JP3000981B2 - High speed current limiter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-speed current limiting system for interconnecting two electric power systems and for preventing an instantaneous voltage drop of an important load on a distributed power supply connecting bus or for interrupting a current limiting operation of a general AC system. The present invention relates to a shutoff device.

[0002]

2. Description of the Related Art A high-speed current limiting device is used as a system interconnecting device for interconnecting two power systems or as a device for performing a current limiting interrupt of a general AC system.

[0003] In particular, a high-speed current-limiting circuit breaker used as a system interconnection device for interconnecting a distributed power supply connection bus such as a cogeneration connection bus to a commercial power supply system is susceptible to a short-circuit accident or a ground fault accident in the commercial power supply system. When it is detected, the distributed power supply connection bus is disconnected from the commercial power supply system, and plays an important role in preventing power supply stop and instantaneous voltage drop in the distributed power supply connection bus.

FIG. 11 shows that the applicant of the present application has disclosed in
1 shows a configuration of one phase of a high-speed current limiter 101 used for a measure against instantaneous voltage drop proposed in Japanese Patent Application Laid-Open No. 85012. The high-speed current limiting device 101 includes diodes D101 and D10.
It comprises a single-phase rectification bridge circuit composed of 2, D103, D104 and a DC reactor L101, and a circuit breaker CB101.

[0005] When a short-circuit accident occurs at the receiving end Rec2, for example, the high-speed current-limiting device 101 uses the effect of suppressing a change in the current of the DC reactor L101 to utilize the receiving end Rec.
The circuit breaker CB101 is disconnected while instantaneously suppressing the current flowing from 1 to the fault point, thereby preventing an instantaneous voltage drop on the power receiving end Rec1 side.

In the high-speed current limiting device 101, the DC reactor L101 has a relatively large reactance,
When a normal copper wire coil is used, the resistance value of the winding increases, and the resistance loss during normal operation increases.

Accordingly, it is effective to use a superconducting reactor having a resistance value of zero in principle with respect to a direct current.

[0008]

SUMMARY OF THE INVENTION DC reactor L10
When a superconducting reactor is used as 1, it is necessary to process the magnetic energy stored in the superconducting reactor after opening circuit breaker CB101 as described below. The inductance of the superconducting reactor is L and the circuit breaker CB101
Assuming that the peak value of the overcurrent flowing through the superconducting reactor immediately before opening is I _max , the energy Q stored in the superconducting reactor is given by Q = (）) · L · I _max ² as is well known.

[0009] In the high-speed current-limiting breaker 101, L is large as mentioned above, I _max is the current value during normal operation, i.e. to become a several-fold to ten-odd times the value of the rated current, Q
Is a very large value.

FIG. 12 shows the flow of current in the single-phase rectification bridge circuit after the circuit breaker CB101 is opened. Circuit breaker C
Current I _max flowing in the DC reactor L101 to open just before the B101 becomes the current circulating circuits that are short-circuited in an open simultaneously with the diode. The stored energy Q is consumed by the resistance in this circulation circuit.

Accordingly, event when the instantaneous overcurrent I _max is part of a superconducting reactor quenched, stored energy Q is intensively consumed quenched portions, the superconducting wire cause problems such melts.

[0012] To avoid this problem, when a superconducting reactor to be designed so as not to quench respect I _max, the forced use less superconducting wire of the AC losses, several times the normal operation time of the current Since a design having a sufficient margin for the short-time overcurrent is required, the superconducting reactor becomes extremely uneconomical.

In this case, the stored energy Q of the superconducting reactor is consumed only by the resistance of the external circuit. However, as shown in FIG. 12, since the external circuit is formed by a short circuit of a diode, the resistance is only the internal resistance of the diode, and is extremely small, for example, several μΩ to several mΩ. It takes a considerable time until it is consumed, that is, the current in the superconducting reactor becomes zero. The high-speed current limiter 101
If the reactor current does not fall below the rated current, the predetermined current limiting operation cannot be restored. Therefore, once a system failure occurs, there is a disadvantage that several hours are required until the interconnection is restored.

On the other hand, in order to solve the above-mentioned problem, a configuration shown in FIG. 13 can be considered as a method of processing the stored energy Q. High-speed current limiter 10 of FIG.
2 is a resistor R1 connected to an external circuit of the superconducting reactor L102.
01 and the short-circuit switch SW101 are provided, and the stored energy Q of the superconducting reactor L102 is consumed by the resistor R101. The short-circuit switch SW101 is provided to be closed during normal operation and to reduce loss at all times.

In this example, even if a part of superconducting reactor L102 is quenched, a higher resistance R is set.
The problem of consuming the stored energy Q at 101 and fusing the superconducting wire can be avoided.

However, in the device configuration shown in FIG. 13, it is necessary to cut off the direct current. Therefore, the short-circuit switch SW
An expensive DC circuit breaker is required as 101, which is considerably uneconomical and, for example, several thousand amps generated when a system fails.
It is difficult to realize a DC circuit breaker capable of handling a large amount of current.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide an inexpensive high-speed current limiting device capable of easily consuming the stored energy of a superconducting reactor. .

[0018]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a high-speed current limiting circuit breaker according to the present invention interconnects two electric power systems, and connects each AC terminal with two DC terminals as boundaries.
With each rectifier element arms extending comprising a single-phase rectifying bridge circuit is interposed, in the high-speed current-limiting breaker which is constituted by a DC superconducting reactor is connected between the two DC terminals, the rectifier elements are all diode If it is interposed in series <br/> at least one of the two arms connected to each AC terminal, rectifying element of the other thyristor of <br/> arm of one of the AC terminal side If a <br/> over arm of the rectifying device of the AC terminal side is a diode is interposed in series with at least one diode arms, when the rectifier element are all thyristors conducting even when the abnormal current from overflowing a resistor interposed in series with one less <br/> least among the AC terminal side arm to maintain the state, it is characterized by comprising a short-circuit means for short-circuiting both ends of the resistor.

According to the above-mentioned invention, during normal operation of the high-speed current limiting interrupter, both ends of the resistor are short-circuited by inexpensive short-circuit means such as a switch, so that the loss due to the resistor is always zero. When a short-circuit accident or the like occurs in the power system, the short-circuit means can be opened and the resistance can be inserted during a half cycle in which no current flows through the rectifier connected in series with the resistance. This eliminates the difficulty of inserting a resistor due to a constant current flow, which is assumed when a resistor is provided in series with the DC superconducting reactor.

[0020] When a rectifying element all diodes of the single-phase rectifier bridge circuit, in series with resistor to at least one of the two <br/> arm connected to the respective AC terminals are interposed. When a short-circuit accident or the like occurs in the power system and an overcurrent flows, the short-circuit means is opened and these resistors are inserted into the single-phase rectification bridge circuit. As a result, after the single-phase rectifier bridge circuit is disconnected from the power system by a circuit breaker or the like, the release current of the magnetic energy stored in the DC superconducting reactor is reduced by two arms connected to each AC terminal and the DC superconducting reactor. It flows two loops constituted by the, is consumed by the resistor inserted on both loops, rapidly attenuated.

One AC terminal side of the single-phase rectifier bridge circuit
If the rectifying elements of the arm are rectifying element diode <br/> arms of the other AC terminal side thyristors in series with the resistor to at least one diode arms is interposed. When a short circuit accident or the like occurs in the power system and an overcurrent flows, the short circuit is opened and a resistor is inserted into the single-phase rectifier bridge circuit. This allows the thyristor to be turned off after an accident
By setting the state to F, the current from the power system can be quickly cut off, and after the disconnection, the release current flows through a loop composed of a diode arm and a DC superconducting reactor. Is done.

When the rectifying elements of the single-phase rectifying bridge circuit are all thyristors, one arm is obtained by replacing the diode arm with a thyristor arm.
These thyristors have the same function as the diodes of the diode arm. That is, the conduction state of these thyristors is maintained even when an overcurrent flows abnormally, and the release current is consumed by the resistor inserted into this arm.

Therefore, the high-speed current limiting device can easily consume the energy stored in the DC superconducting reactor with an inexpensive configuration.

Further , the high-speed current limiting device according to the present invention comprises:
The short-circuit means is a thyristor.

According to the above invention, since the short-circuit means is a thyristor, a resistor can be connected to the rectifier in a short time after a short-circuit accident or the like occurs in the power system.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the high-speed current limiting circuit breaker according to the present invention will be described below with reference to FIGS.

As shown in FIG. 1, the high-speed current limiting device 1 according to the present embodiment has a structure in which all the arms of the single-phase rectification bridge circuit are constituted by diodes, and diodes D1, D2, D3 as rectifying elements. D4, superconducting reactor L1 as a DC superconducting reactor, resistors R1 and R2, switches SW1 and SW2 as short-circuit means, and circuit breaker C
B1.

The superconducting reactor L1 includes a diode D1
A DC terminal which is a connection point of D3 and diodes D2 and D4
And the DC terminal which is the connection point of Further, the resistor R1 and the switch SW1 are connected in parallel with each other, and they are connected in series with the diode D1. Similarly, the resistor R2 and the switch SW2 are connected in parallel with each other, and these are connected in series with the diode D3. The circuit breaker CB1 is provided outside the single-phase rectification bridge circuit.

The operation of the high-speed current limiting device 1 having the above configuration will be described below with reference to FIGS. FIG.
(A) and (b) are current distributions in the bridge circuit during the current limiting operation. Here, for simplification, the illustration of the resistors R1 and R2 and the switches SW1 and SW2 is omitted. When an overcurrent flows in the bridge circuit, each arm turns ON / OF alternately.
Repeat F. At this time, since the current is zero in the arm that is OFF, the switch can be easily opened. Furthermore, a cheap switch having a simple structure can be used.

Next, the above contents will be described in more detail with reference to FIG. FIG. 3A shows a state during normal operation,
The switches SW1 and SW2 are closed, and the resistors R1 and R2 are bypassed to eliminate the constant loss in the resistors R1 and R2.

When a short-circuit accident or the like occurs in the power system and an overcurrent flows, the current limiting operation of the high-speed current limiting device 1 is started.
In a half cycle with overcurrent, as shown in FIG.
Assuming that a current flows through the arms of the diodes D3 and D2, no current flows through the arms of the diodes D1 and D4 . Therefore, the switch SW1 is opened and the resistor R1 can be inserted. In the next half cycle, as shown in FIG. 3C, a current flows only through the arms of the diodes D1 and D4 , so that the switch SW2 is opened and the resistor R2 can be inserted.

As shown in FIG. 3D, the resistors R1 and R2
When the circuit breaker CB1 is opened in a state where the power supply is inserted, the energy stored in the superconducting reactor L1 is changed to the resistance R1 ·
Released via R2.

Next, the switch SW of the high-speed current limiter 1
The effect that the stored energy of the superconducting reactor L1 is released in the device configuration of FIG. 4 in which 1.SW2 is the thyristor TH1 and TH2 is verified.

The thyristors TH1 and TH2 are turned off by detecting a short circuit accident from a current change of a not-shown CT (current transformer) inserted in the AC circuit. The disconnection of the bridge circuit (opening of the circuit breaker CB1) was set to 60 ms after three cycles from the start of the current limit.

FIG. 5 shows the current flowing in superconducting reactor L1 after the start of the current limiting operation. It can be seen that the current increases every half cycle after the current limit starts. FIG. 6 (a)
(B) shows the waveform of the voltage between the terminals of the resistors R1 and R2. The resistor R1 is inserted in a half cycle immediately after the start of the current limit, and a terminal voltage is generated in the resistor R1 in the next half cycle. It can also be seen that the resistor R2 was successfully inserted in the next half cycle after the insertion of the resistor R1.

FIG. 5 shows that the current of the superconducting reactor L1 is rapidly attenuated after the circuit breaker CB1 is opened, and the return time is significantly longer than that in the case where several hours are required to return without inserting a resistor. It can be seen that it can be shortened.

The recovery rate of the stored energy of the superconducting reactor L1 by the resistors R1 and R2 is as follows.
Is 20Ω (the combined series resistance value of the superconducting reactor L1 is 10Ω) and the resistance generated when the superconducting reactor L1 is quenched is about 0.2Ω, and 10 / (10+
0.2) × 100 = 98 (%). Therefore, even if it is quenched, the consumed energy in the superconducting reactor L1 is about 2% of the stored energy, and there is no problem at all.

On the other hand, as is clear from the above description, the configuration of the high-speed current limiting circuit 2 in which the insertion positions of the resistors R1 and R2 are as shown in FIG. 8 is also possible. In this case, the impedance of each arm viewed from the positive terminal and the negative terminal on the AC side differs by the resistances R1 and R2, and is therefore slightly asymmetric. However, since the resistors R1 and R2 can be inserted at the same time, the resistance value can be increased as compared with FIG. 1, and when the resistance generated when the superconducting reactor L1 is quenched is large, the energy in the resistors R1 and R2 can be increased. The recovery rate can be increased.

The reason why the values of the resistors R1 and R2 can be increased is as follows. In the case of FIG. 1, at the time of current reversal immediately after the insertion of the resistor R1 (between FIG. 3B and FIG. 3C), the current distribution is as shown in FIG. That is, when the current on the AC side becomes zero from the state of FIG. 3B, the current I1 flowing through the superconducting reactor L1
(Current value is I +) flows on the diode bridge side where no resistance is included, and the superconducting reactor L1 is in a state where the impedance is almost zero.

From this state, the current on the AC side is reversed and FIG.
The current I2 indicated by the dashed line starts flowing, and when this current value exceeds I +, the current of the diode D3 becomes zero, and the resistor R2 shown in FIG. 3C can be inserted. If the value of the current I2 is smaller than I +, the current always flows through the diode D3, so that the resistor R2 cannot be inserted (the current value is small when a breaker is used for the switch SW2). If it is within the range, it can be cut off, but if a thyristor is used, it cannot be cut off.

The value of the current I2 is the voltage V across the bridge circuit.
And the value of the resistor R1 are uniquely determined, so that the upper limits of the values of the resistors R1 and R2 applicable in FIG. 1 are determined from now on. On the other hand, in the configuration of FIG. 8, since there is no such restriction, the resistors R1 and R2 having high resistance values can be inserted.

Further, as shown in FIG. 9, a high-speed current limiting device 3 in which resistors and switches are arranged in all the arms of the bridge circuit is also possible. In this case, the switch and the resistor are provided at four places, which slightly increases the cost. However, the current on the AC side does not become asymmetric as shown in FIG. Large value resistors can be inserted. The reason why a resistor having a high resistance value can be inserted in the configuration of FIG. 9 is apparent from the same consideration as in the case of FIG.

That is, when the current on the AC side is zero, I +
8 circulates through the diode bridge. At this point, since the diagonal resistance of the bridge has been inserted, the current shunts left and right unlike FIG. Therefore, the value of the current corresponding to the current I2 in FIG.
In addition, since a resistor is inserted in the circulating current circuit, the value of I + itself rapidly attenuates. As a result, FIG.
The diode D1
The ON / OFF operations of D2, D3, and D4 are repeated, and all the resistors R1, R2, R3, and R4 can be inserted by opening the switches SW1, SW2, SW3, and SW4.

Further, as shown in FIG. 10, a high-speed current-limiting device 4 using a mixed bridge of diodes D1 and D2 and thyristors TH3 and TH4 is also possible. In this case, the thyristors TH3 and TH4 are used as the arms on one AC terminal side of the bridge circuit to omit the circuit breaker, and after the current limiting operation, the thyristors TH3 and TH4 are turned off to cut off the AC circuit.

Therefore, the energy stored in the superconducting reactor L1 becomes a current and circulates only in the circuit composed of the diodes D1 and D2 and the superconducting reactor L1, so that a single resistor for energy recovery can be inserted. It is enough. However, when the resistor is inserted at one position, the current of the thyristor may not pass through the zero point as in the case of the diode described above. At this time, it does not directly contribute to energy recovery, but a resistor may be inserted on the thyristor side.

It is also possible to adopt a configuration in which all rectifying elements of the single-phase rectifying bridge circuit are thyristors. At this time,
AC terminal side of the arm of the other side is the diode D1 · D2
Is simply replaced by a thyristor and is always set to the ON state. This by inserting at least one to the resistance of the of these other AC terminal side arm, the same effect as the high-speed current-limiting breaker 4 in FIG. 10 is obtained.

As described above, in the high-speed current limiting circuit breaker of this embodiment, the protection resistor for recovering the stored energy of the superconducting reactor by a simple switch without using an expensive DC circuit breaker is used. Can be inserted.

[0048]

As described above, the high-speed current limiting device according to the present invention interconnects two power systems and connects two DC terminals .
As a boundary, provided with a single-phase rectifier bridge circuits, each rectifying element extending arms each AC terminal is interposed in the high-speed current-limiting breaker which is constituted by a DC superconducting reactor is connected between the two DC terminals, If all of the above rectifiers are diodes, connect to each AC terminal
It is interposed at least one of the two arms in series being at least in the diode arms when the rectifying element of the arm of one of the AC terminal side is rectifying element diode arms of the other AC terminal side thyristors An AC terminal that is interposed in series with one another, and when all of the rectifiers are thyristors, should be kept conductive even when an overcurrent flows abnormally
A resistor interposed in series with at least one of the slave arm, a structure and a shorting means for shorting both ends of the resistor.

Therefore, there is an effect that it is possible to provide an inexpensive high-speed current limiting device capable of easily consuming the stored energy of the DC superconducting reactor.

Further, the high-speed current limiting device according to the present invention
As described above, the short-circuit means is configured as a thyristor.

Therefore, there is an effect that a resistor can be connected to the rectifying element in a short time after a short circuit accident or the like occurs in the power system.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an electrical configuration of a high-speed current limiting circuit breaker according to an embodiment of the present invention.

FIGS. 2 (a) and 2 (b) are explanatory diagrams illustrating a current distribution during a current limiting operation of the high-speed current limiting device of FIG. 1;

3 (a) to 3 (d) are explanatory diagrams illustrating a current limiting operation of the high-speed current limiting device of FIG. 1;

FIG. 4 is a circuit diagram showing an electrical configuration in the case where a switch is a thyristor in the high-speed current limiting device of FIG. 1;

FIG. 5 is a waveform diagram showing a current waveform of a superconducting reactor when the high-speed current limiting device of FIG. 4 performs a current limiting operation.

6 (a) and 6 (b) are waveform diagrams showing a voltage waveform between terminals of a resistor when the high-speed current limiting device of FIG. 4 performs a current limiting operation.

FIG. 7 is an explanatory diagram illustrating a state between (b) and (c) of the high-speed current limiting device of FIG. 3;

FIG. 8 is a circuit diagram showing an electrical configuration of another high-speed current-limiting circuit breaker according to the present embodiment.

FIG. 9 is a circuit diagram illustrating an electrical configuration of still another high-speed current limiting device according to the present embodiment.

FIG. 10 is a circuit diagram showing an electrical configuration of still another high-speed current limiting device of the present embodiment.

FIG. 11 is a circuit diagram showing an electrical configuration of a conventional high-speed current limiting circuit breaker.

FIG. 12 is an explanatory diagram illustrating a current distribution of the single-phase rectification bridge circuit after the circuit breaker is opened in the high-speed current limiting circuit device of FIG. 11;

FIG. 13 is a circuit diagram showing an electrical configuration of another conventional high-speed current limiting circuit breaker.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 High-speed current limiter 2 High-speed current limiter 3 High-speed current limiter 4 High-speed current limiter D1 Diode (rectifier) D2 Diode (rectifier) D3 Diode (rectifier) D4 Diode (rectifier) L1 Superconductivity Reactor (DC superconducting reactor) R1 resistor R2 resistor R3 resistor R4 resistor SW1 switch (short circuit) SW2 switch (short circuit) SW3 switch (short circuit) SW4 switch (short circuit) TH1 thyristor (short circuit) TH2 thyristor (short circuit) TH3 thyristor (rectifier) TH4 thyristor (rectifier)

Continuation of the front page (56) References JP-A-48-97042 (JP, A) JP-A-56-81039 (JP, A) JP-A-49-45349 (JP, A) JP-A-49-50448 (JP, A) , A) JP-A-9-130966 (JP, A) JP-A-11-4542 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02H 9/02 H02H 7/04 H02H 7/22 H01F 7/22 H01F 27/34 H01F 27/42

Claims (2)

(57) [Claims] 1. An electric power system comprising: two electric power systems;
As a boundary, provided with a single-phase rectifier bridge circuits, each rectifying element extending arms each AC terminal is interposed in the high-speed current-limiting breaker of the DC superconducting reactor between the two DC terminals are constituted by connecting If all the rectifiers are diodes, each AC terminal
It is interposed in series with at least one of the two arms one to be connected to, a diode arm when the rectifying element of the arm of one of the AC terminal side is rectifying element diode arms of the other AC terminal side thyristors At least one of
If the above rectifiers are all thyristors, they should be kept conductive even when an overcurrent flows.
A resistor interposed in series with at least one of the AC terminal side of the arm, the high-speed current-limiting breaker characterized in that it comprises a shorting means for shorting both ends of the resistor. 2. The high-speed current-limiting device according to claim 1, wherein said short-circuit means is a thyristor.