JP2005094984A - Protective system for distribution system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable appropriate and high-speed protection by eliminating alliance between relays at short circuiting in a distribution system. <P>SOLUTION: The relay R<SB>2</SB>disposed at a receiving portion of a site, including a dispersion type power supply decides on a short zone based on current i<SB>2</SB>flowing to a Feeder A, current i<SB>A</SB>at a feeder transfer edge, an actual point, direction and absolute value of current i<SB>4</SB>flowing from the other sites to the feeder. A receiving point breaker is released, when the short zone is inside the feeder or the site including the distributed type power supply. The relay R<SB>A</SB>disposed at a substation secondary side bus line decides the short zone based on current i<SB>B</SB>flowing in and out of the bus line, the actual point, direction, and absolute value of the current i<SB>A</SB>flowing to the feeder to release the receiving point breaker, when the short zone is at the feeder or the substation secondary side bus line. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a protection system for a distribution system laid radially, and more particularly to short-circuit protection for a distribution system in which a distributed power source is introduced.

  Due to various reasons such as deregulation in the electric power industry, performance improvement and price reduction of small generators, the introduction of distributed power sources such as solar power generation, fuel cells and micro gas turbines is expected to expand. A conventional large-scale power supply is installed in a remote place away from the consumer, whereas a distributed power supply is small-scale and installed near the consumer. For this reason, in the conventional distribution system, no power source is connected to the lower level of the distribution substation, whereas in the distribution system in which the distributed power source is introduced, the distributed power source is also connected to the lower level of the distribution substation. Will be lined up.

In the current protection system, on the assumption that the introduction of the distributed power supply is small, each relay in the power distribution system basically determines the operation using information on only the installation point. Since each relay cannot clearly determine whether it is a failure point to operate, it is necessary to sufficiently cooperate between relays in the distribution system in order not to disconnect the distributed power source unnecessarily. In future power distribution systems where a large number of distributed power sources are expected to be introduced, it is necessary to coordinate between relays considering a number of distributed power sources, which complicates the planning and operation of the distribution system Is expected. Therefore, it is necessary to introduce a new protection system that can flexibly cope with a large-scale introduction of a distributed power source, and examination and guidelines for this kind of protection system are also shown (for example, see Non-Patent Document 1 and Non-Patent Document 2). ).
Inoue, Shimano, Ito, Totsu, Nakayama: “Discussion of distributed protection relay system using Ethernet”, IEEJ Transactions B, Vol.120, No.8 / 9, pp.1161-1168 Agency for Natural Resources and Energy: “Guidelines for Power System Interconnection Technical Requirements '98”, Electric Power Shinposha, 1998

  The current protection system has the following problems.

  (1) Cooperation between relays in the distribution system is necessary, and it is difficult to cope with future large-scale introduction of distributed power sources.

  (2) It is difficult to flexibly cope with the reconfiguration of the protection system due to the introduction and abolition of distributed power sources and the looping of the distribution system.

  The present invention proposes a protection system that can overcome the above-mentioned problems by using communication technology such as Ethernet (registered trademark) and each relay utilizing information on a plurality of other relay installation points. .

  Non-Patent Document 1 proposes a concept of utilizing an information network for a protection system. However, although it has been studied whether the communication speed of the current technology can be applied to the relay, what information is actually used for the relay and the relay is operated when the information is in what condition It is not considered whether this is the case.

Here, first, the sequence of the current protection system shown in the guideline (Non-Patent Document 2) is organized using the model system of FIG. The model system in the figure branches from the secondary bus (Area-1) of the distribution substation to the feeders (Area-A, Area-B), and the sites (Area-2, 4, 4) branched from these feeders. 5 and 7), a distributed power source is introduced. In this system configuration, paying attention to the operation judgment of the relay R _{2 at} the receiving point of the site where the distributed power source DG2 is introduced and the relay R _{A at} the feeder of the interconnection feeder, focusing on the role of timed coordination in the current protection system Organize and explain the problems of the current protection system at the time of large-scale introduction of distributed power supply.

(1) Role of inter-relay cooperation FIGS. 28 to 30 show an operation sequence of each relay in the current protection system. Overcurrent relays are used in the relays R _A and R _B at the feeder sending end corresponding to the short-circuit failure, and short-circuit direction relays are used in the relays R _{2 to} R ₇ at the receiving points of the distributed power source.

In the figure, the operating current values of R ₂ , R ₄ , R _A and R _B are I _2s , I _4s , I _Ls and I _Ls , and the operating time periods are TDG, TDG, TL and TL. The relay R _{2 at} the power receiving point of the distributed power source DG2 is required to operate when a failure occurs in Area-1, Area-2, and Area-A, and does not operate when a failure occurs in other sections. However, the magnitude and phase current ^ i ₂ flowing through R ₂ in the event of a fault in the Area-A is substantially the same as the time of failure in the Area-4 and Area-B, R ₂ is to determine these fault point I can't. So from FIGS. 28 and 29, for which R ₂ determines the Area-A and Area-B, the R _B of the feeder feed edge taking timed coordination to work earlier than R _2. When the fault on another feeder (Area-B) occurs, R _B operates earlier, for disconnection and failure point and DG2, R ₂ does not operate, # 2 unnecessary Kairetsu Not.

On the other hand, if the dispersed type power supply is small capacity, since the fault current flowing from DG2 when a failure in Area-4 occurs is small, the current flowing in R ₂ is less than if a fault occurs in Area-2. Therefore, R ₂ uses an inverse time characteristic, so that it operates quickly against a fault in its own bus (Area-2) where the fault current is large, and an unnecessary solution of the other distributed power source DG4 in the same feeder. The row is prevented, and the operation is slowed down for a failure in Area-4 where the failure current is small, thereby preventing unnecessary separation of DG2.

Relay R _A feeder transmission terminal operates on the failure in the feeder (Area-A), it is required to do work in respect faults in other feeders. In the case of a failure occurring in Area-B, the current ^ i _A flowing in R _A is supplied from the distributed power sources (DG2 and DG4) in the feeder. If the distributed power source in the feeder has a small capacity, this current is considered to be small compared to the current that flows at the time of failure in Area-A. Only _RA can be operated.

Further, from FIG. 30, in this manner to set the operating current value of R _A, R _A against faults in distribution substation bus (Area-1) is will not work, the distributed power receiving point Relays R ₂ and R ₄ operate, and the distributed power source is reliably disconnected from the point of failure. In addition, in the case of a failure in the buses (Area-2 and Area-4) in the feeder, a very large current flows through the relays (R ₂ and R ₄ ) at the power receiving points of these buses. By setting these relays to operate instantaneously, _RA does not operate.

(2) Problems when large-scale distributed power supply is introduced In the above example, only two distributed power supplies are installed in each feeder. Easy. However, when a very large number of distributed power sources are introduced, a large number of relays must be considered and coordinated. In the future, when the distribution system is looped, it is expected that the protection of the distribution system will become more complicated. This can make it difficult to coordinate.

In addition, it is expected that it will take time to cooperate, and it may take time for the procedure of the distributed power interconnection. In addition, when the introduction of the distributed power source is a small capacity, since the fault current flowing through R _A at the time of failure at Area-B is smaller than the current flowing at the time of failure at Area-A, R _A is replaced with Area-A. It was possible to determine the operating current value so that it would operate only when there was a failure. However, when a distributed power source is introduced on a large scale, the difference between these currents becomes small. Therefore, it is difficult to determine the operating current value of _RA unless additional equipment such as a current limiting reactor is introduced. become.

  In view of the above, an object of the present invention is to provide a distribution system protection system capable of accurate and high-speed protection without the need for coordination between relays in the event of a short circuit failure in a distribution system in which a distributed power source is introduced on a large scale. There is.

  In order to solve the above-mentioned problems, the present invention uses the information of the real part, direction, and absolute value of the current detected at the peripheral feeders and the site to protect the distribution system with the distributed power supply. Judgment is made as to whether or not the circuit breaker needs to be disconnected, and it has the following configuration.

(1) In a power distribution system in which a distributed power source is introduced at a site branched from a feeder,
It is installed at the power receiving point of the site including the distributed power source, and obtains the current flowing from the site to the feeder, the current at the feeder sending end, and the current flowing from the site including other distributed power sources connected to the feeder to the feeder as information. The site including the distributed power source is determined when the short-circuit fault interval is determined using the real part, direction, and absolute value of these currents, and the short-circuit fault interval is inside the site including the feeder or the distributed power source. A distribution system protection system comprising a short-circuit protection sequence for releasing a power receiving point circuit breaker.

(2) In a power distribution system in which a distributed power source is introduced at a site branched from a feeder,
Information obtained from the current flowing into and out of the substation secondary bus and from the site including the distributed power source connected to the feeder to the feeder is obtained as information, and the real part of these currents , Direction, absolute value is used to determine the short-circuit fault section, and when the short-circuit fault section is the feeder or substation secondary bus, the short-circuit protection that releases the receiving point breaker of the site including the distributed power source A distribution system protection system characterized by a sequence.

  As described above, according to the protection system of the present invention, the information on the real part, the direction, and the absolute value of the current detected by each relay is used for the receiving point of the distributed power source and the relay at the feeder transmission end. Even without considering cooperation between relays, it is possible to accurately issue an operation command only to the breaker at the relay installation point linked to the failure section.

  In the protection system of the present invention, it is possible to cope with changes in the capacity of the distributed power supply without changing the set values of the respective relays, and the fault section can be disconnected faster than the conventional protection system.

  In addition, the protection system of the present invention utilizing the information network can flexibly cope with the increase or decrease of the distributed power supply capacity in the distribution system, and further eliminates the need for cooperation between relays as in the conventional protection system. Therefore, it is possible to simplify the procedure of the distributed power interconnection.

  The conventional protection system is based on the premise that the introduction of the distributed power source has a small capacity. Therefore, when a distributed power source is introduced on a large scale, it is necessary to add equipment such as a current limiting reactor. However, in the protection system of the present invention, since each relay can accurately determine the operation, a distributed power source can be introduced on a large scale within the scope of the short-circuit capacity constraint without adding equipment.

  Furthermore, since the start / stop of the distributed power supply is performed at the convenience of the customer, the configuration of the power distribution system frequently changes due to the start / stop, especially the magnitude of the fault current supplied from the distributed power supply changes. It is expected that. Therefore, in the conventional protection system, there is a possibility that the operation determination of the power receiving point relay of the distributed power source may be adversely affected. However, in the protection system of the present invention, only the information on the direction of the current is used for the relay operation among the power receiving point information of the distributed power source. For this reason, the protection system of the present invention can cope with the start / stop of such a distributed power source.

Further, in the case of an area-1 failure in the system model, if the load is interrupted to some extent, the power supply in the feeder can be continued by the distributed power source. However, in the conventional protection system, the fractional power source is disconnected from the failure point by operating the breakers at the installation points R _{2 to} R ₇ instead of R _A and R _B for the failure of Area-1. Therefore, it is impossible to continue power supply to customers who have not introduced a distributed power source. On the other hand, in the protection system of the present invention, by operating the breaker R _A and R _B installation points for failure of Area-1, which paralleled a distributed power from the fault point. Therefore, when the distributed power source has a surplus capacity, power supply to more buses can be continued.

(Embodiment)
In the present invention, each relay uses the information of a plurality of other relay installation points using communication technology such as Ethernet. We propose a protection system that can respond to the introduction, and can flexibly cope with the reconfiguration of the protection system that accompanies the introduction and abolition of distributed power sources and the looping of the distribution system.

  In order to eliminate the need for cooperation between relays, it is necessary to be able to clearly determine whether each relay is a failure point to operate. As one of the methods, we propose to use the information network to capture the information of other relay installation points into the relay.

Hereinafter, information necessary for determining the operation of each relay and its operation sequence will be described with reference to the model system of FIG. FIG. 1 shows the relays R _DG2 , R _DG4 , R _DG5 , and R _DG7 connected to only the low-voltage distribution system and the distributed power source in FIG. 27 (1) Classification of failure sections for information selection In order to select information necessary for operation determination, in the model system described above, a fault section that needs to be disconnected is classified for the relay R ₂ at the power receiving point of DG2 connected to # 2.

  First, when a failure occurs in the distributed power supply introduction bus (Area-2) and the feeder (Area-A) connected to DG2, it is necessary to disconnect DG2 in order to eliminate the failure. On the other hand, even if the DG2 is connected to the feeder, in the case of a failure in another bus (Area-4), it is not necessary to disconnect the DG2 if the corresponding bus can be quickly disconnected. Similarly, for a fault in the low-voltage distribution line (Area-8), it is not necessary to disconnect DG2 if the fuse of the pole transformer is quickly cut off. For failures in feeders (Area-B, Area-5, Area-7, and Area-9) that do not disconnect DG2, it is not necessary to disconnect DG2 if the entire feeder can be quickly disconnected. . Finally, for a fault in the distribution substation (Area-1), it is not necessary to disconnect DG2 if the entire feeder connected to DG2 can be disconnected.

  Therefore, in the case of the model system of FIG. 1, it is considered that it is not necessary to disconnect DG2 in the case of a failure in Area-2 and Area-A, and in the case of a failure in other sections, it is not necessary to disconnect DG2. It is done. Below, the information required in order to determine the disconnection of DG2 is examined about the case where a three-phase short circuit failure occurs.

(2) Failure section where the distributed power source is disconnected (2.1) Area-A
FIG. 2 shows the operation of each relay when a short-circuit failure occurs in Area-A. From the investigation in (1) above, when a failure occurs in Area-1 and Area-B, the phase and magnitude of the current detected by R ₂ is the same as when a failure occurs in Area-A. For this reason, the information for discriminating between the failure in Area-A and the failure in these sections is necessary. In the case of a failure at Area-A, the current direction i i _A detected by R _A is the direction that flows into Area-A. On the other hand, when a short circuit occurs in Area-1 and Area-B, the direction of the current flows in the opposite direction of Area-1. Therefore, as the direction information of the current detected by the R _A, the use of positive and negative information of the real part of the current vector ^ i _A relative to the voltage detected by the R _A Re {^ i _A} to R ₂ With these, it is possible to determine these failure sections.

Further, even when a failure occurs in Area-4 do not need to disconnection of DG2, phase and magnitude of the current flowing in R ₂ is the same extent as if a failure occurs in Area-A. Therefore, information for distinguishing failures between Area-A and Area-4 is necessary. When a short circuit occurs in Area-A, the direction of the current i ₄ detected by R ₄ is the direction that flows into Area-A, but when a short circuit occurs in Area-4, it flows into the reverse Area-4. Direction. Therefore, the failure of Area-A and Area-4 can be discriminated by using the positive and negative information of Re {^ i ₄ } as R2 as information on the direction of the current detected by R ₄ .

Furthermore, in consideration of the reverse flow of the distributed power source, a condition for discriminating between a healthy time and a failure time is necessary for a failure in Area-A. In order to make this determination, it is conceivable to use the current magnitude | ^ i ₂ | at R ₂ . However, when the distributed power source DG2 is a current source, it is considered that | ^ i ₂ | does not increase at the time of failure. Further, even if the distributed power source DG2 is a voltage source, it is conceivable that | ^ i ₂ | at the time of failure may vary greatly depending on activation / deactivation of DG4. From this, it is considered that | ^ i ₂ | is difficult to use for determining whether the state is healthy or failure. Therefore, the current magnitude | ^ i _A | at R _A is used to determine whether the failure at Area-A is healthy or at failure.

Depending on the supply-demand balance, even if a permanent accident occurs in Area-A, there is a possibility that the power supply can be continued uninterrupted to the # 2 load by the distributed power supply # 2. This means that if a fault in Area-A occurs, since it is Kairetsu the distributed power supply and failure point # 2 by the operation of R _2, is considered to be achieved by not operating the R _DG2. At that time, in the failure of Area-A and Area-2, the phase and magnitude of the current flowing through the installation point of R _DG2 are approximately the same, so the failure of Area-A and Area-2 is as shown below. By adding a condition for distinguishing _RDG2 to _RDG2 , the operation of _RDG2 is made more reliable. When a short circuit occurs in Area-A, the direction of the current i ₂ detected by R ₂ is the direction that flows into Area-A. On the other hand, in the case of a failure in Area-2, the direction of the current flows in the opposite direction of Area-2. Therefore, by using the positive / negative information of Re {^ i ₂ } as the information on the direction of the current detected by R ₂ , it is possible to prevent R _DG2 from operating when there is a failure in Area-A. .

(2.2) Area-2
The operation of each relay when a short circuit failure occurs in Area-2 is shown in FIG. When a failure occurs in Area-2, R ₂ and R _DG2 can determine that a failure has occurred in their own bus by mutual information exchange, and disconnect Area-2 and DG2 from the distribution system. In the relay R _DG4 other DG (DG4) in the same feeder, it can detect that the fault in the other bus in the same feeder by Re {^ i _2} occurs, to prevent unwanted disconnection of the distributed power sources Can do.

However, if a failure occurs on the distributed power source side of R _DG2 , R ₂ must not issue a disconnection command in order to continue power supply from the distribution system to the # 2 load. In both cases, the currents flowing through the installation point of R ₂ are considered to be substantially the same phase and the same magnitude. Therefore, it is necessary to take the information to determine the both the R _2.

When a failure occurs in Area-2, the current ^ i _DG2 detected by R _DG2 flows into Area-2, but when a failure occurs on the distributed power source side of R _DG2 , ^ i _DG2 The direction of is considered to be the opposite. Therefore, by using the positive and negative information of Re {^ i _DG2 } as R ₂ as the information of the direction of the current ^ i _DG2 detected by R _DG2 , the failure between Area-2 and the distributed power source side of R _DG2 can be _avoided. Can be determined.

Further, when the load of # 2 is large, it is expected that the direction of the current detected by R ₂ and R _DG2 is the same as that at the time of failure in Area-2 even when the load is healthy. Therefore, it is considered that a condition for discriminating between a healthy time and a failure time is necessary. Since the electrical distance from the failure current supply source to the failure point of Area-2 is reduced by the introduction of the distributed power source, the magnitude of current detected by R ₂ at the time of failure | ^ i ₂ | It is thought that it will increase sufficiently regardless of the position of introduction. Therefore, if the magnitude of | ^ i ₂ | is added to the determination condition, it is possible to determine whether the state is healthy or failure.

(3) Failure section in which distributed power source is not disconnected (3.1) Area-1
FIG. 4 shows the operation of each relay when a short circuit failure occurs in Area-1. The sum of current vectors flowing into Area-1 in the healthy state (^ i _s- ^ i _A- ^ i _B ) = ^ 0. Therefore, when (^ i _s − ^ i _A − ^ i _B ) = ^ 0, it is considered that the failure point of Area-1 can be removed by operating Rs, R _A and R _B. This failure removal sequence in Area-1 can be used in the distribution system of any configuration regardless of the presence or absence of the distributed power source.

On the other hand, when considering that the power supply to the load in the single system is continued by the distributed power supply, it is desired not to disconnect the distributed power supply DG2 in the case of a failure in Area-1. In this case, by taking the direction of the information in the R ₂ ^ i _A, it can be set not Resshi solutions of distributed power DG2.

(3.2) Area-4
FIG. 5 shows the operation of each relay when a short-circuit failure occurs in Area-4. Similar to the Area-2, ^ i ₄ and i _DG4 is the direction towards the _{Area-4, | ^ i 4} | is in Area-4 by operating the R ₄ and R _DG4 when a large value Faults can be disconnected from all power sources. DG2 does not need to be disconnected if the determination to the operation of the circuit breaker can be performed quickly. As described above, the direction of i ₄ is different in the failure between Area-A and Area-4. Therefore, it is possible to set not Resshi solution to DG2 by capturing direction information of R ₂ to ^ i _4.

(3.3) Area-8
FIG. 6 shows the operation of each relay and fuse when a short circuit failure occurs in Area-8. When the short-circuit Area-8 occurs, like the current in R ₂ of the failure in the Area-2, is installed in the distributed Area-8 upper pole transformer in regardless of the position of the introduction of power An excessive current flows through the fuse F2-1. Therefore, only the short-circuit section can be disconnected by making the fuse blow earlier than the operation of other relays. Generally, since the circuit breaker has a mechanical mechanism, the operation speed of the fuse is faster than the operation speed of the protective device combining the relay and the circuit breaker. Therefore, such a protection sequence is sufficiently possible.

  As described above, by using a plurality of pieces of information for determining the operation of each relay, it is possible to reliably disconnect only the distributed power sources linked to the failure section without cooperation between the relays.

An example of the basic configuration of a relay for obtaining the above protection operation is shown in FIGS. 7 and 8 in comparison with the conventional system. Figure 7 is a basic configuration diagram of a relay R ₂ for dispersed power receiving point, FIG 8 is a diagram showing the basic configuration of a relay R _A feeder sending end. In both of these figures, in the conventional system, only comparisons based on absolute values of the currents i ₂ and i _{A in} the relays R ₂ and R _A are made, whereas in the present embodiment, currents i ₂ and i ₄ of other relays are used. the i _a captures information, these information and the current i _DG2, i _B, captures the i _S, and from these current information based on operating conditions of FIGS. 2-6 of the operation determination of the relay R _2, R _a Get.

(simulation result)
Simulations were performed to verify the protection system of the present invention. This will be explained below in comparison with the current protection system.

(A) Calculation conditions In the model system shown in FIG. 1, the buses in Feeder-A are connected by a 2 km 6.6 KV distribution line. The loads of # 2 to # 4 are 700 kW and # 5 are 2100 kW, respectively, and the sum of the loads in Feeder-A and B is equal. All power factors are assumed to be 0.9.

  Distributed power supplies are introduced at # 2, # 4 and # 5. Assuming the case where the installed capacity of the distributed power source is increased, the case where the capacity of DG2 and DG4 is 350 kW and 2000 kW was examined. When the capacity of the distributed power source increases, the breaking capacity of the circuit breaker may become a problem, but here, it is calculated as an extreme example showing the flexibility of the protection system of the present invention. The capacity of DG5 is 700 kW. All of these distributed power sources were synchronous generators used in CGS (Cogeneration System). FIG. 9 shows a device constant table of each distributed power source, and FIG. 10 shows a control system. The device constants and control system of each distributed power source were all the same.

  A simulation was performed using a numerical calculation program (Matlab / Simlink) when a three-phase short-circuit failure occurred at points I to VI of this model system.

(B) Impact on the current protection system When a failure occurred at point I and the failure point was not disconnected, the failure current at each relay was calculated. The electric current which flows into the A phase of each relay installation point is shown in FIG. 11 and FIG. From FIG. 5A, when the distributed power source is 350 kW, the fault current flowing through R ₂ is 130A to 200A. On the other hand, when the distributed power source is 2000 kW, the current flowing through R ₂ is about 150 A even when sound. Therefore, in the current protection system, when the distributed power source is increased from 350 kW to 2000 kW, R ₂ operates even when it is healthy, so the set value of R ₂ must be changed.

(C) Operation of each relay in the protection system of the present invention Here, in the protection system of the present invention, when the capacity of the distributed power source is increased, only the failure section is accurately determined without changing the set value of each relay. Indicates that it can be disconnected. Based on the relay sequence (FIGS. 2 to 6) shown in the embodiment, the control blocks of each relay that can determine whether or not to operate for each point in the distribution system are shown in FIGS. FIGS. 13 to 16 are block diagrams of a relay R _{2 at} a distributed power receiving point, and FIGS. 17 to 21 are block diagrams of a relay _RA at one end of feeder feeding. Using this control block, the operation signal of each relay in the proposed protection system when a three-phase short-circuit failure occurred at points I to VI was calculated.

The change of the relay R ₂ and operation signals of the R _B in the case of failure in I and II points occurs shown in FIGS. 22 to 25. In the figure, when the operation signal is 1, it means that the relay operates and sends a break command to the breaker. From the figure, it can be seen that each relay operates properly. In the fault point I and II points, operation signals of R _A and R ₄ have confirmed that the changes in the same manner as the operation signal R _2.

On the other hand, even if the capacity of the distributed power source increases, each relay operates properly. R ₂ , R _4, and R _A use the current magnitude | ^ i _A | at R _A to determine whether Feeder-A is healthy or faulty. In the case of a failure at point II, | ^ i _A | increases as the capacity of the distributed power source increases, but it is determined from the information in the direction of ^ i _A that the failure is outside of Feeder-A. R ₂ does not work because it can. On the other hand, at the time of failure at point I, | ^ i _A | is considered to increase without depending on the capacity of the distributed power source, and R ₂ operates. From this, it is considered that only the distributed power source linked to the failure section can be selectively disconnected.

  In addition, regarding the failures at points III to VI, the operation signals of the respective relays were calculated based on the above sequence, with the relay set values being the same as in the above examination. As a result, it was confirmed that even if the capacity of the distributed power source was increased from 350 kW to 2000 kW, only the relay in the failure section could be selectively operated without changing the set value of the relay.

  13 to 21, it is preferable to provide a time delay as necessary to prevent a transient malfunction in the relay output.

  From the above, it was confirmed that the proposed protection system can cope with a large increase in the capacity of the distributed power source without changing the set value of the relay.

(D) Speeding up of operation determination In the current protection system, each relay operates the circuit breaker according to an operation time period determined by cooperation with other relays. For this reason, it takes about several hundreds of milliseconds for the failure section to be disconnected. Due to the delay of the failure section disconnection, the distributed power supply outside the failure section may continue for a long time after the termination of the descending section. On the other hand, in the protection system of the present invention, by using the information of other points, it is possible to clearly determine whether each relay is a failure point that should operate the circuit breaker in about 20 msec after the failure occurs. Can be shortened.

In order to confirm this, by using the model system of FIG. 1, the magnitude of the fluctuation of the distributed power source outside the fault section when the fault point is disconnected in the normal protection system and the protection system of the present invention is determined. I went to the village. The capacity of DG2 and DG4 was 2000 kW. To generate a three-phase short circuit fault in II point was Kairetsu the fault point by operating the breaker R _B installation point. As a case where the current protection system was disconnected, this circuit breaker was operated 200 msec after the failure occurred. Further, from the above examination, in the protection system of the present invention, the operation determination of the circuit breaker by each relay is possible in about 20 msec after the occurrence of the failure, but considering the communication delay time, the operation delay time of the circuit breaker, etc. It is considered that an additional time of about several tens of milliseconds is required until the actual failure point is cut off. Therefore, a case where the disconnection with protection system of the present invention, it was decided to operate the breaker R _B installation point 50 msec.

  FIG. 26 shows changes in the internal phase angle of the distributed power supply DG4 outside the descending section. From this figure, it can be confirmed that the failure of the distributed power supply outside the failure section can be suppressed because the acceleration of the rotor of the distributed power supply due to the failure can be suppressed by disconnecting the failure section early.

  From the above, it was confirmed that the fluctuation of the distributed power source outside the descending section can be reduced by quickly disconnecting the fault section using the protection system of the present invention.

Simplified system model diagram. Operation of each relay when a short circuit occurs in Area-A (embodiment). Operation of each relay when a short circuit occurs in Area-2 (embodiment). The operation of each relay when a short circuit occurs in Area-1 (embodiment). Operation of each relay when a short circuit occurs in Area-4 (embodiment). The operation of each relay when a short circuit occurs in Area-8 (embodiment). The basic configuration example of the relay R ₂ in conventional manner as the embodiment. The example of basic composition of relay _RA of a conventional system and an embodiment. Equipment constant table of distributed power source used for simulation. The control system block diagram of the distributed power supply used for simulation. Current waveform that flows through each relay when a failure occurs at point I in the simulation. Current waveform that flows through each relay when a failure occurs at point I in the simulation. A control block diagram of the relay R ₂ in the embodiment (at the time of failure in the Area-A). A control block diagram of the relay R ₂ in the embodiment (at the time of failure in the Area-2). A control block diagram of the relay R ₂ in the embodiment (at the time of failure in the Area-4). A control block diagram of the relay R ₂ in the embodiment (at the time of failure in Area-1, Area-B) . The control block diagram of relay _RA in embodiment (at the time of a failure in Area-A). The control block diagram of relay _RA in embodiment (at the time of a failure in Area-1). The control block diagram of relay _RA in embodiment (at the time of a failure in Area-B). The control block diagram of relay _RA in embodiment (at the time of a failure in Area-2). The control block diagram of relay _RA in embodiment (at the time of a failure in Area-4). Operation signal of each relay at the time of failure at point I in the simulation (distributed power supply 350 kW). Operation signal of each relay at the time of failure at point II in the simulation (distributed power supply 350 kW). The operation signal of each relay at the time of a failure at point I in the simulation (distributed power supply 2000 kW). The operation signal of each relay at the time of failure at point II in the simulation (distributed power supply 2000 kW). The operation signal of each relay at the time of failure at point II in the simulation (distributed power supply 2000 kW). The system | strain model figure explaining the classification | category of a failure area. Operation of each relay when a short circuit occurs in Area-A (conventional). Operation of each relay when a short circuit occurs in Area-B (conventional). Operation of each relay when a short circuit occurs in Area-1 (conventional).

Explanation of symbols

R _A , R _B , R ₂ , R ₄ , R ₅ , R ₇ relays DG2, DG4, DG5, DG7 Distributed power supply

Claims (2)

In a power distribution system where a distributed power source is installed at a site branched from a feeder,
It is installed at the power receiving point of the site including the distributed power source, and obtains the current flowing from the site to the feeder, the current at the feeder sending end, and the current flowing from the site including other distributed power sources connected to the feeder to the feeder as information. The site including the distributed power source is determined when the short-circuit fault interval is determined using the real part, direction, and absolute value of these currents, and the short-circuit fault interval is inside the site including the feeder or the distributed power source. A distribution system protection system comprising a short-circuit protection sequence for releasing a power receiving point circuit breaker. In a power distribution system where a distributed power source is installed at a site branched from a feeder,
Information obtained from the current flowing into and out of the substation secondary bus and from the site including the distributed power source connected to the feeder to the feeder is obtained as information, and the real part of these currents , Direction, absolute value is used to determine the short-circuit fault section, and when the short-circuit fault section is the feeder or substation secondary bus, the short-circuit protection that releases the receiving point breaker of the site including the distributed power source A distribution system protection system characterized by a sequence.

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