JPH01213577A - Voltage measuring instrument - Google Patents

Abstract

PURPOSE:To certainly measure a surge waveform by coaxially setting a conductor having an almost conical shape at the center of an almost conical chamber and connecting the bottom surface of the conductor with one face of an electrode. CONSTITUTION:A discoidal electrode 1 is disposed by pinching earthing potential metal 2 and an insulating substance sheet 3 and a floating capacity C2 is formed between the electrode 1 and metal 2. Moreover, a conical conductor 4 is connected with the electrode 1 by its bottom surface. At the outer periphery of the conductor 4 an earthing potential metal 5 having a conical space which is larther than the conical body of the conductor 4 is provided coaxially on the conductor 4. Since the potential is detected by means of the conductor 4 in the wide area of the electrode 1 in such capacity of voltage divider 20, internal resonance is detected after averaging the resonance even if the internal resonance is produced inside the floating capacity C2. Therefore, the influences of a self-resonance mode can be eliminated and surge waveforms can be measured correctly.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a device for measuring the voltage of a high-voltage device, and in particular, the present invention relates to a device for measuring the voltage of a high-voltage device. The present invention relates to a voltage measuring device for measuring surge voltage.

(Prior Art) Traditionally, wire-wound instrument transformers and resistor voltage dividers have been widely used as devices to measure the voltage of high-voltage devices such as GIS, but recently, 50H7 or 6
There is an increasing need to simultaneously measure not only the commercial frequency voltage of 0H7 but also the high frequency disconnector surge voltage of several MH7 to several tens of MH2 generated when the disconnector is operated.

This is because as the operating voltage increases, the disconnector surge generated inside the GIS becomes larger than the lightning surge that enters from the outside, and the insulation structure for this disconnector surge is a factor that determines the size of the equipment. It becomes. Furthermore, in the field of laser and nuclear fusion research, very short steep wave pulses with voltage rise times on the order of nanoseconds have recently become necessary, and the importance of observing these waveforms is increasing. A capacitive voltage divider is used as a means for observing such voltage waveforms.

As a capacitive voltage divider for GIS disconnector surge measurement, for example, IEEE l"'ransacj!0rls
on Electrical In5lation
n Vol, EI-19No, 2. A1) ril
In 1984 P., 87-92, a capacitive voltage divider having a structure as shown in FIG. 5 was proposed.

In FIG. 5, a film 3 made of an insulating material is sandwiched between the disc-shaped electrode 1 and the ground potential metal 2, and is fixed to form a stray capacitance C2 between the electrode 1 and the ground potential metal 2. has been done. In this case, the electrode 1 has a stray capacitance C+ between it and a high voltage conductor (not shown), and these stray capacitances Ct and C2 form a capacitive voltage divider. The electrode 1 is connected to a lead wire 4- through a resistor 11, and the other end of the lead wire 4- is connected to a coaxial cable connector 6.
It is connected to the. A gap with a circular cross section is formed in the ground potential metal 2 so as to penetrate from the surface on the electrode 1 side to the opposite side, and the resistor 11 and the lead wire 4- are inserted into this gap. . Further, the connector 6 is attached to an opening on the opposite side of the electrode 1 in the gap. On the other hand, a cover 1a is provided at the connection portion between the electrode 1 and the resistor 11 to alleviate the electric field. Note that 8 in the figure is a flange fixed to a flange of a GIS (not shown).

As described above, in the conventional capacitive voltage divider, the electrode 1 and the coaxial cable are connected at only one point via the lead wire 4-, so the potential of the electrode 1 is detected only at one point.

(Problem to be Solved by the Invention) By the way, in the capacitive voltage divider shown in FIG. 5, the facing surfaces of the electrode 1 and the ground potential metal 2 are made completely parallel, so that the distribution of the stray capacitance C2 is completely uniform. It is impossible to do so. Therefore, since the distribution of stray capacitance C2 is not uniform,
When a steep wave with a very quick rise time is applied to this capacitor, the potential of the electrode 1 becomes uniform, but a state in which the potential locally varies in magnitude occurs instantaneously. As a result, a current flows in the electrode 1 to make the potential uniform, and it has been found that this current generates a voltage inside the stray capacitance C2. 1
Capacitive voltage dividers that detect the potential at only one point are affected by such internal resonance, and the waveform due to internal resonance is superimposed on the original surge waveform, making it difficult to observe the waveform accurately. It turns out that.

The present invention was proposed in order to solve the problems of the prior art, and its object is to provide a G
It is an object of the present invention to provide an excellent voltage measurement device that can accurately observe the voltage waveform of a steep wave surge whose rise is on the order of nanoseconds generated inside an IS and a steep wave pulse used in lasers and nuclear fusion.

[Structure of the Invention] (Means for Solving the Problems) The voltage measuring device of the present invention includes the following steps when connecting electrodes having stray capacitance to each of a ground potential metal and a high voltage conductor to a connector of a coaxial cable. A ground potential metal electrode is connected to the coaxial cable side of the ground potential metal, a substantially conical space with the electrode side as the bottom surface is formed in the ground potential metal electrode, and within this substantially conical space, A substantially conical conductor is installed coaxially, the bottom surface of the substantially conical conductor is connected to one surface of the electrode, and the top of the substantially conical conductor is connected to the connector of the coaxial cable. It is characterized by

(Function) In the present invention having the above configuration, by using a substantially conical conductor, the potential of the electrode can be detected over a wide area corresponding to the bottom surface of the conductor. The internal resonance modes generated in the stray capacitance C2 are averaged. Therefore, the influence of the self-resonant mode can be removed, making it possible to accurately observe the surge waveform.

(Example) An example of a voltage measuring device according to the present invention is shown in FIGS. 1 and 2 below. Note that the same parts as in the conventional technique 1 shown in FIG. 5 are given the same reference numerals.

FIG. 1 is a sectional view showing the capacitive voltage divider of this embodiment, and corresponds to FIG. 5 showing a conventional capacitive voltage divider. In FIG. 1, a disk-shaped electrode 1 is placed across a ground potential metal 2 and an insulating sheet 3, forming a stray capacitance C2 between them. Here, the electrode 1 forms a stray capacitance C1 with a high voltage conductor (not shown). Further, the conical conductor 4, which corresponds to the conventional lead wire 4-, has an electric current of %M on its bottom surface.
Connected to 1. On the outer periphery of this conical conductor 4,
Ground potential metal electrode 5 with a larger conical space
A conical structure 21 is formed by both members 4 and 5, and the central axes of both cones coincide with each other. The top of the conical conductor 4 is connected to the center electrode of a connector 6 of the coaxial cable, and the outer electrode of the connector 6 is connected to the metal electrode 5 at ground potential. The ground potential metal 2 is fixed by its flange 8 to the flange 9 of the GIS tank 7. Here, the outer diameter d4 of the conical conductor 4 and the inner diameter d5 of the conical space of the ground potential metal electrode 5 are selected so as to satisfy the following condition at all points: d5/d4=constant. For example, if d5/d+ is selected to be 2.3, the line of the conical structure 21 formed by the conical conductor 4 and the ground potential metal electrode 5 becomes a coaxial cable with a characteristic impedance of 500.

FIG. 2 is a cross-sectional view of the capacitance voltage divider 20 shown in FIG. 1 installed in the GIS tank 7.
is a high voltage conductor in GIS.

FIG. 3 is a diagram showing a connection circuit between the capacitive voltage divider 20 of FIG. 1 and the waveform observation device 12 such as an oscilloscope. The characteristic impedance Z2 (for example, 50Ω) of the coaxial cable 13 and the characteristic impedance Zl of the conical structure 21 of the capacitive voltage divider 20 are made equal, and Z1=22
=Z.

In FIG. 3 (A>), the input impedance 14 of the waveform observation device 12 is the characteristic impedance Z of the coaxial cable 13.
It is taken as equal to 2.

In FIGS. 3(B) and 3(C), a resistor 15 (R1) is placed between the coaxial cable 13 and the conical structure 21.

16 (R2) and capacitor 17 (C3), and a resistor 18 (
By connecting the capacitor 19 (R3) and the capacitor 19 (C41), the input impedance of the waveform observation device 12 can be changed to Z2
It is set to a sufficiently large value (for example, 1 MΩ) compared to .

In this case, each circuit constant in FIGS. 3(B) and 3(C) is selected so as to satisfy the following conditional expression.

Circuit of FIG. 3(B): R1(R2-Z)=Z2. R3=Z... Conditional expression ■ C10C2= (Z/Rt) (C10 103 104) K
I K2 ... Conditional expression ■ Circuit of Fig. 3 (C): R1 (R2 + Z) = Z2. R3=Z... Conditional expression ■ C102 = (R2/Z) (C+C0C3+C4) K1 to 2... Conditional expression ■ However, CK1 is the center conductor 4 of the coaxial cable formed by the conical structure 21 The capacitance that CK has with respect to the external electrode 5, CK
2 represents the capacitance that the center conductor of the coaxial cable 13 has with respect to the external electrode.

The operation of this embodiment having the above configuration is as follows.

That is, in the conventional capacitive voltage divider as shown in FIG.
When leading the terminal voltage of 2 to the coaxial cable, the potential was detected at one point of electrode 1 by lead wire 4-,
In the capacitive voltage divider 20 of this embodiment, since the potential is detected over a wide area of the electrode 1 using the conical conductor 4, the stray capacitance C
Even if internal resonance occurs inside the device 2, this internal resonance is averaged and detected, and has the effect of removing such an internal resonance waveform.

Furthermore, since the characteristic impedance Z1 of the conical structure 21 and the characteristic impedance Z2 of the coaxial cable 13 are made equal, they are connected as shown in FIG. cable 13
When the characteristic impedance Z2 is set equal to the characteristic impedance Z2, both cables 13.degree. 21 can be connected with matching, and therefore, signal reflection within the cable can be eliminated. Since this method has a simple circuit configuration, high frequency characteristics can be improved.

However, in the circuit shown in FIG. 3 (A>), the electrode 1
Since a low resistance (for example, 50Ω) is connected in parallel to the stray capacitance C2 between the metal 2 and the ground potential metal 2, low frequencies cannot be measured. Therefore, the circuits shown in FIGS. 3(B) and 3(C) can be considered. In these circuit configurations, the conditional expression ■
, ■, and ■, ■, each coaxial cable can be matched and the voltage division ratio of low frequency component and high frequency component can be made equal, so from AC voltage of 50Hz and 60Hz to high frequency of several hundred MH7, A measuring instrument with a wide frequency band can be realized.

As described above, in this embodiment, the influence of internal resonance generated in the low-voltage side stray capacitance C2 of the capacitive voltage divider can be removed, and a voltage measuring device with good high frequency characteristics can be provided.

Further, it is possible to provide a voltage measuring device having a wide frequency band from AC with a frequency of 50H2 to high frequency with a frequency of several hundred MH2.

In the above embodiment, the characteristic impedance Zl of the coaxial cable formed by the conical structure 21 and the coaxial cable 1
Although the case has been considered in which the characteristic impedances Z2 of the coaxial cables 13 and 3 are made equal, a configuration in which the characteristic impedance Z1 of the conical structure 21 is larger than the characteristic impedance Z2 of the coaxial cable 13 is also possible. Such an embodiment is shown in FIG.

In FIG. 4, a resistor R1 is connected between the center conductor of the conical structure 21 and the center conductor of the coaxial cable 13, and a resistor R3 is connected between the coaxial cable 13 and the waveform observation device 12. and capacitor C4 are connected in parallel.

In this case, the values of each circuit constant are selected as follows.

R1+Z2 = Zt, R3=Z2... Conditional expression ■ C1+02 = (Z2 /Rt) (CK1+CK2+C4)...
Conditional Expression (2) Here, since Zl >22, R1 that satisfies Conditional Expression (0) has a positive value, and an actually existing resistor can be used. Furthermore, since the conditional expressions ■ and ■ correspond to the conditional expressions ■ and ■ or ■ and ■, the circuit shown in FIG. 4 is exactly the same as the circuit shown in FIGS. 3(B) and (C). You can get the effect of Roughly speaking, the circuit in Figure 4 is as shown in Figure 3 (B), (
Since the resistor 16 and capacitor 17 can be omitted from each circuit in C), the structure can be simplified and the high frequency characteristics can be improved.

[Effects of the Invention] As explained above, in the present invention, the potential of the electrode can be detected over a wide area by using a conical conductor instead of the conventional lead wire when connecting the electrode to the coaxial cable. , since the internal resonance mode of the capacitance can be averaged, G
Accurately observe voltage waveforms and voltage values, from voltages of steep wave surges with rise times on the order of nanoseconds generated in IS and steep wave pulses used in lasers and nuclear fusion to commercial frequency voltages of 50H2 or 60H2. It is possible to provide an excellent voltage measuring device that can perform the following functions.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a capacitive voltage divider of an embodiment of the voltage measuring device according to the present invention, and FIG. 2 is a sectional view showing the capacitive voltage divider of FIG.
3 and 4 are respectively circuit diagrams showing an example in which the capacitive voltage divider shown in Fig. 1 is connected to a waveform observation device, and Fig. 5 is a circuit diagram showing a conventional capacitive voltage divider connected to FIG. DESCRIPTION OF SYMBOLS 1... Electrode, 1a... Cover, 2... Ground potential metal, 3... Insulator sheet, 4... Conical conductor, 4-
Lead wire, 5... Ground potential metal electrode, 6... Connector, 7... GIS tank, 8, 9... Flange, 1
0... High voltage conductor, 11, 15, 16, 18... Resistor, 12... Waveform observation device, 13... Coaxial cable, 14... Input impedance, 17.19... Capacitor, 20... Capacity voltage divider, 21... Conical structure.

Claims (1)

[Claims] In a voltage measuring device that connects an electrode having stray capacitance to a coaxial cable connector for each of a ground potential metal and a high voltage conductor, a ground potential metal is connected to the coaxial cable side of the ground potential metal. An electrode is connected, and a substantially conical space with the electrode side as the bottom surface is formed in this ground potential metal electrode, and a substantially conical conductor is installed coaxially within this substantially conical space. A voltage measuring device characterized in that the bottom surface of the substantially conical conductor and one surface of the electrode are connected at a surface, and the top of the substantially conical conductor is connected to the connector of the coaxial cable.