JP2000338153A - Method for processing insulating resistance measured value under hot line of power cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the processing of a measured value out of a true value caused by the mixing of noise voltage and the like, into a value near an insulating resistance true value by determining a representative insulating resistance value from a group of insulating resistance measured values consisting of only positive polarity. SOLUTION: The measurement of insulating resistance is executed to a cable to be measured at time intervals to obtain a group of insulating resistance measured values [RI]. The remeasurement is executed for the insulating resistance measurement from which the insulating resistance measured value of negative polarity was obtained among a group of insulating resistance measured values, and the data of the value of negative polarity is rejected when the insulating resistance measured value of negative polarity is obtained inspite of the remeasurement. A representative insulating resistance value representing a group of insulating resistance measured values is determined from a group of insulating resistance measured values consisting of only positive polarity. Whereby the power cable insulating resistance under hot line can be indicated by a value sufficiently near a true value under the adverse measuring environment that the insulating resistance of an anticorrosion layer is low and the intrusion noise voltage is high, and this can be applied to the monitoring of the insulation under hot line of the high tension power cable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for diagnosing insulation deterioration of a power cable used in a high-voltage or extra-high-voltage field and applying a low DC signal voltage under a live line to measure the insulation resistance of the power cable. It relates to a method of obtaining an insulation resistance measurement value close to the value.

[0002]

2. Description of the Related Art As a practical method for measuring the insulation resistance of a power cable under a live line, a DC low signal voltage is superimposed on an AC working voltage, and a DC current flowing between a shielded end of a target cable and the ground is applied. 2. Description of the Related Art There is known a technique of calculating an insulation resistance by measuring a leakage current. It is also known in the art that large measurement errors are sometimes introduced during insulation resistance measurement. The causes are summarized in the following two.

(A) The insulation resistance of the anticorrosion layer of the cable to be measured is low. (B) Undefined noise voltage E _n from entering the measurement system. The reason for this will be explained (for details, see Literature, Denki Kagaku B, Vol. 116, No. 9, 1996, pages 1074 to 1082). Although anti-corrosion layer insulation resistance R _s are generally bad with 1MΩ or less, 1 cable with polyethylene anticorrosion layer
Even if it is 0 MΩ or less, it is already defective, and it may be considered that the anticorrosion layer has a pinhole or a locally deteriorated portion. In such a case the that point, local voltage E _s between shielding copper tape and earth occurs. This local voltage E _s is generally at 1V or less, if the value is stable, the live wire under the insulation resistance measuring device or cancel the voltage to create the actively oppose voltage or computing By canceling out the influence, it is possible to prevent a measurement error from occurring. However, if the local voltage E _s is a complete cancellation is not possible to indicate the unstable appearance is than it causes measurement errors come to penetrate the measuring circuit residue variation E _n is as noise voltage . Source of noise voltage E _n is also present in other beyond only the local voltage Es, effect on the measurement error in any case is greater the smaller anticorrosion layer insulation resistance R _s. More precisely, the ratio K = R _I / R _s with respect to R _s of the insulating layers insulation resistance R _I is a primary measured, the product of the noise voltage E _n, the measurement error larger the KE _n increases. This is represented by the following equation.

Β = [R _I ] / R _I = E / (E + KE _n ) where R _I : insulation resistance true value [R _I ]: insulation resistance value including error K: R _I / R _s R _s: anticorrosion layer insulation resistance E: DC signal voltage and generally try Tomeyo a 50 V beta to about 90%, of KE _n is E 10
%. That is, 5V or less is desirable. The larger the insulation resistance true value R _I is as anticorrosion layer insulation resistance R _s is small, the noise voltage E _n is about achieving this condition is difficult larger.

[0005]

[Table 1]

Table 1 and FIG. 1 show that R _I = 100,000 M
Ω, 10,000MΩ, every three cases 1,000Emuomega, calculating the relationship between the measured insulation resistance value of the noise voltage E _n as a parameter and [R _I] and the anticorrosion layer insulation resistance R _s, is a depiction. In Table 1, the virtual noise voltage E _n! = ER _s /
The value of [R _I ] is also shown. Noise voltage E _n is predominantly positive polarity in FIG. 1, hence β but indicates the smaller than 1, the noise voltage E _n is not limited only to the positive polarity, in some cases appearing in negative polarity. In this case beta may be greater than one digit, the KE _n increases further the minus direction from minus 50 V beta is starts to negative polarity by ∽ pass. That is, the measured insulation resistance [R
_I] is not limited to be smaller than the insulation resistance true value R _I, if also be measured erroneously greater than the insulation resistance true value R _I, it is calculated as the measured insulation resistance of the negative polarity [R _I] Some In some cases. Although not character like noise voltage E _n itself is normally distributed around a 0, the probability that the probability and negative polarity as a positive polarity may be considered are equal. However, the probability that the measured insulation resistance value [R _I ] becomes a positive polarity and the probability that the measured insulation resistance value becomes a negative polarity are clearly higher in the former as can be understood from the above description. When a measured insulation resistance value [R _I ] of negative polarity is obtained as a result of actual measurement, how to handle it is a problem. This problem has been dealt with in the prior art as follows. (B) When the measured insulation resistance [R _I ] of the negative polarity is obtained, it is considered that the measurement was performed as the measured insulation resistance [R _I ] ≒ ∞. It is assumed that the maximum readable insulation resistance [R _I ] of the maximum readable insulation resistance determined by the resolution of the measuring device, for example, 200,000 MΩ, is measured. (B) A geometric mean value of a group of measured insulation resistance values [R _I ] of only a group of positive polarities including such a critical high insulation resistance value is obtained, and is used as a representative insulation resistance of the group. (C) A group of measurements usually consists of data measured once a day within a period of about 10 days, such as the early, middle, and late quarters of a month. That is, after data for the number of days in the season is accumulated, these geometric average values are obtained and set as representative insulation resistance values of the group.

[0007]

With the above-described method of processing the measured insulation resistance, no particular problem occurs.
The purpose of monitoring under-line insulation of most high-voltage cables has been well fulfilled. However, when the operating voltage range of the cable to be measured extends to an extra high voltage range, the value of the insulation resistance to be measured also extends to a high range. The following table shows the insulation resistance threshold values used by the inventor to distinguish good and bad crosslinked polyethylene insulated power cables in various voltage ranges.

Insulation resistance threshold value for distinguishing good and bad power cable insulation characteristics Nominal working voltage threshold value (high voltage range) 3KV 1,000MΩ 6KV 3,000MΩ (special high voltage range) 10KV 10,000MΩ 20KV 30,000MΩ As shown in (1), since the insulation resistance to be measured has an order of magnitude difference between the high voltage range cable and the special high voltage range cable, the following problems have occurred. When the DC signal voltage E is maintained at 50 V and the high insulation resistance near the threshold is monitored under the same measurement environment as before, that is, under the same noise voltage generation and equivalent corrosion protection layer insulation resistance, the K value becomes 1 Since the number of digits increases, the measurement error increases significantly. In reality, when the corrosion resistance of the anticorrosion layer is reduced to 1 MΩ or less in the summer measurement, the insulation resistance of the cable, which has shown a value of 10,000 MΩ or less in the winter measurement, is often 1,000 MΩ or less. And it cannot be distinguished whether the insulation performance is truly lowered or just an error measurement result, resulting in doubt. In some cases, some cases appeared to show a higher insulation resistance value than was actually the case. Simulation of the above situation
The results clarified by (simulation) are shown below.

Conditions of Simulation Target Cable: 10 KV CV Cable Insulation Resistance Degradation Characteristics: Insulation Resistance of Origin: 100,000 MΩ Degradation Condition One 100,000 MΩ fault is newly added every season (10 days).

[0010] During this period, a logarithmic sine change is set as a standard, and a double or half amplitude change is superimposed thereon.

Noise voltage: +10 mV, +3 mV, +1 mV, +0.3 mV 0: −0.3 mV, −1 mV, −3 mV, −10 mV Nine kinds of noise voltages are taken in at random without weighting.

Period: Beginning in the first winter of the first year and ending in the third autumn of the third year, for a total of three years, for a total of ten
August Simulation result Insulation resistance R near the threshold of 10,000 MΩ as a representative
Daily measurement environment and the measurement insulation resistance value measured over the first year Winter ninth season _{that I} value is decreased across the second season Spring [R
_I ] is shown in Table 2 and FIG.

[0013]

[Table 2]

When the measured insulation resistance value [R _I ] is obtained as a negative value, it is shown in FIG. 2 on the assumption that [R _I ] = 200,000 MΩ. However, as shown in Table 2, even if the daily measurement is not negative, a negative noise voltage actually penetrates, and a value higher than the true value is often taken as a positive effective measurement value. You can see that. Even if the average insulation resistance (indicated by the double circles in FIG. 2) calculated including the false high insulation resistance values is relatively close to the true insulation resistance value, It is only a coincidence. FIG. 3 shows the change of each seasonal average insulation resistance value during the entire simulation period together with a change curve of the true insulation resistance value. In this simulation example, it is found that the measured insulation resistance value [R _I ] is often higher than the true value. The positive error increases in summer when the corrosion resistance of the anticorrosion layer decreases. Of course, this situation is
In the case of the limitation of the case of the present invention, the influence of the negative noise voltage on the measured value of the intrusion result is not limited by the prior art. Obviously, it is unreasonable, too much left to chance, and irrational. The present invention provides a new method of measuring insulation resistance under a live line of a power cable, which can process a measured insulation resistance value that has been deviated from a true insulation resistance value due to a mixed noise voltage or the like to a value close to the true insulation resistance value. Is to provide a simple processing method.

[0015]

SUMMARY OF THE INVENTION According to the present invention, there is provided a method for processing a measured value of insulation resistance under a live line of a power cable, wherein the insulation resistance measurement is performed on the cable to be measured with a time interval. Obtaining a group of insulation resistance measurement values, performing a re-measurement on the insulation resistance measurement having obtained a negative polarity insulation resistance measurement value of the group of insulation resistance measurement values, When obtaining the insulation resistance measurement value, the data is discarded, and a representative insulation resistance value representing the one group of insulation resistance measurement values is obtained from the group of insulation resistance measurement values consisting of only the positive polarity for the cable to be measured. Determining. further,
The step of determining the representative insulation resistance value includes calculating a virtual noise voltage for each insulation resistance measurement value, obtaining a relation curve between the virtual noise voltage and the insulation resistance measurement value by the least square method, and determining the curve. Comparing the calibration insulation resistance value corresponding to each virtual noise voltage with the measured insulation resistance value, and using the smaller value as a virtual representative insulation resistance value at that virtual noise voltage; Calibrating the virtual noise voltage to a value below the average corrosion protection layer insulation resistance related to the resistance measurement and rejecting the virtual representative insulation resistance value corresponding to a calibrated virtual noise voltage below a predetermined limit determined for the group. And determining a maximum value of the remaining virtual representative insulation resistance values as a representative insulation resistance measurement value representing the group of insulation resistance measurement values.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS It is unreasonable in the prior art that, when a negative measured insulation resistance value [R _I ] is obtained, the measured insulation resistance value is added to a positive limit high insulation resistance value, for example, 200,000 M.
Ω, which is used for calculating the average value. This has the effect of making the average value closer to the true value in proportion to other data measured very low below the true value due to the intrusion of the positive noise voltage, but the degree of the result, that is, overshoot or lack It depends entirely on chance, and you can't predict what the result will be. Therefore, as a first step for eliminating this irrationality and approaching the true value, a means called re-measurement is adopted. That is, the cable where the negative measured insulation resistance value [R _I ] is measured is marked,
After the round of measurement of the cable group is completed, the return measurement is repeated for the cable. It is expected that the measurement insulation resistance value [R _I ] of the positive polarity is obtained by the re-measurement. Although there is still a probability that the measured insulation resistance value [R _I ] of the negative polarity can be obtained even in the second measurement, Simulat
In the ion results, the probability of turning positive was higher.
Nevertheless, there are two ideas for what to do if the negative measured insulation resistance [R _I ] is obtained again. One is to try the third measurement. Another is to reject the measurement data of the cable. In the former case, the feasibility is determined by the number of cables to be measured and the remaining measurement allowance time.
The latter is a practical solution. If the result of measurement again shows a negative polarity result, the series of data is rejected. Simulatio processed as described above
The results are shown in FIG. As expected, the re-averaged value of only the measured insulation resistance [R _I ] of the positive polarity is lower than in the case of FIG. But all plotted points rather than positioned lower than the true value change curve R _I, cases still re average value of the measured insulation resistance value [R _I] are shown above the insulation resistance true value R ₁ number We know that it exists. Ironically, due to such a situation, FIG. 4 seems to show a change curve closer to the true value deterioration characteristic than FIG. As is also shown in the analysis already carried out, measured insulation resistance value [R _I] is the noise voltage E _n of the obtained even though actually negative polarity positive polarity has penetrated the insulation resistance true value R _I This is because the higher measured insulation resistance value [R _I ] could not be excluded because it was indicated with a positive polarity, and was included in the average value calculation. Therefore, simply, the integration of the measured insulation resistance values [R _I ] having only the positive polarity is obtained as a group, and the highest measured insulation resistance value [R _I ] among them is taken as the representative insulation resistance of the group. Such an idea does not hold. The next task is how to find and eliminate the measured insulation resistance value [R _I ] that is higher than the true insulation resistance value R _I. The above-mentioned remeasurement was performed by hardware, but the next method is a processing method by software, and the necessary basic data is already available.
This is processed as follows. (1) virtual noise voltage E _n! Is the measured insulation resistance value [R _I ]
Ask every time. The calculation formula is as follows.

[0017] E _n! = ER _s / [R _I] virtual noise voltage E _n! Not its intrusion noise voltage E _n. Although noise voltage E _n can be determined by calculating the insulation resistance true value R ₁ from the measured insulation resistance value [R _I] If it turns out, because the noise voltage E _n is it is impossible to determine even if the how, virtual noise voltage E _n as a numerical value that can be handled in reality as an alternative to this! And try to use this in the next step. Noise voltage E _n and the virtual noise voltage E _n! Has the following relationship: (Induction omitted) E _n = E _n! (R _I - [R _I]) / R If _I thus measured the insulation resistance value [R _I] is as measured extremely small as compared with the insulation resistance true value R _I is virtual noise voltage E _n
! Very close to the noise voltage E _n it is. Or measured when the insulation resistance value [R _I] is very close measured insulation resistance true value R _1, the virtual noise voltage E _n! Even though it is calculated by the modest value, the noise voltage E _n is close to zero. Returning now to Table 1 noise voltage E _n and the virtual noise voltage E _n! Examining the real relationship with, under certain anticorrosion layer insulation resistance, any two measured insulation resistance value [R _I] In the virtual noise voltage E _n! Differential voltage between the equal to the difference voltage between the noise voltage E _n. Therefore, when one of the measured insulation resistance values [R _I ] is equal to or close to the true insulation resistance value R _I , the noise voltage En that led to the other measured insulation resistance value [R ₁ ] is _equal to the two. virtual noise voltage E _n! It can be seen that the difference voltage is equal or approximate. Virtual noise voltage E _n and the noise voltage E _n as described above! From the relationship between the virtual noise voltage E _n! Appears to likely be able to infer the real noise voltage E _n by obtaining, there is Simulation So seen that, measured insulation resistance value is actually [R _I]
It is not easy to determine the relationship between the value and the true value of the insulation resistance R ₁ . Therefore, the virtual noise voltage E _n! And is kept only to be kept aware of the qualitative relationship between the noise voltage E _n, virtual noise voltage E _n as the only indicator voltage at the time to promote an alternative after handling the noise voltage E _n! Is used. (2) the virtual noise voltage E _n! A relation curve of the measured insulation resistance [R _I ] is created. All of the following steps aim to eliminate insulation resistance measurements [R _I ] that are higher than the true insulation resistance value R _I. First virtual noise voltage E _n! And the measured insulation resistance value [R _I ] is determined by the least squares method. Each virtual noise voltage E _n! And the virtual noise voltage E _n measured insulation resistance value [R _I] asked all their natural logarithms corresponding to it! And the average value of the measured insulation resistance values [R _I ] are obtained, and a curve which passes through these average values and which is usually a straight line to the right on a log-logarithmic grid is drawn. Measure insulation resistance [R
_I ] itself is scattered above and below the curve when plotted. This curve shows the geometric mean corrosion protection layer insulation resistance (R _s
Average) in the lower, the virtual noise voltage E _n! And the measured insulation resistance [R _I ]. (3) The measured insulation resistance value [R _I ] plotted above the relationship curve is rejected because it is highly suspected of including an error. Virtual noise voltage E _n! Insulation resistance against measurement [R _I ]
Measured insulation resistance values are plotted above the relational curve [R _I] is suspected noise voltage E _n is a product of the result of entering a minus value is concentrated. The downward slope as a whole is the result of the strong influence of the decrease in the corrosion protection layer insulation resistance R _s . The plot point above the curve indicates that the corrosion protection layer insulation resistance R _s is higher than the average value. Although also a case caused, high measurement insulation resistance value than the insulation resistance true value R _I caused by invasion of the negative noise voltage E _n is now [R _I]
Therefore, all the measured insulation resistance values [R ₁ ] above the suspected curve are rejected. The virtual noise voltage E _n instead rejected measurements insulation resistance value [R _I]! The calibration measurement insulation resistance value [R _I ] on the relationship curve corresponding to the above is used as a representative. Next, all measured insulation resistance values [R _I ] below the relationship curve are valid as representatives. Putting the above in different words,
The same virtual noise voltage E _n! Virtual noise voltage E _n on the axis! Vs. measured insulation resistance value [R _I] calibration measurements insulation resistance value determined on the relational curve between [R _I], compares the magnitude relation between the original insulation resistance true value R _I, its virtual noise voltage with a smaller value Is the representative insulation resistance value. For subsequent handling, the remaining measured insulation resistance [R _I ] may be rearranged from a large value to a small value. It is still too early to use the measured insulation resistance value [R _I ] showing the largest value as the representative insulation resistance of the group (season). False fairly high insulation resistance (higher R _I [R _I]) is because it will have still remained. (4) A calibration virtual noise voltage threshold is set for each group, and a test for rejection of the measured insulation resistance value [R _I ] is performed.

[0018] The geometric mean anti-corrosion layer insulation resistance R _s mean value of groups obtained by the following equation. (The same also obtained from separate each R _s) R _s mean = (E _n! Average × [R _I] mean) / E calibrated virtual noise voltage E _n! Each measured insulation resistance value [R _I] and the virtual noise voltage E _n corresponding to it! The following equation is used for each calculation.

[0019] The calibration virtual noise voltage E _n! = E _n ! / A (R _s average / R _s) where R _s is measured anticorrosion layer insulation resistance R _s when measuring the measured insulation resistance value [R _I]. Calibration virtual noise voltage E _n!
Is given by the following equation, and the virtual noise voltage En _n ! It is compared with the threshold value, calibration virtual noise voltage E _n! Is smaller than the threshold value, the corresponding measured insulation resistance value [R _I ] is rejected.

[0020] E _n! Threshold = E _n! Average value / log [R _I ] average value The log [R _I ] average value which is the denominator of this formula is Simula
This is a purely empirical formula obtained from the Tion and has no physical meaning. By simulation, the insulation resistance true value R _I
A suitable denominator for finding a higher measured insulation resistance [R _I ] is 10 to 2, and a fixed number is not acceptable due to poor results. The larger the measured insulation resistance [R _I ], the larger the value. It has been found that a value is preferred. log
The [R _I ] average has been adopted as the function that most easily responds to this requirement, and may be or may be modified from experience in practical use. The highest value of the remaining measured insulation resistance values [R _I ] is determined as the insulation resistance treatment value representative of the group (season).

Examples Tables 3 to 5 show that R _I = 100,000 MΩ, 10,000
A specific example of a simulation for determining an insulation resistance processing value performed near 0 MΩ or 1,000 MΩ will be described.

[0022]

[Table 3]

[0023]

[Table 4]

[0024]

[Table 5]

[0025] FIGS. 5 to 7 virtual noise voltage E _n corresponding to Tables 3 to 5! The relationship between the measured insulation resistance [R _I ] is shown. The measured insulation resistance value [R _I ] indicated by a double circle in the figure is the insulation resistance treatment value representative of the group determined by applying the present method.

FIG. 8 is a change curve of the measured insulation resistance value [R _I ] processing value showing the result of the whole simulation. This shows the result of applying the processing method according to the present invention based on exactly the same measurement results as in FIG. 4, which already consisted of only the positive polarity [R _I ] value. The phenomenon of large measurement errors in summer has disappeared.

Compared with FIG. 4, it is clear from the change curve of the true value of the insulation resistance that the measured insulation resistance value [R _I ] is extremely small. On the contrary, you can see that it often exceeds. This Tables 3 5 Any noise voltage E _n is negative polarity as seen 0.3 mV, lm
This means that the measured insulation resistance value [R _I ] higher than the insulation resistance true value R _I appearing at V may not be completely excluded. However, it is also clear that the overall improvement has been greatly improved when compared to FIG. Tables 3 to 5 also show, as an example, that when a large negative polarity noise voltage has penetrated and the measured insulation resistance value [R _I ] of the positive polarity has been shown, it is accurately excluded.

The virtual noise voltage E _n high measurement insulation resistance value than the insulation resistance true value R ₁ which is shown in this Simulation example [R _I] Note as trying to eliminate sharp! When exploring large That threshold to reduce the expression of the denominator for determining the threshold value, be [R _I] processed value with high insulation resistance true value R _I region becomes lower than the insulation resistance true value R _I It is known separately. Since it is desired to obtain the measured insulation resistance value [R _I ] as close as possible to the true insulation resistance value R _I in the region of R _I of 3,000 MΩ or more, the processing results in this region may be emphasized. In this sense, the present Simulation can be said to show quite good results. 3,000M
In the region of the true value of the insulation resistance R _I of less than Ω, the fact that the insulation failure has already been determined by the integration of the measurement results up to that point, the measurement error does not need to be a problem.
Although Simulation showed an example in which the insulation resistance change was tracked in a time series over a long period of time, the present invention captures a single cable to be measured and repeats the measurement once, for example, every 15 minutes, which is extremely impractical. It can also be applied to obtain an approximate value of the true insulation resistance of the cable in a stable noise voltage intrusion environment.

[0029]

According to the present invention, unlike the non-scientific data processing method which has hitherto relied on chance, a rational and Sim
As a result of improvement in hardware and software backed by the ulation, the power cable insulation resistance under the live band in the higher range than before has been improved in a bad measurement environment where the insulation resistance of the anticorrosion layer is low and the intrusion noise voltage is high. Since it can be indicated by a value sufficiently close to the true value, it is optimally applied to monitoring under insulation of a high voltage power cable as well as monitoring of insulation under a hot line of a special high voltage power cable.

[Brief description of the drawings]

[1] Measurement insulation resistance noise voltage E _n as a parameter [R _I] is a diagram showing the relationship between the insulation resistance true value R _I, anticorrosion layer insulation resistance R _s.

FIG. 2 is a diagram showing a relationship between a measurement period and a measured insulation resistance value [R _I ].

FIG. 3 is a diagram showing a change in an insulation resistance value measured in each season during the entire simulation period, together with a change curve of a true insulation resistance value.

FIG. 4 is a diagram showing a change in each season's average measured insulation resistance value during the entire simulation period after discarding a measured insulation resistance value of negative polarity as a result of re-measurement, together with a change curve of a true insulation resistance value.

[Figure 5] In response to Table 3 virtual noise voltage E _n! It is a figure showing the change curve of insulation resistance value [ _RI ] with respect to measurement.

[6] In response to the Table 4 virtual noise voltage E _n! It is a figure showing the change curve of insulation resistance value [ _RI ] with respect to measurement.

[7] In response to the Table 5 virtual noise voltage E _n! It is a figure showing the change curve of insulation resistance value [ _RI ] with respect to measurement.

FIG. 8 is a diagram showing a processing value of a measured insulation resistance value [R _I ] in a whole simulation period together with a change curve of a true insulation resistance value.

Claims (2)

[Claims] 1. A live line, wherein a DC low signal voltage is applied superimposed on an AC working voltage, and a DC leakage current flowing between a shielded end of a cable to be measured and the ground is measured to obtain a measured insulation resistance value. In a method for measuring the insulation resistance of a power cable below, performing an insulation resistance measurement on the cable to be measured over a time interval to obtain a group of insulation resistance measurements for the cable to be measured; and In the step of performing a re-measurement on the insulation resistance measurement having obtained the negative polarity insulation resistance measurement value among the insulation resistance measurement values, and when obtaining the negative polarity insulation resistance measurement value regardless of the re-measurement, the data is Rejecting and determining a representative insulation resistance value representative of the group of insulation resistance measurement values from the group of insulation resistance measurement values consisting of only the positive polarity with respect to the cable to be measured. Comprising a floor, a processing method of hot-under insulation resistance measurement of the power cable. 2. The step of determining the representative insulation resistance value includes the steps of calculating a virtual noise voltage for each insulation resistance measurement value, and obtaining a relationship curve between the virtual noise voltage and the insulation resistance measurement value by a least square method. Compare the calibration insulation resistance values corresponding to the respective virtual noise voltages determined by the curves, and the magnitude relationship between the measured insulation resistance values, and use the smaller value as the virtual representative insulation resistance value at that virtual noise voltage. Calibrating the virtual noise voltage to a value according to the average corrosion protection layer insulation resistance related to the group of insulation resistance measurements and the virtual noise voltage corresponding to a calibrated virtual noise voltage below a predetermined limit determined for the group. Rejecting a representative insulation resistance value; and determining a maximum value of the remaining virtual representative insulation resistance values as a representative insulation resistance measurement value representing the group of insulation resistance measurement values. The method according to claim 1