JPH01204327A - Circuit breaker - Google Patents

Abstract

PURPOSE:To let satisfactory actions be taken for possible failures, thereby enable an electric power system to be operated rationally and economically by utilizing super conductive wires having circuit limiting action, detecting change in magnetic field by a magnetic filed detecting mechanisms, and thereby disconnecting not only failed lines but also normal lines based on said detection. CONSTITUTION:Those such as super conductive lines G connecting the lines of an electric power system, a magnetic field detecting mechanisms 30 detecting change in magnetic field produced around the super conductive lines G, and disconnecting mechanisms 21 through 24 disconnecting lines depending on change in magnetic field detected by the magnetic field detecting mechanism 30 are provided. When great amperage current flows into the super conductive lines G through wires 10 because of irregularities such as short circuiting and grounding taking place in the electric line of one phase out of three phases for some reasons, the super conductive phase of the super conductive lines G is thereby destroyed. In addition, as the super conductive lines G are transformed into non-super conductive conditional material, and concurrently the switch 24 of a burn-out mechanism mounted on the electric wire 10 of a normal phase is opened. And all phases of one circuit in the range of failures are completely disconnected with all switches 24 opened. This constitution thereby allows safety for operators to be secured for repair works and the like in the range of the failures.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a disconnection device installed on a power system line,
In detail, when an excessive current that exceeds the rating flows in a superconducting wire that is a current limiting line connected to a power transmission line buried underground in a power system, not only the faulty line where the excessive current flowed but also the excessive current flowing. This relates to a disconnection device that disconnects normal railway lines from the railway line.

[Conventional technology]

In general, an electric power system is a system that integrates everything from generation to consumption of electric power, that is, it generates electricity at a power plant, transmits it through transmission lines, and then distributes it to factories and homes using distribution lines, and then distributes it to the load equipment. It refers to the system that includes everything up to. Electric power transported by transmission lines cannot be suddenly supplied to consumers at the same transmission voltage, so the voltage must be stepped down several times to a voltage that is suitable for the demand load.

In a grid-connected power system, if an accident occurs somewhere along the lines, the effects will immediately spread to the entire region. Therefore, even if an accident occurs, it is extremely important to suppress its effects locally and prevent it from spreading to other areas, from the standpoint of maintenance and safety, as well as from the standpoint of ensuring a constant supply of power.

There are many types of accidents that occur on power transmission lines, but they include abnormal voltage generation due to lightning strikes, and excessive current flowing due to line short circuits and ground faults. For this reason, to protect against abnormal voltages, overhead ground wires or buried ground wires are installed on power transmission lines to protect the lines, and various types of lightning arresters are installed near the entrances or exits of the lines at power plants and substations. , when abnormal voltage waves attack, they are temporarily grounded and guided to the earth in an effort to prevent insulation breakdown in electrical facilities. In addition, if a power line is short-circuited or grounded due to disconnection or contact, a strong current will flow to the fault location and burn out the electrical equipment in the circuit, so as a measure to prepare for such an unexpected situation, certain sections of the line A current limiting line may be provided for each area. This is to prevent the effects of an accident from spreading by cutting off the faulty section and cutting off the current by the current-limiting action of the current-limiting wire at the same time that a large current flows through the line.

Such current-limiting wires are usually constructed as electric wires by covering a conductor with a current-limiting function with an insulating coating,
There are superconducting wires made of metallic superconducting materials, and superconducting wires made of ceramic superconducting materials previously proposed by the present inventor (see Japanese Patent Application No. 62-248935).

Of these, apart from electric wires that are normal conductors, superconducting wires made of metal or ceramic superconducting materials have no electrical resistance at all due to their superconducting state and allow current to flow without loss during normal times, but due to large currents in the event of an accident, It is characterized by immediately transitioning from a superconductor to an insulator to perform a current limiting action. In other words, the critical current of the superconducting wire is preset according to the allowable current of the line (for example, in the case of the main line of a distribution system line, the voltage is 600 V and the allowable current is 20,000 A, so the critical current is 20,000 A).
When the fault current reaches this level, the superconducting phase of the superconducting wire breaks down, instantly transitioning from a superconductor to an insulator, cutting off the large current.

[Problem to be solved by the invention]

By the way, in electric power systems, single-phase alternating current is generally used exclusively for small consumers such as households, and three-phase alternating current is used exclusively for other large consumers and power transmission systems.

Single-phase AC is normally supplied using Miki wires (or cables) (three wires for a single-phase three-wire system), and three-phase AC is supplied using three wires (or cables) (four wires for a three-phase four-wire system). are doing.

Superconducting wires are connected to each wire on these lines as current-limiting wires to cut off excessive currents caused by accidents, but in the majority of cases accidents such as short circuits and ground faults occur only in one wire. .

In this case, if we take three-phase AC as an example, a large fault current will flow in one of the three phases of one line, and the superconducting wire will transition from the superconductor to the insulator, cutting off the large current and removing the fault phase. Even if it is disconnected, the other two phases are normal and will continue to supply power. However, in order to bring the accident under control, it is important to immediately investigate the cause of the accident and begin restoration work, in order to ensure continuous power supply and protect the operators of electrical facilities from electric shocks. For this purpose, the superconducting wire used as a current-limiting line on the line exerts a current-limiting effect with a large current and disconnects the faulty phase, and at the same time disconnects the healthy phases connected to other superconducting wires and connects one circuit in the faulty section. It is essential to have a device that blocks the gold phase.

Furthermore, as the demand load increases with the development of industry, the power system will gradually expand in scale and become more complex due to the development of power sources and the reinforcement of facilities. Electricity companies provide an abundance of high-quality electricity,
In order to be able to supply electricity at a low cost, the entire power system must always be operated rationally and economically, and it is essential to minimize the total cost of electricity supplied to the loads.

Therefore, in view of the above points, it is an object of the present invention to provide a device which, when a superconducting wire connected to a power system line as a current limiting line disconnects a faulty phase by current limiting action, also disconnects other healthy phases at the same time. There is a particular thing.

[Means to solve the problem]

The purpose is to provide a superconducting wire that has a current-limiting effect for connection to power system lines, a magnetic field detection mechanism that detects changes in the magnetic field generated around the superconducting wire, and a magnetic field detection mechanism that detects changes in the magnetic field detected by the magnetic field detection mechanism. This is achieved by a disconnection device characterized in that it is equipped with a disconnection mechanism that disconnects the line accordingly.

The interrupting device of the present invention uses a superconducting wire that has a current-limiting effect, and during normal times when no fault current is flowing through the line, the superconducting wire is a superconductor and can transmit power without loss, allowing excessive current to flow through the line. At the same time, the superconducting wire performs a current limiting action, and the disconnection mechanism disconnects the faulty line to which the superconducting wire is connected. At the same time, the magnetic field detection mechanism detects changes in the magnetic field around the superconducting wire due to the current interruption. Accordingly, the disconnection mechanism attached to the normal line is linked, and the line is forcibly disconnected even if the superconducting wire of the normal line is a superconductor.

As is well known, when a current passes through an electric wire (or cable), a magnetic field is generated around it. Regardless of whether it is single-phase AC or three-phase AC, when the rated current is flowing through the wires, the magnetic field generated around each wire is of the same strength, but when the current in one wire is interrupted, the magnetic field generated by all the wires is the same. The resultant magnetic field changes. In the interrupting device of the present invention, this magnetic field change is detected by a magnetic field detection mechanism, and the current in the electric wires of all the circuits is interrupted.

There is no particular limitation on the magnetic field detection mechanism used in such a cutoff device, and for example, a well-known magnetic field detection mechanism or element may be used.

Further, as the material of the superconducting wire connected to the line as a current limiting wire, there are metal-based or ceramic-based superconducting materials. Metal-based superconducting materials include niobium, titanium, zirconium, vanadium, tantalum, etc. Ceramic superconducting materials or mixtures of their raw materials are not particularly limited, but must be ceramic materials containing rare earth element oxides. is preferred. Existing materials may be used as such materials, but for example, the material components include barium, yttrium, copper, and oxygen, barium, lanthanum, copper, and oxygen, strontium, lanthanum, copper, and oxygen, barium, scandium, copper, and oxygen. There are ceramics whose composition is oxygen, calcium, lanthanum, copper, and oxygen.
Preferably, it is a material having a composition of barium, yttrium, copper, and oxygen, which is a yttrium-based material that is becoming mainstream in ceramic materials. Furthermore, when using this yttrium-based superconducting material, the preferred blending ratio is Ba:
Y:Cu:O=2:1:3:6~7
It is.

The superconducting wire can be manufactured using conventional methods using the metal or ceramic superconducting materials mentioned above. It is necessary to set the current appropriately.

For example, in the main line of a power distribution system, which is a part of the power system that is directly connected to supply electricity to consumers, the rated current of the main line is 600 A and the breaking current is 20,000 A. In other words, the main wire is a superconducting wire with a cross-sectional area such that at 20,000 A, a critical current is generated and the current is transferred from the superconductor to the insulator, resulting in a current-limiting effect. In addition, superconducting wires utilize the characteristics of both superconductors and insulators, but since ceramic materials are originally excellent insulators, it is necessary to obtain more desirable power supply blocking through insulating conditions during abnormal conditions. Preferably, the superconducting wire is made of a ceramic superconducting material.

〔Example〕

EMBODIMENT OF THE INVENTION Hereinafter, the shutoff device of this invention will be concretely demonstrated based on an Example.

FIG. 1 shows a schematic circuit of one embodiment. The figure shows a three-phase, three-wire system with three-phase AC, and one line of three electric wires 10 (or cables) is connected to a power transmission line buried underground.
A shutoff device BR is installed. A superconducting wire G having a current limiting effect is connected to each electric wire 10, and a disconnection mechanism for disconnecting the electric wire 10 is also attached. As is clear from the figure, the disconnection mechanism includes a shunt resistor r connected to the electric wire 10, a coil 21 connected in series to the shunt resistor r, and an iron rod inserted into the coil 21 and displaced as it is energized and demagnetized. 22, a coil spring 23 attached to the end of the iron rod 22;
and a switch 24 that opens and closes the electric wire 10 according to the displacement of the iron rod 22. However, it is preferable that the disconnection mechanism is provided with an additional mechanism for fixing the switch 24 in an open state, if necessary. As shown in FIG. 2, the superconducting wires G are arranged at the vertices of an equilateral triangle so as to be equidistant from each other, and an arbitrary magnetic field detection mechanism 30 among the above examples is arranged at the center of gravity of the equilateral triangle. The magnetic field detection mechanism 30 and the disconnection mechanism are connected by a suitable interlocking mechanism 31 in order to operate the disconnection mechanism according to changes in the magnetic field generated around the superconducting wire G detected by the magnetic field detection mechanism 30.

The superconducting wire G, whether metal-based or ceramic-based, depends on the critical temperature of the superconducting material, but in order to maintain its superconducting state, it is housed in a cooling tank 40 containing a coolant and constantly cooled. has been done.

The electromotive conductor G used for the interrupter BR is normally placed in the cooling tank 4.
Since the superconducting wire G is placed in a coolant (for example, liquid nitrogen) within the temperature range, a waterproof layer is provided to protect the superconducting wire G from water.
Although it is not necessary to provide a waterproof layer, it is desirable to provide a waterproof layer when using at room temperature without cooling with a coolant.

In the circuit breaker BR having such a structure, when the normal current I is supplied, the superconducting wire G is a superconductor and has no electrical resistance, so no Joule heat is generated, and therefore there is no transmission loss. In addition, under normal conditions, the current shunted from the wire 10 by the shunt resistor r flows through the coil 21.
is excited, the iron rod 22 overcomes the biasing force of the coil spring 23 and is displaced in the direction of the arrow, and the switch 24 is in a closed state.

At this time, a magnetic field of the same strength is generated around each superconducting wire G by the current l passing through each superconducting wire G. However, since the magnetic field detection mechanism 30 is located at the center of gravity of the equilateral triangle, that is, at an equal distance from each superconducting wire G, the generated magnetic fields cancel each other out at this point, and the resultant magnetic field is zero.

Therefore, naturally, no change in the magnetic field occurs.

If an abnormality such as a short circuit or ground fault occurs in the electric line of one of the three phases for some reason and a large current flows into the superconducting wire G through the electric wire IO, the superconducting wire G will be affected by the current exceeding the magnetic field current. The superconducting phase breaks down and instantly transitions from a superconductor to an insulator, which is the original property of ceramic materials.
Immediately interrupt excessive current. Simultaneously with the current limiting action of the superconducting wire G, no current flows through the shunt resistor r, the coil 21 is demagnetized, the iron bar 22 is displaced in the direction of arrow A by the restoring force of the coil spring 23, and the switch 24 is opened and the wire 10 is disconnected. By disconnecting the electric wire 10, the electric wire 1
It is also possible to prevent the backflow of zero current. Since the superconducting wire G becomes an insulator after the current limiting action, the possibility of current backflow is extremely small, but this is a measure to be taken in case of an emergency.

Furthermore, at the same time as the superconducting wire G transitions to the insulator, the current in the fault phase is cut off, so that the magnetic field generated around the superconducting wire G in the fault phase disappears. As a result, the composite magnetic field, which was 0 at the placement point of the magnetic field detection mechanism 30, changes, and the magnetic field detection mechanism 30 detects this, and the interlocking mechanism 31 operates according to the detection signal, and attaches it to the electric wire 10 of the healthy phase. Open the switch 24 of the disconnection mechanism. By opening all the switches 24, all phases of one line in the section where the accident occurred are completely disconnected, and safety for workers working on restoration of the section is guaranteed.

Note that it is preferable that the disconnection mechanism of the above-mentioned disconnection device BR is provided with an additional mechanism that can easily visually confirm that the electric wire 10 is in the disconnected state. This is a multiple measure to protect people operating electrical facilities during restoration work from the risk of electric shock. Further, the structure of the disconnection mechanism may be completely different from that shown in the above embodiment.

(Effects of the Invention) As explained above, the interrupting device of the present invention uses a current-limiting conductive wire, detects changes in the magnetic field generated around this superconducting wire by a magnetic field detection mechanism, and detects changes in the magnetic field generated around the superconducting wire. By blocking not only the accident track but also the normal track,
It is possible to simultaneously and completely disconnect all single-phase AC or three-phase AC power lines in the section where the accident occurred, providing a complete measure against accidents and making it possible to operate the power system rationally and economically. be.

[Brief explanation of the drawing]

Fig. 1 is a schematic circuit diagram showing an example of how the interrupting device of the present invention is attached to each three-phase AC electric line in a power system, and Fig. 2 illustrates the arrangement of the superconducting wire and magnetic field detection mechanism of the interrupting device of Fig. 1. FIG. BR: Breaking device G: Superconducting wire r: Shunt resistor 10: Electric wire 21: Coil 22: Iron rod 23: Coil spring 24: Switch 30: Magnetic field detection mechanism 31: Interlocking mechanism 40: Cooling tank N')N') L- 1−−−= +−＋＋＋−+ J procedural amendment (
Self-button

Claims (2)

[Claims] (1) A superconducting wire that has a current-limiting effect for connecting to power system lines, a magnetic field detection mechanism that detects changes in the magnetic field generated around the superconducting wire, and a magnetic field detection mechanism that responds to changes in the magnetic field detected by the magnetic field detection mechanism. A disconnection device characterized by comprising a disconnection mechanism that disconnects a line by using a disconnection mechanism. (2) The line is a three-phase alternating current, the superconducting wires connected to each phase are arranged at the vertices of an equilateral triangle so that they are equidistant from each other, and the magnetic field detection mechanism is arranged at the center of gravity of the equilateral triangle. The shutoff device according to claim (1).