JP4815824B2 - Resistance value management method for water resistance type neutral point grounding resistors - Google Patents

Description

  The present invention relates to a method for managing a resistance value of a water resistance type neutral point grounding resistor applied to a transformer facility of a power distribution facility.

  The neutral point grounding resistor is a device that instantly acts as grounding to protect the equipment in the system when an abnormal load such as lightning strikes in the power distribution equipment, and is important for ensuring the reliability of the power equipment. Equipment. A water resistance type neutral point grounding resistor (hereinafter abbreviated as a water resistor) is a structure that maintains a predetermined resistance with a neutral solution (such as an aqueous sodium carbonate solution) held in a galvanized container. Yes, because there are no moving parts, it is durable, there is no need for explosion-proof equipment because it does not use oil or gas, etc. Yes.

  If the resistance value is too small, the water resistance type neutral grounding resistor will operate even if the load changes normally, and the system will stop.If the resistance value is too large, the ground will operate even if the load is abnormal. The equipment cannot be protected. For this reason, it is necessary to always manage the resistance value of the water resistance type neutral point grounding resistor within a certain range.

The resistance factors of the water resistance type neutral point grounding resistor are considered to be the following three points from the structure.
1) Electrical resistance in electrode and container metal body 2) Electrical resistance including reaction resistance of product and solution surface on container metal body and electrode surface 3> Electrical resistance depending on conductivity of solution

  Among the above, the electric resistance in the metal body is negligibly small with respect to the entire resistance value. In addition, there is almost no change during the period of equipment operation. However, when the equipment is in service, the water resistance type neutral point grounding resistor is caused by the growth of the surface product due to the contact of the electrode or the container surface with the solution and the change in the conductivity of the solution due to the change in the composition of the solution accompanying the film formation The resistance value of changes. Therefore, conventionally, the resistance value of the water resistance type neutral point grounding resistor to be measured is regularly measured, and if it is out of the control range, the conductivity of the internal neutral solution is adjusted to adjust the resistance. It is managed so that the value is appropriate.

  At present, the resistance value is measured by a method of directly measuring the energization resistance value by disconnecting the system protected by the water resistance type neutral point grounding resistor to be measured. However, this method has the following effects: 1) Since the transmission system is stopped, there is an influence such as a power outage at the customer and an increase in load on the power system; 3) Measurement time is required, and a special instrument dedicated to the measurement is required and the measurement cost is high. For this reason, there existed the subject of the improvement of the equipment maintenance quality of a water resistance type neutral point grounding resistor resulting from restrictions on measurement time and frequency, and reduction of equipment maintenance cost.

  Patent Document 1 discloses that an electrode member of a sensor for measuring liquid resistivity is formed of a nickel-based alloy containing 19 to 24% by mass of chromium and 1 to 7% by mass of iron. Since the electrode member has good corrosion resistance and oxidation resistance, stable cleaning management is possible in the semiconductor wafer cleaning process, and electrode characteristic management and electrode replacement are not required over a long period of time. It is.

JP 2000-46773 A

The present invention has been made in view of the above problems, disconnect from the grid may be able to manage the resistance value required in conductible state, no measurement timing constraints, and easily even in the field It is an object of the present invention to provide a resistance value management method for a water resistance type neutral point grounding resistor that can be implemented.

  The present inventors have intensively studied to solve the above problems. In order to investigate the cause of the resistance fluctuation of the water resistor, the investigation was conducted focusing on the relationship between the surface condition of the galvanization of the electrode and the container and the energization resistance. The galvanized surface generates zinc hydroxide or zinc carbonate initially in a unique aqueous solution containing sodium carbonate in the water resistor so that the metal zinc in the plating layer is consumed and the iron-zinc alloy comes into contact with the aqueous solution. As a result, it was found that iron oxide and iron hydroxide were produced on the surface layer together with the zinc product. Furthermore, it was confirmed that the corrosion accompanied with hydrogen generation proceeds remarkably when the ground iron is exposed. It was also found that the resistance value fluctuates greatly during the initial zinc hydroxide or zinc carbonate generation period, but the resistance becomes stable when the zinc surface is covered with a thick product. When the resistance is stabilized, the main governing factor of the resistance variation of the water resistor is the conductivity of the internal solution.

Next, water resistors that can be used to manage the conductivity of the internal solution were studied. As a result, the resistance value of the water resistance type neutral point grounding resistor when measured by direct energization during initial operation is R ₀ (Ω), and the resistance value when measured by direct energization at a certain time is R ₁ ( Ω), and R ₀ , R ₁ and R ₂ are | R ₁ −R ₂ | ÷ (R ₀ × T) <, where R ₂ (Ω) is the resistance value measured after a certain period T months It was found that the water resistor satisfies the relationship of 0.05. It is inferred that after the zinc surface is covered with the product and the resistance value of the zinc surface is stabilized, the resistance variation of the water resistor is governed by the change in the conductivity of the solution during the period until the steel is corroded. It was done. Therefore, assuming that the corrosion rate of zinc is 4 g / m ² , the average adhesion amount of zinc is 100 g / m ^2, and the remaining amount of zinc plating at the time of transition to corrosion of the steel is 20%, it is governed by the change in conductivity of the solution. The period was about 20 years and was long.

Solution of water resistive neutral in ground resistor, because it is possible harvested while still conductible, as the resistance value managing water resistive neutral grounding resistor resistance value is stabilized zinc surface The resistance value management method based on the conductivity of the solution was examined.

  The measurement of conductivity by a conductivity meter has been conventionally performed when adjusting the internal solution. Using this conductivity meter, an attempt was made to manage resistance values with collected solutions at multiple departments that have jurisdiction over water resistance type neutral point grounding resistors. As a result, the dispersion of measured values was large and the reproducibility within the measurement period was also poor. It was confirmed. The reason for this is that platinum black, an electrode material, must always be stored and managed in pure water. However, it is difficult to manage such electrodes in a department where a water resistor is not fully equipped with a pure water production system. I found out that it was happening. In addition, since the conductivity meter having a platinum black electrode was expensive, a conductivity meter that was easy to manage and relatively inexpensive was studied.

  As a result of the study, there are two requirements for the electrode material: no deterioration during storage in the atmosphere, and that the immersion potential, which is a measure of electrode stability in the solution environment inside the water resistor, is stabilized in a short time. As an electrode material satisfying these requirements, the content of Cr and Mo, which is mainly composed of Fe or Ni and expressed in mass%, is Cr mass% + Mo mass% / 3 ≧ 25. The alloy which satisfy | fills, and titanium and carbon were discovered. When a measuring instrument composed of titanium and carbon was purchased from a commercially available conductivity meter and tested in multiple departments, it was confirmed that the reproducibility during actual measurement and the storage management of the equipment were good.

  Furthermore, it is necessary to compare the data of each department and the past with the conductivity at the same temperature. Although the method of measuring by adjusting the temperature of the solution to 25 ° C. at the time of measuring conductivity is reliable, it is not suitable for measurement in a short time. Therefore, the temperature correction of the actual solution data was performed using the temperature correction function incorporated in the measuring instrument, but it was found that the corrected data is different from the actually measured value. As a result of investigating the cause, the temperature correction mechanism built into the commercially available measuring instrument is compatible with chloride-based solutions similar to the temperature correction method specified in JIS, and is a water resistance neutral type. It was found that the carbonic acid based internal solution unique to the point grounding resistor is difficult to apply because the temperature correction coefficient is completely different. Therefore, using the content solution of the water resistance type neutral point grounding resistor, creating a temperature correction curve using a conductivity meter of an appropriate electrode material, and performing temperature correction on the measured data, appropriate data management Is confirmed to be possible.

Based on the above knowledge, the present inventors have a simple, inexpensive and highly accurate management method that does not require equipment stoppage of the resistance value of the water resistance type neutral point grounding resistor applied to the transformer equipment of the power distribution equipment. Established. That is, the present invention is as follows.
(1) A resistance value management method for managing the resistance performance of a water resistance type neutral point grounding resistor in an energized state,
Determining a certain period of time after operation and a certain period of time;
The water resistance-type neutral grounding resistor, the initial operation resistance when measured by energizing directly when R _{0 (Ω),} the resistance value R ₁ as measured by energizing directly at a time when the certain _(Omega) , the resistance value R ₂ when measured by energizing directly after said predetermined period T months after timing the certain _(Omega) includes the steps to ensure that satisfies the following formula (1),
| R ₁ −R ₂ | ÷ (R ₀ × T) <0.05 (1)
After T months, the conductivity of the solution collected from the water resistance type neutral grounding resistor is measured, and when measuring the conductivity of the solution, the solution temperature is measured at the same time. and line cormorant step the temperature compensation from the relationship between the temperature and electric conductivity of the sodium carbonate aqueous solution 2 to 50 mg / L obtained,
Comparing the conductivity value of the temperature-corrected and the management value as a criteria,
A resistance value management method for a water resistance type neutral point grounding resistor, characterized by comprising :
(2) When measuring the electrical conductivity of the solution, the electrical conductivity is measured by applying a voltage or current between a pair of electrodes immersed in the collected solution, and titanium or a titanium alloy is used as the electrode material. The resistance value management method according to (1), characterized in that:
(3) When measuring the electrical conductivity of the solution, the electrical conductivity is measured by applying a voltage or current between a pair of electrodes immersed in the collected solution, and the electrode material is mainly composed of Fe, And using an alloy satisfying Cr + Mo / 3 ≧ 25 in Cr and Mo content by mass%, the resistance value management method according to (1) above,
(4) When measuring the electrical conductivity of the solution, the electrical conductivity is measured by applying a voltage or current between a pair of electrodes immersed in the collected solution, and the specific surface area (apparent electrode) is applied to the electrode material. The resistance value management method according to (1) above, wherein a carbon electrode having a ratio of electrode surface area to area) of 200% or less is used.

According to the present invention, disconnect from the grid may be able to manage the resistance value required in conductible state, no measurement timing and frequency constraints, simple, inexpensive, high water resistance-type neutral precision A resistance value management method for a grounding resistor can be provided.

Resistance management method of water resistive neutral grounding resistor according to the present invention, the resistance performance of the water resistive neutral grounding resistors with a resistance value management method for managing in a conductible state, from the resistor The conductivity of the collected solution is measured.

  In the present invention, the internal solution of the water resistance type neutral point grounding resistor is collected from the drain below the neutral contact. When collecting the solution, it is not necessary to disconnect the water resistance type neutral point grounding resistor from the system. The maximum amount of collected solution at one time is about 2 liters. With this amount of sampling, it is possible to continue management without affecting the resistors with a management frequency of several times a year. For the measurement of conductivity, a method of measuring the conductivity by applying a voltage or current between a pair of electrodes immersed in a solution is simple and preferable. The measurement of the conductivity is preferably finished within 2 hours in order to avoid the influence of alteration such as pH fluctuation of the solution to be measured due to absorption of carbon dioxide gas or dissolved oxygen in the atmosphere. In addition, the measurement temperature is preferably a constant temperature selected from any temperature between 5 and 50 ° C. from the viewpoint of the stability of the measuring instrument, and usually the conductivity of the solution expressed in various standards. The reference temperature is 25 ° C.

Resistance management method according to the conductivity of the present invention is to some extent over time after operation, zinc surface is applied to stabilize water-resistive neutral grounding resistors. The resistance value is affected by the inner casing of the water resistance type neutral point grounding resistor in contact with the internal solution and the film on the galvanized surface of the electrode. For this reason, the resistance value is not stable at the beginning of operation when the formation of the film is remarkable, and it is difficult to manage the resistance by the conductivity of the internal solution. As a measure of time, R ₀ (Ω) is the resistance value measured by direct energization during the initial operation of the water resistance type neutral point grounding resistor, and the resistance value measured by direct energization at a certain time. R ₁ (Ω), where R ₂ (Ω) is the resistance value when measured by direct energization after a certain period of T months, and R ₀ is multiplied by time with the absolute value of the difference between R ₁ and R ₂ . The value divided by the value, that is, | R ₁ −R ₂ | / (R ₀ × T) can be used as an index. The resistance of the water resistance type neutral point grounding resistor whose value satisfies the following formula (1) depends on the internal solution.
| R ₁ −R ₂ | ÷ (R ₀ × T) <0.05 (1)

  In the present invention, the electrode material of the conductivity meter used for measuring the conductivity is preferably a material having a stable surface state in the atmosphere and in an internal solution peculiar to water resistance. From the point that the stability of the immersion potential in the internal solution after leaving the electrode in the atmosphere is excellent, the amount of Cr and Mo contained in titanium, titanium alloy, and alloy is Cr + Mo / 3 in mass%. Preferred are metals such as iron-based or nickel-based alloys that are ≧ 25 and carbon. However, since carbon has many porous surfaces depending on its production method, a carbon electrode having a porosity of 200% or less in terms of specific surface area (ratio of electrode surface area to apparent electrode area) is desirable. If the specific surface area is higher than 200%, dust or bubbles may enter the hole during storage or operation, and the characteristics as an electrode may fluctuate, which tends to be undesirable.

  As the conductivity meter using titanium or carbon as an electrode material, a commercially available one can be used, and the price is lower than that of a platinum black electrode conductivity meter.

  In order to manage these electrodes, after measuring the conductivity, it is only necessary to lightly wash the surface with pure water and dry it. Pure water can be procured with commercially available pure water bottles and the required amount is 1 liter or less, so it can be easily handled at the place where the water resistance type neutral point grounding resistor is installed.

  Conductivity measurement data may be obtained for each water resistance type neutral point grounding resistor, but in order to compare with past data or data of multiple facilities, conductivity data corrected to the same temperature is used. Need to ask. As the conductivity meter used for temperature correction, it is desirable to use a conductivity meter that is actually applied in order to improve the measurement accuracy, that is, a titanium electrode is used for measuring the conductivity of the internal solution of the water resistance type neutral grounding resistor. When used, the titanium electrode should also be used for measuring the conductivity of the temperature correction solution. Further, as the correction solution, an internal solution of a target water resistance type neutral point grounding resistor or a 2 to 50 mg / liter sodium carbonate aqueous solution as a simulation solution can be used. When the concentration of the aqueous sodium carbonate solution is less than 2 mg / liter, it is difficult to adjust the solution, and the deviation from the actual solution becomes remarkable. On the other hand, when the concentration of the sodium carbonate aqueous solution exceeds 50 mg / liter, the deviation from the actual solution becomes remarkable, and at the same time, the conductivity is too high, resulting in a large measurement error.

  A temperature correction curve with a simulated solution is also necessary when periodically verifying the measurement accuracy of the conductivity meter. There are a plurality of temperature correction methods for the measured value. For example, [Measured conductivity value × Conductivity value on correction curve (correction temperature) / Conductivity value on correction curve (measurement temperature)] The conductivity can be easily obtained.

  Automatic temperature correction by a commercially available conductivity meter is a correction method corresponding to a chloride-based solution, and therefore cannot be applied because it shows temperature dependence even after correction.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited only to a following example.

Example 1
FIG. 1 shows the result of determining whether or not the conductivity management is applicable from the resistance measurement value of the resistor and the conductivity measurement value of the internal solution at that time when the water resistance type neutral point grounding resistor is released from the system. .

In FIG. 1, the horizontal axis is | R ₁ −R ₂ | ÷ (R ₀ × T), and shows resistance variation with time. The vertical axis shows the applicability of resistance value management by measuring the conductivity of the internal solution of the resistor. That is, from the approximate line of the resistance value in the state where the internal galvanized surface of the resistor represented by | R ₁ −R ₂ | ÷ (R ₀ × T) <0.05 and the conductivity of the solution is stable, Applicable when the difference is 15% or more: ×, Applicable when less than 15%: ○.

In the state of | R ₁ −R ₂ | ÷ (R ₀ × T) ≧ 0.05 shown in FIG. 1, the conductivity of the reference internal solution could not be set. At this time, it was confirmed that the galvanized surface in contact with the solution of the water resistance type neutral point grounding resistor is in the process of being covered with the white product from the metallic luster. On the other hand, the measurement results carried out with the water resistance type neutral point grounding resistor of | R ₁ −R ₂ | ÷ (R ₀ × T) <0.05 according to the present invention are all reference resistances of resistance values. The fluctuation from was within 15%. This is considered to be because the product on the surface of the galvanized plate was stabilized, and the conductivity of the internal solution corresponding to the reference resistance of the water resistance type neutral point grounding resistor could be set. From the above results, the application of the present invention is preferably carried out with a water-resistance type neutral point grounding resistor in which | R ₁ −R ₂ | ÷ (R ₀ × T) <0.05.

(Example 2)
FIGS. 2, 3 and 5 show changes with time of the natural potential when various electrode materials are immersed in the internal solution of the water resistance type neutral grounding resistor.

  A saturated calomel electrode was used as a standard reference electrode. The solution temperature was 25 ° C., and measurement was performed in the same open-air environment as the actual measurement atmosphere. In measuring the conductivity, a weak current was passed between the electrodes, and the conductivity of the solution was measured from the impedance. For this reason, it is necessary that the electrode surface is quickly stabilized or not changed in the internal solution.

  The industrial pure titanium and titanium alloy (Ti-6Al-4V) electrode, which is an example of the present invention, is 10 minutes after being immersed in the internal solution of a water resistance type neutral point grounding resistor from the dry state in the air. It can be seen from FIG. 2 that the potential is stabilized in a short time.

  The carbon electrode (specific surface area 100%), which is an example of the present invention, has a potential in a short time of about 10 minutes even after being immersed in an internal solution of a water resistance type neutral point grounding resistor from a dry state in the air. It can be seen from FIG.

  From the initial measurement value when various carbon electrodes with different specific surface areas were immersed in the internal solution of a water resistance type neutral point grounding resistor and the natural potential was measured, then dried in the air and used again after one month. The change rate of the natural potential is shown in FIG. When the surface of the carbon electrode becomes porous, once it is dried in the air after use, the reproducibility is lost when it is used again. Therefore, the specific surface area of the applied carbon electrode needs to be 200% or less. I understand more. This is presumably because air or dust is clogged in the pores on the surface and the surface state of the electrode changes.

  The SUS329J1 (Fe-25% Cr-4% Ni-3% Mo) electrode, which is an example of the present invention, was immersed in an internal solution of a water resistance type neutral point grounding resistor from a dry state in the atmosphere. FIG. 5 shows that the potential stabilizes in a short time of about 10 minutes. On the other hand, the SUS304 (Fe-18% Cr-8% Ni) electrode, which is a comparative example, is about 60 minutes after being immersed in the internal solution of the water resistance neutral point grounding resistor from the dry state in the atmosphere. It can be seen from FIG. 5 that the potential is not stabilized at the time of. From the results shown in FIG. 5, it is necessary to use an alloy whose main component is Fe and whose Cr and Mo contents in mass% satisfy the following formula: Cr mass% + Mo mass% ÷ 3 ≧ 25. I know that there is. In addition, since this knowledge originates from the stability of the internal solution of the water resistance type neutral point grounding resistor and the electrode surface in the atmosphere, the same result can be expected even in an alloy mainly composed of Ni. .

(Example 3)
A comparative example in which the temperature correction incorporated in a conductivity meter using a commercially available Ti electrode is applied to the internal solution simulation solution (10 mg / L sodium carbonate aqueous solution) of water resistance type neutral point grounding resistors with different water temperatures As shown in FIG. The temperature correction built in a commercially available conductivity meter using a conductivity meter made of Ti electrode basically corresponds to a chloride solution. From the results of FIG. 6, it can be seen that the corrected conductivity is not constant in the temperature correction corresponding to the chloride solution.

  FIG. 7 shows the temperature correction coefficient used in the present invention, which was determined using a 10 mg / L sodium carbonate aqueous solution. By using FIG. 7, the corrected conductivity is a value obtained by [corrected conductivity = measured conductivity × temperature correction coefficient corresponding to measured temperature].

  FIG. 8 shows the measurement results using the temperature correction coefficient of FIG. 7 which is an example of the present invention. The solution is an internal solution simulation solution (10 mg / L sodium carbonate aqueous solution) of a water resistance type neutral point grounding resistor, and the conductivity meter is made of SUS329J1 (Fe-25% Cr-4% Ni-3% Mo) electrode. used. According to the example of the present invention, it can be seen that the conductivity after temperature correction shows a constant value in a wide temperature range. In the field measurement, when the solution temperature is controlled at a constant temperature, the measurement takes time. By performing the temperature correction shown in FIG. 8, the measurement data in a short time or the comparison of the measurement data in other fields can be performed. It becomes easy.

Example 4
FIG. 9 shows the result of comparing the conductivity meter of various electrode materials using the actual solution inside the water resistance type neutral point grounding resistor. Data obtained by performing temperature correction according to the present invention using Ti and a carbon electrode having a specific surface area of 200% or less, which are examples of the present invention, all show good agreement and may show a constant value with respect to temperature after correction. Recognize. On the other hand, the data corrected by using SUS304 (Fe-18% Cr-8% Ni) electrode shows a constant value with respect to the temperature change, but shows different conductivity from other electrodes. I understand.

(Example 5)
An example in which the management method according to the present invention is applied to the management of a water resistance type neutral point grounding resistor is shown in FIG. The vertical axis represents the conductivity of the internal solution collected from each water resistor measured using a Ti electrode conductivity meter and a carbon electrode conductivity meter within the scope of the present invention. The horizontal axis shows the actually measured resistance value of each water resistor after time when the reference resistance value set for each water resistor is 100. Any of the water resistors to be measured satisfies the formula (1) of the present invention. A linear correlation is confirmed between the electrical conductivity of the internal solution obtained by the present invention and the resistance value of the water resistor, and it is understood that the resistance management of the water resistor is possible by this method.

It is a figure which shows the applicable range of resistance management by the electrical conductivity measurement of the internal solution of a water resistance type neutral point grounding resistor. It is a figure which shows the time-dependent change (example of this invention) of the immersion potential in the internal solution of the electrode made from Ti and Ti alloy. It is a figure which shows the time-dependent change (example of this invention) of the immersion potential in the internal solution of a carbon electrode. It is a figure which shows the measurement error after 1-month dry storage of a carbon electrode conductivity meter. It is a figure which shows the time-dependent change of the immersion potential in the internal solution of a stainless steel electrode. It is a figure which shows the temperature correction (comparative example) by the commercially available Ti electrode conductivity meter. It is a figure which shows the temperature correction coefficient (example of this invention) in each temperature based on sodium carbonate aqueous solution. It is a figure which shows the electrical conductivity (example of this invention) before and behind the temperature correction based on sodium carbonate aqueous solution. It is a figure which shows the comparison (before and after temperature correction by FIG. 7) of the conductivity value by the electrode type of a conductivity meter. It is a figure which shows the resistance value management example of the water resistance type neutral point grounding resistor by this invention.

Claims (4)

A resistance value management method for managing the resistance performance of a water resistance type neutral point grounding resistor in an energized state,
Determining a certain period of time after operation and a certain period of time;
The water resistance-type neutral grounding resistor, the initial operation resistance when measured by energizing directly when R _{0 (Ω),} the resistance value R ₁ as measured by energizing directly at a time when the certain _(Omega) , the resistance value R ₂ when measured by energizing directly after said predetermined period T months after timing the certain _(Omega) includes the steps to ensure that satisfies the following formula (1),
| R ₁ −R ₂ | ÷ (R ₀ × T) <0.05 (1)
After T months, the conductivity of the solution collected from the water resistance type neutral grounding resistor is measured, and when measuring the conductivity of the solution, the solution temperature is measured at the same time. and line cormorant step the temperature compensation from the relationship between the temperature and electric conductivity of the sodium carbonate aqueous solution 2 to 50 mg / L obtained,
Comparing the conductivity value of the temperature-corrected and the management value as a criteria,
The resistance value management method of the water resistance type neutral point grounding resistor characterized by including this.   When measuring the conductivity of the solution, applying a voltage or current between a pair of electrodes immersed in the collected solution, measuring the conductivity, and using titanium or a titanium alloy as the electrode material The resistance value management method according to claim 1, wherein:   When measuring the electrical conductivity of the solution, the electrical conductivity is measured by applying a voltage or current between a pair of electrodes immersed in the collected solution, and the electrode material is mainly composed of Fe, and the mass%. 2. The resistance value management method according to claim 1, wherein an alloy satisfying Cr + Mo / 3 ≧ 25 is used. When measuring the electrical conductivity of the solution, a voltage or current is applied between a pair of electrodes immersed in the collected solution to measure the electrical conductivity, and the specific surface area of the electrode material (the electrode relative to the apparent electrode area) is measured. The resistance value management method according to claim 1, wherein a carbon electrode having a surface area ratio) of 200% or less is used.

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