Non-ohmic composition, cable connection unit, and method for producing cable connection unit

Abstract

A non-ohmic composition comprising a base elastomer and a plurality of non-ohmic particles, wherein, when an electric field intensity applied to the non-ohmic composition is represented by E and the volume resistivity of the non-ohmic composition is represented by ρ, a threshold electric field intensity E is obtained at which the absolute value of the change in the slope of logρ with respect to logE becomes maximum when the non-ohmic composition is uniaxially stretched by 50%. th Relative to E without stretching non-ohmic composition th The present application also provides a cable connection unit and a method for manufacturing the same.

Description

[0001] This application is a divisional application of application No. 2019800871906, filed on October 8, 2019, and entitled “Non-ohmic composition, cable connection unit, and method for manufacturing a cable connection unit.” Technical Field

[0002] The present invention relates to a non-ohmic composition, a cable connection unit, and a method for producing the cable connection unit.

[0003] This patent application claims priority based on Japanese Patent Application No. 2019-006887 filed on January 18, 2019, and incorporates all the contents described in the Japanese Patent Application. Background Art

[0004] In a cable connection structure for connecting a power cable and an overhead transmission line, or for connecting a pair of power cables, a cylindrical cable connection unit for ensuring insulation is fitted onto the distal end of a gradually stripped power cable.

[0005] For example, a non-ohmic resistive layer composed of a composition containing non-ohmic particles (hereinafter referred to as a "non-ohmic composition") can be provided in the cable connection unit. Consequently, when a high electric field is applied, the volume resistivity of the non-ohmic resistive layer decreases, thereby achieving a uniform distribution of the electric field (e.g., Patent Document 1).

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application No. 2000-503454 Summary of the Invention

[0009] According to one embodiment of the present invention, a non-ohmic composition is provided, comprising a base elastomer and a plurality of non-ohmic particles.

[0010] The electric field strength applied to the non-ohmic composition is defined as E, the volume resistivity of the non-ohmic composition is defined as ρ, and the threshold electric field strength at which the absolute value of the slope change of logρ relative to logE becomes the maximum is defined as E. th , E≥E without stretching the non-ohmic composition th When comparing the volume resistivity ρ of the non-ohmic composition within the range of

[0011] The volume resistivity p when the non-ohmic composition is uniaxially stretched by 50% is 50 times or less the volume resistivity p when the non-ohmic composition is not stretched.

[0012] According to another aspect of the present invention, there is provided a non-ohmic composition comprising a base elastomer and a plurality of non-ohmic particles.

[0013] When the electric field intensity applied to the non-ohmic composition is set to E and the volume resistivity of the non-ohmic composition is set to ρ,

[0014] The threshold electric field intensity E at which the absolute value of the change in the slope of logρ with respect to logE becomes maximum when the non-ohmic composition is uniaxially stretched by 50% is th Relative to E without stretching the non-ohmic composition th Less than 1.4 times.

[0015] According to another aspect of the present invention, there is provided a non-ohmic composition comprising a base elastomer and a plurality of non-ohmic particles.

[0016] The plurality of non-ohmic particles are dispersed in the base elastomer in a network-like manner.

[0017] According to another aspect of the present invention, there is provided a cable connection unit, which is a cylindrical cable connection unit in which a power cable is embedded, and includes:

[0018] A cylindrical non-ohmic resistance layer made of a non-ohmic composition, and

[0019] an insulating layer provided so as to cover the outer side of the non-ohmic resistance layer,

[0020] The non-ohmic composition comprises a base elastomer and a plurality of non-ohmic particles.

[0021] The electric field strength applied to the non-ohmic composition is defined as E, the volume resistivity of the non-ohmic composition is defined as ρ, and the threshold electric field strength at which the absolute value of the slope change of logρ relative to logE becomes the maximum is defined as E. th , E≥E without stretching the non-ohmic composition th When comparing the volume resistivity ρ of the non-ohmic composition within the range of

[0022] The volume resistivity p when the non-ohmic composition is uniaxially stretched by 50% is 50 times or less the volume resistivity p when the non-ohmic composition is not stretched.

[0023] According to another aspect of the present invention, there is provided a cable connection unit, which is a cylindrical cable connection unit in which a power cable is embedded, and includes:

[0024] A cylindrical non-ohmic resistance layer made of a non-ohmic composition, and

[0025] an insulating layer provided so as to cover the outer side of the non-ohmic resistance layer,

[0026] The non-ohmic composition comprises a base elastomer and a plurality of non-ohmic particles.

[0027] The plurality of non-ohmic particles are dispersed in the base elastomer in a network-like manner.

[0028] According to another aspect of the present invention, there is provided a method for manufacturing a cable connection unit, the method being a method for manufacturing a cylindrical cable connection unit into which a power cable is embedded, comprising:

[0029] a step of preparing a non-ohmic composition comprising a base elastomer and a plurality of non-ohmic particles;

[0030] A step of forming a cylindrical non-ohmic resistance layer using the non-ohmic composition; and

[0031] forming an insulating layer so as to cover the outer side of the non-ohmic resistance layer;

[0032] In the process of preparing the non-ohmic composition,

[0033] The base elastomer and the plurality of non-ohmic particles are mixed so that: the electric field strength applied to the non-ohmic composition is set to E, the volume resistivity of the non-ohmic composition is set to ρ, and the threshold electric field strength at which the absolute value of the slope change of logρ relative to logE becomes the maximum is set to E. th , E≥E without stretching the non-ohmic composition th When the volume resistivity ρ of the non-ohmic composition is compared within a range of , the volume resistivity ρ when the non-ohmic composition is uniaxially stretched by 50% is 50 times or less relative to the volume resistivity ρ when the non-ohmic composition is not stretched.

[0034] According to another aspect of the present invention, there is provided a method for manufacturing a cable connection unit, the method being a method for manufacturing a cylindrical cable connection unit into which a power cable is embedded, comprising:

[0035] a step of preparing a non-ohmic composition comprising a base elastomer and a plurality of non-ohmic particles;

[0036] A step of forming a cylindrical non-ohmic resistance layer using the non-ohmic composition; and

[0037] forming an insulating layer so as to cover the outer side of the non-ohmic resistance layer;

[0038] In the process of preparing the non-ohmic composition,

[0039] The plurality of non-ohmic particles are dispersed in the base elastomer in a network shape. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] [ Figure 1 ] is an enlarged cross-sectional view of a portion of the non-ohmic composition involved in the first embodiment of the present invention.

[0041] [ Figure 2 ] is a graph showing an example of volume resistivity relative to electric field intensity in the non-ohmic composition involved in the first embodiment of the present invention.

[0042] [ Figure 3 ] is a cross-sectional view showing a cable connection unit according to a first embodiment of the present invention.

[0043] [ Figure 4 ] is a flowchart showing a method for manufacturing a cable connection structure according to a first embodiment of the present invention.

[0044] [ Figure 5 ] is a cross-sectional view showing a cable connection unit according to a second embodiment of the present invention.

[0045] [ Figure 6A ] is a diagram showing an observation image obtained by observing the non-ohmic composition involved in the example using a scanning electron microscope.

[0046] [ Figure 6B ] is a diagram showing an observation image obtained by observing the non-ohmic composition involved in the comparative example using a scanning electron microscope.

[0047] [ Figure 7 ] are graphs showing the frequency of the non-ohmic particles in the non-ohmic compositions of Examples and Comparative Examples relative to the distance between the centers of gravity.

[0048] [ Figure 8 ] is a graph showing the volume resistivity versus electric field intensity in the non-ohmic composition of the example.

[0049] [ Figure 9 ] is a graph showing the volume resistivity versus electric field intensity in the non-ohmic composition of the comparative example. DETAILED DESCRIPTION

[0050] [Problems to be Solved by the Invention]

[0051] An object of the present invention is to provide a technology that can improve the stability of the characteristics of volume resistivity with respect to electric field intensity.

[0052] [Effects of the Invention]

[0053] According to the present invention, the stability of the characteristics of volume resistivity with respect to electric field intensity can be improved.

[0054] [Description of Embodiments of the Invention]

[0055] <Knowledge Acquired by the Inventors>

[0056] First, the knowledge acquired by the present inventors will be described.

[0057] The cable connection unit has an inner diameter slightly smaller than the outer diameter of the power cable and is fitted onto the power cable in an expanded state. The non-ohmic resistance layer, which is cylindrical and covers the outer circumference of the power cable, is circumferentially extended.

[0058] The present inventors have discovered that when a non-ohmic composition constituting a non-ohmic resistive layer is stretched, the characteristic of volume resistivity with respect to electric field intensity (hereinafter also referred to as "E-ρ characteristic") in the non-ohmic composition may change.

[0059] Specifically, when the non-ohmic composition is stretched, stress increases at the interface between the non-ohmic particles and the base elastomer and a gap is generated. When such a gap is generated, adjacent non-ohmic particles separate from each other, and the distance between the non-ohmic particles becomes longer. When the distance between the non-ohmic particles becomes longer, in the process of applying a high electric field to the non-ohmic composition, even if the resistance of the non-ohmic particles decreases, it is difficult to form a low-resistance circuit between the non-ohmic particles. Therefore, the resistance of the non-ohmic composition as a whole remains at a higher state, and the E-p characteristics that the non-ohmic composition itself has cannot be obtained. When the desired E-p characteristics cannot be obtained, in the process of locally applying a high electric field, it may be impossible to evenly distribute the electric field in the non-ohmic resistance layer. As a result, insulation breakdown may occur at the part where a high electric field is locally applied.

[0060] On the other hand, in order to achieve the desired E-ρ characteristics even after stretching the non-ohmic composition, it is conceivable to mix non-ohmic particles at a high concentration. However, mixing non-ohmic particles at a high concentration reduces the entanglement between molecules in the base elastomer. Consequently, the tensile properties and residual elongation characteristics of the non-ohmic composition may be reduced.

[0061] The present inventors have conducted intensive research on the above situation and have found that by appropriately adjusting the dispersion state of the non-ohmic particles in the base elastomer, the E-ρ characteristics of the non-ohmic composition during stretching can be stably maintained.

[0062] The present invention has been accomplished based on the above-mentioned knowledge found by the present inventors.

[0063] <Embodiment of the present invention>

[0064] Next, embodiments of the present invention will be listed and described.

[0065] [1] One embodiment of the present invention relates to a non-ohmic composition comprising a base elastomer and a plurality of non-ohmic particles.

[0066] The electric field strength applied to the non-ohmic composition is defined as E, the volume resistivity of the non-ohmic composition is defined as ρ, and the threshold electric field strength at which the absolute value of the slope change of logρ relative to logE becomes the maximum is defined as E. th , E≥E without stretching the non-ohmic composition th When comparing the volume resistivity ρ of the non-ohmic composition within the range of

[0067] The volume resistivity p when the non-ohmic composition is uniaxially stretched by 50% is 50 times or less the volume resistivity p when the non-ohmic composition is not stretched.

[0068] According to this configuration, the stability of the characteristics of the volume resistivity of the non-ohmic composition with respect to the electric field intensity during stretching can be improved.

[0069] [2] In the non-ohmic composition described in [1] above,

[0070] The threshold electric field strength E when the non-ohmic composition is subjected to 50% uniaxial stretching th Relative to E without stretching the non-ohmic composition th Less than 1.4 times.

[0071] According to this configuration, the stability of the characteristics of the volume resistivity of the non-ohmic composition with respect to the electric field intensity during stretching can be improved.

[0072] [3] Another embodiment of the present invention relates to a non-ohmic composition comprising a base elastomer and a plurality of non-ohmic particles.

[0073] When the electric field intensity applied to the non-ohmic composition is set to E and the volume resistivity of the non-ohmic composition is set to ρ,

[0074] The threshold electric field intensity E at which the absolute value of the change in the slope of logρ with respect to logE becomes maximum when the non-ohmic composition is subjected to 50% uniaxial stretching is th Relative to E without stretching the non-ohmic composition th Less than 1.4 times.

[0075] According to this configuration, the stability of the characteristics of the volume resistivity of the non-ohmic composition with respect to the electric field intensity during stretching can be improved.

[0076] [4] In the non-ohmic composition described in any one of [1] to [3] above,

[0077] When the non-ohmic composition is subjected to 50% uniaxial stretching, E>E th The slope of the straight line portion in the equation E>E is relative to the slope of the straight line portion in the equation E>E when the non-ohmic composition is not stretched. th The slope of the straight line portion in is within ±50%.

[0078] According to this configuration, the stability of the characteristics of the volume resistivity of the non-ohmic composition with respect to the electric field intensity during stretching can be improved.

[0079] [5] In the non-ohmic composition described in any one of [1] to [4] above,

[0080] The plurality of non-ohmic particles are dispersed in the base elastomer in a network-like manner.

[0081] According to this configuration, the stability of the characteristics of the volume resistivity of the non-ohmic composition with respect to the electric field intensity during stretching can be improved.

[0082] [6] Another embodiment of the present invention relates to a non-ohmic composition comprising a base elastomer and a plurality of non-ohmic particles.

[0083] The plurality of non-ohmic particles are dispersed in the base elastomer in a network-like manner.

[0084] According to this configuration, the stability of the characteristics of the volume resistivity of the non-ohmic composition with respect to the electric field intensity during stretching can be improved.

[0085] [7] In the non-ohmic composition described in any one of [1] to [6] above,

[0086] The coefficient of variation of the distance between the centers of gravity of the plurality of non-ohmic particles obtained by the following formula (1) is 0.5 or greater.

[0087] Coefficient of variation = standard deviation / mean value (1)

[0088] According to this configuration, regardless of the stretched state of the non-ohmic composition, variations in the characteristics of the volume resistivity of the non-ohmic composition with respect to electric field intensity can be stably suppressed.

[0089] [8] In the non-ohmic composition described in any one of [1] to [7] above,

[0090] When observing a cross section of the non-ohmic composition, there are a plurality of particle-free regions containing no non-ohmic particles and having a diameter that is 1.5 times or more the volume average particle diameter of the non-ohmic particles.

[0091] According to this configuration, when the non-ohmic composition is stretched, preferential deformation caused by the base elastic body in the particle-free region can be easily generated.

[0092] [9] In the non-ohmic composition described in any one of [1] to [8] above,

[0093] The base elastomer has:

[0094] an elastomer (A) having relatively high compatibility with the non-ohmic particles, and

[0095] The elastomer (B) has relatively low compatibility with the non-ohmic particles.

[0096] The elastomer (A) contains more non-ohmic particles than the elastomer (B) and constitutes a sea phase.

[0097] The elastomer (B) constitutes an island phase.

[0098] According to this configuration, it is possible to stably form a state in which the non-ohmic particles are dispersed in a network in the base elastomer.

[0099]

[10] In the non-ohmic composition described in [9] above,

[0100] The difference between the solubility parameter of the elastomer (A) and the solubility parameter of the elastomer (B) is 0.5 (cal / cm 3 ) 1 / 2 above.

[0101] According to this configuration, it is possible to stably form a state in which the non-ohmic particles are dispersed in a network in the base elastomer.

[0102]

[11] In the non-ohmic composition described in [9] above,

[0103] The elastomer (A) is non-crosslinked,

[0104] The elastomer (B) comprises a cross-linked rubber.

[0105] According to this configuration, the non-ohmic particles can be preferentially dispersed in the elastomer (A).

[0106]

[12] In the non-ohmic composition described in [9] above,

[0107] The elastomer (A) comprises rubber,

[0108] The elastomer (B) comprises a thermoplastic elastomer,

[0109] The melting point of the elastomer (B) is higher than the softening point of the elastomer (A).

[0110] According to this configuration, the non-ohmic particles can be preferentially dispersed in the elastomer (A).

[0111]

[13] In the non-ohmic composition described in [9] above,

[0112] The elastomer (A) and the non-ohmic particles account for 30% or more of the volume of the entire non-ohmic composition.

[0113] According to this configuration, the elastomer (B) can discretely form the island phase, while the elastomer (A) can continuously form the sea phase.

[0114]

[14] In the non-ohmic composition described in [9] above,

[0115] The elastomer (A) and the elastomer (B) are chemically bonded to each other.

[0116] According to this configuration, it is possible to suppress a decrease in interfacial strength due to a difference in solubility parameters between the elastomer (A) and the elastomer (B).

[0117]

[15] Another embodiment of the present invention relates to a cable connection unit, which is a cylindrical cable connection unit in which a power cable is embedded, and has:

[0118] A cylindrical non-ohmic resistance layer made of a non-ohmic composition, and

[0119] an insulating layer provided so as to cover the outer side of the non-ohmic resistance layer,

[0120] The non-ohmic composition comprises a base elastomer and a plurality of non-ohmic particles.

[0121] The electric field strength applied to the non-ohmic composition is defined as E, the volume resistivity of the non-ohmic composition is defined as ρ, and the threshold electric field strength at which the absolute value of the slope change of logρ relative to logE becomes the maximum is defined as E. th , E≥E without stretching the non-ohmic composition th When comparing the volume resistivity ρ of the non-ohmic composition within the range of

[0122] The volume resistivity p when the non-ohmic composition is uniaxially stretched by 50% is 50 times or less the volume resistivity p when the non-ohmic composition is not stretched.

[0123] According to this configuration, the stability of the characteristics of the volume resistivity of the non-ohmic composition with respect to the electric field intensity during stretching can be improved.

[0124]

[16] Another embodiment of the present invention relates to a cable connection unit, which is a cylindrical cable connection unit in which a power cable is embedded, and has:

[0125] A cylindrical non-ohmic resistance layer made of a non-ohmic composition, and

[0126] an insulating layer provided so as to cover the outer side of the non-ohmic resistance layer,

[0127] The non-ohmic composition comprises a base elastomer and a plurality of non-ohmic particles.

[0128] The plurality of non-ohmic particles are dispersed in the base elastomer in a network-like manner.

[0129] According to this configuration, the stability of the characteristics of the volume resistivity of the non-ohmic composition with respect to the electric field intensity during stretching can be improved.

[0130]

[17] Another embodiment of the present invention relates to a method for manufacturing a cable connection unit, which is a method for manufacturing a cylindrical cable connection unit in which a power cable is embedded, comprising:

[0131] a step of preparing a non-ohmic composition comprising a base elastomer and a plurality of non-ohmic particles;

[0132] A step of forming a cylindrical non-ohmic resistance layer using the non-ohmic composition; and

[0133] forming an insulating layer so as to cover the outer side of the non-ohmic resistance layer;

[0134] In the process of preparing the non-ohmic composition,

[0135] The base elastomer and the plurality of non-ohmic particles are mixed so that: the electric field strength applied to the non-ohmic composition is set to E, the volume resistivity of the non-ohmic composition is set to ρ, and the threshold electric field strength at which the absolute value of the slope change of logρ relative to logE becomes the maximum is set to E. th , E≥E without stretching the non-ohmic composition th When the volume resistivity ρ of the non-ohmic composition is compared within a range of , the volume resistivity ρ when the non-ohmic composition is uniaxially stretched by 50% is 50 times or less relative to the volume resistivity ρ when the non-ohmic composition is not stretched.

[0136] According to this configuration, the stability of the characteristics of the volume resistivity of the non-ohmic composition with respect to the electric field intensity during stretching can be improved.

[0137]

[17] Another embodiment of the present invention relates to a method for manufacturing a cable connection unit, which is a method for manufacturing a cylindrical cable connection unit in which a power cable is embedded, comprising:

[0138] a step of preparing a non-ohmic composition comprising a base elastomer and a plurality of non-ohmic particles;

[0139] A step of forming a cylindrical non-ohmic resistance layer using the non-ohmic composition; and

[0140] forming an insulating layer so as to cover the outer side of the non-ohmic resistance layer;

[0141] In the process of preparing the non-ohmic composition,

[0142] The plurality of non-ohmic particles are dispersed in the base elastomer in a network shape.

[0143] According to this configuration, the stability of the characteristics of the volume resistivity of the non-ohmic composition with respect to the electric field intensity during stretching can be improved.

[0144] [Detailed Description of Embodiments of the Invention]

[0145] Next, an embodiment of the present invention will be described below with reference to the accompanying drawings. It should be noted that the present invention is not limited to these examples, but is represented by the claims and is intended to include all changes within the meaning and scope equivalent to the claims.

[0146] <First embodiment of the present invention>

[0147] (1) Non-ohmic composition (elastomer composition)

[0148] The non-ohmic composition of this embodiment is, for example, a material constituting the non-ohmic resistance layer 220 of the cable connection unit 10 described later, and has a characteristic in which the volume resistivity decreases nonlinearly with increasing electric field intensity.

[0149] Here, use Figure 1 The configuration of the non-ohmic composition will be described. Figure 1 This is an enlarged cross-sectional view of a portion of the non-ohmic composition according to this embodiment.

[0150] like Figure 1 As shown, the non-ohmic composition of this embodiment includes, for example, a base elastomer 120 and a plurality of non-ohmic particles 140. The base elastomer 120 is, for example, an elastomer component that constitutes the main component of the non-ohmic composition and forms the matrix (parent phase) of the non-ohmic composition. The non-ohmic particles 140 are, for example, ceramic particles (so-called nonlinear resistor particles) that have a characteristic in which their volume resistivity decreases nonlinearly with increasing electric field strength.

[0151] In the present embodiment, the non-ohmic particles 140 are, for example, dispersed in a reticular manner in the base elastomer 120. "Reticular dispersion" as mentioned herein (for example) refers to that the particle-free regions are discretely distributed between the particle group regions, wherein the particle group regions include the closest particles in a plurality of series connections, and the particle-free regions do not contain particles and are larger than the size of one particle. Each particle-free region becomes a region enclosed by a particle group region, and is not connected to and separated from other adjacent particle-free regions via the particle group region.

[0152] By dispersing the non-ohmic particles 140 in a network, the base elastomer 120 can maintain its inherent elasticity in the particle-free regions outside the networked particle group regions. Furthermore, in the particle group regions, stress at the interface between the base elastomer 120 and the non-ohmic particles 140 can be mitigated, suppressing the formation of gaps. Consequently, when a high electric field is applied to the non-ohmic composition, a low-resistance circuit can be stably formed between the non-ohmic particles. Consequently, even when the non-ohmic composition is stretched, the inherent E-ρ characteristics of the non-ohmic composition can be stably maintained.

[0153] Specifically, in this embodiment, the coefficient of variation (CV) of the distance between the centers of gravity of the non-ohmic particles 140 is, for example, 0.5 or greater. The "coefficient of variation (CV)" here can be obtained by the following formula (1).

[0154] Coefficient of variation (CV) = standard deviation / mean value (1)

[0155] It should be noted that the "distance between centers of gravity" referred to here refers to the distance between the centers of gravity of a plurality of adjacent particles. For example, the distance between centers of gravity is measured using an image analysis method. More specifically, for example, in an observation image obtained by observing a cross-section at a magnification of 2000 times using a scanning electron microscope (SEM), the distance between the centers of gravity of a plurality of adjacent non-ohmic particles 140 is measured as the distance between centers of gravity. The "adjacent particles" referred to here refer to particles that do not include other particles when the centers of gravity of the two particles being the object are connected in a straight line.

[0156] When the coefficient of variation of the distance between the centers of gravity of the non-ohmic particles 140 is less than 0.5, this state corresponds to a state in which the particle-free region is small and the non-ohmic particles 140 are uniformly dispersed.

[0157] In this case, when the non-ohmic composition is stretched, stress is uniformly applied to the entire non-ohmic composition. Therefore, at the interface between the non-ohmic particles and the base elastomer, stress increases, resulting in a gap. As a result, depending on the stretched state of the non-ohmic composition, the E-ρ characteristic of the non-ohmic composition may deviate. In contrast, in the present embodiment, by setting the coefficient of variation of the distance between the centers of gravity of the non-ohmic particles 140 to be greater than 0.5, a state in which the non-ohmic particles 140 are dispersed in a network in the base elastomer 120 can be stably formed. Therefore, at the interface between the base elastomer 120 and the non-ohmic particles 140, stress can be easily relaxed, thereby stably suppressing the generation of gaps. As a result, regardless of the stretched state of the non-ohmic composition, the deviation of the E-ρ characteristic of the non-ohmic composition can be stably suppressed.

[0158] On the other hand, in this embodiment, the coefficient of variation of the distance between the centers of gravity of the non-ohmic particles 140 is preferably 0.8 or less, for example. When the coefficient of variation of the distance between the centers of gravity of the non-ohmic particles 140 exceeds 0.8, this corresponds to a state in which the gaps between the network formed by the non-ohmic particles 140 in the base elastomer 120 are large, resulting in continuous distribution of particle-free regions, or a state in which the non-ohmic particles 140 aggregate and disperse in blocks within the base elastomer 120. In this case, the continuous number of non-ohmic particles 140 formed by contact between the non-ohmic particles 140 may become insufficient. As a result, the non-ohmic composition may fail to exhibit non-ohmic properties. In contrast, in this embodiment, by setting the coefficient of variation of the distance between the centers of gravity of the non-ohmic particles 140 to 0.8 or less, the network formed by the non-ohmic particles 140 in the base elastomer 120 can be prevented from becoming excessively large, thereby preventing continuous distribution of particle-free regions. Alternatively, the non-ohmic particles 140 can be prevented from aggregating and dispersing in blocks within the base elastomer 120. Thus, the non-ohmic composition can stably exhibit non-ohmic properties.

[0159] Furthermore, in this embodiment, for example, when observing a cross-section of the non-ohmic composition, there are multiple particle-free regions that do not contain non-ohmic particles 140 and have a diameter that is at least 1.5 times the volume average particle diameter of the non-ohmic particles 140. When the diameter of the particle-free regions in the cross-sectional view is less than 1.5 times the volume average particle diameter of the non-ohmic particles 140, preferential deformation caused by the base elastomer 120 in the particle-free regions is difficult to produce when the non-ohmic composition is stretched. As a result, gaps may form at the interface between the non-ohmic particles and the base elastomer in the particle group region. As a result, it may be difficult to achieve the effect of suppressing the deviation of the E-ρ characteristic of the non-ohmic composition. In contrast, in this embodiment, by ensuring that the diameter of the particle-free regions in the cross-sectional view is at least 1.5 times the volume average particle diameter of the non-ohmic particles 140, preferential deformation caused by the base elastomer 120 in the particle-free regions can be easily produced when the non-ohmic composition is stretched. This can stably suppress the generation of gaps at the interface between the base elastomer 120 and the non-ohmic particles 140. As a result, the effect of suppressing the variation in the E-ρ characteristic of the non-ohmic composition can be stably obtained.

[0160] It should be noted that the “volume average particle size (MV)” mentioned here refers to the particle size of the particles being d i , the volume of the particle is set to V i When , it is obtained by the following formula.

[0161] MV=Σ(V i d i ) / ΣV i

[0162] The volume average particle size can be measured using a dynamic light scattering particle size / particle size distribution analyzer.

[0163] It should be noted that there is no particular upper limit on the size of the particle-free area in the cross-sectional view, but from the perspective of suppressing stress deviation during stretching, the diameter of the particle-free area in the cross-sectional view is preferably less than 10 times the volume average particle size of the non-ohmic particles 140, for example.

[0164] In the present embodiment, as described above, the non-ohmic particles 140 are dispersed in a network in the base elastomer 120 , and thus the non-ohmic composition has, for example, a phase separation structure.

[0165] Specifically, the base elastomer 120 includes, for example, an elastomer (A) 122 having relatively high compatibility with the non-ohmic particles 140 (a small difference in solubility parameters, described later), and an elastomer (B) 124 having relatively low compatibility with the non-ohmic particles 140 (a large difference in solubility parameters). Specifically, the elastomer (A) 122 and the elastomer (B) 124 have different compatibilities with the non-ohmic particles 140, thereby forming a phase-separated structure.

[0166] For example, by making the elastomer (A) 122 relatively compatible with the non-ohmic particles 140, it is possible to contain more non-ohmic particles 140 than the elastomer (B) 124. Furthermore, the elastomer (A) 122, for example, constitutes a sea phase (continuous phase) while containing the non-ohmic particles 140. That is, the sea phase composed of the elastomer (A) 122 includes, for example, the aforementioned particle group region.

[0167] On the other hand, the elastomer (B) 124, for example, constitutes an island phase (dispersed phase). For example, the island phase composed of the elastomer (B) 124 is made relatively less miscible with the non-ohmic particles 140, thereby including the aforementioned particle-free region. The entire island phase is preferably a particle-free region. It should be noted that at least a portion of the island phase may also contain non-ohmic particles 140. In this case, the non-ohmic particles 140 contained in the island phase are preferably smaller than the non-ohmic particles 140 contained in the aforementioned sea phase.

[0168] As described above, the sea phase composed of the elastomer (A) 122 and the island phase composed of the elastomer (B) 124 can form a state in which the non-ohmic particles 140 are dispersed in a network in the base elastomer 120 .

[0169] Here, the elastomer (A) 122 and the elastomer (B) 124 of the present embodiment have, for example, different solubility parameters from each other.

[0170] It should be noted that the solubility parameter (SP value) is a value defined by the normal solution theory derived by Hildebrand, which serves as a standard for the solubility of two components. 3 The square root of the heat of vaporization required for the liquid (cal / cm 3 ) 1 / 2 It should be noted that the solubility parameter can be calculated by the Fedors method (Polymer engineering and science, vol. 14, p. 152). When the difference in solubility parameters between two components is small, it means that the two components are highly compatible with each other.

[0171] In this embodiment, the difference between the solubility parameter of the elastomer (A) 122 and the solubility parameter of the elastomer (B) 124 is, for example, 0.5 (cal / cm 3 ) 1 / 2 Above, preferably 1.0 (cal / cm 3 ) 1 / 2 When the difference in solubility parameters is less than 0.5 (cal / cm 3 ) 1 / 2 In contrast, in this embodiment, by setting the difference in solubility parameters to 0.5 (cal / cm 3 ) 1 / 2 As a result, a phase separation structure can be stably formed. Therefore, a state in which the non-ohmic particles 140 are dispersed in a network in the base elastomer 120 can be stably formed. In addition, by setting the difference in solubility parameters to 1.0 (cal / cm 3 ) 1 / 2 As described above, the non-ohmic particles 140 can be more stably dispersed in a network in the base elastic body 120 .

[0172] It should be noted that the upper limit of the difference between the solubility parameter of the elastomer (A) 122 and the solubility parameter of the elastomer (B) 124 is not particularly limited, but is preferably 2.5 (cal / cm 3 ) 1 / 2 The difference in solubility parameters is greater than 2.5 (cal / cm 3 ) 1 / 2 In this case, when the non-ohmic composition is stretched, peeling is likely to occur at the interface between the elastomer (A) 122 and the elastomer (B) 124, and mechanical properties may not be exhibited.

[0173] It should be noted that, in this embodiment, it is preferred that the solubility parameter of the elastomer (B) 124 , the solubility parameter of the elastomer (A) 122 , and the solubility parameter of the non-ohmic particles 140 increase in this order.

[0174] Specifically, the solubility parameter of the non-ohmic particles 140 is, for example, 12.0 (cal / cm 3 ) 1 / 2 Above 20.0 (cal / cm 3 ) 1 / 2 The solubility parameter of the elastomer (A) 122 is, for example, 8.0 (cal / cm 3 ) 1 / 2 Above 11.5 (cal / cm 3 ) 1 / 2 The solubility parameter of the elastomer (B) 124 is, for example, 7.0 (cal / cm 3 )1 / 2 Above 9.0 (cal / cm 3 ) 1 / 2 The materials are selected so that the solubility parameters satisfy the above-mentioned magnitude relationship within the above-mentioned ranges, thereby stably forming the above-mentioned phase separation structure.

[0175] In addition, in the present embodiment, the elastomer (A) 122 and the non-ohmic particles 140, for example, account for more than 30% of the volume of the entire non-ohmic composition. When the volume occupied by the elastomer (A) 122 and the non-ohmic particles 140 is less than 30% of the entire non-ohmic composition, the elastomer (A) is discretely distributed and cannot form a sea phase. Therefore, it is difficult to form a state in which the non-ohmic particles 140 are dispersed in a network in the base elastomer 120. In contrast, in the present embodiment, by setting the volume occupied by the elastomer (A) 122 and the non-ohmic particles 140 to more than 30% of the entire non-ohmic composition, the sea phase can be continuously formed by the elastomer (A) 122 while the island phase is discretely formed by the elastomer (B) 124. Therefore, a state in which the non-ohmic particles 140 are dispersed in a network in the base elastomer 120 can be stably formed. As a result, the effect of suppressing the deviation of the E-ρ characteristic of the non-ohmic composition can be stably obtained.

[0176] On the other hand, in the present embodiment, the elastomer (A) 122 and the non-ohmic particles 140, for example, preferably account for a volume of less than 70% of the non-ohmic composition as a whole. When the volume occupied by the elastomer (A) 122 and the non-ohmic particles 140 exceeds 70% of the non-ohmic composition as a whole, the island phase composed of the elastomer (B) becomes too small. Therefore, in the case of stretching the non-ohmic composition, it is difficult to produce the preferential deformation caused by the elastomer (B). As a result, it may be difficult to obtain the effect of suppressing the deviation of the E-ρ characteristic of the non-ohmic composition. In contrast, in the present embodiment, by setting the volume occupied by the elastomer (A) 122 and the non-ohmic particles 140 to less than 70% of the non-ohmic composition as a whole, the island phase composed of the elastomer (B) can be suppressed from being too small. Therefore, in the case of stretching the non-ohmic composition, the preferential deformation caused by the elastomer (B) can be easily produced. As a result, the effect of suppressing the deviation of the E-ρ characteristic of the non-ohmic composition can be stably obtained.

[0177] Furthermore, in this embodiment, elastomer (A) 122 and elastomer (B) 124 are chemically bonded to each other, for example. Elastomer (A) 122 and elastomer (B) 124 are cross-linked using at least one cross-linking agent, such as sulfur and an organic peroxide. This can suppress a decrease in interfacial strength caused by differences in solubility parameters between elastomer (A) 122 and elastomer (B) 124. Consequently, the residual stretch of the non-ohmic composition can be reduced, and prolonged stress relaxation can be suppressed.

[0178] In this embodiment, the elastic body (A) 122 and the elastic body (B) 124 both have insulating properties. Specifically, the volume resistivity of the elastic body (A) 122 and the elastic body (B) 124 is, for example, 1.0×10 9 Thus, when a low electric field is applied, the predetermined insulating properties of the non-ohmic composition can be obtained.

[0179] In addition, in this embodiment, the elastic modulus of the elastomer (B) 124 is preferably lower than the elastic modulus of the elastomer (A) 122. This facilitates preferential deformation of the elastomer (B) when the non-ohmic composition is stretched, thereby suppressing stress concentration in the elastomer (A).

[0180] Examples of the elastomer (A) that satisfies the above conditions include ethylene propylene rubber (EPR), ethylene propylene diene rubber (EPDM), styrene butadiene rubber (SBR), epichlorohydrin rubber (CO), chloroprene rubber (CR), chlorosulfonated polyethylene rubber (CSM), nitrile rubber (NBR), acrylic rubber (ACM), ethylene acrylic rubber (AEM), ethylene-vinyl acetate copolymer (EVM), and urethane rubber (U).

[0181] In addition, examples of the elastomer (B) that meets the above conditions include fluororubber (FKM), silicone rubber (Q), ethylene propylene rubber (EPR), ethylene propylene diene rubber (EPDM), styrene butadiene rubber (SBR), epichlorohydrin rubber (CO), and chloroprene rubber (CR).

[0182] It should be noted that by using an elastomer that satisfies both the above-mentioned conditions of elastomer (A) and elastomer (B), such as a pair of elastomers such as EPR, EPDM, SBR, CO, CR, etc., either a sea phase containing a large number of non-ohmic particles 140 or an island phase containing particle-free areas can be formed.

[0183] Specifically, for example, when silicone rubber (SP value: 7.3) is used as the elastomer (B), EPDM (SP value: 8.0) can be used as the elastomer (A), but when an elastomer with a higher SP value (U, etc.) is used as the elastomer (A), EPDM can be used as the elastomer (B).

[0184] Furthermore, the non-ohmic particles 140 used in this embodiment have, for example, crystalline portions and grain boundary portions. When an electric field with a strength below the critical electric field is applied, the grain boundary portions exhibit high resistance, and the non-ohmic particles 140 function as insulators. On the other hand, when an electric field exceeding the critical electric field strength is applied, current flows through the grain boundary portions between a pair of adjacent crystalline portions, and the non-ohmic particles 140 function as conductors.

[0185] The crystalline portion of the non-ohmic particle 140 contains, for example, at least one of zinc oxide, silicon carbide, strontium titanate, and barium titanate. When the crystalline portion of the non-ohmic particle 140 is primarily composed of zinc oxide, the grain boundary portion of the non-ohmic particle 140 contains, for example, an oxide containing at least one of bismuth, antimony, manganese, cobalt, and nickel.

[0186] In addition, in the present embodiment, the maximum particle size of the non-ohmic particles 140 is not particularly limited, and is, for example, less than 30 μm, preferably less than 10 μm. By setting the maximum particle size of the non-ohmic particles 140 to less than 30 μm, the dielectric breakdown electric field strength of the non-ohmic composition can be improved. In addition, by setting the maximum particle size of the non-ohmic particles 140 to less than 30 μm, the dielectric breakdown electric field strength of the non-ohmic composition can be stably improved. It should be noted that the lower limit of the maximum particle size of the non-ohmic particles 140 is not particularly limited, but from the perspective of stably obtaining the desired non-ohmic properties, it is 1.5 μm.

[0187] In addition, in this embodiment, the amount of non-ohmic particles 140 in the non-ohmic composition can be appropriately adjusted according to the properties required of the non-ohmic composition. Specifically, the volume ratio of the non-ohmic particles 140 to the base elastomer 120 is preferably, for example, not less than 0.1 and not more than 0.5. By setting the volume ratio of the non-ohmic particles 140 to the base elastomer 120 to not less than 0.1, the predetermined E-ρ characteristics of the non-ohmic composition can be stably obtained. On the other hand, by setting the volume ratio of the non-ohmic particles 140 to the base elastomer to not more than 0.5, the predetermined tensile properties of the non-ohmic composition can be stably obtained.

[0188] In this embodiment, the non-ohmic particles 140 can be surface-treated using, for example, a silane coupling agent. Specifically, trimethoxyvinylsilane, triethoxyvinylsilane, methyldimethoxyvinylsilane, and the like can be used as the silane coupling agent. This allows for adjustment of the dispersibility of the particles in the elastomer (A) 122, thereby effectively forming a particle-free region. As a result, the desired E-ρ characteristics of the non-ohmic composition can be exhibited.

[0189] It should be noted that other additives may be appropriately added to the non-ohmic composition, such as a cross-linking agent, an antioxidant, a plasticizer, and the like.

[0190] (Characteristics of non-ohmic compositions)

[0191] Next, use Figure 2 The characteristics exhibited by the non-ohmic composition of this embodiment will be described. Figure 2 This is a graph showing an example of volume resistivity versus electric field intensity in the non-ohmic composition according to the present embodiment.

[0192] It should be noted that the electric field intensity is set as E and the volume resistivity is set as ρ. In addition, the point where the absolute value of the change in the slope of logρ relative to logE becomes the largest is set as the "decline starting point", wherein the decline starting point in the case of no stretching of the non-ohmic composition is set as "P1", and the decline starting point in the case of 50% uniaxial stretching of the non-ohmic composition is set as "P2". It should be noted that the "slope of logρ relative to logE" mentioned here can also be referred to as "the slope of ρ relative to E when E and ρ are plotted in a double logarithmic graph". In addition, the electric field intensity E at the decline starting point is set as the "threshold electric field intensity E". th ”, where the threshold electric field intensity E at the drop starting point P1 without stretching the non-ohmic composition is th The threshold electric field intensity E at the drop start point P2 when the non-ohmic composition is subjected to 50% uniaxial stretching is defined as “E1”. th Set to "E2".

[0193] As described above, in this embodiment, by dispersing the non-ohmic particles 140 in a network form in the base elastomer 120 , the E-ρ characteristic inherent in the non-ohmic composition can be stably maintained even when the non-ohmic composition is stretched.

[0194] Specifically, if Figure 2 As shown, in this embodiment, when the volume resistivity ρ of the non-ohmic composition is compared in the range of E≥E1 when the non-ohmic composition is not stretched, the volume resistivity ρ when the non-ohmic composition is subjected to 50% uniaxial stretching is, for example, 50 times or less, and preferably 20 times or less, relative to the volume resistivity ρ when the non-ohmic composition is not stretched.

[0195] In this embodiment, the threshold electric field intensity E2 at the drop starting point P2 when the non-ohmic composition is subjected to 50% uniaxial stretching is, for example, 1.4 times or less, preferably 1.2 times or less, relative to the threshold electric field intensity E1 at the drop starting point P1 when the non-ohmic composition is not stretched.

[0196] The lower limit of the ratio of E2 to E1 is not particularly limited, but the ratio of E2 to E1 is, for example, preferably 0.6 times or more, more preferably 0.8 times or more, and even more preferably 1.0 times or more.

[0197] In addition, in this embodiment, the slope of the straight line portion in E>E2 when the non-ohmic composition is subjected to 50% uniaxial stretching is within ±50%, preferably within ±30%, relative to the slope of the straight line portion in E>E1 when the non-ohmic composition is not stretched.

[0198] It should be noted that the "E>E th The slope of the straight line in the equation "is the slope of the straight line in the equation" means (for example) when E>E th In the range of , when the least square method is used to approximate a plurality of consecutive measurement points, the correlation coefficient becomes a slope within the range of -0.99 or less. In addition, when calculating "E>E th The upper limit of E in the case of the slope of the straight line portion in the equation "is an arbitrary value and is not particularly limited, but is, for example, 3E th , preferably 2E th .

[0199] (2) Cable connection unit

[0200] use Figure 3 The cable connecting unit according to this embodiment will be described. Figure 3 It is a cross-sectional view showing the cable connection unit according to the present embodiment.

[0201] Hereinafter, the "axial direction" of the power cable (not shown) or the cable connection unit 10 refers to the direction of the central axis of the power cable or the cable connection unit 10, and may also be referred to as the "direction along the layer" or the "longitudinal direction". It should be noted that the axial direction of the cable connection unit 10 may also be referred to as the axial direction of the hollow portion 202. In addition, the "radial direction" of the power cable or the cable connection unit 10 refers to the direction from the central axis of the power cable or the cable connection unit 10 toward the periphery, and in some cases may also be referred to as the "thickness direction" or the "transverse direction".

[0202] In addition, hereinafter, among the axial ends of the cable connection unit 10, the end on the side where the front end of the power cable is arranged will be referred to as the "front end", and the end on the side opposite to the front end of the power cable (extension side) will be referred to as the "rear end".

[0203] like Figure 3 As shown, the cable connection unit (cable terminal connection unit) 10 of this embodiment is configured in a cylindrical shape, for example, so that the power cable can be inserted in. This can alleviate the electric field outside the power cable and ensure insulation.

[0204] The cable connection unit 10 of this embodiment is configured as a cable terminal connection structure (aerial terminal connection portion) for connecting a power cable to an overhead transmission line (not shown), for example. In this cable terminal connection structure, for example, the cable connection unit 10 is externally fitted onto the outer circumference of a progressively stripped power cable. The power cable is then inserted into a porcelain tube (not shown), which is then filled with an insulating medium. The insulating medium is, for example, insulating oil or insulating gas.

[0205] It should be noted that the power cable mentioned here is constructed as a so-called CV cable (Cross linkedpolyethylene insulated PVC sheathed cable, also known as XLPE cable), for example, from the center axis toward the periphery it has: a cable conductor (not shown), an internal semi-conductive layer of the cable (not shown), a cable insulation layer (not shown), an external semi-conductive layer of the cable (not shown), a cable metal skin (not shown) and a cable sheath (not shown).

[0206] like Figure 3 As shown, the cable connection unit 10 of this embodiment includes, for example, a non-ohmic resistance layer (FGM layer: Field Grading Material Layer) 220 , a semiconductive tapered portion (semiconductive portion, stress tapered portion) 240 , and an insulating layer 260 .

[0207] (Non-ohmic resistance layer)

[0208] The non-ohmic resistor layer 220 is composed of, for example, the aforementioned non-ohmic composition including the base elastomer 120 and the plurality of non-ohmic particles 140. In the non-ohmic resistor layer 220, the elastomer (A) 122 and the elastomer (B) 124 are chemically bonded to each other, for example, by crosslinking.

[0209] The non-ohmic resistive layer 220 is, for example, provided in a cylindrical shape to form the hollow portion 202. The non-ohmic resistive layer 220 is, for example, provided continuously over the entire axial length of the cable connection unit 10, and is configured to cover the outer circumferences of the exposed cable insulation layer and the exposed outer semiconductive layer of the cable when the power cable is embedded in the hollow portion 202.

[0210] The inner diameter of the hollow portion 202 formed by the non-ohmic resistor layer 220 is, for example, slightly smaller than the outer diameter of the power cable. The non-ohmic resistor layer 220 is fitted onto the power cable in an expanded state and circumferentially stretched. This elastically fits the power cable within the hollow portion 202, ensuring a tight, hermetically sealed connection to the inner circumference of the non-ohmic resistor layer 220.

[0211] When the power cable is embedded in hollow portion 202, the rear end of cable connection unit 10 in non-ohmic resistance layer 220 contacts the cable's outer semiconductive layer, thereby being grounded. Meanwhile, the front end of cable connection unit 10 in non-ohmic resistance layer 220 is at substantially the same potential as the cable conductor of the power cable, i.e., at a higher potential.

[0212] In this embodiment, the non-ohmic resistance layer 220 is configured to form the hollow portion 202 and to cover the cable insulation layer. This reduces the resistance of the non-ohmic resistance layer 220 when a local electric field concentration occurs at the front end of the cable connection unit 10, where the cable insulation layer of the power cable, the insulation layer 260 of the cable connection unit 10, and the insulating medium filling the porcelain tube are close (also known as a triple point). Thus, when observing a cross-section along the axial direction of the cable connection unit 10, equipotential lines are evenly distributed (dispersed) within the non-ohmic resistance layer 220 from the front end toward the rear end of the cable connection unit 10. As a result, the electric field concentration at the front end of the cable connection unit 10 can be mitigated, thereby reducing electrical risks such as insulation breakdown.

[0213] (Semi-conductive tapered portion)

[0214] The semi-conductive tapered portion 240 has, for example, semi-conductivity. Specifically, the semi-conductive tapered portion 240 includes, for example, semi-conductive rubber. The semi-conductive rubber is, for example, a composition containing ethylene propylene rubber or silicone rubber and carbon black.

[0215] The semiconductive conical portion 240 is, for example, configured in a conical shape (a trumpet shape) to form a so-called stress cone. Specifically, the semiconductive conical portion 240 is, for example, arranged on the outer side of the non-ohmic resistance layer 220 in the radial direction of the cable connection unit 10. In addition, the axial rear end side of the cable connection unit 10 in the semiconductive conical portion 240 may, for example, be in contact with the non-ohmic resistance layer 220 or may be separated. In addition, the semiconductive conical portion 240 has, for example, an inclined surface 242, which is inclined in a manner that gradually moves away from the non-ohmic resistance layer 220 from the portion close to the non-ohmic resistance layer 220 toward the axial front end side of the cable connection unit 10. Therefore, when observing the cross-section along the axial direction of the cable connection unit 10, equipotential lines can be formed along the inclined surface 242 of the semiconductive conical portion 240, and the equipotential lines can be evenly distributed.

[0216] (Insulation layer)

[0217] The insulating layer 260 has, for example, higher insulating properties than the semi-conductive tapered portion 240. Specifically, the insulating layer 260 includes, for example, insulating rubber, such as ethylene propylene rubber or silicone rubber.

[0218] The insulating layer 260 is provided so as to cover the non-ohmic resistive layer 220 and the semi-conductive tapered portion 240. For example, the insulating layer 260 is provided so as to be embedded between the non-ohmic resistive layer 220 and the inclined surface 242 of the semi-conductive tapered portion 240.

[0219] Furthermore, the insulating layer 260 gradually tapers in diameter as it approaches the axial front end of the cable connection unit 10. As described above, in addition to providing the non-ohmic resistance layer 220, the electric field at the triple point can be further mitigated by gradually tapering the front end of the insulating layer 260 of the cable connection unit 10.

[0220] The non-ohmic resistive layer 220, the semi-conductive tapered portion 240, and the insulating layer 260 described above can be molded, for example, to form an integral part. This facilitates on-site fabrication (construction) of the cable connection structure. Furthermore, on-site fabrication can prevent the formation of gaps between the layers and the infiltration of impurities between the layers. It should be noted that the non-ohmic resistive layer 220, the semi-conductive tapered portion 240, and the insulating layer 260 can also be separate.

[0221] (3) Method for manufacturing a cable connection unit and a method for manufacturing a cable connection structure (cable connection method)

[0222] Next, use Figure 4 A method for manufacturing the cable connection unit and a method for manufacturing the cable connection structure according to the present embodiment will be described. Figure 4 1 is a flow chart showing a method for manufacturing a cable connection structure according to the present embodiment.

[0223] The method for manufacturing the cable connection structure of the present embodiment includes, for example, a cable connection unit fabrication step (cable connection unit manufacturing step) S120 , a power cable preparation step S140 , an embedding step S160 , and a porcelain tube insertion step S180 .

[0224] (S120: Cable Connection Unit Manufacturing Process)

[0225] First, a cylindrical cable connection unit 10 is prepared, comprising a non-ohmic resistive layer 220, a semiconductive tapered portion 240, and an insulating layer 260. The cable connection unit preparation step S120 includes, for example, a non-ohmic composition preparation step S122, a non-ohmic resistive layer formation step S124, a semiconductive tapered portion formation step S126, and an insulating layer formation step S128.

[0226] (S122: Non-ohmic composition preparation step)

[0227] First, the base elastic body 120 and the non-ohmic particles 140 are prepared.

[0228] In this embodiment, as the base elastic body 120 , for example, an elastomer (A) 122 having relatively high compatibility with the non-ohmic particles 140 and an elastomer (B) 124 having relatively low compatibility with the non-ohmic particles 140 are prepared.

[0229] In the present embodiment, so-called non-linear resistor particles having a crystal portion and a grain boundary portion are prepared as the non-ohmic particles 140 .

[0230] After the base elastic body 120 and the non-ohmic particles 140 are prepared, they are mixed (kneaded).

[0231] At this time, in the present embodiment, the non-ohmic particles 140 are dispersed in a network shape in the base elastic body 120 , for example.

[0232] In this embodiment, for example, the base elastomer and the non-ohmic particles are mixed so that E≧E≦ ... th When the volume resistivity ρ of the non-ohmic composition is compared within the range of , the volume resistivity ρ when the non-ohmic composition is uniaxially stretched by 50% is 50 times or less relative to the volume resistivity ρ when the non-ohmic composition is not stretched.

[0233] In addition, at this time, in this embodiment, for example, the base elastomer and the non-ohmic particles are mixed so that the threshold electric field intensity E2 at the starting point P2 of the descent when the non-ohmic composition is subjected to 50% uniaxial stretching is less than 1.4 times the threshold electric field intensity E1 at the starting point P1 of the descent when the non-ohmic composition is not stretched.

[0234] Specifically, as described above, by mixing the elastomer (A) 122, which has relatively high compatibility with the non-ohmic particles 140 and the elastomer (B) 124, which has relatively low compatibility with the non-ohmic particles 140, as the base elastomer 120, the elastomer (A) 122 can constitute a sea phase, while the elastomer (B) 124 can constitute an island phase, while containing a large amount of non-ohmic particles 140. As a result, the non-ohmic particles 140 can be dispersed in a network-like manner in the base elastomer 120.

[0235] It should be noted that, in this case, for example, the elastomer (A) 122, the elastomer (B) 124, and the non-ohmic particles 140 are mixed simultaneously. Even if the three materials are mixed simultaneously, due to the different compatibilities between the elastomer (A) 122 and the elastomer (B) 124, the elastomer (A) 122 contains more non-ohmic particles 140 than the elastomer (B) 124, allowing the non-ohmic particles 140 to be dispersed in a network pattern within the base elastomer 120.

[0236] In this case, for example, the elastomer (A) 122 and the non-ohmic particles 140 are mixed so as to occupy 30% or more of the volume of the entire non-ohmic composition. This allows the non-ohmic particles 140 to be stably dispersed in a network in the base elastomer 120 .

[0237] It should be noted that other additives (cross-linking agent, antioxidant, plasticizer, etc.) can be added as needed.

[0238] As described above, the non-ohmic composition of this embodiment is obtained.

[0239] (S124: Non-ohmic resistance layer forming step)

[0240] After preparing the non-ohmic composition, a mold having a predetermined core is used, the non-ohmic composition is injected into the mold, and heated at a predetermined temperature to cause cross-linking. This forms the non-ohmic resistive layer 220. As a result, the non-ohmic resistive layer 220 is formed into a cylindrical shape, defining the hollow portion 202.

[0241] (S126: Semi-conductive Tapered Portion Forming Step)

[0242] A semiconductive resin composition is injected into a mold having a predetermined conical cavity to form semiconductive tapered portion 240. At this time, semiconductive tapered portion 240 is inclined so as to expand in diameter from one axial end of hollow portion 202 toward the other end, forming inclined surface 242.

[0243] (S128: Insulation Layer Formation Step)

[0244] After forming the non-ohmic resistor layer 220 and the semiconductive tapered portion 240, the non-ohmic resistor layer 220 is placed so as to cover the outer circumference of the core using a mold having a core forming the hollow portion 202. After the non-ohmic resistor layer 220 is placed, the semiconductive tapered portion 240 is placed so that one end of the semiconductive tapered portion 240 is outside the non-ohmic resistor layer 220.

[0245] After the non-ohmic resistance layer 220 and the semiconductive tapered portion 240 are disposed in a mold, an insulating resin composition is injected into the mold to form the insulating layer 260 so as to cover the non-ohmic resistance layer 220 and the semiconductive tapered portion 240 .

[0246] After the forming is completed, the formed body is removed from the mold and unnecessary parts are removed from the formed body.

[0247] As described above, the cable connection unit 10 of the present embodiment is manufactured. Thus, the cable connection unit 10 of the present embodiment is prepared in a state that can be constructed on site.

[0248] (S140: Power Cable Preparation Process)

[0249] During on-site construction, the power cable is gradually peeled off axially from the front end, so that the cable conductor, cable insulation layer and cable outer semi-conductive layer are exposed in sequence from the front end side of the power cable.

[0250] (S160: Embedding Process)

[0251] After the cable connection unit 10 and the power cable are prepared, the power cable is fitted into the hollow portion 202 of the cable connection unit 10. In this embodiment, for example, the following diameter expansion mounting method can be employed.

[0252] First, prepare an expansion tube having an outer diameter larger than that of the power cable. The expansion tube is, for example, divided in an axial cross-section. After preparing the expansion tube, insert the expansion tube into the hollow portion 202 of the cable connection unit 10 to pre-expand the cable connection unit 10. After expanding the cable connection unit 10, insert the power cable into the expansion tube, and configure the cable connection unit 10 at a predetermined installation position. After configuring the cable connection unit 10, remove the expansion tube from the hollow portion 202 of the cable connection unit 10 to reduce the diameter of the cable connection unit 10. In this way, the power cable can be embedded in the hollow portion 202 of the cable connection unit 10.

[0253] (S180: Insertion into porcelain tube process)

[0254] After the power cable is inserted into the hollow portion 202 of the cable connection unit 10, the power cable, with the cable connection unit 10 embedded therein, is inserted into a predetermined porcelain tube. After the power cable is inserted into the porcelain tube, the front end of the cable conductor is secured to the upper portion of the porcelain tube, and the extended side of the power cable is secured to the lower portion of the porcelain tube using a predetermined flange.

[0255] After the power cable is fixed in the porcelain tube, a predetermined insulating medium is filled in the porcelain tube.

[0256] As described above, the cable connection structure of this embodiment is manufactured.

[0257] (4) Effects of this embodiment

[0258] According to this embodiment, one or more of the following effects can be achieved.

[0259] (a) In the non-ohmic composition of this embodiment, the non-ohmic particles 140 are dispersed in a network in the base elastomer 120. In this way, by dispersing the non-ohmic particles 140 in a network, the elasticity of the base elastomer 120 itself can be maintained in the particle-free region outside the network particle group region. As a result, when the non-ohmic composition is stretched, the base elastomer 120 in the particle-free region can be preferentially deformed. On the other hand, in the particle group region, the stress at the interface between the base elastomer 120 and the non-ohmic particles 140 can be relaxed, and the formation of gaps can be suppressed. As a result, the separation of adjacent non-ohmic particles 140 can be suppressed, thereby suppressing the distance between the non-ohmic particles 140 from increasing. By suppressing the distance between the non-ohmic particles 140 from increasing, a low-resistance circuit can be stably formed between the non-ohmic particles during the application of a high electric field to the non-ohmic composition. As a result, even when the non-ohmic composition is stretched, the E-ρ characteristics of the non-ohmic composition itself can be stably maintained.

[0260] (b) Even when the non-ohmic composition is stretched, by stably maintaining the E-ρ characteristic of the non-ohmic composition, when the cable connection unit 10 is externally fitted onto a power cable in an expanded state, and a high electric field is locally applied, the electric field can be uniformly distributed within the non-ohmic resistive layer formed of the non-ohmic composition. As a result, the occurrence of insulation breakdown in the cable connection unit 10 can be suppressed.

[0261] (c) Even when the non-ohmic composition is stretched, the E-ρ characteristics of the non-ohmic composition are stably maintained, making it possible to employ an expanded diameter installation method in which the cable connection unit 10 is pre-expanded before being installed on the power cable. Even with the expanded diameter installation method, the E-ρ characteristics of the non-ohmic composition are not irreversibly altered, and the electric field relaxation effect of the non-ohmic resistance layer can be stably achieved.

[0262] (d) Even when stretching a non-ohmic composition, the stable E-ρ characteristics of the non-ohmic composition eliminate the need to mix non-ohmic particles at excessively high concentrations. This ensures sufficient entanglement between molecules in the base elastomer. Consequently, a decrease in the tensile properties and residual elongation characteristics of the non-ohmic composition can be suppressed.

[0263] (e) In the non-ohmic composition of this embodiment, the coefficient of variation of the distance between the centers of gravity of the non-ohmic particles 140 is 0.5 or greater. By setting the coefficient of variation to 0.5 or greater, a network-dispersed state of the non-ohmic particles 140 can be stably achieved within the base elastomer 120. This facilitates stress relief at the interface between the base elastomer 120 and the non-ohmic particles 140, thereby stably suppressing the formation of gaps. Consequently, regardless of the tensile state of the non-ohmic composition, variations in the E-ρ characteristic of the non-ohmic composition can be stably suppressed.

[0264] (f) In the non-ohmic composition of this embodiment, the base elastomer 120 includes an elastomer (A) 122 having relatively high compatibility with the non-ohmic particles 140, and an elastomer (B) 124 having relatively low compatibility with the non-ohmic particles 140. Consequently, the elastomer (A) 122 contains more non-ohmic particles 140 than the elastomer (B) 124, and the sea phase can be formed by the elastomer (A) 122.

[0265] On the other hand, the island phase can be formed by the elastomer (B) 124. As a result, a state in which the non-ohmic particles 140 are dispersed in a network in the base elastomer 120 can be stably formed.

[0266] (5) Modifications of this embodiment

[0267] The first embodiment described above may be modified as follows: Hereinafter, only elements different from the above embodiment will be described, and elements substantially identical to those already described in the above embodiment will be denoted by the same reference numerals and their description will be omitted.

[0268] In Modifications 1 and 2, the configuration of the base elastic body is different from that of the first embodiment.

[0269] (5-1) Modification 1

[0270] In the non-ohmic composition before crosslinking of Modification 1, for example, elastomer (A) 122 is non-crosslinked, while elastomer (B) 124 comprises (is composed of) pre-crosslinked rubber. Non-ohmic particles 140 are difficult to disperse in crosslinked rubber. Therefore, non-ohmic particles 140 can be preferentially dispersed in elastomer (A) 122.

[0271] It should be noted that at least a portion of the elastomer (A) may be cross-linked. However, even in this case, the cross-linking density of the elastomer (B) 124 is preferably higher than the cross-linking density of the elastomer (A) 122 , for example.

[0272] In Modification 1, the elastic body (A) 122 and the elastic body (B) 124 may be made of different materials, or the elastic body (A) 122 and the elastic body (B) 124 may be made of the same material except for the cross-linked state.

[0273] Specifically, the elastomer (A) 122 is, for example, silicone rubber (Q), ethylene propylene rubber (EPR), ethylene propylene diene rubber (EPDM), styrene butadiene rubber (SBR), epichlorohydrin rubber (CO), chloroprene rubber (CR), chlorosulfonated polyethylene rubber (CSM), nitrile rubber (NBR), acrylic rubber (ACM), ethylene acrylic rubber (AEM), ethylene-vinyl acetate copolymer (EVM), and urethane rubber (U). The elastomer (B) 124 is, for example, particles made by freezing and crushing cross-linked products of ethylene propylene rubber (EPR), ethylene propylene diene rubber (EPDM), styrene butadiene rubber (SBR), epichlorohydrin rubber (CO), chloroprene rubber (CR), chlorosulfonated polyethylene rubber (CSM), nitrile rubber (NBR), acrylic rubber (ACM), ethylene acrylic rubber (AEM), ethylene-vinyl acetate copolymer (EVM), urethane rubber (U), etc., or a powdered pre-cross-linked elastomer such as silicone rubber powder (KMP-597, KMP-598, KMP-594, X-52875 manufactured by Shin-Etsu Chemical).

[0274] In the non-ohmic resistance layer 220 of the cable connection unit 10 of Modification 1, the elastomer (A) 122 and the elastomer (B) 124 are chemically bonded to each other, for example, by crosslinking. In the non-ohmic resistance layer 220, the elastomer (A) 122 and the elastomer (B) 124 may be uniformly crosslinked, or the crosslink density of the elastomer (B) 124 may be higher than the crosslink density of the elastomer (A) 122.

[0275] In the non-ohmic composition preparation step S122 of Modification 1, similarly to the first embodiment, for example, elastomer (A) 122, elastomer (B) 124, and non-ohmic particles 140 are simultaneously mixed. During mixing, elastomer (B) 124 can remain in a cross-linked state. This can suppress the dispersion of non-ohmic particles 140 into elastomer (B) 124.

[0276] (Effect)

[0277] According to Modification 1, by including pre-crosslinked rubber in the elastomer (B) 124, dispersion of the non-ohmic particles 140 into the elastomer (B) 124 can be suppressed during mixing. Consequently, the non-ohmic particles 140 can be preferentially dispersed in the elastomer (A) 122, and the sea phase can be formed by the elastomer (A) 122 containing a large amount of non-ohmic particles 140. As a result, a network-like dispersion of the non-ohmic particles 140 in the base elastomer 120 can be stably achieved.

[0278] (5-2) Modification 2

[0279] In the non-ohmic composition before cross-linking of Modification 2, for example, the elastomer (A) 122 includes (is composed of) rubber, and the elastomer (B) 124 includes (is composed of) a thermoplastic elastomer.

[0280] In Modification 2, the melting point of the elastomer (B) 124 is, for example, higher than the softening point of the elastomer (A) 122. Furthermore, the melting point of the elastomer (B) 124 is preferably higher than the temperature at which the non-ohmic composition is mixed.

[0281] Specifically, the elastomer (A) 122 includes, for example, silicone rubber (Q), ethylene propylene rubber (EPR), ethylene propylene diene rubber (EPDM), styrene butadiene rubber (SBR), epichlorohydrin rubber (CO), chloroprene rubber (CR), chlorosulfonated polyethylene rubber (CSM), nitrile butadiene rubber (NBR), acrylic ester rubber (ACM), ethylene acrylic ester rubber (AEM), and ethylene vinyl acetate copolymer (EVM). The elastomer (B) 124 includes, for example, a particulate olefin-based thermoplastic elastomer, a polyamide-based thermoplastic elastomer, or a polyurethane-based thermoplastic elastomer.

[0282] In the non-ohmic resistance layer 220 of the cable connection unit 10 according to the second modification, the elastomer (A) 122 and the elastomer (B) 124 are chemically bonded to each other by, for example, cross-linking.

[0283] In the non-ohmic composition preparation step S122 of Modification 2, similarly to the first embodiment, for example, elastomer (A) 122, elastomer (B) 124, and non-ohmic particles 140 are mixed simultaneously. During mixing, elastomer (B) 124 remains unmelted. This prevents the non-ohmic particles 140 from dispersing into the elastomer (B) 124.

[0284] (Effect)

[0285] According to Modification 2, by making the melting point of elastomer (B) 124 higher than the softening point of elastomer (A) 122, elastomer (B) 124 remains unmelted during mixing, thereby suppressing the dispersion of non-ohmic particles 140 into elastomer (B) 124. Consequently, non-ohmic particles 140 are preferentially dispersed in elastomer (A), and a sea phase is formed by elastomer (A) 122 containing a large amount of non-ohmic particles 140. As a result, a state in which non-ohmic particles 140 are dispersed in a network-like manner in the base elastomer 120 can be stably achieved.

[0286] <Second embodiment of the present invention>

[0287] Next, use Figure 5 A second embodiment of the present invention will be described. Figure 5 It is a cross-sectional view showing the cable connection unit according to the present embodiment.

[0288] In this embodiment, the cable connection method in the cable connection unit is different from that in the first embodiment. Hereinafter, similarly to the modification of the first embodiment, only the elements different from the first embodiment will be described.

[0289] (1) Cable connection unit

[0290] The cable connection unit (cable intermediate connection unit) 12 of this embodiment is configured, for example, as a cable intermediate connection structure, to linearly connect a pair of power cables so that their axes are aligned and butted against each other. Here, one of the pair of power cables is referred to as the "first power cable" and the other as the "second power cable."

[0291] It should be noted that in this embodiment, the end portion of the cable connection unit 12, which is one axial end of the cable connection unit 12 and on the side where the first power cable in the cable connection unit 12 extends, is referred to as the "first end of the cable connection unit 12." On the other hand, the end portion of the cable connection unit 12, which is the other axial end of the cable connection unit 12 and on the side where the second power cable in the cable connection unit 12 extends, is referred to as the "second end of the cable connection unit."

[0292] like Figure 5 As shown, the cable connection unit 12 includes, for example, an inner semiconductive layer 210 , a non-ohmic resistance layer 220 , a semiconductive tapered portion 240 , an insulating layer 260 , and an outer semiconductive layer 280 .

[0293] Internal semiconductive layer 210 is, for example, semiconductive. Specifically, internal semiconductive layer 210 comprises, for example, the same semiconductive rubber as semiconductive tapered portion 240. Internal semiconductive layer 210 is, for example, cylindrical in shape, forming the axial center of hollow portion 202. It should be noted that when a pair of power cables are embedded within hollow portion 202, internal semiconductive layer 210 is positioned to cover a compression sleeve used to compress and connect the cable conductors. Consequently, internal semiconductive layer 210 reaches a potential substantially the same as that of the cable conductors, i.e., a higher potential.

[0294] The non-ohmic resistive layer 220 is, for example, provided in a cylindrical shape to constitute the remaining portion of the hollow portion 202 in the axial direction, excluding the inner semiconductive layer 210. Furthermore, the non-ohmic resistive layer 220 is provided so as to cover the inner semiconductive layer 210. When a pair of power cables are embedded in the hollow portion 202, the non-ohmic resistive layer 220 extends so as to cover the outer semiconductive layer of the first power cable and the outer semiconductive layer of the second power cable.

[0295] When a pair of power cables are embedded within hollow portion 202, both ends of non-ohmic resistive layer 220 contact the outer semiconductive layer of the first power cable and the outer semiconductive layer of the second power cable, respectively, thereby grounding them. Similarly to inner semiconductive layer 210, the portion of non-ohmic resistive layer 220 in contact with inner semiconductive layer 210 reaches a high potential. Within non-ohmic resistive layer 220, its non-ohmic nature reduces the resistance at locations where the electric field is concentrated, evenly distributing equipotential lines from inner semiconductive layer 210 toward both ends.

[0296] For example, a pair of semiconductive tapered portions 240 are provided on both sides of the cable connection unit 12 in the axial direction, sandwiching the inner semiconductive layer 210. Of the pair of semiconductive tapered portions 240, the portion on the first power cable side is designated as a "first semiconductive tapered portion 240a," and the portion on the second power cable side is designated as a "second semiconductive tapered portion 240b."

[0297] The first semi-conductive tapered portion 240a and the second semi-conductive tapered portion 240b are both formed in a conical shape, and their expanded diameter sides face each other.

[0298] The first end of the first semi-conductive tapered portion 240a in the axial direction of the cable connection unit 10 may be in contact with or separated from the non-ohmic resistor layer 220. The first semi-conductive tapered portion 240a may include, for example, an inclined surface 242 that is inclined so as to gradually move away from the non-ohmic resistor layer 220 from a portion close to the non-ohmic resistor layer 220 toward a second end in the axial direction of the cable connection unit 10.

[0299] On the other hand, the second semiconductive tapered portion 240 b is configured symmetrically with the first semiconductive tapered portion 240 a with the inner semiconductive layer 210 interposed therebetween, for example.

[0300] The insulating layer 260 is provided so as to cover the non-ohmic resistive layer 220 and the pair of semiconductive tapered portions 240. For example, the insulating layer 260 is provided so as to be embedded between the non-ohmic resistive layer 220 and the inclined surface 242 of the first semiconductive tapered portion 240a, and between the non-ohmic resistive layer 220 and the inclined surface 242 of the second semiconductive tapered portion 240b.

[0301] The outer semiconductive layer 280 is provided so as to cover the insulating layer 260. The outer semiconductive layer 280 is in contact with the first semiconductive tapered portion 240a and the second semiconductive tapered portion 240b. Therefore, the outer semiconductive layer 280 is grounded together with the first semiconductive tapered portion 240a and the second semiconductive tapered portion 240b.

[0302] The inner semiconductive layer 210 , the non-ohmic resistance layer 220 , the pair of semiconductive tapered portions 240 , the insulating layer 260 , and the outer semiconductive layer 280 may be integrally bonded by, for example, molding.

[0303] (2) Effect

[0304] According to the present embodiment, even with the cable connection unit 12 used in the cable intermediate connection structure, the same effects as those of the first embodiment can be obtained.

[0305] <Other embodiments of the present invention>

[0306] The embodiments of the present invention have been specifically described above, but the present invention is not limited to the above embodiments and various modifications can be made without departing from the spirit and scope of the present invention. It should be noted that the "above embodiments" referred to here refer to the first and second embodiments.

[0307] While the above embodiment describes the cable connection unit 10 as having a semi-conductive tapered portion 240, the present invention is not limited to this configuration. For example, instead of providing the semi-conductive tapered portion 240, the insulating layer 260 may have a diameter that gradually decreases from the axial center toward the ends. This can alleviate electric field concentration at the axial ends of the insulating layer 260.

[0308] In the second embodiment, the drawings show that the semiconductive tapered portion 240 and the outer semiconductive layer 280 are separate. However, the semiconductive tapered portion 240 may be formed as a part of the outer semiconductive layer 280 and integrated with the outer semiconductive layer 280 .

[0309] In the above embodiment, the elastomer (A) 122, the elastomer (B) 124, and the non-ohmic particles 140 are mixed simultaneously in the non-ohmic composition preparation step S122. However, the present invention is not limited to this configuration. For example, the elastomer (A) 122 and the non-ohmic particles 140 may be pre-mixed to form a masterbatch, and then the masterbatch may be mixed with the elastomer (B) 124.

[0310] While the above embodiment describes the case where the expansion installation method using an expansion tube is employed in the insertion step S160, the present invention is not limited to this method. For example, the cable connection unit 10 may be expanded using an inner core formed by spirally winding an inner core bobbin. It should be noted that in this case, when the cable connection unit 10 is reduced in diameter, the inner core bobbin may be gradually unwound starting from one axial end of the cable connection unit 10.

[0311] In the above embodiment, the non-ohmic resistor layer 220, the semiconductive tapered portion 240, and the insulating layer 260 are cross-linked as a whole. However, the present invention is not limited to this. For example, the semiconductive tapered portion 240 and the insulating layer 260 may be cross-linked as a whole, while the non-ohmic resistor layer 220 may be formed using a separate mold.

[0312] In the above embodiment, an example of the manufacturing method is described, but the order of each process in the manufacturing method can be replaced as much as possible.

[0313] It has been described that the configuration of Modification 1 or 2 can be applied to the above-mentioned first embodiment, but the configuration of Modification 1 or 2 of the first embodiment can also be applied to the second embodiment.

[0314] Example

[0315] Next, embodiments of the present invention will be described. These embodiments are examples of the present invention, and the present invention is not limited to these embodiments.

[0316] (1) Preparation of non-ohmic compositions

[0317] The non-ohmic composition of the embodiment was prepared as described below. Specifically, first, a base elastomer and non-ohmic particles as shown below were prepared. Then, the base elastomer, non-ohmic particles and other additives were mixed to produce a non-ohmic composition. At this time, the elastomer (A) and the non-ohmic particles were mixed in a manner that accounted for more than 30% of the volume of the entire non-ohmic composition. Then, the obtained non-ohmic composition was press-formed at a temperature of 160°C for 1 hour to produce a sample sheet simulating a non-ohmic resistance layer for a cable connection unit.

[0318] [Example]

[0319] Basic elastomer:

[0320] Base elastomer (A): Ethylene acrylate rubber

[0321] Base elastomer (B): Ethylene propylene diene rubber

[0322] Non-ohmic particles: Particles containing zinc oxide and trace amounts of other metal oxides such as bismuth and antimony (maximum particle size: 7 μm, volume average particle size: 3 μm) (volume ratio to base elastomer: 0.3)

[0323] Other additives (the amount in parentheses is relative to 100 parts by mass of the base elastomer):

[0324] Cross-linking agent: DCP (1.5 parts by mass)

[0325] Cross-linking aid: Zinc Hua No. 3 (5 parts by mass)

[0326] Plasticizer: polybutadiene oil (10 parts by mass)

[0327] Antioxidant: Amine TMDQ (1.5 parts by mass)

[0328] On the other hand, in the comparative example, a non-ohmic composition was prepared in the same manner as in the example except that the base elastomer was made only of ethylene propylene diene rubber, and a sample sheet was produced.

[0329] (2) Evaluation

[0330] (Cross-section observation)

[0331] The cross sections of the non-ohmic compositions of Examples and Comparative Examples were observed using a scanning electron microscope (SEM).

[0332] (Distance between centers of gravity of non-ohmic particles)

[0333] The distance between the centers of gravity of the non-ohmic particles in the sample sheets of the Examples and Comparative Examples was measured in the following manner. Specifically, the distance between the centers of gravity was measured using image analysis. More specifically, the distance between the centers of gravity of a plurality of adjacent non-ohmic particles was measured in a cross-sectional SEM observation image at a magnification of 2000. It should be noted that, as described above, adjacent particles here refer to particles that do not include other particles when the centers of gravity of the two particles are connected by a straight line.

[0334] (Volume resistivity)

[0335] The volume resistivity of the sample pieces of Examples and Comparative Examples was measured as follows: Specifically, the sample pieces were held between circular parallel plate electrodes with a diameter of 25 mm and a guard electrode, and immersed in silicone oil at a temperature of 30°C.

[0336] Next, a predetermined voltage is gradually applied between the electrodes holding the sample piece, and the current flowing between the electrodes is measured using a microammeter. The obtained current value is substituted into the following formula (2) to calculate the volume resistivity ρ relative to the predetermined voltage (electric field).

[0337] ρ=S·V / t·I···(2)

[0338] Here, ρ is the volume resistivity, S is the electrode area, t is the thickness of the sample piece, V is the applied voltage, and I is the measured current.

[0339] The volume resistivity ρ was measured by the above-mentioned measurement method when the sample piece was not stretched, stretched 30% along a predetermined uniaxial direction of the main surface using a predetermined stretching jig, and stretched 50% using the same method.

[0340] (Tensile properties)

[0341] A JIS-3 dumbbell plate having a thickness of 2 mm was stretched at a rate of 200 mm / mm using a tensile testing machine at room temperature, and the elongation and stress at break were evaluated.

[0342] (Residual elongation characteristics)

[0343] A strip test piece with a thickness of 2 mm, a width of 5 mm, and a length of 120 mm was stretched at an elongation of 130% for 24 hours at room temperature using a predetermined stretching jig. The test piece was then removed from the stretching jig at room temperature and the residual elongation after 24 hours was evaluated.

[0344] (3) Results

[0345] (Cross-section observation)

[0346] use Figure 6A and Figure 6B The results of cross-sectional observation of Examples and Comparative Examples are described below. Figure 6A The diagram shows an observation image obtained by observing the non-ohmic composition according to the example using a scanning electron microscope. Figure 6B This figure shows an observation image obtained by observing the non-ohmic composition according to the comparative example using a scanning electron microscope.

[0347] like Figure 6BAs shown, in the comparative example, the non-ohmic particles are uniformly dispersed in the base elastomer. In addition, in the comparative example, the particle-free region is small, with a diameter of less than 4.5 μm in the cross-sectional view.

[0348] In contrast, Figure 6A As shown, in the examples, it was confirmed that the non-ohmic particles were dispersed in a network in the base elastomer. In addition, in the examples, it was confirmed that there were many particle-free regions with a diameter of 4.5 μm or more (dotted lines in the figure) in the cross-sectional view.

[0349] (Distance between centers of gravity of non-ohmic particles)

[0350] use Figure 7 The measurement results of the distance between the centers of gravity of the non-ohmic particles in Examples and Comparative Examples are described below. Figure 7 This is a graph showing the frequency of non-ohmic particles versus the distance between centers of gravity in the non-ohmic compositions of Examples and Comparative Examples.

[0351] like Figure 7 As shown in the comparative example, as described above, the range of the distance between centers of gravity is narrow because the non-ohmic particles are uniformly dispersed in the base elastomer. Specifically, the average value of the distance between centers of gravity of the non-ohmic particles is 2.59 μm, and the standard deviation of the distance between centers of gravity is 1.06 μm. As a result, the coefficient of variation calculated from the above formula (1) is 0.41.

[0352] In contrast, in the examples, as described above, the non-ohmic particles are dispersed in a network pattern within the base elastomer, resulting in a wide distribution of the distances between centers of gravity. Specifically, the average value of the distances between centers of gravity of the non-ohmic particles is 2.41 μm, and the standard deviation of the distances between centers of gravity is 1.43 μm. As a result, it was confirmed that the coefficient of variation calculated from the above formula (1) is 0.59.

[0353] (Volume resistivity)

[0354] use Figure 8 and Figure 9 The measurement results of the volume resistivity of the non-ohmic compositions in Examples and Comparative Examples are described below. Figure 8 This is a graph showing the volume resistivity versus electric field intensity in the non-ohmic compositions of Examples. Figure 9 This is a graph showing the volume resistivity versus electric field intensity in non-ohmic compositions of comparative examples.

[0355] like Figure 9As shown, in the comparative examples, the volume resistivity ρ gradually increases as the non-ohmic composition is stretched to a greater extent. Specifically, in the comparative examples, when the volume resistivity ρ of the non-ohmic composition is compared within the range of E ≥ E1 when the non-ohmic composition is not stretched, the volume resistivity ρ when the non-ohmic composition is uniaxially stretched by 50% is more than 50 times the volume resistivity ρ when the non-ohmic composition is not stretched.

[0356] In the comparative example, as the non-ohmic composition is stretched gradually, the starting point of the decrease in volume resistivity ρ shifts to the high electric field strength side. Specifically, in the comparative example, the threshold electric field strength E at the starting point of the decrease when the non-ohmic composition is stretched 50% uniaxially is th The threshold electric field strength E at the start of the decrease relative to the case where the non-ohmic composition is not stretched th More than 1.4 times.

[0357] In the comparative example results, because the non-ohmic particles are uniformly dispersed in the base elastomer, stretching the non-ohmic composition increases stress at the interface between the non-ohmic particles and the base elastomer, creating gaps. Adjacent non-ohmic particles separate, and the distance between them increases. Consequently, it is believed that stretching the non-ohmic composition causes a deviation in the E-ρ characteristic.

[0358] In contrast, Figure 8 As shown, in the Examples, even when the non-ohmic composition is gradually stretched to a large extent, the change in volume resistivity ρ is small. Specifically, in the Examples, it was confirmed that when the volume resistivity ρ of the non-ohmic composition is compared within the range of E ≥ E1 when the non-ohmic composition is not stretched, the volume resistivity ρ when the non-ohmic composition is uniaxially stretched by 50% is 20 times or less relative to the volume resistivity ρ when the non-ohmic composition is not stretched.

[0359] In addition, in the examples, even when the non-ohmic composition is stretched gradually and greatly, the starting point of the decrease in volume resistivity ρ is roughly the same. Specifically, in the comparative examples, it can be confirmed that the threshold electric field intensity E at the starting point of the decrease when the non-ohmic composition is stretched 50% uniaxially is th The threshold electric field strength E at the start of the decrease relative to the case where the non-ohmic composition is not stretched th Less than 1.2 times.

[0360] It should be noted that, in the examples, even if the non-ohmic composition is gradually stretched to a large extent, E>E th The change in the slope of the straight line portion in is also small. Specifically, when the non-ohmic composition is subjected to 50% uniaxial stretching, E>E thThe slope of the straight line portion in the equation is E>E in the case where the non-ohmic composition is not stretched. th The slope of the straight line portion in the graph is reduced by 25% and is within ±50%.

[0361] (Tensile properties)

[0362] The measurement results are as follows: In the Example, the elongation at break was 280%, and the breaking strength was 5.9 MPa. On the other hand, in the Comparative Example, the elongation at break was 280%, and the breaking strength was 6.0 MPa. In other words, the tensile properties of the Example and the Comparative Example are approximately equivalent.

[0363] (Residual elongation characteristics)

[0364] The measurement results are as follows: the residual elongation of the example is 9.2%. On the other hand, the residual elongation of the comparative example is 8.7%. In other words, the residual elongation characteristics of the example and the comparative example are approximately equal.

[0365] (Summarize)

[0366] According to the results of the above examples, by dispersing the non-ohmic particles in a network in the base elastomer, when the non-ohmic composition is stretched, the base elastomer in the particle-free region can be preferentially deformed. On the other hand, in the particle group region, the stress at the interface between the base elastomer and the non-ohmic particles can be relaxed, and the formation of gaps can be suppressed. Thus, the distance between the non-ohmic particles can be suppressed from becoming longer. The results confirm that even when the non-ohmic composition is stretched, the E-ρ characteristics inherent in the non-ohmic composition can be stably maintained.

[0367] Furthermore, the results of the examples show that since the non-ohmic particles do not need to be mixed at excessively high concentrations, sufficient entanglement between molecules in the base elastomer can be ensured. The results confirm that the tensile properties and residual elongation properties of the non-ohmic composition can be suppressed from deteriorating.

[0368] <Preferred Embodiments of the Invention>

[0369] Hereinafter, preferred embodiments of the present invention will be described.

[0370] (Note 1)

[0371] A non-ohmic composition comprises a base elastomer and a plurality of non-ohmic particles.

[0372] The electric field strength applied to the non-ohmic composition is defined as E, the volume resistivity of the non-ohmic composition is defined as ρ, and the threshold electric field strength at which the absolute value of the slope change of logρ relative to logE becomes the maximum is defined as E. th, E≥E without stretching the non-ohmic composition th When comparing the volume resistivity ρ of the non-ohmic composition within the range of

[0373] The volume resistivity p when the non-ohmic composition is uniaxially stretched by 50% is 50 times or less the volume resistivity p when the non-ohmic composition is not stretched.

[0374] (Note 2)

[0375] The non-ohmic composition according to Supplementary Note 1,

[0376] The threshold electric field strength E when the non-ohmic composition is subjected to 50% uniaxial stretching th Relative to E without stretching the non-ohmic composition th Less than 1.4 times.

[0377] (Note 3)

[0378] A non-ohmic composition comprises a base elastomer and a plurality of non-ohmic particles.

[0379] When the electric field intensity applied to the non-ohmic composition is set to E and the volume resistivity of the non-ohmic composition is set to ρ,

[0380] The threshold electric field intensity E at which the absolute value of the change in the slope of logρ with respect to logE becomes maximum when the non-ohmic composition is subjected to 50% uniaxial stretching is th Relative to E without stretching the non-ohmic composition th Less than 1.4 times.

[0381] (Note 4)

[0382] The non-ohmic composition according to any one of Supplementary Notes 1 to 3,

[0383] When the non-ohmic composition is subjected to 50% uniaxial stretching, E>E th The slope of the straight line portion in the equation E>E is relative to the slope of the straight line portion in the equation E>E when the non-ohmic composition is not stretched. th The slope of the straight line portion in is within ±50%.

[0384] (Note 5)

[0385] The non-ohmic composition according to any one of Supplementary Notes 1 to 4,

[0386] The plurality of non-ohmic particles are dispersed in the base elastomer in a network-like manner.

[0387] (Note 6)

[0388] A non-ohmic composition comprises a base elastomer and a plurality of non-ohmic particles.

[0389] The plurality of non-ohmic particles are dispersed in the base elastomer in a network-like manner.

[0390] (Note 7)

[0391] The non-ohmic composition according to any one of Supplementary Notes 1 to 6,

[0392] The coefficient of variation of the distance between the centers of gravity of the plurality of non-ohmic particles obtained by the following formula (1) is 0.5 or more

[0393] Coefficient of variation = standard deviation / mean value... (1).

[0394] (Note 8)

[0395] The non-ohmic composition according to any one of Supplementary Notes 1 to 7,

[0396] When observing a cross section of the non-ohmic composition, there are a plurality of particle-free regions containing no non-ohmic particles and having a diameter equal to or greater than 1.5 times the volume average particle diameter of the non-ohmic particles.

[0397] (Note 9)

[0398] The non-ohmic composition according to any one of Supplementary Notes 1 to 8,

[0399] The base elastomer has:

[0400] an elastomer (A) having relatively high compatibility with the non-ohmic particles, and

[0401] The elastomer (B) has relatively low compatibility with the non-ohmic particles.

[0402] The elastomer (A) contains more non-ohmic particles than the elastomer (B) and constitutes a sea phase.

[0403] The elastomer (B) constitutes an island phase.

[0404] (Note 10)

[0405] The non-ohmic composition according to Supplementary Note 9,

[0406] The difference between the solubility parameter of the elastomer (A) and the solubility parameter of the elastomer (B) is 0.5 (cal / cm 3 ) 1 / 2 above.

[0407] (Note 11)

[0408] The non-ohmic composition according to Supplementary Note 9,

[0409] The elastomer (A) is non-crosslinked,

[0410] The elastomer (B) comprises a cross-linked rubber.

[0411] (Note 12)

[0412] The non-ohmic composition according to Supplementary Note 9,

[0413] The crosslinking density of the elastomer (B) is higher than the crosslinking density of the elastomer (A).

[0414] (Note 13)

[0415] The non-ohmic composition according to Supplementary Note 9,

[0416] The elastomer (A) comprises rubber,

[0417] The elastomer (B) comprises a thermoplastic elastomer,

[0418] The melting point of the elastomer (B) is higher than the softening point of the elastomer (A).

[0419] (Note 14)

[0420] The non-ohmic composition according to any one of Supplementary Notes 9 to 13,

[0421] The elastomer (A) and the non-ohmic particles account for 30% or more of the volume of the entire non-ohmic composition.

[0422] (Note 15)

[0423] The non-ohmic composition according to any one of Supplementary Notes 9 to 14,

[0424] The elastomer (A) and the elastomer (B) are chemically bonded to each other.

[0425] (Note 16)

[0426] The non-ohmic composition according to any one of Supplementary Notes 9 to 15,

[0427] Both the elastomer (A) and the elastomer (B) have insulating properties.

[0428] (Note 17)

[0429] The non-ohmic composition according to any one of Supplementary Notes 9 to 16,

[0430] The elastic modulus of the elastomer (B) is lower than the elastic modulus of the elastomer (A).

[0431] (Note 18)

[0432] A cable connection unit is a cylindrical cable connection unit in which a power cable is embedded, comprising:

[0433] A cylindrical non-ohmic resistance layer made of a non-ohmic composition, and

[0434] an insulating layer provided so as to cover the outer side of the non-ohmic resistance layer,

[0435] The non-ohmic composition comprises a base elastomer and a plurality of non-ohmic particles.

[0436] The electric field strength applied to the non-ohmic composition is defined as E, the volume resistivity of the non-ohmic composition is defined as ρ, and the threshold electric field strength at which the absolute value of the slope change of logρ relative to logE becomes the maximum is defined as E. th , E≥E without stretching the non-ohmic composition th When comparing the volume resistivity ρ of the non-ohmic composition within the range of

[0437] The volume resistivity p when the non-ohmic composition is uniaxially stretched by 50% is 50 times or less the volume resistivity p when the non-ohmic composition is not stretched.

[0438] (Note 19)

[0439] A cable connection unit is a cylindrical cable connection unit in which a power cable is embedded, comprising:

[0440] A cylindrical non-ohmic resistance layer made of a non-ohmic composition, and

[0441] an insulating layer provided so as to cover the outer side of the non-ohmic resistance layer,

[0442] The non-ohmic composition comprises a base elastomer and a plurality of non-ohmic particles.

[0443] When the electric field intensity applied to the non-ohmic composition is set to E and the volume resistivity of the non-ohmic composition is set to ρ,

[0444] The threshold electric field intensity E at which the absolute value of the change in the slope of logρ with respect to logE becomes maximum when the non-ohmic composition is subjected to 50% uniaxial stretching is th Relative to E without stretching the non-ohmic composition th Less than 1.4 times.

[0445] (Note 20)

[0446] A cable connection unit is a cylindrical cable connection unit in which a power cable is embedded, comprising:

[0447] A cylindrical non-ohmic resistance layer made of a non-ohmic composition, and

[0448] an insulating layer provided so as to cover the outer side of the non-ohmic resistance layer,

[0449] The non-ohmic composition comprises a base elastomer and a plurality of non-ohmic particles.

[0450] The plurality of non-ohmic particles are dispersed in the base elastomer in a network-like manner.

[0451] (Note 21)

[0452] A method for manufacturing a cable connection unit, which is a cylindrical cable connection unit into which a power cable is embedded, comprising:

[0453] a step of preparing a non-ohmic composition comprising a base elastomer and a plurality of non-ohmic particles;

[0454] A step of forming a cylindrical non-ohmic resistance layer using the non-ohmic composition; and

[0455] forming an insulating layer so as to cover the outer side of the non-ohmic resistance layer;

[0456] In the process of preparing the non-ohmic composition,

[0457] The base elastomer and the plurality of non-ohmic particles are mixed so that: the electric field strength applied to the non-ohmic composition is set to E, the volume resistivity of the non-ohmic composition is set to ρ, and the threshold electric field strength at which the absolute value of the slope change of logρ relative to logE becomes the maximum is set to E. th , E≥E without stretching the non-ohmic composition th When the volume resistivity ρ of the non-ohmic composition is compared within a range of , the volume resistivity ρ when the non-ohmic composition is uniaxially stretched by 50% is 50 times or less relative to the volume resistivity ρ when the non-ohmic composition is not stretched.

[0458] (Note 22)

[0459] A method for manufacturing a cable connection unit, which is a cylindrical cable connection unit into which a power cable is embedded, comprising:

[0460] a step of preparing a non-ohmic composition comprising a base elastomer and a plurality of non-ohmic particles;

[0461] A step of forming a cylindrical non-ohmic resistance layer using the non-ohmic composition; and

[0462] forming an insulating layer so as to cover the outer side of the non-ohmic resistance layer;

[0463] In the process of preparing the non-ohmic composition,

[0464] The plurality of non-ohmic particles are dispersed in the base elastomer in a network shape.

[0465] Explanation of symbols

[0466] 10, 12 Cable connection unit

[0467] 120 Basic Elastomer

[0468] 122 Elastomer (A)

[0469] 124 Elastomer (B)

[0470] 140 Non-ohmic particles

[0471] 202 Hollow

[0472] 210 inner semi-conductive layer

[0473] 220 Non-ohmic resistance layer

[0474] 240 semi-conductive tapered portion

[0475] 240a First semi-conductive tapered portion

[0476] 240b Second semi-conductive tapered portion

[0477] 242 Inclined Surface

[0478] 260 insulation layer

[0479] 280 Outer semi-conductive layer

Claims

1. A non-ohmic composition comprising a base elastomer and a plurality of non-ohmic particles, The base elastomer has: an elastomer (A) having relatively high compatibility with the non-ohmic particles, and The elastomer (B) has relatively low compatibility with the non-ohmic particles. The elastomer (A) contains more non-ohmic particles than the elastomer (B) and constitutes a sea phase. The elastomer (B) constitutes an island phase, When the electric field intensity applied to the non-ohmic composition is set to E and the volume resistivity of the non-ohmic composition is set to ρ, The threshold electric field intensity E at which the absolute value of the change in the slope of logρ with respect to logE becomes maximum when the non-ohmic composition is subjected to 50% uniaxial stretching is th Relative to E without stretching the non-ohmic composition th Less than 1.4 times.

2. The non-ohmic composition according to claim 1, wherein When the non-ohmic composition is subjected to 50% uniaxial stretching, E>E th The slope of the straight line portion in the equation E>E is relative to the slope of the straight line portion in the equation E>E when the non-ohmic composition is not stretched. th The slope of the straight line portion in is within ±50%.

3. The non-ohmic composition according to claim 1 or claim 2, wherein The plurality of non-ohmic particles are dispersed in the base elastomer in a network-like manner.

4. The non-ohmic composition according to claim 1 or claim 2, wherein The coefficient of variation of the distance between the centers of gravity of the plurality of non-ohmic particles obtained by the following formula (1) is 0.5 or greater, Coefficient of variation = standard deviation / mean value... (1).

5. The non-ohmic composition according to claim 1 or claim 2, wherein When observing a cross section of the non-ohmic composition, there are a plurality of particle-free regions containing no non-ohmic particles and having a diameter that is 1.5 times or more the volume average particle diameter of the non-ohmic particles.

6. The non-ohmic composition according to claim 1, wherein The difference between the solubility parameter of the elastomer (A) and the solubility parameter of the elastomer (B) is 0.5 (cal / cm 3 ) 1 / 2 above.

7. The non-ohmic composition according to claim 1, wherein The elastomer (A) is non-crosslinked, The elastomer (B) comprises a cross-linked rubber.

8. The non-ohmic composition according to claim 1, wherein The elastomer (A) comprises rubber, The elastomer (B) comprises a thermoplastic elastomer, The melting point of the elastomer (B) is higher than the softening point of the elastomer (A).

9. The non-ohmic composition according to claim 1, wherein The elastomer (A) and the non-ohmic particles account for 30% or more of the volume of the entire non-ohmic composition.

10. The non-ohmic composition according to claim 1, wherein The elastomer (A) and the elastomer (B) are chemically bonded to each other.

11. A cable connection unit, which is a cylindrical cable connection unit in which a power cable is embedded, comprising: a cylindrical non-ohmic resistance layer composed of a non-ohmic composition, and an insulating layer provided so as to cover the outside of the non-ohmic resistance layer; The non-ohmic composition comprises a base elastomer and a plurality of non-ohmic particles. The base elastomer has: an elastomer (A) having relatively high compatibility with the non-ohmic particles, and The elastomer (B) has relatively low compatibility with the non-ohmic particles. The elastomer (A) contains more non-ohmic particles than the elastomer (B) and constitutes a sea phase. The elastomer (B) constitutes an island phase, When the electric field intensity applied to the non-ohmic composition is set to E and the volume resistivity of the non-ohmic composition is set to ρ, The threshold electric field intensity E at which the absolute value of the change in the slope of logρ with respect to logE becomes maximum when the non-ohmic composition is subjected to 50% uniaxial stretching is th Relative to E without stretching the non-ohmic composition th Less than 1.4 times.

12. The cable connection unit according to claim 11, wherein: The plurality of non-ohmic particles are dispersed in the base elastomer in a network-like manner.

13. A method for manufacturing a cable connection unit, the method comprising: a step of preparing a non-ohmic composition comprising a base elastomer and a plurality of non-ohmic particles; A step of forming a cylindrical non-ohmic resistance layer using the non-ohmic composition; and forming an insulating layer so as to cover the outside of the non-ohmic resistance layer; The base elastomer has: an elastomer (A) having relatively high compatibility with the non-ohmic particles, and The elastomer (B) has relatively low compatibility with the non-ohmic particles. The elastomer (A) contains more non-ohmic particles than the elastomer (B) and constitutes a sea phase. The elastomer (B) constitutes an island phase, In the process of preparing the non-ohmic composition, The base elastomer and the plurality of non-ohmic particles are mixed so that: when the electric field intensity applied to the non-ohmic composition is set to E and the volume resistivity of the non-ohmic composition is set to ρ, the absolute value of the change in the slope of logρ with respect to logE when the non-ohmic composition is uniaxially stretched by 50% becomes the threshold electric field intensity E at the maximum point. th Relative to E without stretching the non-ohmic composition th Less than 1.4 times.

14. The method for manufacturing a cable connection unit according to claim 13, wherein: In the process of preparing the non-ohmic composition, The plurality of non-ohmic particles are dispersed in a network shape in the base elastomer.

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