JP2009189084A - Power distribution system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power distribution system of one-breaker-in-every distribution-line system, that reduces the number of breakers for distribution lines in the insulated distribution lines of isolated systems where most of accidents are ground faults. <P>SOLUTION: A power distribution system, where a substation, which has a bus for power distribution of a transformer and a plurality of power distribution lines, and each power distribution line includes switches for automation of power distribution, is provided with a set of breakers, which handles the supply of power to the bus, between the transformer and the bus, and fuse type load switches, which are opened automatically when a certain current or over flows at the short circuit accident between the close ends of the distribution lines, in the substation separately for each distribution line, and further it is provided with a first distribution line switch, that breaks a small current at a ground fault in the distribution line or upon short circuit at the remote ends, immediately after the lead-out port of the distribution line. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a power distribution system applicable to a non-grounded substation transformer.

  A configuration example of a conventional power distribution system is shown in FIG. In the substation 1, the transformer 3 that transforms the power supplied from the upper system is connected to the power distribution bus 2, and the bus 2 is distributed via a disconnector (not shown) and circuit breakers 10 a, 10 b, and 10 c, respectively. It is connected to the electric wires 1F, 2F, 3F.

  In addition, distribution switches 7a, 7a1, and 7a2 are installed on the distribution line 1F at intervals. Similarly, 7b and 7b1 are installed on the distribution line 2F, and 7c and 7c1 are installed on the distribution line 3F. Moreover, the interconnection switch 7ab is provided between the distribution line 1F and the distribution line 2F.

  As a protection method for this power distribution system, overcurrent protection relay devices 11a, 11b, and 11c that operate on the basis of electrical signals that are generally input through instrument transformers 20a, 20b, and 20c inserted into the respective distribution lines. And the ground fault direction protection relay devices 12a, 12b, and 12c are used to isolate the fault location by tripping the circuit breakers 10a, 10b, and 10c, respectively, and then the circuit breaker 10a is automatically operated by the reclosing devices 14a, 14b, and 14c. , 10b, and 10c are entered and controlled to restore power.

  Specifically, for example, when an accident occurs between the switches 7a1 and 7a2 of the distribution line 1F, the accident is detected by the overcurrent protection relay device 11a in the case of a short circuit and by the ground fault direction protection relay device 12b in the case of a ground fault. The corresponding circuit breaker 10a is controlled to be opened. Then, when a preset time has passed, the reclosing device 14a supplies power to the distribution line 1F in which the opened circuit breaker 10a is turned on and an accident has occurred.

  In this way, the power distribution system has been constructed without distinguishing between the fault point in the distribution line and the transformer installation method in the substation, so in the event of a short-circuit accident at the far end of the distribution line or in a non-grounded system In the case of a ground fault in a distribution line, a high-current circuit breaker was used in the event of a near-end distribution line accident or a bus accident even though the accident current was small.

However, in recent years, the distribution network and distribution automation system have been enhanced, and restoration using the distribution automation system may be faster than restoration from the host system. Moreover, the distribution line is insulated, and the ratio of the ground fault and the short-circuit accident is about 6: 1. Furthermore, when a near-end short-circuit accident occurs, it is a rare case, and even if a trial charge is performed, unsuccessful establishment in the case of a short-circuit is high. For this reason, it is close to excess facilities to equip all the distribution lines with expensive circuit breakers, which is not economical and expensive to maintain. On the other hand, the reliability of protection under critical conditions is required in case of emergency.
Japanese Unexamined Patent Publication No. 6-86451

  The present invention has been made in view of the above-described circumstances, and provides an economical and reliable distribution system by reducing circuit breakers for distribution lines in a non-grounded insulated distribution system. The purpose is to do.

  In order to achieve the above object, a power distribution system according to the present invention is a power distribution system in which a bus for a distribution line of a transformer, a substation having a plurality of distribution lines, and a switch for distribution automation in each distribution line. A substation comprising a circuit breaker between the transformer and the bus, and a fuse-type load switch that is automatically opened when a certain current or more flows for each distribution line, and the outlet of the distribution line Is provided with a distribution line switch (corresponding to the first switch in the embodiment) capable of cutting off a small current.

  In other words, in an ungrounded and insulated distribution line, most of the accidents are ground faults, and the ground fault current at the time of the ground fault is small. Since the short-circuit current is small, in the event of these accidents, it is interrupted by a distribution line switch that has a sufficient breaking capacity to interrupt this small current, and in the event of a short-circuit accident at the closest end of the distribution line, a fuse-type load switching In case of an accident at the busbar or as a protection after the accident, the breaker installed on the busbar is used.

  The power distribution system according to the present invention further includes an instrument transformer (bus transformer) inserted into the bus to protect the bus, an overcurrent protection relay device for the bus via the power transformer, and each distribution line. In order to protect against ground faults and short circuit accidents, equipped with an instrument transformer (distributor for distribution lines), a ground fault direction relay device via this, and an overcurrent protection relay device for distribution lines It is characterized by that.

  In the present invention, when the current at the time of the ground fault of the distribution line and the current at the time of the short-circuit at the far end are small, the opening control of the distribution line switch is controlled by the ground fault direction protection relay device and the over current protection relay device for the distribution line. If the current of the short-circuit accident at the closest end of the distribution line is large, the fuse-type load switch is used to shut off autonomously. In the event of a bus fault, the interrupt is performed using the bus overcurrent protection relay device. By controlling the opening of the switch, it is possible to control the opening of the switch at the optimum position for any accident in the power distribution system.

  To describe more specific characteristics of this protection method, the operating time characteristics of the overcurrent protection relay device for distribution lines are set to the characteristics that can be interrupted by the distribution line switches, and the operating time characteristics of fuse type load switches are changed. The distribution line switch has a characteristic that cuts off the current that cannot be cut off, and the time-limit characteristic of the overcurrent protection relay device for busbars is a characteristic that is slower than the operation time characteristic of the fuse-type load switch.

  In other words, in order to shut off the optimal switch in the case of a short-circuit accident that occurs rarely in an insulated distribution line, if the current at the short-circuit accident at the far end of the distribution line is small, the equipment of each distribution line The distribution line switch is controlled to be cut off by the overcurrent protection relay device for the distribution line, and in the event of a short circuit fault of the current beyond the distribution line, the fuse type load switch is used to shut off the distribution line short circuit accident. Otherwise, the bus breaker is controlled to be opened by the overcurrent protection relay device for the bus as an accident of the bus.

  At this time, the overcurrent protection relay device for busbars operates in a region including the operation region of the overcurrent protection relay device for distribution lines. When operating in the operation region, the overcurrent protection relay device for distribution lines is used. It is preferable to set the operating characteristics so as to operate slower than the electric device. Thereby, the overcurrent protection relay device for busbars can function as a backup of the overcurrent protection relay device for distribution lines.

  Further, the power distribution system according to the present invention further comprises a reclosing device for reclosing the distribution line switch of each distribution line and a reclosing device for reclosing the busbar circuit breaker for recovery from a power failure. Features.

  In the present invention, a distribution line switch that has been controlled to open by a corresponding protective relay device for distribution lines due to a ground fault in a distribution line and a short-circuit accident at a far end is distributed after a predetermined time (for example, after 30 seconds). It is possible to perform the operation of automatically turning on and recovering the switch of the distribution line automatically by the sequential loading apparatus of the distribution automation equipment. When the circuit breaker is opened, the circuit breaker opened automatically after a predetermined time (for example, after 3 seconds) earlier than the distribution line reclosing device is automatically turned on by the bus reclosing device. Thus, even when the bus overcurrent protection relay device operates as a backup of the distribution line overcurrent protection relay device, the power failure can be smoothly restored.

  According to the present invention, a common circuit breaker for a plurality of insulated non-grounded distribution lines and the first distribution line switch immediately after the distribution line outlet have a relatively large switching capacity. Since it can be configured, a power distribution system with good economic efficiency and maintainability can be constructed.

  Embodiments of the present invention will be described below. FIG. 1 is a circuit configuration diagram of a distribution system of a multi-distribution line 1-breaker system according to a first embodiment of the present invention.

  In this figure, as a configuration of the substation 1, a circuit breaker 4 is provided between the transformer 3 and the distribution line bus 2. A distribution line is connected to the distribution line connected to the bus 2. Fuse-type load switches (hereinafter abbreviated as FDCs) 5a, 5b, and 5c are provided that open when a current of a predetermined value or more calculated based on the accident current flows. All switches on the distribution line side are turned on with a predetermined time when power is supplied from the distribution line, and are opened when power is not supplied. In addition, as a distribution automation facility, the switch has a function to be turned on with a predetermined time when power is supplied, and when a power failure occurs immediately after the power is turned on, the accident continues in the turned-on section. Judgment has an accident section detection lock function that does not turn on the switch even if the next power supply is received. Some switches also have a function that can be controlled to be opened and closed from a distance away from the distribution automation system. Among the switches having these functions, the first switch from the distribution line outlet, that is, the first switch 6a, 6b, 6c, is a switch having a breaking capacity that can cut off the far-end accident current (hereinafter referred to as a switch). AS) and the subsequent switches 7a1, 7a2, 7b1, 7c1, etc. use conventional switches (hereinafter referred to as DM) that do not consider the current interrupting capacity.

  The structure of the protection system on the substation 1 side includes an overcurrent protection relay device (hereinafter abbreviated as OCm) 10 through an instrument transformer 20 inserted between the circuit breaker 4 and the transformer 3, and for accident recovery. The reclosing device (hereinafter abbreviated as RECm) 12 is provided. Each distribution line includes an overcurrent protection relay device (hereinafter abbreviated as OCf) 10a, 10b, 10c and a ground fault via an instrument transformer 20a, 20b, 20c between the bus 2 and the FDS 5a, 5b, 5c. Direction protection relay devices (hereinafter abbreviated as DG) 11a, 11b and 11c and reclosing devices (hereinafter abbreviated as RECf) 12a, 12b and 12c are provided.

  Next, the operation of the above power distribution system will be described for each accident case using the shut-off sequence table of FIG. 1 and FIG.

  As a case 1, when a ground fault occurs in the distribution line 1F, the ground fault is detected by the DG 11a of the distribution line, and the AS 6a is controlled to be opened. By this opening, all DMs 7a1, 7a2,... That are supplied with power by the corresponding distribution line 1F are opened because there is no power source for exciting them. In this automatic recovery, the opened AS 6a is inserted by the corresponding REC f 12a, for example, after 30 seconds, and the reclosing operation is executed. That is, when a ground fault occurs in all the distribution lines, the first AS 6a, 6b, or 6c at the outlet of the substation 1 is opened by the DGs 11a, 11b, and 11c to isolate the location of the accident.

  As the next case 2, when a short-circuit accident occurs at the far end B of the distribution line, if the short-circuit current is a current that can be opened by AS, that is, the distance to the accident point shown in the impedance-time characteristic graph of FIG. When the impedance up to that point is large, that is, when the short-circuit current shown in the current-time characteristic graph of FIG. 3b is smaller than the maximum cutoff current L of the AS, the AS is first controlled to be opened by the time limit characteristic C3 of the OCf 10a. On the other hand, the recovery operation is executed by the RECf 12a as in the case 1. Thus, at the time of a short-circuit accident at the far end where the impedance of the distribution line shown in FIG. 3a becomes large, the accident is avoided by opening the AS of the distribution line in the accident.

  In case 3, when the short-circuit accident occurs at the closest end A of the distribution line, the impedance of the distribution line is small, that is, the short-circuit current is larger than the maximum cut-off current L of the AS. It opens autonomously by the time limit characteristic C2 shown in FIGS. 3a and 3b. Since the power supply of the corresponding distribution line 1F is stopped by this opening, all the switches are opened. Since this recovery operation is a fuse type, automatic recovery is not possible. Therefore, one of the recovery operations from the distribution automation system will be described with reference to FIG. When the accident at the near end A continues, in order to restore the power after the accident section of the distribution line 1F, a healthy distribution line 2F to which power is supplied and the DM7ab across the distribution line 1F in the accident are inserted Then, the power for the 1F healthy section is supplied. At this time, the DM 7a1 installed in the accident section A maintains the open state with the power supplied from the opposite direction, so that no power is supplied to the section of the accident point A, and the same power direction as normal. Supplied in. Subsequent DM7a2 and the like are automatically turned on when power is supplied, and are restored one after another.

  If the short circuit accident of the bus 2 of the substation 1 as the case 4 or the accident cannot be avoided due to the malfunction of the cases 2 and 3, the OCm 10 detects the accident by the time limit characteristic C1 shown in FIGS. 4 is released. For restoration, for example, after 3 seconds by the RECm 12, the circuit breaker 4 is turned on, and power restoration on the distribution line side is restored by the operation of the distribution automation.

  As described above, according to the present embodiment, an expensive circuit breaker conventionally provided in a non-grounded insulated distribution line is replaced with an inexpensive fuse-type load switch and a switch capable of cutting off a small capacity current, Equipped with a set of circuit breakers on the busbar, it becomes a low-cost facility form, the capacity of the protective relay device and remote monitoring control device for protection and monitoring control is reduced, and the maintenance inspection and the like can be reduced. In addition, the fuse type load switch is omitted as case 7, and in the event of a near-end accident, the circuit breaker of the bus is opened and power is transmitted in 3 seconds without disconnecting all AS and all DMs. Is possible.

  The present invention can be used for distribution substation equipment in a power system.

It is a circuit lineblock diagram of a power transmission line system by a 1st embodiment of the present invention. 2 is an operation order table of the line configuration diagram of FIG. 1. FIG. 3A is an operation time characteristic diagram of each protection relay device in FIG. 1, FIG. 3A shows a relationship between impedance and operation time, and FIG. 3B shows a relationship between current and operation time. It is a conventional line configuration diagram.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substation 2 Bus 3 Transformer 4 Circuit breaker 5a, 5b, 5c Fuse load switch 6a, 6b, 6c Small capacity open current type switch 7a1, 7a2, 7b1, 7c1 General switch 10, 10a, 10b, 10c Overload Current protection relay device 11a, 11b, 11c Ground fault direction relay device 12, 12a, 12b, 12c Reclosing device 20, 20a, 20b, 20c Instrument transformer

Claims (3)

A power distribution system comprising an ungrounded transformer, a bus for receiving power supplied through the transformer, and a plurality of distribution lines connected to the bus,
A circuit breaker provided between the transformer and the bus;
Distribution line switches installed near the outlets of each distribution line and capable of cutting off currents during distribution line ground faults and short-circuits at the far end,
A fuse-type load switch that is provided for each distribution line and is automatically opened when the current flows over a predetermined value, and is capable of interrupting a current exceeding the breaking capacity range of the distribution line switch; and
A distribution line transformer for measuring electrical data of each distribution line;
A ground fault direction protective relay device and a distribution line overcurrent protection relay device that perform a protection operation based on the electrical data collected via the distribution line transformer;
A bus transformer for measuring the electrical data of the bus; and
An overcurrent protection relay device for buses that performs a protection operation based on the electrical data collected via the bus transformer,
The distribution line overcurrent protection relay device is set to operate in a capacity range in which the distribution line switch can be cut off.   The bus overcurrent protection relay device operates in an area including the operation region of the distribution line overcurrent protection relay device, and when operating in the operation region, the distribution line overcurrent protection relay device The power distribution system according to claim 1, wherein the power distribution system is set so as to operate more slowly. A distribution line reclosing device for reclosing the distribution line switch of each distribution line, and a busbar reclosing device for reclosing the busbar circuit breaker,
3. The power distribution system according to claim 1, wherein the bus reclosing device performs a reclosing operation earlier than the distribution line reclosing device.

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