JP3777424B2 - Current limiter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a current limiter that suppresses overcurrent in the event of a system fault.
[0002]
[Prior art]
Up to now, a method using arc / resistance, a method using a semiconductor element such as a GTO having self-erasing capability, a method using a diode bridge and a DC reactor, a method using a normal conduction transition phenomenon of superconductivity, LC resonance Various fault current limiters, such as a system that uses, have been proposed and developed.
[0003]
[Patent Document 1]
JP 2000-13993 A [Patent Document 2]
Japanese Patent Laid-Open No. 2002-262450 [0004]
[Problems to be solved by the invention]
However, when the current limiter performs a current limiting operation, the higher the current limiting capability, the higher the voltage is applied between both terminals of the current limiter. Is equal to the line voltage, and a current limiter that can withstand this high voltage needs to have a large capacity, which is large in size and expensive. Moreover, in order to install this separately as a power transmission / distribution facility, a space for installing it must be secured, and there is a problem that the installation location is limited.
[0005]
Furthermore, the method using the normal conduction transition phenomenon of superconductivity has a problem that it takes time to return to the superconducting conductor again after the normal conduction transition and it is difficult to control the return time. In addition, the scale of the equipment becomes large, such as the need to install a cryostat.
[0006]
In addition, in the power system, there is a voltage class suitable for the transmission capacity of each line, and since it is transformed several times by the transformer in the flow of consumption from the generation of power energy, multiple transformers in the line However, it is difficult to provide the conventional current limiting device as described above for these transformers.
[0007]
And in the current transmission system, the overcurrent at the time of the accident is kept below the rated breaking current of the circuit breaker and the stability of the system is secured, but with the future expansion of the system scale, It is possible that the overcurrent at the time of accident exceeds the rated breaking current. In addition, in the distribution system, it is expected that the number of distributed power sources linked to the electric power business will be increased. It is feared that the fault current exceeds the breaking capacity of the power distribution breaker.
[0008]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a current limiting device for suppressing a fault current that is simple and economical and can be easily applied to a transformer.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a yoke having an arbitrary shape capable of forming a closed closed magnetic circuit via a primary winding connected to a power feeding system and a secondary winding connected to a power transmission system, A movable body provided with a magnetic path forming portion made of a magnetic material having an arbitrary shape that magnetically couples two points of the yoke so as to generate a leakage magnetic path between the primary winding and the secondary winding. And moving the movable body to a first position where a leakage magnetic path is not formed by the magnetic path forming portion of the movable body and a second position where a leakage magnetic path can be formed by the magnetic path forming portion of the movable body. A movable body moving means and a current limiting function operating condition detecting means for detecting that a predetermined current limiting function operating condition has been achieved, wherein the current limiting function operating condition detecting means achieves the current limiting function operating condition. The movable body moving means moves the movable body on the basis of Characterized in that from the first position to be moved to the second position.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of a current limiting device according to the present invention will be described based on the attached drawings.
[0011]
FIG. 1 is a structural diagram showing an embodiment of a current limiting device according to the present invention. In the figure, 1 is a primary winding, 2 is a secondary winding, 11 is a fixed iron core, and functions as a yoke of an arbitrary shape that can form a closed closed magnetic circuit via the primary winding 1 and secondary winding 2. To do.
[0012]
As shown in FIG. 2, the details of the movable body 15 are a rod-shaped body including a movable iron piece 12 and a support material 13. The movable iron piece 12 is a magnetic path made of a magnetic material having an arbitrary shape that magnetically couples two points of the fixed iron core 11 so as to generate a leakage magnetic path between the primary winding 1 and the secondary winding 2. It functions as a forming part. The movable iron piece 12 and the fixed iron core 11 are formed by laminating electromagnetic steel plates that are ferromagnetic materials. The support member 13 is made of a nonmagnetic material.
[0013]
The movable body 15 configured as described above includes a state in which the movable iron piece 12 is positioned between the first protrusion 11a and the second protrusion 11b provided on the fixed iron core 11, and the first protrusion 11a and the second protrusion. The support member 13 can be slidably moved in a direction (a direction indicated by an arrow 14 in FIG. 2) that can be converted into a state in which the support member 13 is positioned between the portion 11b.
[0014]
The current limiter configured as described above functions as a current limiter that can be used by inserting it at an appropriate place in the transmission and distribution system if the primary winding 1 and the secondary winding 2 have the same winding ratio. If the winding ratio between the winding 1 and the secondary winding 2 is changed, it can be used as a transformer with a current limiting function. 3 and 4 show an example of use as a transformer, in a normal energized state in which the current limiting function is not activated (between the first protrusion 11a and the second protrusion 11b provided on the fixed core 11). Is a diagram showing a state in which the support member 13 is positioned. FIG. 4 is a view showing a current limiting state in which the current limiting function is activated (a state in which the movable iron piece 12 is positioned between the first protrusion 11a and the second protrusion 11b provided on the fixed iron core 11). is there. In FIGS. 3 and 4, 21 is an AC power source, and 22 is a load.
[0015]
5 and 6 are side views of the current limiting device of FIG. 1 as viewed from the side, and FIG. 5 is a normal energized state (between the first protrusion 11a and the second protrusion 11b provided on the fixed iron core 11). 6 shows a state in which the support member 13 is located), and FIG. 6 shows a current limiting state (a state in which the movable iron piece 12 is located between the first protrusion 11a and the second protrusion 11b provided on the fixed core 11). It is a figure.
[0016]
5 and 6 show an overcurrent detector 31 that functions as a current limiting function operating condition detection means for detecting that a predetermined current limiting function operating condition has been achieved, and a movable that moves the movable body 15. A driving mechanism (for example, an electromagnetic relay 32, an excitation power source 33, an electromagnet solenoid 34, a tension spring 35, etc.) as a body moving means is also shown.
[0017]
During normal energization, the electromagnetic relay 32 is turned on. Thereby, the electromagnet solenoid 34 fed by the excitation power source 33 is excited, and the generated electromagnetic force is moved against the force of the tension spring 35 to contract the movable body 15 in the position shown in FIG. 13 is pulled to a position between the first protrusion 11a and the second protrusion 11b) and is stationary, so that the movable body 15 is in the first position where the leakage magnetic path is not formed by the movable iron piece 12 during normal energization. Will be moved.
[0018]
When the movable body 15 is in the first position as described above, the support member 13 made of a nonmagnetic material is present between the first protrusion 11a and the second protrusion 11b, so that the magnetic resistance therebetween increases. Te, the magnetic flux phi _g between the first projection 11a and the second protrusion 11b decreases when compared to phi ₁ and phi _2, the magnetic path passing through the first projection 11a and the second projection 11b is formed Since it can be regarded as not being performed, a leakage magnetic path is not formed during normal energization. Further, the current limiter during normal energization functions as a normal transformer having a small leakage reactance and a small voltage fluctuation rate when φ _g is sufficiently small and φ ₁ ≈φ ₂ .
[0019]
When the relative permeability of the ferromagnetic material is infinite, the relative permeability of the non-magnetic material is approximated as 1, the cross-sectional area of the iron core is S, and the vacuum permeability is μ ₀ , the magnetoresistance R _n is By using the gap length g between the first protrusion 11a and the second protrusion 11b, it can be expressed as “R _n = g / μ ₀ S”. When the number of turns of the primary winding is n ₁ , the leakage reactance L _n viewed from the primary side is “L _n = n ₁ ² / R _n ”.
[0020]
In order to further reduce the leakage reactance, a good conductor such as copper or aluminum is used for the nonmagnetic support member 13 and a method of canceling φ _g by an eddy current flowing through the non-magnetic support material 13 or a leakage reactance by inserting a capacitor in series with the circuit. There is also a method for compensating for the minute or a method for compensating for the voltage fluctuation by providing a load tap switching mechanism in the winding.
[0021]
Subsequently, as shown in FIG. 4, when a short circuit or a ground fault occurs on the secondary side and the line current I ₁ or I ₂ exceeds the current limiting start current value (when the current limiting function operating condition is achieved), This is detected by an overcurrent detector 31 as current limiting function operating condition detection means, and the electromagnetic relay 32 is turned off by the detection output of the overcurrent detector 31. As a result, the electromagnet solenoid 34 is demagnetized, and the movable body 15 quickly moves to the position shown in FIG. 6 due to the force of the tension spring 35 to contract, so the first protrusion 11a, the movable iron piece 12, and the second protrusion. A magnetic path (leakage magnetic path) passing through 11b is formed. That is, when the current limiting function is operated, the movable body 15 is moved to the second position where the leakage magnetic path can be formed by the movable iron piece 12.
[0022]
At this time, a slight gap is generated on the surface of the fixed iron core 11 where the first protrusion 11a, the second protrusion 11b, and the movable iron piece 12 are in contact with each other. However, if the length of this slight gap is p, the magnetic resistance R _f of the magnetic path passing through the movable body 15 at the time of current limiting can be expressed as R _f = p / μ ₀ S. Since p << g, R _f << R _n .
[0023]
When the leakage magnetic path is formed as described above, the leakage reactance L _f viewed from the primary side is L _f = n ₁ ² / R _f . At the time of the secondary side accident, the voltage across the secondary winding is almost zero, so φ ₂ ≈0 and φ ₁ ≈φ _g . The primary current I ₁ at this time, the primary voltage V _1, when the angular frequency and omega, the _{I 1 = V 1 / (ωL} f). If p is reduced and R _f is reduced, L _f is increased and I ₁ can be suppressed. That is, when an accident occurs on the secondary side, the fault current can be limited by moving the movable body 15.
[0024]
When the accident is resolved and power transmission is resumed, if the electromagnetic relay 32 is turned on again and the electromagnet solenoid 34 is excited, the movable body 15 is pulled to the position of FIG. 5 by the generated electromagnetic force. Thus, the leakage reactance of the transformer is reduced again and power transmission is started.
[0025]
FIG. 7 is a waveform diagram when a device for demonstrating that the current can be limited by the movement of the movable iron piece is manufactured and tested. The winding ratio of the primary winding and the secondary winding was 2: 1, the secondary winding was short-circuited, and the current I _sol of the electromagnetic solenoid was cut off at time 0 second. As can be seen from FIG. 7, after the electromagnetic solenoid current I _sol is cut off and after a period of three and a half cycles to four cycles, the movement of the movable iron piece is completed, and the primary current I ₁ and the secondary current I ₂ are completed. Was limited.
[0026]
As can be seen from FIG. 7, even after the current limiting function is activated in the transformer to which the current limiting device according to the present embodiment is applied, the secondary current cannot be completely cut off, but it is possible to avoid danger. Can be suppressed to a sufficient level. In addition, since high voltage and arc are not generated in the movable part, there is an advantage that consumption of the electrode can be suppressed.
[0027]
Also, the time from the detection of the accident to the completion of the current limiting operation (substantially the time from when the current I _sol of the electromagnet solenoid 34 is cut off until the primary current I ₁ and the secondary current I ₂ are limited. In order to further shorten the length of the drive mechanism, the drive mechanism may be improved, for example, by changing the tension spring 35 to one having a stronger force of contraction. Of course, other movable body drive mechanisms that are not electromagnet solenoids and tension springs may be employed to realize faster movement of the movable body. It should be noted that what kind of mechanism is adopted as the movable body moving means is within a range of arbitrary design matters, and it is desirable that the moving speed is faster, and that it is smaller, lighter and less expensive.
[0028]
Moreover, in the said embodiment, although the 1st protrusion part 11a and the 2nd protrusion part 11b were provided in the fixed iron core 11, and the one movable body was located in between, the leakage magnetic path shall be formed, The method of forming the leakage magnetic path is not limited to this, and the magnetic resistance of the leakage magnetic path is low during current limiting operation when the magnetic path forming portion of the movable body is at the second position, and the magnetic path formation of the movable body is performed. What is necessary is just to be able to make high the magnetic resistance between the leakage magnetic path formation site | parts at the time of normal electricity supply which has a part in a 1st position.
[0029]
【The invention's effect】
As described above, according to the current limiter according to the first aspect, when the current limiting function operating condition detecting means detects that the current limiting function operating condition is achieved, the movable body moving means moves the movable body to the first position. By moving from the position to the second position, a leakage magnetic path can be formed, the magnetic coupling between the first winding and the second winding is switched, and a fault current due to a short circuit or the like can be quickly suppressed. it can. In addition, since the normal conducting transition phenomenon of the superconducting material is not used, there is an advantage that the current limiting start current value and the return time to the normal energized state can be easily controlled.
[0030]
In addition, the current limiter according to claim 1 can be used as a transformer with a current limiting function by changing a winding ratio between the first winding and the second winding. In that case, since it is necessary to provide a movable body moving means, the size is large and expensive compared to an ordinary transformer, but it is required for installation as compared with the case where a large capacity current limiter is provided separately from the transformer. Space can be reduced and can be provided at low cost. Moreover, since the transformer winding is originally designed to withstand the line voltage, there is an advantage that the winding can be used when the present invention is applied to an existing transformer.
[Brief description of the drawings]
FIG. 1 is a schematic structural diagram showing an embodiment of a current limiting device according to the present invention.
2 is a perspective view showing an appearance of a movable body in FIG. 1. FIG.
FIG. 3 is an explanatory diagram showing a normal energization state, which is an example in which a current limiter is applied to a transformer.
FIG. 4 is an example in which a current limiting device is applied to a transformer, and is an explanatory diagram showing a current limiting state.
FIG. 5 is a side view of the current limiter in a normal energized state.
FIG. 6 is a side view of the current limiter in a current limiting state.
FIG. 7 is a diagram showing waveforms of a primary voltage V ₁ , a secondary voltage V ₂ , a primary current I ₁ , a secondary current I ₂ , and an electromagnetic solenoid current I _sol in a current-limiting operation verification test.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Primary winding 2 Secondary winding 11 Fixed iron core 12 Movable iron piece 13 Nonmagnetic support material 14 The arrow 15 which shows the movable direction of a movable body 15 Movable body 21 AC power supply 22 Load 31 Overcurrent detector 32 Electromagnetic relay 33 Excitation power supply 34 Electromagnet Solenoid 35 tension spring

Claims (1)

An arbitrarily shaped yoke capable of forming a closed closed magnetic circuit via a primary winding connected to the power feeding system and a secondary winding connected to the power transmission system;
A movable body provided with a magnetic path forming portion made of a magnetic material having an arbitrary shape that magnetically couples two points of the yoke so as to generate a leakage magnetic path between the primary winding and the secondary winding. When,
A movable body that moves the movable body between a first position where a leakage magnetic path is not formed by the magnetic path forming portion of the movable body and a second position where a leakage magnetic path can be formed by the magnetic path forming portion of the movable body. Transportation means;
A current limiting function operating condition detecting means for detecting that a predetermined current limiting function operating condition is achieved;
With
The movable body moving means moves the movable body from the first position to the second position based on the fact that the current limiting function operation condition detecting means detects the achievement of the current limiting function operation condition. Current limiting device.

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