Distributed power supply distribution system and method for controlling the distributed power supply distribution system

Abstract

To provide a distribution system of a dispersed power supply which cooperates with an islanding prevention device and can prevent over-voltage when an earth fault occurs several times at the time of reverse flow from a dispersed power supply.SOLUTION: A distribution system 100 of a dispersed power supply comprises a distribution system 200 which supplies power to power demand units 10a to 10c via automatic switches 9a to 9h, and a distribution power supply site 21 which has a power supply 7b, an islanding prevention device 18, a breaker 8b for parallel-off which is connected with a high-voltage distribution line 5 and opened and closed based on an output signal of the islanding prevention device 18, a suppressing switch 17a of the islanding prevention device 18, a second ground type instrument transformer 3b, and a high resistivity ground switch 17b, and is connected with the distribution system 200 via the high-voltage distribution line 5 and supplies power to a load 22. At the time of an earth fault accident, when power flows reversely the distribution system 200 while the power supply 7b of the distribution power supply site 21 is a starting point, the neutral point of the distribution power supply site 21 is grounded via the high resistivity ground switch 17b temporarily using the second ground type instrument transformer 3b.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a distributed power supply distribution system for estimating a fault point when a power outage occurs in a power distribution system to which a distributed power supply site is connected, and a control method for the distributed power supply distribution system. [Background technology]

[0002] A conventional method for detecting fault points in a power distribution system is time-delayed sequential transmission. When a fault occurs on a distribution line, the distribution line is temporarily powered down by shutting off the sending circuit breaker at the distribution substation. After that, all automatic circuit breakers for the distribution line are opened. Next, the sending circuit breaker at the distribution substation is closed, and then the automatic circuit breakers that separate the distribution lines are closed in order of proximity to the distribution substation.

[0003] When the automatic switch is closed, power is restored to the fault section, causing a fault current to flow in the distribution line. This fault current is detected at the distribution substation and the sending circuit breaker is tripped. The automatic switch for the distribution line is then opened. At this time, the automatic switch immediately preceding the fault section is locked open to prevent it from being closed again.

[0004] Next, the sending-out circuit breaker of the distribution line is closed again, and then the automatic circuit breakers are closed, starting from the one closest to the distribution substation. The automatic circuit breaker just before the fault section is locked open and will not be closed. Through the above procedure, the fault section is detected and power is restored from the distribution substation to the section just before the fault section.

[0005] The time-delayed sequential transmission described above can detect that there are no faults between the distribution substation and the nearest fault section, but it cannot detect faults in the section beyond the fault section (healthy power outage section), and since it is blocked by the fault section, it is not possible to restore power to the healthy power outage section.

[0006] A distributed power distribution system to improve this situation is described, for example, in Patent Document 1. In this system, power is restored to the healthy power outage section by causing a reverse power flow from the power source at the distributed power source site to the healthy power outage section. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-148098 Summary of the Invention [Problem to be solved by the invention]

[0008] The distributed power supply distribution system described in Patent Document 1 detects a power distribution system fault and performs fault recovery taking into account the reserve capacity of the distributed power supply, but does not take into account cooperative operation with an islanding prevention device to prevent reverse power flow from the distributed power supply.

[0009] Furthermore, no consideration is given to suppressing potential changes and overvoltages at the neutral point of the distribution line when multiple ground faults occur during reverse power flow from a distributed power source.

[0010] Therefore, the present invention aims to provide a distributed power supply distribution system and a control method for a distributed power supply distribution system that can cooperate with an islanding prevention device and suppress overvoltage when multiple ground faults occur during reverse power flow from a distributed power supply. [Means for solving the problem]

[0011] In order to achieve the above object, the present invention is configured as follows.

[0012] A distributed power supply distribution system includes a distribution system that supplies power to a power demand unit via an automatic switch, a power source, an islanding prevention device, a parallel-off circuit breaker connected to the high-voltage distribution line and opened and closed based on an output signal from the islanding prevention device, a suppression switch of the islanding prevention device, a second grounding type instrument transformer, and a distributed power supply site that is connected to the distribution system via the high-voltage distribution line and supplies power to a load, and in the event of a ground fault accident, when reverse power flow is caused to flow from the power source at the distributed power supply site to the distribution system, the second grounding type instrument transformer is used to temporarily ground the neutral point of the distributed power supply site via the high-resistance grounding switch.

[0013] Furthermore, in a control method for a distributed power system that includes a power distribution system that supplies power to a power demand unit via an automatic switch and a distributed power site that is connected to the power distribution system by a high-voltage distribution line and supplies power to a load, in the event of a ground fault, when reverse power flow is caused to flow from the power source at the distributed power site to the distribution system, the neutral point of the distributed power site is temporarily grounded via a high-resistance grounding switch using a second grounded-type instrument transformer. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a distributed power supply distribution system and a control method for a distributed power supply distribution system that can cooperate with an islanding prevention device and suppress overvoltage when multiple ground faults occur during reverse power flow from a distributed power supply. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic configuration diagram of a distributed power supply distribution system according to a first embodiment. [Figure 2A] 1 shows a voltage waveform of a high-voltage distribution line in Example 1. [Figure 2B] 10 is a diagram showing an example of a voltage waveform of a high-voltage distribution line different from that of the present invention. [Figure 3] FIG. 10 is a schematic configuration diagram of a main part of a distributed power supply distribution system according to a second embodiment. [Figure 4]FIG. 10 is a schematic configuration diagram of a distributed power supply distribution system according to a third embodiment. [Figure 5] FIG. 10 is a schematic configuration diagram of a distributed power supply distribution system according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. Note that the following description is merely an example, and the invention is not limited to the specific embodiments described below. The present invention can, of course, be modified into various embodiments, including the embodiments described below. [Example]

[0017] Example 1 The first embodiment will be described with reference to FIGS. 1, 2A and 2B.

[0018] FIG. 1 is a diagram showing a schematic configuration of a distributed power supply distribution system 100 according to a first embodiment.

[0019] 1, a distributed power supply distribution system 100 includes a power distribution system 200, a distributed power supply site 21, and a high-voltage power distribution line 5. The power distribution system 200 includes a distribution substation 1 and automatic switches 9a to 9h.

[0020] The high-voltage distribution line 5 connects the distribution substation 1, the high-voltage consumers 10a, 10b, and 10c, and the distributed power generation site 21.

[0021] Under normal circumstances, high voltage consumer 10a is supplied with power via automatic switches 9a to 9g, high voltage consumer 10b is supplied with power via automatic switches 9a to 9e and 9h, and high voltage consumer 10c is supplied with power via automatic switches 9a, 9b, and 9c.

[0022] The distribution substation 1 includes, as power sending-out facilities, a first earthed-type potential transformer 3a, a sending-out circuit breaker 8a, a first zero-phase-sequence current transformer 4, and a power source 7a.

[0023] The power distribution system also includes automatic switches 9a to 9h.

[0024] The distributed power source site 21 includes, as power receiving equipment, a second zero-phase current transformer 2a, a capacitor-type ground fault detector 11, and a parallel-off circuit breaker 8b, which are arranged on the high-voltage distribution line 5 within the distributed power source site 21. The distributed power source site 21 also includes an islanding prevention device 18, a power source 7b, a switchgear protection device 14, a load 22, and a power receiving control device 15, and supplies power to the load 22.

[0025] When power source 7b and distribution system 200 are operating in parallel, islanding prevention device 18 detects a power outage on the distribution system 200 side and trips parallel-off circuit breaker 8b. A third zero-phase-sequence current transformer 2b is provided in the connecting conductor from power source 7b to the on-site busbar, and if a fault current flows due to a failure in load 22, for example, third zero-phase-sequence current transformer 2b detects this. Then, in accordance with the detection signal from third zero-phase-sequence current transformer 2b, switching protection device 14 trips protective circuit breaker 8c to protect power source 7b.

[0026] The power receiving control device 15 turns off the parallel-off circuit breaker 8b based on the output from a zero-phase current sensor (not shown).

[0027] In the first embodiment, a suppression switch 17a for the islanding operation prevention device 18 is provided on a control line connecting the islanding operation prevention device 18 and the parallel-off circuit breaker 8b. Also, a second grounded potential transformer 3b and a high-resistance grounding switch 17b are provided to high-resistance ground the neutral point of the on-site power distribution system only during reverse power flow originating from the distributed power source site 21.

[0028] In this distributed power supply distribution system 100, if a single-line ground fault 30a occurs while the distribution substation 1, high-voltage customers 10a, 10b, and 10c, and the distributed power supply site 21 are operating in parallel, the first zero-phase-sequence current transformer 4 in the distribution substation 1 detects the fault current and trips the sending circuit breaker 8a. The automatic switches 9a to 9h detect the power outage and open.

[0029] Furthermore, the islanding prevention device 18 of the distributed power supply site 21 detects islanding operation and shuts off the parallel-off circuit breaker 8b. Within the distributed power supply site 21, islanding operation continues.

[0030] When power is restored, the sending circuit breaker 8a in the distribution substation 1 is closed, and the automatic switches 9a to 9h are closed in order of proximity to the distribution substation 1.

[0031] When automatic switch 9b is closed a certain time after automatic switch 9a is closed, a fault current flows due to single-line ground fault 30a. This fault current is detected by distribution substation 1, and sending circuit breaker 8a is tripped. Automatic switches 9a and 9b are opened, but automatic switch 9b is locked open because the time it takes for it to become voltage-free after closing is short.

[0032] After a certain time, the sending circuit breaker 8a in the distribution substation 1 is closed, and then the automatic switchgear 9a is closed, completing the restoration of power. The automatic switchgear 9b is not closed because it is locked open.

[0033] A single-line ground fault 30a exists between automatic switches 9b and 9c, but whether or not a fault exists beyond automatic switch 9c (9c to 9h) cannot be detected by time-delayed sequential transmission starting from distribution substation 1.

[0034] In the first embodiment of the present invention, when reverse power flow occurs, the output of the islanding operation prevention device 18 is suppressed by a suppression switch 17a serving as an islanding operation prevention device suppressor within the distributed power source site 21. In addition, by turning on the high-resistance grounding switch 17b, the neutral point of the on-site power distribution system of the distributed power source site 21 is highly-resistively grounded by the second grounded-type potential transformer 3b.

[0035] In this state, when the parallel-off circuit breaker 8b is closed, a reverse power flow occurs, and a time-limited sequential transmission in the reverse direction starting from the distributed power source site 21 becomes possible.

[0036] Specifically, when automatic switches 9d and 9c are closed in sequence, a fault current will flow, so parallel-off circuit breaker 8b is shut off. Automatic switch 9c is locked open and will not be closed the next time power is restored, with power being restored up to just before automatic switch 9c. Next, when automatic switches 9e and 9f are closed, a fault current will flow, so parallel-off circuit breaker 8b at distributed power source site 21 is shut off.

[0037] Similarly, automatic switch 9f is locked open. Automatic switch 9d is also temporarily opened. Next, when parallel-off circuit breaker 8b at distributed power source site 21 is closed again and automatic switches 9d, 9e, and 9h are closed in sequence, power is restored to high-voltage consumers 10c and 10b by reverse power flow from distributed power source site 21.

[0038] By the above procedure, the presence or absence of an accident in the healthy power outage section is detected. If the power supply capacity of the distributed power supply site 21 is insufficient, power restoration may be stopped and power may be restored again only to an extent that corresponds to the power supply capacity of the distributed power supply site 21.

[0039] 2A and 2B show the system voltage when a line-to-ground fault occurs during reverse time-limited forward transmission starting from the distributed power source site 21 in FIG.

[0040] Figure 2A is an example according to embodiment 1 of the present invention, showing the system voltage when the neutral point of the on-site power distribution system within the distributed power source site 21 is high-resistance grounded by the second grounded-type potential transformer 3b, and Figure 2B is an example different from the present invention, showing the system voltage when the neutral point of the on-site power distribution system within the distributed power source site 21 is not high-resistance grounded by the second grounded-type potential transformer 3b.

[0041] In Figure 2A, when the line-to-ground fault converges, the neutral point potential of the system decays and approaches zero. After that, even if a line-to-ground fault occurs around 0.55 seconds, no overvoltage occurs.

[0042] On the other hand, in Figure 2B, after the single-line ground fault has converged, the neutral point potential of the system does not decay and a DC component remains. In this state, if a single-line ground fault occurs around 0.55 seconds, the amplitude of the transient potential oscillation increases by the amount of the shifted neutral point voltage, causing a large overvoltage.

[0043] Only during reverse time-limited forward transmission starting from the distributed power source site 21, the neutral point of the on-site power distribution system within the distributed power source site 21 is highly resistance grounded at the second grounded potential transformer 3b using the high resistance grounding switch 17b, thereby preventing the occurrence of overvoltage.

[0044] In any state other than reverse time-limited forward transmission starting from the distributed power source site 21, the sensitivity of earth fault current detection at the distribution substation 1 decreases, so high resistance grounding using the second grounded potential transformer 3b at the neutral point of the distribution system within the distributed power source site 21 is not performed.

[0045] According to the first embodiment of the present invention, when a ground fault occurs in the distributed power supply distribution system 100, reverse power flow is performed from the distributed power supply site 21 to the healthy power outage section, and the presence or absence of a fault section in the healthy power outage section is detected by time-limited forwarding (reverse time-limited forwarding) starting from the distributed power supply site 21, and the high-resistance second grounded instrument transformer 3b placed at the neutral point can prevent overvoltage in the distribution line when multiple ground faults occur during the reverse time-limited forwarding process, making it possible to safely perform reverse time-limited forwarding.

[0046] Therefore, it is possible to provide a distributed power supply distribution system 100 and a control method for a distributed power supply distribution system that can cooperate with an islanding prevention device 18 and suppress overvoltage when multiple ground faults occur during reverse power flow from the distributed power supply site 21.

[0047] Example 2 Next, a second embodiment of the present invention will be described.

[0048] FIG. 3 is a schematic configuration diagram of a distributed power source site 21 of a distributed power source power distribution system 100 according to a second embodiment.

[0049] The configuration of the distributed power supply power distribution system 100 other than the distributed power supply site 21 is the same as that of the first embodiment shown in FIG. 1, and therefore illustrations and detailed descriptions thereof will be omitted.

[0050] In the second embodiment, a protective transformer 23 is provided in the distributed power supply site 21. One end of the protective transformer 23 is connected to the load 22 and the high-resistance grounding switch 17b, and the other end of the protective transformer 23 is connected to the power supply 7b via a protective circuit breaker 8c.

[0051] A third grounded potential transformer 3c is connected to the connection point (neutral point) between the other end of the protective transformer 23 and the protective circuit breaker 8c.

[0052] In the second embodiment, the neutral point of the connection line from the protective transformer 23 to the power source 7b can be always connected to a high-resistance ground by the third grounding-type potential transformer 3c, enabling ground fault protection. In addition, reverse time-limited forwarding from the distributed power source site 21 is possible, and in that case, by turning on the high-resistance grounding switch 17b, the same effect as in the first embodiment can be obtained.

[0053] According to the second embodiment, it is possible to obtain the same effects as those of the first embodiment, and also to improve the ground fault protection performance of the distributed power supply site 21.

[0054] Example 3 Next, a third embodiment of the present invention will be described.

[0055] FIG. 4 is a schematic configuration diagram of a distributed power distribution system 100 according to a third embodiment.

[0056] 4, in this embodiment 3, a suppression switch 17a, a high-resistance grounding switch 17b, and a parallel-off circuit breaker 8b serving as islanding prevention device suppression switches in a distributed power source site 21 are operated by commands from a power distribution automation system (power distribution automation department) 24 of a central power dispatching center. The power distribution automation system 24 of the central power dispatching center controls the opening and closing operations of the suppression switch 17a, the high-resistance grounding switch 17b, and the parallel-off circuit breaker 8b based on an output signal from an islanding prevention device 18.

[0057] The power distribution automation system 24 also controls the opening and closing operations of the sending circuit breaker 8a and the automatic switches 9a and 9b.

[0058] According to the third embodiment, it is possible to obtain the same effects as those of the first embodiment, and also to perform cooperative control with the power distribution automation system 24 of the central load dispatching center, thereby further improving reliability and safety.

[0059] Example 4 Next, a fourth embodiment of the present invention will be described.

[0060] FIG. 5 is a schematic configuration diagram of a distributed power distribution system 100 according to a fourth embodiment.

[0061] The fourth embodiment will be described with reference to FIG.

[0062] In the first embodiment, the power receiving control device 15 was configured to shut off the protective circuit breaker 8c based on the output from a zero-phase current sensor (not shown), but in the fourth embodiment, the power receiving control device 15 and the islanding prevention device 18 in the distributed power source site 21 share the second zero-phase current transformer 2a and the capacitor-type ground fault detection device 11.

[0063] In other words, the output signal of the second zero-phase current transformer 2a and the output signal of the capacitor-type earth fault detector 11 are supplied to the islanding prevention device 18 and the power receiving control device 15, and the parallel-off circuit breaker 8b is opened or closed according to the output signal of the second zero-phase current transformer 2a or the output signal of the capacitor-type earth fault detector 11.

[0064] This makes it possible to omit the zero-phase current sensor.

[0065] According to the fourth embodiment, it is possible to obtain the same effects as those of the first embodiment, and in addition, it is possible to omit the zero-phase current sensor, thereby reducing the number of parts.

[0066] The fourth embodiment can also be applied to the second and third embodiments described above. [Explanation of symbols]

[0067] 1···Distribution substation, 2a···Second zero-phase current transformer, 2b···Third zero-phase current transformer, 4···First zero-phase current transformer, 3a···First earthed type voltage transformer, 3b···Second earthed type voltage transformer, 3c···Third earthed type voltage transformer, 5···High voltage distribution line, 7a, 7b···Power source, 8a···Sending circuit breaker, 8b···Parallel-off circuit breaker, 8c···Protection circuit breaker, 9a to 9h···Automatic switch, 10a, 10b, 10c··High voltage consumer ( Power demand section), 11···Capacitor-type earth fault detection device, 14···Switching protection device, 15···Power receiving control device, 17a···Suppression switch, 17b···High-resistance earthing switch, 18···Islanding prevention device, 21···Distributed power source site, 22···Load, 23···Protection transformer, 24···Automated distribution system (Automated distribution section), 30a, 30b··Single-line earth fault, 100··Distributed power source distribution system, 200···Distribution system

Claims

1. a power distribution system that supplies power to a power demand unit via an automatic switch; a distributed power source site connected to the power distribution system via the high-voltage distribution line and supplying power to a load, the distributed power source site including: a power source; an islanding prevention device; a parallel-off circuit breaker connected to the high-voltage distribution line and opened / closed based on an output signal of the islanding prevention device; a suppression switch of the islanding prevention device; a second grounding type potential transformer; and a high-resistance grounding switch; Equipped with A distributed power distribution system characterized in that, in the event of a ground fault, when reverse power flow is caused to flow from the power source at the distributed power site to the distribution system as a starting point, the neutral point of the distributed power site is temporarily grounded via the high-resistance grounding switch using the second grounded potential transformer.

2. 2. The distributed power supply distribution system according to claim 1, the distributed power source site includes a protective transformer, a third zero-phase current transformer, a third grounded voltage transformer, a protective circuit breaker, and a switchgear; a power supply connected to the neutral point and the load at the distributed power supply site via the protective circuit breaker, the third zero-phase current transformer, and the protective transformer; and when the third zero-phase current transformer detects a fault current, the switching protection device trips the protective circuit breaker.

3. 2. The distributed power supply distribution system according to claim 1, A distributed power supply distribution system characterized in that the opening and closing operations of the parallel-off circuit breaker, the suppression switch, and the high-resistance grounding switch at the distributed power supply site are controlled based on an output signal from the islanding prevention device.

4. 2. The distributed power supply distribution system according to claim 1, the distributed power source site includes a second zero-phase current transformer arranged on the high-voltage distribution line within the distributed power source site, a capacitor-type ground fault detector, and a power receiving control device; a power receiving control device that receives an output signal from the second zero-phase current transformer and an output signal from the capacitor-type earth fault detector, and opens and closes the parallel-off circuit breaker in accordance with the output signal from the second zero-phase current transformer or the output signal from the capacitor-type earth fault detector;

5. A control method for a distributed power system including a power distribution system that supplies power to a power demand unit via an automatic switch, and a distributed power site that is connected to the power distribution system by a high-voltage distribution line and supplies power to a load, comprising: A control method for a distributed power distribution system, characterized in that, during a ground fault accident, when a reverse power flow is caused to flow from the power source at the distributed power site to the distribution system, the neutral point of the distributed power site is temporarily grounded via a high-resistance grounding switch using a second grounded-type instrument transformer.

6. 6. The method for controlling a distributed power supply distribution system according to claim 5, a power supply connected to the neutral point and the load at the distributed power supply site via a protective circuit breaker, a third zero-phase current transformer, and a protective transformer, and wherein when the third zero-phase current transformer detects a fault current, the protective circuit breaker is tripped.

Images