JP6832728B2 - A method for estimating the production status of organic copper compounds and copper sulfide in oil-containing cables by insulating oil analysis, and a method for diagnosing the risk of abnormal occurrence of oil-containing cables. - Google Patents

Description

The present invention relates to a method for estimating the production status of an organic copper compound and copper sulfide in an oil-containing cable by insulating oil analysis, and a method for diagnosing the risk of abnormal occurrence of the oil-containing cable.

In oil-containing electrical equipment such as oil-containing transformers, conductive copper sulfide is generated (sulfide corrosion) by the reaction between the copper parts of the oil-containing electrical equipment and the sulfur component in the insulating oil, and oil is contained in order to cause dielectric breakdown. It is known that it can cause fatal damage to electrical equipment. The estimated sulfur components in the insulating oil include the sulfur component contained in the insulating oil, the eluted sulfur component eluted from the members such as insulating paper, and the added sulfur component such as the antioxidant added to the insulating oil. Conceivable.

Oil-filled electrical equipment such as large transformers use oil-impregnated paper as an insulator, so if copper sulfide adheres to this oil-impregnated insulating paper, a short circuit will occur between the coils and it will be destroyed. It has been reported overseas as a case of dielectric breakdown. In addition, it has been thought that the deterioration of oil-filled cables that use oil-impregnated paper as the same insulator is very gradual, but in recent years, dielectric breakdown cases in oil-filled cable lines have been confirmed. However, it has not been reported that the cause of dielectric breakdown is copper sulfide formation.

The reaction mechanism involved in the formation of copper sulfide has been investigated in detail in relation to the antioxidant dibenzyldisulfide (hereinafter, may be abbreviated as "DBDS") added to the insulating oil. That is, DBDS is adsorbed on coiled copper, then DBDS reacts with coiled copper to form a DBDS-copper complex, which is further decomposed into benzyl radicals, benzylsulphenyl radicals and copper sulfide. It has been reported that the reaction occurs (see, for example, Patent Documents 1 to 3).

In Patent Document 1 and Patent Document 2, insulating oil is collected from an operating transformer, and DBDS, its decomposition products, by-products, etc. are analyzed to predict the formation of copper sulfide, resulting in an abnormality in oil-containing electrical equipment. Discloses a method for diagnosing the degree of risk of. Further, Patent Document 3 discloses a method of measuring the concentration of dibenzyl sulfoxide in the insulating oil when the insulating oil is in an air atmosphere and estimating the amount of copper sulfide produced based on the concentration. There is.

However, in the above diagnostic method, it is indispensable that DBDS is added to the insulating oil, and in the case of an oil-filled cable that basically uses an insulating oil to which DBDS is not added, it is in the insulating oil. There is a problem that the amount of copper sulfide produced in the insulating oil cannot be estimated from the amount of DBDS-copper complex produced. In addition, conventionally, as an inspection technique for oil-containing cables, the dielectric normal contact (tan δ) of the insulating oil is measured, the gas in the insulating oil is analyzed, and the combustible is generated by partial discharge (local dielectric breakdown of the insulating oil). Oil gas analysis using the amount of sex gas as a measure of the degree of deterioration is common, and a method of diagnosing the degree of risk from the production status of organic copper compounds and copper sulfide has not been implemented.

JP-A-2010-010439 Japanese Unexamined Patent Publication No. 2012-156232 JP-A-2014-045212

The present invention has been made in view of the above-mentioned conventional problems, and estimates the production status of the organic copper compound and copper sulfide in the oil-containing cable, and the production status of the organic copper compound and copper sulfide estimated by the method. It is an object of the present invention to provide a diagnostic method for evaluating the risk of abnormal occurrence of an oil-containing cable based on the above.

In order to solve the above problems, the present inventors have diligently studied. As a result, based on the results of dismantling of oil-containing cables using insulating oil, copper sulfide is also produced in the oil-containing cable; the amount of molten copper in the insulating oil that is thought to be the cause of copper sulfide formation (hereinafter referred to as oil). A correlation is observed between the amount of dissolved copper in the oil and the dielectric tangent (tan δ) of the insulating oil; the change over time between the amount of dissolved copper in the oil and the dielectric tangent (tan δ) during the production of organic copper compounds and copper sulfide. In the trend graph showing, each value tends to decrease after reaching the maximum value; flammable gas is generated in the insulating oil during the formation of the organic copper compound and copper sulfide, and the flammable gas in the insulating oil. We focused on the increase in total amount (Total Copper Gas: TCG);
Then, the production status of the organic copper compound and copper sulfide can be estimated from the amount of dissolved copper in the oil, the dielectric positive contact (tan δ) and the amount of flammable gas (TCG) of the insulating oil collected from the oil-containing cable, and this method can be used. We have found that it is possible to diagnose the risk of abnormal occurrence of oil-containing cables based on the estimated production status of organic copper compounds and copper sulfide, and have completed the present invention.

That is, the method for estimating the copper sulfide production state of the present invention is
A method for estimating the production status of an organic copper compound and copper sulfide in an oil-containing cable using insulating oil.
Insulating oil is sampled from the cable according to the progress of use of the oil-containing cable, and the amount of dissolved copper in the oil, the dielectric normal contact (tan δ) and the total amount of flammable gas (TCG) of the insulating oil are measured and obtained. Step 1 of creating a trend graph showing changes over time in at least one of the amount of dissolved copper in oil and the dielectric positive contact (tan δ) and the total amount of flammable gas (TCG) based on the measured values.
Including step 2 of determining the maximum amount of dissolved copper in oil by the following formula (1) based on the measured value obtained in step 1.
In the created trend graph, the period during which the amount of dissolved copper in oil or the value of dielectric tangent (tan δ) reaches the maximum value and then decreases is estimated as the production period of the organic copper compound and copper sulfide. From the maximum amount of dissolved copper in oil obtained in 1 and the maximum value of the total amount of flammable gas (TCG) in the production period of the organic copper compound and copper sulfide shown in the trend graph, the organic copper compound and copper sulfide in the oil-filled cable It is characterized by estimating the generation status of.
_{[Cu] max = (tanδ max} -tanδ 0) × {[Cu] / (tanδ-tanδ 0)} ··· (1)
(However, in the above formula (1), [Cu] _max is the maximum amount of dissolved copper in oil, and tanδ _max is the maximum value derived from the trend graph of dielectric loss tangent (tanδ) prepared in step 1. Yes, tan δ ₀ is the value of the dielectric loss tangent (tan δ) of the insulating oil (new insulating oil) before the start of use of the oil-containing cable, and tan δ and [Cu] are the values after the start of use of the oil-containing cable, respectively. It is each value of the dielectric loss tangent (tan δ) of the insulating oil and the amount of molten copper in the oil at the time point.

In the method for estimating the production status of the organic copper compound and copper sulfide of the present invention, the conductor constituting the oil-containing cable reacts with the hydrocarbon or non-hydrogen compound in the insulating oil to form a copper complex or a copper compound. It dissolves in the insulating oil, and the copper complex aggregates on the insulating paper of the reinforcing insulating layer in the high electric field region by dielectric migration, and promotes the oxidation of the insulating oil and the bonding reaction with the copper complex or copper compound as a copper catalyst. It is based on the presumption that an organic copper compound is produced, and thus copper sulfide is produced, and this organic copper compound or copper sulfide is dielectrically migrated to a high electric field region and aggregated and deposited on insulating paper.
Further, regarding the insulating oil before using the oil-containing cable, a positive linear correlation is observed between the dielectric positive contact (tan δ) and the amount of dissolved copper in the oil. Therefore, the maximum dissolution in the oil is based on the above formula (1). The amount of copper can be calculated, and it is estimated that the larger the maximum amount of dissolved copper in oil, the larger the amount of organic copper compound and copper sulfide produced.

In addition, the amount of dissolved copper in oil and the trend of dielectric loss tangent (tan δ) correlate. It is possible to estimate the production status of the organic copper compound and copper sulfide using any of the parameters. It can be arbitrarily selected in consideration of the amount of stored data, high reliability, ease of data processing, and the like.

Further, in the method for estimating the copper sulfide production state of the present invention,
Further including step 3 for obtaining the amount of decrease from the maximum amount of dissolved copper in oil based on the measured value obtained in the step 1 and the maximum amount of dissolved copper in oil obtained in the step 2.
It is preferable to estimate the production status of the organic copper compound and copper sulfide in the oil-containing cable by further using the amount of decrease from the maximum amount of dissolved copper in oil obtained in step 3.

Further, in the method for estimating the copper sulfide production state of the present invention,
Further including step 4 for determining the ratio of dielectric loss tangent (tan δ) to the amount of dissolved copper in oil based on the measured value obtained in step 1.
It is preferable to further use the ratio of the dielectric loss tangent (tan δ) to the amount of dissolved copper in oil obtained in step 4 to estimate the production status of the organic copper compound and copper sulfide in the oil-containing cable.

Moreover, the diagnostic method of this invention
This is a diagnostic method for evaluating the risk of abnormalities occurring in an oil-filled cable using insulating oil.
Insulating oil is sampled from the cable according to the progress of use of the oil-containing cable, and the amount of dissolved copper in the oil, the dielectric normal contact (tan δ) and the total amount of flammable gas (TCG) of the insulating oil are measured and obtained. Step 1 of creating a trend graph showing changes over time in at least one of the amount of dissolved copper in oil and the dielectric positive contact (tan δ) and the total amount of flammable gas (TCG) based on the measured values.
Based on the measured values obtained in the above step 1, the step 2 in which the maximum amount of dissolved copper in oil is obtained by the following formula (1), and
Based on the measured value obtained in the step 1 and the maximum amount of dissolved copper in oil obtained in the step 2, the amount of decrease from the maximum amount of dissolved copper in oil is obtained in step 3 and
Including step 4 of determining the ratio of dielectric loss tangent (tan δ) to the amount of dissolved copper in oil based on the measured value obtained in step 1.
An oil-filled cable in which at least one of the amount of dissolved copper in oil and the dielectric loss tangent (tan δ) shown in the trend graph prepared in step 1 is in a nearly steady state during or after the decrease is evaluated as requiring diagnosis.
Regarding the oil-containing cable evaluated as requiring diagnosis, (a) the maximum amount of dissolved copper in oil obtained in the step 2 and (b) flammability during the production period of the organic copper compound and copper sulfide shown in the trend graph. The maximum value of the total amount of gas (TCG), (c) the amount of decrease from the maximum amount of dissolved copper in oil obtained in the step 3, and (d) the dielectric tangent (tan δ) with respect to the amount of dissolved copper in the oil obtained in the step 4. ) Is evaluated based on each preset reference value, and the degree of risk is evaluated.
_{[Cu] max = (tanδ max} -tanδ 0) × {[Cu] / (tanδ-tanδ 0)} ··· (1)
(However, in the above formula (1), [Cu] _max is the maximum amount of dissolved copper in oil, and tanδ _max is the maximum value derived from the trend graph of dielectric loss tangent (tanδ) prepared in step 1. Yes, tan δ ₀ is the value of the dielectric loss tangent (tan δ) of the insulating oil (new insulating oil) before the start of use of the oil-containing cable, and tan δ and [Cu] are the values after the start of use of the oil-containing cable, respectively. It is each value of the dielectric loss tangent (tan δ) of the insulating oil and the amount of molten copper in the oil at the time point.

Further, in the diagnostic method of the present invention, (a) the maximum amount of dissolved copper in oil obtained in the step 2 and (b) the total amount of flammable gas in the production period of the organic copper compound and copper sulfide shown in the trend graph ( When both the maximum value of TCG) and the maximum value exceed each preset reference value, it is preferable to evaluate that the risk level is higher.

Since the amount of dissolved copper in oil is an index showing the amount of copper that is a factor in the production of the organic copper compound and copper sulfide, it is a factor directly linked to the production of the organic copper compound and copper sulfide. In addition, the total amount of flammable gas (TCG) is an index showing an increase in the dissolved gas of insulating oil, and is therefore important in evaluating the risk of partial discharge.

According to the method for estimating the production status of the organic copper compound and copper sulfide of the present invention, the amount of dissolved copper in oil or the value of the dielectric tangent (tan δ) shown in the trend graph shows a maximum value and then decreases. Since the period is estimated to be the production period of the organic copper compound and copper sulfide, the production status of the organic copper compound and copper sulfide is based on the amount of dissolved copper in the oil or the value of the dielectric constant tangent (tan δ) of the insulating oil collected from the oil-containing cable. Can be estimated.
Further, according to the diagnostic method of the present invention, gas analysis in oil (diagnosis of trend tendency of gas generated by partial discharge or thermal deterioration), diagnosis of decrease tendency of electrical characteristics of insulating oil (tan δ, TCG, volume resistance, AC) Oil using insulating oil to which dibenzyldisulfide is not added because the diagnosis is made based on the copper sulfide formation mechanism from a viewpoint different from the conventional diagnostic methods such as pressure resistance measurement) and water infiltration diagnosis (water content measurement). Deterioration diagnosis is also possible for incoming cables.

Furthermore, since the measurement data of the dielectric loss tangent (tan δ) of the insulating oil and the total amount of flammable gas (TCG) in the insulating oil are used, a trend graph can be created from the measurement data accumulated from the operation of the oil-filled cable. .. Further, according to the above formula (1), the maximum amount of molten copper in oil can be easily calculated from the maximum value of the dielectric tangent (tan δ) of the insulating oil, and the maximum value of the total amount of flammable gas (TCG) in the production period and the maximum value. The risk is evaluated by associating with the wide and narrow data of the copper sulfide production range in the disassembled oil-filled cable, along with the amount of decrease from the maximum amount of dissolved copper in oil and the ratio of the dielectric tangent (tan δ) to the amount of dissolved copper in oil. Can be diagnosed.

Therefore, it is possible to easily and accurately diagnose an oil-containing cable, which has been in operation for 30 to 40 years, while utilizing the conventional accumulated data.

It is a figure which shows an example of (a) cross-sectional view and (b) connection part structure of an OF cable. It is a figure which shows the example of the organic copper compound and copper sulfide production of a cable core part. (A); It is a photograph which shows the example generated along the oil gap. (B); It is a photograph which shows the example generated in the cable core (the whole insulating paper). It is a figure which shows the tendency of organic copper compound, copper sulfide formation in the reinforcing layer of the aged OF cable which was dismantled and investigated. It is a figure which shows the tendency of organic copper compound, copper sulfide formation in the reinforcing layer of the aged OF cable which was dismantled and investigated. It is a figure which shows an example of the trend graph which shows the time-dependent change of tan δ, TCG. It is a correlation diagram of the amount of dissolved copper in oil and tan δ. It is a correlation diagram of the amount of dissolved copper in oil and tan δ in the insulating oil in which copper is dissolved from a copper rod using the insulating oil before use for the OF cable. It is a relationship diagram between the amount of dissolved copper in oil and the dismantling survey result. It is a correlation diagram of the amount of dissolved copper in oil, tan δ, and the cohesive force of an organic copper compound. It is a figure which shows the amount of dissolved copper in oil, tan δ, TCG, H _{2 amount by the shape of the trend graph.}

Hereinafter, a method for estimating the production status of an organic copper compound and copper sulfide in an oil-containing cable (hereinafter referred to as an OF cable) according to the present invention, and a diagnostic method for evaluating the risk of abnormal occurrence will be described in detail.

≪Deterioration status of OF cable≫
An example of the OF cable is shown in FIG. FIG. 1A shows a cross-sectional view of an OF cable, and FIG. 1B shows an OF cable connection portion structure. In the OF cable, if the oil-impregnated insulating paper is simply used as an insulator, bubbles are generated in the insulating oil due to the pressure drop of the insulating oil due to the temperature change, and the required characteristics are not satisfied. Therefore, the OF cable is inside the conductor (or metal cover). It is designed to withstand high electric field strength by providing an oil passage and constantly applying a pressure of atmospheric pressure or higher to the insulating oil by an oil tank installed outside. As shown in FIG. 1B, the insulator of the OF cable is configured by wrapping a tape-shaped insulating paper and impregnating it with insulating oil. At that time, in order to improve the bending characteristics, the insulating paper is usually not wrapped and the gaps are evenly provided.

Factors that reduce the insulation performance of the OF cable are considered to be a decrease in the degree of polymerization of the insulating paper due to overheating, damage / deformation / collapse of the insulator due to vibration / thermal expansion / contraction, negative pressure, oil leakage, and abnormal insulation oil characteristics. , Various inspection techniques have been reported and implemented conventionally. As inspection technology, for example, gas analysis technology in oil (diagnosis of trend tendency of gas generated by partial discharge or thermal deterioration), electrical characteristics of insulating oil (tan δ, TCG, volumetric resistance, AC withstand voltage measurement) tend to decrease. There are techniques for diagnosing, water infiltration diagnosis (water content measurement), and the like.

The electrical characteristics of the OF cable have a margin with respect to the AC voltage, but if there is a defect due to the displacement or damage of the insulating paper due to core displacement, etc., partial discharge will occur at the defective part due to the intrusion of overvoltage and gas will be generated. , If it is repeated, it may exist as a void in the defective part. Further, since the void has a remarkably low dielectric strength, it is conceivable that partial discharge will continue when an AC voltage is applied.

Figure 2 shows the organic copper compound that was formed and deposited in a streak shape along the oil gap in the cable core (cable insulator) as a result of removing the aged OF cable that had been operated for more than 30 years in the actual equipment and conducting a disassembly survey. It is a photograph showing an example in which punctate organic copper compounds and copper sulfide (FIG. 2 (b)) were formed and deposited on the entire cable core (insulating paper) or copper sulfide (FIG. 2 (a)). Organocopper compounds and copper sulfide in the cable core tend to form and deposit most in the cable core below the semi-stop.

Further, as shown in FIG. 3, most of the formation and deposition occur in the gap portion, but there are cases where the formation and deposition occur in the entire insulating paper. Organocopper compounds and copper sulfide are formed and deposited in the order of outer layer to inner layer to middle layer of the cable core, but there are cases where organic copper compounds and copper sulfide are formed and deposited up to the vicinity of the middle layer in cables with dielectric breakdown. ..

FIG. 4 shows an example of a generation situation that may lead to dielectric breakdown. As shown in FIG. 4, when copper sulfide is formed and deposited up to the middle layer in a place where the upper and lower oil gaps are close to each other or connected to each other, the copper sulfide formation and depositing portion is also connected from the inner and outer layers to the middle layer. As a result, the insulation performance is significantly reduced, and the possibility of dielectric breakdown increases.

≪Copper sulfide formation mechanism in OF cable≫
In the conventional production of copper sulfide in insulating oil to which DBDS is added, DBDS reacts with copper in the conductor, the DBDS-copper complex diffuses into the insulating oil, and the DBDS-copper complex diffused in the oil becomes the insulating paper. It is presumed that this is due to the mechanism that copper sulfide is produced by adsorbing to copper and decomposing it by thermal energy.

On the other hand, in the present invention, in the formation of copper sulfide in the OF cable, (i) the conductor reacts with the insulating oil, (ii) is dissolved in the insulating oil as a copper complex or a copper compound, and (iii) the dissolved copper complex is formed. Alternatively, the copper compound aggregates in the high electric field region by dielectric migration, and (iv) promotes the oxidation of the insulating oil and the bonding reaction with the copper complex or the copper compound as a copper catalyst to produce a high molecular weight organic copper compound. v) The produced organic copper compound is further aggregated in the high electric field region by dielectric migration, and the copper complex, copper compound or organic copper compound aggregated in the high electric field region reacts with the sulfur component contained in the insulating paper or insulating oil. It is presumed that this is due to the mechanism by which copper sulfide is produced. In the present invention, the sulfur component that reacts with the copper complex, the copper compound, or the organic copper compound is not limited to the component added to the insulating oil like DBDS, but is the sulfur compound used in the production of the insulating paper. It is assumed that the sulfur component derived from it and the sulfur component derived from petroleum, which is a raw material of insulating oil, are also contained.

Further, in the above mechanism, it is presumed that the copper complex or the copper compound reacts with the insulating oil to produce a polymer-like organic copper compound. Such an organic copper compound is a solid substance having a large molecular weight, and agglomerates in a high electric field region by dielectrophoresis and deposits on a cable core or the like, which causes deterioration of insulation performance and dielectric breakdown like copper sulfide. Is assumed.

That is, the copper sulfide formation mechanism according to the present invention assumes that an organic copper compound and copper sulfide are formed over time, although the reaction rate is very slow even in the case of an insulating oil to which a sulfur compound is not added, such as DBDS. Based on this, it is estimated that the three conditions of copper + insulating oil + high electric field are necessary for the formation of organic copper compounds and copper sulfide.

≪Diagnostic method based on copper sulfide formation mechanism≫
According to the copper sulfide formation mechanism in the OF cable described above, (ii) when the copper complex or copper compound is dissolved in the insulating oil, the amount of dissolved copper in the oil and the dielectric positive contact (tan δ) of the insulating oil increase. After that, when (iii) the copper complex or copper compound aggregates in the high electric field region, the amount of dissolution reaches the maximum value, and eventually, (iv) dissolution in oil with the formation of organic copper compound and (v) formation of copper sulfide. The amount of copper and the dielectric tangent (tan δ) of the insulating oil are reduced.

On the other hand, the gas generated by the formation reaction of the copper complex and the formation reaction of the organic copper compound and copper sulfide is absorbed by the insulating oil, so that the gas concentration in the oil increases and the total amount of flammable gas (TCG) in the oil increases. The measured value of is increased.

FIG. 5 is an example of a trend graph showing the increase / decrease in the dielectric loss tangent (tan δ) of the insulating oil and the total amount of combustible gas (TCG) in the oil based on the copper sulfide formation mechanism in the OF cable over time. ..

Here, the trend graph of dielectric loss tangent (tan δ) correlates with the trend of the amount of dissolved copper in oil. That is, from the trend graph (FIG. 5) of the amount of dissolved copper in oil and the dielectric tangent (tan δ), the “decrease” period of these characteristic values is the production period of the organic copper compound and copper sulfide (note that in FIG. 5, “ (It is abbreviated as "copper sulfide formation period"), and if these characteristic values (absolute values) are large, the amount of dissolved copper in the oil that becomes the organic copper compound and copper sulfide is large, so organic copper It can be estimated that the amount of compound and copper sulfide produced will be high. Therefore, it is possible to estimate the production status of the organic copper compound and copper sulfide in the OF cable from the maximum amount of dissolved copper in oil or the dielectric loss tangent (tan δ) shown in the trend graph.

<Measurement and analysis of characteristic values required for diagnosis>
FIG. 6 is an example of a correlation diagram between the amount of dissolved copper in oil and the dielectric loss tangent (tan δ). As a mock test, using the insulating oil before use for the OF cable, insulating oil with different amounts of dissolved copper in the oil was prepared for the insulating oil in which copper was dissolved from the copper rod and the insulating oil in which the copper compound was dissolved. For each insulating oil, the amount of dissolved copper in the oil and the dielectric tangent (tan δ) value were measured, the obtained measured values were plotted, an approximate straight line was drawn, and the correlation coefficient was obtained. In addition, the amount of dissolved copper in the oil and the tan δ value were measured for the insulating oil collected from the actual equipment, and the obtained measured values were plotted.

From the results of FIG. 6, in the insulating oil in which copper or a copper compound is dissolved, the correlation coefficient between the amount of dissolved copper in the oil and the dielectric tangent (tan δ) is 0.9 or more, and the correlation coefficient is 0.9. From the above, the linearity was confirmed.

FIG. 7 is a graph in which both axes are integers for the measurement result of the insulating oil in which copper is dissolved from the copper rod by using the insulating oil before use for the OF cable from the result of FIG.
From FIG. 7, it was confirmed that the approximate expression of the approximate straight line showing the relationship between the amount of dissolved copper in oil and the dielectric loss tangent can be expressed by a linear expression.
Based on these findings, the present inventors have found that the maximum amount of dissolved copper in oil can be estimated from the past maximum value of the tan δ value by the following formula (1).
_{[Cu] max = (tanδ max} -tanδ 0) × {[Cu] / (tanδ-tanδ 0)} ··· (1)
In the above formula (1), tan δ _max is the record maximum value of dielectric loss tangent (tan δ), tan δ ₀ is the value of dielectric loss tangent (tan δ) of new insulating oil, and tan δ and [Cu] are respectively. These are the values of the dielectric loss tangent (tan δ) of the insulating oil collected at a certain point in time and the amount of molten copper in the oil from the actual equipment after the start of use.

According to the above formula (1), the value of the dielectric tangent (tan δ) of the new insulating oil, the maximum value of the past dielectric tangent (tan δ) of the insulating oil collected from the actual equipment, and a certain time point (for example, the latest). The maximum amount of molten copper in oil can be easily calculated from the values of dielectric tangent (tan δ) and the amount of dissolved copper in oil at the time of measurement), and the production status of organic copper compounds and copper sulfide can be estimated from this. It becomes possible.
That is, when the maximum amount of dissolved copper in oil is large, it can be estimated that the amount of organic copper compound and copper sulfide produced is large because the amount of dissolved copper in oil that becomes the organic copper compound and copper sulfide is large. .. If the difference between the maximum amount of dissolved copper in oil and the amount of dissolved copper in oil at the latest measurement (the amount of decrease from the maximum amount of dissolved copper in oil) is large, the organic copper compound and the amount of copper dissolved in oil are already present at the time of measurement. It can be estimated that a large amount of copper sulfide is produced.

Further, as shown in FIG. 8, the present inventors used an insulating oil having a value of dielectric tangent (tan δ) higher than the correlation line with respect to the amount of molten copper in the oil, based on the results of the dismantling survey of the actual equipment. In the equipment, organic copper compounds and copper sulfide are generated in many places in the equipment, and organic copper compounds and copper sulfide are generated in a wide range of the reinforcing layer, from the inner and outer layers of the cable core to the vicinity of the middle layer. I have confirmed that.

As shown in FIG. 8, the plot of the dielectric tangent (tan δ) of the equipment in which the organic copper compound and copper sulfide were generated at many places in the equipment shows the dielectric tangent (tan δ) (%) and the molten copper in oil. It exists above the straight line (straight line with a slope of 0.9 (% / ppm)) representing the correlation of quantity (ppm).

That is, when 0.9 (% / ppm) is set as the reference value, the ratio of the amount of dissolved copper in oil measured for unknown insulating oil to the dielectric tangent (tan δ) is larger than the reference value (measured value is from a straight line). (If present in the upper part), it is possible to presume that organic copper compounds and copper sulfide are produced in many places in the facility. On the contrary, when the ratio of the amount of dissolved copper in oil to the dielectric loss tangent (tan δ) is smaller than the reference value (when the measured value is below the straight line), the production of organic copper compound and copper sulfide is in the facility. It is possible to estimate that it will stay in a narrow range.

<Diagnosis>
At the time of diagnosis, evaluation is carried out in the order of "diagnosis I" and "diagnosis II".

In the first "diagnosis I", the equipment corresponding to the production stage of the organic copper compound and copper sulfide is extracted.
When extracting the relevant equipment, the trend graph shapes of dielectric tangent (tan δ) are classified into four types in Table 1, and the production status of organic copper compounds and copper sulfide is estimated for each of them, and the organic copper compounds and copper sulfide Extract the equipment in and before and after the production period.

Then, when the item requiring diagnosis is "diagnosis required", the next "diagnosis II" is performed. When "Caution required", it is better to shorten the measurement and evaluation interval of "Diagnosis I" and perform "Diagnosis II" again when the graph shows a decreasing tendency (organocopper compound and copper sulfide production period). .. When it is "not necessary", the measurement and evaluation of "diagnosis I" may be performed at a normal pace.

That is, in the diagnostic method for evaluating the risk of abnormality occurrence in the oil-containing cable of the present invention, as step 1, the insulating oil collected from the oil-containing cable has the amount of dissolved copper in the oil, the dielectric loss tangent (tan δ), and flammability. The total amount of gas (TCG) is measured, and based on each measured value, a trend graph showing at least one of the amount of dissolved copper in oil and the dielectric loss tangent (tan δ) and the time course of the amount of flammable gas (TCG) is created. ..

Then, after at least one of the amount of dissolved copper in oil and the dielectric loss tangent (tan δ) shown in the trend graph created in step 1 shows a maximum value, an oil-containing cable that is in a decreasing process or in an almost steady state after the decrease is extracted. However, since it can be estimated that the organic copper compound and copper sulfide are produced in the cable, it is preferable to evaluate it as requiring diagnosis.

In the next "Diagnosis II", the equipment risk is diagnosed from the production status of the organic copper compound and copper sulfide.
That is, using the values of the amount of dissolved copper in oil, the dielectric tangent (tan δ) and the total amount of flammable gas (TCG) measured for the insulating oil collected from the oil-containing cable, (a) the maximum amount of dissolved copper in oil, ( b) Calculate the maximum value of the total amount of flammable gas (TCG), (c) the amount of decrease from the maximum amount of dissolved copper in oil, and (d) the ratio of the dielectric tangent (tan δ) to the amount of dissolved copper, and set the value of each item. Evaluate based on the following evaluation criteria, and diagnose the risk of equipment based on the following diagnostic criteria from the evaluation results.

Here, (a) the maximum amount of molten copper in oil is calculated based on the following formula (1). However, in the following equation (1), tan δ _max is the maximum value derived from the trend graph of the dielectric loss tangent (tan δ) created in step 1, and tan δ _{0 is the insulating oil (tan δ 0)} before the start of use of the oil-containing cable. It is the value of the dielectric loss tangent (tan δ) of the new insulating oil), and tan δ and [Cu] are the dielectric loss tangent (tan δ) of the insulating oil and the amount of molten copper in the oil at a certain point after the start of use of the oil-containing cable, respectively. Each value. It should be noted that the time point after the start of use of the oil-containing cable is preferably the most recent measurement time point (at the time of diagnosis), but at any time point in the past during the production period of the organic copper compound and copper sulfide. There may be.
_{[Cu] max = (tanδ max} -tanδ 0) × {[Cu] / (tanδ-tanδ 0)} ··· (1)
When the maximum amount of dissolved copper in oil is large, the amount of dissolved copper in oil that becomes the organic copper compound and copper sulfide is large, so it can be estimated that the amount of organic copper compound and copper sulfide produced is large.

Further, (b) the maximum value of the total amount of flammable gas (TCG) is derived from the trend graph of the total amount of flammable gas (TCG) prepared in step 1, and the production period of the organic copper compound and copper sulfide (STEP 2 and 3). ) Is the maximum value of the total amount of flammable gas.
When the maximum value of the total amount of flammable gas (TCG) is large, the amount of dissolved copper in the oil that becomes the organic copper compound and copper sulfide is large, so it can be estimated that the amount of the organic copper compound and copper sulfide produced is large. ..

Further, (c) the amount of decrease from the maximum amount of dissolved copper in oil is derived from the trend graph of the total amount of flammable gas (TCG) prepared in step 1 after the production period of the organic copper compound and copper sulfide (STEP2 and). 3) is the difference ([Cu] _max- [Cu]) between the amount of dissolved copper in oil ([Cu]) of the insulating oil at a certain point in time and the maximum amount of molten copper ([Cu] _max). It should be noted that a certain time point after the production period of the organic copper compound and copper sulfide (STEPs 2 and 3) is the most recent measurement time point (when making a diagnosis) (the same applies hereinafter).
If the amount of dissolved copper in oil at a certain point after the production period of the organic copper compound and copper sulfide is significantly reduced from the maximum amount of dissolved copper in oil (the amount of decrease is large), it is already organic at that point. It can be estimated that a large amount of copper compound and copper sulfide are produced.

Further, (d) the ratio of the dielectric loss tangent (tan δ) to the amount of dissolved copper in oil is the amount of dissolved copper in oil ([Cu) of the insulating oil at a certain time after the production period of the organic copper compound and copper sulfide (STEP 2 and 3). ]) To the dielectric loss tangent (tan δ) ([Cu] / tan δ).
If the ratio of the amount of dissolved copper in oil to the dielectric tangent (tan δ) is larger than the reference value at a certain point after the production period of the organic copper compound and copper sulfide, at that point, it is already organic in many places in the facility. It can be estimated that copper compounds and copper sulfide are produced.

(Evaluation criteria for each item)
The values calculated for each of the above items are determined by the evaluation criteria shown in Table 2.
The above reference value is an example, and the setting of the numerical value will be described later.

(Diagnostic criteria)
Based on the results of judgment for each item in Table 2, the equipment risk level (4 categories A to D below) is diagnosed according to the criteria shown in Table 3. In the diagnostic method of the present invention, in the above diagnosis I, if the trend shape of the dielectric loss tangent (tan δ) is classified into STEP 0 and STEP 1, the final diagnosis result is D.

In diagnosis II, it is preferable to evaluate how many of the above evaluation items (a) to (d) are applicable. The above diagnostic criteria also correlate with the results of dismantling surveys of oil-filled cables using insulating oil.
In particular, since the evaluation items (a) and (b) correlate with the amount of organic copper compound and copper sulfide produced, it is presumed that the risk is higher when both of them are applicable, and the highest risk rank A is It is premised that both evaluation items (a) and (b) are applicable.
By evaluating and ranking the risk levels in the above order, the risk level of equipment can be judged relatively simply, and results that are consistent with the results of dismantling surveys of oil-filled cables using insulating oil can be obtained. ..

The partial discharge occurrence status is estimated as a "supplementary diagnosis".
Using the trend graph showing the change over time of the dielectric normal contact (tan δ) and the total amount of flammable gas (TCG) of the insulating oil shown in FIG. 5, the production status of the organic copper compound and copper sulfide shown in Table 1 is determined by Diagnosis I. For copper compounds and equipment extracted after copper sulfide formation (classified in STEP3), the total amount of flammable gas set in advance from the maximum value of the total amount of flammable gas (TCG) after the decrease in dielectric tangent (tan δ). Evaluate the magnitude of (TCG) with respect to the reference value.
In the example shown in FIG. 5, the partial discharge generation status is determined by diagnosing the partial discharge generation equipment when the total amount of flammable gas (TCG) is 140 ppm or more after the measurement date 2010 after the decrease of the dielectric loss tangent (tan δ). Can be estimated.

In addition, estimation of difficult copper sulfide formation and dangerous equipment will be carried out as a "supplementary diagnosis".
In this supplementary diagnosis, the amount of sulfur in oil is measured in accordance with the above-mentioned measurement of the amount of dissolved copper in oil.
It can be considered that copper sulfide is not produced by the reaction with the sulfur component contained in the insulating oil in the equipment where the sulfur component was not detected in the collected insulating oil by the measurement of the amount of sulfur in the oil. However, even in such equipment, copper sulfide may be produced by the reaction with the sulfur component contained in the insulating paper or other materials of the OF cable, but such production of copper sulfide is insulating. It is extremely small compared to the amount of copper sulfide produced by the reaction with the sulfur component contained in the oil. Therefore, such equipment can be presumed to be equipment that is difficult to produce copper sulfide because the amount of copper sulfide produced is small.
For equipment that does not use mineral oil, which contains a large amount of sulfur during manufacturing, as the insulating oil, the sulfur component contained in the insulating paper and other materials of the OF cable is transferred to the insulating oil. The amount of sulfur in oil may show a high value at the time of measurement. In this case, since copper sulfide is likely to be produced after the measurement, it can be estimated that the equipment produces a large amount of copper sulfide.
From the above, in equipment where the amount of sulfur in oil is measured in accordance with the measurement of the amount of dissolved copper in oil and sulfur is not detected, it is unlikely that the insulation performance will be significantly reduced due to copper sulfide formation. It can be diagnosed that the risk of In addition, in equipment that does not use mineral oil as insulating oil, if the amount of sulfur in the oil is large, the insulation performance is likely to deteriorate significantly due to the formation of copper sulfide, and the risk of abnormal occurrence due to the formation of copper sulfide increases. Can be diagnosed.

Next, the result of confirming the effect of the diagnostic method according to the present invention will be specifically described, but the present invention is not limited to the following examples.

(1) Confirmation of the effect of this diagnostic method (see Table 4)
For the actual equipment (OF cable 17 wires), the estimated diagnosis result diagnosed based on the diagnosis method of the present invention and the dismantling investigation result were compared. The results are shown in Table 4. The presumptive diagnosis based on the diagnostic method of the present invention and the disassembly survey were carried out by the following methods, respectively.

<Estimated diagnosis based on the diagnostic method of the present invention>
First, for the sample oil collected from each actual facility, the dielectric loss tangent (tan δ) and the total amount of flammable gas (TCG) were measured by the following measurement methods, and based on the obtained measured values, the dielectric loss tangent (tan δ) was obtained. A trend graph showing the time course of the total amount of flammable gas (TCG) was created.
Next, the shape of the dielectric loss tangent (tan δ) trend created for each actual equipment was classified into the four types shown in Table 1 above (diagnosis I).

Further, for the actual equipment (OF cable 17 wires) in which the trend shape of the dielectric loss tangent is classified into STEPs 2 and 3, the amount of dissolved copper in oil is measured by the following measurement method, and the measured value and the dielectric loss tangent measured above are measured. Using the values of (tan δ) and total flammable gas (TCG), (a) maximum amount of dissolved copper in oil, (b) maximum value of total flammable gas (TCG), (c) maximum amount of dissolved copper in oil. The ratio of the dielectric loss tangent (tan δ) to the amount of decrease from (d) the amount of molten copper was calculated.

Next, (a) the maximum amount of dissolved copper in oil, (b) the maximum value of the total amount of flammable gas (TCG), (c) the amount of decrease from the maximum amount of dissolved copper in oil, and (d) calculated for each actual facility. The dielectric loss tangent (tan δ) with respect to the amount of dissolved copper in oil was evaluated by the evaluation criteria in Table 2 above, and the equipment risk was diagnosed based on the diagnostic criteria in Table 3 above from the evaluation results (diagnosis II).

(Measurement condition)
The above-mentioned various measurements were carried out according to the following procedure.
-Measurement of dielectric loss tangent (tan δ) 50 ml of sample oil collected from each actual equipment was placed in a liquid electrode, heated to 80 ° C., 1000 V was applied, and measurement was performed with a tan δ measuring device.

-Measurement of total flammable gas amount (TCG) An oil sampling syringe (200 ml) containing sample oil collected from each actual facility was set in a gas sampling device, and the gas in the oil was separated and extracted by a gas chromatograph and analyzed.

-Measurement of the amount of dissolved copper in oil and the amount of sulfur in oil The sample oil collected from each actual facility was diluted 10-fold with xylene to prepare a prepared solution, and the solution was analyzed by an inductively coupled plasma (ICP) emission spectrometer. .. For the preparation of the standard solution for the calibration curve, a standard solution prepared by diluting a commercially available oil-based copper-containing standard solution with blank oil and xylene in order was used.

<Dismantling survey>
In the dismantling survey, the appearance and location of the black part on the insulating paper, which is the organic copper compound and copper sulfide producing part, were investigated for the creeping surface and inside of the reinforcing insulating paper of the actual equipment, the innermost outer layer and the inner layer of the cable insulating paper. It was carried out by visual confirmation and evaluated based on the following diagnostic criteria.
To confirm the production of organic copper compounds and copper sulfide, an electron microscope and a fluorescent X-ray analyzer were used to identify the location where both copper (Cu) and sulfur (S) were detected in the blackened part on the insulating paper. At that specific location, the organic copper compound was confirmed by the Fourier transform infrared spectrophotometer (FTIR), which detected absorption peaks of insulating oil, oxidation products and sulfur compounds from the infrared absorption spectrum, and copper sulfide was confirmed. It was confirmed that the Raman spectrum of copper sulfide was detected by the microscopic Raman spectrometer.

(Diagnostic criteria)
A: There are wrinkles, oil gaps, and black parts beyond the edges in the inner layer of the reinforcing insulating paper or the inner layer of the cable insulating paper.
B: There are wrinkles, oil gaps, and black parts beyond the edges on the creeping surface of the reinforcing insulating paper or on the innermost and outer layers of the cable insulating paper. Alternatively, there are wrinkles, oil gaps, and black edges on the inside of the reinforcing insulating paper or the inner layer of the cable insulating paper.
C: There are wrinkles, oil gaps, and black parts at the ends along the creeping surface of the reinforcing insulating paper or on the innermost and outer layers of the cable insulating paper.
D: There is no black part.

In Table 4, the diagnostic results based on the diagnostic method of the present invention were underestimated (route name: JH line 3LB23) and overestimated (route name: RH line 1R511) with respect to the dismantling survey results of the actual equipment. ), But the other equipment was the same as the dismantling survey result and the diagnostic result of the present invention, and the overall consistency rate was as high as about 88%.
From these results, it was confirmed that according to the diagnostic method of the present invention, a result corresponding to the result of the dismantling investigation of the actual equipment can be obtained. Further, according to the diagnostic method of the present invention, it is not necessary to disassemble and test the actual equipment as in the dismantling survey, and each measurement and evaluation can be performed only by collecting the test oil from the OF cable, which is relatively relatively. The risk level of actual equipment can be easily diagnosed.

(2) Confirmation of correlation between this diagnostic method and the copper sulfide formation mechanism It was confirmed by the dismantling investigation test of the actual equipment and each evaluation test that the diagnostic method of the present invention has a correlation with the copper sulfide formation mechanism as follows.
(B) Calculation of maximum amount of dissolved copper in oil (see Fig. 6)
Insulating oil with different amounts of dissolved copper in oil (sample insulating oil) in which copper was dissolved from a copper rod, insulating oil in which different amounts of copper compound were dissolved (copper compound dissolved sample insulating oil), and samples collected from actual equipment. FIG. 6 shows the results of measuring the amount of dissolved copper in the oil and tan δ for the insulating oil.
The amount of dissolved copper in the sample insulating oil was measured by heating the insulating oil in which the copper rod was immersed at 80 ° C. in a nitrogen atmosphere, sampling timely over time, and performing the above ICP emission spectroscopic analysis. The amount of dissolved copper in the oil of the copper compound-dissolved sample insulating oil is measured by ICP emission spectroscopic analysis by the above method after dissolving a commercially available copper compound reagent (copper alkylbenzene sulfonate or copper oleate) at an appropriate concentration. did. tan δ was measured using a dielectric loss tangent measuring device.

From FIG. 6, in the copper-dissolved sample insulating oil, a correlation showing a linearity between the amount of dissolved copper in oil and the tan δ value is observed, but in actual equipment, the tan δ value may differ depending on the equipment even if the amount of dissolved copper in oil is the same. Understand. Although the tan δ value increases due to deterioration of the insulating oil (moisture content and thermal deterioration), deterioration of the insulating oil rarely occurs in the OF cable. On the other hand, in FIG. 6, even in the case of the copper-dissolved sample insulating oil in which the copper compound is dissolved, the slope of a line (correlation coefficient) showing the correlation between the amount of dissolved copper in the oil and the tan δ value is shown depending on the type of copper compound used. It has been shown to be different, indicating that the value of tan δ is affected by the morphology of the copper compound dissolved in the insulating oil. Therefore, it is considered that the reason why the value of dielectric loss tangent (tan δ) is different even if the amount of molten copper in oil is the same in the actual equipment is that the form of the molten copper in oil is different for each equipment.
Further, although FIG. 6 is a log-log graph, when both axes are represented by integers from FIG. 7, the approximate straight line can be shown by a linear equation.
From the above, it is possible to calculate the amount of dissolved copper in oil from the tan δ value using the relational expression between the amount of dissolved copper in oil and the tan δ value, and it is dissolved in the insulating oil for each facility. It can be seen that it is necessary to calculate the maximum amount of molten copper for each facility because the form of copper is different.
According to the above formula (1) found by the present inventors, the past maximum tan δ value of the insulating oil of each equipment, the current tan δ value, the amount of dissolved copper in the oil, and the tan δ value of the new insulating oil are used. Therefore, the maximum amount of molten copper in oil for each facility can be calculated.

(B) Estimating the formation period of organic copper compounds and copper sulfide According to the copper sulfide formation mechanism in the OF cable proposed in the present invention, the relationship with the risk of the OF cable associated with the formation of organic copper compounds and copper sulfide is determined. , Can be described in relation to the amount of dissolved copper in oil as follows.
(I) The conductor reacts with the insulating oil. At this stage, the amount of dissolved copper in oil does not change.
(Ii) When copper is dissolved in insulating oil as a copper complex or copper compound, the amount of dissolved copper in the oil gradually increases, and the dissolution is eventually stopped with time.
(Iii) The dissolved copper complex or copper compound aggregates in the oil gap portion of the insulator (insulating paper) by dielectrophoresis in the high electric field region.
(Iv) Furthermore, the agglomeration of the copper complex or copper compound in the high electric field region increases the catalytic effect of the copper complex or copper compound in the insulator oil gap.
(V) Due to the increase in the catalytic medium effect, the oil binds to oxygen, sulfur, and a copper complex or a copper compound and rapidly deteriorates, and a polymer-like organic copper compound is formed in the insulator oil gap. From this stage, the amount of dissolved copper in oil begins to decrease.
(Vi) Since the organic copper compound also aggregates in the high electric field region by dielectric migration, the copper complex or the copper compound and the organic copper compound are sulfur in the insulating paper or the insulating oil (sulfur originally contained in the insulating oil). ) To produce copper sulfide. The amount of dissolved copper in oil gradually decreases with the formation of copper sulfide.
(Vii) When copper sulfide is generated in the oil gap, the amount of dissolved copper in the oil is reduced, and the copper sulfide in the oil gap causes a partial discharge.

Since there is a correlation between the amount of dissolved copper in oil and the tan δ value, it can be said that there is also a correlation between the tan δ trend and the trend of the amount of dissolved copper in oil. Further, from the copper sulfide formation mechanism estimated as described above, when the organic copper compound and copper sulfide are formed, the amount of dissolved copper in the oil decreases, so that the tan δ value also decreases.
From the above, when the tan δ trend decreases, it can be determined that the amount of dissolved copper has decreased due to the formation of the organic copper compound and copper sulfide.

(C) Equipment risk diagnosis from the location and amount of copper sulfide produced [1] Relationship between the amount of dissolved copper in oil and the amount of organic copper compounds and copper sulfide produced The greater the amount of dissolved copper in oil, the more copper sulfide is produced. It can be said that the amount of organic copper compounds and copper sulfide produced also increases.
From the above, it can be judged that the production amount of the organic copper compound and copper sulfide is large in the equipment having a large amount of dissolved copper in the maximum oil.

[2] Relationship between tan δ, the amount of dissolved copper in oil and the production sites of organic copper compounds and copper sulfide (see Tables 5 and 8)
FIG. 8 shows a relationship diagram between tan δ, the amount of dissolved copper in oil, and the production sites of the organic copper compound and copper sulfide. FIG. 8 is a graph showing the relationship between the amount of dissolved copper in oil and tan δ in the actual equipment where the dismantling survey was conducted, and a straight line is drawn so that the ratio of tan δ and the amount of dissolved copper in oil is 0.9. ..
Furthermore, based on the results of the dismantling survey, 11 plots (sample names: A to K) of the graph were shown for facilities with many production sites of organic copper compounds and copper sulfide (wide range of production of organic copper compounds and copper sulfide). The results of determining the ratio of tan δ to the amount of dissolved copper in oil are shown in Table 5.
As a result, the minimum value (sample name: K) of the ratio of tan δ to the amount of dissolved copper in oil was "0.95" and the ratio was 0.9 for equipment with many locations where organic copper compounds and copper sulfide were produced. It was plotted above the straight line of.

However, there were some facilities plotted above the straight line with a ratio of 0.9 even in the facilities where organic copper compounds and copper sulfide were produced in small numbers. However, in the equipment (plot of x) where the amount of dissolved copper in oil was small and the maximum amount of dissolved copper in oil in the past could be calculated, the calculated maximum amount of dissolved copper in oil was as small as 0.1 ppm. That is, since the amount of dissolved copper in the oil was originally small, it can be inferred that the number of production sites was small.

Similarly, for equipment with a dissolved copper content of 1 ppm or more in oil, there was no past data and the trend tendency was unknown, but it can be inferred from this that the production period of organic copper compounds and copper sulfide may be reached.

From the above, if the value of the ratio of tan δ to the amount of dissolved copper in oil is high, it can be judged that the equipment may generate organic copper compounds and copper sulfide in many places, and it is a deterioration equipment that leads to dielectric breakdown. Can be discriminated.

Further, an insulating oil in which several kinds of copper compounds were dissolved was heated in a simulated high electric field region to prepare a solid organic copper compound.
The amount of dissolved copper in the oil and tan δ of the insulating oil in which this organic copper compound was dissolved were measured, and a dielectric migration test was carried out for each insulating oil containing the solid organic copper compound, and the results of examining the correlation were obtained. It is shown in FIG.
The method for measuring the amount of dissolved copper in oil and tan δ is as described above. In the dielectrophoresis test, the insulating oil was placed in a petri dish, two conducting wires were placed under the petri dish, a voltage was applied, and the aggregation time of various solid organic copper compounds was measured. The solid organic copper compound produced was confirmed to be an organic copper compound of the same quality as the actual equipment by an electron microscope, a fluorescent X-ray analyzer, and FTIR by the same method as the above-mentioned disassembly survey.

From the results shown in FIG. 9, the larger the ratio of the amount of dissolved copper in the oil to the tan δ, the more easily the organic copper compound produced as a solid from the copper compound is agglomerated on the lead wire on the power supply side by the dielectrophoresis test. It was confirmed that the time was short (strong cohesive force). From these results, it was found that the ratio of the amount of dissolved copper in oil to the dielectric loss tangent (tan δ) correlates with the cohesive force (dielectrophoretic force) of the solid organic copper compound produced.
In particular, when the ratio of the amount of dissolved copper in oil to tan δ is 0.9 or more, the aggregation confirmation time is less than 1 minute, indicating that the organic copper compound has a strong cohesive force. This also corresponds to the relationship between the equipment in which the organic copper compound and copper sulfide are produced at many locations and the ratio of the amount of dissolved copper in the oil to tan δ, which is shown in FIG. It can be inferred that the organic copper compound easily moves in the actual equipment with strong cohesive force, and the organic copper compound and copper sulfide are produced in a wide range.

[3] Relationship between the amount of dissolved copper in oil and TCG (see FIG. 10)
For the actual equipment (1272 locations), a trend graph of tan δ, the amount of dissolved copper in oil and TCG was created, and the average value of each characteristic value for each graph shape was summarized in FIG.
As a result, when the increase or decrease of tan δ, the amount of TCG tended to be large. From the formation mechanism, it was speculated that various chemical reactions occurred in the processes of copper dissolution, organic copper compound formation, and copper sulfide formation, and TCG was detected as the decomposition product gas generated during this chemical reaction. That is, it can be determined that the larger the amount of TCG, the larger the amount of copper dissolved, the amount of organic copper compound produced, and the amount of copper sulfide produced.
From the above, it can be determined that the larger the amount of TCG when the molten copper is reduced (when the tan δ is reduced), the larger the amount of copper sulfide produced.

(D) For each reference value (see Table 6)
Since each reference value described in the evaluation items of the equipment risk diagnosis in Table 2 above does not have a clear correlation at present, it was set as a provisional reference value from the current test data shown in Table 6. This point needs to be reviewed in the future according to the actual conditions of the equipment.

Table 6 shows (a) the maximum amount of dissolved copper in oil, (b) the maximum value of the total amount of flammable gas (TCG), and (c) the amount of decrease from the maximum amount of dissolved copper in oil for the actual equipment (1272 locations). It is calculated, and based on these values, the mean value, standard deviation (σ), and mean value + σ are shown for each characteristic value. Furthermore, the minimum value of each characteristic value is shown for the actual equipment (2 locations) diagnosed as A rank in the dismantling survey.

Based on the current test data shown in Table 6, (a) the maximum amount of dissolved copper in oil was set to 4.0 ppm as a provisional reference value as a value covering the minimum value of the actual equipment data of the dismantling survey A rank. Further, (b) the maximum value of the total amount of flammable gas (TCG) was set to 260 ppm as a provisional reference value from the average value of the actual equipment (1272 locations). Further, (c) the amount of decrease from the maximum amount of molten copper in oil was set to 5.0 ppm from the average value of the actual equipment (1272 locations) + σ as a provisional reference value.

Regarding (d) the ratio of the dielectric loss tangent (tan δ) to the amount of molten copper, 0.9 is provisionally set based on the graph of the relationship between the amount of molten copper in oil and tan δ in the actual equipment where the dismantling survey shown in FIG. 8 was conducted. It was set as a standard value.

(E) Supplementary diagnosis [Partial discharge occurrence status] (See Table 1, Table 6, and Fig. 10)
TCG amount _{(H 2} amount), tan [delta, the dissolved copper content in the oil is shown in Figure 10 in association with the propensity of an organic copper compound and copper sulfide shown in Table 1 (tan [delta increasing or decreasing trend).
As is clear from FIG. 10, the amount of TCG (H ₂ ) tends to be large (does not decrease) after copper sulfide formation (at STEP 3). In this case, since decomposition gas is not generated by various chemical reactions after copper sulfide is produced, the gas generated by partial discharge (H ₂ is a partial discharge with a large discharge charge amount) is based on the conventional concept of insulating oil analysis. Generated gas). In particular, it can be inferred that a partial discharge occurs at the copper sulfide production site, especially after the copper sulfide production.
From the above, it can be determined that a large amount of partial discharge is generated in the equipment having a large amount of TCG after the production of copper sulfide.

(F) Supplementary diagnosis [Difficulty in producing copper sulfide and dangerous equipment]
In this supplementary diagnosis, the amount of sulfur in oil is measured in accordance with the above-mentioned measurement of the amount of dissolved copper in oil.
It can be considered that copper sulfide is not produced by the reaction with the sulfur component contained in the insulating oil in the equipment where the sulfur component was not detected in the collected insulating oil by the measurement of the amount of sulfur in the oil. However, even in such equipment, copper sulfide may be produced by the reaction with the sulfur component contained in the insulating paper or other materials of the OF cable, but such production of copper sulfide is insulating. It is extremely small compared to the amount of copper sulfide produced by the reaction with the sulfur component contained in the oil. Therefore, such equipment can be presumed to be equipment that is difficult to produce copper sulfide because the amount of copper sulfide produced is small.
For equipment that does not use mineral oil, which contains a large amount of sulfur during manufacturing, as the insulating oil, the sulfur component contained in the insulating paper and other materials of the OF cable is transferred to the insulating oil. The amount of sulfur in oil may show a high value at the time of measurement. In this case, since copper sulfide is likely to be produced after the measurement, it can be estimated that the equipment produces a large amount of copper sulfide.
From the above, in equipment where the amount of sulfur in oil is measured in accordance with the measurement of the amount of dissolved copper in oil and sulfur is not detected, it is unlikely that the insulation performance will be significantly reduced due to copper sulfide formation. It can be diagnosed that the risk of In addition, in equipment that does not use mineral oil as insulating oil, if the amount of sulfur in the oil is large, the insulation performance is likely to deteriorate significantly due to the formation of copper sulfide, and the risk of abnormal occurrence due to the formation of copper sulfide increases. Can be diagnosed.

As described above, the method for diagnosing the risk of occurrence of OF cable abnormality of the present invention can be applied to insulating oil to which dibenzyl disulfide, which is a factor of copper sulfide, is not added, as compared with the conventional diagnostic method. Since the characteristic values (amount of dissolved copper in oil, tan δ, TCG) obtained by the conventional diagnostic method can be used, it has advantages such as simplicity, and can be said to be a simple and accurate diagnostic method. It is also consistent with the actual equipment.

However, since the value of tan δ is affected by the form of molten copper in oil and the form of molten copper in oil differs for each facility, the above diagnostic method needs to be carried out for each OF cable facility.

Claims (5)

A method for estimating the production status of an organic copper compound and copper sulfide in an oil-containing cable using insulating oil.
Insulating oil is sampled from the cable according to the progress of use of the oil-containing cable, and the amount of dissolved copper in the oil, the dielectric loss tangent (tan δ) and the total amount of flammable gas (TCG) of the insulating oil are measured and obtained. A trend graph showing the time course of the dielectric loss tangent (tanδ) and the total amount of flammable gas (TCG) based on the measured values, or the time course of the amount of dissolved copper in oil and the dielectric loss tangent (tanδ ) and the total amount of flammable gas (TCG). Step 1 to create a trend graph showing changes,
Including step 2 of determining the maximum amount of dissolved copper in oil by the following formula (1) based on the measured value obtained in step 1.
In the created trend graph, the period during which the amount of dissolved copper in oil or the value of dielectric tangent (tan δ) reaches the maximum value and then decreases is estimated as the production period of the organic copper compound and copper sulfide. From the maximum amount of dissolved copper in oil obtained in 1 and the maximum value of the total amount of flammable gas (TCG) in the production period of the organic copper compound and copper sulfide shown in the trend graph, the organic copper compound and copper sulfide in the oil-filled cable A method characterized by estimating the generation status of.
_{[Cu] max = (tanδ max} -tanδ 0) × {[Cu] / (tanδ-tanδ 0)} ··· (1)
(However, in the above formula (1), [Cu] _max is the maximum amount of dissolved copper in oil, and tanδ _max is the maximum value derived from the trend graph of dielectric loss tangent (tanδ) prepared in step 1. Yes, tan δ ₀ is the value of the dielectric loss tangent (tan δ) of the insulating oil (new insulating oil) before the start of use of the oil-containing cable, and tan δ and [Cu] are the values after the start of use of the oil-containing cable, respectively. It is each value of the dielectric loss tangent (tan δ) of the insulating oil and the amount of molten copper in the oil at the time point. Further including step 3 for obtaining the amount of decrease from the maximum amount of dissolved copper in oil based on the measured value obtained in the step 1 and the maximum amount of dissolved copper in oil obtained in the step 2.
The method according to claim 1, wherein the production state of the organic copper compound and copper sulfide in the oil-containing cable is estimated by further using the amount of decrease from the maximum amount of dissolved copper in oil obtained in the step 3. .. Further including step 4 for determining the ratio of dielectric loss tangent (tan δ) to the amount of dissolved copper in oil based on the measured value obtained in step 1.
Claim 1 or claim 1, wherein the production state of the organic copper compound and copper sulfide in the oil-containing cable is estimated by further using the ratio of the dielectric loss tangent (tan δ) to the amount of dissolved copper in oil obtained in the step 4. The method according to 2. This is a diagnostic method for evaluating the risk of abnormalities occurring in an oil-filled cable using insulating oil.
Insulating oil is sampled from the cable according to the progress of use of the oil-containing cable, and the amount of dissolved copper in the oil, the dielectric loss tangent (tan δ) and the total amount of flammable gas (TCG) of the insulating oil are measured and obtained. A trend graph showing the time course of the dielectric loss tangent (tanδ) and the total amount of flammable gas (TCG) based on the measured values, or the time course of the amount of dissolved copper in oil and the dielectric loss tangent (tanδ ) and the total amount of flammable gas (TCG). Step 1 to create a trend graph showing changes,
Based on the measured values obtained in the above step 1, the step 2 in which the maximum amount of dissolved copper in oil is obtained by the following formula (1), and
Based on the measured value obtained in the step 1 and the maximum amount of dissolved copper in oil obtained in the step 2, the amount of decrease from the maximum amount of dissolved copper in oil is obtained in step 3 and
Including step 4 of determining the ratio of dielectric loss tangent (tan δ) to the amount of dissolved copper in oil based on the measured value obtained in step 1.
An oil-filled cable in which the dielectric loss tangent (tan δ) shown in the trend graph created in step 1 is in a nearly steady state during or after the decrease is evaluated as requiring diagnosis.
Regarding the oil-containing cable evaluated as requiring diagnosis, (a) the maximum amount of dissolved copper in oil obtained in the step 2 and (b) flammability during the production period of the organic copper compound and copper sulfide shown in the trend graph. The maximum value of the total amount of gas (TCG), (c) the amount of decrease from the maximum amount of dissolved copper in oil obtained in the step 3, and (d) the dielectric tangent (tan δ) with respect to the amount of dissolved copper in the oil obtained in the step 4. ) Is evaluated based on each preset reference value, and the degree of risk is evaluated.
_{[Cu] max = (tanδ max} -tanδ 0) × {[Cu] / (tanδ-tanδ 0)} ··· (1)
(However, in the above formula (1), [Cu] _max is the maximum amount of dissolved copper in oil, and tanδ _max is the maximum value derived from the trend graph of dielectric loss tangent (tanδ) prepared in step 1. Yes, tan δ ₀ is the value of the dielectric loss tangent (tan δ) of the insulating oil (new insulating oil) before the start of use of the oil-containing cable, and tan δ and [Cu] are the values after the start of use of the oil-containing cable, respectively. It is each value of the dielectric loss tangent (tan δ) of the insulating oil and the amount of molten copper in the oil at the time point. Both (a) the maximum amount of dissolved copper in oil obtained in the step 2 and (b) the maximum value of the total amount of flammable gas (TCG) in the production period of the organic copper compound and copper sulfide shown in the trend graph are The diagnostic method according to claim 4, wherein when the value exceeds each preset reference value, the risk is evaluated to be higher.