JPH04179017A - Vacuum switch with current limiting element - Google Patents

Abstract

PURPOSE:To facilitate current interruption by winding a plural pair of superconductive coils having a required critical current value around an insulating body rod with their coiling directions of right or left reverse to each other's, and connecting a current limiting element in which respective superconductive coils are mutually connected in parallel, to the contact of a vacuum switch in series. CONSTITUTION:Superconductive coils 8c, 8d are coiled around the same outer circumference part of an insulating body rod 8e with their coiling directions of right or left reverse to each other's so as to reduce each other's magnetomotive force. A current limiting element 8 is constructed by connecting the coils 8c, 8d in parallel and integratedly positioned in a switch 12 so as to be serial with the contacts of vacuum switches 2, 3. Thus, the element 8 is in a superconductive state as its stationary state and its impedance is approximately zero because of the inductionless coiling so that it can be normally load-fed in accordance with a close of contacts of the vacuum switch. However, when a load short-circuit or the like occurs and an excessive current flows, the element 8 gets quenched and transforms itself into a high resistance body. An electric circuit and a circuit apparatus can thus securely be protected from a short-circuit accident and an interrupting current which is shared by a switching device can be reduced.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) This invention relates to a vacuum switch used for opening and closing high-voltage, large-current paths. A current-limiting element that utilizes the phenomenon of transfer to a normal conductor (
The present invention relates to an improvement of a vacuum switch equipped with a current suppressing element)).

(Prior Art) When a three-phase short circuit or ground fault occurs in an AC line such as a power distribution line, a fault current of several tens of kA flows, causing great damage to the system and equipment. Vacuum switches are designed to interrupt such fault currents within a few cycles, and are constructed by arranging both movable and fixed forces facing each other in a cylindrical vacuum insulating container, and moving the movable electrode back and forth in the axial direction. The contacts are opened and closed by operation.

On the other hand, in recent power distribution systems, fault current is quickly limited to a predetermined value in order to reliably protect electrical circuits and circuit equipment from short-circuit accidents and to reduce as much as possible the breaking current borne by switchgear. It is desired to realize a compact and simple current-limiting element or a current-limiting switch that can allow current to flow. In response to such a demand, a vacuum switch with a current limiting element as shown in Japanese Patent Application Laid-Open No. 01-159921 has been devised.

This prior art is constructed as shown in FIG.

In FIG. 6, ] is a vacuum vessel, 2 is a movable electrode, 3 is a fixed electrode, 4 is a shield, 5 is a bellows, and 6 is a fixed terminal. Then, first and second superconducting coils 10 and 11 having different critical current values are wound in series with each other so as to be almost non-inductive on the rod extending from the fixed terminal 6 to the fixed electrode 3, and this is used as a current limiting element. A current limiting element is arranged in series with the fixed electrode 3.

In this configuration, both coils maintain superconductivity up to a predetermined current level, and the magnetomotive forces of the coils cancel each other out, resulting in a non-inductive state, so they act as low-impedance elements and do not affect the circuit. When an overcurrent flows, the second superconducting coil 11 quenches and becomes a high-resistance body, while the first coil 10 becomes a superconducting reactor and suppresses the overcurrent.

(Problems to be Solved by the Invention) However, the above-described conventional vacuum switch with a current-limiting element has the following problems.

(1) Because the reactor operates, it is difficult for a vacuum switch to interrupt the current.

(2) Due to reactor operation, it is difficult to obtain a high current limiting impedance.

(3) Difficult to apply to DC circuits due to reactor operation.

(4) Due to the coil configuration, the magnetic flux cancellation rate between the superconducting coils is low (approximately 50%) and the steady-state inductance is large.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a vacuum switch with a resistance-operated current limiting function that can reduce steady-state impedance and can be used for both alternating current and direct current.

[Structure of the invention]

(Means for solving the problem) Therefore, in this invention, a plurality of sets of superconducting coils having a predetermined critical current value are wound around the same outer circumferential portion of the insulator opening and the opposite left and right so that their magnetomotive forces cancel each other out. The superconducting coils were connected in parallel to form a current-limiting element, and this current-limiting element was integrally attached within the sui-nochi so as to be in series with the contacts of the vacuum switch.

(Function) The current limiting element according to the present invention is in a superconducting state in a steady state and is non-inductively wound, so its impedance is approximately zero.

Therefore, by closing the vacuum switch contact, the load can be normally supplied with power. However, when a load short circuit occurs and overcurrent flows through the circuit, the current limiting element quenches and transfers to a high resistance element. As a result, the fault current is limited, and then the vacuum switch opens to interrupt the circuit. As a result, the current limiting element is cooled down and restores superconductivity after a predetermined period of time. Therefore, it becomes possible to easily restart load power supply by closing the vacuum switch when the accident is resolved.

(Embodiment) FIG. 1 shows the configuration of a vacuum switch according to an embodiment of the present invention. In FIG. 1, 1 is a vacuum container, 2 is a movable electrode,
Reference numeral 3 represents a fixed electrode, 4 a shield, 5 a bellows, 6 a fixed terminal, 7 an insulating tube, 8 a current limiting element, and 9 a cooling medium flow path (not shown).

FIG. 2 is a diagram showing the detailed configuration of the current limiting element section 8 in the configuration of FIG. 1, in which 8a and 8b are electrodes, 8C is a right-handed superconducting coil, 8d is a left-handed superconducting coil, and 8e is an insulating rod. In this configuration example, the current limiting element 8 includes an insulating rod 8e, superconducting coils 8c and 8d having a predetermined critical current value and wound around the insulating rod 8e in left and right opposite directions, and superconducting coils 8c and 8d. It consists of electrodes 8a and 8b for connecting both coils in parallel by short-circuiting both ends.

FIG. 3 is a diagram showing the current-carrying current versus impedance characteristics of the current-limiting element 8. The impedance of the superconducting coils 8c and 8d is zero when the critical current is below IC1, and when the current exceeds ICI, the superconducting coils 8c and 8d are quenched and become high-resistance elements. It is set to be. In other words, this vacuum switch has the function of opening and closing the contacts by reciprocating the movable electrode 2 in the axial direction by an operation mechanism (not shown), and also has the function of opening and closing the contacts by moving the movable electrode 2 back and forth in the axial direction by an operation mechanism (not shown). Current limiting element 8
has the function of activating (quenching) and transferring to a high impedance element.

FIG. 4 is a diagram showing an example of a circuit in which the element of the present invention is used, in which a vacuum switch 12 of the present invention and a load 13 are connected in series to a power source 14. FIG. 5 is a diagram showing the circuit current waveform and the resistance change of the vacuum switch 12 in the steady state and when a load short circuit occurs in the circuit of FIG. 4, and the operation of the vacuum switch of the present invention will be explained using these diagrams. do.

Now, when the vacuum switch 12 is closed and the load 13 is in a normal state, the current limiting element 8 of the vacuum switch 1 is in a superconducting state, so its impedance is almost zero, so it does not affect the circuit in any way, and the current limiting element 8 is in a normal state. Continue load power supply. Next, load 1
3, a short circuit occurs and fault current flows (point "a" in Figure 5)
, when the value exceeds the critical current value (ICI) of the current limiting element 8, the superconducting coils 8c and 8d are quenched and transformed into high resistance elements. Since the resistance value rises due to this quenching is extremely steep, the short circuit current is instantly suppressed to a predetermined value (point "b" in FIG. 5). Thereafter, an operation mechanism (not shown) opens the movable electrode 2 of the vacuum switch 12 to interrupt the short circuit (point "C" in FIG. 5).

Note that since the current limiting at this time is substantially performed by the resistance of the current limiting element 8, the circuit power factor is close to 1, and the vacuum switch 12 can be shut off extremely easily compared to a conventional inductance circuit. Become. As described above, the fault current is instantaneously limited to a predetermined value and cut off by the current limiting element 8.

Moreover, when a superconductor is cooled, it returns to superconductivity in a relatively short time.

Therefore, after the current limiting element 8 has completely cooled down, the vacuum switch 12
When the circuit is closed, the circuit returns to a steady state.

In addition, in the above embodiment, the superconducting coil is placed outside the vacuum chamber, and the superconductor is directly cooled by the cooling medium, so more stable characteristics against disturbances can be obtained, and the time required for the superconductor to return after quenching can be shortened. It has the effect of

In addition, in the above-mentioned embodiment, the current limiting element 8 was arranged on the fixed contact side, but it can also be arranged on the movable contact side with a similar structure.
Alternatively, it is also possible to further enhance the current limiting effect by disposing them on both sides.

〔Effect of the invention〕

The vacuum switch with current limiting element of the present invention has the following effects compared to the prior art.

(1) Resistance current limiting makes it easy to interrupt current and extend contact life.

(2) High current-limiting impedance (quench resistance) because the superconductor is configured in a spiral shape and the coil length can be increased.
is obtained.

(3) Can be applied to DC circuits due to resistance current limiting.

(4) Since the left and right superconducting coils are placed close to each other, the magnetic flux cancellation rate is high and the steady inductance is small.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram of a vacuum switch with a current-limiting element according to an embodiment of the present invention, FIG. 2 is a perspective view showing the detailed configuration of the current-limiting element in the same embodiment, and FIG. 3 is a diagram showing the upper limit current of the same. Figure 4 is a circuit diagram of an example of the use of a vacuum switch with the same upper flow element; Figure 5 is a diagram showing the operating characteristics of the vacuum switch in the circuit of Figure 4; Figure 6 is a diagram showing the impedance characteristics of the element versus current. It is a block diagram of the conventional vacuum switch with a current limiting element. DESCRIPTION OF SYMBOLS 1... Vacuum container, 2... Movable electrode, 3... Fixed electrode, 4... Shield, 5... Bellows, 6... Fixed terminal, 7... Insulating cylinder, 8... - Current limiting element, 9... Cooling channel, 8a, 8b... Electrode, 8c... Right-handed superconducting coil, 8d... Left-handed superconducting coil, 8e... Insulating rod, 12... Vacuum switch with current limiting element, 13...Load, 14...Power supply.

Claims (1)

[Claims] A plurality of sets of superconducting coils each having a predetermined critical current value are wound around the same outer circumferential portion of an insulating rod in left and right reverse windings so that their magnetomotive forces cancel each other out, and each superconducting coil is connected in parallel. A vacuum switch with a current-limiting element, characterized in that the current-limiting element is integrally attached so as to be connected in series with the contacts of the vacuum switch.