JP2006094658A - Interconnection system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an interconnection system which can prevent an important load from being influenced by preventing an instantaneous voltage drop in the case of a failure when interconnecting two different electric power systems. <P>SOLUTION: The interconnection system A is for supplying the electric power of the electric power systems different from each other by being systematically interconnected between the two different electric power systems. Circuit breakers 14 and 15; a current detector 16; and a current limiting circuit breaker 11 which is composed of a current limiter 12 constituted of parallel circuits of a switch circuit 12a, a varistor circuit 12b and a reactor circuit 12c, and a controller 13 for controlling the switch circuit of the current limiter are arranged between the two electric power systems different from each other. Thus, the current limitor 12 is constituted of the parallel circuits of the switch circuit 12a, the varister circuit 12b and the reactor circuit 12c, an abnormal overcurrent being made to be a small safety current in a short time, and an important load can be protected by preventing instantaneous power interruption and an instantaneous voltage drop in the case of the failure of the electric power system. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is to link a power system of a load that is connected to and connected to two different power systems of a commercial power system and a private power system, in order to avoid a momentary power failure or an instantaneous voltage drop at the time of an accident of the power system This relates to the grid interconnection system.

  There are important facilities (demand loads) that must be avoided even in the event of a momentary power failure or instantaneous voltage drop, and a private power supply system is provided as a countermeasure for this. The conventional grid interconnection system is connected to a commercial power distribution main line in a customer where commercial power is drawn from the distribution line, and is supplied to a general load connected to the commercial power distribution branch line via the commercial distribution main line. It is configured. On the other hand, the private power source consisting of private power generation is connected to a private distribution main line different from the commercial distribution main line connected to the commercial power supply, and is supplied to the important load connected to the private distribution branch line via the private distribution main line. It is configured. A bidirectional thyristor circuit in which the polarity of the thyristor is connected in parallel with the reverse polarity is connected between the commercial power distribution main line and the private power distribution main line, and interconnection connection is configured between the commercial power supply system and the private power supply system.

As an example, Patent Document 1 discloses a grid interconnection system including a bidirectional thyristor circuit in which the polarities of such thyristors are connected in parallel with opposite polarities.
Japanese Patent Laid-Open No. 9-93814

  However, in the grid interconnection system having the bidirectional thyristor circuit in which the polarity of the thyristor is connected in parallel with the reverse polarity, the output from the relay is not shown in the grid connection between the commercial distribution trunk line and the private distribution trunk line. The gate of the bi-directional thyristor circuit is driven to maintain the conduction state, but if a fault such as a lightning surge or a short circuit, a ground fault or an open of the commercial power supply system occurs, the relay is cut off and the thyristor circuit is driven. Although it is possible to cut off within 20 ms (in the case of 50 Hz), it is inevitable that a short-circuit current flows and a large voltage drop occurs during this time. The time required to shut off the bidirectional thyristor circuit is short, so it is possible to avoid stopping the private power supply.However, the instantaneous voltage drop cannot be avoided, and the important load connected to the private power distribution main line is affected. Had.

  An object of the present invention is to provide a grid interconnection system capable of preventing an instantaneous voltage drop at the time of failure and not affecting an important load when grid-linking two different power systems described above. It is.

  In order to achieve the above-described object, the present invention is a system interconnection system that is firstly grid-connected between two different power systems and supplies power from different power systems. A current limiter comprising a parallel circuit of a circuit breaker, a current detector, a switch circuit, a varistor circuit, and a reactor circuit, and a controller for controlling the switch circuit of the current limiter between two different power systems A second current limiting circuit breaker is arranged, and secondly, the reactor constituting the reactor circuit is a cored reactor.

  Since this invention has the structure mentioned above, there can exist the effect described below.

  In the grid interconnection system of the present invention, as described above, a current limiter comprising a parallel circuit of a circuit breaker, a current detector, a switch circuit, a varistor circuit, and a reactor circuit between two different power systems. And a controller that controls the switch circuit of the current limiter are arranged, so that the switch circuit of the current limiter is instantaneously opened by detecting the abnormal current of the current detector. The arc discharge generated between the terminals of the switch circuit due to the opening of the switch circuit is instantaneously absorbed by the varistor circuit connected in parallel to the switch circuit and becomes the limit voltage of the varistor circuit. The arc discharge becomes unsustainable and the arc disappears. When the arc disappears, the abnormal current flowing in the switch circuit is commutated to the varistor circuit and the reactor circuit, and most of the abnormal current flows to the reactor circuit due to the resistance value ratio between the varistor circuit and the reactor circuit. After that, the abnormal current flowing in the reactor circuit is limited by the relational expression of impedance Z = R + jωL from the characteristics of the reactor circuit, and this limited current becomes a current flowing from the private power supply system to the commercial power supply system, The voltage drop of the power supply system can be suppressed. Thereafter, the circuit breaker is opened, and the commercial power supply system and the private power supply system are disconnected, thereby ensuring the power supply to the important load of the private power supply system.

  As described above, since the current limiter 12 is configured as a parallel circuit of the switch circuit 12a, the varistor circuit 12b, and the reactor circuit 12c, an excessive abnormal current can be reduced to a small safe current in a short time, so that the power system can be It is possible to protect the important load by avoiding instantaneous power failure and instantaneous voltage drop.

  Moreover, since the reactor which comprises a reactor circuit was made into the reactor containing an iron core, the resistance component of a reactance can be obtained largely, Therefore Therefore, the effect that the limiting current limit by resistance becomes large can be increased.

  Examples of the present invention will be described below. However, the present invention is not limited to the examples as long as the gist of the present invention is not exceeded.

  Reference numeral 1 denotes a commercial power supply system. The commercial power supply system 1 has a commercial distribution line 3 for introducing a commercial power supply 2 into a consumer, and is connected to a commercial distribution main line 4 in the consumer via the commercial distribution line 3. It is connected. Reference numeral 5 denotes a plurality of commercial power distribution branches branched from the commercial power distribution trunk line 4, and a plurality of general loads R <b> 1 are connected to the commercial power distribution branch line 5.

  Reference numeral 6 denotes a private power supply system. The private power supply system 6 has a private distribution line 8 connected to a private power supply 7, and the private distribution line 8 is connected to a private distribution main line 9. Reference numeral 10 denotes a plurality of private power distribution branch lines branched from the private power distribution trunk line 9, and a plurality of important loads R <b> 2 are connected to the private power distribution branch line 10.

  Reference numeral 11 denotes a current limiting circuit breaker, which is connected between the commercial distribution line 3 and the private distribution line 8 and is interconnected. The current limiting circuit breaker 11 opens and closes a current limiting device 12 including a switching circuit 12a and a varistor circuit 12b and a reactor circuit 12c connected in parallel to the switching circuit 12a, and the switching circuit 12a of the current limiting device 12, respectively. The controller 13 for controlling, the circuit breakers 14 and 15 connected to both ends of the current limiter 12, and the current more than a predetermined value connected to one line on the commercial distribution line 3 side flowed. And a current detector 16 for detecting.

  As described above, the grid interconnection system A is composed of the commercial power supply system 1, the private power supply system 6, and the current limiting breaker 11.

  Next, the operation of the grid interconnection system A having the above-described components will be described.

  The electric power of the commercial power supply system 1 is supplied from the commercial power supply 2 to the general load R1 connected to the commercial distribution branch line 5 branched from the commercial distribution main line 4 via the commercial distribution line 3. On the other hand, the electric power of the private power supply system 6 is supplied from the private power supply 7 to the important load R2 connected to the private power distribution branch line 10 branched from the private distribution main line 9 via the private distribution line 8. Further, power is supplied from the commercial power supply system 1 to the important load R2 of the private power supply system 6 to configure the grid interconnection system A.

  Now, when a lightning surge or the like is applied to the commercial power supply system 1, the current detector 16 installed in the grid interconnection system A detects an abnormal current, gives a detection signal to the controller 13, and configures the current limiter 12. The switch circuit 12a is opened. When the switch circuit 12a is opened, arc discharge occurs at both ends of the open end. When arc discharge occurs, a current is also applied to the varistor circuit 12b, and the voltage across the varistor circuit 12b becomes the varistor limit voltage value. Then, the voltage at both ends of the switch circuit 12a also decreases to the same value as the varistor voltage value. At this time, arc discharge cannot be maintained and is stopped.

  When the arc discharge at the open end of the switch circuit 12a stops, the abnormal current then commutates to the varistor circuit 12b and the reactor circuit 12c in parallel with the switch circuit 12a. The abnormal current commutated to the varistor circuit 12b and the reactor circuit 12c is proportional to the resistance ratio between the varistor circuit 12b and the reactor circuit 12c, and most of the abnormal current flows to the reactor circuit 12c. When an abnormal current flows through the reactor circuit 12c, an abnormality is found from the relational expression of impedance Z = R + jωL of the reactor 12c (where Z = impedance, R = DC resistance, L = reactance, ω = 2πf, f = frequency). The current becomes a limited small current, and the current flowing from the private power supply system 6 to the commercial power supply system 1 is also suppressed to the limited small current. Therefore, the voltage drop of the private power supply system 6 can be suppressed, Normal voltage can be maintained. Thereafter, the circuit breakers 14 and 15 are opened, the system interconnection is disconnected, the commercial power supply system 1 and the private power supply system 6 are disconnected, and the important load R2 of the private power supply system 6 is protected. .

  As described above, when the abnormal current is detected by the current detector 16, the switch circuit 12 a is opened via the controller 13 by the detection signal from the current detector 16. When the switch circuit 12a is opened, arc discharge occurs at both ends of the open end of the switch circuit 12a. However, the voltage at both ends of the switch circuit 12a is changed by the operation of the varistor circuit 12b in parallel with the switch circuit 12a. Because of the voltage value, the arc discharge stops because the discharge cannot be continued. The abnormal current is commutated to the varistor circuit 12b and the reactor circuit 12c, but most of the abnormal current flows to the reactor circuit 12c and to the reactor circuit 12c due to the resistance ratio between the varistor circuit 12b and the reactor circuit 12c. The abnormal current that flows is limited, and the limited and reduced current flows from the private power supply system 6 to the commercial power supply system 1, and thus the voltage drop of the private power supply system 6 is suppressed. Then, the circuit breakers 14 and 15 are opened, and the commercial power supply system 1 and the private power supply system 6 are disconnected, so that the important load R2 of the private power supply system 6 is protected.

  As described above, since the current limiter 12 having the parallel circuit of the switch circuit 12a, the varistor circuit 12b, and the reactor circuit 12c is disposed, the system is normally connected by the switch circuit 12a, and abnormal current is generated. When this occurs, the switch circuit 12a opens to cause arc discharge. When arc discharge occurs, the varistor circuit 12b operates to stop the arc discharge, and abnormal current is commutated to the varistor circuit 12b and the reactor circuit 12c. Then, since the current is made small in the reactor circuit 12c, the time until the circuit breakers 14 and 15 are opened can be shortened, so that the current capacity of the varistor circuit 12b and the reactor circuit 12c can be reduced. It is possible to reduce the size and cost, and to deal with an excessive abnormal current.

  As described above, since the current limiter 12 is configured as a parallel circuit of the switch circuit 12a, the varistor circuit 12b, and the reactor circuit 12c, an excessive abnormal current can be reduced to a small safe current in a short time, so that the power system can be It is possible to protect the important load by avoiding instantaneous power failure and instantaneous voltage drop.

  It is preferable that the reactor constituting the reactor circuit 12c is an iron cored reactor, and by configuring in this way, the resistance component of the reactance L can be increased, so that the limited current limit due to the resistance is large. The effect can be increased.

  In the above-described embodiment, two circuit breakers 14 and 15 are arranged. However, it is not always necessary to arrange two circuit breakers, and only one of the circuit breakers may be provided.

FIG. 1 is a configuration diagram of a grid interconnection system of the present invention. FIG. 2 is a configuration diagram of a current limiting device constituting the grid interconnection system of the present invention.

Explanation of symbols

A ······ Grid connection system 1 ···························································· Commercial power distribution line 4・ ・ Commercial distribution trunk line 5 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Commercial distribution branch line 6 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Private power supply system 7 ・ ・ ・ ・ ・ Private power supply 8 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Private distribution line 9 ・・ ・ ・ ・ ・ ・ Private distribution trunk line 10 ・ ・ ・ ・ ・ ・ Private distribution branch line 11 ・ ・ ・ ・ ・ ・ Current limiting circuit breaker 12 ・ ・ ・ ・ ・ ・ Current limiting device 12a ・ ・ ・ Switch circuit 12b ・・ ・ ・ ・ Varistor circuit 12c ・ ・ ・ Reactor circuit 13 ・ ・ ・ ・ ・ ・ Controller 14, 15 ・ ・ ・ Circuit breaker 16 ・ ・ ・ ・ ・ ・ Current detector

Claims (2)

  A grid interconnection system that is grid-connected between two different power grids and supplies power from different power grids, and includes a circuit breaker and a current detector between the two different power grids. And a current limiter comprising a parallel circuit of a switch circuit, a varistor circuit, and a reactor circuit, and a controller for controlling the switch circuit of the current limiter. system.   The grid interconnection system according to claim 1, wherein the reactor constituting the reactor circuit is a cored reactor.

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