JP2023140456A - Life evaluation method of pole transformer - Google Patents

Abstract

To provide a life evaluation method for a pole transformer based on gasket deterioration.SOLUTION: A life evaluation method for a pole transformer calculates a current from a smart meter that can measure the amount of current passing through a pole transformer, obtains environmental data around the pole transformer, calculates the gasket temperature using a thermal equivalent circuit for outputting the gasket temperature of the gasket provided in the pole transformer by using the current and the environmental data as input data, and estimates the lifetime of the pole transformer by estimating a deterioration index on the basis of the gasket thermal characteristics, which express the relationship between the gasket temperature and the gasket deterioration index.SELECTED DRAWING: Figure 2

Description

The present invention relates to a method for evaluating the life of a pole transformer.

It is known that the lifespan of pole transformers is shortened mainly due to corrosion of the tank, deterioration of the insulating paper that covers the windings, and deterioration of the gasket used to prevent oil leakage. However, pole transformers are often replaced regardless of their service life based on these factors.

Therefore, a technique has been proposed for estimating the lifespan of a pole transformer based on a current value obtained from a smart meter attached to the pole transformer (for example, Patent Document 1). According to such technology, replacement and maintenance can be performed based on the estimated lifespan of the pole transformer.

On the other hand, although gasket deterioration leads to oil leakage, it is assumed that the gasket temperature will be higher than the air temperature due to the current flowing inside the transformer, but the gasket temperature has not been ascertained. Very little research has been done to understand this. Based on this situation, if gasket deterioration that leads to oil leakage can be ascertained, the lifespan of the pole transformer can be determined, and replacement can be performed after determining the appropriate deterioration status. However, the technique disclosed in Patent Document 1 determines the lifespan based on the deterioration of the insulating paper of the pole transformer, and does not take into account the deterioration of the gasket.

Patent No. 6689212

In view of the above circumstances, an object of the present invention is to provide a method for evaluating the life of a pole transformer based on gasket deterioration.

An aspect of the present invention for achieving the above object is to calculate the current from a smart meter capable of measuring the current passing through the pole transformer, acquire environmental data around the pole transformer, and calculate the current passing through the pole transformer. , and the environmental data as input data, calculate the gasket temperature using a thermal equivalent circuit for outputting the temperature of the gasket provided in the pole transformer (hereinafter referred to as gasket temperature), and calculate the gasket temperature and the gasket temperature. A pole-mounted transformer characterized in that the life of the pole-mounted transformer is estimated by estimating the deterioration index based on the gasket thermal characteristics representing a relationship with an index representing the degree of deterioration (hereinafter referred to as the "deterioration index"). It is in the method of evaluating the lifespan of the device.

According to the present invention, a method for evaluating the life of a pole transformer based on gasket deterioration is provided.

FIG. 2 is a diagram showing a system configuration for evaluating the life of a pole transformer. FIG. 3 is a diagram showing the flow of a method for evaluating the life of a pole transformer. This is an example of a thermal equivalent circuit. It is a figure showing the history of gasket temperature. This is a gasket thermal characteristic that represents the relationship between a deterioration index and a gasket temperature. FIG. 3 is a diagram comparing a gasket temperature calculated without using environmental data such as solar radiation with an actually measured gasket temperature. The gasket temperature calculated using the heat flow due to solar radiation is compared with the actually measured gasket temperature. It is a figure which shows the gasket temperature obtained using the heat flow of the solar radiation obtained from the weather observatory. It is a figure showing gasket temperature obtained using wind speed obtained from a weather observatory. FIG. 6 is a diagram showing a comparison between a calculated value and an actual value of gasket temperature calculated with or without consideration of wind speed and solar radiation. FIG. 3 is a diagram showing a comparison between a calculated value and an actual value of gasket temperature calculated in consideration of wind speed and solar radiation.

A method for evaluating the life of a pole transformer according to an embodiment of the present invention will be described. FIG. 1 is a diagram showing a system configuration for evaluating the life of a pole transformer. In the pole transformer 1 whose life is to be evaluated, a lead wire 3 branched from a high voltage line is guided into a tank 6 via a bushing 4 . Further, the bushing 4 is provided with a gasket 5, and the gasket 5 prevents oil leakage. Inside the tank 6, a transformer main body including windings, an iron core, insulating paper covering the windings, and the like is stored, although not particularly shown. Electric wires 7 are wired from the secondary side of the transformer main body to each customer 10. Since such a pole-mounted transformer 1 is well-known, a detailed explanation of the other components will be omitted.

A smart meter 2 is installed in the consumer 10. The smart meter 2 is a device equipped with a power measurement function and a communication means. The power measurement function is a function that can collect the amount of power supplied via the electric wire 7, and collects the amount of power at a frequency of, for example, once every 30 minutes. The collected power amount is transmitted as smart meter information to the life evaluation device 11 via a dedicated line, which is an example of communication means. The life evaluation device 11, which will be described later, adds up the electric energy of the smart meters 2 of each customer 10 connected to one pole transformer 1 to be evaluated. Thereby, it is possible to grasp the amount of power passing through the pole transformer 1 to be evaluated, and the current passing through the pole transformer from this amount of power.

Observation data from meteorological observatories includes data on temperature, solar radiation conditions, wind speed, etc. The Japan Meteorological Agency publishes this data on its website. Normally, temperature, solar radiation conditions, and wind speed are not actually measured in the pole-mounted transformer 1 to be evaluated, so by using these data, the accuracy of gasket temperature estimation will increase, which will lead to estimation of gasket deterioration status. Accuracy is also improved. These data on temperature, solar radiation, and wind speed are collectively referred to as environmental data. Environmental data is not limited to that provided by the Japan Meteorological Agency, but can also be provided by various organizations. Hereinafter, institutions that provide environmental data will be referred to as meteorological observatories, etc.

The life evaluation device 11 is a general computer, and performs calculations to estimate the deterioration of the gasket of the pole transformer 1 based on environmental data obtained from a weather observatory, etc., and the current obtained from the smart meter 2. do.

Processing in the life evaluation device 11 will be explained using FIGS. 2 to 5. First, as shown in FIG. 2, the life evaluation device 11 acquires the current of the pole transformer 1 from the smart meter 2 (step S1). Since a plurality of smart meters 2 are connected to one pole transformer 1 to be evaluated, the current obtained from each smart meter 2 is totaled, and this total value is calculated as the pole transformer 1 to be evaluated. Let be the current passing through. Since the smart meter 2 measures the current once every 30 minutes, the current passing through the pole transformer 1 is obtained every 30 minutes.

The life evaluation device 11 also acquires environmental data regarding temperature, solar radiation, and wind speed from a weather observatory or the like (step S2). The frequency of acquiring environmental data is not particularly limited, but it is preferable to match the timing with which the current of the smart meter 2 is acquired.

Next, the temperature of the gasket is calculated using the current and environmental data as input data (step S3). Specifically, the input values are current, environmental data, and constants related to the pole transformer 1, and the output is the temperature of the tank 6, the oil temperature in the tank 6, and the gasket 5 (hereinafter referred to as gasket temperature). Calculate the equivalent circuit. Figure 3 shows an example of a thermal equivalent circuit.

[Constant value]
The winding (T1 in the same figure), tank oil temperature (T2 in the same figure), gasket (T3 in the same figure), and air temperature (T0 in the same figure) are connected in series, and there is a Let R1, R2, and R3 be the thermal resistances and C1, C2, and C3 be their heat capacities. These constants are calculated from a temperature rise test of the pole transformer 1, specifications of the pole transformer, and the like.

[Input value]
i is the heat flow [W] generated by the current flowing in the winding of the pole transformer 1. This heat flow can be determined from the current etc. obtained from the smart meter 2. is is the heat flow due to solar radiation. T0 is the temperature (air temperature) around the pole transformer 1. For the heat flow due to solar radiation and the temperature around the pole transformer 1, environmental data obtained from a meteorological observatory or the like is used.

[Output value]
T1 represents the winding temperature of the pole transformer 1. T2 represents the oil temperature in the tank 6 (average temperature between the upper and lower parts). T3 is the bushing gasket temperature.

[Correction for wind and rain effects]
Wind and rain are considered to affect the thermal resistance R3 between the gasket and the air temperature in the thermal equivalent circuit. Specifically, R3 is corrected so that the higher the wind speed obtained from the weather observatory, the lower the thermal resistance. This corrected thermal resistance is defined as surface dissipation thermal resistance R3'. Furthermore, a rain coefficient α, which indicates the degree to which the influence of rain is taken into consideration, is set in the range of 0 to 1. If the influence of rain is not considered at all, the rain coefficient α is set to 1. When considering the influence of rain, set it to a value greater than 0 and less than 1 depending on the degree of influence. By using a resistance value obtained by multiplying the surface heat dissipation resistance R3' by the rain coefficient α, the more the rain influences the thermal resistance R3, the smaller the thermal resistance R3 becomes.

The calculation for obtaining the temperature based on the above-mentioned thermal equivalent circuit is well known, so a detailed explanation will be omitted. As a result, T3, that is, the temperature of the gasket 5 can be obtained. As shown in FIG. 4, the temperature history of the gasket can be obtained by calculating the temperature of the gasket 5 every time environmental data is obtained from the smart meter 2, electric current, weather observatory, etc.

Next, the life of the pole transformer 1 is evaluated from the gasket temperature obtained as described above (step S4 in FIG. 2). Gasket deterioration indicators are used to evaluate lifespan. The deterioration index is an index representing the degree of deterioration of the gasket, and as an example, the compression set rate of the material forming the gasket 5 is used.

FIG. 5(a) shows the gasket thermal characteristics representing the relationship between the deterioration index and the gasket temperature. The horizontal axis of the gasket thermal characteristics represents the gasket temperature, and the vertical axis of the gasket thermal characteristics represents the amount of increase in the deterioration index (compression set rate).

Although the gasket temperature is calculated based on the thermal equivalent circuit, it is assumed that it represents the temperature between the previous and current calculations. In this example, since the gasket temperature is calculated once every 30 minutes, it is assumed that the gasket temperature of gasket 5 was obtained by calculation over a period of 30 minutes.

For example, if the gasket temperature is 60° C. for 30 minutes, the increase in compression set rate is 0.01%. Therefore, the value "0.01" is added to the compression set rate of the gasket 5. Thereafter, each time the gasket temperature is calculated, the amount of increase corresponding to the gasket temperature is obtained from the gasket thermal characteristics, and the amount of increase is added to the compression set rate. As a result, as shown in FIG. 5(b), the deterioration index increases over time.

Note that such gasket thermal characteristics are prepared in advance through actual measurements or simulations. Further, the gasket thermal characteristics are not limited to the case where only one type is used as shown in FIG. 5(a). For example, different gasket thermal characteristics may be prepared for each accumulated time since the gasket 5 has been used. The plurality of gasket thermal characteristics may be switched and used depending on the actual accumulated time of the gasket 5. Even at the same gasket temperature, the amount of increase in the deterioration index may differ depending on the cumulative time of the gasket 5. By switching and using a plurality of gasket thermal characteristics depending on the cumulative time, it is possible to more accurately obtain the amount of increase in the deterioration index.

The compression set rate increases from the initial value due to deterioration. A threshold value (see symbol th in FIG. 5(b)) is provided for such compression set rate. The threshold value is set to a value that serves as a guideline for replacing the gasket 5. The life of the gasket 5 is estimated based on the deterioration index and the threshold value set in this way. One of the estimation methods is to evaluate that the gasket 5 should be replaced if the compression set rate exceeds a threshold value. Another estimation method is to estimate how long it will take for the compression set rate to reach the threshold value, assuming future loads and environmental factors, based on the thermal characteristics shown in Figure 5, if the compression set rate has not reached the threshold value. presume. The deterioration of the gasket 5 is the main factor that affects the life of the pole transformer 1. Therefore, by estimating the deterioration of the gasket 5, the life of the pole transformer 1 can be evaluated.

In the above-mentioned life evaluation method, the temperature of the gasket 5 was calculated, but an experimental example will be shown in which it is compared with the actually measured temperature of the gasket 5. FIG. 6 compares the temperature of the gasket 5 calculated without using environmental data such as solar radiation (calculated value; blue line) with the actually measured temperature of the gasket 5 (actual value; black line). Although the calculated values follow the actual measured values in terms of increase and decrease, there are discrepancies, especially in the temperature when it is sunny. For the colors of solid lines, dotted lines, etc. shown in Figures 6 to 10, please refer to the color drawings corresponding to Figures 6 to 10 submitted with the property submission form. Also, in Figures 6 to 8, there are some places where the actual measured value is zero, but this does not mean that the actual measured value of the gasket temperature is zero, but that the actual measured value is missing. It represents.

Figure 7 shows the temperature of gasket 5 calculated on a non-rainy day (calculated value; blue line) using heat flow due to solar radiation obtained from a meteorological observatory, taking into account the influence of wind, and the temperature of gasket 5 actually measured. This is a comparison of the temperature (actually measured value; black line). That is, the surface heat dissipation resistance R3' is used, and the rain coefficient α is 1. In this case, it has been shown that the calculated value approximates the actual measured value very well even on sunny days.

Table 1 shows the compression set rate for 10 years obtained from the gasket temperature calculated by taking into account the influence of wind speed. The actual wind speed is the wind speed obtained from a weather observatory or the like. 0.5 m/s, 1.0 m/s, and 4.0 m/s are not obtained from a meteorological observatory or the like, but are values appropriately assigned as wind speeds used for calculating gasket temperature.

The compression set rate obtained by considering the actual wind speed is considered to be the most reliable. On the other hand, the compression set rates when using wind speeds of 0.5 m/s, 1.0 m/s, and 4.0 m/s deviate from the compression set rates at actual wind speeds. I understand. In addition to using the wind speed obtained from a weather observatory as described above, the average wind speed for a predetermined period may be determined from the wind speed obtained from a meteorological observatory and the obtained average wind speed may be used.

Table 2 shows the compression set rate obtained from the gasket temperature calculated by setting the rain coefficient α to 1 and 0.4. Although the difference is not large, it can be said that the influence of rain affects the compression set rate.

In the example described above, heat flow due to solar radiation obtained from a weather observatory or the like was used, but FIG. 8 shows a comparison with the case where environmental data obtained at the installation location of the pole transformer 1 is used.

The figure shows the measured value (blue line), calculated value 1 (green), calculated value 2 (pink), and calculated value 3 (black) of the gasket temperature. The calculated value 1 is the gasket temperature calculated using the heat flow of solar radiation measured at the installation location of the pole transformer 1. Calculated value 2 is the gasket temperature calculated using the heat flow of solar radiation around the pole transformer 1 obtained from a weather observatory or the like. Calculated value 3 is the gasket temperature calculated without using the heat flow of solar radiation.

The calculated value 1 is closest to the actual value. The calculated value 2 is closer to the actual measurement value than the calculated value 3. Therefore, even when using environmental data regarding the amount of heat from solar radiation from a meteorological observatory, as in calculated value 2, it is possible to obtain a value closer to the actual value than when no environmental data is used, as in calculated value 3. Can be done.

Next, FIG. 9 shows a comparison between wind speeds obtained from a meteorological observatory and the like and those obtained at the location where the pole transformer 1 is installed.

The figure shows the measured value (green), calculated value 1 (blue), and calculated value 2 (black) of the gasket temperature. Calculated value 1 is a gasket temperature calculated using wind speed measured at the installation location of pole transformer 1. Calculated value 2 is the gasket temperature calculated using the wind speed around the pole transformer 1 obtained from a weather observatory or the like.

The calculated value 1 is closest to the actual value. The calculated value 2 is not as good as the calculated value 1, but is close to the actual measured value. Therefore, even when environmental data regarding wind speed from a weather observatory or the like is used as in calculation value 2, it is considered that a value closer to the actual measurement value can be obtained than a gasket temperature calculated without using environmental data.

Next, FIGS. 10 and 11 show the results of comparing the bushing temperature (gasket temperature) when wind speed and solar radiation were taken into account and when they were not taken into account, in order to study the influence on wind speed and solar radiation.

FIG. 10 shows the measured value (black), calculated value 1 (pink), calculated value 2 (blue), and calculated value 3 (green) of the gasket temperature. Calculated value 1 is the gasket temperature calculated taking into account solar radiation without considering wind speed. Calculated value 2 is the gasket temperature calculated taking into account the wind speed and not taking into account solar radiation. Calculated value 3 is the gasket temperature calculated without considering both wind speed and solar radiation. Calculated value 1 (wind speed not taken into account, solar radiation taken into account) resulted in a higher temperature and a longer time taken for the temperature to fall due to daily temperature fluctuations, compared to the actual measured value. Calculated value 2 (wind speed taken into account, solar radiation not taken into account) resulted in a lower temperature than the actual measured value. Calculated value 3 (both wind speed and solar radiation were not considered) resulted in deviations from the actual measured values in terms of temperature, time of daily temperature fluctuation, and time required for temperature drop.

As shown in FIG. 11, the calculated value taking into account wind speed and solar radiation has the smallest deviation from the actual measured value. From the results shown in FIGS. 10 and 11, it is necessary to consider wind speed and solar radiation in order to reduce the deviation between the measured temperature and the calculated temperature.

According to the above-described method for evaluating the life of a pole-mounted transformer, the gasket temperature is calculated based on environmental data obtained from a meteorological observatory, etc., and the gasket deterioration index (for example, compression set rate) is calculated based on this gasket temperature. It is possible to estimate and evaluate the life of the pole transformer 1 based on the deterioration index. In calculating the gasket temperature, environmental data around the pole transformer 1 is used. Thereby, the actual gasket temperature can be estimated with higher accuracy than when those effects are not considered. As a result, the deterioration index of the gasket can be estimated more reliably, and the life of the pole transformer 1 can be evaluated with higher accuracy.

As a specific method for evaluating the life of the pole transformer 1, the amount of increase in the deterioration index is determined from the calculated gasket temperature and the gasket thermal characteristics shown in FIG. 5(a), and the deterioration index shown in FIG. 5(b) is calculated. Calculate changes in metrics over time. The state of deterioration of the gasket 5 can be determined based on such a deterioration index and the threshold value, and the lifespan of the pole transformer 1 can be evaluated.

By switching and using a plurality of gasket thermal characteristics depending on the cumulative time, it is possible to more accurately obtain the amount of increase in the deterioration index, and as a result, it is possible to obtain the gasket deterioration index with higher accuracy.

Furthermore, the method for evaluating the life of a pole transformer can accurately calculate the gasket temperature using environmental data from a weather observatory, etc., without having to obtain environmental data at the location where the pole transformer 1 is installed. Moreover, since it is not necessary to arrange various devices for acquiring environmental data at the installation location of the pole transformer 1, the cost required for them can be eliminated.

In addition, the temperature, heat flow due to solar radiation, and wind speed are input as environmental data to the thermal equivalent circuit. Thereby, the gasket temperature can be calculated with higher accuracy.

Furthermore, the average wind speed is used as the wind speed given to the thermal equivalent circuit. This makes it possible to reduce the effects of momentary gusts of wind.

In addition, the rain coefficient is used in the thermal equivalent circuit. Thereby, the gasket temperature can be calculated with higher accuracy taking into account the influence of rain.

Further, in the above description, the case where environmental data is acquired from a weather observatory or the like has been described, but the present invention is not limited to such a configuration. The environmental data may be obtained by a sensor or the like provided near the installation location of the pole transformer 1 in a range including the pole transformer 1. Furthermore, if a smart meter having a sensor or the like capable of obtaining environmental data such as wind speed, temperature, and solar radiation is realized, environmental data may be obtained from such a smart meter.

Although a case has been described in which the smart meter 2 measures current at a frequency of once every 30 minutes, the present invention is not limited to such a frequency. The present invention can utilize a smart meter that can measure current at any frequency.

Although the compression set rate was used as the gasket deterioration index, the present invention is not limited to this. For example, the hardness of the gasket may be used. Since it is known that the hardness increases with thermal deterioration, an evaluation may be performed such as replacing it when the hardness exceeds a certain threshold. Furthermore, when using a deterioration index that decreases as the gasket deteriorates, FIG. 5 may be read as "decreased amount." Then, the deterioration of the gasket may be estimated based on the deterioration index and the threshold value in the same manner as when using the compression set rate.

It can be used in industrial fields where pole-mounted transformers are maintained.

1... Pole transformer, 2... Smart meter, 3... Lead wire, 4... Bushing, 5... Gasket, 6... Tank, 7... Electric wire, 8... Current measuring device, 10... Consumer, 11... Life evaluation device

Claims (9)

calculating said current from a smart meter capable of measuring the current passing through the pole transformer;
acquiring environmental data around the pole transformer;
Calculating the gasket temperature using the current and the environmental data as input data and using a thermal equivalent circuit for outputting the temperature of the gasket provided in the pole transformer (hereinafter referred to as gasket temperature),
estimating the lifespan of the pole-mounted transformer by estimating the deterioration index based on gasket thermal characteristics representing a relationship between the gasket temperature and an index representing the degree of deterioration of the gasket (hereinafter referred to as deterioration index); A method for evaluating the life of a pole-mounted transformer. A method for evaluating the life of a pole transformer according to claim 1, comprising:
The gasket thermal characteristics represent the relationship between the gasket temperature and the amount of increase or decrease in the deterioration index,
Each time the gasket temperature is calculated, the increase amount or the decrease amount corresponding to the gasket temperature is obtained from the gasket thermal characteristics, and the increase amount or the decrease amount is added to the deterioration index,
setting a threshold value indicating that the gasket needs to be replaced for the deterioration index;
A method for evaluating the life of a pole transformer, comprising estimating the life of the pole transformer based on the deterioration index and the threshold. A method for evaluating the life of a pole transformer according to claim 2, comprising:
Different gasket thermal characteristics are prepared for each cumulative time since the gasket was first used,
A method for evaluating the life of a pole-mounted transformer, characterized in that the amount of increase or the amount of decrease is obtained from the gasket thermal characteristics according to the cumulative time. A method for evaluating the life of a pole transformer according to any one of claims 1 to 3, comprising:
A method for evaluating the life of a pole transformer, wherein the environmental data is measured in an area including the pole transformer. A method for evaluating the life of a pole transformer according to any one of claims 1 to 4, comprising:
The thermal equivalent circuit is
The winding of the pole transformer, the oil temperature of the tank of the pole transformer, the gasket, and the air temperature are each connected in series with a thermal resistance in between,
A method for evaluating the life of a pole-mounted transformer, characterized in that the air temperature obtained as the environmental data is inputted as the air temperature. A method for evaluating the life of a pole transformer according to claim 5, comprising:
A method for evaluating the life of a pole transformer, characterized in that heat flow due to solar radiation is input as the environmental data to the gasket of the thermal equivalent circuit. A method for evaluating the life of a pole transformer according to claim 5 or 6, comprising:
A method for evaluating the life of a pole-mounted transformer, comprising: correcting the thermal resistance between the gasket of the thermal equivalent circuit and the air temperature so that it becomes smaller as the wind speed as the environmental data becomes stronger. A method for evaluating the life of a pole transformer according to claim 7, comprising:
A method for evaluating the life of a pole-mounted transformer, comprising: calculating an average wind speed for a predetermined period from the wind speed as the environmental data, and correcting the thermal resistance so that it becomes smaller as the average wind speed becomes stronger. A method for evaluating the life of a pole transformer according to any one of claims 5 to 8,
If the effect of rain is not considered, it is set as 1, and a value less than 1 is set as the rain coefficient depending on the degree to which the effect of rain is considered.
A method for evaluating the life of a pole transformer, comprising: multiplying the thermal resistance between the gasket of the thermal equivalent circuit and the air temperature by the rain coefficient.

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