JPH065247B2 - Coil system abnormality monitoring device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a coil system abnormality monitoring device, and more particularly to a coil system abnormality monitoring device capable of promptly dealing with an abnormal state such as a rare short circuit.

<Prior Art> Conventionally, a coil has been used in various applications for the purpose of stepping up, stepping down, forming a magnetic field, and the like. These coils require sufficient consideration for insulation between adjacent coil windings so that rare shorts do not occur from the viewpoint of performing an operation conforming to design conditions. Therefore, optimal insulation is provided according to the application of each coil, the applied voltage, and the like.

That is, it is known that, when the current directions are the same, a tensile force proportional to the square of the current and inversely proportional to the winding interval is applied between adjacent coil windings. Since the line spacing is extremely small, in the case of a coil that carries a large current, such as a toroidal magnetic field coil used for confining plasma in a fusion reactor, a large tensile force always acts and By using it, the insulation strength between the windings decreases, and eventually a rare short circuit occurs.

In order to deal with such an abnormal situation, conventionally, an overcurrent relay is connected in series with the coil, and it is determined that a rare short circuit has occurred by detecting that the current flowing through the coil has increased abnormally. The voltage application to the coil is cut off.

However, the overcurrent relay operates at a time when a considerable amount of time has passed after one layer of the coil has been short-circuited, and at this time, the damage due to the rare short has spread considerably. This means that it is impossible to prevent burnout, disconnection, etc. of the sound part of the coil.

In other words, the voltage application cannot be interrupted until the damage caused by the rare short occurs in a considerable range, and in particular, in the fusion reactor etc., a cooperative magnetic field for confining plasma etc. is generated. In the toroidal coil used for this purpose, a large current is made to flow by setting it in a superconducting state, so the above-mentioned damage also appears remarkably, so that the voltage application can be cut off more quickly. Measures are eagerly awaited.

<Purpose> The present invention has been made in view of the above problems,
It is an object of the present invention to provide a coil system abnormality monitoring device capable of quickly interrupting voltage application when a rare short circuit occurs.

<Structure> The coil system abnormality monitoring device of the present invention for achieving the above object detects that the apparent inductance of the coil has changed from the normal inductance by a predetermined value or more, and an abnormality occurs in the coil. It is determined that the voltage has been applied to the coil, and the voltage application to the coil is cut off, and (E-Ri) (di / d
By calculating t) ^-1 , it is possible to constantly calculate the apparent inductance.

Here, E is the applied voltage, R is the resistance of the coil system, and i is the current flowing through the coil system.

That is, as a result of earnest studies, the present inventor has found that a coil short-circuited by a rare short circuit causes a change in magnetic flux Ladia / dt due to a current ia flowing through the entire coil due to mutual induction with a coil of another sound part. Current i that cancels
b begins to flow, and this current is the magnetic flux d due to dia / dt.
It has been found that a magnetic flux dφb / dt that cancels φa / dt is generated, and as a result, the apparent inductance L ′ of the coil immediately after the occurrence of a rare short circuit sharply decreases. Then, based on this knowledge, the voltage and the current applied to the coil are constantly detected, and the apparent inductance L ′ = (E−Ri) · di / dt (however, the current i = iaib) is calculated. By doing so, it is determined whether or not the inductance L ′ deviates from the normal value L by a predetermined value or more,
When the difference is equal to or more than a predetermined value, it is determined that a rare short circuit has occurred, and the voltage application to the coil is cut off, so that it is possible to prevent the remaining healthy portion from being burned or broken.

More specifically, FIG. 1 shows an equivalent circuit of a coil in a sound state, where the inductance is L and the resistance is R
, The applied voltage is E, and the flowing current is ia.
Therefore, the circuit equation is expressed by E = Ldia / dt + Ria, and the inductance is L = (E-Ria) (dia /
dt) ^-1 .

On the other hand, FIG. 2 is an equivalent circuit of a coil when a rare short circuit occurs. If the ratio of the rare short circuit generation portion is x and the circulating current of the rare short circuit generation portion is ib, the circuit equation for the entire coil is E = (1-x) ² dia / dt + x ² L (dia / dt-dib / dt) + (1-x) × Ldia / dt + (1-x) × L (dia / dt-dib / dt) + ( It is represented by 1-x) Ria + xR (ia-ib), and the circuit equation for the portion where the rare short circuit occurs is O = X ² L (dib / dt-dia / dt)-(1-x) xLdia / dt + xR (ib -ia).

Therefore, from the above two equations, two equations are obtained: E = Ldia / dt + Ria-xLdib / dt-xRib xLdib / dt + Rib = Ldia / dt + Ria. From both equations, the inductance (apparent inductance) L ' If L '= (E-Ri) (di / dt) ^-1 = L-xL (dib / dt) (dia / dt) ^-1 -xRib (dia / dt) ^-1 is obtained. Since the value of xRib (dia / dt) ^-1 is extremely small, it can be approximated by L '= L-xL (dib / dt) (dia / dt) ^-1 .

If the circuit current i = at + b (where b is the current value at the time of occurrence of a rare short circuit), (dib / dt) (dia / dt) ^-1 = {(1-x) / x + Rb / xLa} exp (-Rt / xL) +1, and changes as shown in FIG. Therefore, as shown in FIG. 3, the apparent inductance L'decreases sharply at the time of occurrence of the rare short circuit, and thereafter increases to the inductance (1-x) L of the sound portion. The current flowing through the coil gradually increases, while the current flowing through the rare short layer increases rapidly.Therefore, it is possible to confirm that the current flowing through the coil has exceeded the predetermined value by the overcurrent relay. Even if the voltage application is detected and the voltage application is interrupted, the current flowing in the rare short layer becomes very large, and therefore, the healthy portion of the coil will be burned or broken.

However, in the present invention, as shown in FIG. 4, the time point t1 when a predetermined time has elapsed from the time point t0 when the rare short circuit occurs
Since the voltage application to the coil is cut off at
Not only does the current flowing through the entire coil not increase so much, but the current flowing through the rare short layer does not increase too much, so that burnout, disconnection, etc. will not occur in a sound portion.

<Example> Hereinafter, detailed description will be given with reference to the accompanying drawings illustrating an example.

Fig. 5 shows a configuration for implementing countermeasures for coil system abnormalities. (1) is a power supply, (2) is a voltage measuring instrument, (3) is a current measuring instrument, and (4) is an apparent. It is a calculator that calculates the above inductance, (5) is a power interruption controller,
(6) is a toroidal magnetic field coil. More specifically, the arithmetic unit (4) has an apparent inductance L '= (E-Ri) (di / based on the voltage E and the current i.
dt) ^-1 for calculating the power cutoff controller (5)
Calculates the difference between the apparent inductance L'and the normal inductance L, compares it with a predetermined reference value, and outputs a signal to shut off the power supply (1) when the difference exceeds a predetermined reference value. The toroidal field coil (6)
18 coils each having 72 turns are connected in series.

Then, let L1 be the entire 17 coils in which no rare short has occurred, L2 be the healthy part of the coil in which the rare short has occurred, and L3 be the part in which the rare short has occurred. Coil L1,
The self-inductance of L2 and L3 is 1.697 respectively.
339, 0.273257 × 10 ^-1 , 0.54207 ×
10 is ^-5, the mutual inductance between the coils L1, L2, L3, respectively .75167 × 10 ^-1, 0.384
The values are 07 × 10 ⁻³ and 0.105869 × 10 ⁻² , and the inductance L of the toroidal magnetic field coil (6) as a whole is L = 1.87788H.

In the above configuration, when a short circuit occurs at a coil current i = 5 kA and the short circuit resistance is 1 μΩ, the inductance L ′ of the toroidal magnetic field coil (6) as a whole is 1.
It is drastically reduced to 54H. The current flowing through the coil L3 is -36.7 due to the influence of the AT of the other coil L2.
Sudden change to kA. In addition, the excess or deficiency of AT (when no countermeasure is taken against the occurrence of short circuit) at the time point 3 seconds after the occurrence of the short circuit, occurs in the portion where the short circuit occurs.
2kA x 71T-36.7kA x 1T = 332.5kA
T, in other healthy parts, 5.2 kA × 72T = 37
Since it becomes 4.4 kAT, 41.9 kAT becomes insufficient in the short circuit occurrence portion, and the AT unbalance becomes 11%.

However, in the above-described embodiment, the voltage application to the toroidal magnetic field coil is cut off immediately (0.1 second) after detecting the drastic decrease in the inductance, so that the current flowing through the coil L3 is -28 kA at the time of short circuit. However, the AT current imbalance is 7%, and the voltage is cut off, so that the current returns to the original level, and after 0.4 seconds, the coil current is almost It becomes a normal value, and the current at the part where the short circuit occurs is almost zero.
Then, the currents of the coils L1, L2 and L3 decrease at the same rate.

Therefore, it is possible to reliably prevent the inconvenience of causing burnout, disconnection, or the like in a healthy portion under the influence of the current flowing in the short-circuited portion.

<Effect> As described above, according to the present invention, the voltage and the current across the coil are constantly measured, and the apparent inductance L ′ = (E−Ri) di / dt is calculated based on the voltage and the current. Compared with the inductance during normal operation, when the value deviates by more than a predetermined value, it is determined that a rare short circuit has occurred, and the voltage application to the coil is cut off, so the absolute value of the circulating current in the rare short circuit occurrence part is suppressed. Therefore, it is possible to suppress the adverse effects such as burnout and disconnection on a sound portion to a minimum.

[Brief description of drawings]

FIG. 1 is an equivalent circuit diagram of the coil, FIG. 2 is a diagram showing the ratio of the rate of change of the current flowing through the entire coil to the rate of change of the current flowing through the rare short circuit occurrence portion, and FIG. Fig. 4 shows the inductance over the front and back, the current flowing through the coil, and the current flowing through the rare short circuit. Fig. 4 shows the inductance before and after the rare short circuit and the current flowing through the coil when the voltage application is quickly interrupted after the rare short circuit occurs. , A diagram showing a current flowing in a rare short portion, and FIG. 5 is a diagram showing a configuration for implementing a coil system abnormality countermeasure method.

Claims (1)

[Claims] 1. A device for monitoring abnormality of a coil system during operation, comprising: voltage measuring means for measuring an applied voltage E to the coil system; current measuring means for measuring a current i flowing through the coil system; Based on the measured applied voltage E and current i, the calculating means for calculating the apparent inductance L ′ = (E−Ri) (di / dt) ⁻¹ of the coil, and the apparent inductance calculated by the calculating means. Inductance L when L'is normal
And a power cutoff control means for cutting off the voltage application to the coil when it detects a change of a predetermined value or more from the coil system abnormality monitoring device.