JP3249830B2 - Transformer operation system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a transformer operating system in a distribution substation having a plurality of transformers.

[0002]

2. Description of the Related Art As shown in FIG. 6, in a distribution substation having two or more transformers 20, each transformer 20 has a plurality of distribution lines 21.
In the normal operating state, the buses 22 on the secondary side of each transformer 20 are interconnected by a bus-barrier circuit breaker 23 in an off state. However, when the power demand increases in the summer, for example, the load sharing among the transformers 20 becomes unbalanced, and the transformer utilization may decrease. Therefore, in such a case, in order to improve the supply reliability and equalize the load sharing, it is conceivable to perform the parallel operation by a plurality of transformers 20 with the bus-bar communication circuit breaker 23 turned on.

However, in a distribution system that performs such a transformer parallel operation, when a short circuit fault occurs in the distribution line 21, the fault current from the plurality of transformers 20 is much larger than when the transformer 20 is used alone. Flow toward the accident point, the breaking capacity of the distribution line breaker 24 installed on each distribution line 21 may be exceeded, and the distribution line breaker 24 operates in this state. In case of circuit breaker 24
May be damaged. For this reason, if the fault current exceeds a predetermined value, a method that does not operate the distribution circuit breaker 24 may be considered, but in this case, the circuit breaker 25 on the primary side of the transformer is considered.
Must be operated to suppress the fault current, and there has been a problem that the supply of power to a large number of distribution lines 21 is stopped and the blackout section is wide.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems in the prior art, and performs parallel operation by a plurality of transformers in order to improve the supply reliability and level the load sharing among the transformers. It is an object of the present invention to provide a transformer operation system that can perform the operation and can reliably operate only the distribution line breaker of the distribution line when an accident occurs in any of the distribution lines.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an interconnection between buses on the secondary side of a plurality of transformers via a semiconductor device and a connection to each bus.
A detection section detecting a failure of the distribution line to the circuit breaker for power distribution lines and distribution lines to be continued provided, also the fault current exceeds a predetermined value to the semiconductor device is detected from the detection unit in a state of ON in the above semiconductor device If the fault current does not exceed the specified value, the semiconductor device is turned off before the circuit breaker for the faulty distribution line turns off.
Turn off only the distribution line breaker provided for the
In which it characterized in that a monitoring control unit for off.

[0006]

According to the present invention, by turning on a semiconductor device provided between buses on the secondary side of a plurality of transformers, load sharing among the transformers can be balanced. Even if one transformer stops due to an accident or the like, power distribution can be continued by the remaining transformers. Also, when an accident has occurred in any of the distribution lines during the parallel operation with the semiconductor device turned on, and it is determined that the accident current detected by the detection unit has exceeded the breaking capability of the circuit breaker for the distribution line, the monitoring control unit Turns off the semiconductor device before the distribution line breaker. For this reason, the fault current flowing toward the fault point is only the current flowing from one transformer, and then the fault can be cut off by the distribution line breaker. Note that the semiconductor device may be turned on immediately after the distribution line breaker is turned off, and parallel operation may be started.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to the illustrated embodiments. In FIG. 1, 1 and 1 are two transformers,
Reference numerals 2 and 2 denote buses of the transformers 1 and 1, respectively. The buses 2 and 2 are interconnected via a semiconductor device 3 capable of high-speed interruption instead of a conventional bus-barrier circuit breaker. A plurality of distribution lines 4 are connected to each bus 2, 2, and each distribution line 4 is provided with a distribution line breaker 5 and a detection unit 6 located on the load side thereof. Reference numeral 7 denotes these detectors 6
And a semiconductor control unit 8 connected to the monitor control unit 7.

The semiconductor device 3 used in the present invention has a semiconductor device 9 such as a thyristor connected in anti-parallel as shown in FIG. 2, for example. In addition, the capacity can be increased, the load on the semiconductor element 9 can be reduced, and the reliability of the device can be improved.

The detection section 6 has the function shown in the block diagram of FIG. 3, and outputs a signal from the output circuit to the monitoring control section 7 when the fault current flowing through the distribution line 4 exceeds a predetermined value. . Here, the level of the predetermined value is set to be equal to or less than the rated breaking current of the circuit breaker 5 for distribution lines. It should be noted that a conventional current transformer and a relay can be used for the detection unit 6.

Next, the operation of the system of the present invention will be described.
First, the semiconductor device 3 is turned off during normal operation,
As described above, when power demand increases,
A plurality of transformers 1 and 1 are operated in parallel. When an accident occurs in any of the distribution lines 4 in this state, an accident current is detected by the detection unit 6, and the monitoring control unit 7 determines the level as shown in the flow sheet of FIG.

When the semiconductor device 3 is on and the fault current detected by the detector 6 exceeds a predetermined value, the distribution line circuit breaker 5 provided on the distribution line 4 is turned off. First, the monitoring control unit 7 turns off the semiconductor device 3. As a result, each of the transformers 1 and 1 shifts to the isolated operation, so that only the current flows from the transformer 1 on one side at the fault point, and the fault current decreases. In this state, the distribution line circuit breaker 5 provided on the distribution line 4 in which the accident has occurred is turned off to interrupt the accident current. When the fault current does not exceed the predetermined value, the monitoring control unit 7 turns off only the distribution line circuit breaker 5 to cut off the fault current without turning off the semiconductor device 3. After the fault current is cut off by turning off the distribution line circuit breaker 5 in this way, the monitoring control unit 7 immediately turns on the semiconductor device 3 and restarts the parallel operation.

As described above, the level of the predetermined value of the fault current at which the monitoring control unit 7 turns off the semiconductor device 3 is set to be equal to or lower than the rated breaking current of the circuit breaker 5 for distribution lines. Suppose this level is 12.5 kA, which is the short-circuit current value of a general distribution line.
FIG. 5 is a graph obtained by calculating the distance from the substation outlet and the short-circuit current value at that point. According to this figure, the short-circuit current (fault current) flowing through distribution line 4 is only 1 when an accident occurs within 0.3 km from the substation.
In the case of an accident at a point farther than 2.5 kA, the value becomes 12.5 kA or less due to the impedance of the distribution line. Therefore, it can be seen that in most accidents, the distribution line in which the accident has occurred can be separated by the distribution circuit breaker 5 without operating the semiconductor device 3.

[0013]

As described above, according to the transformer operation system of the present invention, a plurality of transformers can be operated in parallel, so that the facility utilization rate can be improved, and one transformer can be used. Even if the power supply is stopped due to a failure or the like, power distribution can be continued without interruption by the remaining transformer. Further, according to the present invention, even when an accident occurs in a distribution line during parallel operation of a plurality of transformers, only the distribution line can be separated, and the range of power failure can be minimized. Further, according to the present invention, since the semiconductor device is turned off only when the fault current exceeds a predetermined value, unnecessary operations can be eliminated. Further, the transformer operating system of the present invention can make the most of the conventional equipment and reduce the equipment cost.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a circuit diagram of a semiconductor device.

FIG. 3 is a block diagram illustrating functions of a detection unit.

FIG. 4 is a flow sheet showing the operation of the system of the present invention.

FIG. 5 is a graph showing a relationship between a distance from a substation to an accident occurrence point and a magnitude of an accident current.

FIG. 6 is a circuit diagram showing a conventional power distribution system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transformer 2 Busbar 3 Semiconductor device 4 Distribution line 5 Circuit breaker for distribution line 6 Detector 7 Monitoring and control unit 8 Semiconductor control unit

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02J 3/38 H02H 7/22 H02J 3/04

Claims (2)

(57) [Claims] An interconnection between buses on a secondary side of a plurality of transformers via a semiconductor device , and a distribution line breaker and a distribution line connected to each distribution line connected to each bus . A detection unit for detecting a failure is provided, and when the fault current detected by the detection unit exceeds a predetermined value in a state where the semiconductor device is turned on, a distribution unit provided in the failed distribution line is provided. Turn off the semiconductor device before the wire breaker turns off
If the fault current does not exceed the specified value,
An operation system for a transformer, comprising a monitoring control unit for turning off only a circuit breaker for a distribution line provided on an electric wire . 2. The operating system for a transformer according to claim 1, wherein the monitoring control unit turns on the semiconductor device after the distribution line breaker provided on the failed distribution line is turned off.