JP4086234B2 - Distribution line connection method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for connecting distribution lines that connect a plurality of distribution lines of a high-voltage distribution system to each other.
[0002]
[Prior art]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-125318
In power distribution systems, voltage fluctuations due to load fluctuations are reduced and minimization of power outage sections is required in the event of a failure. A distribution system that can stabilize the current and voltage of each distribution system when there are load fluctuations and fluctuations in power flow from distributed power sources, and can improve the equipment utilization rate of each distribution system and reduce power loss. A power flow control method is disclosed in Japanese Patent Laid-Open No. 2002-125318. The power flow control method for the distribution system disclosed in Japanese Patent Application Laid-Open No. 2002-125318 discloses a method of connecting a series-type active filter between distribution lines and flowing a correction current of a commercial frequency between the distribution lines to reduce the flow of each distribution line. The current of each distribution line can be controlled, and the power loss of the distribution line can be reduced by balancing the currents of the distribution lines.
[0004]
In general, as shown in FIG. 6, the distribution system includes a plurality of distribution lines (feeders) connected to the high-voltage bus 2 connected to the secondary side of the main transformer 1 through circuit breakers (CB) 3, 4, 5, 6. ) 7, 8, 9, 10 are connected to form a dendritic system. Faults occurring in the distribution lines 7, 8, 9, and 10 include a short circuit and a ground fault. An overcurrent relay (not shown) is used for the short circuit, and a ground fault direction relay (DGR) 11 is used for the ground fault. 12, 13, 14 and a ground fault overvoltage relay (not shown) are installed, respectively, and trip through the circuit breakers 3, 4, 5, 6 of any of the distribution lines 7, 8, 9, 10 detected by these A protective device is provided. In the figure, reference numerals 15, 16, 17, and 18 denote zero-phase current transformers that detect the zero-phase current and apply it to the ground fault direction relays 11, 12, 13, and 14. Each wiring line indicated by a single line in the figure. 7, 8, 9, 10 are three-phase, three-wire, and a load is connected between the wires, the high-voltage distribution system is ungrounded, and between each distribution line 7, 8, 9, 10 and the ground Needless to say, there are capacitance and leakage resistance (not shown).
[0005]
In such a distribution system, when a ground fault occurs in the distribution line 10, sound distribution lines 7, 8, 9 are transmitted from the high-voltage bus 2 side to the distribution line 10 side in the failed distribution line 10 as shown in FIG. 7. Then, a fault current flows from the distribution lines 7, 8, 9 side to the high voltage bus 2 side. Since the direction of the fault current is reverse between the faulty distribution line 10 and the healthy distribution lines 7, 8, 9, the faulty distribution line 10, is identified by the ground fault relays 11, 12, 13, 14. Then, the circuit breaker 6 of the distribution line 10 is opened.
[0006]
At this time, if the distribution line 9 is connected to the distribution line 10 as shown in FIG. 8, the failure current flows from the distribution line 9 connected to the failed distribution line 10 toward the failure point. become. Therefore, the fault current flows from the high-voltage bus line 2 side to the distribution line path 9 and 10 side in the distribution line paths 9 and 10, and from the distribution line path 7 and 8 side to the high-voltage bus line 2 side in the healthy distribution line paths 7 and 8. There is a disadvantage that 9 cannot be identified as healthy. In order to avoid this inconvenience, conventionally, it has been considered that the high voltage distribution line cannot be configured as a loop system or a mesh system, and is a dendritic system. For this reason, in the event of a failure, the power outage section is minimized by means such as reverse transmission.However, after a power outage, it is necessary to retransmit power after operating a switch to configure a new dendritic system. There was a problem that it took time and effort to transmit power.
[0007]
In addition, the power flow control method for a distribution system disclosed in Japanese Patent Application Laid-Open No. 2002-125318 is such that a series-type active filter is connected between distribution lines, and a correction current is supplied between the distribution lines to optimize the flow of each distribution line. By controlling, it is useful to improve the equipment utilization rate and reduce the power loss of the distribution line, but since the series-type active filter also transmits the zero-phase current, the ground fault direction relay 11 as described above, 12, 13, 14 and the protection method using the ground fault overvoltage relay, there is a problem that the failed distribution line and the healthy distribution line cannot be distinguished, and the failed distribution line cannot be selectively cut off. .
[0008]
[Problems to be solved by the invention]
The present invention solves the above-mentioned conventional problems, and even if the distribution line is connected and the high-voltage distribution line is configured in a loop system or a mesh system, the distribution line in which a failure has occurred is selectively blocked by the conventional protection method. It is made in order to provide the connection method of the distribution line which can do.
[0009]
[Means for Solving the Problems]
The distribution line connection method of the present invention made to solve the above problems is a distribution line connection method for connecting a plurality of distribution lines, and the zero-phase impedance is low in the normal phase and the negative phase impedance. The distribution lines are connected to each other through a zero-phase current suppressing device having a high impedance.
The zero-phase impedance of the zero-phase current suppression device is preferably set to a value sufficiently higher than the zero-phase impedance of the distribution line from the point where the zero-phase current suppression device is connected to the power source. The suppression device can be a common mode coil. In addition, it is possible to release the connection between distribution lines by connecting a switch in series to the zero-phase current suppression device, or to connect a fuse in series to the zero-phase current suppression device to protect against short-circuit faults. Furthermore, a series-type active filter is connected in series to the zero-phase current suppression device, and the positive-phase current and the reverse-phase current flowing between the distribution lines connected to each other by the active filter are controlled. be able to.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of the present invention will be specifically described.
FIG. 1 shows a first embodiment, and between the distribution line paths 7 and 8 of the general distribution system as shown in FIG. 6, between the distribution line paths 8 and 9, and between the distribution line paths 9 and 10, respectively. It is connected via the zero-phase current suppression devices 19, 20, and 21, and the distribution system can be configured as a loop system or a mesh system by appropriately connecting the distribution line paths in this way. In FIG. 1, the protective device, the load, the electrostatic capacity, the leakage resistance, and the like existing between the distribution lines 7, 8, 9, 10 and the ground are omitted.
[0011]
The zero-phase current suppression devices 19, 20, 21 can be common mode coils configured by winding three coils 23, 24, 25 on a common core 22, as shown in FIG. As shown in FIG. 3, it is assumed that the transformer is composed of single-phase transformers 26, 27, and 28, and the secondary windings of the transformers 26, 27, and 28 are connected in parallel and terminated with a termination impedance 29. it can. One end a, b, c and the other end a ′, b of the primary windings of the coils 23, 24, 25 or the transformers 26, 27, 28 of the zero-phase current suppressing devices 19, 20, 21 thus configured. ', C' is connected to the three-phase lines of the distribution lines 7, 8, 9 and the three-phase lines of the same phase of the distribution lines 8, 9, 10 connected to each other.
[0012]
As described above, if the distribution line paths 7 and 8, the distribution line paths 8 and 9, and the distribution line paths 9 and 10 are respectively connected via the zero-phase current suppression apparatuses 19, 20, and 21, the zero-phase current suppression apparatus 19. , 20, 21, normal phase and reverse phase currents flow between the distribution lines 7, 8, 9, 10, and normal phase and reverse phase currents flowing through the distribution lines 7, 8, 9, 10 average It changes in the direction to be converted. In addition, the voltage of each distribution line at the connection point is also averaged. When the power supply side is viewed from the load downstream from the connection point, the mutually connected distribution line paths 7, 8, 9, 10 are connected in parallel, and the loss in the distribution line paths 7, 8, 9, 10 Will be reduced.
[0013]
When a ground fault occurs in the distribution line 10 in a state where the distribution lines 7 and 8, the distribution lines 8 and 9, and the distribution lines 9 and 10 are connected via the zero-phase current suppression devices 19, 20, and 21, respectively. As shown in FIG. 4, in the distribution line 10 in which a failure has occurred, a failure current flows from the high-voltage bus 2 side to the distribution line 10 side. At this time, the fault current flowing from the distribution line 9 connected to the distribution line 10 toward the failure point is suppressed by the zero-phase current suppression device 21. If the zero-phase impedance of the zero-phase current suppression device 21 is a value sufficiently higher than the zero-phase impedance to the power source of the distribution line 9, the failure current flowing from the distribution line 9 toward the failure point can be ignored. As a result, a failure current flows from the distribution line 9 side to the high-voltage bus line 2 side even in the distribution line 9, so that the failed distribution line 10 can be selectively cut off even with the conventional protection method, and the distribution system is connected to the loop system. Or a mesh system.
[0014]
FIG. 5 shows a second embodiment, in which a zero-phase current suppression device 19 and a series-type active filter 30 are connected in series between distribution lines 7 and 8. In FIG. 5, the zero-phase current suppressing device 19 is configured as shown in FIG. The active filter 30 itself is the same as that known as a filter for removing harmonics, and is connected to the distribution line 8 to convert the AC power source to DC, and the DC power of the converter 31 is changed to AC power. It comprises an inverter 32 to be converted, a filter 33 for adjusting the waveform of the inverter 32, a transformer 34 for applying a current between distribution lines, and a capacitor 35 connected to the DC input side of the inverter 32. Needless to say, the converter 31 is for generating power for the inverter 32 and may be connected to the distribution line 7.
[0015]
Although not shown, current and voltage sensors are provided in the distribution line paths 7 and 8, and current and voltage sensors and arithmetic units are provided in the active filter 30, and distribution is performed at the point where the distribution line paths 7 and 8 are connected to each other. When there is a difference between the supply current from the line 7 and the supply current from the distribution line 8, the correction current is calculated and the active filter is operated to balance the supply current from the distribution line 7 and the supply current from the distribution line 8. Let When a ground fault occurs in the distribution line 7 or 8, the zero-phase current suppression device 19 suppresses the failure current flowing between the distribution lines 7 and 8 connected to each other, as in the case of the first embodiment. Similarly, the distribution line 7 or 8 in which a failure has occurred can be selectively cut off with the conventional protection method, and the distribution system can be configured as a loop system or a network system according to the second embodiment. Become.
[0016]
In the first embodiment, current flows between distribution lines connected to each other through the zero-phase current suppression device, and the current flowing through each distribution line is averaged. It depends on the impedance of the line. In addition, when there is a difference in the capacity of distribution lines, it may be inconvenient if they are averaged as they are. According to the second embodiment, there is an advantage that the current can be optimally distributed by distributing the current between the distribution lines by the active filter 30.
[0017]
As shown in FIGS. 2 to 4, the zero-phase current suppressing device can be constituted by a common mode coil or three single-phase transformers. The common mode coil has an extremely simple configuration. On the other hand, when three single-phase transformers are used, the degree of freedom of arrangement increases and the characteristics of the zero-phase current suppressing device can be adjusted by the termination impedance. is there. In addition, if a switch is connected in series to the zero-phase current suppression device and the connection between the distribution lines can be released, it becomes easy to change the configuration of the distribution system at the time of failure, etc. Protection coordination can be easily achieved by connecting a switch such as a current limiting fuse in series to the zero-phase current suppressing device. In addition, when a ground fault occurs in the system to which the zero-phase current suppression device is connected, the switch is opened to prevent the ground fault from continuing and prevent the influence on the sound distribution line. It becomes possible.
[0018]
【The invention's effect】
As described above, according to the distribution line connection method of the present invention, by connecting between the distribution line paths through the zero-phase current suppressing device, the loop system and the mesh system remain in the conventional protection system. A power distribution system can be configured. This makes it easy to change the configuration of the distribution line system for minimizing the power outage section in the event of a failure, disperse the load current, improve the equipment utilization rate of the distribution line, and reduce the power loss of the distribution line. Has an excellent effect. Therefore, the present invention provides a method for connecting a distribution line that solves the conventional problems, and has an extremely great industrial value.
[Brief description of the drawings]
FIG. 1 is a system diagram showing a first embodiment;
FIG. 2 is a configuration diagram illustrating an example of a zero-phase current suppressing device.
FIG. 3 is a configuration diagram showing another example of the zero-phase current suppressing device.
FIG. 4 is a diagram showing a flow of a fault current in the first embodiment.
FIG. 5 is a block diagram of a main part showing a second embodiment.
FIG. 6 is a diagram showing a configuration of a general distribution line system.
FIG. 7 is a diagram showing a flow of a fault current in a general distribution line system.
FIG. 8 is a diagram showing a flow of a fault current when distribution lines are connected to each other.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Main transformer 2 High voltage bus 3, 4, 5, 6 Circuit breaker 7, 8, 9, 10 Distribution line 11, 12, 13, 14 Ground fault direction relay 15, 16, 17, 18 Zero phase current transformer 19, 20, 21 Zero phase current suppression device 22 Core 23, 24, 25 Coils 26, 27, 28 Single phase transformer 29 Termination impedance 30 Active filter 31 Converter 32 Inverter 33 Filter 34 Transformer 35 Capacitor

Claims (6)

A distribution line connection method for connecting a plurality of distribution line paths, wherein the distribution line paths are connected via a zero-phase current suppression device having a low normal phase impedance and a negative phase impedance and a high zero phase impedance. A distribution line connection method characterized by the above. The zero-phase impedance of the zero-phase current suppression device is set to a value sufficiently higher than the zero-phase impedance of the distribution line from the point where the zero-phase current suppression device connects each other to the power source. The connection method of the distribution line path of description. 3. The distribution line connection method according to claim 1, wherein the zero-phase current suppression device is a common mode coil. 4. The distribution line connection method according to claim 1, wherein a switch is connected in series to the zero-phase current suppression device, and the connection between the distribution line paths can be released. 5. The distribution line connection method according to claim 1, wherein a fuse is connected in series to the zero-phase current suppressing device to protect against a short-circuit failure. 6. A series-type active filter is connected in series to a zero-phase current suppressing device, and a positive-phase current and a reverse-phase current flowing between distribution lines connected to each other by the active filter are controlled. The distribution line connection method according to any one of the above.

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