Distributed grounding fault line selection device and method

Abstract

The invention discloses a distributed grounding fault line selection device and method, and relates to the technical field of grounding fault processing, and the device comprises an intelligent grounding mechanism, a pole-mounted circuit breaker, an intelligent feeder terminal, a zero-sequence current transformer, and a preprocessor. The pole-mounted circuit breaker is used for controlling the closing and opening of a line where the pole-mounted circuit breaker is located; the zero-sequence current transformer is used for monitoring the zero-sequence current value of the line where the zero-sequence current transformer is located; the preprocessor is used for collecting a zero-sequence current value signal of the zero-sequence current transformer and sending an alarm signal to the intelligent grounding mechanism and the intelligent feeder terminal; the intelligent grounding mechanism can receive the alarm signal, transfer a single-phase grounding fault current and determine a phase and a line where a single-phase grounding fault is located; and the intelligent feeder terminal can receive the alarm signal and control the pole-mounted circuit breaker to be switched off. The method has the effect of improving the timeliness of opening of the feeder where the single-phase earth fault is located.

Description

Technical Field

[0001] The present application relates to the technical field of ground fault processing, and in particular to a distributed ground fault line selection device and method. Background Art

[0002] Single-phase grounding is a common circuit fault in the power distribution system. This fault mostly occurs in humid and rainy weather environments due to many factors such as tree barriers, breakdown of insulators on distribution lines, single-phase line breaks, and animal and plant hazards. Single-phase grounding not only affects the normal power supply of the distribution system to users, but also poses the risk of overvoltage and equipment burnout, and even causes phase-to-phase short circuits, leading to fires, casualties, and large-scale equipment damage.

[0003] After a single-phase grounding fault occurs in a certain section of the feeder, it will be difficult for the users connected to the phase line where the fault occurs to obtain a stable power supply, and the electrical equipment will be difficult to operate continuously. Therefore, the single-phase grounding fault needs to be handled in a timely manner.

[0004] Generally speaking, after a single-phase grounding fault occurs, the intelligent feeder terminal at the fault location sends a fault alarm to the system background, and the background performs data analysis to obtain information such as the fault phase and fault type, and then generates an action instruction and sends an action instruction (such as a feeder trip instruction) to the intelligent feeder terminal. After receiving the action instruction, the intelligent feeder terminal controls the faulty feeder to trip and disconnect the power supply, so that the staff can safely handle the single-phase grounding fault.

[0005] Since the distance span of fault signal transmission is relatively large, the signal transmission process is subject to various interferences, especially electromagnetic interference of the power system facilities themselves, climate influence, terrain influence, etc. Therefore, the timeliness and stability of the tripping of the feeder where the fault is located need to be further improved. Although the traditional small current grounding system has a certain anti-interference ability, the system wiring is complex and the equipment maintenance cost is high. Summary of the invention

[0006] In order to improve the timeliness of tripping the feeder where a single-phase grounding fault occurs, the present application provides a distributed grounding fault line selection device and a grounding fault line selection method.

[0007] In a first aspect, the present application provides a distributed ground fault line selection device, which adopts the following technical solution: A distributed ground fault line selection device, comprising an intelligent grounding mechanism, a pole-mounted circuit breaker, an intelligent feeder terminal, a zero-sequence current transformer and a preprocessor; The pole-mounted circuit breaker is used to control the closing and opening of the circuit. The zero-sequence current transformer is used to monitor the zero-sequence current value of the line; The preprocessor is used to collect the zero-sequence current value signal of the zero-sequence current transformer and send an alarm signal to the intelligent grounding mechanism and the intelligent feeder terminal; The intelligent grounding mechanism is capable of receiving the alarm signal and transferring the single-phase grounding fault current and determining the phase and line where the single-phase grounding fault is located; The intelligent feeder terminal is capable of receiving the alarm signal and controlling the pole-mounted circuit breaker to open.

[0008] Through the above technical solution, when the line is operating normally, the vector sum of the currents of each phase is zero. When a single-phase grounding fault occurs in one phase, the state of the current vectors of each phase being zero is unbalanced, and the vector sum of the currents of each phase is not zero. At this time, magnetic flux is generated in the core of the zero-sequence current transformer, thereby generating a current signal, which is collected and converted by the preprocessor and transmitted to the intelligent grounding mechanism and the intelligent feeder terminal.

[0009] Among them, after receiving the alarm signal, the intelligent grounding mechanism first transfers the short-circuit current, determines the phase of the single-phase grounding fault, then determines the single-phase grounding fault line, and reports the phase and line where the fault is located to the background.

[0010] Among them, after the intelligent feeder terminal receives the alarm signal for a period of time, it controls the pole-mounted circuit breaker of the corresponding line to open or the two pole-mounted circuit breakers closest to the fault location to open, thereby cutting off the current of the faulty line. At this time, the operator can perform single-phase grounding fault inspection and processing in a more targeted manner.

[0011] This technical solution does not need to rely on the information transmission and interaction between the power dispatching system and the intelligent feeder terminal. It only needs to use the intelligent grounding mechanism to determine the phase where the fault is located and effectively transfer the current of the short-circuit fault. The intelligent feeder terminal controls the column-mounted circuit breaker to open the feeder where the single-phase grounding fault is located, thereby effectively improving the timeliness of opening the feeder where the single-phase grounding fault is located.

[0012] In addition, compared with the traditional low-current grounding system, the operator does not need to perform complicated wiring operations and can directly use the device on site, which reduces operation and maintenance costs.

[0013] In a preferred example, the present application can be further configured as follows: the intelligent grounding mechanism includes a controller, an arc extinguishing unit, a line selection unit and a current transformer; The arc extinguishing unit comprises a phase-splitting circuit breaker, the input end of the phase-splitting circuit breaker is connected to the three-phase line, the phase-splitting circuit breaker is provided with a switch 1, a switch 2 and a switch 3 corresponding to the three-phase lines respectively, the arc extinguishing unit further comprises a switch 4 and a current limiting resistor, the switch 4 and the current limiting resistor are connected in parallel with each other, one end of the current limiting resistor is grounded, and the other end is connected to the output end of the phase-splitting circuit breaker; The line selection unit includes a three-phase circuit breaker and a grounding transformer with impedance, the input end of the three-phase circuit breaker is connected to the three-phase line, one end of the grounding transformer is grounded, and the other end of the grounding transformer is connected to the output end of the three-phase switch; The controller is used to collect the three-phase line voltage value, the zero-sequence voltage value and the current value flowing through the current limiting resistor, and control the closing and opening of the switch 1, the switch 2, the switch 3, the switch 4 and the three-phase circuit breaker; The current transformer 1 is installed on a common grounding circuit of the current limiting resistor and the switch 4.

[0014] The relevant technical effects of this technical solution are described in detail in the specific implementation manner.

[0015] In a preferred example, the present application can be further configured as follows: the intelligent grounding mechanism also includes a pre-circuit breaker, the input end of the pre-circuit breaker is connected to the three-phase line, and the output end of the pre-circuit breaker is connected to the phase circuit breaker and the three-phase circuit breaker.

[0016] Through the above technical solution, the front circuit breaker is used to control the switching on and off of the intelligent grounding mechanism, so as to facilitate the installation, inspection and equipment maintenance of the intelligent grounding mechanism.

[0017] In a preferred example, the present application can be further configured as follows: a current transformer 2 is installed on the output end line of the grounding transformer.

[0018] Through the above technical solution, by installing current transformer 2 on the output line of the grounding transformer, the current change of the grounding transformer can be monitored in real time, and it can be determined whether the equipment is abnormal (such as overload, short circuit, etc.) to ensure the safe operation of the equipment.

[0019] In a preferred example, the present application may be further configured as follows: the opening time of the pole-mounted circuit breaker is consistent with the time when the fault line selection information of the intelligent grounding mechanism is issued.

[0020] Through the above technical solution, since the opening time of the pole-mounted circuit breaker is consistent with the time when the fault line selection information of the intelligent grounding mechanism is sent, after the intelligent grounding mechanism completes the determination of the faulty line and sends the information of the line where the fault is located, at the same time, the intelligent feeder terminal immediately controls the corresponding pole-mounted circuit breaker to open the circuit, cutting off the faulty line or the section where the faulty line is located, thereby shortening the energized operation time of the faulty line, minimizing the safety risks caused by single-phase grounding faults, and also giving maintenance personnel sufficient time for maintenance.

[0021] In a preferred example, the present application may be further configured as follows: further comprising a backup power supply, wherein the backup power supply is used to provide backup power to the intelligent feeder terminal.

[0022] Through the above technical solution, when the line where the smart feeder terminal is located is powered off, the backup power supply provides power to the smart feeder terminal to ensure that the smart feeder terminal can continue to operate, giving full play to the three remote functions of the smart feeder terminal (telemetry, telesignaling, and remote control), reducing the possibility of loss of connection between the smart feeder terminal and the main station, thereby improving the stability of the entire distribution network system.

[0023] In the second aspect, based on the above-mentioned distributed ground fault line selection device, the present application provides a distributed ground fault line selection method, which adopts the following technical solution: A distributed ground fault line selection method comprises the following steps: The preprocessor acquires abnormal current information of the zero-sequence current transformer in real time, and transmits the abnormal current information to the intelligent grounding mechanism and the intelligent feeder terminal; The intelligent grounding mechanism controls the switch of the phase circuit breaker to close according to the abnormal current information; If the short-circuit fault disappears, the intelligent grounding mechanism exits; if the fault still exists, the switch 4 is closed; Closing the three-phase circuit breaker and switching on the grounding transformer; Opening the phase-splitting circuit breaker and the switch 4; According to the current fluctuation information of each zero-sequence current transformer, the line where the single-phase grounding fault is located is determined, the fault line information is generated, and reported to the system backend; The intelligent feeder terminal controls the pole-mounted circuit breaker of the line where the fault occurs to open.

[0024] Through the above technical scheme, the method is implemented through the grounding fault line selection device to transfer the short-circuit current and determine the single-phase grounding fault line. There is no need to rely on the information transmission and interaction between the power dispatching system and the intelligent feeder terminal. Only the intelligent grounding mechanism is needed to complete the determination of the phase where the fault is located and effectively transfer the current of the short-circuit fault. The intelligent feeder terminal controls the pole-mounted circuit breaker to open the feeder where the single-phase grounding fault is located, which effectively improves the timeliness of opening the feeder where the single-phase grounding fault is located.

[0025] In a preferred example, the present application can be further configured as follows: the intelligent grounding mechanism controls the closing of the switch of the corresponding phase of the phase circuit breaker according to the phase where the abnormal current information is located, including: According to the abnormal current information, the intelligent grounding mechanism controls the closing of the switch of the corresponding phase of the phase circuit breaker; Acquire the current information of the current transformer 1, and analyze whether the closing phase of the phase-splitting circuit breaker is correct according to the current information of the current transformer 1; If the closing is wrong, the wrong switch in the phase-splitting circuit breaker is disconnected, and the switches of other phases are closed until the closing is correct.

[0026] Through the above technical solution, multiple switches in the phase-splitting circuit breaker respectively control the grounding closing and opening of different phases, which can timely transfer the single-phase grounding fault current. It has certain fault tolerance and error correction functions, and improves the stability of single-phase grounding fault current transfer.

[0027] In a preferred example, the present application can be further configured such that after generating the fault line information and reporting it to the system backend, the following steps are further included: Record the serial numbers of several intelligent feeder terminals closest to both sides of the line where the single-phase grounding fault occurs; If the intelligent feeder terminal closest to the line where the single-phase grounding fault occurs cannot drive the corresponding pole-mounted circuit breaker, the pole-mounted circuit breaker closest to the line where the fault occurs and operating normally is opened; Based on the fault line information of the newly recorded single-phase grounding fault, the frequency of single-phase grounding faults occurring in multiple lines is calculated; Based on the frequency of single-phase grounding faults occurring in multiple lines and the recently normal operating pole-mounted circuit breakers of the single-phase grounding fault lines, a priority line section for troubleshooting is generated.

[0028] Through the above technical solution, each time the line where the single-phase grounding fault is located is determined, the smart feeder terminals near the line where the fault is located are recorded. If the smart feeder terminal closest to the fault line cannot drive the corresponding pole-mounted circuit breaker (called the fault circuit breaker) to close, then the system background controls the pole-mounted circuit breaker that is closest to the fault circuit breaker to open, so as to complete the cutting off of the power supply line section.

[0029] After the system enters the fault line information, it recalculates the frequency of single-phase grounding faults on each line to generate priority line sections for troubleshooting. It prioritizes troubleshooting of lines or line sections where single-phase grounding faults frequently occur, thereby improving the efficiency of fault troubleshooting.

[0030] In summary, this application includes the following beneficial technical effects: 1. This device does not need to rely on the information transmission and interaction between the power dispatching system and the intelligent feeder terminal. It can determine the phase where the fault is located, effectively transfer the current of the short-circuit fault, and complete the line cutting through the intelligent grounding mechanism, which effectively improves the timeliness of the feeder disconnection where the single-phase grounding fault is located; 2. The intelligent grounding mechanism in this device effectively improves the fault tolerance rate of fault current transfer by closing multiple switches of the phase circuit breaker in sequence; 3. After the intelligent grounding mechanism completes the determination of the faulty line and sends out the information of the faulty line, at the same time, the intelligent feeder terminal immediately controls the corresponding pole-mounted circuit breaker to open the switch, cuts off the faulty line or the section where the faulty line is located, shortens the energized operation time of the faulty line, and minimizes the safety risks caused by single-phase grounding faults, thus giving maintenance personnel sufficient time for maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the overall structure of an embodiment of the present application, mainly illustrating the installation positions of the pole-mounted circuit breaker and the intelligent feeder terminal.

[0032] Figure 2 It is a circuit diagram of the intelligent grounding mechanism in the embodiment of the present application.

[0033] Figure 3 It is a flow chart of the ground fault line selection method in the embodiment of the present application.

[0034] Figure 4 It is a flow chart of phase determination in the ground fault line selection method.

[0035] Figure 5 It is a schematic diagram of the flow chart for generating the priority line section in the ground fault line selection method.

[0036] Description of reference numerals: 1. Intelligent grounding mechanism; 11. Current transformer 1; 12. Phase circuit breaker; 121. Switch 1; 122. Switch 2; 123. Switch 3; 124. Switch 4; 125. Current limiting resistor; 13. Three-phase circuit breaker; 14. Grounding transformer; 15. Pre-circuit breaker; 16. Current transformer 2; 2. Pole circuit breaker; 3. Intelligent feeder terminal; 4. Backup power supply. DETAILED DESCRIPTION

[0037] The following is combined with Figure 1 -Attached Figure 5 This application is described in further detail.

[0038] An embodiment of the present application discloses a distributed ground fault line selection device.

[0039] See attached Figure 1 and attached Figure 2 As shown, a distributed ground fault line selection device includes an intelligent grounding mechanism 1, a pole-mounted circuit breaker 2, an intelligent feeder terminal 3, a zero-sequence current transformer and a preprocessor.

[0040] See attached Figure 1 As shown, the pole-mounted circuit breaker 2 is installed on the line tower and is used to control the closing and opening of the line.

[0041] Zero-sequence current transformer is used to monitor the zero-sequence current value of the line. When the line is operating normally, the vector sum of the currents of each phase is zero; when a single-phase grounding fault occurs in one phase of the line, the state of the zero vector current of each phase is unbalanced, and the vector sum of the currents of each phase is not zero. At this time, magnetic flux is generated in the core of the zero-sequence current transformer, thereby generating a current signal.

[0042] The preprocessor is used to collect the zero-sequence current value signal of the zero-sequence current transformer and send an alarm signal to the intelligent grounding mechanism 1 and the intelligent feeder terminal 3. The "alarm signal" referred to here refers to the signal of zero-sequence abnormality.

[0043] See attached Figure 1 and attached Figure 2 As shown, the intelligent grounding mechanism 1 can receive the above-mentioned alarm signal, transfer the single-phase grounding fault current and determine the phase and line where the single-phase grounding fault is located. The specific structure and principle of the intelligent grounding mechanism 1 will be described in detail later.

[0044] See attached Figure 1 As shown, the intelligent feeder terminal 3 can receive the above-mentioned alarm signal and control the pole-mounted circuit breaker 2 to open. In addition, the device also equips the intelligent feeder terminal 3 with a backup power supply 4 for providing a backup power supply to the intelligent feeder terminal 3, ensuring that the intelligent feeder terminal 3 can continue to operate, giving full play to the three remote functions (telemetry, telesignaling, and remote control) of the intelligent feeder terminal 3, reducing the possibility of disconnection between the intelligent feeder terminal 3 and the master station, thereby improving the stability of the entire distribution network system.

[0045] After a single-phase grounding fault occurs, magnetic flux is generated in the core of the zero-sequence current transformer, thereby generating a zero-sequence current. After the preprocessor collects the zero-sequence current signal, it is converted into an alarm signal and sent to the intelligent grounding mechanism 1 and the intelligent feeder terminal 3.

[0046] The intelligent grounding mechanism 1 first transfers the short-circuit current and determines the phase where the fault is located, then determines the line where the fault is located, and reports the fault phase information and fault line information to the system backend. After the fault phase determination and line determination information are sent, the intelligent feeder terminal 3 controls the circuit breaker 2 on the control column to open and cut off the line where the fault is located.

[0047] The opening of the above-mentioned pole-mounted circuit breaker 2 can be to cut off the current of a certain line. For example, if the fault is located on the branch where the No. 3 tower is located, only the circuit breaker on the No. 3 tower is controlled to be opened; it can also be the current of a certain line section where the fault is located. For example, if the fault is on the No. 4 tower, and the pole-mounted circuit breaker 2 is not installed on the No. 4 tower, then the No. 3 tower and the No. 5 tower installed with the pole-mounted circuit breaker 2 are controlled to be opened to achieve the purpose of cutting off the line section.

[0048] This device does not need to rely on the information transmission and interaction between the power dispatching system and the intelligent feeder terminal 3. It only needs to use the intelligent grounding mechanism 1 to complete the determination of the phase where the fault is located and effectively transfer the current of the short-circuit fault. It also controls the pole-mounted circuit breaker 2 to open through the intelligent feeder terminal 3 to complete the disconnection of the line where the single-phase grounding fault is located, thereby improving the timeliness of opening the feeder where the single-phase grounding fault is located.

[0049] The tripping time of the pole-mounted circuit breaker 2 is consistent with the time when the fault line selection information of the intelligent grounding mechanism 1 is sent out. When a permanent single-phase grounding fault occurs, through the time coordination between the intelligent grounding mechanism 1 and the intelligent feeder terminal 3 (the intelligent feeder terminal 3 controls the pole-mounted circuit breaker 2 to be tripped), the pole-mounted circuit breaker 2 is immediately tripped after the intelligent grounding mechanism 1 sends out the fault phase and fault line information, shortening the energized operation time of the fault line, minimizing the safety risks caused by the single-phase grounding fault, and also giving maintenance personnel sufficient time for maintenance.

[0050] See attached Figure 1 and attached Figure 2 As shown, the intelligent grounding mechanism 1 includes a controller, an arc extinguishing unit, a line selection unit, a current transformer 11, a pre-circuit breaker 15 and a current transformer 2 16.

[0051] See attached Figure 1 and attached Figure 2As shown, the arc extinguishing unit includes a phase circuit breaker 12, the input end of the phase circuit breaker 12 is connected to the three-phase line through the pre-circuit breaker 15, and the phase circuit breaker 12 is provided with a switch 121, a switch 2 122 and a switch 3 123, and the above three switches correspond to the three-phase lines respectively. The arc extinguishing unit also includes a switch 4 124 and a current limiting resistor 125, and the switch 4 124 and the current limiting resistor 125 are connected in parallel with each other, one end of the current limiting resistor 125 is grounded, and the other end is connected to the output end of the phase circuit breaker 12. The current transformer 11 is installed on the common grounding line of the current limiting resistor 125 and the switch 4 124.

[0052] See attached Figure 1 and attached Figure 2 As shown, the line selection unit includes a three-phase circuit breaker 13 and a grounding transformer 14 with impedance. The input end of the three-phase circuit breaker 13 is connected to the three-phase line through a pre-circuit breaker 15. One end of the grounding transformer 14 is grounded, and the other end of the grounding transformer 14 is connected to the output end of the three-phase switch. Current transformer 2 16 is installed on the output end line of the grounding transformer 14 to monitor the current change of the grounding transformer 14 in real time and determine whether there is an abnormality in the equipment.

[0053] See attached Figure 1 and attached Figure 2 As shown, the controller is used to collect the three-phase line voltage value, the zero-sequence voltage value and the current value flowing through the current limiting resistor 125, and control the closing and opening of switch 1 121, switch 2 122, switch 3 123, switch 4 124 and the three-phase circuit breaker 13.

[0054] After the intelligent grounding mechanism 1 receives the alarm signal sent by the preprocessor, the switch of the phase circuit breaker 12 in the intelligent grounding mechanism 1 is first closed (i.e., one of the switch 1 121, the switch 2 122, and the switch 3 123 of the phase circuit breaker 12). At this time, the switch 4 124 is in the open state. By monitoring the current change flowing through the current limiting resistor 125 through the current transformer 11, it can be determined whether the closing phase is correct.

[0055] If the closing is correct, the short-circuit current is suppressed by the current limiting resistor 125, and the current after current limiting is transferred to the grounding point, and the current at the fault point is shunted. At this time, the current at the fault point is reduced, and the arc of the single-phase grounding fault disappears, thereby completing the arc extinguishing process and reducing the harm caused by the single-phase grounding.

[0056] If the closing error occurs, the wrong switch (such as switch one 121) is disconnected, and other phase switches are closed (such as switch two 122 or switch three 123). Therefore, the intelligent grounding mechanism 1 has the functions of closing fault tolerance and error correction. Even if the closing error occurs, it can perform self-correction and transfer the fault current in time.

[0057] After the above-mentioned closing action is completed, the switch four 124 is closed with a delay. If the insulation is restored and the fault disappears, the fault is a transient fault (such as lightning strike, short-term contact between animals and plants, etc.), and the intelligent grounding mechanism 1 exits, and the line resumes normal operation; if the insulation is not restored and the fault does not disappear, the fault is a permanent fault (such as damage and aging of line insulation materials, damage to electrical equipment, etc.). At this time, the switch four 124 is closed, the current limiting resistor 125 is short-circuited, and the faulty phase is metal-grounded. At this time, the faulty phase voltage becomes zero, the non-faulty phase voltage rises to the line voltage, and the three-phase voltage remains unchanged, so that the power grid system can continue to operate for a period of time (usually 1 to 2 hours) to facilitate the investigation and repair of permanent faults.

[0058] After switch four 124 is closed, the three-phase circuit breaker 13 is closed, the grounding transformer 14 with impedance is switched on, and then the phase circuit breaker 12 and switch four 124 are disconnected. When a single-phase grounding fault occurs, the zero-sequence voltage will rise sharply (to about 100V), and after the grounding transformer 14 is switched on, the zero-sequence voltage will drop significantly, and the waveform of the zero-sequence voltage will show an obvious concave change. At this time, the zero-sequence current waveforms of the fault line and the non-fault line will show obvious differences, that is, the zero-sequence current of the fault branch increases, and the zero-sequence current of the non-fault branch decreases. According to this feature, the fault line and the non-fault line can be distinguished, thereby completing the line determination of the single-phase grounding fault, effectively improving the accuracy of the fault line determination, and thus improving the work efficiency of fault handling.

[0059] See attached Figure 1 , Attachment Figure 2 And attached Figure 3 As shown, based on the above-mentioned distributed ground fault line selection device, the embodiment of the present application also discloses a distributed ground fault line selection method, which includes the following steps.

[0060] S101 , a preprocessor obtains abnormal current information of a zero-sequence current transformer in real time, and transmits the abnormal current information to an intelligent grounding mechanism 1 and an intelligent feeder terminal 3 .

[0061] In implementation, the preprocessor collects current anomalies of the zero-sequence current transformer, generates current anomaly information and sends it to the intelligent grounding mechanism 1 and the intelligent feeder terminal 3, thereby triggering a series of actions of the intelligent grounding mechanism 1 and the intelligent feeder terminal 3.

[0062] S102 . The intelligent grounding mechanism 1 controls the switch of the phase circuit breaker 12 to close according to the abnormal current information.

[0063] In practice, after receiving the abnormal current information, the intelligent grounding mechanism 1 controls the switch of the phase circuit breaker 12 to close and transfer the fault current, while the current at the fault point decreases and the arc is extinguished, thereby achieving the effect of arc extinguishing and transferring the fault current.

[0064] S103. If the short-circuit fault disappears, the intelligent grounding mechanism 1 exits; if the fault still exists, the switch 4 124 is closed.

[0065] In practice, for instantaneous short-circuit faults, such as brief contact between animals and plants, lightning strikes, etc., usually after arc extinguishing, the arc is extinguished and the fault disappears, and no human intervention is required, and the device can be directly exited. For permanent short-circuit faults, such as damage and aging of line insulation materials, damage to electrical equipment, etc., at this time, switch 4 124 is closed, the current limiting resistor 125 is short-circuited, and the fault phase is metal-grounded. At this time, the voltage of the fault phase becomes zero, the voltage of the non-fault phase rises to the line voltage, and the three-phase voltage remains unchanged, so that the power grid system can continue to operate for a period of time (usually 1 to 2 hours) to facilitate the investigation and repair of permanent faults.

[0066] For the determination of the specific fault line, see below.

[0067] S104 , closing the three-phase circuit breaker 13 and switching on the grounding transformer 14 .

[0068] S105, opening the phase circuit breaker 12 and the switch 4 124.

[0069] S106. According to the current fluctuation information of each zero-sequence current transformer, determine the line where the single-phase grounding fault is located, generate fault line information, and report it to the system backend.

[0070] During implementation, after the grounding transformer 14 is switched on and the phase circuit breaker and switch four 124 are opened, the zero-sequence voltage will be significantly reduced, and the waveform of the zero-sequence voltage will show an obvious concave change. At this time, there will be obvious differences in the zero-sequence current waveforms of the fault line and the non-fault line, that is, the zero-sequence current of the fault branch is significantly increased, and the zero-sequence current of the non-fault branch is significantly reduced. Based on this feature, the fault line and the non-fault line can be distinguished, and this change in zero-sequence current can be captured by the zero-sequence current transformer and the preprocessor, thereby completing the line determination of the single-phase grounding fault, effectively improving the accuracy of the fault line determination, thereby improving the work efficiency of fault handling.

[0071] S107. The intelligent feeder terminal 3 controls the pole-mounted circuit breaker 2 of the line where the fault occurs to open.

[0072] In implementation, after the fault line information (including the fault phase and the fault line) is sent out, the intelligent feeder terminal 3 controls the pole-mounted circuit breaker 2 to open the circuit. The pole-mounted circuit breaker 2 referred to here can be the pole-mounted circuit breaker 2 on a specific pole tower, or the pole-mounted circuit breaker 2 at both ends of a line section. The relevant description has been made above and will not be repeated here.

[0073] The pole-mounted circuit breaker 2 may be opened at a time after or at the same time as the fault line information is sent, in order to shorten the time after the fault line information is sent and cut off the faulty line as soon as possible.

[0074] See attached Figure 1 , Attachment Figure 2 And attached Figure 4 As shown, the specific steps of step S102 are as follows.

[0075] S201. According to the abnormal current information, the intelligent grounding mechanism 1 controls the switch of the corresponding phase of the phase circuit breaker 12 to close.

[0076] In implementation, after receiving the abnormal current information, the intelligent grounding mechanism 1 controls a phase switch (ie, one of the three switches 121 to 123 ) of the phase circuit breaker 12 to close.

[0077] S202, obtaining the current information of the current transformer 11, and analyzing whether the closing phase of the phase-splitting circuit breaker 12 is correct according to the current information of the current transformer 11.

[0078] In practice, if the circuit breaker is closed correctly, the short-circuit current will be transferred, and the current transformer 11 will be able to detect obvious fluctuations, thereby being able to determine whether the circuit breaker is closed correctly.

[0079] S203, if the closing is wrong, disconnect the wrong switch in the phase circuit breaker 12, and close the switches of other phases until the closing is correct.

[0080] In implementation, if the first switch 121 is closed by the phase-splitting circuit breaker 12, and the closing is wrong, then the switch 121 is opened, and the switch 2 122 is closed, and the open state of the switch 3 123 is maintained; if the closing is still wrong, the open state of the switch 1 121 is maintained, the switch 2 122 is opened, and the switch 3 123 is opened. This is the most undesirable phase selection process. Other situations can be obtained by making relevant simplified processing on this basis, and will not be elaborated.

[0081] See attached Figure 1 , Attachment Figure 2 as well as Figure 5As shown, after step S202, the following processing steps may also be included.

[0082] S301. Record the serial numbers of several intelligent feeder terminals 3 closest to each other on both sides of the line where the single-phase grounding fault occurs.

[0083] In implementation, for example, among pole towers 1 to 10, pole-mounted circuit breakers 2 are installed on odd-numbered towers, while pole-mounted circuit breakers 2, zero-sequence current transformers and other equipment are not installed on even-numbered towers (this is also true in actual operation. In order to control costs and reduce losses, the above equipment is not installed on every tower). If a single-phase grounding fault occurs on pole tower 4, pole towers 1, 3, 5 and 7 can be recorded.

[0084] S302: If the intelligent feeder terminal 3 closest to the line where the single-phase grounding fault occurs cannot drive the corresponding pole-mounted circuit breaker 2, the pole-mounted circuit breaker 2 closest to the line where the fault occurs and operating normally is opened.

[0085] In implementation, based on the example of S301, it is usually necessary to open the pole-mounted circuit breakers 2 on the No. 3 and No. 5 pole towers to facilitate the maintenance of the faulty line. However, if the pole-mounted circuit breaker 2 on the No. 3 pole tower cannot be controlled to open, the pole-mounted circuit breakers 2 on the No. 1 and No. 5 pole towers are controlled to open; if the pole-mounted circuit breaker 2 on the No. 5 pole tower cannot be controlled to open, the pole-mounted circuit breakers 2 on the No. 3 and No. 7 pole towers are controlled to open; if both the No. 3 and No. 5 pole towers cannot be opened, the pole-mounted circuit breakers 2 on the No. 1 and No. 7 pole towers are controlled to open, and so on.

[0086] S303: Calculate the frequency of single-phase grounding faults occurring in multiple lines based on the newly recorded fault line information of the single-phase grounding fault.

[0087] During implementation, each time after receiving fault line information, the system will recalculate and update the frequency of single-phase grounding faults on each line, so as to obtain the lines with higher frequencies of single-phase grounding faults, and further combine them with the time of fault occurrence to provide data reference for fault cause analysis. For example, in an area where the line passes through, animals migrate in a certain period of time, and there will be frequent single-phase grounding faults. Therefore, the area through which the line passes can be inspected in detail and corresponding response strategies can be formulated to reduce the probability of faults and improve power supply reliability.

[0088] And according to the frequency and specific time point of single-phase grounding faults, corresponding early prevention measures can be taken, such as guiding the migration or expelling the animals.

[0089] S304: Generate a priority line section for checking based on the frequency of single-phase grounding faults occurring in multiple lines and the recently normally operated pole-mounted circuit breaker 2 of the single-phase grounding fault line.

[0090] In implementation, based on the example of S301 and the expanded description in step S302, if a single-phase grounding fault occurs on tower No. 4 and the pole-mounted circuit breaker 2 on tower No. 3 cannot be opened, then the pole-mounted circuit breakers 2 on towers No. 1 and No. 5 are opened at this time, and according to the frequency of single-phase grounding faults, the intervals with a higher frequency of single-phase grounding faults are distinguished, that is, it is distinguished whether the fault is more likely to occur between towers No. 1 and No. 3, or between towers No. 3 and No. 5, so as to perform more targeted fault troubleshooting and improve the processing efficiency of fault troubleshooting and maintenance.

[0091] The embodiments of this specific implementation method are all preferred embodiments of the present application, and are not intended to limit the protection scope of the present application in turn. Therefore, all equivalent changes made based on the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A distributed ground fault line selection device, characterized in that: It includes an intelligent grounding mechanism (1), a pole-mounted circuit breaker (2), an intelligent feeder terminal (3), a zero-sequence current transformer and a preprocessor; The pole-mounted circuit breaker is used to control the closing and opening of the circuit. The zero-sequence current transformer is used to monitor the zero-sequence current value of the line; The preprocessor is used to collect the zero-sequence current value signal of the zero-sequence current transformer and send an alarm signal to the intelligent grounding mechanism (1) and the intelligent feeder terminal (3); The intelligent grounding mechanism (1) is capable of receiving the alarm signal and transferring the single-phase grounding fault current and determining the phase and line where the single-phase grounding fault is located; The intelligent feeder terminal (3) is capable of receiving the alarm signal and controlling the pole-mounted circuit breaker (2) to open.

2. A distributed ground fault line selection device according to claim 1, characterized in that: The intelligent grounding mechanism (1) comprises a controller, an arc extinguishing unit, a line selection unit and a current transformer (11); The arc extinguishing unit comprises a phase-splitting circuit breaker (12), the input end of the phase-splitting circuit breaker (12) is connected to a three-phase line, the phase-splitting circuit breaker (12) is provided with a switch 1 (121), a switch 2 (122) and a switch 3 (123) corresponding to the three-phase lines respectively, the arc extinguishing unit further comprises a switch 4 (124) and a current limiting resistor (125), the switch 4 (124) and the current limiting resistor (125) are connected in parallel with each other, one end of the current limiting resistor (125) is grounded, and the other end is connected to the output end of the phase-splitting circuit breaker (12); The line selection unit comprises a three-phase circuit breaker (13) and a grounding transformer (14) with impedance, wherein an input end of the three-phase circuit breaker (13) is connected to a three-phase line, one end of the grounding transformer (14) is grounded, and the other end of the grounding transformer (14) is connected to an output end of the three-phase switch; The controller is used to collect three-phase line voltage values, zero-sequence voltage values ​​and current values ​​flowing through a current-limiting resistor (125), and to control the closing and opening of the switch 1 (121), the switch 2 (122), the switch 3 (123), the switch 4 (124) and the three-phase circuit breaker (13); The current transformer one (11) is installed on the common grounding line of the current limiting resistor (125) and the switch four (124).

3. A distributed ground fault line selection device according to claim 2, characterized in that: The intelligent grounding mechanism (1) also includes a pre-circuit breaker (15), the input end of the pre-circuit breaker (15) is connected to the three-phase line, and the output end of the pre-circuit breaker (15) is connected to the phase-splitting circuit breaker (12) and the three-phase circuit breaker (13).

4. A distributed ground fault line selection device according to claim 2, characterized in that: A second current transformer (16) is installed on the output end line of the grounding transformer (14).

5. A distributed ground fault line selection device according to claim 2, characterized in that: The opening time of the pole-mounted circuit breaker (2) is consistent with the time when the fault line selection information of the intelligent grounding mechanism (1) is sent out.

6. A distributed ground fault line selection device according to claim 2, characterized in that: It also comprises a backup power supply (4), and the backup power supply (4) is used to provide backup power to the intelligent feeder terminal (3).

7. A distributed ground fault line selection method, based on the distributed ground fault line selection device according to any one of claims 1 to 6, characterized in that: The steps include: The preprocessor acquires abnormal current information of the zero-sequence current transformer in real time, and transmits the abnormal current information to the intelligent grounding mechanism (1) and the intelligent feeder terminal (3); The intelligent grounding mechanism (1) controls the switch closing of the phase circuit breaker (12) according to the abnormal current information; If the short-circuit fault disappears, the intelligent grounding mechanism (1) exits; if the fault still exists, the switch four (124) is closed; Closing the three-phase circuit breaker (13) and switching on the grounding transformer (14); Performing a disconnection process on the phase-splitting circuit breaker (12) and the switch four (124); According to the current fluctuation information of each zero-sequence current transformer, the line where the single-phase grounding fault is located is determined, the fault line information is generated, and reported to the system backend; The intelligent feeder terminal (3) controls the pole-mounted circuit breaker (2) of the line where the fault occurs to open.

8. A distributed ground fault line selection method according to claim 7, characterized in that: The intelligent grounding mechanism (1) controls the closing of the switch of the corresponding phase of the phase circuit breaker (12) according to the phase where the abnormal current information is located, including: According to the abnormal current information, the intelligent grounding mechanism (1) controls the switch of the corresponding phase of the phase circuit breaker (12) to close; Acquiring current information of the current transformer 1 (11), and analyzing whether the closing phase of the phase-splitting circuit breaker (12) is correct based on the current information of the current transformer 1 (11); If the closing is wrong, the wrong switch in the phase-splitting circuit breaker (12) is disconnected, and the switches of other phases are closed until the closing is correct.

9. A distributed ground fault line selection method according to claim 8, characterized in that: After generating the fault line information and reporting it to the system background, the following steps are also included: Record the serial numbers of several intelligent feeder terminals (3) closest to each other on both sides of the line where the single-phase grounding fault occurs; If the intelligent feeder terminal (3) closest to the line where the single-phase grounding fault is located cannot drive the corresponding pole-mounted circuit breaker (2), the pole-mounted circuit breaker (2) closest to the line where the fault is located and operating normally is opened; Based on the fault line information of the newly recorded single-phase grounding fault, the frequency of single-phase grounding faults occurring in multiple lines is calculated; Based on the frequency of single-phase grounding faults occurring in multiple lines and the recently normally operated pole-mounted circuit breakers (2) of the single-phase grounding fault lines, a priority line section is generated.

Images