JPH01286733A - Current limiting unit - Google Patents

Abstract

PURPOSE:To reduce the cost of a current limiting device by employing a superconducting lead made of a ceramic superconducting material as a current limiting wire, and providing a bypass at the time of shifting to a quenching state. CONSTITUTION:A current limiting unit G1 has a current limiting wire 10 of a superconducting lead made of a ceramic superconducting material, a conductive cooling tank 11 in which cooling refrigerant 12 is filled, and a heat insulating tank 13. Current limiting wire terminals 15 are attached to both ends of the wire 10, and unit terminals 16 for connecting to a line 60 are attached thereto. Terminals 18, 19 each having resistance are attached to opposite positions through an insulator 17 on one and the other faces of the tank 11. A fuse 20 is mounted between both the terminals. Thus, when a large current flows to a line 50 due to a malfunction such as a short-circuit or the like, the wire 10 of the unit G1 is shifted from a superconductor to a quenching state, a current flows to a fuse circuit having a resistance R, thereby reducing the current.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is installed on the lines of a power system to suppress the flow of excessive current when an excessive current exceeding the rating flows through the line. The present invention relates to a current limiting unit that restarts energization of a line after extinction.

[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. Electric power transported by transmission lines cannot be suddenly supplied to consumers at the same transmission voltage, so the voltage must be adjusted to a shallow level or suitable for the demand load by then. have to descend.

In a power system connected in the form of a cable, if an accident occurs somewhere along the line, 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 metal-based superconducting materials and superconducting wires made of ceramic-based superconducting materials proposed by the present inventors.

Apart from electric wires that are normal conductors, superconducting wires made of metallic or ceramic superconducting materials have no electrical resistance at all due to their superconducting state during normal times (current flows without loss, but large currents in the event of an accident It is characterized by the fact that it shifts from a superconductor to a non-superconductor in a short time and performs a current limiting action.In other words, the critical current of a superconducting wire (for example, the main line of a distribution system line) is set in advance according to the allowable current of the line. In the case of , the voltage is 600■ and the allowable current is 20,000A, so the critical current is 2
When a fault current reaches more than 10,000 A), the superconducting phase of the superconducting wire breaks down, transitioning from a superconductor to a non-superconductor in a short period of time, interrupting the large current.

[Problem to be solved by the invention]

Current-limiting wires made of ceramic-based superconducting materials utilize the inherent characteristics of ceramic materials as high electrical resistors, that is, as both non-superconductors and superconductors. It also has an excellent current limiting effect.

By the way, in general, superconducting wires made of ceramic-based superconducting materials exhibit a quench phenomenon in which the superconducting state is destroyed by an excessive current larger than the critical current, and the entire superconductor becomes a normal conductor in a short time. Superconductors generally exhibit high resistance during transition, and this high resistance generates Joule heat, which may eventually burn out the superconducting wire.

Therefore, when a superconducting wire made of a ceramic superconducting material is used as a current limiting wire, it is desirable to take measures to prevent the wire from burning out even if the superconducting wire becomes quenched due to excessive current.

Furthermore, if 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 abundant electricity in Ryoga,
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.

From this standpoint, it is desired that the cost of a current limiting device using a superconducting wire as a current limiting wire be reduced as much as possible and that it can be easily installed on power system lines.

Therefore, in view of the above points, an object of the present invention is to use a superconducting wire made of ceramic superconducting material as a current limiting wire,
To provide a current limiting unit which does not have the risk of being burnt out even if a vJA streamline shifts to a quench state due to a large 1ttX, and can be easily installed on a power system line.

[Means to solve the problem]

In order to achieve the above object, the current limiting unit of the present invention includes:
A superconducting wire made of ceramic superconducting material is used as a current limiting wire and can be easily installed on power system lines, and has a bypass that detours the current when the superconducting wire transitions from a superconductor to a quench state due to large current. However, by bypassing, the current is suppressed to a level that does not damage the load equipment.

In other words, the current limiting unit attaches a unit terminal for line connection to a superconducting wire, places the superconducting wire in a conductive cooling tank in such a way that the unit terminal penetrates the cooling tank, and connects the cooling tank and the unit terminal electrically. The cooling tank is divided into one part and the other part by an insulator provided in the cooling tank, terminals with resistance are attached to the outer surface of one part of the cooling tank, and terminals with resistance are installed to the outer surface of the other part, respectively, and a fuse is connected between both terminals. It is characterized by being constructed.

Further, a current limiting unit without a fuse is characterized in that the cooling tank is electrically conductive and has resistance so that the cooling tank itself can be used as a bypass without dividing the cooling tank into two by an insulator.

In a current limiting unit equipped with a fuse, the superconducting wire is in a superconducting state under normal conditions and there is no transmission loss, but when a large current flows due to an accident, the superconducting phase is destroyed by the excessive current, so the superconducting wire is in a quench state for a short time. to move to. At the same time as the superconducting wire transitions to the quench state, from the upstream unit terminal to one part of the conductive cooling tank, the terminal attached to that one part, the fuse, the terminal attached to the other part of the cooling tank, and the other part of the cooling tank A bypass is formed that connects to the unit terminal on the downstream side, and the excessive current is throttled by both terminals having a resistor attached to the cooling tank.

Furthermore, in a current limiting unit that does not include a fuse, a conductive cooling tank is used as a detour, and since the cooling tank itself has resistance, the excessive current is throttled by the cooling tank.

There is no particular restriction on the ceramic superconducting material of the superconducting wire used as the current limiting wire in the current limiting unit of the present invention. For example, oxide ceramic materials containing rare earth elements include barium, yttrium, copper, oxygen, barium, lanthanum, Copper/oxygen, strontium/lanthanum/copper/oxygen,
Ceramics with compositions of barium, scandium, copper, oxygen, calcium, lanthanum, copper, oxygen, etc. Examples of oxide ceramic materials that do not contain rare earth elements include ceramics with compositions of bismuth, strontium, calcium, copper, and oxygen. be done.

The superconducting wire can be manufactured using conventional methods using the ceramic superconducting materials mentioned above, but the critical current when the superconducting phase of the superconducting wire is destroyed and the superconducting wire transitions from an electromotive conductor to a quench state is It is necessary to set it appropriately. For example, in the main line of the distribution system, which is a two-part power system that is directly connected to consumers and supplies electricity, the rated current of the main line is 60
The breaking current is 20,000 A at 0 A. In other words, a superconducting wire with a cross-sectional area such that at 20,000 A, a critical current is generated, the electromotive conductor changes to a quench state, and a current-limiting action appears.

〔Example〕

EMBODIMENT OF THE INVENTION Hereinafter, the current limiting unit of this invention is demonstrated based on an Example.

Figure 1 shows an example of a current limiting unit.
It is equipped with. The current limiting unit G1 is a superconducting wire made of ceramic superconducting material, that is, a current limiting wire lO
, a conductive cooling tank 11 containing a cooling medium (for example, liquid nitrogen) 12, and a cooling tank 1 for efficient cooling.
1 and a heat-retaining tank 13 with a heat-retaining layer 14 interposed therebetween. Current-limiting line terminals 15 are attached to both ends of the current-limiting line 10, and unit terminals 16 for connecting to the line 50 are attached to the current-limiting line terminals 15. The current limiting wire 10 is arranged in the cooling tank 11 in such a manner that the unit terminal 16 penetrates the cooling tank 11 in order to maintain the superconducting state, although it varies depending on the critical temperature of the ceramic superconducting material. and the unit terminal 16 are electrically connected.

Further, the cooling tank 11 is housed within the heat-retaining tank 13 , and the unit terminal 16 penetrates through the heat-retaining tank 13 and protrudes to the outside of the heat-retaining tank 13 . The cooling tank 11 is divided into one part and the other part by an insulator 17 provided in the cooling tank 11, and the cooling tank 11 is connected from the upstream unit terminal to the downstream unit terminal.
No current can flow through it. Cooling tank 11
Terminals 18 and 19 having resistance are respectively attached to the outer surface of one part and the outer surface of the other part at opposite positions with the insulator 17 in between, and extend through the heat-retaining tank 13 and projecting to the outside of the heat-retaining tank 13. A fuse 20 is installed between these terminals 18 and 19.

As is clear from the figure, the current limiting wire 10 has a metal thin layer 22 formed around a superconductor 21 made of a ceramic superconducting material by wire drawing during the manufacturing process. Here, the current limiting line 10 usually refers to the cooling medium 12 in the cooling tank 11.
Since it is inserted inside, there is no need to provide a waterproof layer such as a thin metal layer 22 on the current limiting line 10 to protect the current limiting line 10 from water, but when it is used at room temperature without being cooled by the cooling medium 12. It is desirable to provide a waterproof layer.

As mentioned above, in such a current limiting unit (GL), if the line is short-circuited or grounded due to disconnection or contact, a strong current will flow to the fault location, causing major damage such as burning out electrical equipment in the circuit. This is to automatically and quickly cut off large currents through current limiting action and isolate faulty sections.

Therefore, the current limiting unit G1 is installed and used in each predetermined section of the line 50, as the circuit is shown in FIG.

- In such a current limiting unit G1, the current limiting unit G1 is normally
1110 is a superconductor and has an electrical resistance of O, so no Joule heat is generated, so there is no transmission loss at all. At this time, the current I is bypassed. In the fuse circuit, the terminals 18 and 19 connect the resistor R. Because it has, it will not flow.

For some reason, an abnormality such as a short circuit or ground fault occurs on the line, and a large current flows through the line 50 to the current limiting unit (CI).
When the current limiter 10 flows from the superconductor to the quench state in a short time, no current flows through the current limiter 1110 (at the same time, the current flows from the fuse circuit with resistance R, that is, from the upstream unit terminal to the cooling tank). 11, terminal 18
, the fuse 20, the terminal 19, the other part of the cooling tank 11, and the downstream unit terminal in this order. At this time, terminal 18.1
Since terminal 9 has a resistor R, the current is sufficiently restricted by the terminals 18 and 19 to the extent that problems such as burnout of the load equipment do not occur, and an excessive current does not flow all at once.

While the current is being throttled, the fault that has occurred is removed and the current limiting line 10
When the current limiting wire 10 returns to a superconducting state, normal current flow from the current limiting wire 10 resumes.

If the fault is not removed while the current is being reduced, the fuse 20 will automatically blow out due to the Joule heat caused by the overcurrent, and the current will be temporarily interrupted to prevent a failure due to the overcurrent. is removed and the current limiting line l
When O returns to the superconductor, energization is resumed.

Here, if the fault is not removed even when the current is interrupted, and the current-limiting wire 10 returns to the superconductor state, the current-limiting wire 10 will be in the quench state again due to the excessive current, and the current-limiting wire 10 will be in the quench state again as long as the fault continues. The streamline 10 repeats the transition to the quench state with the superconductor. Therefore, as a countermeasure for this, for example, the number of repetitions is counted at the substation, and when the number of repetitions reaches a predetermined number (for example, two times), the faulty line section is disconnected using a substation circuit breaker to completely cut off the current in the line section. It is preferable.

If the fuse 20 is blown or not when the power supply is stopped, the accident area can be immediately determined, so that recovery from the accident can be speeded up. Since the current limiting wire 10 has been transferred to a superconductor during the accident recovery work, once the accident recovery is completed, the circuit breaker can be turned on and the zero wire 50 energized again.

Next, FIG. 3 shows an example of a current-limiting unit G2 that does not have a fuse circuit, and FIG. 4 shows its circuit.This current-limiting unit G2 is different from the current-limiting unit G1 shown in FIG. The cooling tank 3 is used to bypass the cooling tank 31 itself.
1 is not divided into two by an insulator and has conductivity and resistance.

The other structure is exactly the same as the current limiting unit G1 in FIG.

In this current limiting unit G2, when a large current flows through the line 50 to the current limiting unit G2 due to an accident, the current limiting line 3
0 transitions from the superconductor to the quench state, and the current bypasses the conductive cooling bath 31 with resistance r.

At this time, the current is throttled by the resistance r of the cooling tank 31.

If the fault is removed while the current is being throttled and the current limiting wire 30 returns to a superconductor, normal current flow from the current limiting wire 30 is resumed.

If the fault has not been eliminated at this point, the current limiting line 30 will repeat the transition to the superconductor and quench state while the fault continues, so as in the previous example, if the fault duration exceeds the specified time, the power will be switched off. It is preferable to operate the station circuit breaker to completely cut off the current in the faulty line section.Since the current limiting line 30 is transferred to a superconductor during the accident restoration work, once the accident restoration is completed. , it is sufficient to turn on the circuit breaker and restart energization of the zero wire 50.

It goes without saying that the present invention is not limited to the above embodiments, and other embodiments may be adopted as long as they do not depart from the purpose of the present invention.

〔Effect of the invention〕

Since the current limiting unit of the present invention is configured as described above, it produces the effects described below.

A superconducting wire made of ceramic superconducting material is used as a current limiting wire, and a bypass is provided to detour and throttle the current when the current limiting wire shifts from the superconductor to the quench state due to excessive current. During transition, the current limiting wire will not burn out due to its high resistance characteristics.

In addition, since the overall structure is simple and unitized, it is easy to handle and can be easily installed on IIM roads, and is low cost, making it possible to operate the power system rationally and economically. It is something.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of one embodiment of the current limiting unit of the present invention, Fig. 2 is a schematic circuit diagram when the current limiting unit shown in Fig. 1 is installed on the line of a power system, and Fig. 3 is a diagram of the present invention. FIG. 4 is a sectional view of another embodiment of the current limiting unit of the invention, and is a schematic circuit diagram when the current limiting unit shown in FIG. 3 is installed on a line of an electric power system. G1, G2: Current limiting unit 1O130; Current limiting wire (superconducting wire) 11.31: Conductive cooling tank 13.33: Heat insulation tank 16.36: Unit terminal 17: Insulator 18.19: Terminal 20: Fuse 50: Lines R, r: Resistance diagram 2

Claims (2)

[Claims] (1) A current limiting unit installed on the lines of a power system, in which a unit terminal for connecting the line is attached to a superconducting wire made of ceramic superconducting material, and the unit terminal is placed in a conductive cooling tank. At the same time, the cooling tank and the unit terminal are electrically connected, and the cooling tank is divided into one part and the other part by an insulator provided in the cooling tank, and the outer surface of one part of the cooling tank and the other part are connected to each other electrically. A current limiting unit characterized in that terminals each having a resistance are attached to the outer surface of the unit, and a fuse is installed between both terminals. (2) A current-limiting unit installed on power system lines, in which a unit terminal for line connection is attached to a superconducting wire made of ceramic-based superconducting material, and the superconducting wire is placed in a cooling tank that has conductivity and resistance. 1. A current limiting unit characterized in that a terminal is arranged so as to pass through a cooling tank, and the cooling tank and the unit terminal are electrically connected.