JP4186630B2 - Isolation detection method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for detecting the amount of fouling on an insulator surface.
In particular, the present invention relates to a method for detecting an insulator fouling by calculating the amount of fouling of an insulator by using a leakage current value, temperature and humidity flowing on the insulator surface.
[0002]
[Prior art]
The insulator is installed in a power generation / transformation facility and supports a cable to which a high voltage is applied. When the power generation and substation equipment is in a salt damage area, salt is attached to the insulator surface and the insulator is contaminated. As the insulator fouls, partial discharge occurs on the insulator surface, leading to a ground fault. In order to prevent such an accident, the insulator fouling measurement method is used.
[0003]
As one of the conventional methods for measuring the insulator contamination, there is a method for calculating the insulator contamination amount by calculating means from the leakage current, temperature and humidity flowing on the insulator surface. When the calculated amount of fouling exceeds a predetermined value, the insulator is washed and the fouling material is washed away. Thereby, the occurrence of an accident in the insulator can be prevented.
In order to clean the insulator at an appropriate timing, it is necessary to accurately detect the amount of contamination of the insulator.
[0004]
The leakage current flowing on the insulator surface changes depending on the temperature and humidity even if the amount of fouling is constant. Therefore, in order to accurately measure the amount of contamination, the temperature and humidity are measured, and the leakage current value is converted into the amount of contamination based on these measured values. According to this method, the amount of contamination on the insulator surface can be accurately measured without being affected by the weather conditions around the insulator, and the timing of insulator cleaning can be accurately grasped (for example, see Patent Document 1).
[0005]
FIG. 1 shows the relationship between the amount of insulator contamination, temperature, and leakage current, and FIG. 2 shows the relationship between the amount of insulator contamination, humidity, and leakage current.
Each figure shows the relationship between temperature and leakage current and the relationship between humidity and leakage current with the amount of insulator fouling as a parameter. From the figure, it can be seen that even if the amount of contamination is constant, the leakage current changes when the temperature and humidity change. Further, when the amount of contamination changes, the relationship between temperature and leakage current and the relationship between humidity and leakage current change. Furthermore, when the amount of contamination is constant, it indicates that the relationship between temperature and leakage current and the relationship between humidity and leakage current are predetermined.
[0006]
In the conventional insulator contamination detection method, when the leakage current i0 is measured at the temperature T0, the leakage current value i18 at a temperature of 18 ° C. is corrected using the relationship shown in FIG.
If the humidity is H0, the leakage current i0 is corrected to the leakage current i80 having a humidity of 80% using the relationship shown in FIG. At this time, if the leakage current i18 corrected at a temperature of 18 ° C. is used as the leakage current i0, a reference leakage current corrected at a temperature of 18 ° C. and a humidity of 80% can be obtained.
[0007]
FIG. 3 shows the relationship between the reference leakage current and the amount of fouling. If the reference leakage current is obtained as described above, the amount of contamination of the insulator 1 can be obtained from the relationship shown in FIG.
[0008]
[Patent Document 1]
Japanese Patent Laid-Open No. 2001-231119
[Problems to be solved by the invention]
As described above, if the amount of insulator fouling is constant, the relationship between humidity and leakage current value should be constant. However, as a result of testing, it has been found that the relationship between humidity and the amount of eggplant contamination may not be constant.
FIG. 4 shows the relationship between ambient humidity and leakage current according to the test results. In this test, the applied voltage to the insulator was kept constant, and the relative humidity around the insulator and the leakage current (18 ° C equivalent leakage current value) flowing on the insulator surface were measured for several days.
[0010]
In this test, there was little change in the amount of insulator fouling after several days of measurement. Further, since the applied voltage is constant, there is no change in leakage current due to voltage fluctuation. However, actually, as shown in FIG. 4, when the relative humidity changes, the leakage current does not change in a fixed relationship. Therefore, high detection accuracy cannot be obtained only by obtaining the amount of contamination from the measured relative humidity and leakage current.
[0011]
It has been found that the error shown in FIG. 4 is caused by using the ambient humidity as the humidity when the leakage current value is converted into the amount of insulator fouling.
The temperature and humidity of the insulator surface change with a time lag with respect to changes in ambient temperature and humidity. For this reason, when the ambient temperature and the ambient humidity change, a difference occurs between the temperature and humidity of the local space surrounding the fouling substance attached to the insulator surface and the ambient temperature and ambient humidity.
[0012]
The leakage current that flows on the insulator surface is determined by the temperature and humidity of the insulator surface. Therefore, if the ambient temperature and ambient humidity are used as they are for the conversion processing of the fouling amount, an error due to a time delay occurs.
An object of the present invention is to make it possible to accurately detect the amount of insulator contamination even in the case where there is a change in the ambient environment in the insulator contamination detection method for obtaining the amount of contamination on the insulator surface from the leakage current value, temperature and humidity Is.
[0013]
[Means for Solving the Problems]
The present invention has been made to achieve the above object. In the present invention, the leakage current value and temperature flowing on the insulator surface are measured to determine the humidity of the insulator surface. Then, the amount of fouling on the insulator surface is determined by calculation from these leakage current, temperature and humidity.
According to the present invention, since the amount of insulator contamination is calculated by directly using the humidity on the insulator surface, the insulator contamination amount can be accurately detected even if there is a difference between the insulator surface humidity and the ambient humidity.
[0014]
The humidity of the insulator surface can be obtained by measuring the ambient humidity and calculating a delay with a predetermined time constant.
Further, the amount of contamination can be detected more accurately by using a value specific to the detected insulator as the predetermined time constant.
[0015]
As for the temperature, a time delay occurs between the insulator surface temperature and the ambient temperature. However, the influence of this is less than the influence of the time delay of humidity, and can be ignored. However, the detection accuracy can be further improved by taking into account the time delay of the temperature.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings.
FIG. 5 shows the configuration of an apparatus that implements the insulator stain detection method.
The insulator 1 is attached to the electric power device 15 and supports the cable 16. A leakage current sensor 2 is connected to the attachment base of the insulator 1. The leakage current sensor 2 measures the leakage current i flowing on the insulator 1 surface.
[0017]
A temperature sensor 3 for measuring the ambient temperature of the insulator 1 and a humidity sensor 4 for measuring the ambient humidity are provided.
Output signals of the leakage current sensor 2, the temperature sensor 3, and the humidity sensor 4 are input to the insulator stain detection device 5.
[0018]
In the insulator contamination detection device 5, each input signal is converted into a digital signal by the A / D converter 6 and input to the CPU 7.
In the CPU 7, each digital signal is delayed in time by the digital filter 8 and input to the calculation means 9.
Part or all of the digital filter 8 can be omitted. Details of the digital filter 8 are described in Japanese Patent Application No. 2002-255562.
[0019]
The calculation means 9 calculates the amount of fouling on the insulator 1 surface using the measured leakage current, ambient temperature, and ambient humidity.
The amount of contamination calculated by the calculation means 9 is output to the output unit 10. The output unit 10 can be configured by a display, a printer, or the like. Also, a relay contact for issuing an alarm to the outside when the amount of contamination exceeds a threshold value may be used.
[0020]
A method for calculating the amount of fouling by the calculating means 9 will be described.
The calculation of the fouling amount is executed at predetermined time intervals.
First, the measured leakage current value is corrected to the leakage current value at a temperature of 18 ° C. using the relationship shown in FIG. 1 according to the measured ambient temperature.
[0021]
Next, the corrected leakage current value is converted into the amount of insulator fouling by using the relationship shown in FIG.
The method for calculating the amount of insulator contamination is not limited to the above example, and any other method can be used.
[0022]
The feature of this example is that the humidity (calculated humidity) obtained by the following calculation is used as the humidity, not the measured ambient humidity (relative humidity).
The calculated humidity Hs (n) is obtained by the following equation.
Hs (n) = Hs (n−1) + ΔH × (1−e ^{(−1 / t)} )
[0023]
Here, Hs (n-1) is the calculated humidity obtained by the calculation at the previous time (n-1 o'clock). ΔH is a difference (H (n) −Hs (n−1)) between the humidity H (n) obtained by the current measurement (n hours) and the calculated humidity Hs (n−1) obtained by the previous calculation. is there. t is an intrinsic time constant, which is a value determined by the type and shape of the insulator 1 and the time interval for performing the above calculation, and can be obtained for each insulator 1 by experiments and calculations.
[0024]
The reason why the calculated humidity Hs (n) is used will be described with reference to FIG.
Since the insulator 1 has a heat capacity, the surface temperature of the insulator 1 is a time delayed from the ambient temperature. For this reason, when a change occurs in the ambient temperature, a difference occurs between the temperature T1 of the local space 11 on the insulator surface and the temperature T2 of the ambient space 12 at the same time.
Here, assuming that the water vapor pressure in the local space 11 and the surrounding space 12 on the insulator surface is constant, the relative humidity H1 in the local space 11 and the relative humidity H2 in the surrounding space 12 are different.
[0025]
Further, when the fouling of the insulator 1 proceeds, a fouling substance 13 such as sodium chloride or magnesium chloride adheres to the insulator surface. A time delay also occurs between the relative humidity H1 of the local space 11 and the relative humidity H2 of the surrounding space 12 when the pollutant 13 absorbs and drains moisture in the space.
By calculating the calculated humidity Hs (n) from the above equation, the time delay factor of each relative humidity can be taken into account, and the current relative humidity of the insulator surface can be obtained.
[0026]
The meaning of the above formula is as follows.
The difference between the calculated humidity obtained in the previous calculation and the ambient humidity measured this time is added to the previous calculated humidity with a time delay due to the intrinsic time constant t, so that the calculated humidity can be obtained. Since the intrinsic time constant t is determined by the type and shape of the insulator 1 and the time interval for performing the above calculation, the calculated humidity of this time accurately indicates the humidity on the surface of the insulator 1.
[0027]
When the calculation means 9 calculates the calculated humidity Hs (n), it stores it in the memory. Thus, it can be used as the previous calculated humidity Hs (n−1) at the next calculation. Moreover, the calculation means 9 calculates the above-described leakage current using the current calculated humidity Hs (n).
[0028]
FIG. 7 shows the test results when the above calculated humidity is used. Leakage current, ambient temperature, and ambient humidity were determined under the same conditions as in the test of FIG. As a result, when the calculated humidity was obtained and the relationship with the leakage current was obtained, a substantially constant relationship was obtained between them as shown in FIG. This relationship is in good agreement with the theoretical relationship.
Thus, the amount of contamination on the insulator surface can be accurately detected by using the calculated humidity.
[0029]
In the above example, the humidity of the insulator surface is obtained by calculation. However, when the humidity of the insulator surface can be directly measured, the directly measured insulator surface humidity can be used.
In the above example, only the humidity time delay is corrected, but the detection accuracy can be further improved by correcting the temperature with respect to the time delay.
[0030]
【The invention's effect】
According to the insulator contamination detection method of the present invention, when the amount of insulator surface contamination is determined from the leakage current value, temperature and humidity, the insulator surface humidity is used as the humidity. Therefore, the insulator contamination amount can be accurately detected. .
[Brief description of the drawings]
FIG. 1 is a diagram showing a relationship among an amount of insulator contamination, temperature, and leakage current in an insulator contamination detection method.
FIG. 2 is a diagram showing a relationship among an amount of insulator contamination, humidity, and leakage current in an insulator contamination detection method.
FIG. 3 is a diagram showing a relationship between a reference leakage current and a contamination amount in the insulator contamination detection method.
FIG. 4 is a diagram showing an experimental result by a conventional insulator stain detection method.
FIG. 5 is a diagram showing a circuit configuration of an apparatus for carrying out the insulator stain detection method of the present invention.
FIG. 6 is a diagram for explaining the reason why there is a difference between the relative humidity on the insulator surface and the ambient humidity.
7 is a diagram showing the relationship between humidity and leakage current by the apparatus of FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... insulator 2 ... leakage current sensor 3 ... temperature sensor 4 ... humidity sensor 5 ... insulator contamination detector 6 ... A / D converter 7 ... CPU
DESCRIPTION OF SYMBOLS 8 ... Digital filter 9 ... Calculation means 10 ... Output part 11 ... Insulator surface local space 12 ... Ambient air layer 13 ... Fouling substance 15 ... Electric power equipment 16 ... Cable

Claims (2)

Measuring leakage current value and temperature flowing on the insulator surface;
Measuring the ambient humidity of the insulator surface, the steps we calculate the calculated humidity delayed this with a predetermined time constant,
Calculating the amount of fouling on the insulator surface from the leakage current, the temperature, and the calculated humidity;
An insulator defacement detection method comprising:   The method of claim 1, wherein the time constant is a value unique to the insulator.

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