JP6819151B2 - Method of estimating the remaining life of laminated structures - Google Patents

Description

The present invention relates to a method for estimating the remaining life of a laminated structure.

In a laminated structure in which a plurality of layers are bonded to each other, the boundary of the lamination may be peeled off due to aged deterioration or usage conditions, and the strength and function may be deteriorated.
For example, a resin-coated paper capacitor bushing, which is a type of transformer bushing, has a structure in which insulating paper coated with phenol resin is wound and compacted coaxially while being alternately laminated with metal foil. In this type of bushing, the insulating paper is peeled off due to the deterioration of the phenol resin over time, and the product life is reached due to the deterioration of the insulating property. As a method for diagnosing deterioration of a bushing, a method is known in which an electrode is attached to the outer peripheral portion of the core and the degree of deterioration is diagnosed by measuring dielectric loss tangent, capacitance, and insulation resistance (see Patent Document 1).
Further, as a method for diagnosing deterioration of a laminated product, a method for diagnosing the degree of deterioration from a measured hardness value based on the relationship between hardness and mechanical strength is also known (see Patent Document 2).

Japanese Unexamined Patent Publication No. 3-277951 Japanese Unexamined Patent Publication No. 6-331523

Although it is possible to diagnose the deteriorated state of the bushing performance by the method described in Patent Document 1, it is not possible to estimate the remaining life of the bushing to be diagnosed.
In the method described in Patent Document 2, the relationship between mechanical strength and hardness is calculated by repeatedly measuring the tensile fatigue strength, and deterioration due to peeling of the laminated structure cannot be estimated.

The present invention has been made in view of the above-mentioned problems of the prior art, and it is possible to appropriately estimate the occurrence of deterioration due to the peeling of the laminated structure, and to easily estimate the remaining life of the laminated structure. The purpose is to provide a method.

One aspect of the method for estimating the remaining life of a laminated structure in the present invention includes a step of producing a plurality of test pieces using at least a part of the laminated structure including a plurality of thin layers bonded to each other, and the first method. The test piece is heat-treated under the first temperature condition, and each time a predetermined heating time elapses, the test piece is supported at both ends in the stacking direction of the thin layer, and the tensile strength at which the thin layer breaks is measured. A first test in which a tensile test and a test piece repair in which the broken thin layer is adhered to reprepare the test piece are repeatedly executed to derive a tensile strength at which the test piece first breaks at each heating time. The step and the second test piece are heat-treated under a second temperature condition different from the first temperature condition, and each time a predetermined heating time elapses, the tensile test and the test piece repair are performed. Based on the results of the second test step of repeatedly executing the test to derive the tensile strength at which the test piece first breaks at each heating time, and the results of the first test step and the second test step, the heating temperature and the test It includes a step of deriving a relationship with a heating time in which the tensile strength at which the piece first breaks is below the threshold.

Further, in the method for estimating the remaining life of a laminated structure according to the present invention, when the test piece to be subjected to the tensile test is first broken in the first test step and the second test step, the test piece is broken. A method may be used in which the number of portions is counted as the first number of breaks of the thin layer, the test piece is repaired, and then the tensile test and the test piece repair are repeatedly executed.

Further, in the method for estimating the remaining life of a laminated structure according to the present invention, the laminated structure may be a capacitor core for capacitor bushing.

Further, in the method for estimating the remaining life of a laminated structure according to the present invention, the laminated structure may be a three-dimensional model in which resin layers are laminated.

Further, in the method for estimating the remaining life of a laminated structure according to the present invention, the laminated structure may be a laminated rubber member in which a plurality of plate members and a plurality of rubber layers are alternately laminated.

According to the above-mentioned method for estimating the remaining life of the laminated structure, the occurrence of deterioration due to the peeling of the laminated structure can be appropriately estimated, and the remaining life of the laminated structure can be easily estimated.

The flowchart which shows the process of the remaining life estimation method of the laminated structure which concerns on one Embodiment of this invention. It is a perspective view which shows a part of a transformer bushing as a laminated structure which concerns on this invention. The figure for demonstrating the process of making a test piece from a part of a laminated structure. (A) to (e) are diagrams for explaining the first test process. The graph which shows the result of the tensile test. The graph which shows the estimation (temperature: 70 degreeC constant) of the first fracture stress considering the actual number of fractures. The figure which shows the Arrhenius curve which calculated the temperature (50 ℃, 70 ℃, 80 ℃) and the heating time (2000h, 4000h) of a test piece as parameters about the stress shown in Table 1. The figure for estimating the life evaluation of a transformer bushing.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Method for estimating the remaining life of laminated structures]
In the present invention, the remaining life of the transformer bushing is estimated as a laminated structure.

FIG. 1 is a flowchart showing a process of a method for estimating the remaining life of a laminated structure according to an embodiment of the present invention. FIG. 2 is a perspective view showing a part of a transformer bushing as a laminated structure according to the present invention. FIG. 3 is a diagram for explaining a process of producing a test piece from a part of a transformer bushing. 4 (a) to 4 (e) are diagrams for explaining the first test step.

In the remaining life estimation method shown in FIG. 1, first, at least a part of the transformer bushing is used to prepare a plurality of test pieces to be used for processing (step S1). The transformer bushing (laminated structure) 1 is a capacitor core 16 in which a central conductor 12 and an insulating paper (thin layer) 14 on which electrodes are formed coated with phenol resin are concentrically wound around the outer periphery of the central conductor 12. It consists of a resin-coated paper capacitor with a laminated structure.

Here, a transformer bushing 1 containing a plurality of insulating papers 14 adhered to each other is cut in a direction intersecting the axial direction thereof and sliced to a predetermined thickness to obtain a sample 18 as shown in FIG. To make. Further, as shown in FIG. 3, in the sample 18, a rod-like shape having a length in the stacking direction of the insulating paper 14 adhered to each other by cutting out a predetermined region around the axis of the central conductor 12 and the capacitor core 16 in the radial direction. A plurality of test pieces 20 of the above are prepared. In the present embodiment, five first test pieces 20A and 20B, five second test pieces 20C and 20D, and five third test pieces 20E and 20F are prepared.

Next, in order to perform a tensile test by heating and deteriorating a plurality of test pieces, five of each of the test pieces 20A to 20F are heated at different temperatures and times. In the present embodiment, the breaking stress of each test piece 20A to 20F is measured by performing a tensile test on each test piece forcibly deteriorated at a predetermined temperature.

1. 1. First test step 1-1. (First test piece 20A: set temperature "50 ° C", heating time "2000h")
First, a tensile test is performed on the five first test pieces 20A.
Of the plurality of produced test pieces 20, five first test pieces 20A are placed in a heat treatment device, and heat treatment is performed by setting the first temperature condition to 50 ° (step S2).

When the heat treatment of the plurality of first test pieces 20A has passed the heating time "2000 h" (step S3), five first test pieces 20A are taken out from the heat treatment apparatus and broken into each first test piece 20A. It is confirmed whether or not (peeling between the insulating papers 14) has occurred (step S4).

In the process of producing the above-mentioned test piece, the test piece may be broken due to interfacial peeling between the insulating papers 14 adhered to each other due to vibration during cutting or the like. It is confirmed whether or not the first test piece 20A taken out from the above is broken. When the first test piece 20A is broken, a repair is performed to re-prepare the test piece by applying an adhesive to the fracture surface and adhering the peeled insulating papers 14 to each other (step S41). The number of broken points in one test piece is not limited to one, and there may be a plurality of broken points. In that case, all the broken points are repaired.

On the other hand, if no breakage is confirmed in the first test piece 20A at the time of taking out from the heat treatment apparatus, the first test piece is set in the tensile tester 2 as shown in FIG. 4A, and the tensile test is performed. It is carried out (step S5). In the tensile test, both ends of the first test piece 20A (both ends in the stacking direction of the insulating paper 14) are supported by the respective tensile test jigs 21 and 22, and the tensile strength is measured. At this time, both ends of the first test piece 20A are attached to the tensile test jigs 21 and 22, respectively, via an adhesive. Then, by pulling the movable jig 22 in one direction with respect to the fixing jig 21 (step S51), a tensile stress is applied to the first test piece 20A in the laminating direction of the insulating paper 14. The tensile stress is increased until the first test piece 20A breaks, and the breaking stress when the first test piece 20A breaks is measured as shown in FIG. 4 (b). Then, as shown in FIG. 4C, an adhesive is applied to the fracture surface (the surface of the insulating paper 14 whose interface has been peeled off) to repair the broken portion (step S52). Subsequently, as shown in FIG. 4D, a tensile test was performed again on the repaired first test piece 20A, and as shown in FIG. 4E, the first test piece 20A broke again. Measure the breaking stress at the time of The fractured part in the second tensile test is different from the repaired part in the first tensile test.

In this way, the tensile test and the repair work are repeatedly executed up to a preset number of times. In this example, the fractured portion was repaired and completely adhered, and then the tensile test was performed, and the tensile test was repeated 8 times or more in total for one test piece. In this way, the same tensile test is performed on the other four first test pieces 20A.

1-2. (First test piece 20B: set temperature "50 ° C.", heating time "4000h")
Next, a tensile test is performed on the five first test pieces 20B.
The first test piece 20B is heated at 50 °, which is the first temperature condition, and when the heat treatment has passed the heating time “4000 h”, five first test pieces 20B are taken out from the heat treatment apparatus and broken. Check for the presence of. If there is a break, repair it and then perform a tensile test. If it is not broken, perform a tensile test as it is. The tensile test is carried out in the same manner as in the case of the first test piece 20A described above, and the tensile test is repeatedly carried out for each of the first test pieces 20B eight times or more in total.
In this way, the tensile strength at break of the first test pieces 20A and 20B is measured for each heating time.

2. 2. Second test process 2-1. (Second test piece 20C: set temperature "70 ° C.", heating time "2000h")
Next, a tensile test is performed on the five second test pieces 20C.
The second test piece 20C is heated at 70 °, which is the second temperature condition, and when the heat treatment has passed the heating time “2000 h”, five second test pieces 20C are taken out from the heat treatment apparatus and broken. Check for the presence of. If there is a break, repair it and then perform a tensile test. If it is not broken, perform a tensile test as it is. The tensile test is carried out in the same manner as in the case of the first test piece 20A described above, and a total of eight or more tensile tests are repeatedly carried out on each of the second test pieces 20C.

2-2. (Second test piece 20D: set temperature "70 ° C", heating time "4000h")
Next, a tensile test is performed on the five second test pieces 20D.
The second test piece 20D is heated at 70 °, which is the second temperature condition, and when the heat treatment has passed the heating time “4000 h”, five second test pieces 20D are taken out from the heat treatment apparatus, and the second test piece 20D is taken out. The subsequent processes are executed in the same manner as in the first test step, and a total of eight or more tensile tests are repeatedly performed on each second test piece 20D.
In this way, the tensile strength at break of the second test pieces 20C and 20D is measured for each heating time.

3. 3. Third test process 3-1. (Third test piece 20E: set temperature "80 ° C.", heating time "2000h")
Next, a tensile test is performed on the five third test pieces 20E.
The third test piece 20E is heated at 80 °, which is the third temperature condition, and when the heat treatment has passed the heating time “2000 h”, the five third test pieces 20E are taken out from the heat treatment apparatus, and the third test piece 20E is taken out. The subsequent processes are executed in the same manner as in the first test step, and a total of eight or more tensile tests are repeatedly performed on each third test piece 20E.

3. 3. Third test step 3-2. (Third test piece 20F: set temperature "80 ° C", heating time "4000h")
The third test piece 20F is heated at 80 °, which is the third temperature condition, and when the heat treatment has passed the heating time “4000 h”, the five third test pieces 20F are taken out from the heat treatment apparatus, and the third test piece 20F is taken out. Subsequent processes are executed in the same manner as in the first test step, and a total of eight or more tensile tests are repeatedly performed on each third test piece 20F.
In this way, the tensile strength at break of the third test pieces 20E and 20F is measured for each heating time.

When the tensile test for all the test pieces is completed and all the test pieces in the heat treatment apparatus are exhausted, it is determined that the heat treatment is completed (step S6), and the heat treatment is completed (step S7).

[Tensile test results]
FIG. 5 is a graph showing the results of tensile tests, showing the relationship between the number of tensile tests and the maximum stress. In FIG. 5, as an example, the test results from the first to the eighth of the plurality of tensile tests performed on each of the five test pieces accelerated and deteriorated at a heating temperature of 70 ° C. and a heating time of 4000 h. (Relationship between number of times and maximum stress) and its average are shown. As shown in FIG. 5, it was confirmed that the maximum stress (tensile strength) tends to increase with the number of tensile tests. In addition, it was confirmed that the results of the tensile test on the test pieces of other parameters having different heating temperatures and heating times had the same tendency.

[Remaining life evaluation]
Next, the remaining life is evaluated based on the tensile test results of each test piece.
The tensile test results for the initial (normal temperature) test pieces that have not been forcibly deteriorated by heating are shown as "initial", and the tensile strength of each test piece with a heating time of 2000 hours at each heating temperature (50 ° C, 70 ° C, 80 ° C). The average results of the tests were compared with the average results of the tensile tests on each test piece having a heating time of 4000 h at each temperature (50 ° C, 70 ° C, 80 ° C).

In the following, as an example, a comparison was made based on the test results for a test piece that was accelerated and deteriorated at a heating temperature of 70 ° C.
FIG. 6 is a graph showing the estimation of the first fracture stress (temperature: constant at 70 ° C.) in consideration of the actual number of fractures. In the figure, the vertical axis shows the maximum stress and the horizontal axis shows the actual number of fractures. In the present embodiment, the number of breaks in the test piece in the initial state, which is thought to have occurred during the preparation of the test piece, is added as the initial number of breaks between the insulating papers 14, and the actual number of breaks is arranged. For example, if the test piece has two fractures in the initial state (normal temperature) before the tensile test, the number of fractures in the tensile test is counted as if there were two fractures.

As shown in FIG. 6, in the initial test piece, since there was one fractured part after the test piece was manufactured, it is considered that the tensile test was performed once, and the result of performing the tensile test a total of 10 times is shown. It was. Since the test piece having a heating time of 2000 h and the test piece having a heating time of 4000 h each had three fracture points after the preparation of each test piece, it is considered that each test piece was subjected to a tensile test three times. The results of carrying out a total of 8 or more tensile tests are shown.

From the results shown in FIG. 6, the relationship between the actual number of fractures (11 times) and the maximum stress (average of 5 test pieces) is that the stress increases as the actual number of fractures increases and the tensile strength increases regardless of the heating time. There is a tendency.

Further, the stress at which the initial test piece breaks at the first time can be estimated from the transition of the approximate curve shown in FIG. The stress at which this initial test piece breaks the first time is defined as the reference stress σ [N / cm ² ].

Even in a test piece with a heating time of 2000 hours, the relationship between the actual number of fractures (9 times) and the maximum stress (average of 5 test pieces) is that the maximum stress increases as the actual number of fractures increases, and the tensile strength tends to increase. Can be seen. From the transition of the approximate curve, it can be estimated that the stress at which the test piece accelerated and deteriorated at 70 ° C. and 2000 h breaks at the first time is about 0.78σ [N / cm ² ] as compared with the reference stress σ.

Even in a test piece with a heating time of 4000 h, the relationship between the actual number of fractures (8 times) and the maximum stress (average of 5 test pieces) is that the maximum stress increases as the actual number of fractures increases, and the tensile strength tends to increase. Can be seen. From the transition of the approximate curve, it can be estimated that the stress at which the test piece accelerated and deteriorated at 70 ° C. and 4000 h breaks at the first time is about 0.62σ [N / cm ² ] as compared with the reference stress σ.

Table 1 is a table showing the relationship between the heating temperature and the heating time and the first breaking stress.
From Table 1, it was found that the higher the heating temperature and the longer the heating time, the lower the breaking stress tended to be.

FIG. 7 is a diagram showing an Arrhenius curve obtained by using the temperature (50 ° C., 70 ° C., 80 ° C.) and heating time (2000h, 4000h) of the test piece as parameters with respect to the stress shown in Table 1. The relationship between the first fracture stress and the fracture time is shown for each heating time (initial, 2000 h, 4000 h). Here, with respect to the initial value σ [N / cm ² ] of the breaking stress, 30% of the initial value is set as a threshold value (breaking stress judged to be the product life). The threshold value is not limited to 30% of the initial value, and is set from the measurement result of the test piece collected from the one in which deterioration actually occurs.

Next, an approximate curve is created based on Table 1, and the time required to fall below the threshold value is estimated for each heating time.

In the case of the test piece subjected to accelerated deterioration at a heating temperature of 50 ° C., it is estimated from the approximate curve created based on the data in Table 1 that the test piece drops below the threshold value shortly before the elapse of 100,000 hours. In the case of the test piece subjected to accelerated deterioration at a heating temperature of 70 ° C., it is estimated from the approximate curve created based on the data in Table 1 that the test piece drops below the threshold value when about 10,000 hours have passed. In the case of the test piece subjected to accelerated deterioration at a heating temperature of 80 ° C., it is estimated from the approximate curve created based on the data in Table 1 that the test piece drops below the threshold value after about 8000 hours.

In this way, based on the results of the first test step, the second test step, and the third test step described above, the relationship between the heating temperature and the heating time at which the tensile strength at which each test piece first breaks is below the threshold value is determined. Derived.

FIG. 8 is a diagram for estimating the life evaluation of the transformer bushing.
Here, a life estimation line is created from the relationship between the time for lowering the threshold stress estimated in FIG. 7 and the heating temperature, and the number of years to reach the life when the transformer bushing is used at a predetermined temperature is estimated.
As shown in FIG. 8, when used at 25 ° C., the service life is estimated to be about 380000 hours (about 43 years). On the other hand, when used at 40 ° C., the service life is estimated to be about 175,000 hours (about 20 years). Furthermore, when used at 50 ° C, it takes about 130,000 hours (about 15 years), when it is used at 70 ° C, it takes about 55,000 hours (about 6 years), and when it is used at 80 ° C, it takes about 25,000 hours (about 3 years). Year) is estimated to be the lifespan.

According to the remaining life estimation method of the present embodiment, the strength of the transformer bush, which is a laminated structure, is evaluated by repeatedly performing a tensile test of the test piece and grasping the adhesive force when the actual number of fractures is the first. It can be performed. By performing a plurality of tensile tests on one test piece, the strength of the weakest part can be known from the fact that the test piece breaks in order from the weakest part. By grasping the tendency of the strength of the transformer bushing to decrease, it is possible to diagnose the deterioration over time and estimate the remaining life of the transformer bushing for how many years it can be used at the temperature of the usage environment.

According to the method for estimating the remaining life of a laminated structure of the present invention, in addition to the transformer bushing, a three-dimensional model (3D printer) in which resin layers are laminated, or a plurality of plate materials and a plurality of rubber layers are alternately laminated. It is possible to evaluate the remaining life of a laminated structure such as a laminated rubber member, which has a product life due to peeling of the laminated interface.

1 ... Transformer bushing (laminated structure), 14 ... Insulating paper (thin layer), 16 ... Capacitor core, 20 ... Test piece

Claims (5)

A step of preparing a plurality of test pieces using at least a part of a laminated structure containing a plurality of thin layers bonded to each other, and
Among the specimens, those that heat treatment at the first temperature condition as the first test piece, and set each different heating times for a plurality of said first test strip, after the heating time has elapsed , tensile and test the thin layer and supports the respective first of said test piece at both ends in the stacking direction of the laminate is measured tensile strength to break, first the by bonding the laminate was broken A first test step in which the test piece repair for re-preparing the test piece is repeatedly executed, and the tensile strength at which the first test piece first breaks is derived for each heating time , and the first test step .
A test piece to be heat-treated under a second temperature condition different from the first temperature condition is used as the second test piece, and after the heating time has elapsed , the tension is applied to each of the second test pieces. A second test step in which the test and the repair of the test piece are repeatedly executed, and the tensile strength at which the second test piece first breaks is derived for each heating time , and
A laminated structure including a step of deriving a relationship between a heating temperature and a heating time at which the tensile strength at which the test piece first breaks is below a threshold value based on the results of the first test step and the second test step. How to estimate the remaining life of an object. In the first test step and the second test step,
When the test piece to be subjected to the tensile test is first broken, the number of broken points is counted as the first number of breaks of the thin layer, and after the test piece is repaired, the tensile test and the above The method for estimating the remaining life of a laminated structure according to claim 1, wherein the test piece repair is repeatedly executed. The method for estimating the remaining life of a laminated structure according to claim 1 or 2, wherein the laminated structure is a capacitor core for capacitor bushing. The method for estimating the remaining life of a laminated structure according to claim 1 or 2, wherein the laminated structure is a three-dimensional model in which resin layers are laminated. The method for estimating the remaining life of a laminated structure according to claim 1 or 2, wherein the laminated structure is a laminated rubber member in which a plurality of plate members and a plurality of rubber layers are alternately laminated.

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