JP2024015626A - Distribution system of dispersed power supply and control method of the same - Google Patents

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

The present invention relates to a distributed power distribution system and a method for controlling the distributed power distribution system for estimating a fault point when a power outage occurs in a power distribution system to which distributed power generation sites are connected.

A conventional method for detecting fault points in power distribution systems is timed sequential transmission. When an accident occurs on a distribution line, this system temporarily shuts off the distribution line by shutting off the sending circuit breaker at the distribution substation. Then, open all automatic switches on the distribution lines. Next, the sending circuit breakers at the distribution substations are turned on, and then the automatic switches that separate the distribution lines in order of distance from the distribution substations are turned on.

When the fault section is energized as a result of turning on the automatic switch, fault current flows through the distribution line. This fault current is detected at the distribution substation and the sending circuit breaker is shut off. Then, open the automatic switch on the distribution line. At this time, the automatic switch just before the accident section is locked open to prevent it from being turned on again.

Next, the distribution line circuit breakers are turned on again, and then the automatic switches are turned on in order of distance from the distribution substation. The automatic switch in front of the accident zone is locked open, so it will not close. Through the above procedure, the accident section is detected and power restoration from the distribution substation to the section before the accident section is completed.

In the timed sequential transmission described above, it is possible to detect that there is no fault point between the distribution substation and the most recent fault section, but it is not possible to detect a fault point in the section beyond the fault section (healthy power outage section). , it was not possible to restore power to the normal outage section because it was blocked by the accident section.

As a distributed power distribution system for improving this, there is a system described in Patent Document 1, for example. In this system, power is restored to the normal outage area by reverse power flowing from the power source at the distributed power generation site to the normal outage area.

Japanese Patent Application Publication No. 2009-148098

In the distributed power distribution system described in Patent Document 1, it is shown that a distribution system fault is detected and accident recovery is performed taking into account the reserve power of the distributed power sources. Cooperative operation with the islanding prevention device is not considered.

Furthermore, no consideration is given to suppressing potential changes at the distribution line neutral point and overvoltage generation when ground faults occur multiple times during reverse power flow from distributed power sources.

Therefore, the present invention provides a distributed power distribution system and a method for controlling the distributed power distribution system that cooperates with an islanding prevention device and can suppress overvoltage when a ground fault occurs multiple times during reverse power flow from a distributed power source. The purpose is to

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

In a distributed power distribution system, a distribution system that supplies power to a power demand unit via an automatic switch, a power supply, an islanding prevention device, and an output signal of the islanding prevention device connected to the high voltage distribution line. a disconnection circuit breaker that opens and closes based on the voltage, a suppression switch for the islanding prevention device, a second grounding instrument transformer, and a high-resistance grounding switch; a distributed power source site that is connected via a distribution line and supplies power to loads, and in the event of a ground fault, when reverse power is caused to flow from the power source of the distributed power source site to the distribution system as a starting point, temporarily The second grounded potential transformer is used to ground the neutral point of the distributed power site via the high resistance ground switch.

Further, a distributed power supply system comprising a power distribution system that supplies power to the power demand section via an automatic switch, and a distributed power supply site that is connected to the power distribution system by a high-voltage distribution line and supplies power to the load. In the control method, in the event of a ground fault, when reverse power flow is caused from the power source at the distributed power source site to the distribution system, a second ground voltage instrument transformer is temporarily used as a neutral point of the distributed power source site. is grounded via a high resistance grounding switch.

According to the present invention, there is provided a distributed power distribution system and a method for controlling the distributed power distribution system that cooperates with an islanding prevention device and can suppress overvoltage when a ground fault occurs multiple times during reverse power flow from a distributed power source. can do.

1 is a schematic configuration diagram of a distributed power distribution system according to a first embodiment; FIG. 1 is a high-voltage distribution line voltage waveform of Example 1. It is a high-voltage distribution line voltage waveform of an example different from the present invention. FIG. 2 is a schematic configuration diagram of main parts of a distributed power distribution system according to a second embodiment. FIG. 3 is a schematic configuration diagram of a distributed power distribution system according to a third embodiment. FIG. 3 is a schematic configuration diagram of a distributed power distribution system according to a fourth embodiment.

Preferred embodiments for carrying out the present invention will be described below with reference to the drawings. Note that the following description is merely an example, and the content of the invention is not limited to the specific embodiments below. It goes without saying that the present invention can be modified into various embodiments including the following embodiments.

(Example 1)
Example 1 will be described using FIGS. 1, 2A, and 2B.

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

In FIG. 1, a distributed power distribution system 100 includes a power distribution system 200, a distributed power source site 21, and a high voltage distribution line 5. The power distribution system 200 includes a power distribution substation 1 and automatic switches 9a to 9h.

High voltage distribution line 5 connects distribution substation 1, high voltage consumers 10a, 10b, and 10c, and distributed power source site 21.

In normal times, the high voltage consumer 10a is supplied with power via the automatic switches 9a to 9g, and the high voltage consumer 10b is supplied with power via the automatic switches 9a to 9e and 9h. Further, in normal times, the high voltage consumer 10c is supplied with electric power via the automatic switches 9a, 9b, and 9c.

The distribution substation 1 includes, as power sending equipment, a first ground voltage instrument transformer 3a, a sending circuit breaker 8a, a first zero-phase current transformer 4, and a power source 7a.

Further, the power distribution system includes automatic switches 9a to 9h.

The distributed power source site 21 includes, as power receiving equipment, a second zero-phase current transformer 2a arranged on the high-voltage distribution line 5 within the distributed power source site 21, a capacitor type ground fault detection device 11, and a disconnecting circuit breaker 8b. Equipped with. Further, the distributed power source site 21 includes an islanding prevention device 18, a power source 7b, a switching protection device 14, a load 22, and a power reception control device 15, and supplies power to the load 22.

When the power supply 7b and the power distribution system 200 are operating in parallel, the islanding prevention device 18 detects a power outage on the power distribution system 200 side and shuts off the parallel disconnection circuit breaker 8b. A third zero-phase current transformer 2b is provided on the connection conductor from the power source 7b to the premises busbar, and when a fault current flows due to a failure of the load 22, the third zero-phase current transformer 2b detects it. Then, according to the detection signal from the third zero-phase current transformer 2b, the switching protection device 14 interrupts the protective circuit breaker 8c to protect the power source 7b.

The power reception control device 15 interrupts the disconnection circuit breaker 8b based on the output from a zero-phase current sensor (not shown).

In the first embodiment, a suppressing switch 17a of the islanding prevention device 18 is provided on a control line connecting the islanding prevention device 18 and the parallel disconnection circuit breaker 8b. In addition, a second grounding instrument transformer 3b and a high resistance grounding switch 17b are provided to ground the neutral point of the on-premise power distribution system with high resistance only when a reverse power flow starts from the distributed power source site 21.

In this distributed power distribution system 100, when the distribution substation 1, the high voltage consumers 10a, 10b, 10c, and the distributed power source site 21 are operating in parallel, if a single line ground fault 30a occurs, the distribution substation 1 The first zero-phase current transformer 4 detects the fault current and interrupts the sending circuit breaker 8a. The automatic switches 9a to 9h open when detecting a power outage.

Moreover, the islanding prevention device 18 of the distributed power supply site 21 detects islanding and shuts off the parallel disconnection circuit breaker 8b. Within the distributed power source site 21, autonomous operation continues.

At the time of power restoration, the sending circuit breaker 8a in the distribution substation 1 is turned on, and the automatic switches 9a to 9h are turned on in order of proximity to the distribution substation 1.

When the automatic switch 9b is turned on after a certain period of time after the automatic switch 9a is turned on, a fault current flows to the single line ground fault fault 30a. The fault current is detected at the distribution substation 1, and the sending circuit breaker 8a is shut off. The automatic switches 9a and 9b are opened, but the automatic switch 9b is locked open because the time when there is no voltage after turning on is short.

After a certain period of time, the sending circuit breaker 8a in the distribution substation 1 is turned on, and then the automatic switch 9a is turned on to complete the power restoration. Since the automatic switch 9b is locked open, it is not turned on.

Although there is a single-line ground fault 30a between automatic switches 9b and 9c, whether there is an accident beyond automatic switch 9c (9c to 9h) is determined from the distribution substation 1. It cannot be detected by timed sequential transmission.

In Embodiment 1 of the present invention, when a reverse power flow is generated, the output of the islanding prevention device 18 is suppressed by the suppression switch 17a in the distributed power supply site 21, which suppresses the islanding prevention device. Furthermore, by turning on the high resistance grounding switch 17b, the neutral point of the on-site power distribution system of the distributed power supply site 21 is grounded with high resistance by the second grounding instrument transformer 3b.

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

Specifically, when the automatic switches 9d and 9c are sequentially turned on, a fault current flows, so the line-breaking circuit breaker 8b is cut off. The automatic switch 9c is locked open, and the power is not turned on at the next power restoration, but the power is restored to just before the automatic switch 9c. Next, when the automatic switches 9e and 9f are turned on, a fault current flows, so the disconnection circuit breaker 8b of the distributed power supply site 21 is shut off.

Similarly, the automatic switch 9f is locked open. The automatic switch 9d is also opened once. Next, when the disconnection circuit breaker 8b of the distributed power source site 21 is turned on again, and the automatic switches 9d, 9e, and 9h are turned on in sequence, the high-voltage consumers 10c and 10b are restored by the reverse power flow from the distributed power source site 21. Powered up.

Through the above procedure, the presence or absence of an accident in a normal power outage section is detected. If the power capacity of the distributed power source site 21 is insufficient, power restoration may be stopped and power restored only to a range commensurate with the power capacity of the distributed power source site 21.

2A and 2B show the system voltage when a line-to-ground fault occurs during time-sequential transmission in the reverse direction starting from the distributed power source site 21 in FIG. 1. FIG.

FIG. 2A is an example according to the first embodiment of the present invention, and shows the system voltage when the neutral point of the on-site power distribution system is grounded with high resistance by the second ground voltage instrument transformer 3b in the distributed power supply site 21. , FIG. 2B is an example different from the present invention, and shows the system voltage in the case where the neutral point of the on-premise power distribution system is not grounded to high resistance by the second ground voltage instrument transformer 3b within the distributed power supply site 21.

In FIG. 2A, when the single-line ground fault converges, the neutral point potential of the system attenuates and approaches zero. After that, even if a single line ground fault occurs around 0.55 seconds, no overvoltage occurs.

On the other hand, in FIG. 2B, after the one-line ground fault is resolved, the neutral point potential of the system is not attenuated and a DC component remains. In this state, if a single line ground fault occurs in the vicinity of 0.55 seconds, the amplitude of the transient potential oscillation increases by the shifted neutral point voltage, resulting in a large overvoltage.

Only during timed forwarding in the reverse direction starting from the distributed power source site 21, within the distributed power source site 21, the neutral point of the on-site power distribution system is connected to the second ground voltage instrument transformer 3b by the high resistance grounding switch 17b. By providing high resistance grounding, this overvoltage can be avoided.

In conditions other than time-sequential transmission in the reverse direction starting from the distributed power source site 21, the ground fault current detection sensitivity at the distribution substation 1 decreases, so the neutral point of the distribution system within the distributed power source site 21 is High resistance grounding using the second grounding instrument transformer 3b is not performed.

According to Embodiment 1 of the present invention, when a ground fault occurs in the distributed power distribution system 100, power flows backward from the distributed power source site 21 to the normal power outage section, so that timed sequential transmission starting from the distributed power source site 21 is performed. (backward timed forwarding) detects the presence or absence of a fault section in a healthy power outage section, and the high resistance second grounded instrument transformer 3b placed at the neutral point detects the reverse timed forwarding process. This makes it possible to prevent overvoltage in the power distribution line when multiple ground faults occur, and it becomes possible to safely implement reverse timed transmission.

Therefore, we provide a distributed power distribution system 100 and a method for controlling the distributed power distribution system that can cooperate with the islanding prevention device 18 and suppress overvoltage when a ground fault occurs multiple times during reverse power flow from the distributed power source site 21. can do.

(Example 2)
Next, Example 2 of the present invention will be described.

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

The configuration of the distributed power distribution system 100 other than the distributed power source site 21 is the same as that of the first embodiment shown in FIG. 1, so illustration and detailed description will be omitted.

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

Further, a third ground voltage instrument transformer 3c is connected to a connection point (neutral point) between the other end of the protection transformer 23 and the protection circuit breaker 8c.

In the second embodiment, the neutral point of the connection line from the protection transformer 23 to the power supply 7b is always configured to be grounded with high resistance by the third grounding instrument transformer 3c, and earth fault protection is possible. be. Further, reverse time-sequential transmission starting from the distributed power source site 21 is possible, and in that case, the same effect as in the first embodiment can be obtained by turning on the high resistance grounding switch 17b.

According to the second embodiment, in addition to being able to obtain the same effects as the first embodiment, it is also possible to improve the ground fault protection performance of the distributed power source site 21.

(Example 3)
Next, Example 3 of the present invention will be described.

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

In FIG. 4, in the third embodiment, the suppression switch 17a as the islanding prevention device suppression switch in the distributed power source site 21, the high resistance grounding switch 17b, and the disconnection circuit breaker 8b are installed in the power distribution automation system of the central power dispatch center. It is operated by commands from the system (power distribution automation section) 24. The power distribution automation system 24 of the central power dispatch center controls the opening/closing operations of the suppression switch 17a, the high resistance grounding switch 17b, and the disconnection circuit breaker 8b based on the output signal from the islanding prevention device 18.

Furthermore, the power distribution automation system 24 controls the opening and closing operations of the sending circuit breaker 8a and automatic switches 9a and 9b.

According to the third embodiment, in addition to being able to obtain the same effects as in the first embodiment, it is also possible to perform cooperative control with the power distribution automation system 24 of the central power dispatch center, thereby further improving reliability and safety. Can be done.

(Example 4)
Next, Example 4 of the present invention will be described.

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

Example 4 will be explained using FIG. 5.

In the first embodiment, the power reception control device 15 was configured to shut off the protective circuit breaker 8c based on the output from the zero-phase current sensor (not shown), but in the fourth embodiment The second zero-phase current transformer 2a and the capacitor type ground fault detection device 11 are shared by the power reception control device 15 and the islanding prevention device 18 in the power receiving control device.

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

Thereby, the above-mentioned zero-phase current sensor can be omitted.

According to the fourth embodiment, in addition to being able to obtain the same effects as the first embodiment, the zero-phase current sensor described above can be omitted, and the number of parts can be reduced.

Note that the fourth embodiment can also be applied to the second and third embodiments described above.

DESCRIPTION OF SYMBOLS 1... Distribution substation, 2a... 2nd zero-phase current transformer, 2b... 3rd zero-phase current transformer, 4... 1st zero-phase current transformer, 3a... th 1 Grounding plane instrument transformer, 3b... Second grounding plane instrument transformer, 3c... Third grounding plane instrument transformer, 5... High voltage distribution line, 7a, 7b... Power supply, 8a... Sending circuit breaker, 8b... Line breaking circuit breaker, 8c... Protective circuit breaker, 9a to 9h... Automatic switch, 10a, 10b, 10c... High voltage consumer (electric power demand section), 11... Capacitor type ground fault detection device, 14... Switching protection device, 15... Power receiving control device, 17a... Suppression switch, 17b... High resistance grounding switch, 18... ... Islanding prevention device, 21 ... Distributed power supply site, 22 ... Load, 23 ... Protective transformer, 24 ... Power distribution automation system (power distribution automation department), 30a, 30b ... Line Ground fault accident, 100... Distributed power distribution system, 200... Power distribution system

Claims (6)

A power distribution system that supplies power to the power demand section via an automatic switch;
a power supply, an islanding prevention device, a parallel disconnection circuit breaker connected to a high-voltage distribution line and opened and closed based on an output signal of the islanding prevention device, a suppressing switch for the islanding prevention device, and a second a distributed power source site that has a grounded instrument transformer and a high resistance ground switch, is connected to the power distribution system via the high voltage distribution line, and supplies power to a load;
Equipped with
In the event of a ground fault, when reverse power flows from the power source of the distributed power source site to the distribution system, the second ground voltage instrument transformer is temporarily used to temporarily connect the neutral point of the distributed power source site to the power distribution system. is grounded through the high resistance grounding switch. The distributed power distribution system according to claim 1,
The distributed power source site includes a protection transformer, a third zero-phase current transformer, a third ground voltage instrument transformer, a protection circuit breaker, and a switching protection device,
The power source is connected to the neutral point and the load of the distributed power source site via the protective circuit breaker, the third zero-phase current transformer, and the protective transformer, and the third zero-phase current transformer 1. A distributed power supply distribution system, wherein the switching protection device interrupts the protective circuit breaker when the circuit breaker detects a fault current. The distributed power distribution system according to claim 1,
A distributed power supply distribution system characterized in that opening and closing operations of the parallel disconnection circuit breaker, the suppression switch, and the high resistance grounding switch of the distributed power supply site are controlled based on an output signal from the islanding prevention device. . The distributed power distribution system according to claim 1,
The distributed power source site includes a second zero-phase current transformer disposed on the high voltage distribution line in the distributed power source site, a capacitor type ground fault detector, and a power reception control device,
The islanding prevention device and the power reception control device are supplied with the output signal of the second zero-phase current transformer and the output signal of the capacitor-type ground fault detector, and the output signal of the second zero-phase current transformer or A distributed power distribution system characterized in that the parallel disconnection circuit breaker is opened and closed according to the output signal of the capacitor type ground fault detector. A method for controlling a distributed power supply system comprising a power distribution system that supplies power to a power demand unit via an automatic switch, and a distributed power supply site that is connected to the power distribution system through a high-voltage distribution line and supplies power to a load. In,
In the event of a ground fault, when reverse power flows from the power source at the distributed power source site to the distribution system, the neutral point of the distributed power source site is temporarily connected to the neutral point of the distributed power source site using a second ground voltage instrument transformer. A method for controlling a distributed power distribution system characterized by grounding through a high resistance grounding switch. The method for controlling a distributed power distribution system according to claim 5,
The power source is connected to the neutral point and the load of the distributed power source site via a protective circuit breaker, a third zero-phase current transformer, and a protective transformer, and the third zero-phase current transformer 1. A method for controlling a distributed power distribution system, comprising: cutting off the protective circuit breaker when the protection circuit breaker detects a fault current.

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