JPH02307327A - Current limiter device - Google Patents

Abstract

PURPOSE:To promptly remove a thermal fault due to an overcurrent so as to suppress vaporization of a cooling medium by connecting the first superconducting coil in series and the second superconducting coil in parallel to a switching element. CONSTITUTION:At the time of generating an overcurrent, a flow of the current in a trigger coil 2a of small critical current value is suppressed. A switching element 2h is opened, a circuit of the trigger coil 2a is cut off and an electric current is supplied to a load 3. Since opening action of the switching element 2h is performed simultaneously with the reactor action of a current limiting coil 2b, the switching element, while it is surely actuated, operates at a high speed of action with out a delay. In this way, generation of a thermal fault due to the overcurrent can be promptly removed, and vaporization of a cooling medium such as helium can be effectively suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a superconducting current limiting device that limits overcurrent flowing through an electrical circuit.

[Conventional technology]

Conventionally, when an overcurrent occurs in an electric circuit such as a distribution line due to a short circuit between lines or a ground fault, a current limiting device is used to limit the overcurrent. In some cases, a large overcurrent will flow,
It becomes difficult to use normal current limiting devices.

Therefore, as a current limiting device that can limit the overcurrent that occurs when supplying a large current as described above,
The use of superconducting current limiting devices is being considered.

[Problem to be solved by the invention]

In order to obtain a superconducting state, such superconducting current limiting devices require a low temperature maintenance device that maintains the device at an extremely low temperature using a cooling medium such as liquid helium. If a thermal disturbance occurs due to the generation of helium, liquid helium will rapidly vaporize, which is undesirable.

In other words, this vaporization means the consumption of expensive liquid helium, which not only causes a decrease in cooling capacity, but also exerts a large pressure on the container housing the superconducting current limiting device, and the effect of pressure is also It becomes a problem.

Therefore, there has been a need for a superconducting current limiting device that instantaneously limits the generated overcurrent to prevent a thermal failure that may lead to vaporization of a cooling medium such as liquid helium when an overcurrent occurs in the electrical circuit.

The present invention has been made in view of the above points, and its purpose is to limit the overcurrent when it occurs in the electrical circuit, quickly eliminate thermal damage caused by the overcurrent, and An object of the present invention is to provide a superconducting current limiting device capable of suppressing vaporization of such a cooling medium.

[Means to solve the problem]

The above object is achieved by a current limiting device according to the present invention. That is, in summary, the present invention provides a superconducting current limiting device that limits overcurrent in an electrical circuit, including a first superconducting coil having a predetermined critical current value and a critical current value higher than the first superconducting coil. and a second superconducting coil configured to generate a magnetomotive force in an opposite direction with substantially the same strength as that of the first superconducting coil, and a second superconducting coil that is biased by the current suppressed state of the first superconducting coil and performs an opening operation. a switching element configured as follows, the switching element and the first superconducting coil are connected in series, and the second superconducting coil is connected in parallel to the switching element and the first superconducting coil. This is a current limiting device characterized by the fact that it is connected.

[For production]

According to the present invention, in a steady state, the switching element is closed and the currents flowing through the first superconducting coil and the second superconducting coil are approximately the same value, and the magnetic flux of each coil is generated by this current. cancel each other out, resulting in a non-inductive state and steady operation with zero resistance.

Next, when an abnormality occurs, that is, when an overcurrent occurs,
Due to this overcurrent, the current flowing through the first superconducting coil, which has a small critical current value, is suppressed, and the first superconducting coil becomes a high-resistance body, causing most of the total current to be diverted to the second superconducting coil. As a result, the second superconducting coil acts as a beam axle. At this time, the switching element is opened by the magnetic field generated by the second superconducting coil, and therefore the circuit of the first superconducting coil, which is in the current suppressed state, is interrupted, and the entire current flows through the second superconducting coil. The current will flow to the load side through the capacitor, and current will be supplied.

At this time, the opening operation of the switching element is performed simultaneously in conjunction with the acdle operation of the second superconducting coil, so that the switch operation can be performed reliably, and the operation speed is increased without causing any delay in the switch operation. As a result, it is possible to quickly eliminate the occurrence of thermal failures due to overcurrent, and it is possible to effectively suppress adverse effects such as vaporization of a cooling medium such as helium.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is an explanatory diagram of one embodiment of a superconducting current limiting device according to the present invention, and FIG. 2 is an explanatory diagram of the operation of the device shown in FIG. 1.

Referring to FIG. 1, a superconducting current limiting device 2 of the present invention is connected between an AC power source 1 and a load 3 via an electrical line, and the current limiting device 2 is a It is placed in a cryostat (not shown) filled with media.

Here, the above-described current limiting device 2 will be explained in more detail.

That is, the current limiting device 2 includes a first superconducting coil 2a (hereinafter referred to as a trigger coil) formed in a cylindrical shape and having a predetermined critical current value;
A is provided with a second superconducting coil 2b (hereinafter referred to as a current limiting coil) arranged so as to surround a. The current limiting coil 2b is configured to generate a predetermined critical current value H higher than that of the trigger coil 2a, and to generate a magnetomotive force in the opposite direction with substantially the same strength as the coil 2a. Note that the trigger coil 2a and current limiting coil 2b are wound around coil spools 2C and 2d, respectively.

A common terminal 2e, which is a common terminal for these coils, is connected to one end of the trigger coil 2a and current-limiting coil 2b.
A trigger coil terminal 2f is connected to the other end of the trigger coil 2a, and a current limiting coil terminal 2g is connected to the other end of the current limiting coil 2b.

A switching element 2h such as a vacuum switch is connected in series to the coil 2a via a trigger coil terminal 2f, and the current limiting coil 2b is connected in parallel to the switching element 2h and the trigger coil 2a. It is arranged like this. The switching element 2h is arranged within the magnetic field generated by the current-limiting coil 2b, as described later, and generates a magnetic field in the current-limiting coil 2b depending on the suppressed state of the current flowing through the trigger coil 2a, so that the current-limiting coil 2b performs an opening operation. It is configured. That is, the trigger coil 2a
The current limiting coil 2b is configured to generate a magnetic field in the current suppressed state, and the magnetic field generated by the current limiting coil 2b is configured to drive an armature for driving a contact of a vacuum switch used as a switching element, for example. has been done.

The operation of the above embodiment configured as described above will be described below with reference to FIG. 2.

Now, when the superconducting current limiting device is in the operating state, the switching element 2h is in the closed state in the steady state,
As a result, the circuit currents 11.12 flowing through the current limiting coil 2b and trigger coil 2a in the current limiting device 2 have approximately the same value, and the magnetic fluxes φ1 and φ2 of the respective coils caused by the circuit currents i1 and i2 cancel each other out. Accordingly, the current limiting device 2 has no induction and zero resistance, and can perform steady operation.

Next, when an abnormality occurs, that is, when an overcurrent occurs,
Trigger coil 2 has a small critical current value due to this overcurrent.
The current flowing through a is suppressed, making it a high-resistance element. As a result, most of the total current flowing through the current limiting device 2 is commutated to the current limiting coil 2b side (11>12), and as a result, this current limiting coil 2
b Acts as a beam axle. At this time, since the switching element 2h is placed within the magnetic field generated by the current limiting coil 2b, the magnetic flux φ1 generated by the current limiting coil 2b
(φ2″: 0), the switching element 2h is opened, and as a result, the trigger coil 2a is in a current suppressed state.
The circuit is cut off, and the entire current flows to the load 3 via the current limiting coil 2b, supplying current to the load 3. The opening operation of the switching element 2h is performed simultaneously in conjunction with the current limiting coil 2b acdle operation, so that it operates reliably and has no delay and the operating speed is high. Therefore, the occurrence of thermal failure due to overcurrent can be quickly eliminated,
Evaporation of a cooling medium such as helium can be effectively suppressed.

When the switching element is placed outside the generated magnetic field, this switching element operation detects the current suppression state of the current limiting coil and then operates the switching element via a relay or the like (tS configuration is complicated and time consuming). It has great effects, such as being able to achieve faster speeds and quickly eliminating thermal failures caused by overcurrent.

It is something to do.

Furthermore, a superconducting coil is used, and changes in the current flowing through this superconducting coil are used to generate magnetic flux, and this generated magnetic field activates a switching element to perform current limiting, so although there is inductance, there is no resistance, and the flow is continuous. Current can be limited without loss, and since the generated magnetic field is used as a driving source for the switching element, no separate driving source is required. Further, since the switching element is located within the magnetic field generated by the current limiting coil, and the current is limited by the operation of the switching element, only two lead wires are required per lead wire. This means that fewer lead wires are required compared to the three lead wires required when the switching element is placed outside the generated magnetic field, and as a result, the thermal effect on the superconducting current limiting device is reduced. can be done.

〔Effect of the invention〕

As explained above, according to the current limiting device of the present invention,
First and second superconducting coils are provided, and a switching element connected in series to the first superconducting coil is provided, and the second superconducting coil is connected to the switching element and the first superconducting coil.
When an overcurrent occurs, most of the current is commutated to the second superconducting coil to generate a magnetic field, and this generated magnetic field causes switching. Since the element is opened to limit the flow of overcurrent, the switching element opens simultaneously in conjunction with the generation of the magnetic field of the second superconducting coil, and therefore, this opening operation is reliable. It operates quickly and operates at high speed without delay, and therefore has the effect of quickly eliminating thermal damage caused by overcurrent and suppressing vaporization of a cooling medium such as liquid helium.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the superconducting current limiting device according to the present invention, and FIG. 2 is an explanatory diagram of the operation of the superconducting current limiting device shown in FIG. 1. DESCRIPTION OF SYMBOLS 1... Power supply, 2... Current limiting device, 2a... Trigger coil, 2b... Current limiting coil, 2 Cs 2 d...
Coil spool, 2e... common terminal, 2f... trigger coil terminal, 2g... current limiting coil terminal, 2h...
Switch, 3...Load.

Claims (1)

[Claims] 1. In a superconducting current limiting device that limits overcurrent in an electric circuit,
a first superconducting coil having a predetermined critical current value; and a first superconducting coil having a higher critical current value than the first superconducting coil and generating a magnetomotive force in the opposite direction with approximately the same strength as the first superconducting coil. a second superconducting coil, and a switching element configured to perform an opening operation when biased by the current suppression state of the first superconducting coil, and the switching element and the first superconducting coil are connected in series. , and the second superconducting coil is connected in parallel to the switching element and the first superconducting coil. 2. The armature for driving the contact of the switching element is arranged to be operated by the magnetic field of the second superconducting coil generated when suppressing the current of the first superconducting coil. current limiting device. 3. The current limiting device according to claim 1 or 2, wherein the switching element is a vacuum switch.