of manufacturing, in step S3: