JPH0113621B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a vacuum level monitoring device for vacuum switchgear such as vacuum shields and disconnectors. In general, the ability of vacuum switchgears such as vacuum insulators and disconnectors to disconnect greatly depends on the quality of the internal vacuum, so it is important to monitor the vacuum level. For this reason, various vacuum degree monitoring devices have been proposed in the past, but all of them have problems with insulation, size, cost, etc., and are not practical. Therefore, the applicant of the present application has previously proposed a vacuum level monitoring device for vacuum electrical equipment in Japanese Patent Application No. 55-37098, but this vacuum level monitoring device is designed to prevent vacuum electrical equipment such as vacuum shields and Focusing on the fact that the shared voltage inside the device changes, which changes the electric field near the outside of vacuum electrical equipment, such as vacuum shields and circuit breakers, this electric field is detected, and the degree of vacuum can be determined based on the magnitude of this detection signal. This is an attempt to carry out monitoring. FIG. 1 shows the configuration of a vacuum degree monitoring device for a vacuum switchgear, such as a vacuum switch or disconnector. In Fig. 1, 1 is a vacuum shield, 2 is a fixed electrode, 3 is a movable electrode, 4 is a fixed lead, 5 is a movable lead, 6 is an insulating tube, and 7 and 8 are sealed at both ends of the insulating tube 6. The fixed lead 4 is attached to the end plate 7 and the movable lead 5 is sealed to the end plate 8 via the bellows 9. 10 is a shield attached to the middle of the insulating cylinder 6. The interior of the vacuum vessel of the vacuum shield and disconnector with such a configuration is maintained at a high vacuum, and when this degree of vacuum deteriorates, the fixed electrode 2, movable electrode 3, and shield 1
The resistance between 0 and 0 suddenly decreases, and the voltage between the fixed electrode 2, movable electrode 3 and shield 10 decreases,
Changes occur in the shared voltage at each part of the vacuum shield and disconnector. Therefore, the voltage across the shield 10 varies greatly depending on the degree of vacuum, and the electric field E near the shield 10 also varies greatly. Figure 3 shows the relationship between the pressure inside the vacuum shield and the electric field strength near the outside of the vacuum shield. Reference numeral 11 denotes an electric field sensor provided near the outside of the shield 10, and as shown in FIG. and is housed in an insulator case 15,
The light from the light emitting section (electrical-to-optical converter) 16 is supplied to the electric field sensor 11 via the optical fiber 17, and the light from the electric field sensor 11 is supplied to the light receiving section (optical-to-electrical converter) 19 via the optical fiber 18. Here, the received light is converted into an electric signal corresponding to the amount of light and outputted, and this output is received by the degree of vacuum quality determining section 20 to determine whether the degree of vacuum is good or bad. Vacuum degree quality judgment section 2
0 detects deterioration of the degree of vacuum due to a sudden increase (or decrease) in the output of the light receiving section 19, and outputs an output for alarm or display. In the vacuum level monitoring device having such a configuration, a Pockels element 12 is used as the electric field sensor 11, and the Pockels effect is used to detect the electric field strength according to the vacuum level, and the quality of the vacuum level is determined based on the magnitude of the detected amount. However, various considerations must be taken to avoid false detections, such as when the amount of light changes due to factors other than the electric field, or when the electric field changes regardless of the degree of vacuum (for example, due to surge voltage). To,
The structure was a little complicated. The present invention was made in view of these points,
That is, a light emitting part, an electric field sensor arranged on the outer circumferential side of the vacuum part of the vacuum switchgear and using a liquid crystal,
A light receiving section having a light receiving element is coupled with an optical fiber, and the output of the light receiving section is used as a vacuum level monitoring signal,
The purpose of this invention is to provide a vacuum level monitoring device for vacuum switching equipment, which is characterized by being able to monitor and measure the vacuum level at all times, and will be described below using examples. Before explaining the present invention, first, a liquid crystal used as an electric field sensor applied to the present invention will be explained.
There are several operating methods for liquid crystals. First, the dynamic scattering effect (DSM) is shown in Figures 4 and 5, respectively.
The structure of a liquid crystal device using this method and the transmission characteristics of a dynamic scattering effect (DSM) type liquid crystal device are shown. In Figure 4, 21 is the dynamic scattering effect (DSM)
22 and 23 are the liquid crystals 21 and 23, respectively.
Transparent electrodes are arranged on the upper and lower surfaces of the transparent electrodes 22 and 23, and an AC power source (or a DC power source is also acceptable) is connected between these transparent electrodes 22 and 23. Also 24,
25 is glass, 26 is an insulating member such as plastic, and the side surface of the liquid crystal 21 is surrounded by the insulating member 26. These transparent electrodes 22 and 23 and the insulating member 26 react with the liquid crystal 21 and
It is a substance that does not affect the When voltage is applied from the power source V to the transparent electrodes 22 and 23 configured in FIG. 4, the applied electric field E (=V/d,
The relationship between the transmittance P ₂ /P ₁ (where V is the power supply voltage and d is the thickness of the liquid crystal 21) is shown in FIG. here,
P ₁ and P ₂ are the input light energy and the output light energy, respectively. Figures 6 and 7 show the twist effect (TN) type liquid crystal element structure and twist effect (TN), respectively.
This figure shows the transmission characteristics and optical rotation characteristics of a type liquid crystal element. In FIG. 6, numeral 31 is a liquid crystal that utilizes a twisting effect (TN), 32 and 33 are transparent electrodes arranged on the upper and lower surfaces of the liquid crystal 31, respectively, and an AC power source is connected between these transparent electrodes 32 and 33. V
(DC power supply is also acceptable) is connected. 34 is a polarizing plate as a polarizer, 35 is a polarizing plate as an analyzer, and the polarization planes of these polarizing plates 34 and 35 are made parallel. 36 and 37 are glass, and 38 is an insulating member such as plastic, and the side surface of the liquid crystal 31 is surrounded by the insulating member 38. These transparent electrodes 32 and 33 and the insulating member 38 are materials that do not react with the liquid crystal 31 and do not affect the liquid crystal 31. In FIG. 7, the dotted line curve A indicates the applied electric field E when a voltage V is applied to the liquid crystal 31 with a thickness d without using the polarizing plates 34 and 35.
(=V/d) and the angle of optical rotation (deg), and the solid line curve (B) is the structure shown in FIG. This is a transmission characteristic curve showing the relationship between applied electric field E (=V/d) and transmittance when a voltage is applied to 32 and 33 from power source V. Note that if the polarization planes of the polarizing plates 34 and 35 are at right angles, the applied electric field E
The relationship between the transmittance P ₂ /P 1 and the transmittance P 2 /P ₁ is reversed as shown in FIG. 7A. Furthermore, field effect type Distortion of Align Phase
The structure of a liquid crystal element (abbreviated as DAP type) is similar to that shown in FIG. 6 described above, and the transmission characteristics and optical rotation characteristics of the DAP type liquid crystal element are also similar to those shown in FIG. 7 described above. Note that even in the case of a torsional effect (TN) type liquid crystal element configuration or a DAP type liquid crystal element configuration, the polarizing plate 35 is required using the configuration shown in Figure 6, but the output light of the photodiode is used as the input light. In this case, the polarizing plate 34 is required, but if laser light is used, the polarizing plate 34 becomes unnecessary. The difference between the dynamic scattering effect (DSM) type liquid crystal and the twisting effect (TN) and DAP type liquid crystal described above is that the DSM type is easy to construct, while the TN and DAP types have a remarkable threshold in their transmission characteristics. be. Furthermore, the threshold value of the TN type in particular can be controlled by adjusting the components of the liquid crystal, and when used in the electric field sensor part of the vacuum level monitoring device of vacuum switchgear, it is possible to match the electric field strength. It is possible. The table below shows the classification of LCDs by function.

[Table] Liquid crystals with high contrast are used for electric field sensors in vacuum level monitoring devices for vacuum switchgear.
It is preferable to use the DAP type or TN type. In addition
The DMP type and TN type are used depending on the electric field strength used in the vacuum switchgear. FIG. 8 shows an embodiment of the vacuum degree monitoring device for vacuum switchgear according to the present invention, and the same reference numerals are used for the same components as in FIG. 1 or those having the same functions. In the figure, reference numeral 40 denotes a tank wall that houses the vacuum chamber and disconnector 1, and is grounded. Reference numeral 41 denotes an electric field sensor disposed on the outer circumferential side of the vacuum shield disconnector 1, and FIG. 9 shows details of a case where, for example, a torsion effect (TN) type liquid crystal element is used as the electric field sensor 41. In FIG. 9, a polarizing plate 13 as a polarizer and a polarizing plate 14 as an analyzer are arranged on both sides of a torsional effect (TN) type liquid crystal 42,
A glass member 43 is disposed in contact with the input light side of the polarizing plate 13, and an optical fiber 17 is connected to this glass member 43. Further, a glass member 44 is disposed in contact with the output light side of the polarizing plate 14, and an optical fiber 18 is connected to this glass member 44. These liquid crystal 42, polarizing plates 13, 14, and glass members 43, 44
is housed in an insulator case 15. The polarizing plates 13 and 14 and the insulating case 15 are made of materials that do not react with the liquid crystal 42 and have no effect on the liquid crystal 42. Next, the torsion effect (TN) is used as the electric field sensor 41.
The operation when using a type liquid crystal element will be explained below. Light from a photodiode of the light emitting unit 16, for example, is input to the electric field sensor 41. Vacuum switching equipment Here, an electric field corresponding to the degree of vacuum inside is distributed on the outer circumferential side of the vacuum switch 1. Therefore, an electric field is applied to the liquid crystal 42 of the electric field sensor 41.
Therefore, the light (light energy P ₁ ) input to the electric field sensor 41 is transmitted through the liquid crystal 42 through the polarizing plate 13 as a polarizer, and the light (light energy P _{2 )} is extracted through the polarizing plate 14 as an analyzer. ) is the transmittance (P ₂ /
P ₁ ). In other words, the degree of vacuum has deteriorated (defective)
If so, the applied electric field increases in accordance with the degree of the change, and as the applied electric field increases, the output light (light energy P ₂ ) from the electric field sensor 41 decreases extremely. Light receiving part 1
9 receives this reduced output from the electric field sensor 41, converts it into an electric signal (current signal), and at this time displays or outputs an alarm signal as a vacuum degree failure. When light (light energy P ₂ ) in a good-quality region is supplied, the light energy P ₂ is large, so the configuration may be such that it is not output even if it is converted into an electrical signal. For example, the configuration of the light receiving section 19 may be a combination of a photoelectric conversion section and a switching circuit using, for example, a transistor. Furthermore, since the transmission characteristics of the liquid crystal element differ depending on the type of the liquid crystal element, it goes without saying that the light receiving section 19 is configured to be able to extract a detection signal corresponding to a poor vacuum degree. This detection signal may be used as an alarm or display signal. Although FIG. 8 of this embodiment refers to the case where a torsional effect (TN) type liquid crystal element (see FIG. 9) is used as the electric field sensor 41, the present invention is not limited to this, and the present invention can be used as an electric field sensor. The same applies to cases where a dynamic scattering effect (DSM) type liquid crystal element or a field effect type Distortion of Align Phase (abbreviated as DAP type) liquid crystal element is used. In this case, when a DSM type liquid crystal element is used, the configuration of the electric field sensor 41 is as shown in FIG. 9, using a DSM type liquid crystal instead of the liquid crystal 42, and
14 is not required, DSM type liquid crystal and glass member 43,
44 is housed in an insulator case 15,
Further, when a DAP type liquid crystal element is used, the configuration is such that the DAP type liquid crystal is used instead of the liquid crystal 42 in FIG. 9. Note that using a laser as the light emitting section 16,
When inputting the laser light (indicating a single vibration) to an electric field sensor, a polarizing plate as a polarizer is not required. The present invention is not limited to this embodiment, and various applications and modifications are possible. By using the vacuum level monitoring device for vacuum switchgear according to the present invention described above, the following various effects can be achieved. (1) By using a liquid crystal element (TN type liquid crystal element, DAP type liquid crystal element) as an electric field sensor,
A vacuum level quality determination section is not required, and the configuration is simplified. (2) Since the optical path of the electric field sensor section can be made smaller than that of conventional Pockels type elements, there is no need for an optical system that parallelizes the light emitted from the optical fiber, and the structure of the electric field sensor section is simple. (3) The vacuum state inside vacuum switching equipment can be monitored without contact, without changing the equipment structure at all. (4) Optical fibers can easily insulate the ground potential from high-voltage parts such as vacuum shields and vacuum switchgear such as disconnectors, so the degree of vacuum can be monitored regardless of the voltage class ( (See Figure 8). (5) Electric field sensor 41 and optical fibers 17, 18
It is made entirely of insulators and is small, so it is easy to implement. (6) All liquid crystal elements that make up the electric field sensor installed in the high voltage section of vacuum switchgear are passive elements.
Very reliable. (7) Since the degree of vacuum is detected using the effect of light, the system has high noise resistance. (8) Short time like surge voltage (several to several 100 μs)
Since the response time of a liquid crystal element to a pulse of 10 ms or more is over several tens of milliseconds, no special surge voltage countermeasure device is required. (9) Since the vacuum level of vacuum switchgear is automatically monitored, it is easy to automate the power system.

[Brief explanation of drawings]

Figure 1 is a configuration diagram showing an example of a conventional vacuum level monitoring device for vacuum switchgear, Figure 2 is an enlarged sectional view of section A in Figure 1, and Figure 3 is a diagram showing the pressure inside the vacuum chamber and the vacuum. Figure 4 is a configuration diagram of a liquid crystal element that utilizes the dynamic scattering effect, Figure 5 is a transmission characteristic diagram of the dynamic scattering effect type liquid crystal element shown in Figure 4, Figure 6 is a configuration diagram of a twist effect type liquid crystal element.
FIG. 7 is a diagram showing optical rotation characteristics and transmission characteristics of a torsional effect type liquid crystal element, FIG. 8 is a configuration diagram showing an embodiment of a vacuum degree monitoring device for vacuum switching equipment according to the present invention,
FIG. 9 is an enlarged sectional view of part B in FIG. 8, in which 1 is a vacuum shield, 13 and 14 are polarizing plates, and 15
1 is an insulator case, 16 is a light emitting part, 17 and 18 are optical fibers, 19 is a light receiving part, 41 is an electric field sensor, 4
Reference numeral 2 indicates a twist effect type liquid crystal, and reference numerals 43 and 44 indicate glass members.

Claims (1)

[Scope of Claims] 1. A light emitting unit, an electric field sensor disposed on the outer peripheral side of a vacuum section of a vacuum switchgear, and using a liquid crystal;
1. A vacuum level monitoring device for a vacuum switchgear, characterized in that a light receiving section having a light receiving element is coupled with an optical fiber, and an output of the light receiving section is used as a vacuum level monitoring signal. 2. The vacuum degree monitoring device for vacuum switching equipment according to claim 1, characterized in that a dynamic scattering effect type liquid crystal is used as the electric field sensor. 3. The vacuum level monitoring device for vacuum switchgear according to claim 1, characterized in that the electric field sensor includes a torsional effect type liquid crystal and at least a polarizing plate as an analyzer. 4. The vacuum degree monitoring device for vacuum switchgear according to claim 1, comprising a field effect (DAP) liquid crystal as an electric field sensor and a polarizing plate as at least an analyzer.