JPH11344433A - Method for diagnosing deterioration of covered cable and method for estimating remaining life - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for diagnosing the deterioration of a covered cable and a method for estimating a remaining life of the covered cable after the deterioration diagnosis. SOLUTION: In the deterioration diagnostic method, places where cable deterioration is likely to speed rapidly are grasped by a plurality of deterioration factor-measurement means installed along a covered cable, and a deterioration diagnostic characteristic Sts for a reference temperature at those places is examined. In the mean time, in a method for estimating a remaining life, the remaining life is estimated based on the time required for characteristics at the starting time for estimating the remaining life of the organic polymer material to reach a predetermined life value at a scheduled operation temperature of the covered cable after the deterioration diagnosis by utilizing a plurality of Arrhnius curves having deterioration degree judgment characteristics (for example, a breaking elongation rate) for the organic polymer material for forming a covering layer as parameters, thus the deterioration of the covered cable can be correctly diagnosed. Meanwhile, the covered cable can be removed before reaching the estimation life, and an dielectric breakdown accident and a fire accident of the covered cable can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for diagnosing deterioration of a covered cable and a method for estimating a remaining life.

[0002]

2. Description of the Related Art Many organic polymer materials are degraded by heat, sunlight, radiation or other causes, and various properties of the organic polymer materials are changed to some extent as the deterioration proceeds. On the other hand, since various coating cables such as power cables, communication cables, and indoor power distribution lines are formed of such organic polymer materials, power failures and fire accidents may occur due to deterioration of the organic polymer materials. There is. For this reason, it is necessary to periodically measure and monitor changes in certain characteristics of the coating layer, such as the ultrasonic wave propagation characteristics, of the coated cable in operation.

[0003] The laying environment of the covered cable generally differs in the longitudinal direction of the covered cable, and therefore, the degree of deterioration of the covered cable varies in the longitudinal direction.
In general, cable parts exposed to an environment that tends to accelerate the deterioration of organic polymer materials such as high temperatures will progress faster, and the insulation breakdown of the coated cable due to deterioration will be
Usually, it is likely to occur at a site where deterioration progresses quickly. Therefore, although the deterioration diagnosis of the sheathed cable should be given priority to the cable part exposed to the environment where deterioration is likely to occur, conventionally, it is not appropriate to select such a deterioration diagnosis part without using a proper diagnosis. It was a reality to go about the parts. For this reason, there is often a discrepancy between the estimated life of the coated cable obtained from the deterioration diagnosis and the actual life (for example, the actual operation period that led to cable breakage). In other words, in the conventional method, the actual state of the deterioration of the coated cable is grasped. Had a problem.

[0004] Further, conventionally, it has been proposed to diagnose the degree of deterioration of the coated layer of a coated cable in operation by a non-destructive inspection such as an ultrasonic wave propagation characteristic. In addition to the deterioration, the temperature changes greatly depending on the temperature of the coating layer (organic polymer material) at the time of measurement, and therefore, there has been a problem that deterioration diagnosis of the coated cable cannot be performed correctly and reliability is lacking.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for diagnosing deterioration of a coated cable in which the reliability of deterioration diagnosis is improved in view of the above. It is a further object of the present invention to provide a method for estimating the remaining life of a covered cable after an arbitrary point in time, such as after a deterioration diagnosis.

[0006]

The above-mentioned objects can be solved by the following methods. (1) (Step 1) In at least one section of a laid covered cable having a covering layer formed of an organic polymer material, a plurality of cables are arranged so that the distribution of the strength of the cable deterioration factor in the longitudinal direction of the cable can be grasped. (Step 2) A portion where the strength of the deterioration factor is high in the longitudinal direction of the coated cable is known from the measurements by the plurality of deterioration factor measurement means, and (Step 3) at least the strength of the deterioration factor is high. Deterioration degree diagnostic characteristics S are actually measured for the part,
(Step 4) The measured value of the deterioration degree diagnostic characteristic S is calculated based on the temperature dependence of the deterioration degree diagnostic characteristic S at the reference temperature.
(Step 5) Deterioration diagnosis of the coated cable based on the value of the deterioration degree diagnosis characteristic Sts or the value of the deterioration degree judgment characteristic C obtained from the correlation between the deterioration degree diagnosis characteristic Sts and the deterioration degree judgment characteristic C And a method for diagnosing deterioration of the coated cable. (2) Deterioration factor measurement means are as follows: temperature of coated cable, presence or absence of underwater immersion of coated cable, pH of immersion water in case of immersion in coated cable underwater, presence or absence of oil on coated cable, atmospheric humidity, atmospheric humidity Measure at least one item selected from the group consisting of hydrogen sulfide concentration, atmospheric oxygen concentration, atmospheric radiation dose, solar radiation, strain of the coated cable after installation, and vibration applied to the coated cable after installation. And / or a method for diagnosing deterioration of a coated cable according to the above (1), which can be detected. (3) Deterioration degree diagnostic characteristics S are based on the ultrasonic propagation characteristics, surface rebound hardness, and the like of the organic polymer material forming the coating layer of the coated cable.
The method for diagnosing deterioration of a coated cable according to the above (1) or (2), which is at least one selected from the group consisting of surface penetration hardness, torsion torque of the coated cable, and bending stiffness of the coated cable. (4) at least one material selected from the group consisting of the organic polymer material forming the coating layer, the reproduced material of the organic polymer material, and a similar material similar to the reproduced material, Tensile strength, elongation at break, elastic modulus, Young's modulus, modulus, dielectric constant, dielectric loss tangent, volume resistivity,
(1) to (1) which are at least one selected from the group consisting of AC breakdown voltage strength and impulse breakdown voltage strength;
(3) The method for diagnosing deterioration of a coated cable according to any one of (3) and (4). (5) The similar material is based on an organic polymer of the same kind as the organic polymer used as the base of the reproduction material, and its degradation level diagnostic characteristic Sts is ± 2 of its value of the reproduction material.
The method for diagnosing deterioration of a coated cable according to the above (4), which has a value within 0%. (6) A similar material, wherein the organic polymer material forming the coating layer is a composition based on a specific organic polymer containing at least one selected from the group consisting of a plasticizer, a filler, and carbon black. In some cases, when at least one of the above is a plasticizer, the same type of plasticizer is used. When it is a filler, its compounding amount or its compounding amount is used. (5) The method for diagnosing deterioration of a coated cable according to the above (5), wherein the method comprises a quantity or a blended quantity close to the quantity. (7) In estimating the remaining life of the coated cable having the coating layer formed of the organic polymer material, (step α) the organic polymer material forming the coating layer, a reproduction material of the organic polymer material, And at least one material selected from the group consisting of similar materials similar to the reproduction material, the deterioration degree diagnostic characteristics Sts or the deterioration degree diagnostic characteristics Sts and the deterioration degree determination characteristics C
A correlation (th-h correlation) between the heating temperature t and the heating time h using the deterioration degree determination characteristic C obtained from the correlation with the parameter as a parameter is established experimentally (step β). The ht correlation for at least one parameter value arbitrarily selected from the relationships is determined as the life ht correlation, and (step γ) the value of the degradation degree diagnostic characteristic Sts of the covered cable laid for a certain period or the value thereof. A value of the deterioration degree determination characteristic C having a correlation is obtained by the method according to any one of the above (1) to (6), and (step δ) at the average temperature of the coating layer of the coated cable after the above-mentioned fixed period of installation. The above step β
The heating time h1 and the process γ on the life-th correlation determined by
The heating time h2 on the ht correlation with the value of the deterioration degree diagnostic characteristic Sts or the value of the deterioration degree
(Step ε) The remaining life of the coated cable is defined as the remaining life of the coated cable based on the time difference between the heating time h1 and the heating time h2. (8) The heating temperature t in the tha correlation is the absolute temperature T
And the heating time h is the logarithm of the heating time.
(7) The method for estimating the remaining life of the coated cable described in (7).

[0007]

By disposing a plurality of deterioration factor measuring means along the laid cable, the distribution of the strength of the deterioration factor in the longitudinal direction of the coated cable can be grasped. When the part having the strong deterioration factor is known correctly, the degradation diagnostic characteristic S of the coated cable at that part is actually measured, and the measured value is converted into the degradation diagnostic characteristic Sts at the reference temperature to perform the degradation diagnosis of the coated cable. Do. Therefore, in the present invention, since the deterioration degree of the portion where the progress of deterioration is considered to be fast is determined by the characteristic value which is not influenced by the temperature at the time of characteristic measurement, the deterioration diagnosis of the coated cable is performed. improves. Further, the t− established in step α of the invention of (7)
h Estimating the remaining life of the coated cable in the process ε based on the expected or artificially determined average temperature of the coating layer of the coated cable after the installation for a certain period of time using the correlation. Can be.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

In step 1 of the invention (1), a plurality of deterioration factor measuring means are installed so that the distribution of the strength of the cable deterioration factor can be grasped along the longitudinal direction of the laid covered cable. At this time, the entire installation section of the covered cable may be subjected to the deterioration diagnosis. However, if only a certain section is particularly susceptible to deterioration depending on the installation condition, the deterioration factor measuring means is provided only in the certain section. It can be installed and targeted for diagnosis.

[0010] The deterioration factor measuring means is installed in the longitudinal direction along the laid cable. As the deterioration factors in the present invention, various factors that deteriorate the coated cable can be targeted. Typical examples are temperature, humidity and water, pH of water, oil, hydrogen sulfide, oxygen,
Ozone or other reactive gases, sunlight, radiation, etc., which chemically degrades the material of the coating layer of the coated cable, or causes strain at the various parts of the coated cable or vibration caused by external force, etc. And those that mechanically degrade.

Among the means for measuring the deterioration factors, the temperature of the coated cable, whether or not the coated cable is immersed in water, the pH of the immersion water when the coated cable is immersed in water, the presence or absence of oil on the coated cable, the humidity in the atmosphere , The concentration of hydrogen sulfide in the atmosphere,
Measurement and / or detection of at least one item selected from the group consisting of oxygen concentration in the atmosphere, radiation dose in the atmosphere, insolation, strain of the covered cable after installation, and vibration applied to the covered cable after installation ( Hereinafter, measurement and detection are collectively referred to simply as measurement.)

The intervals at which the deterioration factor measuring means are installed differ somewhat depending on the type of the deterioration factor to be measured, the installation condition of the covered cable, and the environment. For example, the radiation dose in a well-ventilated outdoor environment, the concentration of reactive gas such as hydrogen sulfide, oxygen, and ozone in the atmosphere, the humidity, the amount of solar radiation, and the like are substantially constant over a relatively wide range. An interval is sufficient. On the other hand, since the radiation dose received by the coated cable laid in the nuclear power plant, the immersion of the coated cable laid on the road in the production plant in water and the adhesion of oil occur in a relatively narrow range, about 1 to 10 m, and in some cases, 0.5 ~
It is preferable to install them at intervals of about 2 m. In short, the determination may be made in consideration of the width of the range in which the degradation factors to be measured are considered to be substantially the same. The installation interval is generally 0.5
It is about 50 m, especially about 1-10 m.

Next, an example of a method of installing each deterioration factor measuring means will be described. The means for measuring the temperature of the covered cable may be installed using an adhesive tape or the like so that the temperature-sensitive portion contacts the surface of the covered cable.

Humidity in the atmosphere, hydrogen sulfide concentration, oxygen concentration,
Each of the means for measuring the amount of solar radiation or radiation dose has its sensing part in contact with or near the coated cable, for example, 1 to 50 c from the surface of the coated cable.
It may be installed by an arbitrary method in the atmosphere about m away.

[0015] Each of the means for measuring the presence or absence of underwater immersion of the coated cable and the pH of the immersion water in the case of immersion in water are immersed in the water so that the sensing portion thereof comes into contact with the lower surface to the middle surface of the coated cable. It should be installed so that it can freely come into direct contact with water when it is done.

As means for measuring the presence or absence of oil adhesion of the coated cable, for example, a method in which a rubber having a rubber which swells with oil and changes the electric resistance value in the sensing portion is exemplified. And preferably in contact with the surface of the coated cable.

After the cable is laid, the sheathed cable expands and contracts due to a temperature change due to the suspension of the cable itself, a temperature change of a cable support used for laying the sheathed cable, deformation due to an external force, or a change in the sheathed cable itself. Such an external force causes various types of distortion (deformation) such as elastic distortion and permanent distortion (plastic deformation). For example, torsion or bending of the entire covered cable or deformation of the cross-sectional shape of the covering layer. The measurement of the strain of the coated cable in the present invention may be performed for any one or more of such strains.For example, regarding the deformation of the cross-sectional shape of the coating layer, a strain gauge capable of measuring a change in the outer diameter of the cable is used for the cable. It can be measured by placing it in

[0018] Vibration generated at the place where the covered cable is laid, for example, vibration of the ground due to long-term civil engineering work near the place where the covered cable is laid, vibration of the building itself when the laid place is inside the building, covered cable for movement With regard to the above, the whole or a part of the coated cable may vibrate due to vibration of the cable itself caused during movement. When the vibration generated in the coated cable is due to the vibration at the installation location as described above, the vibration measuring means may be fixed to the coated cable,
Alternatively, it may be installed near the coated cable. on the other hand,
It is necessary to fix the covered cable for movement to the cable. In addition, since vibration may occur due to various causes other than the above case, it is generally preferable to fix the vibration measuring means to the coated cable.

The measurement by at least one of the above-mentioned deterioration factor measuring means may be performed continuously or at regular time intervals. In the latter case, it is slightly different depending on the measurement items, but generally, about once / hour to once / day is appropriate. However, depending on the strength of the deterioration factor and the type of the coated cable, about once / year may be sufficient.

The measurement by the above-mentioned deterioration factor measuring means is continued for a certain period of time, for example, 0.5 to 5 years immediately after the cable is laid, and the strength of the deterioration factor during that period is measured and integrated. The distribution of the strength of the deterioration factor is known, and from the distribution, a section or a place where the integrated amount of the strength is particularly large, in other words, there is a high possibility that the deterioration of the coated cable is particularly advanced is found (step 2).

When a section or a place where deterioration is particularly likely to progress is grasped in step 2, in step 3, the deterioration degree diagnosing characteristic S of at least the coated cable existing in such a portion is measured. In the present invention, the deterioration degree diagnostic characteristics include, for example, ultrasonic propagation characteristics of the coating layer, surface rebound hardness, surface penetration hardness and the like, or mechanical characteristics of the coated cable itself, for example, torsion torque of the coated cable,
Characteristics that can be measured nondestructively, such as the bending stiffness of the coated cable, are used.

Since the method of measuring the ultrasonic wave propagation characteristics of the organic polymer material and the coating layer of the coated cable is well known in the art,
In the present invention, such a well-known method, for example,
For example, the method described in JP-A-35732 or JP-A-7-35733 may be used. The ultrasonic wave propagation characteristics include an ultrasonic wave propagation speed, an ultrasonic wave propagation time (including a reciprocal of the ultrasonic wave propagation time, and the like).

When the organic polymer material loses its elasticity due to chemical deterioration and hardens, the surface rebound hardness and the surface penetration hardness increase, and the torsional torque and bending rigidity of the coated cable itself also increase. Therefore, deterioration diagnosis can be performed from these characteristics.

The method for measuring the surface rebound hardness is described in
As is well known in Japanese Patent No. 0370 and Japanese Patent Application Laid-Open No. 8-313423, a steel indenter (ball impactor) is caused to collide with the surface of the sample to be inspected. Are measured, and the speed ratio is defined as the surface rebound hardness. The higher the surface hardness of the coating layer, the greater the speed at which the indenter reflects. The surface penetration hardness can be measured from a pressing load when the pressing needle is pressed into the organic polymer material. On the other hand, the torsional torque and bending stiffness of the coated cable can be measured from the load required by applying the torsional torque and bending while the coated cable itself is in a live state.

Since the temperature at the time of measuring the deterioration degree diagnostic characteristic S usually changes depending on the installation location of the covered cable, the cable load, the season, and the like, in step 4, the value of the deterioration degree diagnostic characteristic S actually measured at the temperature t is obtained. Deterioration diagnostic characteristics S separately established
Is converted into a value at the reference temperature ts, that is, a deterioration degree diagnostic characteristic Sts, based on the temperature dependency of the temperature (hereinafter, St correlation). At this time, the St correlation is basically established by examining the coated cable itself to be diagnosed and measuring the degradation diagnostic characteristic S of the coated cable itself or its coating layer at various temperatures. be able to.

The St correlation can be established by the following alternative method other than the above method.
As a test material for examining the St correlation, a reproduction material having the same composition as the organic polymer material forming the coating layer of the coated cable to be diagnosed and separately prepared in a laboratory or the like, At least one of similar materials having a similar composition is used. The reproduction material can be formulated and prepared from the specifications of the organic polymer material itself or by analyzing the material itself to grasp its composition. Examples of the above-mentioned similar materials include various compositions based on the same organic polymer as the specific organic polymer used in the organic polymer material itself.
Are used within a difference of ± 20% or less of that of the reproduction material. Next, the test material is formed into a suitable processed product, for example, a sheet having a thickness of about 0.5 to 5 mm or a coated cable having the same structure as the coated cable to be diagnosed. When the organic polymer material of the coated cable to be diagnosed is a crosslinked product, the test material is crosslinked during molding. Finally, the deterioration degree diagnostic characteristics S of the thus obtained processed product are measured at various temperatures.

Next, among the deterioration degree diagnostic characteristics S, two types of ultrasonic wave propagation characteristics and surface rebound hardness are selected, and an example of establishing the St correlation for each of them will be described. In the following, when reference is made to the deterioration degree diagnostic characteristics S as a superordinate concept without using specific examples such as the ultrasonic wave propagation characteristic and the surface rebound hardness, the deterioration degree diagnostic characteristics S ,
The terms “St correlation” and “deterioration degree diagnostic characteristic Sts” are used, and in the case of the ultrasonic propagation characteristic as a specific example included in the degradation degree diagnostic characteristic S, the ultrasonic propagation characteristic V and its St
The correlation is specially displayed as a Vt correlation, and the value of the ultrasonic wave propagation characteristic V at the reference temperature ts is shown as an ultrasonic wave propagation characteristic Vts. As for the surface rebound hardness, similarly to the above, the surface rebound hardness H, Ht correlation, the surface rebound hardness H
Display as ts respectively.

[Vt correlation] A cross-linked polyethylene insulating layer having a thickness of 2 mm is provided on a stranded copper conductor having a diameter of 10 mm,
For a 600 V power cable having a 1.5 mm thick plasticized polyvinyl chloride composition sheath layer thereon, an undegraded cable test piece taken from the cable and the cable test piece were heated to 110 ° C. Prepare a deteriorated cable test piece which was heat-degraded for 300 hours in a controlled oven, and left for about 2 hours in an oven whose temperature was controlled at 5 ° C., 25 ° C., and 40 ° C., and then in the oven, The ultrasonic wave propagation characteristics V of the sheath layer were measured. The result is shown in FIG. In FIG. 1, G1 is a graph for an undegraded cable test piece, and G2 is a graph for a deteriorated cable test piece. G1, G
2 The ultrasonic wave propagation characteristic V (correctly, the ultrasonic wave propagation velocity (m / s)) and the temperature t (° C.) in both graphs are as follows.
Vt which can be expressed by the following equations (1) and (2), respectively
There is a correlation, and the proportionality constant a in both equations is-
It turns out that it is 5.5. Therefore, the sheath layer of the above power cable, regardless of whether it is undegraded or deteriorated cable, has the ultrasonic propagation having the following general formula (3) based on the Vt correlation of the formula (1) or (2). Characteristics Vts
-It was confirmed that the temperature relational expression was satisfied. V = at + 2280 (1) V = at + 2020 (2) Vts = −5.5 (ts−tx) + Vtx (3) (Vtx is the ultrasonic wave propagation characteristic V at the temperature tx (temperature at the time of measurement).)

[Ht Correlation] For the same 600 V power cable used in establishing the Vt correlation described above, a large number of cable test pieces taken from the cable were heated to 110 ° C. The heating time was changed in two stages in the adjusted oven to cause heating deterioration, and thus two groups of deteriorated cable samples having different degrees of deterioration were obtained. The average elongation at break of the sheath layer of the deteriorated cable sample included in the first group was 101.5%, and that of the second group was 341.3%. Next, the deteriorated cable samples of the above two groups were allowed to stand in ovens controlled at 9 ° C., 23 ° C., and 40 ° C. for about 2 hours, and then the surface rebound hardness H of each sheath layer was measured in the oven. The result is shown in FIG. In FIG. 2, G3 is a graph for the deteriorated cable sample of the first group,
4 is a graph of the deteriorated cable sample of the second group. From the above measurement data, the first group (Graph G3) can be expressed by the following equation (4), while the second group (Graph G4) can be expressed by the following equation (5). A possible Ht correlation was obtained. It can be seen that the proportional constants (−7.53 and −7.47) of these equations are substantially equal to each other, and the average value is −7.50. H = −7.53t + 813.3 (4) H = −7.47t + 501.8 (5) However, as for the sheath layer in the above power cable, at least up to the degree of deterioration at which the elongation at break decreases to 100%. For example, it can be seen from the expressions (4) and (5) that the surface rebound hardness Hts-temperature relationship having the following general formula (6) holds regardless of whether the cable is undegraded or deteriorated. Hts = −7.50 (ts−tx) + Htx (6) (where Htx is the surface rebound hardness at the temperature tx (temperature at the time of measurement), and Hts is the surface rebound hardness at the reference temperature ts.)

Many coated cables having a coating layer of various organic polymer materials having different types of specific organic polymers also have different proportional constants depending on the material type, but generally have the above general formula (3).
And a linear or substantially linear temperature relationship such as Equation (6). Note that, with the progress of deterioration, St
There are cases where the proportionality constant of the correlation changes, and cases where the St correlation changes from a primary type to a quadratic type, etc. In such a case, the deterioration degree diagnostic characteristic Sts-temperature depends on the degree of deterioration. What is necessary is just to change a relational expression. However, even in such a case, there is a light deterioration stage in which the residual ratio from the initial value such as the tensile strength or the elongation at break is about 70% or more, and a severe deterioration stage in which the residual ratio is about 70% or less. It is often practically sufficient to simply divide the deterioration degree diagnostic characteristics Sts-temperature relational expression for each stage into two stages.

In the step 4, the reference temperature ts can be arbitrarily selected. However, from the establishment of the St correlation in the step 4, the deterioration degree diagnosing characteristic S is corrected without difficulty to the deterioration degree diagnosing characteristic Sts. It is preferred that the temperature be obtained. When the relationship is established in a temperature range of, for example, 15 to 50 ° C., the reference temperature ts is, for example, 25 ° C.

In the step 3 of the present invention, the characteristics of the coated cable actually measured for the deterioration diagnosis are the deterioration diagnosis characteristic S and the temperature t of the coated cable itself and its coating layer to be diagnosed. The deterioration degree diagnostic characteristic S itself can be measured by the method described above. The temperature t is usually the average temperature of the entire coating layer except for the surface rebound hardness, but in many cases, it can be replaced by the surface temperature of the coating layer.

If the temperature t of the coating layer at the time of actually measuring the deterioration diagnostic characteristic S is different from the reference temperature ts, in step 4, the measured value is obtained by the deterioration diagnostic characteristic Sts-temperature relational expression. The deterioration degree of the coated cable is diagnosed from the value of the deterioration degree diagnosis characteristic Sts and the like in step 5 described later.

In step 5, the deterioration diagnosis of the coated cable may be performed based on the value of the deterioration degree diagnosis characteristic Sts itself.
On the other hand, the tensile strength, elongation at break, modulus of elasticity, Young's modulus, modulus, dielectric constant, dielectric loss tangent, volume resistivity, AC breakdown voltage strength, impulse breakdown voltage strength, or other properties of the organic polymer material forming the coating layer Since the mechanical or electrical characteristics of the above directly indicate the degree of deterioration of the coated cable, they are more suitable for determining the degree of deterioration. Therefore, in the present invention, instead of the deterioration degree diagnostic characteristics S, the above mechanical or electrical characteristics (hereinafter, these characteristics are referred to as deterioration degree determination characteristics C) are selected from the group consisting of the above characteristics. The degree of deterioration of the coated cable may be diagnosed by at least one of the obtained types.

When the deterioration degree judgment characteristic C is adopted for the deterioration diagnosis of the coated cable, a correlation between the deterioration degree diagnosis characteristic Sts and the deterioration degree judgment characteristic C (hereinafter, this correlation is referred to as Sts-C correlation). ) Is separately established, and the deterioration degree diagnostic characteristics Sts obtained in steps 3 and 4 are converted into deterioration degree determination characteristics C using the Sts-C correlation. As the Sts-C correlation, for example, a correlation between the ultrasonic wave propagation characteristic Vts and the elongation at break, a correlation between the surface rebound hardness Hts and the elongation at break,
A correlation between the ultrasonic wave propagation characteristic Vts and the impulse breakdown voltage intensity, a correlation between the surface rebound hardness Hts and the volume resistivity, and the like can be exemplified.

To establish the Sts-C correlation, the above-described S
As in the case of establishing the -t correlation, the organic polymer material itself forming the coating layer of the coated cable to be diagnosed has the same composition as the organic polymer material itself and is reproduced separately in a laboratory or the like. At least one of a material or a similar material similar to the reproduction material may be used as the test material. Sts-C correlation indicates that the test material is 0.5-5 m.
m, into a sheet or covered cable, etc., and degrade to various degrees by irradiation, heating, etc. in the form of such a molded product, and the degradation degree diagnostic characteristics Sts and degradation for each molded product with different degrees of degradation It can be established by measuring the degree determination characteristic C. Examples of the above-mentioned similar materials include various compositions based on the same organic polymer as the specific organic polymer used in the organic polymer material itself. In the case of Vts, those whose ultrasonic propagation characteristics Vts coincide within ± 20% or less of that of the reproduction material are used.

The Sts-C correlation generally varies somewhat depending on the deterioration conditions of the organic polymer material. However, for each of the above test materials, for example, room temperature to about 250 ° C. and / or
Or irradiation, for example, 10 Gy / h to 10 kGy /
The Sts-C correlation obtained when deteriorated by irradiation of about h can be practically used for deterioration diagnosis of many coated cables deteriorated under other conditions. However, in order to perform a more accurate deterioration diagnosis, the test material is deteriorated under conditions that reproduce or approximate the deterioration factors grasped by the inventions of (1) and (2) above, and the deterioration test material thus obtained is obtained. It is preferable to establish a Sts-C correlation for.

The mechanical properties such as tensile strength, elongation at break, modulus of elasticity, Young's modulus and modulus among the properties C for judging the degree of deterioration are determined by the dumbbell sample punched from the test material.
It can be measured by a normal method specified in IS, ASTM, and the like, and the electrical properties such as dielectric constant, dielectric loss tangent, and volume resistivity can be measured for a sheet of the test material using a sharing bridge. In general, measurement breakdown data such as AC breakdown voltage strength and impulse breakdown voltage strength tends to vary, but it is desirable to obtain an average value by a statistical method using a Weibull distribution or the like.

The above-mentioned test materials include various compounding agents specific to the specific organic polymer used as the base of the materials, for example, antioxidants and antioxidants such as ultraviolet absorbers, processing aids, Several kinds of plasticizers, stabilizers, pigments, crosslinking agents, crosslinking aids, fillers, carbon black and others are blended in usual amounts specific to each blending agent.

The above-mentioned specific organic polymer is generally a synthetic or natural polymer having a mechanical strength that can be used as a so-called mechanical structural material. Examples of organic polymers include polyethylene, cross-linked polyethylene, polypropylene, polybutene, and poly-4 in resins.
For rubbers such as polyolefins such as methylpentene-1, polyamides such as nylon, polyvinyl chloride, polyvinylidene chloride, thermoplastic polyester, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, and polytetrafluoroethylene. Natural rubber, isoprene rubber, butyl rubber, ethylene-propylene copolymer rubber, ethylene-propylene-diene terpolymer rubber, styrene-butadiene copolymer rubber, acrylonitrile-butadiene copolymer rubber, ethylene-vinyl acetate copolymer rubber, ethylene- ethyl acrylate copolymer rubber, chloroprene rubber, chlorosulfonated polyethylene rubber, epichlorohydrin rubber, silicone rubber, fluorine rubber, a thermoplastic elastomer and ABA triblock (AB) _n X type radians Polyolefin-based thermoplastic elastomers such as styrene-based thermoplastic elastomers such as blocks, blended TPO, partially cross-linked blended TPO, fully cross-linked blended TPO, and polyvinyl chloride-based heat such as nitrile rubber blends and partially cross-linked nitrile rubber blends Thermoplastic elastomers, polyurethane-based thermoplastic elastomers such as polyester and polyether,
Examples include polyester-based thermoplastic elastomers such as polyester / polyether type and polyester / polyester type. Above all, resins such as polyvinyl chloride, polyethylene, cross-linked polyethylene, polypropylene, and polytetrafluoroethylene, which are frequently used as organic polymers for cables, chloroprene rubber, ethylene-propylene copolymer rubber, ethylene-propylene-diene Rubbers such as original copolymer rubber, chlorosulfonated polyethylene rubber, and silicone rubber.

According to the study of the present inventors, for many compounding agents, the presence or absence of the compounding agent in each of the usual amounts does not affect the St-C correlation due to deterioration of the test material. When at least one of the agents, fillers and carbon black is blended, the type of the plasticizer and the blending amount of the filler and carbon black slightly vary depending on the blending amount.
Therefore, in the present invention, Sts is improved by the following improved method.
Preferably, a -C correlation is established.

In the above-mentioned improved method, first, the organic polymer material forming the coating layer of the coated cable to be diagnosed is
It is checked whether or not it contains at least one of a plasticizer, a filler, and carbon black. When the organic polymer material contains at least one of them, if it is a plasticizer, its kind, if it is a filler, its compounding amount,
Focusing on the amount of carbon black, its Sts-C correlation is established for test materials having such plasticizer types or amounts.

Examples of the plasticizer include dimethyl phthalate, diethyl phthalate, dibutyl phthalate,
Phthalic acid derivatives such as di-n-octyl-phthalate, diphenyl-phthalate, diisodecyl-phthalate and di-n-alkyl-phthalate; isophthalic acid derivatives such as dimethyl-isophthalate; di- (2-ethylhexyl) tetrahydrophthalate Tetrahydrophthalic acid derivatives such as dibutyl-adipate, diisodecyl-adipate, di-n-octyl-adipate, di-
adipic acid derivatives such as n-alkyl-adipate,
Tri- (2-ethylhexyl) trimellitate, tri-
n-octyl-trimellitate, tri-isooctyl-
Trimellitate, tri-isodecyl-trimellitate,
Tri-isononyl-trimellitate, higher alcohol-
Trimellitic acid derivatives such as trimellitate, or other acid derivatives.

Examples of fillers include calcium carbonates such as light calcium carbonate and heavy calcium carbonate, clays such as hard clay, soft clay, calcined clay and silane modified clay, and talc such as mistro vapor talc. , Silica, wollastonite, zeolite, diatomaceous earth, silica sand, barium sulfate, calcium sulfate, lithobone, magnesium oxide, molybdenum disulfide and the like.

Examples of carbon black include channel blacks, SAF, ISAF, N-339, HA
Furnace blacks such as F, MAF, FEF, SRF, GPF, and ECF; thermal blacks such as FT and MT; and conductive blacks such as acetylene black and Ketjen black.

Whether or not the organic polymer material forming the coating layer of the coated cable to be diagnosed contains at least one of a plasticizer, a filler, and carbon black can be examined by various methods. . If the cable manufacturer considers its own insulated cable to be diagnosed, its manufacturing specifications will indicate this, and the cable user will specify the organic polymer material and have the cable manufacturer produce the insulated cable for diagnosis. And so on.

Even in cases other than the cases described above, the type of the organic polymer which is the base of the organic polymer material can be determined from the printing on the surface of the coated cable, and if the type of the organic polymer is known, the plasticizer, filler, and The presence or absence of carbon black can be estimated with a considerably high probability. Alternatively, take a small amount of organic polymer material from the coated cable,
This can be discriminated by subjecting it to thermogravimetric analysis or infrared absorption spectrum measurement.

When the organic polymer is polyvinyl chloride, a plasticizer is usually compounded, and the type thereof is determined and the amount of the compound is measured by, for example, using a solvent (acetone, methanol, T
The surface of the organic polymer material of the coated cable is rubbed with absorbent cotton containing HF or the like to collect a plasticizer, and the components in the absorbent cotton are analyzed by infrared absorption spectrum, GPC (gel filtration chromatography), HPLC (high-performance liquid). Chromatography).

When the organic polymer is a polyvinyl chloride or rubber-based material, a filler is usually compounded, and the amount of the compound is determined by taking a small sample (several mg) from the coated cable, and converting it to TGA ( It can be quantified by analyzing by thermogravimetric analysis). If the organic polymer is a rubber-based material, carbon black is also compounded in addition to the filler, and the compounding amount may be obtained by collecting a sample in the same manner as in measuring the compounding amount of the filler.

Next, a method for establishing the Sts-C correlation will be described. Regarding the effect of the type of plasticizer in the relationship, the difference between the individual members of each acid derivative is generally small except for the difference between the acid derivatives. Therefore, in the present invention, when the specific name of the plasticizer to be blended is known, the Sts-C correlation may be established for the plasticizer with the specific name. Name of the acid derivative of the agent, for example,
The relationship may be established with phthalic acid derivatives, isophthalic acid derivatives, and the like.

When the organic polymer material is, for example, an ethylene-propylene-diene terpolymer rubber containing both a specific amount of a filler and a specific amount of carbon black, the organic polymer material containing the specific amount of the filler is used. Preparing a rubber test material, or a rubber test material comprising the specified amount of carbon black,
A Sts-C correlation is established for any of the test materials.

The organic polymer material is ethylene-propylene-containing a specific amount of a filler and a specific amount of carbon black.
When containing a filler and carbon black, such as a diene terpolymer rubber, as described above, the rubber test material containing a specific amount of filler or the rubber test material containing the specific amount of carbon black The Sts-C correlation may be established for either one of them, or may be established from both of them. In the latter case, there may be a difference between the one established from one side and the one established from the other side. In such a case, the average value of the two will improve the accuracy of the deterioration diagnosis. In addition, test materials containing both a specific amount of filler and a specific amount of carbon black
When the ts-C correlation is established, more accurate deterioration diagnosis can be performed. The same is true for plasticizers and fillers and / or
Alternatively, this also applies to an organic polymer material containing carbon black.

As described above, the type of the plasticizer, particularly its acid derivative, greatly affects the Sts-C correlation. However, some of the acid derivatives, such as trimellitic acid derivatives, also greatly affect the St-C correlation. Therefore, when establishing the Sts-C correlation,
When the specific name of the plasticizer used or the name of the acid derivative is known, the presence or absence of the influence of the blending amount of the plasticizer or the acid derivative is checked in advance, and if there is, the specific amount of the plasticizer is determined. Alternatively, a test material containing a similar acid derivative may be used.

In establishing the Sts-C correlation, the blending amount of the plasticizer, filler or carbon black in the organic polymer material in the coated cable to be diagnosed coincides with that in the test material. Although it is preferable, an error of about ± 5% of the compounding amount in the organic polymer material is acceptable.

Each of the test materials described above contains a plasticizer, a filler or other compounding agents other than carbon black, which are usually compounded in an organic polymer material, such as a stabilizer, an antioxidant, a pigment, and a processing aid. It may or may not be blended. When the test material is a rubber composition, it is used after being crosslinked in advance with a usual crosslinking agent and a crosslinking technique.

On the other hand, when the above-mentioned improved method is applied to a general or wide range of deterioration diagnosis of a coated cable regardless of whether the composition of the organic polymer material of the coated cable is unknown or known, the following method is used. Like First, the type and amount of plasticizer for each organic polymer, the amount of filler,
A large number of test materials having different amounts of carbon black are prepared, each test material is deteriorated in the same manner as described above, and necessary items are measured for the deteriorated sample. In this way, a number of Sts-C correlations (hereinafter, referred to as "data group") can be established with the types and amounts of the plasticizer, the amount of the filler, and the amount of the carbon black as parameters. .

The types of organic polymers frequently used as the organic polymer material of the coated cable are at most about ten or more, including those described above, of which the plasticizer is compounded. It is only polyvinyl chloride, and as a plasticizer, it may be an acid derivative name without being an individual specific name, and it is a phthalic acid derivative or trimellitic acid derivative even if it is an acid derivative that is frequently used. . Therefore, it is practically sufficient to establish the above data group only for organic polymers and plasticizers used frequently. The amount of the plasticizer, filler and carbon black in the above test materials includes the range of the amount used in the practical coated cable, and about 5 to 10 points within a wider range.
A variable amount is sufficient.

In the above-described improvement method, it is preferable to prepare a recording medium on which the following deterioration diagnosis program is recorded. The recording medium is composed of the type of organic polymer used for the organic polymer material of the coated cable to be diagnosed, the type and amount of plasticizer mixed with the organic polymer, the amount of filler, and carbon black. A procedure for inputting the blending amount of the input information as input information, and a procedure for selecting data having the same conditions as the input information from the data group,
A program for causing a computer to execute a procedure for inputting deterioration diagnosis characteristics Sts of an organic polymer material to be diagnosed and calculating a deterioration degree determination characteristic C from the input value and the selected data. .

In the present invention, the remaining life of the coated cable laid for a certain period can be estimated by a method having the following steps α to ε. First, in step α, as in the case of establishing the Sts-C correlation described above, the organic polymer material itself forming the coating layer of the coated cable to be diagnosed has the same composition as the organic polymer material itself. At least one of a reproduction material prepared separately in a laboratory or the like or a similar material similar to the reproduction material is used as a test material, and the material is used as a suitable processed product, for example, a sheet or a coated cable to be diagnosed. A correlation between the heating temperature t and the heating time h (hereinafter, t-
h correlation) is established experimentally. As an example of the t-h correlation, t-
h correlation, tha correlation using the elongation at break as a parameter, and the like.

Hereinafter, t- with the elongation at break as a parameter
The h correlation is taken up, its establishment method, and the t-
A general method for estimating the remaining life of a coated cable using the h correlation will be described. The following description of the method of establishing the ht correlation and the method of estimating the remaining life also applies to the deterioration diagnostic characteristic S (or the deterioration diagnostic characteristic Sts) and the deterioration determination characteristic C other than the elongation at break.

First, the above-mentioned test material is processed into a sheet having a thickness of, for example, about 0.5 to 5 mm by press working, and this sheet is used as a heat-degraded sample, which is heated at various heating temperatures t for an appropriate time. Heating at each heating temperature t
The change of the elongation at break with respect to the heating time h is measured every time.
At this time, the heating temperature t is preferably as wide as possible and in small increments. However, in general, heating at a low temperature of 90 ° C. or less slows the progress of deterioration, so that the heating temperature is usually 100 to 20 ° C.
It is preferred that the temperature be in the range of 0 ° C. in increments of at least 50 ° C., and in particular in increments of 20 ° C. On the other hand, the heating time h for each heating temperature t is preferably at least one month, especially at least three months. FIG. 3 is a model graph of the result, in which the horizontal axis represents the heating time h and the vertical axis represents the elongation at break (%) using the heating temperature t (t1 to t4) as a parameter.

Next, a constant elongation at break (for example, 20
The relationship between the heating temperature (t1 to t4) at 0%) and the heating time h is read from FIG. 3 and is graphed. FIG. 4 shows an example in which the abscissa represents the reciprocal of the absolute temperature T of the heating temperature t, and the ordinate represents the logarithm of the heating time h. %, 2
T- for each of 00%, 250%, and 300%
2 shows an h correlation, a so-called Arrhenius curve. When obtaining the Arrhenius curve on FIG. 4 from the data read from FIG. 3, it is preferable to obtain a linear equation (straight line) that minimizes the correlation coefficient by the least squares method, or a quadratic or higher polynomial. In many cases, it can be approximated by a linear expression (linear line) in practice.

In step β, the elongation at break shown in FIG.
The t-h correlation for a specific parameter value arbitrarily selected from a plurality of t-h correlations for 00%, 150%, 200%, 250%, 300%, etc.
-H Defined as correlation. At this time, the life-th correlation may be selected and set in consideration of the type of the coated cable, the cable management standard of the cable user, or other circumstances. Here, the elongation at break indicated by the thick line is 10
The 0% tha correlation is temporarily defined as the life tha correlation.

In the step γ, the elongation at break of the organic polymer material forming the coating layer of the coated cable laid for a certain period of time is examined. The elongation at break is determined by the Sts established by the method described above for the deterioration diagnosis method of the present invention. One of the -C correlations, the correlation between the ultrasonic wave propagation characteristic Vts and the elongation at break and the ultrasonic wave propagation characteristic Vts can be known.

Next, in step δ, the average temperature of the coating layer of the coated cable after the installation for the above-mentioned predetermined period is ascertained. The average temperature may be the expected operating temperature of the coated cable determined by the cable user, or the expected operating temperature of the coated cable expected from the cable installation environment. Alternatively, there may be a temporary operating temperature for the cable user to formulate a future cable operation plan. In any case, the life t−h at such average temperature
The heating time h2 on the ht correlation for the heating time h1 on the correlation and the specific elongation at break (specific parameter) obtained in step γ is determined. Assume that the specific elongation at break is, for example, 250%, and thereafter, the case where the coated cable is operated at a temperature at which the average temperature of the coating layer is 60 ° C., 70 ° C., 80 ° C., or 90 ° C. . When the operating temperature is 90 ° C, the elongation at break is 100%
The heating times h1 and h2 on the respective vertical axes at (point a in FIG. 4) and 250% (point b in FIG. 4) are read.

In step ε, the time difference (h1−h2) between the heating time h1 and the heating time h2 is calculated, and the remaining time of the coated cable is estimated based on the calculated time difference. In the same manner as when the operating temperature is 90 ° C., the operating temperature is
It is possible to know the estimated remaining life in the case of ° C, 70 ° C, and 60 ° C.

For example, with respect to an insulated wire having a polyvinyl chloride sheath layer operated at 60 ° C., the elongation at break of the sheath layer was calculated from the ultrasonic wave propagation speed.
Met. When the life of the insulated wire is set when the elongation at break of the sheath layer reaches 100%, 250
The time required to decrease from 100% to 100%, ie, the remaining life, was estimated to be 14 years.

[0068]

According to the present invention, unlike the related art, by installing a plurality of deterioration factor measuring means along the laid cable, deterioration progresses quickly from the strength distribution of the deterioration factor in the coated cable. Detect the part that seems to be
Since the diagnosis of the degree of deterioration of the portion is performed, the life of the covered cable can be correctly known. Furthermore, according to the remaining life estimating method of the present invention, since the remaining life of each of the coated cables that have been operated for a certain period of time after each operating temperature can be estimated,
It can be removed before the end of its useful life and replaced with a new one as needed, thereby preventing insulation damage and fire accidents of the insulated cable.

[Brief description of the drawings]

FIG. 1 is an example of a graph showing a relationship between an ultrasonic wave propagation characteristic V of a covered cable and a temperature t.

FIG. 2 is a graph example showing the relationship between the surface rebound hardness H of the sheath layer and the temperature t.

FIG. 3 is a model graph showing the relationship between the heating time and the elongation at break of the organic polymer material using the heating temperature as a parameter.

FIG. 4 is a graph created by the numerical values read from FIG. 3 and showing the relationship between the reciprocal of the heating temperature (absolute temperature T) and the logarithm of the heating time (th-h correlation) using the elongation at break as a parameter.

[Explanation of Signs] G1 Graph of undegraded cable test piece G2 Graph of degraded cable test piece G3 Graph when average breaking elongation rate of sheath layer is 101.5% G4 Average breaking elongation rate of sheath layer Graph when the elongation at break is a point at an operating temperature (average temperature) of 90 ° C. on a th-h correlation where the elongation at break is 100% b A th-correlation where the elongation at break is 250% The point where the operating temperature (average temperature) above is 90 ° C

Continued on the front page (72) Inventor Tetsuya Ashida 8 Nishinocho, Higashikojima, Amagasaki City, Hyogo Prefecture Inside Mitsubishi Electric Wire Industry Co., Ltd. In company

Claims (8)

[Claims] (Step 1) In at least one section of a covered cable having a covering layer formed of an organic polymer material, a distribution of strength of a cable deterioration factor in a longitudinal direction of the cable can be grasped. A plurality of deterioration factor measuring means are installed in (Step 2) From the measurement by the plurality of deterioration factor measuring means, a portion where the strength of the deterioration factor in the longitudinal direction of the coated cable is high is known, and (Step 3) at least the strength of the deterioration factor. Degradation characteristic S
(Step 4) Convert the measured value of the deterioration degree diagnostic characteristic S into a deterioration degree diagnostic characteristic Sts at a reference temperature based on the temperature dependence of the deterioration degree diagnostic characteristic S, and (Step 5) Deterioration degree diagnosis Characteristics Sts
Or a value of the deterioration degree determination characteristic C obtained from the correlation between the deterioration degree diagnosis characteristic Sts and the deterioration degree determination characteristic C. . 2. The deterioration factor measuring means includes: a temperature of the coated cable, whether or not the coated cable is immersed in water, a pH of the immersion water when the coated cable is immersed in water, whether or not oil is attached to the coated cable, an atmospheric humidity, an atmospheric pressure. At least one item selected from the group consisting of hydrogen sulfide concentration in the atmosphere, oxygen concentration in the atmosphere, radiation dose in the air, solar radiation, the amount of strain on the coated cable after installation, and the amount of vibration applied to the coated cable after installation. The method for diagnosing deterioration of a covered cable according to claim 1, which can be measured and / or detected. 3. The deterioration degree diagnosing characteristic S includes an ultrasonic propagation characteristic, a surface rebound hardness, a surface penetration hardness, a torsion torque of the coated cable, and a coated cable of the organic polymer material forming the coating layer of the coated cable. The method for diagnosing deterioration of a covered cable according to claim 1 or 2, wherein the method is at least one selected from the group consisting of bending stiffness. 4. The deterioration degree determination characteristic C is at least one selected from the group consisting of the organic polymer material forming the coating layer, a reproduced material of the organic polymer material, and a similar material similar to the reproduced material. Tensile strength, elongation at break,
The elastic modulus, Young's modulus, modulus, dielectric constant, dielectric loss tangent, volume resistivity, AC breakdown voltage intensity, and at least one selected from the group consisting of impulse breakdown voltage intensity. Method for diagnosing the deterioration of coated cables. 5. The similar material is based on an organic polymer of the same kind as the organic polymer used as the base of the reproduction material, and within ± 20% of its value of the reproduction material in the deterioration degree diagnostic characteristics Sts. 5. The method for diagnosing deterioration of a coated cable according to claim 4, wherein the method has a value of: 6. A composition in which the similar material is based on a specific organic polymer, wherein the organic polymer material forming the coating layer contains at least one selected from the group consisting of a plasticizer, a filler, and carbon black. In the case of carbon black, when at least one of the above is a plasticizer, the same type of plasticizer is used. 6. The method for diagnosing deterioration of a covered cable according to claim 5, wherein the compounded amount or the compounded amount approximate to the compounded amount is included. 7. Estimating the remaining life of a coated cable having a coating layer formed of an organic polymer material (Step α): Reproducing the organic polymer material forming the coating layer and the organic polymer material. Materials, and at least one material selected from the group consisting of similar materials similar to the reproduction material,
Deterioration degree diagnostic characteristic Sts or correlation between heating temperature t and heating time h using deterioration degree determination characteristic C obtained from correlation between deterioration degree diagnostic characteristic Sts and deterioration degree determination characteristic C (th-h correlation) ) Was established experimentally, and (step β) the t
-H correlation with respect to at least one parameter value arbitrarily selected from the -h correlation is determined as a life ht correlation, and (step γ) the degradation degree diagnostic characteristic Sts of the covered cable laid for a certain period of time is determined. A value or a value of the deterioration degree determination characteristic C having a correlation with the value is obtained by the method according to any one of claims 1 to 6, and (step δ) at the average temperature of the coating layer of the coated cable after the above-mentioned fixed period of installation. Heating time h1 on the life-th correlation determined in step β above
And the heating time h2 on the ht correlation with respect to the value of the deterioration degree diagnostic characteristic Sts or the value of the deterioration degree determining characteristic C obtained in the step γ, (step ε) the heating time h1 and the heating time h
2. A method for estimating the remaining life of a coated cable, wherein the time difference from the value 2 is used as the remaining life of the coated cable. 8. The heating temperature t in the ht correlation is
The method according to claim 7, wherein the heating time h is a logarithm of the heating time, which is a reciprocal of the absolute temperature T.