Operation voltage automatic setting device for ground fault protective relay

Abstract

To provide an operation voltage automatic setting device for a ground fault protective relay capable of automatically performing operations from calculation of a ground electrostatic capacity C to optimization of an operation voltage setting of a ground fault relay.SOLUTION: In a ground fault relay which protects a system by open-circuiting a breaker of a distribution system in a case where a ground fault current is detected, each time the system is switched, an operation voltage setting of the ground fault relay is automatically calculated and changed.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an operating voltage automatic setting device that can automatically calculate and change the operating voltage setting value of an earth fault relay for protecting a power system.

Background Art

[0002] When an earth fault occurs in a distribution line, it is necessary to immediately detect the occurrence of the accident and isolate the accident section to protect the power system. For the detection of earth faults, earth fault relays installed in the distribution system are used. When an earth fault is detected by the earth fault relay, the circuit breaker connected to the distribution line where the accident occurred is opened to protect the power system (see Patent Document 1 below).

Prior Art Documents

Non-Patent Documents

[0003]

Patent Document 1

[0004] As a method for determining an earth fault by an earth fault relay, for example, it is known that an earth fault is determined to have occurred when the fault voltage becomes equal to or higher than the operating voltage setting value previously set in the earth fault relay.

[0005] The operating voltage setting value can be calculated by measuring the charging current and the capacitance to ground for each bank, and the operating voltage setting value of the earth fault relay is rewritten by periodically calculating the operating voltage setting value.

Summary of the Invention

Problems to be Solved by the Invention

[0006] The rewriting of the setting value needs to be carried out by going to the substation where the ground fault relay is installed, which is laborious and costly. Also, the setting value changes according to the value of the capacitance to ground C, and since the capacitance to ground C varies depending on the system connection status, it is necessary to rewrite the setting value at the timing of system switching, and regular rewriting cannot cope with it.

[0007] If the operating voltage setting value of the ground fault protection relay is not rewritten to the correct value suitable for the current situation of the distribution system, the ground fault relay cannot detect a ground fault, and a situation will occur where the opening operation of the circuit breaker cannot be achieved.

[0008] If the circuit breaker is not opened and the ground fault is left unattended, it will cause fires, electric shocks, and other disasters.

[0009] In order to solve the above problems, an object of the present invention is to provide an automatic operating voltage setting device for a ground fault protection relay that can automatically perform from the calculation of the capacitance to ground C to the optimization of the operating voltage setting value of the ground fault relay.

Means for Solving the Problems

[0010] The invention according to claim 1 connects a remote substation installed in a distribution system and a master station device installed at a power company's business office or the like by a communication line, and by remote monitoring from the master station device, grasps the system state via the remote substation and cooperates with a distribution line automation system that performs remote control of distribution facilities. By monitoring the opening and closing state of the sectionalizer installed in the distribution system at the remote substation, the system switching is detected by the master station device, and by receiving a notification of system switching information from the master station device, it is installed in the distribution system and, when a ground fault is detected, automatically calculates the operating voltage setting value of the ground fault relay that opens the circuit breaker of the distribution system to protect the system.

[0011] An automatic operating voltage setting device for an earth fault protection relay, characterized in that each time the operating voltage setting value of the earth fault relay according to claim 1 is calculated, the previous operating voltage setting value set (stored in memory) in the earth fault relay is rewritten.

Advantages of the Invention

[0012] According to the invention described in claim 1, the setting value can be automatically rewritten at the switching timing of the power system. Also, by using the existing distribution automation system, the switching of the power system can be detected by the master station device of the distribution automation system, so there is no need to introduce a new system.

[0013] According to the invention described in claim 2, each time the operating voltage setting value of the earth fault relay is calculated, the operating voltage setting value of the earth fault relay can be rewritten. Therefore, the earth fault relay can always be operated with the optimal operating setting value, and the power system can be reliably protected from earth fault accidents.

Brief Description of the Drawings

[0014]

Figure 1

Embodiments for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present invention will be described with reference to FIG. 1. FIG. 1 shows a power system in which the automatic operating voltage setting device for an earth fault relay according to the present invention is installed. In FIG. 1, 1 is a distribution transformer installed in substation A for power distribution, and 2 indicates a distribution bus.

[0016] 3 is a substation circuit breaker installed on the distribution bus 2, and 4 is a distribution line 4 branched from the distribution bus 2. 5 is a distribution line circuit breaker installed on the distribution line 4, and 6a, 6b, 6c... are sectional switches installed on the distribution line 4 to divide the distribution line 4 into sections.

[0017] 7a, 7b, 7c... are voltage and current sensors that detect the voltage and current of the distribution line 4 for the main purpose of confirming the absence of power outages and monitoring the on / off states of the sectional switches 6a, 6b, 6c... in each section of the distribution line 4 divided by the sectional switches 6a, 6b, 6c... 8a, 8b, 8c... indicate remote control stations that are attached to utility poles and monitor the opening / closing commands of the sectional switches 6a, 6b, 6c... and the voltage, current, and faults of the distribution line 4.

[0018] For the purpose of detecting the source of harmonics and detecting ground fault short-circuit accidents on the distribution line 4, the remote control stations 8a, 8b, 8c... are equipped with various measuring devices for measuring state quantities such as harmonics on the distribution line 4, the operating state of the ground fault short-circuit relay, and the fundamental voltage and current, and a memory for storing the state quantities measured by the various measuring devices.

[0019] 9 indicates a master station device that collects various measurement data from the remote control stations 8a, 8b, 8c... and automatically monitors and controls the distribution line. It is roughly composed of an operation console 9a and a main computer device 9b installed at a branch office or other location (branch or business office) of the power company. The master station device 9 and the remote control stations 8a, 8b, 8c... are communicably connected by, for example, a dedicated network 10. The master station device 9 and the remote control stations 8a, 8b, 8c... constitute a distribution automation system, aiming to streamline and improve the efficiency of the operation of the distribution system and enhance the supply reliability.

[0020] C1, C2, C3, C4... indicate the capacitance to ground between each distribution line 4 divided by the sectional switches 6a, 6b, 6c... and the ground.

[0021] 12 is a grounding type instrument transformer (EVT) for inputting the ground fault voltage to the ground fault relay 11 during a ground fault, and 13 is an automatic setting device for the operating voltage of the ground fault relay 11 according to the present invention. The ground fault relay 11, the grounding type instrument transformer 12, and the operating voltage setting device 13 are all installed in the distribution substation A.

[0022] As described above, the distribution automation system shown in FIG. 1 is a system for monitoring and controlling a distribution system. Remote substations 8a, 8b, 8c... attached to each utility pole are communicably connected to a master station device 9, and sectional switches 6a, 6b, 6c... on the utility pole are controlled to open and close via the remote substations 8a, 8b, 8c....

[0023] The master station device 9 constantly monitors the operating state of the distribution line 4 via the remote substations 8a, 8b, 8c.... For example, when a distribution line accident such as a ground fault occurs, the accident location is identified, and the sectional switches sandwiching the section including the accident location are opened to disconnect from the healthy section. The opening (closing) operation of the sectional switches 6a, 6b, 6c... can be executed by operating the operation console 9a of the master station device 9 or automatically. After disconnecting the accident section from the healthy section, power is supplied to the healthy section. The power supply to the healthy section is realized not only by power transmission from the distribution substation A, for example, but also by reverse power transmission from another distribution substation B (not shown).

[0024] To identify the accident section, for example, when a distribution line accident such as a ground fault occurs, first the distribution line breaker 5 is opened to make the fault location have no voltage. Next, the distribution line breaker 5 is reclosed, and the sectional switches 6a, 6b, 6c... on the power supply side are sequentially energized to perform re-power transmission to the healthy section. Then, when the re-power transmission reaches the accident section, the distribution line breaker 5 is opened again. In this way, by identifying the sectional switch that divides the accident section, when the distribution line breaker 5 is reclosed again, the sectional switch that divides the accident section can be locked in the open state to separate the accident section from the healthy section.

[0025] Note that the above distribution automation system not only responds to faults in the distribution line, but also improves the power supply reliability of the distribution system, such as when a power outage occurs due to an accident (such as an instantaneous voltage drop) in the distribution substation, by operating the operation console 9a of the master station device 9 or automatically supplying power from surrounding distribution substations to the area where the power outage occurred.

[0026] As described above, when a fault such as a ground fault occurs in the distribution line 4, the distribution line breaker 5 is opened to make the fault location have no voltage. The occurrence of the ground fault is detected by the ground fault relay 11 shown in FIG. 1.

[0027] Specifically, an operating voltage setting value (setting value Vo) calculated by measuring the charging current and the capacitance to ground for each bank in advance is set (stored in the memory) in the ground fault relay 11. When the distribution line voltage (Vo during the accident) at the time of the ground fault occurrence is equal to or higher than this operating voltage setting value (setting value Vo ≤ Vo during the accident), it is determined that a ground fault has occurred, and the distribution line breaker 5 is opened.

[0028] Here, when the above zero-phase voltage Vo is expressed by the zero-phase current Io and the admittance Y, (Equation 1) Vo = Io / Y. Also, for simplicity, when the admittance Y is expressed by omitting the line resistance and reactance, (Equation 2) Y = jω≡. Therefore, the zero-phase voltage is expressed as (Equation 3) Vo = Io / jω≡.

[0029] Therefore, as described above, when the sectional switches 6a, 6b, 6c... are opened and closed by the distribution automation system, the value of the capacitance to ground C changes each time. For example, in the state where all the sectional switches 6a, 6b, 6c... shown in FIG. 1 are closed, the capacitance to ground C takes the value of C = C1 + C2 + C3 +..., but when the sectional switch 2 is opened, the capacitance to ground C takes the value of C = C1 + C2, so the capacitance to ground becomes smaller. When the capacitance to ground C becomes smaller, from the above (Equation 3), the value of the voltage Vo during the accident becomes larger than the assumed value. When the value of Vo during the accident becomes larger than the assumed value, the ground fault relay 11 will malfunction and operate unnecessarily.

[0030] Conversely, when the sectionalizer 2 changes from the open state to the closed state, the capacitance to ground C changes from the value of C = C1 + C2 to the value of C = C1 + C2 + C3 + …, and the capacitance to ground increases. When the capacitance to ground C increases, from the above (Equation 3), the value of the fault voltage Vo becomes smaller than the assumed value. When the value of Vo during a fault becomes smaller than the assumed value, the ground fault relay 11 enters a non-operating state, and a situation occurs where the system cannot be protected from a ground fault accident.

[0031] As described above, since the value of the fault voltage Vo changes depending on the value of the capacitance to ground C, in order to derive the correct operating voltage setting value, it is essential to accurately grasp the capacitance to ground C. Therefore, in the present invention, an automatic operating voltage setting device 13 for the ground fault relay 11 is installed in the distribution substation, and the operating voltage setting value is automatically calculated by the setting device 13 and automatically rewritten to the operating voltage setting value stored in the ground fault relay 11.

[0032] As a result, there is no longer a need to periodically measure and calculate the charging current and the capacitance to ground for each bank as in the past, and for an operator to go to the substation where the ground fault relay 11 is installed to perform the operation of rewriting the setting value.

[0033] In addition, the automatic calculation of the setting value by the automatic operating voltage setting device 13 is linked with the above-described distribution automation system. When the sectionalizers 6a, 6b, 6c… and the distribution line breaker 5 are opened and closed, information (system switching information) on which sectionalizer has been opened and closed is notified from the master station device 9 to the automatic operating voltage setting device 13, enabling the automatic setting device 13 to accurately grasp the capacitance to ground C.

[0034] As a result, the automatic setting device 13 can calculate the correct setting value and can always set the accurate setting value to the ground fault relay 11. As a result, it is possible to reliably prevent malfunction and non-operation of the distribution line breaker 5 by the ground fault relay 11, and it is possible to reliably protect the system from a ground fault accident.

[0035] As described above, according to the operating voltage automatic setting device of the present invention, the operating voltage setting value of the ground fault relay can be automatically calculated, so there is no need for an operator to measure and calculate the charging current and capacitance to ground for each bank of the setting value.

[0036] Also, each time the system switches, the operating voltage automatic setting device automatically calculates the setting value and rewrites the setting value of the ground fault relay, so that the correct setting value can always be set for the ground fault relay, and malfunction and non-operation of the distribution line breaker can be reliably prevented.

[0037] Furthermore, since it is not necessary for an operator to go to the substation where the ground fault relay is installed for rewriting the setting value of the ground fault relay, the burden and cost of the operator required for the rewriting work can be significantly reduced.

[0038] Moreover, since the switching of the system can be grasped in cooperation with the existing distribution automation system, there is no need to introduce a new system, and the hurdle for introducing this device can be lowered.

Industrial Applicability

[0039] The present invention is applicable to the setting of the operating voltage setting value of the ground fault relay.

Explanation of Signs

[0040] 1 Distribution transformer 2 Distribution bus 3 Substation breaker 4 Distribution line 5 Distribution line breaker 6a, 6b, 6c… Sectionalizer 7a, 7b, 7c… Voltage and current sensor 8a, 8b, 8c… Remote substation 9 Master station device 9a Operator console 9b Main computer device 10 Dedicated network 11 Ground fault relay 12 Earthing type instrument transformer (EVT) 13 Operating voltage automatic setting device Substation for power distribution of A and B

Claims

1. Connect a remote substation installed in a power distribution system and a master station device installed in a branch office of an electric power company or the like with a communication line, and through remote monitoring from the master station device, grasp the system state via the remote substation and perform remote control of power distribution facilities. Cooperate with a power distribution line automation system, monitor the opening and closing state of sectional switches installed in the power distribution system at the remote substation, detect system switching at the master station device, and receive a notification of system switching information from the master station device. Then, an automatic operating voltage setting device for a ground fault relay that is installed in a power distribution system and automatically calculates the operating voltage setting value of a ground fault relay that opens the circuit breaker of the power distribution system to protect the system when a ground fault is detected.

2. The automatic operating voltage setting device for a ground fault protection relay according to claim 1, wherein each time the operating voltage setting value of the ground fault relay is calculated, the operating voltage setting value stored in the ground fault relay is rewritten.

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