An intelligent power transmission and cut-off system and method for downhole wiring

Abstract

This application relates to the field of mine electrical control technology, and in particular to an intelligent power outage and restoration system and method for underground overhead power lines. The system includes a host computer and an overhead power line control unit connected by communication, which work together to realize power outage and restoration control and status monitoring of underground overhead power lines. The host computer can view the energized status and operating current of the underground overhead power lines in real time, and remotely complete the opening and closing operations without the need for on-site personnel, improving the timeliness and convenience of operation. Furthermore, each section executes its own independent control logic, so a fault only affects that section and does not spread to other sections, achieving precise section control. Moreover, through the cooperation of a pre-charge contactor and a power resistor, the pre-charge contactor engages before the main contactor during closing, effectively preventing the main contactor contacts from sticking due to high current, extending the equipment's service life. In addition, a current transmitter monitors the main circuit current in real time; when a high current fault occurs, an alarm is automatically issued and the circuit is tripped, further ensuring operational safety.

Description

Technical Field

[0001] This application relates to the field of mine electrical control technology, and in particular to an intelligent power outage and restoration system and method for underground overhead power lines. Background Technology

[0002] Power outage and restoration in electric locomotive overhead contact lines refers to the operation of connecting (closing) or disconnecting (opening) power to the overhead contact network (referred to as "overhead line") on which electric locomotives rely for transportation, according to a specific "section" (such as a section of roadway or a transportation zone). Existing technical solutions for power outage and restoration in electric locomotive overhead contact lines are mainly based on traditional electrical control logic, and rely on "manual operation" or "overall power outage" at their core, and can be divided into two categories.

[0003] Option 1: Complete Power Outage of the Rectifier Cabinet. The power supply for the overhead power lines in the mine is provided by the rectifier cabinet (which converts AC power into DC power, such as DC 550V, required by the locomotive). This option achieves a complete power outage of the entire overhead power line system (all transport sections) by directly cutting off the output of the rectifier cabinet. The operation involves operators in the rectifier cabinet control room above or below ground manually turning off the rectifier cabinet switch or remotely controlling the rectifier cabinet to shut down, thus cutting off power to all overhead power line sections.

[0004] Option 2: On-site Intersection Tripping. Tripping devices (such as manual disconnect switches or simple contactors) are installed at key nodes in each overhead line section. When power needs to be cut off to a section, operators go to the tripping device in that section and manually operate the tripping device to cut off power only to the target section, while other sections maintain normal power supply. The operation involves the operator carrying tools down into the well, reaching the tripping point of the target section, and manually disconnecting the disconnect switch using a wrench or other tools, or pressing the local tripping button to cut off power to the section. To restore power, the operator must return to the site to reconnect the switch.

[0005] Option 1 involves a blanket power outage with no selectivity for specific sections. Disconnecting the rectifier cabinet would cut off power to all overhead lines relying on it, paralyzing the entire transportation system. Since underground transportation is a core part of production (such as transporting ore and materials), a complete power outage would directly interrupt the production process, resulting in significant wasted time. Option 2 relies heavily on manual labor and has low operational efficiency. Each power outage requires a dedicated person to operate underground, but underground tunnels are complex and can stretch for several kilometers. Upon receiving a power outage request, operators must travel to and from the target section, leading to delayed response and an inability to handle emergencies. Furthermore, dispatchers and operators cannot know in real time whether a section is de-energized, potentially leading to misjudgments such as "believing it's de-energized when it's actually still energized." Summary of the Invention

[0006] To overcome the shortcomings of the existing technology, this application provides an intelligent power outage and restoration system and method for underground power lines, which can improve the intelligence, safety and efficiency of power outage and restoration of underground power lines through dedicated deployment in one zone and one box, and remote and local dual operation.

[0007] In a first aspect, there is an intelligent power supply and shutdown system for underground power lines, including a host computer and a power line control unit. The host computer is communicatively connected to the power line control unit to collaboratively realize the power supply and shutdown control and status monitoring of underground power lines. The overhead line control unit includes a programmable logic controller, a main contactor, a pre-charge contactor, a power resistor, a current transmitter, an air switch, and a switching power supply; The digital input terminals of the programmable logic controller are connected to the closing button, the opening button, and the local / remote switching knob; its digital output terminals are connected to the closing indicator light, the opening indicator light, the main contactor, and the pre-charge contactor; and its analog input terminals are connected to the current transmitter. The main contactor is used to connect / disconnect the main circuit of the overhead line; the pre-charge contactor is connected in series with the power resistor and then in parallel across the two ends of the main contactor; the current transmitter is fitted onto the main circuit of the overhead line and is used to collect the operating current and feed it back to the programmable logic controller. The host computer is used to display the energized status and operating current of the overhead line in the section in real time, and to send remote opening and closing commands to the programmable logic controller.

[0008] In one possible implementation, the overhead line control unit is integrated into an outer casing, and the outer casing is installed one-to-one at the corresponding layout position of each overhead line control section underground, with each overhead line control section independently configured with one outer casing.

[0009] In one possible implementation, the outer casing is equipped with an electrical isolation plate to isolate the main overhead line circuit from the control circuit.

[0010] In one possible implementation, the digital output terminal of the programmable logic controller is connected to the closing indicator light, the opening indicator light, and the main contactor via relays.

[0011] In one possible implementation, the Ethernet interface of the programmable logic controller communicates with the host computer via network cable, switch, and optical fiber.

[0012] In one possible implementation, the overhead line control unit further includes an air switch and a switching power supply; the air switch is used to switch the AC380V input of the control circuit on / off; the switching power supply is connected to the air switch and is used to convert AC380V alternating current to DC24V direct current to power the programmable logic controller.

[0013] Secondly, this application provides a method for intelligent power outage and restoration of underground power lines, applied to any of the intelligent power outage and restoration systems for underground power lines described in the first aspect, the method comprising the following steps: The current transmitter collects the operating current of the main circuit of the underground overhead line in real time, converts it into a 4-20mA standard analog signal and feeds it back to the programmable logic controller (PLC). The PLC then uploads the signal to the host computer to display the energized status and operating current of the overhead line in the section in real time. When the programmable logic controller receives a remote tripping command from the host computer or a local tripping command from the tripping button, it controls the main contactor to trip, cuts off the main circuit of the overhead line, and the host computer updates the power outage status of the overhead line synchronously. When the programmable logic controller receives a remote closing command from the host computer or a local closing command from the closing button, it controls the main contactor to close, the main circuit of the overhead line is connected, and the host computer updates the energized status of the overhead line synchronously. Among them, when the main contactor closes, the pre-charge contactor engages before the main contactor, and the pre-charge contactor releases when the main contactor engages.

[0014] In one possible implementation, the method further includes the following steps: When the operating current of the main circuit of the overhead line exceeds the set threshold, the programmable logic controller determines it as an overcurrent fault, controls the main contactor to trip, and synchronously sends an audible and visual alarm to the host computer.

[0015] In one possible implementation, the method further includes the following steps: The programmable logic controller locks a unique operation access channel based on the status switching command received from the local / remote switching knob.

[0016] In one possible implementation, the method further includes the following steps: The programmable logic controller (PLC) blocks all closing commands based on the grounding tag interlock command received from the host computer.

[0017] This embodiment provides an intelligent power supply and shutdown system and method for underground power lines. The system allows real-time monitoring of parameters such as the energized status and operating current of the underground power lines via a host computer, enabling remote operation of opening and closing circuits without on-site personnel. This improves operational timeliness and convenience, and reduces labor costs. Furthermore, each section's independent control logic ensures that a fault only affects that section and does not spread to other sections, achieving precise section control. Specifically, the pre-charge contactor, in conjunction with a power resistor, engages before the main contactor during closing, effectively preventing the main contactor contacts from sticking due to high current and extending equipment lifespan.

[0018] In other embodiments, the main circuit current is monitored in real time by a current transmitter. When a large current fault occurs, an alarm is automatically issued and the circuit breaker is tripped, further ensuring operational safety. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This paper shows a schematic diagram of the structure of an intelligent power supply and shutdown system for underground power lines according to an embodiment of this application; Figure 2 A flowchart of an embodiment of the intelligent power outage and restoration method for underground power lines is shown. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. It should be understood that the accompanying drawings in this application are for illustrative and descriptive purposes only and are not intended to limit the scope of protection of this application. Furthermore, it should be understood that the schematic drawings are not drawn to scale. The flowcharts used in this application illustrate operations implemented according to some embodiments of this application. It should be understood that the operations in the flowcharts may not be implemented in sequence, and steps without logical contextual relationships may be reversed or implemented simultaneously. In addition, those skilled in the art, guided by the content of this application, may add one or more other operations to the flowcharts, or remove one or more operations from the flowcharts.

[0022] Furthermore, the described embodiments are merely some, not all, of the embodiments of this application. The components of the embodiments of this application described and illustrated herein can typically be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0023] It should be noted that the term "comprising" will be used in the embodiments of this application to indicate the presence of the features declared thereafter, but does not exclude the addition of other features.

[0024] In view of the technical problems raised in the background art, this application provides an intelligent power interruption and restoration system and method for underground power lines, which can improve the intelligence, safety and efficiency of power interruption and restoration of underground power lines through dedicated deployment of one box per area underground and remote and local dual operation.

[0025] In one embodiment, see the appendix to the specification. Figure 1 The present application provides an intelligent power supply and shutdown system for underground power lines, which mainly consists of a host computer and a power line control unit. The host computer and the power line control unit are communicatively connected to achieve power supply and shutdown control and status monitoring of underground power lines.

[0026] In this application, the integrated outer casing of the overhead line control unit is installed underground and connected to the main circuit of the corresponding overhead line section nearby. That is, each section is equipped with a complete overhead line control unit (integrated within the outer casing) to ensure that the control of each section does not interfere with each other (e.g., when inspecting section A, only the main contactor inside the outer casing of section A is disconnected, while other sections such as B and C are powered normally). Furthermore, it is connected to the host computer above ground via an independent communication link, allowing the host computer to individually identify and control the outer casing of each section, enabling parallel management of multiple sections. This achieves precise section control and remote intelligent operation.

[0027] Specifically, the overhead line control unit includes a programmable logic controller, a main contactor, a pre-charge contactor, a power resistor, a current transmitter, an air switch, and a switching power supply.

[0028] The air switch is used to control the on / off of the AC380V input power supply to power the control circuit; the switching power supply is connected to the air switch to convert AC380V AC power to DC24V DC power to power low-voltage components such as programmable logic controllers. The programmable logic controller (PLC) is the control core. Its digital input terminals are connected to the closing button, the opening button, and the local / remote switching knob. Its digital output terminals are connected to the closing indicator light, the opening indicator light, the coil of the main contactor, and the coil of the pre-charge contactor. Its analog input terminals are connected to the 4-20mA current signal output by the current transmitter. Its Ethernet interface communicates with the configuration software of the host computer through network cable, switch, and optical fiber to realize data interaction and command transmission.

[0029] The main contactor is used to connect / disconnect the main circuit of the overhead line; the pre-charge contactor is connected in series with the power resistor and then in parallel across the main contactor. The reason for adding the "pre-charge contactor + power resistor" pre-processing step in the closing logic of this application is that when closing the main circuit, the pre-charge contactor will be energized before the main contactor, and the capacitor pre-charge will be completed with a low current (current limited by the power resistor). After 200ms, the main contactor will be energized and the pre-charge contactor will be released, which can prevent the main contactor contacts from sticking due to the large current generated when the locomotive is in the pantograph raising and working state due to human negligence.

[0030] The reason this application abandons conventional wireless communication or ordinary network cables and adopts a combined link of network cable + switch + fiber optic cable is that fiber optic cable has the characteristics of being resistant to electromagnetic interference, having a long transmission distance (supporting transmission in tunnels of several kilometers), and being difficult to physically damage. It can penetrate underground tunnels and avoid the loss or distortion of commands caused by strong electromagnetic radiation generated by locomotives and frequency converters. In addition, an electrical isolation board is also installed in the integrated outer box of the overhead line control unit to isolate the main overhead line circuit from the control circuit, that is, to isolate the main contactor, pre-charge contactor and power resistor in the overhead line control unit, to prevent high-voltage electromagnetic interference from affecting the stability of remote control signals.

[0031] Preferably, the digital output terminal of the programmable logic controller (PLC) is connected to the closing indicator light, the opening indicator light, the coil of the main contactor, and the coil of the precharge contactor via relays. This is because the digital output terminal of the PLC itself is a low-voltage, weak-current output. Directly connecting it to actuators such as the closing indicator light, the opening indicator light, the main contactor coil, and the precharge contactor coil would make it susceptible to voltage fluctuations, electromagnetic interference, and reverse surge current impacts from the actuator side, thereby damaging the output port of the PLC. In the context of strong electromagnetic interference and frequent equipment start-ups and shutdowns in underground mines, the core function of the relay is to build an isolation bridge between the digital output terminal of the PLC and various actuators, while simultaneously ensuring reliable transmission of control signals.

[0032] The host computer includes configuration software and a mobile client, which are used to display the energized status of the overhead line in the section, the operating current of the overhead line section, provide remote tripping and closing operation interfaces and grounding tag interlocking functions, and can also receive fault alarm signals and feed them back to the user.

[0033] The following section will focus on explaining the workflow of the intelligent power outage and restoration system for underground power lines.

[0034] See the instruction manual appendix Figure 2 Based on the same inventive concept, this application also provides an intelligent power outage and restoration method for underground power lines, applicable to any of the aforementioned intelligent power outage and restoration systems for underground power lines. The method includes the following steps: S1. The current transmitter collects the operating current of the main circuit of the underground overhead line in real time, converts it into a 4-20mA standard analog signal and feeds it back to the programmable logic controller (PLC). The PLC then uploads the signal to the host computer to display the energized status and operating current of the overhead line in the section in real time. S2. When the programmable logic controller receives a remote tripping command from the host computer or a local tripping command from the tripping button, it controls the main contactor to trip, cuts off the main circuit of the overhead line, and the host computer updates the power outage status of the overhead line synchronously. S3. When the programmable logic controller receives a remote closing command from the host computer or a local closing command from the closing button, it controls the main contactor to close, the main circuit of the overhead line is connected, and the host computer updates the energized status of the overhead line synchronously. Among them, when the main contactor closes, the pre-charge contactor is engaged before the main contactor, and the pre-charge contactor is released when the main contactor is engaged.

[0035] Before performing the above steps, system initialization is required to provide a stable power supply to the entire system, establish a communication link, and complete the initial state calibration to ensure that the subsequent control logic can be executed normally.

[0036] Specifically, the operator (locally) manually closes the air switch inside the outer casing of the overhead line control unit, officially connecting the external AC380V industrial power supply to the control circuit of the overhead line control unit. The air switch, acting as the main power switch for the control circuit, has overload and short-circuit protection functions. If an abnormal current occurs in the subsequent circuit, it can automatically disconnect to prevent the power supply side fault from escalating. The switching power supply inside the overhead line control unit converts the connected AC380V AC power into a stable DC24V DC power supply to power low-voltage core components such as the programmable logic controller (PLC), resolving power mismatch issues. After receiving DC24V power, the PLC automatically powers on and starts, loading its internal control program (including communication protocol configuration). It connects to the downhole switch via its Ethernet interface and a network cable. The switch then establishes a physical connection with the network interface of the above-ground host computer via fiber optic cable (anti-interference, long-distance transmission). After the physical connection is established, the PLC and the host computer complete a handshake authentication through a preset communication protocol (such as ModbusTCP or Profinet), ultimately forming a stable bidirectional communication link.

[0037] In step S1, the main task is to perform status monitoring to address the shortcomings of existing technologies that cannot intuitively display the status.

[0038] Specifically, the current transmitter is connected in series at a key node of the main overhead line circuit (close to the power output or load input) to ensure that the actual operating current of the entire main circuit can be collected. The collected current signal is then converted into a 4-20mA standard analog signal and transmitted to the programmable logic controller (PLC). The PLC processes the signal (integrating it into a data packet containing the current value and energized status) and uploads it to the host computer via the established communication link for intuitive display on the configuration software interface or mobile client interface.

[0039] In step S2, the main task is to perform closing control, and to achieve a smooth connection of the main circuit of the overhead line while ensuring equipment safety (avoiding damage to the main contactor by large current).

[0040] Specifically, the programmable logic controller (PLC) identifies the received command and confirms whether it is a valid closing command (including remote closing commands and local closing commands). If it is a valid closing command, the PLC controls the pre-charge contactor to close. After the pre-charge contactor closes, its contacts connect to the power resistor. The current is limited by the power resistor, and the inverter capacitor is pre-charged with a low current. After the pre-charge contactor closes for 200ms (the PLC has a built-in delay module), the PLC controls the main contactor to close. At the same time as the main contactor closes, the pre-charge contactor releases. After the main contactor closes, the main circuit of the overhead line is officially connected, and the "closing indicator" in the local button indicator lights up, visually indicating to the underground operator that the closing is complete. The PLC also sends a closing completion signal to the host computer, which synchronously updates the overhead line energization status.

[0041] In step S3, the main task is to perform circuit breaker control to ensure that the main circuit of the overhead line is quickly and reliably disconnected in the event of normal power outage or sudden overcurrent fault, so as to avoid equipment damage or safety accidents.

[0042] Specifically, the programmable logic controller (PLC) monitors two types of signals (command signals and current data) in real time and determines whether to trigger the trip according to preset logic. The specific judgment rules are as follows: Valid trip command trigger (active operation type), including remote trip command (issued by the host computer) and local trip command (local trip button is pressed and the local / remote switching knob is in the "local" position); and overcurrent fault trigger (automatic protection type), which compares the real-time current of the main circuit uploaded by the current transmitter with the preset safety threshold (set according to the rated current of the overhead line and the load-bearing capacity of the equipment). If the real-time current is ≥ the preset threshold and the duration is ≥ 10ms (to avoid false triggering due to instantaneous fluctuations), it is determined to be an overcurrent fault and the trip is automatically triggered.

[0043] After the programmable logic controller (PLC) determines that the circuit breaker has been triggered, it immediately cuts off the DC24V control signal output to the main contactor coil. After the main contactor coil is de-energized, the power supply channel of the main overhead line circuit is directly cut off. The "Break Indicator" in the local button indicator lights up, visually indicating to the underground operator that the circuit breaker has been closed. At the same time, the PLC sends a closing completion signal back to the host computer, and the host computer updates the energized status of the overhead line synchronously.

[0044] When the circuit breaker trips due to a current reaching a preset threshold, the programmable logic controller (PLC) simultaneously triggers the overcurrent trip and sends an overcurrent fault trip signal to the host computer. This signal includes information such as the fault occurrence time, the peak current at the time of the fault, and the preset threshold. Upon receiving the signal, the host computer immediately activates an audible and visual alarm (e.g., a pop-up window on the interface or a buzzer sound) and displays "Overcurrent fault! Automatic tripping has been completed" in a prominent position on the interface, while simultaneously highlighting the fault current value in red. After receiving the fault alarm, the operator goes to the underground site or uses a remote monitoring system to troubleshoot the fault (e.g., checking for short circuits in the overhead lines, abnormal loads on the locomotive, or malfunctions in the current transmitter). After the fault is identified and resolved, the alarm is deactivated and the circuit is reset before the closing operation can be performed again.

[0045] This covers two scenarios: normal operation power outages and sudden fault protection. It not only meets the needs of human control, but also provides automatic protection during overcurrent, thus solving the shortcomings of existing technologies such as untimely power outages and lack of automatic overcurrent protection.

[0046] In addition, the host computer can also send grounding tag locking commands. Grounding tag locking commands are exclusive control commands under the strict safety compliance requirements of underground electrical operations in mines. They realize physical safety locking and operation permission locking after power outage in the overhead line section, preventing unauthorized personnel from accidentally closing the switch and causing electric shock to maintenance personnel. It is a more advanced safety protection command than simply opening the switch.

[0047] For example, when maintenance is required on a section of overhead power lines (such as overhead line maintenance or locomotive fault handling), the operator first issues a tripping command to cut off the power supply to that section, and then issues a grounding tag interlocking command to achieve dual safety protection. After receiving the grounding tag interlocking command from the host computer, the programmable logic controller (PLC) will execute both hardware and software interlocking actions, and the interlocking state is irreversible (manual unlocking is required). At the software level, the PLC directly blocks all closing commands for that section (including remote closing commands and local closing commands). Even if the operator accidentally presses the closing button or sends a remote closing command, it will be considered an "invalid command," refusing to execute any closing operation, thus preventing accidental closing from the control logic perspective. At the hardware level, if the overhead line control unit's outer casing integrates a dedicated underground grounding switch, the programmable logic controller (PLC) will output a control signal to drive the grounding switch to close, reliably connecting the main overhead line circuit to the underground grounding electrode. This releases residual induced voltage / static electricity from the overhead line, ensuring that maintenance personnel have no risk of electric shock when touching the line. In scenarios without an integrated grounding switch, operators must manually ground the line on-site and confirm "grounding complete" via the host computer / local button before the interlock is completed. After maintenance, operators remove the grounding device and warning sign on-site, then press the interlock release button via the host computer. The PLC verifies and clears the interlock state, restoring the closing function.

[0048] It should be noted that this application retains local operation buttons (closing, opening, fault reset). Remote control and local operation can be switched through a local / remote switching knob and identified by the programming logic controller. The power outage and restoration operation permissions of the overhead line section are uniquely locked, forming a dual operation channel of "remote as the main and local as the auxiliary".

[0049] Furthermore, this application implements "two-way status visualization," with the host computer displaying the energized status and current data of the section in real time. The underground control box is equipped with energized indicator lights and operation status indicator lights, which can be confirmed on-site by the operators. At the same time, a grounding tag interlocking function is added, which requires the interlocking to be released before remote closing to prevent others from accidentally closing the circuit remotely without their knowledge, thus solving the safety hazards of opaque status and lack of interlocking protection in conventional remote control.

[0050] As can be seen, the intelligent power outage and restoration system and method for underground power lines provided in this application, through dedicated underground deployment with one box per zone, and through remote and local dual operation channels and intelligent interlocking protection, accurately solves the pain points of traditional overall power outages affecting production and slow and high-risk on-site manual operation response. Furthermore, it is equipped with pre-charge protection and automatic overcurrent tripping logic, adapting to high-voltage and high-current conditions underground. Relay isolation and anti-interference communication links ensure stable equipment operation, while also achieving status visualization and operation traceability. This significantly improves the efficiency and accuracy of power outage and restoration operations, reduces labor costs, and comprehensively meets the high safety compliance requirements of mines from hardware to logic, adapting to the trend of automated and unmanned operation, ensuring underground power supply and operational safety while maximizing production efficiency.

[0051] Finally, it should be noted that the above embodiments are merely specific implementations of this application, used to illustrate the technical solutions of this application, and not to limit them. The protection scope of this application is not limited thereto. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features, within the scope of the technology disclosed in this application; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application. All should be covered within the protection scope of this application. Therefore, the protection scope of this application should be determined by the protection scope of the claims.

Claims

1. An intelligent power supply and shutdown system for underground power lines, characterized in that, It includes a host computer and a line-building control unit. The host computer is communicatively connected to the line-building control unit to collaboratively realize the power supply and shutdown control and status monitoring of the underground line-building. The overhead line control unit includes a programmable logic controller, a main contactor, a pre-charge contactor, a power resistor, a current transmitter, an air switch, and a switching power supply; The digital input terminals of the programmable logic controller are connected to the closing button, the opening button, and the local / remote switching knob; its digital output terminals are connected to the closing indicator light, the opening indicator light, the main contactor, and the pre-charge contactor; and its analog input terminals are connected to the current transmitter. The main contactor is used to connect / disconnect the main circuit of the overhead line; the pre-charge contactor is connected in series with the power resistor and then in parallel across the two ends of the main contactor; the current transmitter is fitted onto the main circuit of the overhead line and is used to collect the operating current and feed it back to the programmable logic controller. The host computer is used to display the energized status and operating current of the overhead line in the section in real time, and to send remote opening and closing commands to the programmable logic controller.

2. The intelligent power supply and shutdown system for underground power lines according to claim 1, characterized in that, The overhead line control unit is integrated into the outer box, and the outer box is installed one-to-one at the corresponding layout position of each overhead line control section underground. Each overhead line control section is independently configured with one outer box.

3. The intelligent power supply and shutdown system for underground power lines according to claim 2, characterized in that, The outer casing is equipped with an electrical isolation plate to isolate the main overhead line circuit from the control circuit.

4. The intelligent power supply and shutdown system for underground power lines according to claim 1, characterized in that, The digital output terminals of the programmable logic controller are connected to the closing indicator light, the opening indicator light, the main contactor, and the precharge contactor via relays.

5. The intelligent power supply and shutdown system for underground power lines according to claim 1, characterized in that, The Ethernet interface of the programmable logic controller communicates with the host computer via network cable, switch, and optical fiber.

6. The intelligent power supply and shutdown system for underground power lines according to claim 1, characterized in that, The overhead line control unit also includes an air switch and a switching power supply; the air switch is used to switch the AC380V input of the control circuit on / off; the switching power supply is connected to the air switch and is used to convert AC380V alternating current to DC24V direct current to power the programmable logic controller.

7. A method for intelligent power outage and restoration of underground power lines, characterized in that, The method, applied to any of the above-described intelligent power outage and restoration systems for underground power lines, includes the following steps: The current transmitter collects the operating current of the main circuit of the underground overhead line in real time, converts it into a 4-20mA standard analog signal and feeds it back to the programmable logic controller (PLC). The PLC then uploads the signal to the host computer to display the energized status and operating current of the overhead line in the section in real time. When the programmable logic controller receives a remote tripping command from the host computer or a local tripping command from the tripping button, it controls the main contactor to trip, cuts off the main circuit of the overhead line, and the host computer updates the power outage status of the overhead line synchronously. When the programmable logic controller receives a remote closing command from the host computer or a local closing command from the closing button, it controls the main contactor to close, the main circuit of the overhead line is connected, and the host computer updates the energized status of the overhead line synchronously. Among them, when the main contactor closes, the pre-charge contactor engages before the main contactor, and the pre-charge contactor releases when the main contactor engages.

8. The intelligent power supply and shutdown method for underground power lines according to claim 7, characterized in that, The method further includes the following steps: When the operating current of the main circuit of the overhead line exceeds the set threshold, the programmable logic controller determines it as an overcurrent fault, controls the main contactor to trip, and synchronously sends an audible and visual alarm to the host computer.

9. The intelligent power supply and shutdown method for underground power lines according to claim 7, characterized in that, The method further includes the following steps: The programmable logic controller locks a unique operation access channel based on the status switching command received from the local / remote switching knob.

10. The intelligent power supply and shutdown method for underground power lines according to claim 7, characterized in that, The method further includes the following steps: The programmable logic controller (PLC) blocks all closing commands based on the grounding tag interlock command received from the host computer.

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