JPH10275530A - Method for evaluating reliability of suspension insulator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To estimate a rate of deterioration of real use condition on the basis of the relation between a high-level stress and lifetime by giving a stress at a high level to a suspension insulator, of which material age is accelerated. SOLUTION: A suspension insulator, which is filled with cement, is dipped in the hot water heated at a predetermined temperature so as to accelerate the material age of the cement, and a tensile load for generating a breakdown within a predetermined period is given to the suspension insulator, of which material age is accelerated. Time till a breakdown corresponding to the strength of the tensile load is generated is measured so as to accumulate the probability of breakdown, and a rate of deterioration of the suspension insulator due to the regular use of load is obtained on the basis of the relation between the accumulated rate of breakdown, strength of the tensile load and the time till a breakdown is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspension insulator used in series with a large number of transmission lines, and more particularly, to a method of calculating a deterioration rate of a suspension insulator which has been used for a long period of time to improve its reliability. How to evaluate.

[0002]

2. Description of the Related Art Conventionally, many suspension insulators used in series with a transmission line, as shown in FIG. 5, include a main body 1 made of porcelain, a cap fitting 3, a pin fitting 4, and a And a cement 2 for joining the cap fitting 3 and the main body 1 to the pin fitting 4 respectively.
A main body 1 made of porcelain includes a cap portion 1a and a plurality of folds 1 formed annularly and concentrically on the inner surface of the cap portion 1a.
b and a closed cylindrical head 1c integrally formed at the upper center of the cap portion 1a.

[0003] A cap fitting 3 is fixed on the outer periphery of the head 1 c by a cement 2.
a is formed so as to be able to engage the pin fitting 4 of another suspension insulator connected directly above. The upper part of the pin fitting 4 is fixed inside the head 1c of the main body 1 by the cement 2, and the lower end is engaged with the engaging recess 3a of the cap fitting 3 of another hanging insulator connected directly below.

Here, the head 1c and the cap fitting 3 and the head 1c and the pin fitting 4 are provided on the inner and outer peripheral surfaces of the head 1c of the main body 1.
A sand 5 for mechanically and firmly bonding is attached. The tensile strength of the suspension insulator thus configured is
It is essentially determined by the inherent strength of the porcelain of the body 1, but in addition, the porcelain and pin fittings 4 and cap fittings 3
Is strongly influenced by the strength of the cement 2 for fixing each of them.

[0005] In such a suspension insulator, if the design and quality control are inadequate and the quality of the insulator is insufficient, cracks may occur in the head 1c due to deterioration of the porcelain portion with age. If the insulator with such cracks is used as it is with the insulator interposed between the insulators, flashover occurs in the insulator with intervening insulators due to the discharge of natural lightning, etc. When passing through the part 1c, the arc energy causes an internal explosion at the head 1c, and the insulator loses its mechanical support function, and the power transmission system is seriously hit.

Here, as a test method for evaluating the aging strength of the insulator, a Thermal Mechanical Perm in which a temperature cycle is superimposed on a mechanically repeated load is used.
The performance test (hereinafter referred to as aging test) is standardized by IEC and Canadian Standard (CSA). This test method artificially generates mechanical and thermal stresses in a long-term use state and forcibly deteriorates the insulator. That is, after performing an aging test under predetermined load and temperature conditions, an electrical breakdown load test is performed, and the test result is used as a quality factor Qs of the following formula (1).
Is determined.

[0007]

(Equation 2)

The quality factor Qs is defined in the range of 1.4 to 1.7 according to the number of test samples in the IEC, and 3 in the CSA.
As described above, the criterion is strict. It is known that there is a good correspondence between the aging test result and the deterioration rate of the suspension insulator on the actual line.

[0009]

In the above-described test method, low quality is effective in determining insulators.
It is not enough to verify the reliability of a high quality insulator requiring a life cycle of 0 to 50 years.

Therefore, the present invention estimates the life of a suspended insulator at a normally applied low stress level by obtaining the life distribution of the suspended insulator at a certain high stress level and grasping the relative relationship between the applied stress level and the life. The present invention has been made based on the finding that it is theoretically possible to provide a method of estimating the deterioration rate of a hanging insulator in an actual use state and evaluating the reliability of the insulator.

[0011]

SUMMARY OF THE INVENTION The present invention relates to a method for evaluating the reliability of a suspended insulator which determines the deterioration rate of a suspended insulator which has been used for a short time and for a long period of time and evaluates its reliability. Therefore, in order to solve the above-mentioned problems, in the invention according to claim 1, a suspension insulator filled with cement is immersed in hot water heated to a predetermined temperature to accelerate the material age of the cement, A tensile load is applied to the suspended insulator whose cement age has been accelerated so as to cause breakage within a predetermined period, and the time to breakage in accordance with the magnitude of the applied tensile load is measured to measure the probability of breakage. Thus, the cumulative probability of fracture, the magnitude of the tensile load, and the time until the fracture occurs are determined from the relationship between the suspension insulator and the suspension insulator at normal operating load. Lumber By applying a high stress level tensile load in a state where acceleration is accelerated, the life of the suspension insulator is shortened, and the relationship between the tensile load, the probability of failure and the failure time at this time is determined, and this is extrapolated to the constant operating load. By doing so, the deterioration rate of the suspension insulator in a practical state can be obtained in a short period of time.

In the present invention, the magnitudes of the tensile loads are defined as S ₁ , S ₂ ... Sn, and the magnitudes of the tensile loads are accumulated for each of the magnitudes S ₁ , S _2. Probability of destruction P
₁ , P ₂ ... Pn and the time T ₁ ,
T ₂ ... Tn are measured, and a large number of actual measured values obtained by the measurement are substituted into the following equation (1) to calculate m / (n + 1), m · n. / (N + 1) and C
Is obtained by the least squares method, and the values of m / (n + 1), mn / (n + 1) and C obtained by the least squares method, the desired time (T), and the constantly used load (S) are calculated. By substituting into the above formula, the probability of destruction (P) at a desired time is calculated, and the deterioration rate of the suspension insulator under the constant use load is obtained.

[0013]

(Equation 3)

Here, m represents a Weibull constant, n represents a constant relating to life, and C represents a constant.

As described above, the magnitudes of the tensile loads S ₁ , S _2.
After having set the · · Sn to a high stress level, failure probability P ₁₁ that is accumulated when the tensile load is S _1, P ₁₂ · · ·
P ₁ n and the times T ₁₁ , T ₁₂ ...
Measured T ₁ n, tensile load the accumulated fracture probability _{P 21, P 22 ··· P 2} n and to failure occurs time _{T 21, T 22 ··· T 2} n when the S ₂ , Pn ₁ , Pn _2, ..., And Pn ₁ , Pn _2, ..., Pnn, and times Tn ₁ , Tn ₂ ,. Measure and find.

Each of the measured values of the plurality of sets is substituted into the equation (3), and m / (n) of the equation (3) is calculated by the least square method.
+1), mn / (n + 1) and C. M / (n + 1), mn /
By substituting (n + 1) and C into the calculation formula of Expression 3, and by substituting the constant use load S and the desired service life T into the calculation expression of Expression 3, the failure probability P can be calculated. This makes it possible to obtain the deterioration rate of the suspension insulator under a constantly used load in a short period of time.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below. As shown in FIG. 5, the suspension insulator is composed of a main body 1 made of porcelain, a cap fitting 3, a pin fitting 4, and a main body 1.
, A cap fitting 3 and a cement 2 for joining the main body 1 and the pin fitting 4 respectively. As the cement 2, portland cement is widely used, and an aggregate is added to impart fluidity to the cement. The strength of the cement after curing differs depending on the amount of the aggregate or the amount of water for mixing, but generally, the hydration reaction progresses with the age of the cement 2 after curing, and the strength of the cement increases. Increase.

A method for testing the physical properties of boltland cement is specified in JIS R5201. This J
In IS R5201, a loading rate of 80 kgf / cm is applied to a specimen cast into a rectangular parallelepiped by casting cement into a mold.
s is applied to determine the compressive strength.

In order to determine the compressive strength of the cement 2 filled in the suspension insulator, the inventors of the present invention used the transmission line for a long time to remove the pin bracket 4 from the removed suspension insulator. Cement 2 was cut into a rectangular parallelepiped shape having a side of 7 mm and a thickness of 4 mm to obtain a sample piece, and the aged characteristics of the compressive strength of the sample piece were determined. FIG. 1 shows the results of the test of the compressive strength. FIG.
As is clear from the test results, the compressive strength increases as the use period is prolonged, but after 10 years, it tends to be saturated, and the hydration reaction of cement converges in about 10 years. It became clear.

A. Age accelerated test As with other chemical reactions, cement hydration accelerates the reaction with increasing temperature. If the hydration reaction is performed while supplying water, the reaction is promoted. From this, it is possible to accelerate the age of the cement filled in the suspension insulator by immersing the suspended insulator in the hot water for a long time. Therefore, the pendant insulator after curing is immersed in hot water of 80 ° C. for 10 days and 3 months, and the pin hole of the pendant insulator accelerates the material age.
Cement was cut out into a rectangular parallelepiped shape having a side of 7 mm and a thickness of 4 mm, and specimens A and B with accelerated material age were obtained. The compressive strength of the specimens A and B accelerated with this age was determined.

When the test results of the compressive strength were applied to the data of FIG. 1, the results shown in FIG. 2 were obtained. As is evident from the test results in FIG.
The compressive strength of the suspension insulator (sample A), which was immersed in hot water at 0 ° C. for 10 days and accelerated the material age, was almost equal to the compressive strength of the suspension insulator whose use period was 5 years. The compressive strength of the suspension insulator (sample B), which was immersed in hot water at 80 ° C. for 3 months to accelerate the material age, was almost equal to the compressive strength of the suspension insulator having a service period of 10 years or more. From this, it can be seen that if the suspended insulator after curing is immersed in hot water at 80 ° C. for 3 months to accelerate the material age, a suspended insulator having a service period of about 10 years can be obtained.

Therefore, the hydration reaction of cement is almost 1
After converging in a few years, 80%
The compressive strength of a suspension insulator immersed in hot water for 3 months for three months to accelerate the material age is almost equal to the compressive strength of a suspension insulator used for 40 or 50 years.

B. S, P, T relation In the case of a pendant insulator, the porcelain of the pendant insulator that has been used for a long time tends to deteriorate due to the progress of hardening and shrinkage of the cement, and the tensile breaking load of the porcelain decreases. In order to determine this, it is necessary to first determine the S, P, and T relationships. However, since the suspension insulator generally breaks at the metal fittings, the S, P, and
When obtaining the T relationship, it is necessary to use a strong metal fitting made of high-tensile steel so as to prevent the metal part from being broken.

After such preparation, the magnitude S of the tensile load applied to the suspension insulator (Stress) and the probability of fracture (P
(robability) P and fracture time (Time) T
, That is, the S, P, and T relationships were determined as follows.

The tensile load applied to the test insulator is obtained by calculating the average tensile breaking load of the porcelain by a method in which the load is increased at a constant rate so that the breaking occurs within a few seconds to one year after the application of the load. 95% (S ₁ ) to 75% (Sn)
A load level of ~ 4 is set, and a plurality of test insulators are connected and exposed outdoors. Then, for each of the set load of each of the set load S _1, S ₂ ··· Sn, measures the time T _1, T ₂ ··· Tn until the breakdown occurs, destruction probability P _1, P ₂ · ································· Although Pn is accumulated, fluctuations in tension due to temperature changes during the day and night were also measured, and the hydraulic circuit was controlled so that accuracy of ± 1% of the set load could be secured.

In this manner, the magnitudes of the tensile loads S ₁ , S ₂ ... Sn applied to the hanging insulators, the probability of destruction P ₁ , P _{2 for} each Sn
.. Pn and the measured values of the destruction times T ₁ , T _2, ... Tn are plotted on Weibull probability paper (see FIGS. 3 and 4). From these measured values, the relative relationship among S, P, and T is obtained, and parameters for calculating the deterioration rate of the suspension insulator are obtained. The S, P, T relationship of the porcelain destruction can be expressed by the following equation (2) obtained from the porcelain delayed destruction phenomenon.

[0027]

(Equation 4)

Here, the left side of the above equation (2) represents the vertical axis of the Weibull probability paper, and lnT on the right side represents the horizontal axis. Therefore, the slope of the plotted data is m / (n +
1). M is a parameter representing the distribution variation, and the larger the value, the smaller the characteristic variation. Further, n is a parameter indicating the dependence of the life on the tensile load, and a larger value indicates a longer life.

Therefore, S, P, obtained from the actually measured data,
From the T relation, m / (n + 1), mn /
If the solution of (n + 1) and C is obtained by the least square method,
It is possible to derive the values of m and n. Then, given the values of m and n, it is possible to estimate the deterioration rate under the constant use load. This will be described below.

C. S, P, of the suspended insulator which accelerated the material age
T characteristics Therefore, the suspended insulators after curing were immersed in hot water at 80 ° C for 3 months to accelerate the material age. The S, P, T relationship was determined. Each test insulator A,
The tensile load S applied to B is the average value of the tensile fracture load of the porcelain (test insulator A is 21500 kgf, test insulator B is 400
00 kgf) of 0.95 (S ₁ ), 0.85 (S ₂ ),
0.75 (S ₃ ). The tensile load level is set as described above, and a plurality of test insulators A and B are connected to each other and exposed outdoors.

In this way, by applying a high stress level tensile load to a plurality of test insulators A and B,
The number of test insulators destroyed with time increases.
Then, set at a tensile load S _1, together with measuring the time _{T 11, T 12 ··· T 1} n until breakdown occurs, Weibull cumulative destruction probability _{P 11, P 12 ··· P 1} n Plot on paper. Similarly, in the setting tensile load S _2, with measuring the time _{T 21, T 22 ··· T 2} n until breakdown occurs, and the cumulative fracture probability _{P 21, P 22 ··· P 2} n Weibull Plot on probability paper. Further, at the set tensile load S ₃ , the time T ₃₁ until fracture occurs,
With measuring the T ₃₂ ··· T ₃ n, destruction probability P _31,
P ₃₂ ... P ₃ n are accumulated and plotted on Weibull probability paper. As a result, data as shown in FIGS. 3 and 4 is obtained. FIG. 3 shows the test results of the test insulator A, and FIG. 4 shows the test results of the test insulator B.

As apparent from FIGS. 3 and 4, S,
Since the relationship between the slope of the straight line representing the relationship between P and T and the measured data at each set tensile load show a good correspondence, the relationship between S, P and T of the measured data is extrapolated to the actual use load range. However, there is no problem in calculating the deterioration rate.

[0033] Therefore, the test insulators A, for each of the B, measured data (i.e., T ₁₁ at S _1, T ₁₂ · ·
T ₁ n and P ₁₁ , P ₁₂ ... P ₁ n, T in S _2
21, T ₂₂ ··· T ₂ n and _{P 21, P 22 ··· P 2} n, S
T ₃₁ at _3, T ₃₂ ··· T ₃ n and P _31, P ₃₂ ··
* P ₃ n) is substituted into Expression (2), and m /
When the solutions of (n + 1), mn / (n + 1) and C are calculated using the least squares method and the values of the constants m and n are obtained, as shown in Table 1 below, m is 8 to 9, n was in the range of 45 to 53.

[0034]

[Table 1]

As apparent from Table 1, m / (n +
1) is 0.15 to 0.2, and mn / (n + 1) is 8 to 9. These m / (n + 1) and mn /
Since (n + 1) is a coefficient of the tensile load S and the breaking time T as shown in Expression (2), it indicates that the deterioration rate of the suspension insulator is more dependent on the use load than on the years of use.

Here, it is assumed that the deterioration rate when the actual working load such as 1/2, 1/4, 1/5 of the guaranteed value is applied to the sample insulators A and B, for example. For the sample insulators A and B, m / (n + 1) and mn / (n +
1) By using m, n, and C, these values are substituted into the above equation (2) to determine the cumulative failure probability (P) when 50 years (T = 2.6 × 10 ⁷ ) are used, Sample A
Calculation of the number of deteriorations per 100,000 B results in the results shown in Table 2 below.

[0037]

[Table 2]

Note that the guaranteed value (guaranteed value of electrical breakdown load) in Table 2 above is 12,000 for the sample A.
kgf and 21,000k for sample B
gf was used.

Generally, in the design of a transmission line, the load that is always used is 1/4 to 1/1 / the guaranteed value of the applied breaking load.
As is clear from Table 2 above, in 1/5 of the guaranteed value of the electric breakdown load, 0.4 to 10 million pieces was obtained.
3 pieces, 1/4 of the guaranteed value of the electric breakdown load, 100
A calculation result is that 4 to 20 degradations appear for 100,000.

This calculation result has a good correspondence with the number of deterioration of the suspension insulator on the actual line. Therefore, by considering the age of the cement, it is possible to derive the deterioration rate of the suspension insulator in a long-term use state from the S, P, and T relationships.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the time of a hanging insulator used for a long time and the compressive strength.

FIG. 2 is a diagram showing test results obtained by applying the compressive strength of a suspended insulator with accelerated cement age to FIG.

FIG. 3 is a plot of the tensile load, the time to failure, and the cumulative failure probability of the sample A with accelerated cement age on Weibull probability paper, and shows the relationship between the time to failure and the cumulative failure probability with respect to the tensile load. FIG.

FIG. 4 is a plot of the tensile load, the time to failure, and the cumulative failure probability of the sample B with accelerated cement age on Weibull probability paper, and shows the relationship between the time to failure and the cumulative failure probability with respect to the tensile load. FIG.

FIG. 5 is a sectional view showing a schematic configuration of a suspension insulator.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Body, 2 ... Cement, 3 ... Cap fitting, 4 ... Pin fitting

Claims (2)

[Claims] 1. A method for evaluating the reliability of a suspension insulator which determines a deterioration rate of a suspension insulator which has been used for a short time and for a long time, and evaluates the reliability of the suspension insulator. Immersing in hot water heated to a temperature to accelerate the age of the cement, applying a tensile load such that breakage occurs within a predetermined period to the suspended insulator in which the age of the cement is accelerated, Measuring the time until breakage occurs in accordance with the magnitude of the tensile load, accumulating the fracture probability, the accumulated fracture probability and the magnitude of the tensile load,
A method for evaluating the reliability of a suspension insulator, wherein a deterioration rate of a suspension insulator under a constant operating load is determined from a relationship with a time until the breakage occurs. 2. The method according to claim 1, wherein the magnitude of the tensile load is S ₁ , S _2.
Sn, and for each of the magnitudes of the tensile loads S ₁ , S _2, ... Sn, the accumulated failure probability P ₁ , P _2, ... Pn and the time T ₁ , T _2. ··· Tn is measured, and a number of actual measured values obtained by measuring these are substituted into a calculation formula of the following Expression 1 to obtain m / (n + 1), m · n /
The values of (n + 1) and C are obtained by the least squares method, and m / (n + 1), mn /
The values of (n + 1) and C, the desired time (T), and the constant use load (S) are substituted into the above-described calculation formula, and the probability of destruction (P) at the desired time is calculated, and The method for evaluating the reliability of a hanging insulator according to claim 1, wherein a deterioration rate of the hanging insulator is obtained. (Equation 1) Here, m represents a Weibull constant, n represents a constant relating to life, and C represents a constant.