JPH0594742A - Vacuum switchgear - Google Patents

Abstract

PURPOSE:To provide a vacuum switchgear by which workability of a judgment on the vacuum quality or various kinds of inspection tests in the vacuum switchgear having a vacuum switch tube in a container to seal up an insulating medium such as SF6 gas can be improved and the judgment on the vacuum quality can be carried out simply/reliably by applying a conventional widespread 20kV withstand voltage testing method. CONSTITUTION:A vacuum switch tube 3 having vacuum dielectric strength of an opening distance Lv=1mm and alternating voltage equal to or higher than 20kV, is housed inside of a container 1 to seal up SF6 gas 2 having pressure and dielectric strength higher than atmospheric pressure air. An opening distance adjusting device 20, by which the pressure of which inter-polar dielectric strength is an opening distance Lc >=1mm when the SF6 gas 2 is filled and alternating voltage becomes lower than 20kV is limited as the maximum pressure Ps of the SF6 gas 2, and by which an opening distance can be also shortened freely from a full opening position Ls to a closed position, is provided in an operation mechanism 10 inside of this vacuum switch tube 3. Even if a trace of vacuum leakage is caused, since an insulating medium is formed of mixed gas of gas having molecular weight smaller than the SF6 gas and the SF gas, by setting partial pressure of the SF6 gas below the atmospheric pressure, the vacuum resistant service life can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum switchgear in which a vacuum switch tube (hereinafter referred to as VST) is housed in a container for sealing an insulating medium.

[0002]

2. Description of the Related Art FIGS. 8 (a) and 8 (b) are views showing a fully opened state of a vacuum switchgear for a circuit breaker with a rated voltage of 12 kV and a rated fully opened distance L _S = 8 mm, and FIG. 8 (a) is a top view. FIG. 8 (b) is a side view. In the figure, reference numeral 1 is a container for sealing SF ₆ gas 2 as an insulating medium, which is generally called a cubicle, in which a VST 3 and other high voltage equipment not shown are housed. The SF ₆ gas filling pressure is generally higher than atmospheric pressure so as not to make the container negative, and a maximum pressure of 2 atmospheric pressure or lower is used in consideration of the characteristics of the bellows (not shown) of the VST 3. Reference numerals 3a and 3b denote fixed electrodes and movable electrodes of VST3, and L _S represents a full opening distance or a full opening position. Cable heads 4a and 4b are electrically connected to the fixed electrode 3a and the movable electrode 3b, respectively, and are drawn out to the atmosphere 7 side outside the sealed container 1. 8 is the frame of the vacuum switchgear, 10 is this frame 8
Is an operating mechanism for opening and closing the movable electrode 3b. In the case of the opening operation, the spring force of an open spring (not shown) is applied to the pin 11 and the shaft driven by the drive lever 12
The rotation of the drive lever 12 is transmitted to the main lever 15 via the joint 14, and the main lever 15 rotates with the center of the main shaft 16 as the rotation center together with the main shaft 16. Due to the rotation of the main shaft 16, the movable electrode 3b moves from the closed position to the fully opened position and is held at the fully opened distance L _S. Reference numeral 17 is a gas seal that allows the main shaft 16 to freely rotate and separates the SF ₆ gas 2 from the atmosphere 7. In the closing operation, the spring force of another closing spring (not shown) is transmitted to the main shaft 16 to close the movable electrode 3b. In the normal use state, both the opening and closing operations are performed at high speed, and the movable electrode 3b is stopped only at two positions of the closed electrode position or the fully opened electrode position L _S. It is a structure that cannot be done.

Next, the discharge start voltage characteristic between the VST electrodes will be described with reference to FIG. FIG. 9 shows V when the VST internal pressure P is changed from a high vacuum of 10 ⁻⁴ Torr or less to a high pressure of atmospheric pressure (760 Torr) or more with the full opening distance L _S being 8 mm.
It shows a change in the discharge start voltage V between the ST poles and is generally called a Paschen curve. Although the limit vacuum degree of VST is slightly different corresponding to the rated voltage of the vacuum switchgear of 3.6 to 36 kV, it is on the order of P = 10 ^-3 Torr, and the withstand voltage and the breaking performance are not satisfied when the pressure is higher than that. In the conventional VST used in the atmosphere, the withstand voltage test voltage V ₁ for judging the quality of the vacuum is a voltage value capable of covering from this limit vacuum degree to the atmospheric pressure of the air, and the rated voltage 12
20 kV is standard for kV. But VST is SF
_When used in ₆ gases, since the discharge starting voltage is lower than air on the low pressure side on the left side of the Paschen minimum point, it is possible to judge whether the vacuum is good or bad by the test voltage V _1, and there is no problem. Moreover, as shown in the figure, since the discharge start voltage is higher than the test voltage V ₁ in the high pressure region of SF ₆ gas, the vacuum quality cannot be determined. Especially pressure P _T higher than atmospheric pressure
Therefore, even if a discharge occurs, it cannot be distinguished from a high vacuum. Voltage V
₂ is a voltage limiting voltage that should not be applied, because when this voltage is applied, it discharges in parts other than between the VST electrodes and threatens the insulator of the vacuum switchgear. Therefore, with the vacuum switchgear in which VST3 is stored in the container 1 in which the SF ₆ gas is sealed,
If a vacuum leak occurs and the VST is filled with SF ₆ gas with a filling pressure P _T in the sealed container 1, the standard withstanding voltage test method that has been widely used in the past cannot be adopted, and special measures are taken. is necessary.

In FIG. 9, when the opening distance is smaller than the full opening distance L _S , the characteristic of SF ₆ gas is that of the air of L _S = 8 mm because the entire V-shaped curve moves to the right almost horizontally. Get closer to the characteristics. On top of that, the conventional SF ₆ gas filling pressure P _T
Lower the pressure to bring it closer to atmospheric pressure, or devise the VST electrode to maintain high vacuum withstand voltage at a small opening distance.
It is possible that the conventional standard withstand voltage test method can be adopted by means such as lowering the withstand voltage of SF ₆ gas.

FIG. 10 is a conventional test circuit diagram showing a withstand voltage test method for VST used in the atmosphere, and is widely used because it is possible to easily and surely determine whether the vacuum switch is good or bad at the site where the vacuum switchgear is used. In FIG. 10, the same reference numerals indicate the same as in FIGS. Reference numeral 30 is a test device, which is composed of a high-voltage transformer 31, an ammeter 32 for detecting if VST discharges between electrodes, and 33 is an AC power supply. Now, when testing the vacuum quality of VST3, the vacuum switchgear is disconnected from the electric circuit in use, and the test device 30 is connected in the open state of L _{S at} the full open distance, and both electrodes 3
The presence or absence of inter-electrode discharge when the test voltage V ₁ = 20 kV is applied between a and 3b is detected by the ammeter 32, and the vacuum is judged to be defective or good. However, in the VST used in SF ₆ gas, there is a pressure range where the quality of the vacuum cannot be determined as described above. In the method proposed in Japanese Patent Laid-Open No. 62-208521, a constant high voltage is applied between VST electrodes,
The number of times the inter-electrode discharge occurs is measured over a certain period of time, the change in the number of discharges per unit time with respect to the elapsed time is observed, and the vacuum is judged to be good or bad according to the pattern of temporal decrease or increase. However, this method also has the drawback that it is complicated and requires skill.

Generally, in the periodic inspection of the vacuum switchgear performed every 6 years, in addition to the vacuum quality judgment, it is necessary to inspect the VST electrode consumption, the electrode contact resistance, and the three-phase VST opening / closing misalignment. is there. As the vacuum switchgear becomes more sophisticated and multifunctional, higher inspection reliability is required, but the demand is particularly strong for a device that is housed in the sealed container 1 and the VST 3 cannot be directly observed or touched from the outside. In addition, since the work of removing and installing the insulating material of the cable heads 4a and 4b is troublesome, it is desired to develop a vacuum switchgear that has excellent workability during inspection. Further, due to the demand for extension of the periodic inspection cycle, it is strongly expected that a vacuum switchgear will have a long vacuum service life even if a very small amount of vacuum leakage occurs.

[0007]

Since the conventional vacuum switchgear which uses VST in SF ₆ gas is constructed as described above, it is simple and reliable in the case of vacuum leakage and has been widely used in the past. In the withstanding voltage test method, there is a pressure range where the quality of the vacuum cannot be judged, and if the test voltage is increased, there is a risk that discharge will occur outside the VST pole and damage the insulator. In addition, since the inter-electrode discharge start voltage of the defective VST filled with SF ₆ gas is about the same, it is impossible to judge pass / fail. Even if a special test circuit is used, the test method is complicated and requires skill. In addition to the quality of the vacuum, it is necessary to attach and detach the insulating material of the cable head each time when various inspections are performed.

The present invention has been made in order to solve the above-mentioned problems, and a VST is provided in a container for sealing an insulating medium having both a pressure and a dielectric strength higher than atmospheric pressure air.
Various inspection tests such as vacuum quality, electrode wear, and electrode open / close irregularity can be performed easily and reliably at the installation site of the vacuum switchgear that houses the vacuum switchgear, and the inspection workability is excellent. Also aims to obtain a vacuum switchgear with a long vacuum life and high vacuum reliability.

[0009]

According to the present invention, there is provided a vacuum switch in which a VST having a vacuum dielectric strength of AC voltage of 20 kV or more at an opening distance of 1 mm is housed in a container for sealing an insulating medium.
Pressure and dielectric strength higher than atmospheric pressure air The dielectric strength between VST electrodes when the above-mentioned insulating medium is filled in VST is the maximum pressure at which the AC voltage is less than 20 kV at the opening distance of 1 mm or more, and the operating mechanism In addition, it is provided with an opening contact distance adjusting device that can reduce the opening contact distance from the fully opened position to the closed position. In addition, gas with a smaller molecular weight than SF ₆ gas and SF
_The insulating medium is composed of the mixed gas of ₆ gases and
The partial pressure of SF ₆ gas is limited to atmospheric pressure or less.

[0010]

The vacuum switchgear according to the present invention is provided with a contact opening distance adjusting device that can reduce the contact opening distance less than the full contact distance of the VST rating, so that the 20 kV withstand voltage that has been widely spread in the conventional manner in the reduced contact opening state. The vacuum quality can be determined by applying the test method, and the above vacuum quality can be determined by limiting the lower limit of the withstand voltage of the high vacuum VST and the upper limit of the withstand voltage of the VST filled with the insulating medium at the reduction opening of 1 mm. Make the judgment easier and more reliable. Further, the insulating medium is a mixed gas of a gas having a smaller molecular weight than that of SF ₆ gas and SF ₆ gas, and the partial pressure of SF ₆ gas in the mixed gas is limited to atmospheric pressure or less, whereby the discharge start voltage and VST
The dielectric strength on the low pressure side from the Paschen minimum point in the relationship curve with the internal pressure is improved, and the limit vacuum degree of VST used in SF ₆ gas is 10 ^-4 Torr VST when used in air
Enlarge to reach the critical vacuum of 10 ^-3 Torr.

[0011]

【Example】

Example 1. Embodiment 1 of the present invention will be described below with reference to the drawings. 1A and 1B show a vacuum switchgear provided with a contact opening distance adjusting device. FIG. 1A is a top view and FIG. 1B is a side view. FIG. 2 is a perspective view of the contact opening distance adjusting device. FIG. 3A is a vertical sectional view showing the electrode A of the first embodiment. FIG. 4 is a relationship diagram between the discharge starting voltage and the opening distance. The same reference numerals in FIG.
~ Equivalent to FIG. First, FIG. 1 is a vacuum switchgear breaker of the rated voltage 12 kV, low SF ₆ gas as an insulating medium in a sealed container 1 than the pressure P _T in the prior art Figure 8, at above atmospheric pressure in the pressure P _S It is hermetically sealed and has a rated full contact distance L
_S is a 8 mm, are shown adjustment completion state to the reduced opening distance L = L _V ~L _G for inspection test in FIG. The operation mechanism 10 is provided with an opening distance adjusting device 20 that can reduce the opening distance from the fully opened position to the closed position.

In FIGS. 1 and 2, reference numeral 21 is a contact plate having a hole in the central portion and abutting against the frame 8, 22 is a female screw in the central portion and is fixed to a drive lever 12 which is a part of the operating mechanism 10. A hook for hooking the pin 11 is a bolt, and 23 is a bolt which penetrates the hole of the contact plate 21 and engages with the female thread of the hook 22. When the bolt 23 is rotated to the right, the hook 22 is attracted so as to approach the contact plate 21, so that the pin 11, the drive lever 12, and the drive shaft 13 rotate about the center of the drive shaft 13 as a center of rotation. In the same manner as described in 8, the turning force is transmitted to the main shaft 16 and the movable electrode 3b can be moved in the closing direction. Conversely, when the bolt 23 is rotated counterclockwise, the opening spring force acts on the pin 11 as in FIG. 8, so that the movable electrode 3b moves in the opening direction. This opening distance adjusting device 20 is capable of finely adjusting the opening distance. The relationship between the rotation speed N of the bolt 23 and the change in the opening distance L is calibrated, and the movable electrode 3b is moved by a tester. While checking the conduction between the fixed electrode 3a and the fixed electrode 3a, the place where there is no conduction is set as the opening distance L = 0 mm, and the bolt 23 is set so that the opening distance L becomes an intermediate value between the reduced opening distances L _V and L _G described later. Rotate counterclockwise to complete the adjustment.

This opening distance adjusting device 20 can be attached to and detached from the operating mechanism 10, and in addition to the vacuum quality judgment test, when the vacuum is judged to be poor, the VST pressure is on the low pressure side on the Paschen curve in FIG. , Used to determine whether it is on the high pressure side,
Since it is used for various kinds of inspection tests such as measuring the amount of electrode wear or electrode misalignment between three phases, it can be removed under normal use of the vacuum switchgear. If the auxiliary spring 24 shown in FIG.
It is not necessary to detach the opening distance adjusting device 20 each time an inspection test is performed without moving the hook 22 away from the contact plate 21 by the spring force and hindering the rotation operation of the pin 11 and the drive lever 12 in the normal use state. Absent. The changeable range of the contact opening position by the contact opening distance adjusting device can be made larger than the rated full contact distance if necessary.

The opening distance L is defined as a distance L between L _V and L _G.
The vacuum switchgear adjusted to _V <L ≦ L _G is connected to the same withstand voltage tester 30 as in the conventional case as in FIG. 10, and the test voltage V ₁ = 20 kV is applied as in the conventional case. If VST3 is normal and the vacuum is high, no inter-electrode discharge occurs, and therefore only a small exciting current of the high voltage transformer 31 flows through the ammeter 32. Even if
If state VST3 is defective in SF ₆ gas is filled, the short-circuit current of the high voltage transformer 31 flows through the ammeter 32 standing is interpole discharge. Since the short-circuit current is orders of magnitude larger than the exciting current, it is possible to clearly discriminate the presence / absence of inter-electrode discharge of VST3. If it is determined that the vacuum is defective, the open-circuit distance is changed and the withstand voltage test is performed again. If the inter-electrode discharge disappears when the distance is increased, the VST pressure is the Paschen curve shown in FIG. If there is no inter-electrode discharge when the distance is shortened on the high pressure side, on the contrary, it is possible to determine that the vacuum state is on the low pressure side of the Paschen curve.

The electrodes 3a and 3b of the first embodiment are for a circuit breaker, and the electrode A equivalent to the conventional example is made of the material A, and its structure is shown in FIG. 3 (a). In FIG. 4 showing the discharge starting voltage characteristic of the electrode A, when the test voltage V ₁ is applied, the normal high vacuum VST is discharged at the opening distance L _V , and SF ₆ gas having a pressure P _S above atmospheric pressure is generated. The filled VST represents that discharge occurs at the opening distance L _G. L _V is about 1 mm and L _G is about 2.5 mm, and the difference is slight. In the vacuum quality judgment test, the greater the difference between L _G and L _V , the easier the test work and the higher the reliability of the quality judgment. Precise adjustment in the middle between L _G and L _V can be reliably performed by the opening distance adjusting device 20 shown in FIGS.

Example 2. FIG. 5 is a side view of a vacuum ring main unit having a rated voltage of 12 kV, and the same reference numerals are the same as those in FIG. The vacuum ring main unit is a switchgear installed in the power distribution network. In order to improve various checkability of the device, the test terminals 6a, 6b are provided on the atmosphere 7 side of the sealed container 1, and the switching disconnector 5a, 5b has a structure in which the VST electrodes 3a and 3b can be directly drawn to the outside. Further, since high withstand voltage performance is required, as shown in FIG. 3B, it is made of a material B having a higher withstand voltage than the breaker electrode A of the first embodiment. The test opening distance L _V ~L _G is opening distance adjusting device 20 are adjusted to shorter 1~2mm than Example 1. FIG. 4 is a relationship diagram between the discharge start voltage V and the opening distance L of the vacuum ring main unit in which the VST of the electrode B is housed in a container that seals SF ₆ gas at a pressure P _S above atmospheric pressure.
A comparison with the electrode A of Example 1 is shown. Test voltage V ₁ = 20kV
The open electrode distance L _G in the SF ₆ gas discharged at is shorter in the high withstand voltage electrode, and the distance difference between L _G and L _V is reduced to 1 mm. Actual vacuum quality judgment is performed at the intermediate distance between L _G and L _V , but even with such fine distance adjustment, the opening distance adjusting device
20 is possible. Further, the test voltage may be increased to increase the distance difference between L _G and L _V , but in the vacuum ring main unit, the test terminals 6a and 6b are exposed to the atmosphere 7, and the voltage limit voltage V ₂ is the same as the first embodiment and is economically inexpensive.

Embodiment 3. FIG. 3C is a sectional view showing the structure of the electrode C of the VST. Electrodes A and B are materials A and
While the electrode C in Example 3 is integrally formed with B, the electrode C in the third embodiment has the material C at the central portion of the electrode and the material A at the electrode peripheral portion.
It is composed of. In terms of materials, withstand voltage performance is highest in material B and lowest in material C. As shown in FIG. 6, the inter-electrode discharge starting voltage characteristic of the electrode C having the composite structure as described above is, as shown in FIG. 6, a region in which the opening distance is short when SF ₆ gas having a pressure P _S equal to or higher than the atmospheric pressure is filled in the VST. Therefore, the discharge starting voltage becomes particularly low. A region with a long opening distance for SF ₆ gas,
When the atmospheric pressure air is filled in the VST and when the VST is in a high vacuum, there is almost no difference from the discharge start voltage characteristic of the electrode A. According to the vacuum switchgear having an electrode such as the electrode C in which the electrode peripheral portion is made of a high withstand voltage material and the electrode central portion is made of a low withstand voltage material, a test contact opening distance L for determining the quality of the vacuum is obtained. _V is about 1 mm and L _G is about 5 mm. As can be seen from the discharge firing voltage characteristics in Fig. 6, L _V and L are lower than those of electrode A in which the electrode periphery and the electrode center are made of the same material.
_This has the effect of greatly expanding the distance difference from _G. Therefore,
The vacuum quality determination test becomes extremely simple, and the reliability of quality determination can be improved. If the electrode C having this composite structure is applied, it is possible to increase the gas pressure to the same value as the conventional gas pressure P _T.

Example 4. The discharge start voltage characteristic of Fig. 7 is SF
An example is shown in which VST is used in a mixed gas of SF ₆ gas and dry air instead of ₆ gas. Compared with the case of using SF ₆ gas alone, the test opening distance L _G is increased, and the distance difference from L _V can be enlarged. In addition, Paschen of Figure 9
By increasing the dielectric strength on the low pressure side from the minimum point, the range of the limit vacuum degree of VST can be expanded. Therefore, if VST causes a very small amount of vacuum leakage, there is an effect of extending the vacuum service life. In order to further increase this effect, the partial pressure of SF ₆ gas is 1 / the maximum pressure of 2 atm of the conventional example.
If it is set to 2, the vacuum service life can be doubled as compared with the conventional example. This is because the gas leak rate into the VST when a very small amount of vacuum leak occurs is proportional to the pressure outside the VST.

Example 5. The second gas mixed in the SF ₆ gas of Example 4 is not limited to dry air, and any gas having a molecular weight M smaller than 146 of SF ₆ may be used, and the dielectric strength on the low pressure side of the Paschen minimum point may be SF. Can be higher than ₆ gas. For example, N ₂ (molecular weight M = 28, and so on),
Carbonized fluorine gas such as CO ₂ (44) or CF ₄ (88) or noble gas such as He (4), Ne (20), A (40), Kr (83.8), Xe (131.3) As a mixed gas with SF ₆ gas, the total pressure is higher than atmospheric pressure, and the partial pressure of each component can be determined in the range where the dielectric strength on the high pressure side on the right side of the Paschen minimum point is higher than atmospheric pressure air. ..

Example 6. In the above embodiments, the case where the insulating medium around the VST is a gas containing SF ₆ gas has been described, but instead of these gases, for example, a silicon in a vacuum solid insulation switchgear or a vacuum load tap changer is used. When VST is used in liquid insulating medium such as oil or transformer oil, or liquid nitrogen, liquid hydrogen, or liquid helium in a vacuum switch for superconductivity, if VST causes a vacuum leak, it first enters as a gas. The vacuum switchgear provided with the above-mentioned opening contact distance adjusting device 20 can accurately determine whether the VST vacuum is good or bad.

[0021]

As described above, according to the present invention, the vacuum dielectric strength of the VST housed in the container for sealing the insulating medium is set to an opening voltage of 1 mm and an AC voltage of 20 kV or more.
The dielectric strength when filled in ST is the maximum pressure at which the opening distance is 1 mm or more and the AC voltage is less than 20 kV, and the opening distance of the operating mechanism can be reduced from the fully open position to the closed position. Since the adjusting device is provided, there is an effect that a vacuum switchgear having excellent workability of various inspection tests can be obtained while easily applying a conventional withstanding voltage test method to easily determine whether the vacuum is good or bad.

Further, since the insulating medium is a mixed gas of gas having a smaller molecular weight than SF ₆ gas and SF ₆ gas, and the partial pressure of SF ₆ gas in the mixed gas is limited to atmospheric pressure or less,
Even if a very small amount of vacuum leakage occurs, there is an effect that a vacuum switchgear that extends the vacuum service life of VST more than twice as long as the conventional one can be obtained.

[Brief description of drawings]

FIG. 1 (a) of a vacuum switchgear showing Embodiment 1 of the present invention.
Is a top view and (b) is a side view.

FIG. 2 is a perspective view of a contact opening distance adjusting device common to Embodiments 1 to 6 of the present invention.

FIG. 3 is a vertical cross-sectional view of electrodes of Examples 1 to 3 of the present invention, in which (a) shows Example 1, (b) shows Example 2, and (c) shows Example 3.

FIG. 4 is a diagram showing a relationship between a discharge starting voltage and an opening distance, which is common to the first and second embodiments of the present invention.

FIG. 5 is a side view of a vacuum switchgear according to a second embodiment of the present invention.

FIG. 6 is a relationship diagram of a discharge starting voltage and an opening distance according to a third embodiment of the present invention.

FIG. 7 is a relationship diagram of a discharge starting voltage and an opening distance according to a fourth embodiment of the present invention.

FIG. 8A is a top view and FIG. 8B is a side view of a conventional VCB.

FIG. 9 is a relationship diagram between a discharge start voltage and a VST internal pressure of a conventional vacuum switchgear.

FIG. 10 is a test circuit diagram showing a conventional withstand voltage test method for vacuum quality judgment.

[Explanation of symbols]

1 Sealed container 2 Insulating medium 3 Vacuum switch tube L _V Opening distance L _G Opening distance L _S Total closing distance P _S Maximum pressure 10 Operating mechanism 20 Opening distance adjusting device

Claims (2)

[Claims] 1. A vacuum switch tube having a vacuum dielectric strength of an AC voltage of 20 kV or more at an opening distance of 1 mm in a container that seals an insulating medium that is a gas or a liquid and has a higher pressure and dielectric strength than atmospheric pressure air. When the vacuum switch tube is housed and the insulating medium is filled, the interelectrode dielectric strength is the maximum pressure of the insulating medium at the opening distance of 1 mm or more and the AC voltage is less than 20 kV, and the opening distance is at the fully open position. The vacuum switchgear is characterized in that the operating mechanism is provided with an opening distance adjusting device that can be reduced from the closing position to the closing position. Wherein accommodating the vacuum switch tube total pressure and dielectric strength to seal the high gas mixture than air at atmospheric pressure in the container, the mixed gas with a small gas and SF ₆ gas molecular weight than SF ₆ gas A vacuum switching device characterized in that the partial pressure of the SF ₆ gas is limited to atmospheric pressure or less.