JP6228535B2 - Power cable - Google Patents

Description

  The present invention relates to a power cable, and more particularly to a power cable used as a high-voltage underground transmission line.

  The power cable includes, for example, a conductive portion, an insulating layer made of crosslinked polyethylene or the like covering the outer periphery of the conductive portion, and a covering layer made of polyvinyl chloride or the like covering the outer periphery of the insulating layer. Such a power cable is used as, for example, a high-voltage underground transmission line.

  The power cable covering layer contains, for example, stabilizers such as tribasic lead sulfate and lead stearate and lead compounds such as lubricants (for example, Patent Documents 1 to 3).

Japanese Patent Laid-Open No. 06-313147 JP-A-11-120828 JP 2011-228111 A

  However, in consideration of environmental impact, a power cable containing a lead compound in the coating layer is not desirable. On the other hand, a power cable used as a high-voltage underground transmission line is required to have mechanical characteristics (trauma resistance), flame resistance, cold resistance, and the like. Until now, a high-voltage power cable that has excellent environmental characteristics and satisfies various characteristics such as external resistance, flame resistance, and cold resistance has not been realized due to technical barriers.

  An object of the present invention is to provide a power cable that has excellent environmental characteristics and can be used as a high-voltage underground transmission line.

According to a first aspect of the invention,
A power cable used as a high-voltage underground transmission line,
A conductive part;
Covering the outer periphery of the conductive portion, an insulating layer mainly made of crosslinked polyethylene,
Covering the outer periphery of the insulating layer, and comprising a coating layer mainly made of polyvinyl chloride,
A power cable is provided in which the coating layer is lead-free.

According to a second aspect of the invention,
In the coating layer,
A hydrotalcite stabilizer, a lead-free lubricant, a plasticizer, a filler, and a flame retardant are blended so as to complement each other of the damage resistance, flame resistance, and cold resistance of the coating layer. A power cable according to an aspect is provided.

According to a third aspect of the invention,
The coating layer includes a hydrotalcite stabilizer,
The hydrotalcite stabilizer is
Hydrotall represented by the general formula M ²⁺ _1-X M ³⁺ _X (OH ⁻ ) ₂ (CO ₃ ) _{x / 2} · mH ₂ O (where 0 <x <0.5, 0 ≦ m <2) Including sites,
M ²⁺ is at least one of Mg ²⁺ , Fe ²⁺ , Zn ²⁺ , Ca ²⁺ , Li ²⁺ , Ni ²⁺ , Co ²⁺ , and Cu ²⁺ .
The power cable according to the first or second aspect, in which M ³⁺ is at least one of Al ³⁺ , Fe ³⁺ , and Mn ³⁺ is provided.

According to a fourth aspect of the invention,
The power cable according to the third aspect, in which the hydrotalcite is Mg ₄ Al ₂ (OH) ₁₂ (CO ₃ ) · 3H ₂ O, is provided.

According to a fifth aspect of the present invention,
The coating layer includes a lead-free lubricant,
The power cable according to any one of the first to fourth aspects, in which the non-lead-based lubricant includes a fatty acid metal salt.

According to a sixth aspect of the present invention,
The coating layer includes a plasticizer,
The power cable according to any one of the first to fifth aspects, in which the plasticizer includes diisononyl phthalate.

According to a seventh aspect of the present invention,
The coating layer is
100 parts by weight of the polyvinyl chloride,
2 to 5 parts by weight of hydrotalcite stabilizer,
A lead-free lubricant containing 0.3 to 1 part by weight of a fatty acid metal salt;
37.5 parts by weight or more and 45.0 parts by weight or less of a phthalate ester plasticizer having 24 to 28 carbon atoms;
An average particle diameter of 1 μm or more and 1.5 μm or less, and a filler containing 3 to 15 parts by weight of fired clay;
A flame retardant containing at least one of 2 parts by weight or more and 10 parts by weight or less of an antimony compound and a boric acid compound;
A power cable according to any one of the first to sixth aspects is provided.

According to an eighth aspect of the present invention,
The power cable according to any one of the first to seventh aspects, in which the allowable side pressure is 500 kgf / m or more is provided.

According to a ninth aspect of the present invention,
The power cable according to any one of the first to eighth aspects, in which the combustion length is 1200 mm or less from the burner port and the afterflame time is within one hour in the vertical tray combustion test, is provided.

According to a tenth aspect of the present invention,
A power cable according to any one of the first to ninth aspects, wherein a cold resistant temperature measured in accordance with JIS C3005 is −15 ° C. or lower is provided.

According to an eleventh aspect of the present invention,
The power cable according to any one of the first to tenth aspects, wherein the nominal voltage is 66 kV or more and 500 kV or less.

  ADVANTAGE OF THE INVENTION According to this invention, the power cable which has the outstanding environmental characteristic and can be used as a high voltage underground transmission line is provided.

It is sectional drawing orthogonal to the axial direction of the power cable which concerns on one Embodiment of this invention. It is a schematic diagram which shows the mode of installation of an electric power cable. (A) is a schematic diagram which shows the mode of a wound test, (b) is the sectional view on the A-A 'line of (a), (c) is the B section enlarged view of (a).

<Knowledge obtained by the present inventors>
In recent years, lead-free processing has been promoted in various technical fields in consideration of the influence on the environment and the human body. This is no exception for power cables. However, particularly in a power cable used as a high-voltage underground transmission line, there are various technical barriers to lead-free coating layers.

  For example, when the lead layer of the power cable used for a low voltage, low-capacity distribution line or the like having a nominal voltage of 22 kV or 33 kV or less is made lead-free, the power cable is lightweight, so that the cover layer is hardly damaged. Moreover, since it was a low voltage use, even if the coating layer was damaged, the influence was limited. Therefore, it was not required that the coating layer has high damage resistance. As described above, in the power cable having a nominal voltage of 33 kV or less, the test conditions (specifications) to be satisfied are not strict, and thus it was easy to lead-free the coating layer.

  On the other hand, for example, when the cover layer of a high-voltage underground transmission line with a nominal voltage of 66 kV or higher is made lead-free, the conductor portion of the power cable is large and heavy, so that it is damaged when laying in underground facilities. It is easy to receive. Due to the high voltage, even a slight damage has a large effect on the withstand voltage characteristics of the power cable. In order to suppress this, the coating layer of the power cable must have excellent trauma resistance. Moreover, since a power cable is also laid in an urban area, the coating layer is required to have high flame resistance. Power cables are often used in cold regions, and the coating layer must also have sufficient cold resistance such as no cracks or cracks caused by the cold. If the coating layer is made of lead-free material, the cold resistance is particularly insufficient, and it is considered that other properties such as flame retardancy and cold resistance are sacrificed if this is compensated.

  Thus, a covering layer is not provided between a power cable for a low-voltage underground transmission line with a nominal voltage of 33 kV or less and a power cable for a high-voltage underground transmission line with a nominal voltage of 66 kV or more. There is a big difference in terms of test conditions (specifications) that must be met when leaded. In power cables for underground power transmission lines with a nominal voltage of 66 kV or higher, the test conditions (specifications) to be satisfied are severe, and the above technical difficulties arise, so lead-free implementation has not yet been realized. Not done. As in the above-mentioned Patent Documents 1 to 3 and the like, the current mainstream is one in which a stabilizer such as tribasic lead sulfate or a lubricant such as lead stearate is added to the coating layer of the power cable.

  As a result of diligent research, the present inventors have excellent environmental characteristics and can satisfy various characteristics such as trauma resistance, flame retardancy, and cold resistance, and can be used as high-voltage underground power transmission lines. Got a good power cable.

  The present invention is based on such knowledge found by the inventors.

<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 FIG. FIG. 1 is a cross-sectional view orthogonal to the axial direction of the power cable 1 according to the present embodiment.

(Structure overview)
As shown in FIG. 1, the power cable 1 includes a conductive portion 10, an insulating layer 20 that covers the outer periphery of the conductive portion 10, and a covering layer 30 that covers the outer periphery of the insulating layer 20.

  The conductive portion 10 is a conductor formed by twisting a plurality of conductive core wires made of, for example, pure copper (Cu), copper alloy, pure aluminum (Al), or aluminum alloy. An internal semiconductive layer 11 is formed on the outer periphery of the conductive portion 10, that is, between the conductive portion 10 and the insulating layer 20.

  The insulating layer 20 contains, for example, a crosslinked polyethylene as a main component. An outer semiconductive layer 21 and a shielding layer 22 are formed in this order on the outer periphery of the insulating layer 20, that is, between the insulating layer 20 and the covering layer 30. The shielding layer 22 is, for example, a wire shield covered with a plurality of conductive wires such as a soft copper wire, a plurality of wound soft copper tapes, or a metal sheath made of aluminum or stainless steel (having a corrugated outer peripheral surface). A pressing tape 23 is further wound around the outer periphery of the shielding layer 22.

  The covering layer 30 is made of, for example, a covering material (sheath) mainly composed of polyvinyl chloride or the like. The coating material does not contain a lead compound, that is, the coating layer 30 is non-leaded. The lead-free coating layer 30 will be described later.

  As described above, the power cable 1 is, for example, a cross-linked polyethylene insulated vinyl sheathed cable (CV cable), and is configured as, for example, a high-voltage underground transmission line. Specifically, the nominal voltage of the power cable 1 is 66 kV or more and 500 kV or less, for example.

  The power cable 1 is a type having a plurality of conductive portions such as a single-core type having only one conductive portion 10 as shown in FIG. 1 and a triplex type having three conductive portions. It may be.

(Coating layer)
The coating layer 30 contains, for example, polyvinyl chloride (PVC), which is a main component, as a base material (base resin), and contains various additives such as a stabilizer, a lubricant, a plasticizer, a filler, and a flame retardant. ing. As described above, these additives do not contain lead compounds, and the coating layer 30 is non-lead. Here, “non-lead” means that the coating layer 30 has a content higher than the content of inevitable impurities and does not contain lead.

  As stabilizers, lead compounds such as tribasic lead sulfate, tribasic lead maleate, dibasic lead stearate, and dibasic lead phosphite have been frequently used so far. In this embodiment, in order to make the coating layer 30 lead-free, as a stabilizer, the hydrotalcite-type stabilizer containing a hydrotalcite is used, for example.

Hydrotalcite general formula _{^{M 2+ 1-X M 3+ X}} - in _{2 (CO 3) x / 2} · mH 2 O ( provided that, 0 <x <0.5,0 ≦ m <2) (OH) It is a compound represented by a double hydroxide as a main skeleton. M ²⁺ is, for example, at least one of Mg ²⁺ , Fe ²⁺ , Zn ²⁺ , Ca ²⁺ , Li ²⁺ , Ni ²⁺ , Co ²⁺ , and Cu ²⁺ . M ³⁺ is, for example, at least one of Al ³⁺ , Fe ³⁺ , and Mn ³⁺ . Specifically, the hydrotalcite in the present embodiment is, for example, Mg ₄ Al ₂ (OH) ₁₂ (CO ₃ ) · 3H ₂ O in which M ²⁺ and M ³⁺ are Mg and Al, respectively. .

  When the coating layer 30 contains the hydrotalcite-based stabilizer as described above, chlorine desorbed from the polyvinyl chloride can be captured and decomposition of the polyvinyl chloride can be suppressed. Hereinafter, this effect is referred to as “thermal stabilization effect”. Due to the thermal stabilization effect, thermal stability during extrusion and thermal stability during use can be obtained. Specifically, it is possible to suppress so-called “burning” that occurs due to the thermal decomposition of PVC in the extruder during long-time extrusion. Further, by suppressing the occurrence of burns, stable long-time extrusion is possible, and so-called wall thickness fluctuations can be suppressed. In use, it is possible to prevent the PVC from gradually decomposing, oxidizing, or deteriorating due to temperature or ultraviolet rays, and to prevent the PVC from becoming hard and brittle.

  As a lubricant, a lead compound such as lead stearate, which is a fatty acid metal salt, has been often used so far. In the present embodiment, in order to make the coating layer 30 lead-free, for example, a lead-free lubricant such as a fatty acid metal salt containing a metal other than lead or a fatty acid is used as the lubricant. The fatty acid metal salt can also act as a stabilizer.

  Examples of the fatty acid portion of the fatty acid metal salt and the fatty acid as a lubricant include stearic acid and oleic acid. Examples of the metal contained in the fatty acid metal salt include Mg, Al, Zn, Ca and the like.

  In addition, as the lubricant, a polyolefin having a molecular weight of 900 or more and 30000 or less, preferably 2000 or more and 3000 or less may be used. The polyolefin is, for example, polyethylene.

  Examples of the plasticizer include carbon numbers such as diisononyl phthalate (DINP), diisodecyl phthalate (DIDP), di-2-ethylhexyl phthalate (DOP), and the like. From 24 to 28 phthalate ester plasticizers are used. However, di-2-ethylhexyl phthalate is a Class 1 Designated Chemical Substance in the Pollutant Release and Transfer Register (PRTR), which contains diisononyl phthalate and diisodecyl phthalate that are not regulated by PRTR. More preferably.

  The molecules of polyvinyl chloride constituting the coating layer 30 have polarity, and the molecules attract each other strongly, and the intermolecular distance of the polyvinyl chloride is shortened. For this reason, polyvinyl chloride is hard at room temperature and exhibits brittleness against impacts and external forces at low temperatures. Therefore, by adding the plasticizer as described above to the coating layer 30, the plasticizer molecules are interrupted between the polyvinyl chloride molecules, thereby suppressing the proximity of the polyvinyl chloride molecules. Thereby, the coating layer 30 becomes soft and the softness | flexibility at the time of the low temperature of the coating layer 30, ie, cold resistance, can be improved.

  As the filler, for example, baked clay or calcium carbonate is used. When the filler is fired clay, the average particle size of the fired clay is, for example, 1 μm or more and 1.5 μm or less. The average particle size is the particle size at an integrated value of 50% in the particle size distribution determined by the X-ray transmission gravity sedimentation method.

  An inorganic flame retardant is used as the flame retardant. Examples of the inorganic flame retardant include antimony compounds such as antimony trioxide and antimony pentoxide, metal hydroxides such as aluminum hydroxide and magnesium hydroxide, and boric acid compounds such as zinc borate.

  Polyvinyl chloride is inherently highly flame retardant, but the addition of additives such as plasticizers may reduce the flame retardancy. Therefore, by adding a flame retardant as described above, the reduction in flame retardancy can be supplemented.

  The coating layer 30 contains 100 parts by weight of polyvinyl chloride, and these hydrotalcite stabilizers, non-lead lubricants, plasticizers, fillers, and flame retardants are resistant to trauma, flame retardant, and cold resistance. In order to complement each other, the following amounts are blended.

  Here, the blending amount of the stabilizer will be described. Lead-based stabilizers have a remarkable heat-stabilizing effect that suppresses the thermal decomposition of polyvinyl chloride, and even if the amount of the lead-based stabilizer is small, a heat-stabilizing effect can be obtained. . However, as described above, there are concerns about the environmental impact of lead. On the other hand, non-lead stabilizers other than hydrotalcite stabilizers have a small thermal stabilization effect, and in order to obtain a thermal stabilization effect, a large amount of non-lead stabilizers other than the hydrotalcite stabilizer is used. It is necessary to blend in. Increasing the amount of stabilizer added decreases cold resistance. For this reason, in order to ensure cold resistance, it is necessary to increase the compounding quantity of a plasticizer. When the blending amount of the plasticizer is increased, the trauma resistance and flame retardancy are lowered. On the other hand, in this embodiment, by using the hydrotalcite stabilizer, the blending amount of the hydrotalcite stabilizer is smaller than the blending amount of the non-lead stabilizer other than the hydrotalcite stabilizer. Even so, a heat stabilization effect can be obtained, and cold resistance can be ensured without increasing the blending amount of the plasticizer. As a result, the coating layer 30 with improved trauma resistance and flame retardancy can be obtained without using a lead-based stabilizer.

  Specifically, the blending amount of the hydrotalcite stabilizer is, for example, 2 parts by weight or more and 5 parts by weight or less. If the blending amount of the hydrotalcite stabilizer is less than 2 parts by weight, the heat stabilization effect may be insufficient. For this reason, PVC is remarkably decomposed with time due to the high temperature during the extrusion process, so-called scorching and the accompanying thickness fluctuation may occur, and stable production may not be possible. In contrast, the amount of hydrotalcite-based stabilizer added is 2 parts by weight or more, thereby suppressing the decomposition of PVC and maintaining a stable product shape even during long-time continuous extrusion processing. can do. On the other hand, if the amount of the hydrotalcite-based stabilizer exceeds 5 parts by weight, cold resistance may be lowered. On the other hand, when the amount of the hydrotalcite-based stabilizer is 5 parts by weight or less, cold resistance can be ensured while maintaining the thermal stabilization effect.

  The amount of the lead-free lubricant containing the fatty acid metal salt is, for example, 0.3 part by weight or more and 1 part by weight or less. When the blending amount of the lead-free lubricant is less than 0.3 parts by weight, the affinity between the resin composition mainly composed of polyvinyl chloride and the metal surface of the processing machine is large when the coating layer 30 is extruded. Become. For this reason, since the flow of the resin composition on the metal surface of the processing machine is inhibited, the resin composition may partially stay on the metal surface of the processing machine, and the resin composition may be thermally decomposed. There is sex. In addition, it may be difficult to clean the processing machine after the processing is completed. On the other hand, when the blending amount of the lead-free lubricant is 0.3 parts by weight or more, the affinity between the resin composition and the metal surface of the processing machine is increased when the coating layer 30 is extruded. Can be suppressed. Thereby, the residence of the resin composition on the metal surface of the processing machine can be suppressed, and the thermal decomposition of the resin composition can be suppressed. Moreover, it becomes possible to easily clean the processing machine after the processing is completed. On the other hand, if the blending amount of the lead-free lubricant is more than 1 part by weight, the kneading of the resin composition in the processing machine does not work, and the surface state (appearance) of the coating layer 30 may deteriorate. In addition, if the blending amount of the lead-free lubricant is more than 1 part by weight, cold resistance may be lowered. On the other hand, when the blending amount of the lead-free lubricant is 1 part by weight or less, kneading unevenness at the time of synthesizing the resin composition is suppressed, and the surface state and low temperature characteristics (cold resistance) of the coating layer 30 are reduced. Can keep good.

  The blending amount of the phthalate ester plasticizer having 24 to 28 carbon atoms is, for example, 37.5 parts by weight or more and 45.0 parts by weight or less. When the blending amount of the phthalate ester plasticizer is less than 37.5 parts by weight, flame retardancy can be improved, but cold resistance may be lowered. On the other hand, when the blending amount of the phthalate ester plasticizer is 37.5 parts by weight or more, it is possible to improve cold resistance while enhancing flame retardancy. On the other hand, when the blending amount of the phthalate ester plasticizer is more than 45.0 parts by weight, the trauma resistance may be lowered. In addition, since the plasticizer itself is flammable, flame retardancy may be reduced. On the other hand, when the blending amount of the phthalate ester plasticizer is 45.0 parts by weight or less, it is possible to suppress the deterioration of the trauma resistance and to reduce the flame retardancy. Can be suppressed.

  The blending amount of the filler containing fired clay having an average particle size of 1 μm or more and 1.5 μm or less is, for example, 3 parts by weight or more and 15 parts by weight or less. When the blending amount of the filler is less than 3 parts by weight, cold resistance can be improved, but flame retardancy and insulation resistance may be lowered. On the other hand, when the blending amount of the filler is 3 parts by weight or more, it is possible to suppress a decrease in flame resistance while increasing cold resistance, and to reduce the insulation resistance of the coating layer 30. Can be suppressed. On the other hand, if the blending amount of the filler is more than 15 parts by weight, cold resistance may be lowered. On the other hand, cold resistance can be ensured when the blending amount of the filler is 15 parts by weight or less.

  For reference, in the conventional coating layer, the blending amount of the filler was larger than the blending amount of the filler of the present embodiment (in many cases, the blending amount of the filler is 20 parts by weight or more and 50 parts by weight or less. Met). As a result, in the conventional coating layer, the flame retardancy is slightly improved, and in many cases, cost merit is obtained. However, in the conventional blending amount of the filler, since the cold resistance is lowered, it is necessary to add many plasticizers. For this reason, conventionally, there has been a tendency for the damage resistance to decrease due to an increase in the amount of plasticizer. In this case, since the flame retardancy is reduced by increasing the amount of the plasticizer, the effect of improving the flame retardancy due to the increase in the filler content was offset. Therefore, in this case, it was necessary to increase the amount of flame retardant. On the other hand, in this embodiment, it can suppress that cold resistance falls because the compounding quantity of a filler is 3 weight part or more and 15 weight part or less. Therefore, it is not necessary to increase the blending amount of the plasticizer to such an extent that the damage resistance and the flame retardancy are concerned.

  Moreover, the compounding quantity of the flame retardant containing at least any one of an antimony compound and a boric acid compound is 2 to 10 weight part, for example. If the blending amount of the flame retardant is less than 2 parts by weight, the flame retardancy may be insufficient. On the other hand, desired flame retardance can be obtained when the blending amount of the flame retardant is 2 parts by weight or more. On the other hand, when the blending amount of the flame retardant exceeds 10 parts by weight, uneven distribution and poor dispersion of each component in the coating layer 30 are likely to occur. In addition, quality variations tend to occur, and the resistance to external damage tends to decrease. On the other hand, each component in the coating layer 30 can be uniformly dispersed when the blending amount of the flame retardant is 10 parts by weight or less. Moreover, it can suppress that the dispersion | variation in quality arises and it can suppress that external damage resistance falls.

  In this way, each of the hydrotalcite stabilizer, non-lead lubricant, plasticizer, filler, and flame retardant is the above blending amount, so that each characteristic of trauma resistance, cold resistance, and flame retardancy can be achieved. They can complement each other.

  The power cable 1 can be manufactured as follows, for example.

  For example, the conductive portion 10 is formed by twisting a plurality of conductive core wires made of pure copper, copper alloy, pure aluminum, aluminum alloy, or the like. The raw materials of the internal semiconductive layer 11, the insulating layer 20, and the external semiconductive layer 21 are extruded sequentially or collectively so as to cover the outer periphery of the conductive portion 10. Thereafter, on the outer periphery of the outer semiconductive layer 21, for example, a wire shield covered with conductive wires such as a plurality of annealed copper wires, a plurality of wound annealed copper tapes, or a metal coating made of aluminum or stainless steel, etc. The shielding layer 22 is formed. Next, the pressing tape 23 is wound in an overlapping manner so as to cover the outer periphery of the shielding layer 22. Next, the coating layer 30 made of, for example, polyvinyl chloride is further extruded.

(2) Various characteristics of power cable The trauma resistance required for the coating layer 30 of the power cable 1 will be described with reference to FIG. FIG. 2 is a schematic diagram showing a state in which the power cable 1 is laid.

  As shown in FIG. 2, the power cable 1 is drawn into a human hole 80 from a cable drum 83 disposed in the vicinity of the human hole 80a, for example, and is installed in the vicinity of the human hole 80 or in the human hole 80a. While being pulled by the machine 85 or the wire 2 attached in advance to the distal end portion of the power cable 1, it is drawn into another human hole 80 b or the like via the inside of the conduit 81. The holing machine 85 pulls the power cable 1 by rotating a caterpillar-shaped drive unit sandwiching the power cable 1 with a motor. The wire 2 pulls the power cable 1 by being wound up by a winch 84 disposed in the vicinity of another human hole 80b.

  Thus, when laying the power cable 1 in the underground facility, the covering layer 30 of the power cable 1 is easily damaged by being dragged in the pipe 81, for example. The power cable 1 is required to have high hardness, that is, resistance to external damage, in order to suppress damage and maintain the withstand voltage characteristic or the like at a predetermined value or more.

  In laying underground transmission lines, allowable tension, allowable bending radius, allowable lateral pressure, and the like are managed. The power cable 1 must satisfy these tolerances. The allowable tension is an allowable value of tension generated in the underground power transmission line when being pulled inside the underground facility. The allowable bending radius is an allowable value of the bending radius when the underground power transmission line is bent along a predetermined path in the underground facility. The allowable side pressure is an allowable value of the pressure applied to the side surface of the underground transmission line. When the underground power transmission line is bent, a particularly large lateral pressure is likely to be applied. The allowable side pressure has a close relationship with the hardness of the coating layer 30. If the coating layer 30 is hard, the allowable side pressure increases. In the power cable 1 of the present embodiment, the allowable side pressure is, for example, 500 kgf / m or more. Such allowable side pressure is required in power cables with a nominal voltage of 66 kV or higher, which differs from power cables with a nominal voltage of 33 kV or lower.

  The covering layer 30 of the power cable 1 is also required to have a property that does not ignite due to flame, high heat, or the like, or a property that does not spread even if ignited, that is, flame retardancy.

  The flame retardancy of the power cable 1 can be defined by, for example, a vertical tray combustion test. The vertical tray combustion test is a test method that conforms to the standard IEEE std 383-1980 of the Institute of Electrical and Electronics Engineers (IEEE). The cable which is a sample is arranged in a vertical tray with an interval of 1/2 of the diameter, and the condition of the cable after burning with a burner for 20 minutes is evaluated. This combustion test is conducted three times. In any case, if the cable combustion length is 1200 mm or less from the burner port and the afterflame time is within about 1 hour, it is determined as acceptable. The power cable 1 of this embodiment is provided with the flame retardance which can pass such a vertical tray combustion test.

  The covering layer 30 of the power cable 1 is also required to have a property that does not crack or break due to cold, that is, cold resistance.

  The cold resistance of the power cable 1 can be defined at a cold resistant temperature based on JIS C3005, for example. In the power cable 1 of this embodiment, the cold-proof temperature measured based on JIS C3005 is -15 degrees C or less.

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

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

(1) Manufacture of power cables of Examples and Comparative Examples Power cables according to Examples in which the coating layer was lead-free and power cables according to Comparative Examples were manufactured. The composition of the coating layer with which the electric power cable of an Example and a comparative example is provided to the following Tables 1-3 is shown.

In the table, HT-1 which is a stabilizer manufactured by Sakai Chemical Industry Co., Ltd. has hydrotalcite (Mg ₄ Al ₂ (OH) ₁₂ (CO ₃ ) · 3H ₂ O) as a main component and contains a lubricant. Absent.

  As shown in Tables 1 and 2, in Examples 1 to 23, the blending amount of the phthalate ester plasticizer is 37.5 parts by weight or more and 45.0 parts by weight or less, and the hydrotalcite stabilizer is used. The blending amount is 2 parts by weight or more and 5 parts by weight or less, the blending amount of the non-lead-based lubricant is 0.3 parts by weight or more and 1 part by weight or less, the blending amount of the filler made of fired clay is 3 parts by weight or more and 15 parts by weight or less, The blending amount of the flame retardant containing at least one of antimony trioxide and zinc borate was set to 2 parts by weight or more and 10 parts by weight or less.

  On the other hand, as shown in Table 3, power cables according to Comparative Examples 1 to 11 were manufactured. In the power cables according to Comparative Examples 1, 2, and 6 to 11, a lead-based stabilizer or a lead-based lubricant was used. In Comparative Examples 2 to 11, the blending amount of at least one of the stabilizer, the lubricant, the filler, and the flame retardant was out of the predetermined range.

(2) Evaluation The power cables of the examples and comparative examples manufactured as described above were evaluated as follows.

(Traumatic)
FIG. 3A is a schematic diagram showing a state of the trauma test, FIG. 3B is a cross-sectional view taken along the line AA ′ in FIG. 3A, and FIG. 3C is an enlarged view of a portion B in FIG. As shown in FIGS. 3 (a) and 3 (b), the power cable 1 heated at about 40 ° C. for 2 hours or more is placed on the test bench 83 via the cable receiving portion 82 that simulates a pipe line. Two were mounted. The power cable 1 was moved at a speed of 10 m / min while the load 81 was evenly placed on the two power cables 1 over 1.5 m. Damage conditions such as peeling of the covering layer 30 when the power cable 1 moved through the cable receiving portion 82 were confirmed. At this time, the load 81 was set to 8.83 kN (900 kgf), 11.8 kN (1200 kgf), and 14.7 kN (1500 kgf). Moreover, as shown in FIG.3 (c), the cable receiving part 82 used height chamfered about 8 mm in height, and the corner | angular part in a cross section about 1-2 mm. The case where peeling or a crack was not confirmed by the upper limit of the load 81 was set as pass, and the case where peeling or a crack was confirmed was set as failure.

(Flame retardance)
In accordance with IEEE std 383-1980, as described above, the cable as a sample was placed in a vertical tray with a space of 1/2 the diameter, and burned with a burner for 20 minutes to burn the cable. The condition was evaluated. This combustion test was conducted three times. In all cases, if the cable combustion length was 1200 mm or less from the burner port and the afterflame time was within about 1 hour, the test was considered acceptable.

(Cold resistance)
In accordance with JIS C3005, a test piece equivalent to the coating layer 30 was prepared, and after immersing the test piece in a medium at a predetermined temperature for a predetermined time, it was examined whether or not it was destroyed. If the temperature at the time of destruction was −15 ° C. or lower, it was determined to be acceptable.

(3) Results Comparative Example 1 and Examples 1 to 23 are compared. In the power cable according to Comparative Example 1, the trauma resistance by the trauma test, the flame retardancy by the vertical tray combustion test, and the cold resistance were acceptable. In Comparative Example 1, due to the blending amount of the filler being more than 15 parts by weight, the cold resistance sometimes failed in several cold resistance tests among a plurality of times. On the other hand, in the power cables according to Examples 1 to 23, the trauma resistance by the trauma test, the flame retardance by the vertical tray combustion test, and the cold resistance were acceptable. That is, it confirmed that the electric power cable which concerns on Examples 1-23 comprised with the non-lead type compound had the characteristic more than equivalent to the comparative example 1 containing a lead compound.

  Next, Examples 1 to 23 and Comparative Examples 5 and 10 are compared with respect to the blending amount of the phthalate ester plasticizer. In Comparative Example 10 in which the amount of the plasticizer was less than 37.5 parts by weight, the cold resistance was unacceptable. On the other hand, in Comparative Example 5 in which the blending amount of the plasticizer exceeds 45.0 parts by weight, the cold resistance is improved so as to compensate for the cold resistance that has been lowered due to the blending amount of the lubricant exceeding 1 part by weight. However, the trauma resistance was unacceptable. On the other hand, in Examples 1-23, when the compounding quantity of a plasticizer is 37.5 weight part or more and 45.0 weight part or less, while improving cold resistance, trauma resistance falls. It was confirmed that it could be suppressed.

  Next, Examples 1 to 23 and Comparative Examples 2 and 11 are compared with respect to the blending amount of the hydrotalcite-based stabilizer. In Comparative Example 2 in which the blending amount of the stabilizer was less than 2 parts by weight, it was difficult to extrude for a long time because a heat stabilizing effect was not obtained (for example, burns occurred). On the other hand, in Comparative Example 11 in which the blending amount of the stabilizer exceeded 5 parts by weight, the cold resistance was unacceptable. On the other hand, in Examples 1 to 23, when the blending amount of the stabilizer is 2 parts by weight or more and 5 parts by weight or less, the extrusion can be stably performed for a long time due to the thermal stabilization effect, and the cold resistance is improved. It was confirmed that it was possible to suppress the decrease.

  Next, Examples 1-23 and Comparative Examples 2-5 are compared about the compounding quantity of a lubricant. In Comparative Examples 2 to 4 in which the blending amount of the lubricant was more than 1 part by weight, the cold resistance was unacceptable. In Comparative Example 5, as described above, although the blending amount of the lubricant was more than 1 part by weight, the cold resistance was complemented because the blending amount of the plasticizer was large. On the other hand, in Examples 1 to 23, it was confirmed that the cold resistance could be suppressed from being lowered when the blending amount of the lubricant was 0.3 parts by weight or more and 1 part by weight or less.

  Next, about the compounding quantity of a filler, Examples 1-23 and Comparative Examples 1, 8, and 9 are compared. In Comparative Example 9 in which the blending amount of the filler was less than 3 parts by weight, the flame retardancy was unacceptable. On the other hand, in Comparative Example 8 in which the blending amount of the filler exceeded 15 parts by weight, the cold resistance was unacceptable. In Comparative Example 1, the cold resistance sometimes failed as described above. On the other hand, in Examples 1 to 23, it was confirmed that cold resistance could be improved while suppressing a decrease in flame retardancy.

  Next, about the compounding quantity of a flame retardant, Examples 1-23 and Comparative Examples 6 and 7 are compared. In Comparative Example 7 in which the blending amount of the flame retardant was less than 2 parts by weight, the flame retardancy was unacceptable. On the other hand, in Comparative Example 6 in which the blending amount of the flame retardant was more than 10 parts by weight, the trauma resistance was unacceptable. On the other hand, in Examples 1 to 23, it was confirmed that the flame resistance was improved and the deterioration of the trauma resistance could be suppressed.

  As described above, according to Examples 1 to 23, by adjusting the blending amounts of the hydrotalcite stabilizer, the non-lead lubricant, the plasticizer, the filler, and the flame retardant, the trauma resistance, the cold resistance It was confirmed that each of the properties of fire resistance and flame retardancy could be complemented each other. Moreover, according to Examples 1-23, it was confirmed that it was possible to provide a power cable that had excellent environmental characteristics and could be used as a high-voltage underground transmission line.

DESCRIPTION OF SYMBOLS 1 Electric power cable 10 Conductive part 20 Insulating layer 30 Covering layer 81 Load 82 Cable receiving part 83 Test stand

Claims (7)

A power cable used as an underground transmission line having a nominal voltage of 66 kV to 500 kV ,
From the center to the outer periphery, the conductive portion, the inner semiconductive layer, the insulating layer mainly composed of cross-linked polyethylene, the outer semiconductive layer, the shielding layer, and the outermost layer of the power cable constitute polyvinyl chloride. A coating layer mainly composed of
The coating layer is
100 parts by weight of the polyvinyl chloride,
2 to 5 parts by weight of hydrotalcite stabilizer,
0.3 to 1 part by weight of a lead-free lubricant containing a fatty acid metal salt;
37.5 parts by weight or more and 45.0 parts by weight or less of a phthalate ester plasticizer having 24 to 28 carbon atoms;
3 parts by weight or more and 15 parts by weight or less filler containing fired clay;
2 to 10 parts by weight of a flame retardant containing at least one of an antimony compound and a boric acid compound,
The power cable heated at 40 ° C. for 2 hours or more is placed on a predetermined cable receiving part simulating a pipeline, and a predetermined load is placed on the power cable for 1.5 m, and the speed is increased. The power cable according to claim 1, wherein an allowable lateral pressure at which the covering layer is not damaged is 500 kgf / m or more in a trauma test in which the power cable is moved at 10 m / min . The coating layer does not contain an inorganic oxide, an inorganic hydroxide, or a carbonate other than the hydrotalcite stabilizer, the calcined clay, and the antimony compound.
The power cable according to claim 1. Before Symbol hydrotalcite-based stabilizer,
Hydrotall represented by the general formula M ²⁺ _1-X M ³⁺ _X (OH ⁻ ) ₂ (CO ₃ ) _{x / 2} · mH ₂ O (where 0 <x <0.5, 0 ≦ m <2) Including sites,
M ²⁺ is at least one of Mg ²⁺ , Fe ²⁺ , Zn ²⁺ , Ca ²⁺ , Li ²⁺ , Ni ²⁺ , Co ²⁺ , and Cu ²⁺ .
The power cable according to claim 1 or 2, wherein M ³⁺ is at least one of Al ³⁺ , Fe ³⁺ , and Mn ³⁺ . The _hydrotalcite power cable according to claim 3, wherein the _{Mg 4 Al 2 (OH) 12} (CO 3) a · 3H ₂ O. Before SL plasticizer, power cable according to any one of claims 1 to 4, characterized in that it comprises a diisononyl phthalate. IEEE std. 383-1980 combustion length 1200mm or less from the burner port in the vertical tray combustion test according to the power cable according to any one of claims 1 to 5, after flame time is equal to or is within 1 hour. The power cable according to any one of claims 1 to 6 , wherein a cold resistant temperature measured in accordance with JIS C3005 is -15 ° C or lower.

Images