JPS6345052B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vacuum level monitoring device for a vacuum switch, which includes a shared voltage equalizing capacitor in parallel with a vacuum interrupter.

In the case of vacuum switches such as vacuum switches and disconnectors, a decrease in the degree of vacuum can greatly affect the performance of the switch, such as a decrease in the degree of vacuum or a deterioration in the disconnection ability, so monitoring the degree of vacuum is desirable to improve the reliability of the equipment in which it is applied. .

As a conventional technique for monitoring the degree of vacuum, there is a method in which a pair of opposing electrodes for monitoring is prepared separately from the opening/closing electrode in a vacuum interrupter, and the discharge voltage between the pair of opposing electrodes is measured. This requires a special design of the vacuum interrupter itself, and it also requires a high-voltage power source to apply voltage between opposing electrodes, making the monitoring device large and expensive. Also, it was difficult to obtain sufficient insulation between the monitoring device and the switching electrode.

A device that solves the above problems is one that captures the decrease in the degree of vacuum in the vacuum interrupter as a change in the electric field around it, converts the change in the electric field into a change in refractive index using a Pockels element, and detects this refractive index with an analyzer and a light receiving element. The applicant has already proposed this (Japanese Patent Application No. 37098/1983).

The present invention focuses on the fact that in a vacuum switch including a shared voltage equalizing capacitor in parallel with a vacuum interrupter, the voltage applied to the capacitor changes depending on the degree of vacuum of the vacuum interrupter,
By using the capacitor as a means for applying an electric field to an electro-optic effect element such as a Pockels element or a Kerr element, it is possible to easily connect the vacuum interrupter and the electro-optic effect element, and also to enable reliable monitoring of the degree of vacuum. It is an object of the present invention to provide a vacuum level monitoring device that can be applied to equipment in which vacuum switches of 1 to 6 are connected in parallel or in series to provide an efficient configuration of the monitoring device.

Hereinafter, the principles and embodiments of the present invention will be explained with reference to the drawings.

FIG. 1 shows a sectional side view of a main part of a tank-type vacuum interrupter having a metal case that is grounded around a vacuum interrupter. An insulating cylinder 1 such as a glass tube has both end plates 2 and 3 forming a vacuum container, and a fixed lead 4 having an electrode is provided inside the container by penetrating one end plate 2. The bellows 5 is used as a means for partitioning the inside and outside of the container.
A movable lead 6 having an electrode is provided inside the container via the container. Also, on the surfaces of the end plates 2 and 3, leads 4,
6 are provided with conductors 7 and 8 electrically connected to each other,
Between the conductors 7 and 8, shared voltage equalizing capacitors 9 ₁ to 9 _2o are connected in series outside the container. On the outermost side of this vacuum interrupter is a metal container 10 containing an insulating gas and housing the interrupter.
is connected to earth. Further, the intermediate connection points of the capacitors 9 ₁ to 9 _2o are electrically connected to the intermediate shield 11, and the potential at that point is set to approximately 50%, and the potential distribution within the vacuum container is also made uniform.

In a vacuum shield/disconnector having such a configuration, the equivalent of closing when the movable lead 6 is brought into contact with the fixed lead 4 in an operating state in which the AC power supply 12 is connected to the fixed lead 4 and the load 13 is connected to the movable lead 6. The circuit will be as shown in FIG. In Figure 2, R1 is the resistance of the insulating cylinder 1, and R2 is the resistance of the leads 4, 6 and the shield 1.
C _p is the stray capacitance between the leads 4, 6 and the shield 11, C ₁ is the total capacitance of the upper and lower halves of the capacitors 9 ₁ to 9 _2o , C ₂ is the resistance between the shield 11 and the capacitors 9 ₁ to 9 _2o and the floating capacitance between the metal container 10.

As is clear from this equivalent circuit, when the degree of vacuum in the vacuum vessel 1 is good, the voltages at various parts of the vacuum interrupter are as follows.

V _AB =C ₂ /C ₀ +C ₁ +C ₂ V ......(1) V _AE =C ₀ +C ₁ /C ₀ +C ₁ +C ₂ V ......(2) E _C =E _AB /n ...(3) However, V _AB is the voltage between point A and point B in Figure 2,
_VAE is the voltage between point A and earth E, and V is the voltage of the power supply 12. In these equations (1) to (3), since the normal interrupter is C ₀ ≪C ₁ and C ₂ ≪C ₁ , V _AB <V _AE
becomes. Then, when the degree of vacuum decreases, V _AB decreases toward zero, V _AE increases toward V, and the voltage E _C of each of the capacitors 9 ₁ to 9 _2o decreases toward zero. This relationship is shown in Figure 3, with the vacuum vessel internal pressure on the horizontal axis and E _AE , E _AB , and E _C on the vertical axis. pressure
P ₁ or less indicates a value that is considered normal vacuum, P ₂ or more indicates a degraded vacuum, and there is no voltage between P ₁ and P ₂ .
Changes are seen in E _AE , E _AB , and E _C. The equivalent circuit when the movable lead 6 is disconnected from the fixed lead 4 is that the resistance R ₂ and the stray capacitance C ₀ are divided into the leads 6 and 4, respectively, and the resistance and stray capacitance are connected in parallel between the leads 6 and 4. A circuit is interposed, and the voltages E _AE , E _AB , and E _C at the time of opening, which become this equivalent circuit, exhibit a phenomenon similar to that at the time of closing due to changes in the degree of vacuum, although there are changes in level.

Therefore, the degree of vacuum can be determined by monitoring these voltages E _AB , E _AE , or E _C , and in the present invention, the degree of vacuum is determined by monitoring the shared voltage equalization capacitor voltage E _C. Compared to monitoring other voltages E _AE or E _AB , monitoring of this voltage E _C detects the voltage across a single capacitor, making it easier to install and remove the detection element, and it can be used as a monitoring device for existing vacuum switches. Facilitates installation, maintenance and inspection.

FIG. 4 shows a basic block diagram of a monitoring device according to the invention. Shared voltage equalization capacitor voltage E _C
is applied to an electro-optic effect element 14 such as a Pockels element or a Kerr element, and this electro-optic effect element 14 is integrally attached to a capacitor as a vacuum degree detection head 17 arranged between a polarizer 15 and an analyzer 16. , light enters the polarizer 15 from the light source 18 to the detection head 17 position via an optical fiber transmission path, and the light linearly polarized by the polarizer 15 passes through the electro-optic effect element 14 to generate a voltage E. _C is refracted in a linear or quadratic function relationship, and this light is passed through an analyzer 16 to determine the polarization direction component of the analyzer.
It is detected by the light receiving section 19 of the electrical conversion element, and a judgment section 20 such as a comparator makes a judgment based on the detected electric signal level, thereby obtaining an indication of whether the degree of vacuum is good or not, as well as an alarm signal.

A concrete structure for attaching the vacuum detecting head 17 shown in FIG. 4 to the vacuum interrupter is shown in FIG. In FIG. 5, conductors 21, 21 drawn out from both ends of the lowest capacitor 92o, which is one of the shared voltage equalizing capacitors _{91 to 92o} , are connected to the voltage application terminal of the detection head 17 and supported. The light input to the detection head 17 is sent from the ground-side light source 18 through an optical fiber 22 with good insulation, and the light output from the detection head 17 is transmitted through the optical fiber 23 to the ground-side light receiving section 19 and then to the judgment section 2.
Send to 0. Note that the capacitance of the detection head 17 is sufficiently smaller than that of the capacitor _92o and does not affect the capacitance accuracy of the capacitor _92o .
Further, when the detection head 17 has a low breakdown voltage, a configuration in which a voltage dividing capacitor is connected in series within the head can be easily realized.

In the embodiment, a case where the vacuum interrupter is applied to one vacuum interrupter is shown, but the present invention is not limited to this.
The same effects can be obtained by applying this method in series, and it is also possible to realize a monitoring device that integrates them all together.

Figure 6 shows an equivalent circuit in the case of one phase with two wires in series, and the equivalent circuit when the degree of vacuum is good is shown in Figure 7. In Figure 7, C ₃ = C ₀ + C ₁ , C ₄ = C _1/2
Similarly to the case of FIG. 2, the degree of vacuum of the two vacuum interrupters can be monitored at once by monitoring the voltage of the shared voltage equalizing capacitor. The device configuration for this collective monitoring is shown in FIG. 8, in which electro-optic effect elements 14A and 14B are provided in parallel to one shared voltage equalization capacitor of each of the two vacuum interrupters, and both elements 14A and 14B polarize each other. The planes are at right angles, and 14A of them are polarizers 15A on the receiving side.
, a polarizer 15B is provided on the output side, and the polarizer 15B is
The light emitted from the element 14B is used as a detection head with an analyzer 16 provided on the output side of the element 14B, and an optical fiber is used for optical transmission between the two elements. In this configuration, if deterioration of the degree of vacuum occurs in one or both of them, the intensity of light passing through the analyzer 16 decreases, and a determination output thereof can be obtained.

FIG. 9 is a structural diagram for monitoring the degree of vacuum in three phases at once, and as in the case of FIG.
At least one of the three-phase vacuum interrupters constitutes an optical system in which electro-optic effect elements 14A to 14C whose polarization planes are alternately perpendicular to 15C are arranged alternately.
This can be detected by the deterioration of the vacuum level of the book.

Similarly, as shown in FIG. 10, two vacuum interrupters per phase can be configured to monitor three phases at once.

As is clear from FIGS. 8 to 10, this collective monitoring can be configured by preparing one light receiving section 19, one light source 18, and one determining section 20, and the number of polarizers used per number of interrupters can be reduced. .

As described above, the vacuum level monitoring device according to the present invention can be applied to a vacuum switch having a voltage sharing equalization capacitor to easily monitor the vacuum level without changing its structure. Furthermore, when monitoring equipment having a plurality of vacuum switches, collective monitoring can be easily realized at a relatively low cost. In addition, the high-voltage part can be insulated from the ground using optical fiber, the detection head is a passive element that does not require a power supply and is highly reliable, and the vacuum interrupter can be monitored whether it is open or closed. It also has excellent resistance to electrical noise because it detects the degree of vacuum using a phenomenon based on the degree of polarization, making it easy to connect to a vacuum switch and enable reliable monitoring.

Note that the present invention is not limited to tank-type vacuum switches;
The same effect can be obtained by applying it to a vacuum switch that has an insulated tube instead of the metal container 10, or a vacuum switch filled with a solid insulator instead of an insulating gas between the envelope and the vacuum interrupter. .

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of a vacuum shield breaker with a voltage sharing equalization capacitor, Figure 2 is an equivalent circuit diagram when it is open, Figure 3 is a vacuum degree-voltage characteristic diagram in Figure 2, and Figure 4 is a block diagram of a monitoring device according to the present invention, Figure 5 is a diagram of the main part mounting structure of the present invention, Figure 6 is an equivalent circuit diagram of two vacuum shield disconnectors connected in series, and Figure 7 is an equivalent circuit diagram of two vacuum shield disconnectors connected in series. Equivalent circuit diagram modified from the diagram,
8 to 10 are block diagrams of other monitoring devices according to the present invention. 1... Vacuum container, 9 ₁ to 9 _2o ... Voltage sharing equalization capacitor, 14... Electro-optic effect element, 15
... Polarizer, 16 ... Analyzer, 17 ... Vacuum degree detection head, 18 ... Light source, 19 ... Light receiving section, 20
. . . Determination section, 21 . . . Conductor, 22, 23 . . . Optical fiber.

Claims (1)

[Claims] 1. In a vacuum switch having a plurality of series capacitors for equalizing voltage sharing in which the switching electrodes are connected in parallel outside the vacuum vessel and the intermediate connection point is electrically connected to the intermediate shield, both ends of one of the capacitors an electro-optic effect element to which a voltage is applied as a refractive index control voltage; a polarizer that linearly polarizes light from a light source and makes it enter the electro-optic effect element; an analyzer that detects light with a polarization direction component; a light receiver that converts the output light of the detector into a corresponding electrical signal; A vacuum level monitoring device for a vacuum switch, comprising: a determination unit that determines that the vacuum level has deteriorated.