A temperature and pressure prediction grading prevention and control system and method for internal arc fault of ring main unit

Abstract

The application discloses a temperature-pressure prediction grading prevention and control system and method for internal arc fault of ring network cabinet, and belongs to the technical field of safety protection of high-voltage switch equipment. The application deploys a multi-physical quantity sensor module in an arc risk compartment to collect pressure, temperature and arc light signals in real time; uses a temperature-pressure dynamic coupling prediction algorithm built in an edge computing unit to quickly predict the peak pressure of arc and evaluate the hazard level; starts a main suppression device according to the level, uses a super-fast action type fault current limiter to limit the fault current within 1ms for first-level suppression, and realizes rapid arc extinguishing by directional injection of CO2 insulation gas to the fault compartment for second-level suppression. The application realizes the transformation of arc fault from passive bearing to active prediction and grading suppression, can complete arc extinguishing within 5ms, significantly reduces the risk of cabinet explosion, is suitable for dry air and other environmentally friendly gas insulation ring network cabinets, and guarantees safe operation and reliable operation of equipment.

Description

Technical Field

[0001] This invention relates to the field of safety protection technology for high-voltage switchgear, specifically to a temperature and pressure prediction and classification prevention and control system and method for arc faults inside ring main units, applicable to the protection of internal arc faults in gas-insulated metal-enclosed switchgear such as ring main units and gas-filled switchgear. Background Technology

[0002] Internal arcing faults are the most serious type of fault in ring main units. They are usually caused by insulation breakdown, misoperation, overvoltage, etc. When an arcing fault occurs inside the ring main unit, the huge energy released instantaneously causes the arc temperature to reach 10,000 to 20,000°C. At the same time, the gas in the compartment is rapidly heated and expanded, which can generate a high-voltage shock wave of several MPa within milliseconds.

[0003] Existing internal arc protection technologies mainly fall into two categories: passive pressure relief channels and arc fault detection and protection. (1) Passive pressure relief technology: A pressure relief cover is installed on the top or rear of the ring main unit. When the internal pressure exceeds the set threshold, the cover will automatically open to release high-temperature and high-pressure gas. However, this method is a "locking the stable door after the horse has bolted" type of protection, which cannot stop the development and destruction of the arc, but can only guide the destructive effect in a safe direction; In the internal arc test specified in GB / T 3906-2020 standard, qualified products are only required to prevent the cabinet from cracking and the indicator from being ignited, but the equipment inside the cabinet is often severely damaged.

[0004] (2) Arc fault detection and protection technology: By detecting arc light or overcurrent signals, the circuit breaker is triggered to trip, cutting off the source of arc energy; However, the full breaking time of traditional circuit breakers is usually 40 to 60 ms, while internal arcing can cause irreversible damage to the cabinet within 10 ms. At this time, even if a fast circuit breaker is used, its inherent mechanical action delay is difficult to meet the requirements for early arc suppression.

[0005] In summary, the core deficiency of existing technologies is the lack of real-time prediction capability for arc development, making it impossible to achieve early active suppression in the early stages of arc development (e.g., within 5ms).

[0006] To address these issues, this invention proposes a temperature and pressure prediction and classification prevention and control system and method for arcing faults inside ring main units, in order to solve the aforementioned technical problems. Summary of the Invention

[0007] The main objective of this invention is to provide a temperature and pressure prediction and graded prevention and control system and method for arcing faults inside ring main units, which solves the technical problems mentioned in the background art of the inability of existing technologies to predict arcing development in real time and the lack of active intervention capabilities, and realizes early prediction and graded suppression of internal arcing faults.

[0008] To address the problems of existing technologies being unable to predict arc development in real time and lacking proactive intervention capabilities, this invention employs the following technical solution to resolve the aforementioned technical issues: On one hand, this invention discloses a temperature and pressure prediction and hierarchical prevention and control system for arcing faults inside a ring main unit. By deploying multiple physical quantity sensors to monitor the pressure, temperature, and arc light signal of each compartment of the ring main unit in real time, a temperature and pressure dynamic coupling prediction model based on energy conservation and the gas state equation is constructed to predict the peak pressure during the arcing process in real time. When the predicted pressure exceeds the threshold that the cabinet can withstand, an ultra-fast action fault current limiter is activated in stages to cut off the arc energy input, and CO2 is injected into the fault area for cooling and arc extinguishing. The amount of gas injected is adaptively calculated based on the predicted peak pressure.

[0009] Furthermore, the temperature and pressure prediction and hierarchical prevention and control system for arcing faults inside the ring main unit specifically includes: Multi-physical quantity sensor modules are deployed in the gas box and cable compartment of the ring main unit. These two compartments are core compartments where arcing faults may occur, and each is independently configured with a sensor module. The multi-physical quantity sensor modules are used to monitor changes in gas temperature within the compartments, quickly trigger identification after an arcing event occurs, and capture the pressure rise process during the instant of arcing in real time. Since there are no high-voltage live components in the secondary control room, arcing faults do not occur inside, so no arcing monitoring sensors are deployed there; only an edge computing unit is deployed. The multi-physical quantity sensor modules are communicatively connected to the edge computing unit, transmitting the data they acquire to the edge computing unit. The sampling of each sensor is synchronized, and the timestamp accuracy is better than 0.1ms. The edge computing unit, deployed in the secondary control room of the ring network cabinet, includes a data acquisition module, a storage module, and a high-speed computing module. It has a built-in temperature and pressure dynamic coupling prediction algorithm based on energy conservation and the gas state equation. It is used to receive sensor transmission data from the multi-physical quantity sensor module in real time, predict the arc development process, and complete the arc hazard level assessment. The edge computing unit is controlled and connected to the active suppression device to send graded suppression commands according to the prediction results. An active suppression device is used to quickly limit the fault current amplitude and instantaneously spray insulating gas to suppress the arc spread during the initial stages of short-circuit faults and internal arcing faults in ring main units. This rapidly extinguishes the fault arc and isolates the fault energy, thereby reducing the safety risks of equipment burnout, cabinet deformation and cracking, and electric shock and burns to maintenance personnel. The active suppression device includes a common CO2 high-pressure gas storage tank deployed on the top of the ring main unit and an ultra-fast-acting fault current limiter installed on the power supply side of the ring main unit (i.e., the end closest to the power supply; for incoming line cabinets, it is the incoming line side; for outgoing line cabinets, it is the busbar side), connected in series in the main circuit.

[0010] Preferably, the multi-physical quantity sensor module is independently configured in each compartment (gas box and cable compartment) where arcing may occur, including: A fast-response pressure sensor with a range of 0–5 MPa (absolute pressure), a response time of <0.1 ms, and a sampling frequency of not less than 100 kHz is used to capture the pressure rise process during the instant of arcing in real time. Thermocouple sensor: range set to -40℃~+500℃, response time <10ms, used to monitor changes in gas temperature in a compartment; Arc light sensor: It adopts ultraviolet / visible dual-spectrum detection with a response time of <1ms, and is used to quickly trigger and identify arcing events occurring inside the cabinet. Preferably, the active suppression device includes: The ultra-fast-acting fault current limiter is installed on the power supply side of the ring main unit (closest to the power source), connected in series in the main circuit, and employs solid-state switching or fast mechanical disconnection technology. Its action time is <1ms, and it is used to reduce the fault current from its peak value during the initial stage of arcing. Limit to safe value the following; The insulating gas injection device includes a common CO2 high-pressure storage tank installed on the top of the ring main unit, as well as branch pipelines and independent solenoid valves leading to the gas box and cable compartment respectively; the CO2 is used as the injection medium and is injected into the compartment where the arc occurs as needed by the solenoid valve. After injection, the gas can be quickly discharged through the pressure relief channel without affecting the main insulation performance; the main insulation medium in the gas box is set as dry air.

[0011] On the other hand, this invention also discloses a temperature and pressure prediction and hierarchical prevention method for arcing faults inside a ring main unit, implemented based on the aforementioned temperature and pressure prediction and hierarchical prevention system for arcing faults inside a ring main unit, comprising: Step S1. Real-time monitoring: Continuously collect real-time pressure data inside the gas box and cable compartment. ,temperature He Guangqiang The signal, in which sampling is synchronized across all sensors, has a timestamp accuracy better than 0.1ms; Step S2. Arc Trigger Detection: Determine whether an arc occurs inside the cabinet by using ultraviolet / visible dual-spectrum detection and current changes. Step S3. Dynamic Prediction of Arc Development: The temperature and pressure dynamic coupling prediction model is activated through the edge computing unit to output the real-time arc parameters inside the cabinet, thereby constructing the real-time pressure inside the compartment. The coupling differential relationship between the arc energy injection rate and the pressure relief and exhaust rate; Step S4. Hazard Level Assessment: The coupled prediction model uses the fourth-order Runge-Kutta method to numerically solve the coupled differential relationship between the internal pressure of the compartment and the arc energy injection rate and the pressure relief and exhaust rate, in order to predict the future. Within milliseconds ( Take 5ms, for example, from the moment the arc occurs. arrive The pressure change curve (+5ms) is used to extract the predicted peak pressure. And based on the preset level determination rules, the arc hazard level is assessed; Step S5. Graded Active Suppression: Actively suppress arcing inside the cabinet in stages. Step S6. System Recovery and Daily Monitoring: After the arc is suppressed, the system records specified data including the fault time, peak pressure, and action sequence, and issues an alarm signal, waiting for maintenance personnel to troubleshoot the fault and reset the system. In addition, during the daily operation of the system, if no arc event occurs, the edge computing unit is in standby monitoring state, only continuously collecting sensor data, and does not execute the prediction and suppression process.

[0012] Preferably, the specific criterion for determining whether an arc occurs inside the cabinet in step S2 is as follows: An arcing event is determined to have occurred when any of the following conditions are met: Condition A: The output of the arc light sensor exceeds the threshold. (Typical value: 500 μW / cm) 2 ); Condition B: Rate of change of current and voltage sag rate All exceeded the corresponding threshold, including: current change rate Exceeding the corresponding threshold of 10 A / μs, and the voltage descent rate Exceeding another corresponding threshold of 1kV / ms; After triggering, record the moment of arcing. and collect Initial pressure at any moment Initial temperature of the cabinet's internal environment , which serves as the initial input value for the prediction model in step S3.

[0013] Preferably, the real-time pressure inside the model compartment in step S3 The coupling differential relationship between the arc energy injection rate and the pressure relief and exhaust rate is as follows:

[0014] in, The adiabatic index of the gas in the compartment is 1.40 for dry air in the gas box and 1.30 for the injected medium CO2. Initial free volume of the compartment where the arcing failure occurred (unit: m³) 3 ), Effective pressure relief area of ​​the pressure relief channel (unit: m²) 2 ), The flow coefficient of the pressure relief port ranges from 0.5 to 0.7. The initial gas density in the compartment (unit: kg / m³) 3 ), Environmental absolute pressure (unit: Pa). The instantaneous power of the electric arc (unit: W) is and the electric arc voltage is . and arc current The product determines that, i.e.: The above pressure relief term is derived based on the isentropic flow assumption and the simplified derivation of the nozzle flow rate formula, and has good engineering approximation accuracy under the initial small-hole discharge condition of pressure relief.

[0015] Preferably, the arc voltage Arc length and arc current The function, described using the improved Cassie-Mayr mixture model, is expressed as:

[0016] in, , , Arc characteristic parameters (calibrated experimentally, typical values:) =15V / cm, =2.5V / cm, =8V / cm), The reference current is 1kA. The time constant is 0.5 ms. The term is used to simulate the dynamic overshoot process in the initial stage of arc breakdown, while the ln term is used to describe the voltage characteristics in the steady-state arcing stage, wherein the arc length... Based on sensor location and fault point experience values, the shortest distance between two phase conductors is selected during a three-phase short circuit.

[0017] Preferably, the specific assessment process for assessing the arc hazard level based on preset level determination rules in step S4 includes: The safe pressure withstand threshold of the cabinet is calibrated through type testing. (Typical value is rated pressure + 50% margin), for threshold : like If so, it is determined to be a low-risk arcing event, and only an alarm is recorded; like If so, it is determined to be a medium-risk arc ignition, triggering the first level of suppression; like If it is determined to be a high-risk arcing event, it will trigger both the first and second level of suppression.

[0018] After implementing the first level of current limiting suppression, the edge computing unit will continuously monitor the rate of pressure change; if in Δt The pressure is expected to continue rising rapidly over the next period, and the peak is predicted to exceed [a certain value]. If this occurs, the second stage of injection suppression is immediately triggered, forming a closed-loop adaptive control.

[0019] Preferably, the specific operational procedure for actively suppressing arcing inside the cabinet in step S5 includes: Step S51. First-stage current limiting suppression: Trigger the ultra-fast fault current limiter, in The fault current will be reduced from its peak value within ≤1ms. Limit to safe value Cut off the arc energy at the source (to a current of 2-3 times or less than the rated current); Step S52. Second-stage injection arc extinguishing suppression: Simultaneously (only activated in high-risk situations), the insulating gas injection device is activated, and the solenoid valve of the corresponding arc-ignition compartment is opened, allowing CO2 from the common high-pressure CO2 storage tank at the top of the ring main unit to be injected into the fault area through branch pipelines, achieving the following dual effects: Lowering the arc temperature: Low-temperature gas exchanges heat with the high-temperature arc, reducing the arc conductivity; Improve the recovery strength of the medium: the jet gas blows through the arc channel, accelerating arc cooling and deionization effect; Total injection volume (Unit: standard liter) Based on the predicted peak pressure of the highest-risk compartment The deviation from the safety threshold is adaptively calculated using the following formula:

[0020] This formula is only applicable to high-risk arc-ignition scenarios. ≥ At this point, the calculation result is positive, representing the amount of gas that needs to be injected additionally to suppress the risk of overpressure. Among these, This is an empirical proportionality coefficient, ranging from 0.5 to 1.5, calibrated through arcing tests. The gas constant of the injected gas CO2 ( =189J / (kg·K)), The initial free volume of the compartment where the arcing failure occurred, and the initial temperature of the internal environment of the cabinet. (Unit: K) The system pre-charges the gas storage tank to absolute pressure (unit: Pa). Based on the calculation results, the system controls the total release of the common gas cylinder and distributes it to the corresponding compartments through valves.

[0021] If no arcing occurs during the above steps, the edge computing unit remains in standby monitoring mode, continuously collecting sensor data without starting the temperature and pressure dynamic coupling prediction model and subsequent processes.

[0022] In another aspect, the present invention also discloses a computer-readable storage medium storing a computer program, which, when executed by a processor, causes the processor to perform the steps of the method described above.

[0023] In another aspect, the present invention also discloses a computer device, including a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor performs the steps of the method described above.

[0024] As can be seen from the above technical solution, the present invention provides a temperature and pressure prediction and classification prevention and control system and method for arcing faults inside a ring main unit. Compared with the prior art, the present invention has the following advantages: 1. This invention enables real-time prediction of the internal arcing development process by constructing a temperature-pressure dynamic coupling model based on physical mechanisms.

[0025] 2. This invention performs a graded suppression operation. The first stage limits the current to cut off the arc supply from the energy source, and the second stage sprays the arc extinguishing jet to accelerate the extinction of the generated arc. This can maximize the reduction of action loss while ensuring safety.

[0026] 3. This invention adaptively calculates the injection volume of the injected gas based on the deviation between the predicted peak pressure and the safety threshold, thereby achieving adaptive matching between the injection volume and the severity of arcing, rapidly and quantitatively calculating the gas injection volume, and avoiding gas waste or insufficient suppression.

[0027] 4. This invention enables a shift from passively accepting arcing faults inside the cabinet to actively predicting and suppressing them in stages, effectively reducing the destructive impact of arcing faults on the cabinet and ensuring the safety of maintenance personnel.

[0028] It should be understood that the descriptions in this section are not intended to identify key or essential features of embodiments of the invention, nor are they intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Of course, implementing any product of the invention does not necessarily require achieving all of the advantages described above simultaneously. Attached Figure Description

[0029] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the temperature and pressure prediction and hierarchical control system architecture of the present invention; Figure 2 This is a schematic diagram showing the deployment of the multi-physical quantity sensor and active suppression device of the present invention; Figure 3 This is a schematic diagram of the temperature and pressure prediction and graded control method of the present invention; Figure 4 This is a curve showing the comparison between the predicted and actual pressure values ​​of the temperature-pressure coupling model of this invention. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] For details in the embodiments, please refer to Figures 1 to 4 .

[0032] like Figure 1 and Figure 2 As shown. The temperature and pressure prediction and hierarchical prevention and control system for arcing faults inside ring main units proposed in this embodiment of the invention includes: (1) Multi-physical quantity sensor modules are deployed in the gas box and cable compartment of the ring main unit. These two compartments are core compartments where arcing faults may occur, and sensor modules are configured independently in each compartment. Since there are no high-voltage live parts in the secondary control room, arcing faults do not occur inside. Therefore, only edge computing units are deployed in the secondary control room, and no arcing monitoring sensors are deployed. The multi-physical quantity sensor modules are communicatively connected to the edge computing units and transmit the data they acquire to the edge computing units. The sampling of each sensor is synchronized, and the timestamp accuracy is better than 0.1ms.

[0033] The multi-physical quantity sensor module is independently configured in the air box and cable chamber, respectively, including: (1a) A fast-response pressure sensor with a range of 0 to 5 MPa (absolute pressure), a response time of <0.1 ms, and a sampling frequency of not less than 100 kHz, is used to capture the pressure rise process during the instant of arcing in real time. (1b) Thermocouple sensor: The range is set to -40℃ to +500℃, and the response time is <10ms. It is used to monitor the temperature change of the gas in the compartment. (1c) Arc light sensor: It adopts ultraviolet / visible dual-spectrum detection with a response time of <1ms, and is used to quickly trigger and identify arc events that occur inside the cabinet.

[0034] The sensors acquire data and then transmit it to the edge computing unit.

[0035] (2) Edge computing unit, deployed in the secondary control room of the ring network cabinet, includes a data acquisition module, a storage module and a high-speed computing module, and has a built-in temperature and pressure dynamic coupling prediction algorithm based on energy conservation and gas state equation, which is used to receive sensor transmission data from the multi-physical quantity sensor module in real time and predict the arc development process; the edge computing unit is controlled and connected to the active suppression device, which is used to send suppression commands according to the prediction results.

[0036] (3) An active suppression device is used to quickly limit the amplitude of the fault current and instantaneously spray insulating gas to suppress the spread of the arc during the initial stage of a short circuit fault or internal arcing fault in the ring main unit, thereby quickly extinguishing the fault arc and isolating the fault energy, reducing the safety risks of equipment burnout, cabinet deformation and cracking, and electric shock and burns to maintenance personnel. The active suppression device includes a common CO2 high-pressure gas storage tank, deployed on the top of the ring main unit, and an ultra-fast action fault current limiter, installed on the power supply side of the ring main unit (i.e., the end closest to the power supply, the incoming side for incoming line cabinets and the busbar side for outgoing line cabinets), connected in series in the main circuit.

[0037] The active suppression device includes: (3a) Ultra-fast action type fault current limiter, installed on the power supply side of the ring main unit (closest to the power supply end), connected in series in the main circuit, and adopts solid-state switch or fast mechanical disconnection technology, with an action time of <1ms, used to reduce the fault current from the peak value in the early stage of arcing. Limit to safe value the following; (3b) An insulating gas injection device includes a common CO2 high-pressure gas storage tank (geometric volume 5L) installed on the top of the ring main unit, as well as branch pipelines and independent solenoid valves leading to the gas box and the cable compartment respectively; the CO2 is used as the injection medium and is injected into the compartment where the arc occurs as needed by the solenoid valve. After injection, the gas can be quickly discharged through the pressure relief channel without affecting the main insulation performance; the main insulation medium in the gas box is set as dry air.

[0038] On the other hand, such as Figure 3 As shown, this invention also discloses a temperature and pressure prediction and hierarchical prevention method for arcing faults inside a ring main unit, which is implemented based on the temperature and pressure prediction and hierarchical prevention system for arcing faults inside a ring main unit in the above embodiments. Data processing is implemented based on the data acquisition module, storage module, and high-speed computing module of the edge computing unit, including: Step S1. Real-time monitoring: Continuously collect real-time pressure data inside the gas box and cable compartment using a multi-physical quantity sensor module. ,temperature He Guangqiang The signal is sampled synchronously by all sensors, with a timestamp accuracy better than 0.1ms.

[0039] Step S2. Arc Trigger Detection: The presence of an arc within the cabinet is determined by ultraviolet / visible dual-spectrum detection and current changes. The specific criteria for determination are as follows: An arcing event is determined to have occurred when any of the following conditions are met: Condition A: The output of the arc light sensor exceeds the threshold. (Typical value: 500 μW / cm) 2 ); Condition B: Rate of change of current and voltage sag rate All exceeded the corresponding threshold, including: current change rate Exceeding the corresponding threshold of 10 A / μs, and the voltage descent rate Exceeding another corresponding threshold of 1kV / ms; After triggering, record the moment of arcing. and collect Initial pressure at any moment Initial temperature of the cabinet's internal environment , which serves as the initial input value for the prediction model in step S3.

[0040] Step S3. Dynamic Prediction of Arc Development: The temperature and pressure dynamic coupling prediction model is activated through the edge computing unit to output the real-time arc parameters inside the cabinet, thereby constructing the real-time pressure inside the compartment. The coupling differential relationship between the arc energy injection rate and the pressure relief and exhaust rate.

[0041] At this time, the real-time pressure inside the model compartment The coupling differential relationship between the arc energy injection rate and the pressure relief and exhaust rate is as follows:

[0042] in, The adiabatic index of the gas in the compartment is 1.40 for dry air in the gas box and 1.30 for the injected medium CO2. Initial free volume of the compartment where the arcing failure occurred (unit: m³) 3 ), Effective pressure relief area of ​​the pressure relief channel (unit: m²) 2 ), The flow coefficient of the pressure relief port ranges from 0.5 to 0.7. The initial gas density in the compartment (unit: kg / m³) 3 ), Environmental absolute pressure (unit: Pa). The instantaneous power of the electric arc (unit: W) is and the electric arc voltage is . and arc current The product determines that, i.e.: The above pressure relief term is derived based on the isentropic flow assumption and the simplified derivation of the nozzle flow rate formula, and has good engineering approximation accuracy under the initial small-hole discharge condition of pressure relief.

[0043] Arc voltage here Arc length and arc current The function, described using the improved Cassie-Mayr mixture model, is expressed as:

[0044] in, , , Arc characteristic parameters (calibrated experimentally, typical values:) =15V / cm, =2.5V / cm, =8V / cm), The reference current is 1kA. The time constant is 0.5 ms. The term is used to simulate the dynamic overshoot process in the early stage of arc breakdown, while the ln term describes the voltage characteristics during the steady-state arcing stage, and the arc length. Based on sensor location and fault point experience values, the shortest distance between two phase conductors is selected during a three-phase short circuit.

[0045] Step S4. The coupled prediction model uses the fourth-order Runge-Kutta method to numerically solve the coupled differential relationship between the internal pressure of the compartment and the arc energy injection rate and the pressure relief and exhaust rate, in order to predict the future. Within milliseconds ( Take 5ms, for example, from the moment the arc occurs. arrive The pressure change curve (+5ms) is used to extract the predicted peak pressure. And based on the preset level determination rules, the arc hazard level is assessed.

[0046] Furthermore, the specific assessment process for evaluating the hazard level of arcing based on preset level determination rules includes: The safe pressure withstand threshold of the cabinet is calibrated through type testing. (Typical value is rated pressure + 50% margin), for threshold : like If so, it is determined to be a low-risk arcing event, and only an alarm is recorded; like If so, it is determined to be a medium-risk arc ignition, triggering the first level of suppression; like If it is determined to be a high-risk arcing event, it will trigger both the first and second level of suppression.

[0047] Step S5. Actively suppress arcing inside the cabinet in stages using an active suppression device. The specific operation process includes: Step S51. First-stage current limiting suppression: Trigger the ultra-fast fault current limiter, in The fault current will be reduced from its peak value within ≤1ms. Limit to safe value Cut off the arc energy at the source (to a current of 2-3 times or less than the rated current); Step S52. Second-stage injection arc extinguishing suppression: Simultaneously (only activated in high-risk situations), the insulating gas injection device is activated, and the solenoid valve of the corresponding arc-ignition compartment is opened, allowing CO2 from the common high-pressure CO2 storage tank at the top of the ring main unit to be injected into the fault area through branch pipelines, achieving the following dual effects: Lowering the arc temperature: Low-temperature gas exchanges heat with the high-temperature arc, reducing the arc conductivity; Improve the recovery strength of the medium: the jet gas blows through the arc channel, accelerating arc cooling and deionization effect; Total injection volume (Unit: standard liter) Based on the predicted peak pressure of the highest-risk compartment The deviation from the safety threshold is adaptively calculated using the following formula:

[0048] This formula is only applicable to high-risk arc-ignition scenarios. ≥ At this point, the calculation result is positive, representing the amount of gas that needs to be injected additionally to suppress the risk of overpressure. Among these, This is an empirical proportionality coefficient, ranging from 0.5 to 1.5, calibrated through arcing tests. Let CO2 be the gas constant of the injected gas. V 0 represents the initial free volume of the compartment where the arcing failure occurred, and the initial temperature of the internal environment of the cabinet. (Unit: K) The system pre-charges the gas storage tank to absolute pressure (unit: Pa). Based on the calculation results, the system controls the total release of the common gas cylinder and distributes it to the corresponding compartments through valves.

[0049] Step S6. System Recovery and Daily Monitoring: After the arc is suppressed, the system records specified data including the fault time, peak pressure, and action sequence, and issues an alarm signal, waiting for maintenance personnel to troubleshoot the fault and reset the system. In addition, during the daily operation of the system, if no arc event occurs, the edge computing unit is in standby monitoring state, only continuously collecting sensor data, and does not execute the prediction and suppression process.

[0050] In summary, a set of environmentally friendly gas-insulated ring main units was used for testing and demonstration during the specific implementation process.

[0051] The system uses dry air as the primary insulating medium, with a global warming potential (GWP) of 0, completely replacing traditional SF6 gas. The gas tank is a fully sealed design, filled with dry air (volume fraction: approximately 78% N2 + 21% O2 + 1% other components, moisture content ≤150ppm), and the rated filling pressure is set at 0.15MPa (relative pressure, i.e., absolute pressure 0.251MPa). The ring main unit cabinet adopts a vertically layered structure: the top is the secondary control room, the middle is the gas tank, and the bottom is the cable compartment. This embodiment uses the incoming line cabinet as an example, but for the outgoing line cabinet, the fault current limiter is also installed on the power supply side (busbar side) inside the cabinet, and the technical solution is fully applicable.

[0052] In this embodiment, inside the air box (volume) V 0 = 0.15m 3 (The air chamber is filled with dry air to an absolute pressure of 0.251 MPa). Install one piezoresistive fast-response pressure sensor (range 0-1.0MPa absolute pressure, response time <0.05ms) in the middle of the rear wall of the compartment to capture the pressure rise at the moment of arcing in real time. Install one K-type thermocouple (1mm in diameter, 8ms response time) at the top of the compartment to monitor changes in gas temperature; Install one fiber optic arc sensor (response time < 0.5ms) near the circuit breaker contacts, directly opposite the gap between the three-phase moving and stationary contacts, for rapid triggering and identification of arcing events.

[0053] In the cable room (volume) V 0 = 0.12m 3 In an atmospheric pressure air environment, one pressure sensor, one thermocouple, and one arc light sensor are also installed, located in the middle of the rear wall of the cable compartment, the top, and near the cable joint, respectively.

[0054] Only edge computing units are installed in the secondary control room; no sensors or spray devices are installed.

[0055] In this embodiment, the ultrafast fault current limiter adopts a scheme based on bridge solid-state switch series current-limiting reactor, with a rated voltage of 12kV, a rated current of 630A, and an action time of 0.8ms. It is installed on the power supply side of the ring main unit (in this embodiment, it is the incoming line unit, so it is installed on the incoming line side) and connected in series in the main circuit. In this embodiment, an insulating gas injection device is also constructed: a common CO2 high-pressure storage tank with a geometric volume of 5L is installed on the top of the ring main unit. The pressure conversion rule is: absolute pressure = relative pressure + standard atmospheric pressure, where standard atmospheric pressure is approximately taken as 0.101MPa. CO2 is pre-charged to 12MPa (relative pressure, i.e., absolute pressure 12.101MPa). The outlet of the storage tank is connected to two branch pipelines, leading to the gas tank and cable compartment respectively. Each pipeline is equipped with an independent solenoid valve, with a nozzle diameter of 10mm and a solenoid valve actuation time of 1.2ms. The injection direction in the gas tank is designed to cover the three-phase contact area and the arc, while the injection direction in the cable compartment covers the cable joint area.

[0056] According to the test method specified in Appendix B of GB / T 3906-2020, the three-phase conductors of the gas box are connected by a copper wire with a diameter of 0.5 mm as the arc ignition point.

[0057] The test circuit parameters are set as follows: applied voltage 12kV (rated voltage), expected short-circuit current 20kA (RMS), duration 1s.

[0058] It should be noted that the insulation strength and arc-extinguishing capacity of dry air are lower than those of SF6. Therefore, under the same parameters, the thermal and pressure effects of internal arcing faults are more significant in a dry air environment, which places higher demands on the protection system.

[0059] In addition, the key physical properties of dry air and CO2 were calibrated before the arc test: (1) Parameters of dry air in the gas box: adiabatic index γ=1.40, gas constant Initial inflation density ; (2) Parameters of the injection medium CO2: adiabatic index =1.30 (due to the polyatomic molecular characteristics of CO2) (lower), gas constant The critical temperature is 304K. It is easily liquefied at room temperature and stored in liquid form in the gas storage tank. When it is injected, it rapidly vaporizes and absorbs heat. (3) Arc characteristic parameters (calibrated through small current pre-test in dry air environment): =18V / cm, =3.0V / cm, =10V / cm.

[0060] The post-processing data from the arc test are as follows: Approximately 4.8 ms after the test circuit was closed, the arc light sensor output jumped from 0 Lux to 135 Lux (exceeding the threshold). ), while the rate of change of current Reaching 18 A / μs, the system detected and recorded the arcing event within 0.2 ms. At that moment, the prediction model is activated: exist At any given moment, the initial absolute pressure is collected. initial temperature The initial free volume of the compartment where the arcing failure occurred Effective pressure relief area (Equivalent area of ​​a tiny gap before the pressure relief channel is opened), flow coefficient The adiabatic index of the dry air inside the gas box .

[0061] Arc current Calculated based on expected short-circuit current parameters (RMS 20kA, peak approximately 50.4kA). Arc length is taken as the shortest distance between the three phase conductors. Substitute the dry air arc characteristic parameters , , Using the improved Cassie-Mayr hybrid model, we have:

[0062] The calculated arc voltage at the initial stage of arcing is approximately 380V, and the instantaneous power is... .

[0063] The above parameters are numerically solved using the fourth-order Runge-Kutta method to predict the pressure rise curve within the next 10 ms. Figure 4 The comparison between the model-predicted pressure curve and the measured pressure curve is shown, and the results indicate that the model-predicted peak pressure is accurate. (Absolute pressure), measured peak value The prediction error is less than 8%. The predicted time when the pressure reaches 0.35 MPa (design withstand threshold) is... +2.6ms, actual measurement is +2.9ms, with a time error of less than 0.5ms, verifying the accuracy of the model in dry air medium.

[0064] By constructing a temperature-pressure dynamic coupling model based on physical mechanisms, this invention enables real-time prediction of the internal arcing process. Compared with existing solutions that only passively release pressure after the pressure reaches a threshold, this invention can predict the peak pressure 5-10ms in advance, thus gaining valuable time for proactive intervention.

[0065] At this point, the design of the gas box of the environmental protection ring network cabinet is subjected to absolute pressure. (Relative pressure approximately 0.25 MPa), perform hazard level assessment, model prediction. If the arc is classified as high-risk, the following first-level and second-level suppression must be triggered simultaneously: Level 1 suppression (current limiting): exist At +0.8ms, the fault current limiter activates, limiting the fault current from the expected 20kA RMS value to 1.3kA (approximately twice the rated current).

[0066] Actual measurements show that after current limiting, the instantaneous power of the arc drops to approximately 380×3270≈1.24MW, which is only 6.5% of the original power, fundamentally cutting off the continuous injection of arc energy.

[0067] Second-level suppression (jet arc extinguishing): CO2 is used as the injection medium to calculate the injection volume. Pressure conversion rule: Absolute pressure = Relative pressure + Standard atmosphere, where standard atmosphere is approximated as 0.101 MPa in engineering. (Relative pressure, i.e., absolute pressure 12.101 MPa), take... ,have:

[0068] The calculated volume of CO2 gas to be injected (under standard conditions) is approximately 23 standard liters. Since the gas chamber is a high-risk compartment, the system opens the corresponding solenoid valve to release a corresponding amount of liquid CO2 from the common storage tank. The liquid CO2 expands in volume approximately 450 times after vaporization; therefore, only a very small amount of liquid CO2 (approximately 0.055L) needs to be released from the 5L storage tank to meet the 25 standard liter injection requirement. The injection duration is approximately 45ms, and the actual injection volume is approximately 25 standard liters (calibrated after considering pipeline losses and nozzle characteristics).

[0069] By adaptively calculating the injection volume of the injected gas based on the deviation between the predicted peak pressure and the safety threshold, it is possible to achieve adaptive matching between the injection volume and the severity of arcing, quickly and quantitatively calculate the gas injection volume, and avoid gas waste or insufficient suppression.

[0070] The injected CO2 at this time has multiple arc-quenching effects: Physical cooling: When CO2 is ejected from the storage tank, it rapidly vaporizes and expands (Joule-Thomson effect), generating a low-temperature gas flow (down to -50°C), which undergoes intense heat exchange with the high-temperature electric arc (about 20,000°C), rapidly reducing the temperature of the electric arc channel; Chemical arc quenching: CO2 decomposes at the high temperature of the electric arc, consuming the energy of the electric arc, and the decomposition products can promote the recombination of charged particles. Arc blowing effect: High-pressure gas injection forms a directional airflow, which stretches the arc path and accelerates arc cooling; Deionization effect: Airflow purging promotes the diffusion and recombination of charged particles in the arc channel, improving the dielectric recovery strength.

[0071] In this embodiment, CO2 is used as the injection medium because it has a higher density and specific heat capacity, a stronger cooling effect, and can be stored in liquid form in the storage tank (high storage efficiency). In practical applications, other gases with stronger chemical inertness and no corrosiveness to equipment can also be selected as the injection medium, depending on cost and supply conditions.

[0072] Under the same test conditions (dry air insulation in the chamber, expected short-circuit current of 20kA), four sets of comparative tests were set up as shown in Table 1 below: Table 1: Comparison of Arcing Conditions under the Same Conditions - Explanation Table

[0073] In summary, the present invention reduces the peak absolute pressure generated by the arc to 0.30 MPa, which is lower than the design withstand threshold of 0.35 MPa, while keeping the cabinet structure intact.

[0074] In short, by organically combining two physical methods, "current limiting" and "jet arc extinguishing," a graded suppression operation is implemented. The first stage, current limiting, cuts off the arc supply at the energy source. The second stage, jet arc extinguishing, accelerates the extinguishing of the existing arc. Low-risk situations only trigger an alarm, medium-risk situations involve current limiting, and high-risk situations combine current limiting with jet extinguishing. This approach maximizes safety while minimizing operational losses. Furthermore, it enables a shift from passively accepting internal arcing faults to actively predicting and graded suppressing them, effectively reducing the destructive impact of arcing faults on the cabinet and ensuring the safety of maintenance personnel.

[0075] Because dry air has a lower arc-extinguishing capacity than SF6, the peak pressure exceeds the cabinet's withstand threshold when only a single protective measure is taken (flow only or jet only).

[0076] The present invention employs a synergistic graded suppression strategy of current limiting and CO2 injection, which can control the peak pressure within a safe range even under dry air insulation conditions, fully verifying the technical superiority of the present invention and its adaptability to environmentally friendly gas ring main units.

[0077] Furthermore, to further verify the adaptability of this invention to different insulating media, the results of this embodiment (dry air insulation combined with CO2 injection) were compared with the test results of SF6 insulated ring main units (same cabinet volume, same short-circuit current of 20kA, and CO2 injection medium). The comparative test results are shown in Table 2 below: Table 2: Comparison of test results between the present invention and SF6 insulated ring main unit

[0078] The results show that although the thermal effects of dry air insulated ring main units under arcing faults are more severe (peak power is about 3 times that of SF6), the graded suppression scheme of the present invention can still effectively control the pressure peak within a safe range and fully meet the requirements for internal arcing protection.

[0079] In summary, the complete sequence of actions on the dry air environmental protection ring main unit is as follows: Arc triggering (dual criteria of arc light and current change), the system identifies arc events (time < 0.2ms). +0.5ms: The model completes the stress prediction and outputs the hazard level (high risk). +0.8ms: The current limiter activates, and the current begins to decrease; +1.5ms: The CO2 injection device activates and begins injecting high-pressure CO2 into the arcing area; +4.0ms: The arc is completely extinguished and the current drops to zero; +16ms: The compartment pressure drops below the safe value (0.20MPa).

[0080] The total time from arc triggering to complete arc extinction is approximately 4.0 ms, which is much shorter than the 40-60 ms breaking time of traditional circuit breakers. It still achieves effective protection for the ring main unit under the harsh conditions of dry air insulation.

[0081] The ultrafast current limiter here has an action time of <1ms, which is two orders of magnitude faster than traditional circuit breakers (40-60ms). Combined with a pressure sensor with a response of <0.1ms, this invention can achieve true "initial arc suppression".

[0082] Furthermore, in this embodiment, the technical solution of the present invention also has the following environmental advantages: Zero GWP emissions: The ring main unit uses dry air as the main insulation medium, with GWP=0, completely replacing SF6 and eliminating greenhouse gas emissions.

[0083] Environmentally friendly injection medium: The active suppression device uses CO2 as the injection medium. CO2 has a GWP of 1 (far less than SF6's 23,900), making it environmentally friendly as an emergency suppression medium. The injection medium is released into the atmosphere after arcing, with no long-term negative impact on the environment.

[0084] Non-toxic: Both dry air and CO2 are non-toxic and harmless. The combustion decomposition products of dry air are only a small amount of nitrogen oxides (which can be treated by simple filtration), which is much safer than the highly toxic low-fluorine sulfides produced by the decomposition of SF6.

[0085] Easy to maintain: The air box uses dry air as the main insulating medium (GWP=0), which can be directly generated from the ambient air. No special equipment is required for replenishment and replacement, resulting in low operation and maintenance costs.

[0086] Furthermore, this embodiment fully verifies the effectiveness of the system and method of the present invention in preventing and controlling arcing faults inside environmentally friendly gas-insulated ring main units.

[0087] Furthermore, through proactive prediction and graded suppression, internal arcing failures can be downgraded from "catastrophic accidents" to "recoverable events," thereby significantly improving the safe operation level of environmental gas ring main units.

[0088] In another aspect, the present invention also discloses a computer-readable storage medium storing a computer program, which, when executed by a processor, causes the processor to perform the steps of the method described above.

[0089] In another aspect, the present invention also discloses a computer device, including a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor performs the steps of the method described above.

[0090] In another embodiment of the present invention, a computer program product containing instructions is also provided, which, when run on a computer, causes the computer to execute the temperature and pressure prediction and prevention method for arcing faults inside any of the ring main units in the above embodiments.

[0091] It is understood that the system provided in the embodiments of the present invention corresponds to the method provided in the embodiments of the present invention, and the explanation, examples and beneficial effects of the relevant content can be referred to the corresponding parts of the above methods.

[0092] This invention also provides an electronic device, including a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other via the communication bus. Memory, used to store computer programs; The processor, when executing the program stored in the memory, implements the temperature and pressure prediction and prevention method for arcing faults inside the ring main unit.

[0093] The communication bus mentioned in the above-mentioned electronic devices can be a standard bus for interconnecting peripheral components or an extended industrial standard structure bus, etc. This communication bus can be divided into address bus, data bus, control bus, etc.

[0094] The communication interface is used for communication between the aforementioned electronic devices and other devices.

[0095] The memory may include random access memory or non-volatile memory, such as at least one disk storage device. Optionally, the memory may also be at least one storage device located remotely from the aforementioned processor.

[0096] The processors mentioned above can be general-purpose processors, including central processing units, network processors, etc.; they can also be digital signal processors, application-specific integrated circuits, field-programmable gate arrays or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components.

[0097] In the above embodiments, implementation can be achieved entirely or partially through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented entirely or partially as a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of the present invention are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired or wireless means. The computer-readable storage medium can be any available medium accessible to a computer or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium, an optical medium, or a semiconductor medium, etc.

[0098] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0099] Furthermore, it should be noted that if any directional indication (such as up, down, left, right, front, back, etc.) is involved in the embodiments of the present invention, the directional indication is only used to explain the relative positional relationship and movement of each component in a specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0100] Furthermore, those skilled in the art should understand that in the actual use of the embodiments of the present invention, there may be preset thresholds as the basis for judging the corresponding technical solutions. These thresholds are conventional technical means commonly used in the field to implement functions such as state judgment, condition recognition, and control logic switching. The specific values, setting basis, value selection methods, determination methods, and adjustment rules of the thresholds involved in this technical solution are all conventional technical choices that can be reasonably determined by those skilled in the art based on conventional technical factors such as actual application scenarios, system working states, characteristics of the detection object, hardware performance parameters, and functional requirements, through conventional experiments, calibrations, and debugging. The specific setting and adjustment of the aforementioned thresholds will not cause the overall implementation of this technical solution to be impossible, nor will it affect the realization of the core concept and the achievement of the technical effects of this technical solution.

[0101] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the meaning of "and / or" throughout the text includes three parallel solutions; for example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, in the embodiments of this invention, "multiple" refers to two or more. Moreover, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

Claims

1. A temperature and pressure prediction and graded prevention and control system for arcing faults inside a ring main unit, characterized in that, include: The multi-physical quantity sensor module is deployed in the arc risk compartment of the ring main unit to monitor the gas temperature change in the compartment, quickly trigger identification after an arc event occurs, and capture the pressure rise process at the moment of arc in real time. The multi-physical quantity sensor module acquires data through sensors and then transmits it to the edge computing unit; The edge computing unit, deployed in the secondary compartment of the ring network cabinet, incorporates a dynamic temperature and pressure coupling prediction algorithm based on energy conservation and the gas state equation. It is used to receive sensor transmission data from the multi-physical quantity sensor module in real time, construct the coupled differential relationship between the real-time pressure change rate inside the compartment and the arc energy injection rate and the pressure relief and exhaust rate, predict the arc development process, output the peak arc pressure, complete the hazard level assessment, and finally send graded suppression commands to the active suppression device based on the hazard level and prediction results. Active suppression device is used to limit the fault current amplitude in stages and spray insulating gas to suppress the spread of arc in the early stage of internal arcing fault in ring main unit, quickly extinguish the fault arc and isolate the fault energy, so as to reduce the safety risks of equipment burn-out, cabinet deformation and cracking and electric shock burns to maintenance personnel. The real-time pressure inside the compartment The coupling differential relationship between the rate of change and the arc energy injection rate and the depressurization and exhaust rate is as follows: in, The adiabatic index of the gas inside the compartment. The initial free volume of the compartment where the arcing failure occurred. The effective pressure relief area of ​​the pressure relief channel. The flow coefficient of the pressure relief port. The initial gas density in the compartment. For environmental absolute pressure, The instantaneous power of the electric arc is determined by the arc voltage. and arc current The product is calculated.

2. The temperature and pressure prediction and graded prevention and control system for arcing faults inside a ring main unit as described in claim 1, characterized in that, The multi-physical quantity sensor module is independently configured in each compartment where arcing may occur, including: A fast-response pressure sensor with a range of 0–5 MPa is used to capture the pressure rise process during the instantaneous arcing. Thermocouple sensor: The range is set to -40℃ to +500℃, used to monitor changes in gas temperature inside the compartment; Arc light sensor: Employs ultraviolet / visible dual-spectrum detection to quickly trigger and identify arcing events occurring inside the cabinet.

3. The temperature and pressure prediction and graded prevention and control system for arcing faults inside a ring main unit as described in claim 1, characterized in that, The active inhibition device includes: An ultra-fast-acting fault current limiter, installed in series on the incoming side of the ring main unit, employs solid-state switching or fast mechanical disconnection technology to reduce the fault current from its peak value during the initial stage of arcing. Limit to safe value the following; The insulating gas injection device includes a common high-pressure gas storage tank, as well as branch pipelines and independent solenoid valves leading to each arc risk compartment. The injection medium is directionally injected into the fault compartment under independent control of the solenoid valves, and the gas is quickly discharged through the pressure relief channel after injection.

4. A method for temperature and pressure prediction and hierarchical prevention of arcing faults inside a ring main unit, implemented based on the temperature and pressure prediction and hierarchical prevention system for arcing faults inside a ring main unit as described in any one of claims 1-3, characterized in that, include: Step S1. Continuously collect real-time pressure data inside the risk compartment. rate of change, temperature He Guangqiang The signal, in which the sampling of all sensors is synchronized; Step S2. Determine whether there is an arc inside the cabinet by detecting ultraviolet / visible dual-spectrum light and current changes inside the cabinet; Step S3. Activate the dynamic coupling prediction model of temperature and pressure through the edge computing unit, output the real-time arcing parameters inside the cabinet, and construct the real-time pressure inside the compartment. The coupled differential relationship between the rate of change and the arc energy injection rate and the pressure relief and exhaust rate; Step S4. The coupled prediction model uses the fourth-order Runge-Kutta method to numerically solve the coupled differential relationship to predict the pressure change curve and extract the predicted peak pressure. And based on the preset level determination rules, the arc hazard level is assessed; Step S5. Actively suppress arcing inside the cabinet according to the hazard level classification; Step S6. After the arc is suppressed, the system records the fault time, peak pressure, and action timing data, and issues an alarm signal, waiting for maintenance personnel to troubleshoot the fault and reset the system. In the absence of an arcing event, the edge computing unit is in standby monitoring and only collects sensor data.

5. The method for temperature and pressure prediction and graded prevention and control of arcing faults inside a ring main unit as described in claim 4, characterized in that, The specific criteria for determining whether an arcing occurs inside the cabinet in step S2 are as follows: An arcing event is determined to have occurred when any of the following conditions are met: Condition A: The output of the arc light sensor exceeds the preset light intensity threshold. ; Condition B: Rate of change of current and voltage sag rate All exceeded the corresponding preset threshold; After triggering, record the moment of arcing. and collect Initial pressure at any moment Initial temperature of the cabinet's internal environment , which serves as the initial input value for the prediction model in step S3.

6. The method for temperature and pressure prediction and graded prevention and control of arcing faults inside a ring main unit as described in claim 5, characterized in that, The arc voltage The improved Cassie-Mayr mixture model is used to describe this, as follows: in, , , These are the characteristics of the electric arc. For reference current, It is a time constant; The arc length In the case of a three-phase short circuit, the shortest distance between two phase conductors is taken.

7. The method for temperature and pressure prediction and graded prevention and control of arcing faults inside a ring main unit as described in claim 4, characterized in that, The specific process for assessing the arc hazard level based on preset level determination rules in step S4 includes: The safe pressure withstand threshold of the cabinet is calibrated through type testing. For threshold : like If so, it is determined to be a low-risk arcing event, and only an alarm is recorded; like If so, it is determined to be a medium-risk arcing event, triggering the first level of current limiting suppression; like If it is determined to be a high-risk arcing, it will trigger the first-level flow restriction suppression and the second-level injection suppression simultaneously; After implementing the first level of current limiting and suppression, the edge computing unit continuously monitors the rate of pressure change; if in The pressure is expected to continue rising rapidly over the next period, and the peak is predicted to exceed [a certain value]. If this occurs, the second level of jet suppression will be triggered immediately.

8. The method for temperature and pressure prediction and graded prevention and control of arcing faults inside a ring main unit as described in claim 4, characterized in that, The specific operational procedure for actively suppressing arcing inside the cabinet in step S5 includes the following steps: Step S51. First-stage current limiting suppression: Trigger the ultra-fast fault current limiter to reduce the fault current from its peak value within 1ms. Limit to safe value the following; Step S52. Second-level injection suppression: In high-risk arcing scenarios, start the insulating gas injection device, open the solenoid valve of the corresponding arcing compartment, and inject insulating gas into the fault area; Total gas injection volume Based on predicted peak pressure The deviation from the safety threshold is adaptively calculated using the following formula: in, This is an empirical proportionality coefficient, calibrated through arcing tests. Let CO2 be the gas constant of the injected gas. Pre-charge the gas storage tank to absolute pressure. The initial free volume of the compartment where the arcing failure occurred. The initial temperature of the internal environment of the cabinet. To calibrate the safe pressure threshold of the cabinet through type testing.

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