JPH07146313A - Capacitor voltage divider - Google Patents

Abstract

PURPOSE:To obtain a capacitor voltage divider which is mounted on gas insulated electronic equipment and the voltage detecting accuracy of which does not drop even when a temperature change occurs by improving the voltage detecting accuracy of the divider. CONSTITUTION:A capacitor voltage divider is constituted so that its capacitance can be accurately recognized from a design stage by providing an auxiliary electrode 15 at the end section of a main electrode 13 concentrically installed with an inner conductor 2 near the internal surface of a metallic container 1 and preventing the expansion of an electric field at the end section of the electrode 13. In addition, the voltage divider is constituted so that materials having desirable coefficients of linear expansion can be selected for the conductor 2 and electrode 13 by defining the relation which does not allow the capacitance of the voltage divider to change between the coefficients of linear expansion of the materials used for the conductor 2 and electrode 13 in corresponding to the diametric ratios of the conductor 2 and electrode 13 so that the capacitance of the voltage divider cannot change even when a temperature change occurs. Therefore, detecting voltage adjusting work and calibrating work can be easily performed on the voltage divider after assembly and the voltage detecting accuracy of the voltage divider does not drop even when the temperature change occurs, since the capacitance of the voltage divider can be accurately recognized from a design stage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitor voltage divider of a voltage detecting device which is installed in a gas insulated electric device installed in a substation or the like and detects a voltage applied to the device.

[0002]

2. Description of the Related Art As a voltage detecting means for a gas-insulated electric device, an inner conductor is induced near an inner peripheral surface of a metal container housed in the center thereof by an electrode mounted electrically insulated from the metal container. A method using a so-called capacitor voltage divider that outputs a secondary voltage proportional to the induced voltage is well known. FIG. 9 is a sectional view showing an example of a conventional capacitor voltage divider mounted on a gas-insulated electric device. In the figure, 1 is a metal container whose inside is filled with an insulating gas, 2 is an internal conductor housed in the center of the metal container, and 3 is a main electrode mounted in the vicinity of the inner peripheral surface of the metal container 1. is there. A mounting seat 1a for mounting the main electrode 3 is fixed to a predetermined position on the inner peripheral surface of the metal container 1, and a mounting metal 3a for mounting on the metal container 1 is provided on the outer periphery of the main electrode 3. Reference numeral 4 is an insulating ring for mounting the main electrode 3 while electrically insulating it from the metal container 1. Reference numeral 6 is an insulating terminal for leading the voltage induced in the main electrode 3 to the outside, and 7 is a connecting lead for electrically connecting the main electrode 3 and the insulating terminal 6. The main electrode 3 has a mounting bracket 3a and a mounting seat 1a fixed to the metal container 1.
The insulating ring 4 is inserted between the main electrode 3 and the insulating terminal 6, and the main electrode 3 and the insulating terminal 6 are connected to each other by a connecting lead 7
Are electrically connected to each other, and the induced voltage is led to the outside.

In the capacitor voltage divider thus constructed, the main capacitance C ₁ between the inner conductor 2 and the main electrode 3 and the main electrode ground capacitance C ₂₁ between the main electrode 3 and the metal container 1 are set. Is in a serial state, and the voltage V ₀ applied between the inner conductor 2 and the metal container 1 is divided by the main electrostatic capacitance C ₁ and the main electrode ground electrostatic capacitance C ₂₁ to be the main voltage. The divided voltage V _t shown in Expression 1 is induced in the electrode 3.

[Equation 1] Normally, the divided voltage according to the formula 1 is too high for measurement or control, so that the voltage induced in the main electrode 3 is adjusted to an appropriate voltage value by an external adjusting capacitor 10 and the main electrode ground capacitance C _21. It is connected in parallel with and adjusted to an appropriate voltage value for use. When the electrostatic capacitance of the adjusting capacitor 10 is C ₂₂ , the electrostatic capacitance C ₂ of the voltage dividing tap becomes C ₂₁ + C _{22 and the} divided voltage V _t of the voltage dividing tap is given by the formula 2.

[Equation 2] The equivalent circuit of the capacitor voltage divider configured in this way is
As shown in 10.

The capacitor voltage divider constructed as described above has a small electrostatic capacity and does not take a secondary load on the output side. Therefore, the detected voltage is converted into a digital signal or an optical signal and transmitted, and then the control panel or the like is used. A method of converting to a voltage value is adopted. The accuracy required for the detection voltage used for measurement or control in substations is usually required to be 1.0 class, and sometimes 0.5 class. In such cases,
The required accuracy of the capacitor voltage divider is 0.2% or less in consideration of the accuracy of the signal conversion means.

As described above, the capacitor voltage divider has a main capacitance C ₁ between the inner conductor 2 and the main electrode 3, a main electrode ground capacitance C ₂₁ between the main electrode 3 and the metal container 1, and a main electrode. Three
The voltage dividing tap capacitance C ₂ is configured by the electrostatic capacitance C ₂₂ of the adjusting capacitor 10 that adjusts the divided voltage of V to an appropriate value, and the divided voltage V _t accurately grasps the main electrostatic capacitance C _1. , The capacitance C ₂₂ of the adjusting capacitor 10 is selected to set the voltage dividing tap capacitance C ₂ . Since the voltage dividing tap capacitance C _{2 in} which the adjusting capacitor 10 is connected in parallel is large and its value can be grasped with high precision, the voltage detection precision of the capacitor voltage divider depends on the precision of the main capacitance. When there is a temperature rise in the inner conductor 2 and the main electrode 3 while the equipment is operating, the dimensions of the inner conductor 2 and the main electrode 3 change due to thermal expansion, and the main capacitance C ₁ and the voltage dividing tap capacitance C ₂ change and detected. It is also necessary to consider that the voltage changes.

The main capacitance C ₁ of the capacitor voltage divider shown in FIG. 9 can be obtained by the formula 3 of the calculation formula of the capacitance of the concentric cylindrical capacitor.

[Equation 3] ε ₀ : Dielectric constant of intervening insulator L: Length of main electrode D ₁ : Diameter of inner conductor D ₂ : Inner diameter of main electrode Equation 3 is an equation for obtaining the capacitance of an infinite cylindrical capacitor, and it has a finite length. In this case, since the electric field spreads at the end of the main electrode 3, the actual electrostatic capacitance becomes a value smaller than the calculated main electrostatic capacitance. End of the electric field of the spread relationship or around the metallic container 1 in the shape of the diameter D ₂ of diameter D ₁ and the main electrode 3 of the inner conductor 2 of the main electrode 3, for example, because the changes by such flexion portion is short, accurate It is difficult to grasp the electrostatic capacity, and the electrostatic capacity is only a guide at the time of design.At the time of manufacturing, the voltage is actually applied and the detection voltage is measured to set the adjustment capacitor 10 to an appropriate value. The detection voltage is adjusted by the method described above.

In an actual capacitor voltage divider, a change in temperature of a mounted portion causes a change in dimensions of the internal conductor 2 and the main electrode 3 to change a main capacitance C _{1 and} an error in a detection voltage. In gas-insulated electrical equipment, the inner conductor 2
The generated heat is transmitted to the portion of the metal container 1 by the convection of the insulating gas filled in the surroundings, and is radiated from the surface of the metal container 2 to the outside air. Therefore, the temperature distribution of the gas-insulated electric equipment is highest in the portion of the inner conductor 2, the temperature gradient of the filling insulating gas, the temperature gradient of the portion of the metal container 2, the temperature gradient of the boundary transmitted from the outer surface to the outside air, etc. Becomes The main electrode 3 of the capacitor voltage divider is mounted close to the inner surface of the metal container 2, and the temperature of the main electrode 3 is in the filled insulating gas. The temperature difference between the outer wall and the outer wall is small, and it is in the middle of the temperature of the inner conductor 2 and the inner wall of the metal container 1.
Is estimated to be close to the temperature of the insulating gas, and in actual gas-insulated electrical equipment there is a difference depending on the rated voltage and rated current, but it is estimated to be approximately 70 to 80% of the temperature rise value of the inner conductor 2.

The temperature distribution during operation of the capacitor voltage divider is as described above, and the electrostatic capacitance C _{1 (2)} during operation changes according to the equation (4).

[Equation 4] α: linear expansion coefficient of inner conductor material β: linear expansion coefficient of main electrode material t ₁ : temperature rise value of inner conductor t ₂ : temperature rise value of main electrode D ₁ , D ₂ , ε ₀ , L Represents the same part as time.

Now, assuming that the materials of the inner conductor 2 and the main electrode 3 are the same, and α = β, equation 4 becomes equation 5.

[Equation 5] Since ln (1 + αt ₂ ) and ln (1 + αt ₁ ) in formula 5 are sufficiently smaller than _{1 in} αt ₂ and αt ₁ , formula 6 and formula 7
An approximate value can be calculated by using. _{ln (1 + αt 2) ≒} αt 2 ................................................... formula _{6 ln (1 + αt 1)} ≒ αt 1 ............................................. Equation 7 Equation 6 is substituted into Equation 5 to obtain Equation 8.

[Equation 6] Furthermore, α (t ₂ −t ₁ ) of Equation 8 is ln (D ₂ / D ₁ ).
Since it is sufficiently small with respect to

[Equation 7] Expanding Equation 9, the term of α squared is sufficiently smaller than the other terms, so if you set it to 0, Equation 10 is obtained.

[Equation 8] The first term of the equation 9 is the same as that of the equation 3, and the second term becomes an increase of the main capacitance, which is related to the accuracy of the detection voltage.

[0010]

The conventional capacitor voltage divider is constructed as described above, and the electric field spreads at the end of the main electrode between the inner conductor and the main electrode, and the actual main capacitance is increased. Is smaller than the value calculated by Equation 3, and the degree changes depending on the distance between the inner conductor and the main electrode, so it is difficult to grasp the accurate value of the main capacitance from the time of design. However, a complicated adjustment work of applying a voltage to adjust the detection voltage after assembling the product is required. Further, there is a problem that the main capacitance changes due to the temperature rise of the main body device in which the capacitor voltage divider is mounted, and the accuracy of the detection voltage deteriorates.

The present invention has been made in order to solve the above problems, and provides a capacitor voltage divider capable of accurately ascertaining a main electrostatic capacity from the time of designing, and further, during operation of the main equipment. It is also an object of the present invention to provide a capacitor voltage divider in which the change in the main capacitance is small even if the temperature rises and a desired voltage detection accuracy is obtained in the operating temperature range.

[0012]

The capacitor voltage divider according to claim 1 of the present invention has the same inner diameter as the main electrode at both ends of the main electrode mounted near the inner wall of the metal container, and one end of the main There is a flange that connects with the electrodes, and the other end has a structure in which a pair of auxiliary electrodes formed in a shape that expands toward the outer periphery with a predetermined radius of curvature in order to mitigate the electric field concentration is insulated and connected to the main electrode. Is electrically connected to the metal container.

The capacitor voltage divider according to claim 2 of the present invention is a metal fitting for mounting the main electrode by directly fixing one of a pair of auxiliary electrodes connected to both ends of the main electrode to the inner wall of the metal container. It also serves as a dual purpose and omits a metal fitting for mounting the main electrode.

In the capacitor voltage divider according to claim 3 of the present invention, the main electrode has a cylindrical shape with a slit formed in one axial direction in the circumference, and the inner diameter is the same as the inner diameter of the main electrode. The one end has a stepped shape in which the main electrode is fitted, and the other end is fixed to the inner peripheral surface of the metal container with a predetermined interval facing each other with a pair of auxiliary electrodes that spread toward the wall of the metal container. A cylindrical main electrode is electrically insulated and attached to the inner circumference of the auxiliary electrode.

In the capacitor voltage divider according to claim 4 of the present invention, the linear expansion coefficient of the inner conductor is smaller than the value obtained by dividing the allowable rate of change of the main capacitance by the maximum temperature rise value of the inner conductor. The material of the main electrode is a material having a linear expansion coefficient close to a value obtained by dividing the product of the linear expansion coefficient of the inner conductor and the maximum temperature increase value by the maximum temperature increase value assumed for the main electrode.

According to a fifth aspect of the present invention, in the capacitor voltage divider, the inner conductor material is copper and the main electrode material is aluminum or an aluminum alloy containing aluminum as a main component.

In the capacitor voltage divider according to the sixth aspect of the present invention, the electrode portion is formed with a main electrode at a predetermined position on the inner peripheral surface of the electrode body made of a resin material, and a predetermined space is provided between the main electrode and an end portion of the main electrode. It is formed by adhering a conductive film to be an auxiliary electrode to the outer peripheral surface from the position where it is placed to the end.

[0018]

In the capacitor voltage divider according to the first aspect of the present invention, the auxiliary electrode having the same inner diameter as the inner diameter of the main electrode is insulated and connected to both ends of the main electrode mounted near the inner wall of the metal container. As a result, the spread of the electric field at the end of the main electrode is eliminated, and the main capacitance between the main electrode and the internal conductor can be accurately grasped at the time of design.

In the capacitor voltage divider according to claim 2 of the present invention, one of the pair of auxiliary electrodes connected to both ends of the main electrode is directly fixed to the inner wall of the metal container so that the main electrode is mounted. The number of parts required for manufacturing is small, and the manufacturing cost can be reduced.

In the capacitor voltage divider according to claim 3 of the present invention, the main electrode has a cylindrical shape, and one portion of the circumference is
Since the slits are provided in the axial direction, the pair of auxiliary electrodes are directly fixed to the metal container, and the main electrode is insulated and mounted between the pair of auxiliary electrodes, so the number of parts for mounting the main electrode is small. In addition to easy mounting, the space for mounting the main electrode can be reduced.

In the capacitor voltage divider according to a fourth aspect of the present invention, the inner conductor has a permissible rate of change of the main capacitance between the inner conductor and the main electrode as a linear expansion coefficient of the inner conductor and a maximum temperature rise value. The material of the main electrode has a coefficient of linear expansion smaller than the value obtained by dividing the product by the product of the coefficient of linear expansion of the internal conductor and the maximum temperature rise of the internal conductor. Since the coefficient of linear expansion is close to the value divided by the value, the main capacitance can be within the range of the allowable rate of change even if the temperature rises.

In the capacitor voltage divider according to the fifth aspect of the present invention, since the internal conductor material is copper and the material of the main electrode is aluminum or an aluminum alloy containing aluminum as a main component, the temperature rise in the internal conductor and the main electrode. However, the main capacitance can still be a capacitor voltage divider that is within the acceptable range.

In the capacitor voltage divider according to claim 6 of the present invention, the main electrode and the main electrode are formed at predetermined positions on the inner circumference of the electrode body in which the electrode portions of the main electrode and the auxiliary electrode are formed of a resin material in a predetermined shape. Since the conductive film to be the auxiliary electrode is attached to the end of the inner peripheral surface from a position spaced apart from the extreme, the main capacitance can be accurately grasped from the beginning of designing, and the electrode part is mounted. Therefore, a capacitor voltage divider having a small number of parts can be obtained.

[0024]

【Example】

Example 1. A first embodiment of the present invention will be described below with reference to FIG. In FIG. 1, reference numerals 1, 2, 4, 6, and 7 have the same or the same functions as those of the conventional example shown in FIG. Reference numeral 13 denotes a main electrode, which is provided with a mounting metal 13a for mounting the metal container 1 on the outer peripheral portion, and flanges 13b to which the following auxiliary electrodes are connected at both ends. Reference numeral 15 is a pair of auxiliary electrodes connected to both ends of the main electrode 13, the inner diameter is the same as the inner diameter of the main electrode 13, and one end is provided with a flange 15a for connecting with the main electrode 13, The end is formed in a shape that spreads toward the outer periphery with a predetermined radius of curvature. Reference numeral 14 is an insulating ring for insulating between the main electrode 13 and the auxiliary electrode 15. Reference numeral 17 is a connecting lead for keeping the auxiliary electrode 15 at the same potential as the metal container 1. The capacitor voltage divider is provided with a pair of auxiliary electrodes 15 at both ends of the main electrode 13 to electrically insulate them by interposing insulating rings 14, and connected with bolts 18 to form an electrode portion, which is provided on the outer peripheral portion of the main electrode 13. Mounting money
An insulating ring 4 is inserted between 13a and a mounting seat 1a fixed to the inner peripheral surface of the metal container 1 so as to be electrically insulated and mounted, and a main electrode 13 and an insulating terminal 6 are connected by a connecting lead 7. The pair of auxiliary electrodes 15 are connected to the metal container 1 by the connection leads 17, and an adjusting capacitor (not shown) for adjusting the detection voltage value is connected between the insulating terminal 6 and the metal container 1. To be done.

In the capacitor voltage divider thus constructed, the main capacitance C between the main electrode 13 and the inner conductor 2 is
_1, the main electrode 13 and the partial pressure tap capacitance C ₂ of the sum of the capacitance C ₂₂ of the adjusting capacitor capacitance C ₂₁ between the metallic container 1 becomes series, same as the conventional example The equivalent circuit shown in FIG. 10 is obtained, and the divided voltage V _t has the value shown in Expression 2. This divided voltage V _t is usually suitable for signal conversion or measurement.
Adjusted to 100 V or 100 / √3 V, auxiliary electrode
Reference numeral 15 is connected to the metal container 1 and is divided from the main electrode 13 by a divided voltage V _t.
Although there is a potential difference of (100 V or 100 / √3 V), the voltage of the inner conductor 2 is several tens to several hundreds KV, which is sufficiently small, and the electric field distribution in the connecting portion between the main electrode 13 and the auxiliary electrode 15 is ,
It is not affected by the divided voltage V _t , the spread of the electric field at the end of the main electrode 15 is eliminated, and the main capacitance C ₁ between the inner conductor 2 and the main electrode 13 is calculated from the initial designing according to the formula 3 above. It can be grasped accurately.

The accuracy (error class) of the detection voltage required for the capacitor voltage divider depends on its application, but is 1.0 for voltage measurement or control of a power transmission system which is usually used.
Class is required. When the error class is required to be 1.0 class as a voltage detection device, the capacitor voltage divider according to the present invention has a small electrostatic capacity and cannot take a secondary load, so only the voltage value is detected from the capacitor voltage divider. Then, the detected value is converted into a digital optical signal or the like and transmitted, and is inversely converted at the receiving side such as a control panel and used for measurement and control. When the error class at the output end is required to be class 1.0 in such a system, the errors of the signal converter and the inverse converter are integrated, so 0.1% to 0.2% is applied to the capacitor voltage divider.
Degree is required.

When a strict accuracy is required for the detection voltage as described above, when the capacitor voltage divider is constructed without using the auxiliary electrode as in the conventional example, the main capacitance is only a standard at the design stage. Since it is not possible to grasp, it is necessary to prepare many types of adjustment capacitors, actually apply voltage after assembly of the product, measure the capacitance, and replace the adjustment capacitors of various values to perform adjustment, which is complicated and requires a long time adjustment. become Although this first embodiment, since the accessory auxiliary electrode 15 to the electrode portion, diverging portion of the electric field that inhibits the calculation accuracy of the capacitance C ₁ is not related to the main capacitance C ₁ auxiliary Electrode 15
, The electric field at the main electrode 13 becomes almost equal, and the main capacitance C ₁ can be grasped accurately from the beginning of design, so there are few types of adjustment capacitors to prepare and adjustment of the detection voltage after assembly. The effect of simplifying the work is obtained. Further, by using the auxiliary electrode 15, even when the capacitor voltage divider is mounted near the bent portion of the metal container, the disturbance of the electric field due to the bending does not affect the portion of the main electrode 13, so that the metal container 1 The accuracy of the main capacitance C ₁ can be ensured even when it is attached to the bent portion.

Example 2. Next, a second embodiment will be described with reference to FIG. This example is basically the same as Example 1 described above except that one of the pair of auxiliary electrodes is
This is also used as a fitting for mounting the main electrode 13 on the metal container 1. 2, 1, 2, 6, 7, 13, 13, 14, 15 and 17 have the same or the same functions as those of FIG. 9 showing the conventional example and FIG. 1 showing the first embodiment, and the description thereof will be omitted. Reference numeral 5 has an inner diameter that is the same as that of the main electrode 13, and connects the main electrode 13 to the auxiliary electrode formed so that the open end at one end expands toward the outer periphery with a predetermined radius of curvature and the opposite side of the open end of the auxiliary electrode. The flange 5a is provided toward the outer circumference, and the outer circumference of the flange 5a is a fixed auxiliary electrode fixed to the metal container 1. The electrode part is connected to the fixed auxiliary electrode 5 by connecting one end of the main electrode 13 with an insulating ring 14 and electrically insulating with a bolt 18 and inserting the insulating ring 14 at the other end of the main electrode 13 to electrically connect. The auxiliary electrode 15 is connected to the insulating terminal 6 by the connecting lead 7 and is electrically insulated from the auxiliary electrode 15 by the bolt 18.
Are connected to the metal container 1 by connection leads 17.
An adjustment capacitor (not shown) is connected to the insulating terminal 6 to adjust the divided voltage.

In the capacitor voltage divider thus constructed, one of the pair of auxiliary electrodes also serves as the metal fitting for mounting the main electrode 13, so that the number of parts to be mounted is reduced, and in addition to the same effect as the first embodiment. As a result, the effect of facilitating the assembly work of the electrode portion can be obtained.

Example 3. Further, a third embodiment will be described with reference to FIG. Reference numeral 23 in FIG. 3 is a main electrode which is formed into a cylindrical shape with a predetermined length and has an axial notch at one position on the circumference, 25 is a pair of auxiliary electrodes, and the inner diameter is the same as the inner diameter of the main electrode 23. , The open end of each end is formed to spread toward the inner peripheral surface of the metal container 1 with a predetermined radius of curvature, and the opposite end is formed in a stepped shape to which the main electrode 23 can be attached,
The metal container 1 is fixed to the metal container 1 with a predetermined gap so that the open end is on the outside. Reference numeral 24 is an insulating ring for electrically insulating the auxiliary electrode 25 and the main electrode 23. The outer shape of the main electrode 23 is made small by overlapping the notches as shown by the one-dot chain line in FIG. 3, and an insulating ring 24 is inserted at the end between the auxiliary electrode 25 and a pair of auxiliary electrodes 25. Then, the electrode portion is formed by inserting it between the two and expanding the superposition of the notches to make it have a predetermined diameter. The main electrode 23 and the insulating terminal 6 are electrically connected by the connection lead 7.

When the capacitor voltage divider is configured as described above, the number of parts of the electrode portion is reduced, and in addition to the effect that the main capacitance can be accurately grasped from the design stage as in the first and second embodiments, The mounting space for the electrode 23 is reduced, the diameter of the metal container 1 can be reduced, and the assembling work is simplified.

Example 4. Next, a fourth embodiment will be described. The fourth embodiment corresponds to the fact that the main capacitance changes due to the temperature rise during the operation of the capacitor voltage divider, and the error in the detected voltage increases, and refer to FIGS. 1, 2 and 3. Explain. Main electrode shown in FIGS. 1, 2 and 3
When the material of 13 or 23 is the same as the material of the inner conductor 2, if the temperature rises during operation, the main capacitance C ₁ increases as shown in the above formula 10. ₁
The error of the detection voltage becomes larger as is increased.

When the inner conductor 2 and the main electrode 13 or 23 are made of the same material, the main capacitance C ₁ changes according to the above equation 5 due to temperature rise. The change of the main electrostatic capacitance C _{1 (2)} due to the temperature change when the materials of the inner conductor 2 and the main electrode 13 or 23 are different from each other is changed by the above-mentioned formula 4. Similar to the case where Expression 4 is rearranged into Expression 9 and Expression 10, an approximate expression is derived as Expression 11.

[Equation 9] The first term of the equation 11 is the same as the equation 3 for obtaining the main capacitance C ₁ when there is no temperature rise, and the second term is the increase of the main capacitance due to the temperature rise.

If the amount of increase in the main capacitance when the temperature rises can be eliminated, the voltage detection accuracy can be improved. The condition can be set by setting the second term of Expression 11 to zero. When the condition is obtained, it is as shown in Expressions 12 and 13.

[Equation 10]

[Equation 11] T ₂ / t ₁ is the value of about 0.7 to 0.8 in ordinary capacitor divider is the ratio of the temperature rise value of the main electrode 13 or 23 with respect to the temperature rise value of the internal conductor 2 in Formula 13.
When t ₂ / t ₁ = 0.7, the main capacitance C ₁ does not change even if the temperature changes, and the diameter ratio D ₂ / D _{1 of the} inner conductor 2 and the main electrode 13 or 23 and the ratio of the respective linear expansion coefficients. The relationship with β / α is the curve of S = 0 shown by the dotted line in FIG. From this curve, the diameter ratio D of the inner conductor 2 and the main electrode 13 or 23
_A capacitor whose main capacitance C ₁ does not change even if the temperature changes due to a load current by selecting each material so that the ratio β / α of each linear expansion coefficient is satisfied corresponding to ₂ / D _1. You can get a voltage divider.

However, since the actual temperature of the capacitor voltage divider changes depending on the operating conditions and changes in the ambient temperature, the linear expansion coefficient of the material of the inner conductor 2 and the main electrode 13 or 23 that satisfies the condition of Equation 15 is satisfied. Even if you choose one,
It is impossible to make the amount of change in the main capacitance C ₁ zero. Therefore, a condition for satisfying the change amount of the main capacitance C ₁ allowed for the capacitor voltage divider in the operating temperature range is obtained. In the voltage detecting means configured by using this kind of capacitor voltage divider, the allowable change amount of the main capacitance is 0.
About 1 to 0.2% is required. The amount of change in the main electrostatic capacitance C ₁ of the capacitor voltage divider is the second term of the equation 11, and the allowable change rate S is given by the equation 14 when the allowable change rate is S.

[Equation 12] If the ratio of the linear expansion coefficients α and β of the materials of the inner conductor 2 and the main electrode 13 or 23 is obtained from the equation 14, the equation 15 is obtained.

[Equation 13] In formula 15, the diameter ratio D ₂ / D ₁ between the inner conductor 2 and the main electrode 13 or 23 is selected by selecting α that satisfies the condition of S / αt ₁ = _1.
The material of the main electrode 13 or 23 can be selected regardless of
The required linear expansion coefficient β of the material can be obtained.

Further, by making the amount of change of the main capacitance C ₁ of the second term of the formula 11 due to temperature rise smaller than the allowable change rate S, the condition of the following formula 16 is satisfied so that the value is not more than the allowable value. You can

[Equation 14] The condition of the linear expansion coefficient β required for the material of the main electrode 13 or 23 is derived from the formula 16 to obtain the formula 17.

[Equation 15] Therefore, the relation between the allowable variation S of the main capacitance C ₁ and the product αt ₁ of the linear expansion coefficient α of the internal conductor 2 and the maximum temperature rise value t ₁ satisfies the condition of S / αt ₁ > 1. By selecting the material of the conductor 2, it is not necessary to increase the linear expansion coefficient β of the main electrode 13 or 23 even if the diameter ratio D ₂ / D ₁ between the inner conductor 2 and the main electrode 13 or 23 increases. S / αt ₁ > 1
Select the material of the inner conductor 2 that satisfies the conditions
By selecting the material of the main electrode 13 or 23 so that the material of 13 or 23 satisfies the condition of Expression 17, regardless of the value of the diameter ratio D ₂ / D ₁ of the inner conductor 2 and the main electrode 13 or 23. It is possible to obtain the capacitor voltage divider in which the allowable change amount S of the main capacitance C _{1 due to} the temperature rise of the main capacitance C ₁ is equal to or less than the allowable change amount S.

In equation 14, t ₂ / t ₁ is the ratio of the temperature rise value of the main electrode 13 or 23 to the temperature rise value of the inner conductor 2.
The temperature distribution of the portion of the gas-insulated electrical equipment where the capacitor voltage divider is mounted is such that the heat generated by the load current in the inner conductor 2 is applied to the inner surface of the metal container 1 by convection of the insulating gas filled in the metal container 1. It moves, is transmitted through the wall of the metal container 1, and is radiated to the outside air from the surface of the metal container 1. The temperature of each part of the heat transfer path is the highest point of the inner conductor 2 and Since the temperature gradient is divided in proportion to the thermal resistance of the internal conductor 2 and the thermal resistance of each part does not change even if the temperature of the inner conductor 2 changes, the temperature rise value of each part is It is a value obtained by multiplying the divided division ratio.

The main electrode 13 or 23 of the capacitor voltage divider is mounted in a filled insulating gas, the temperature of which is equal to the temperature of the filled insulating gas temperature near the inner surface of the metal container 1. The diameter D ₁ of the inner conductor 2 of this type of capacitor voltage divider is to be increased according to the voltage class in order to average the internal electric field even if the diameter required is smaller than the rated current. The diameter ratio D ₂ / D _{1 to} the main electrode 13 or 23 does not change greatly depending on the voltage class and is set in a narrow range, and the range of D ₂ / D ₁ is approximately 1.4 to 2.0. Therefore, it may be considered that they are substantially similar in heat distribution, and that t ₂ / t ₁ is almost constant regardless of the voltage class. In the actual temperature test of the gas-insulated electric equipment, the ratio between the temperature rise value of the inner conductor 2 and the surface temperature rise value of the metal container 1 is in the range of 0.6 to 0.7, although there is a slight difference due to the difference in configuration. Estimating the temperature of the main electrode 13 or 23 from the thermal resistance ratio, t ₂ / t ₁ = 0.
It is in the range of 7 to 0.8.

The temperature at the time of manufacturing the capacitor voltage divider can be considered to be almost in the range of 15 to 30 ° C. although it varies depending on the season, and the capacitor voltage divider manufactured at the temperature in this range is a standard (JEC-181). ) Maximum ambient temperature
Used at 40 ℃, the maximum temperature of the inner conductor at that time is 105
The temperature rise value t ₁ is 65 ° C. Assuming that the temperature when the capacitor voltage divider is manufactured is 15 ℃ and the maximum temperature is 40 ℃, the worst condition is that the temperature of the inner conductor 2 is 105 ℃ when the maximum temperature is 40 ℃.
90 ° C is set as the maximum temperature rise value of the inner conductor 2, and the ratio t ₂ / t ₁ between the temperature rise value of the main electrode 13 or 23 and the temperature rise value of the inner conductor 2 is 0.7 to 0.8. By selecting a material having a linear expansion coefficient required for the inner conductor 2 and the main electrode 13 or 23 as 0.7, which falls within the allowable range of the main capacitance C ₁ with respect to the temperature change during use. be able to.

The allowable change rate S of the main capacitance C ₁ required for the capacitor voltage divider is 0.1 to 0.2% as described above.
This is a degree, and the design target value is S = 0.0015 (0.15%) and is considered. The setting conditions examined above are re-described as follows. S = 0.0015, t ₁ = 90 ° C., t ₂ / t ₁ = 0.7 The condition under which Eq. 15 is no longer related to the diameter ratio D ₂ / D ₁ of the inner conductor 2 and the main electrode 13 or 23, S = α
The value of α that satisfies t ₁ is as follows. α = S / t ₁ = 0.0015 / 90 = 16.7 × 10 ^-6 Substituting α into Equation 15 and calculating the ratio β / α of the linear expansion coefficients of the internal conductor 2 and the main electrode 13 or 23 gives 1.429. When β is calculated from this, it becomes 23.8 × 10 ⁻⁶ , and the linear expansion coefficient of each of the inner conductor 2 and the main electrode 13 or 23 is α = 1.
By setting 6.7 × 10 ⁻⁶ and β = 23.8 × 10 ⁻⁶ , the permissible rate of change of the main capacitance C ₁ regardless of the diameter under the above temperature conditions t ₁ = 90 ° C. and t ₂ / t ₁ = 0.7. S = 0.0015 (0.
15%).

However, few materials are suitable for the linear expansion coefficients α and β of the internal conductor 2 and the main electrode 13 or 23 thus determined, and in reality, materials having linear expansion coefficients close to these are used. The amount of change in the main capacitance C ₁ of the actual product is determined by the linear expansion coefficient of the selected material, and the applied amount can be applied under the condition that the obtained amount of change is within the allowable change rate S. The material closest to α = 16.7 × 10 ^-6 and β = 23.8 × 10 ^-6 obtained above is copper {linear expansion coefficient 16.5 × 10 ^-6 (at20
℃)}, aluminum {coefficient of linear expansion 23.8 × 10 ^-6 (at20
℃)}. The material of the inner conductor 2 is copper, the main electrode 13 or
As the material of 23, aluminum or an aluminum alloy containing aluminum as a main component can be selected. In this case, the diameter ratio of the inner conductor 2 to the diameter of the main electrode 13 or 23 D ₂ / D ₁
FIG. 5 shows the rate of change of the main capacitance C ₁ corresponding to the above when the temperature of the central conductor 2 is 90 ° C., 80 ° C. and 70 ° C. Figure 5
As shown in, the allowable change rate S is 0.00 at the maximum temperature of 90 ℃.
It is 15 (0.15%) or less, and the rate of change decreases as the temperature decreases, and the main capacitance C ₁ can be kept within the allowable rate of change S in the temperature range during operation.

Example 5. Next, a fifth embodiment will be described. In the first to fourth embodiments, the case where the main electrode and the auxiliary electrode are made of a metal material is shown, but in the fifth embodiment, the main electrode and the auxiliary electrode are integrally formed with a resin material to form the electrode portion. The embodiment is shown in FIGS. In the figure, reference numeral 30 denotes an electrode portion, and a main electrode film 32 is formed at a predetermined position on an inner peripheral surface of an electrode body 31 formed by molding a resin material such as an epoxy casting resin into a predetermined shape, and an end portion of the main electrode film 32 is formed. A conductive film is attached so as to form an auxiliary electrode film 33 on the outer peripheral surface from a position separated by a predetermined insulation distance 31a through the end of the electrode body 31. The main electrode film 32 and the auxiliary electrode film 33 can be easily formed by applying a conductive paint, spraying a metal, or vapor deposition. The main electrode film 32 is connected to the insulating terminal 6 by the connection lead 7, and the divided voltage is led to the outside. Auxiliary electrode
33 is directly connected to the metal capacitor 1 by the connection lead 17.

When the electrode portion is constructed in this way, the main electrode film
The electric field distribution at the end of 32 becomes an almost uniform electric field, and the main capacitance can be grasped from the time of design as in Examples 1 and 2, and the number of parts for mounting the electrode part is reduced, Work becomes easy.

In this embodiment, the linear expansion coefficient of the electrode body 31 is set to the diameter ratio D ₂ / D ₁ between the inner conductor 2 and the main electrode film 32, the maximum temperature rise ratio t ₂ / t ₁ , and the main capacitance C. _From the relationship with the allowable change rate S of ₁ , the main capacitance C ₁ can be changed to the allowable change rate S by using the material adjusted to the linear expansion coefficient β required for the resin material of the main electrode body 32 by using the above formula 17. It can be within.

When a resin material having a large linear expansion coefficient β is used as described above, even if the allowable change rate S of the main capacitance C ₁ requires a small value, even if the temperature rises, It is possible to obtain the capacitor voltage divider in which the accuracy of the electrostatic capacitance C ₁ is ensured. FIG. 6 shows the relationship between the linear expansion coefficient β required for the main electrode 13 or 23 when the material of the inner conductor 2 is copper and the allowable change rates S = 0, S = 0.001 and S = 0.015.
Shown in.

[0046]

In the capacitor voltage divider according to the first aspect of the present invention, the inner conductor is housed in the center of the metal container, and both ends are near the inner circumference of the metal container of the gas-insulated electric equipment filled with the insulating gas. The main electrode is provided with an auxiliary electrode that is insulated and supported at the end of the main electrode.By providing the auxiliary electrodes that are insulated and supported at both ends of the main electrode, the spread of the electric field at the end of the main electrode is eliminated, Since the accurate value of the main capacitance between the electrode and the internal conductor can be grasped from the time of design, the number of types of adjustment capacitors required to adjust the divided voltage after assembly is reduced, which simplifies the adjustment work. Moreover, since the influence of the surrounding electrodes on the main electrode portion is less likely to occur, the degree of freedom of the mounting position of the capacitor voltage divider on the gas-insulated electric device is increased.

In the capacitor voltage divider according to claim 2 of the present invention, one of the pair of auxiliary electrodes is fixed to the metal container as a mounting seat for mounting the electrode portion on the inner circumference of the metal container. The number of parts for mounting the capacitor voltage divider on the gas-insulated electrical equipment is reduced, and the mounting work can be easily performed, and the main capacitance can be accurately grasped from the time of design as in the case of claim 1, and the The number of adjusting capacitors for adjusting the piezoelectric voltage is reduced, and the working time required for the adjusting work is shortened.

In the capacitor voltage divider according to claim 3 of the present invention, the main electrode has a cylindrical shape, a slit is provided at one position on the circumference in the axial direction, and the pair of auxiliary electrodes are provided in the metal container at a predetermined interval. Since it is fixed and the insulating ring is inserted and mounted between the auxiliary electrodes, the main capacitance can be accurately grasped from the time of design as in the case of claims 1 and 2, and the electrode part can be mounted. Since the space is small, the diameter of the metal container can be made small, and the installation work is easy.

In the capacitor voltage divider according to claim 4 of the present invention, the inner conductor is made of a material having a linear expansion coefficient smaller than a value obtained by dividing the allowable rate of change of the main capacitance by the maximum temperature rise value of the inner conductor. Since the electrode is a material having a larger linear expansion coefficient than the value obtained by dividing the product of the linear expansion coefficient of the internal conductor material and the maximum temperature increase value of the internal conductor by the maximum temperature increase value of the main electrode,
A capacitor voltage divider in which the rate of change of the main capacitance does not exceed the allowable range in the operating temperature range regardless of the diameters of the inner conductor and the main electrode.

In the capacitor voltage divider according to the fifth aspect of the present invention, the material of the inner conductor is copper, and the material of the main electrode is aluminum or an aluminum alloy containing aluminum as a main component. With this configuration, a capacitor voltage divider having a main capacitance change rate of 0.15% or less can be obtained in the temperature range from the temperature at the time of manufacture to the state where the maximum temperature rises.

According to a sixth aspect of the capacitor voltage divider of the present invention, the electrode portion is a main electrode at a predetermined position on the inner peripheral surface of the electrode body made of a resin material, and the main electrode has a predetermined distance from the end portion. Since the conductive film to be the auxiliary electrode is attached to the outer peripheral surface beyond the end from the position where the is placed, the electric field at the end of the main electrode does not spread, and the accurate main capacitance can be grasped from the time of design. Therefore, the number of types of adjustment capacitors for adjusting the partial pressure need not be large, and the adjustment can be easily performed, and the number of parts to be mounted on the electrode portion is small, and the assembling work can be facilitated.

[Brief description of drawings]

FIG. 1 shows a first capacitor voltage divider according to the present invention.
It is sectional drawing which shows the Example of.

FIG. 2 shows a second capacitor voltage divider according to the present invention.
It is sectional drawing which shows the Example of.

FIG. 3 is a third diagram of a capacitor voltage divider according to the present invention.
It is sectional drawing which shows the Example of.

FIG. 4 is a diagram showing a necessary main electrode material corresponding to a diameter ratio between an inner conductor and a main electrode for obtaining a permissible rate of change of a main capacitance in a temperature change range during use of a capacitor voltage divider according to the present invention. It is a figure which shows the curve which calculates | requires a linear expansion coefficient.

FIG. 5 is a diagram showing a main electrode corresponding to a diameter ratio between the inner conductor and the main electrode when the inner conductor material of the capacitor voltage divider according to the present invention is copper and the main electrode material is aluminum or an aluminum alloy containing aluminum as a main component. It is a figure which shows the change rate of electrostatic capacitance for every operating temperature.

FIG. 6 shows that the permissible rate of change of the main capacitance is 0, 0.001 and 0.00 corresponding to the diameter ratio between the inner conductor and the main electrode when the inner conductor material of the capacitor voltage divider according to the present invention is copper.
FIG. 8 is a diagram showing a curve for obtaining the linear expansion coefficient of the main electrode material for setting the value to 15.

FIG. 7 is a fifth diagram of a capacitor voltage divider according to the present invention.
It is sectional drawing which shows the Example of.

8 is an enlarged cross-sectional view of the electrode end portion of FIG. 7.

FIG. 9 is a cross-sectional view showing a conventional capacitor voltage divider used in gas-insulated electrical equipment.

FIG. 10 is an equivalent circuit of a capacitor voltage divider.

[Explanation of reference symbols] 1 metal container 2 inner conductor 6 insulating terminal 13 main electrode 14 insulating ring 15 auxiliary electrode 23 main electrode 24 insulating ring 25 auxiliary electrode 30 electrode part 31 electrode body 32 main electrode film 33 auxiliary electrode film

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Naoto Yamamoto 8-1-1 Tsukaguchihonmachi, Amagasaki City Mitsubishi Electric Corporation Itami Works

Claims (6)

[Claims] 1. An internal conductor is housed in the center, is provided inside a metal container filled with an insulating gas, and is arranged concentrically with the internal conductor having a predetermined length and insulated and supported by the metal container. A main electrode, an auxiliary electrode connected to both ends of the main electrode through an insulating member on an extension of the main electrode, and a terminal connected to the main electrode and led to the outside of the metal container. A capacitor voltage divider, wherein auxiliary electrodes connected to both ends of the main electrode are electrically connected to the metal container. 2. The capacitor voltage divider according to claim 1, wherein one auxiliary electrode is fixed to the inner wall of the metal container, and the main electrode is fixed to the auxiliary electrode via an insulating member. 3. A pair of auxiliary electrodes having an inner conductor housed in the center thereof and fixed to the inner wall of a metal container filled with an insulating gas at a predetermined interval, and having a cylindrical shape, A slit in the axial direction is provided at a location, and a main electrode insulated and supported between the pair of auxiliary electrodes, and a terminal connected to the main electrode and led to the outside of the metal container are provided. Capacitor voltage divider. 4. An inner conductor is housed in the center, is provided inside a metal container filled with an insulating gas, is insulated and supported by the metal container, and has a predetermined length arranged concentrically with the inner conductor. Of the main conductor and a terminal connected to the main electrode and led to the outside, and the inner conductor has an allowable change rate of the main capacitance between the inner conductor and the main electrode divided by the maximum temperature rise value of the inner conductor. The linear expansion coefficient is larger than the value obtained by dividing the product of the linear expansion coefficient of the inner conductor material and the maximum temperature rise value of the internal conductor by the maximum temperature rise value of the main electrode. A capacitor voltage divider characterized by using a material having. 5. A main electrode having an inner conductor housed in the center thereof, provided inside a metal container filled with an insulating gas, insulated and supported by the metal container, and arranged concentrically with the inner conductor, A terminal connected to a main electrode and led out of the metal container, wherein the material of the inner conductor is copper and the material of the main electrode is aluminum or an aluminum alloy containing aluminum as a main component. Capacitor voltage divider. 6. An inner conductor is housed in the center, is provided inside a metal container filled with an insulating gas, is supported concentrically with the inner conductor in the metal container, and a main part is made of a resin material in a cylindrical shape. An electrode part that is molded and has a main electrode at the center of the inner peripheral surface and a conductive film that serves as an auxiliary electrode at the end of the inner peripheral surface, and an insulating terminal connected to the main electrode and led out of the metal container. And the auxiliary electrode is electrically connected to a metal container.