A method for identifying an arc in a cable compartment of a switchgear and an arc pressure relief device

Abstract

This invention discloses a method for arc detection and an arc relief device for the cable compartment of a switchgear, belonging to the field of power equipment fault handling technology. The arc detection method for the switchgear cable compartment of this invention periodically collects arc light data, current data, and pressure data, and then compares them with corresponding thresholds to confirm whether an arc has occurred. Simultaneously, it periodically collects environmental data and load data of the switchgear, updating some thresholds to make the arc fault identification more consistent with the specific installation environment and operating status of the switchgear. The arc relief device of this invention separates the arc detection circuit from the threshold update circuit; during the arc detection process, the threshold is in a latched state. This invention confirms the working priority through update signals, activation signals, and loading signals, avoiding conflicts between the arc detection and threshold update operation logic.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power equipment fault detection, and in particular to an arc recognition method for a cable chamber of a switch cabinet and an arc pressure relief device. BACKGROUND

[0002] During the operation of a switch cabinet, arc phenomenon may occur in the cable chamber, accompanied by changes in light, current and pressure. Arc phenomenon is mainly identified through arc light, current and pressure data. Chinese patent application No. CN108270205A discloses an arc monitoring protection system based on pressure protection. The system acquires arc light signals from an arc light sensor to determine whether arc light appears in the switch cabinet, acquires pressure signals from a pressure sensor to determine whether pressure suddenly increases in the switch cabinet, and then determines whether arc phenomenon occurs through a DSP processor and sends grounding instructions to a fast grounding switch. Although this system avoids visible light interference, the arc monitoring time depends on the computing power of the data processing unit, limiting the arc recognition speed. Chinese patent application No. CN121440500A discloses a high-altitude switch cabinet arc fault intelligent response method. The method collects light intensity change signals and pressure change signals, and determines that an arc fault occurs when the light intensity change signals indicate the presence of arc light and the pressure rise rate exceeds a preset action threshold. In the case of environmental data changes, the fixed action threshold limits the arc recognition accuracy. In addition, Chinese patent application No. CN121231951A discloses a switch cabinet arc fault detection method. The method collects three-phase current signals of each feeder circuit in the switch cabinet, obtains current modal components through processing and decomposition, and then identifies arc faults. This method uses current signals as the determination standard, which can reduce the influence of environmental data, but is not suitable for situations where switch cabinet load data changes dynamically, and requires dynamic updating of the threshold in combination with the operating conditions. Furthermore, arc faults occur in a short time, and if the arc fault is detected during threshold updating, it may cause a conflict in the operating logic of the circuit. SUMMARY

[0003] To solve the above problems, the present application provides an arc recognition method for a cable chamber of a switch cabinet, which can update the recognition threshold, making the arc fault recognition more consistent with the installation environment and operating state of the specific switch cabinet. The present application confirms the working priority through updating signals, activation signals and loading signals, avoiding conflicts in the operating logic of arc recognition and threshold updating.

[0004] The present application also discloses an arc pressure relief device for implementing the arc recognition method for the cable chamber of the switch cabinet. The arc pressure relief device separates the arc recognition circuit from the threshold updating circuit, and the threshold is in a latching state during the arc recognition process. Furthermore, the present application uses flip-flops, gate circuits and other hardware to build the arc pressure relief device, avoiding electromagnetic interference and chip software delays, and enabling timely pressure relief actions.

[0005] The application objectives of the present application can be achieved by the following technical means: The application objectives of the present application can be achieved by the following technical means: Step 1: obtaining the structure data and design target of the cable chamber, initializing the first threshold value, the second threshold value and the third threshold value; Step 2: collecting a group of environmental data and load data of the cable chamber every first period, updating the first threshold value and the second threshold value, and generating an update signal after outputting the first threshold value and the second threshold value to the buffer; Step 3: collecting a group of arc light data, current data and pressure data every second period, generating an activation signal if the arc light data is greater than the first threshold value of the main latch, and entering step 4, otherwise generating a loading signal and entering step 7; Step 4: entering the detection state, entering step 5 if the current data is greater than the second threshold value of the main latch or the pressure data is greater than the third threshold value of the main latch, otherwise entering step 6; Step 5: entering the pressure relief state, identifying the arc fault and performing the pressure relief action, and ending the task; Step 6: returning to step 2 if the activation signal ends, otherwise repeating step 4; Step 7: entering the standby state, the main latch reading the first threshold value and the second threshold value from the buffer based on the loading signal and the update signal, and returning to step 2.

[0006] In the present application, in step 1, the structure data includes the minimum arc distance, the free volume and the cabinet reflection coefficient of the cable chamber, the design target includes the rated voltage and the short-circuit capacity, the arc illumination is calculated according to the minimum arc distance, the first threshold value is initialized in combination with the cabinet reflection coefficient and the arc illumination, the minimum two-phase short-circuit current is calculated according to the rated voltage and the short-circuit capacity, the second threshold value is initialized according to the product of the sensitivity coefficient and the minimum two-phase short-circuit current, and the third threshold value is initialized according to the power density calculated according to the minimum two-phase short-circuit current and the free volume, in combination with the time length of the second period and the power density.

[0007] In the present application, in step 2, the environmental data includes the real-time temperature and the real-time humidity, the temperature correction factor is updated by the real-time temperature, the humidity correction factor is updated by the real-time humidity, and the first threshold value is updated, the load data is the maximum load current in the current first period, and the larger value of the product of the maximum load current and the minimum two-phase short-circuit current is updated as the second threshold value.

[0008] In this invention, in step 3, multiple sets of state transition durations from the detection state to the depressurization state are extracted, the pressure wave velocity is corrected according to the real-time temperature, the pressure response duration is updated according to the pressure wave velocity and the maximum arc distance, and the duration of the activation signal is adjusted by combining the state transition duration and the pressure response duration.

[0009] An arc-relief device for implementing the arc identification method in the cable compartment of the switchgear includes: The arc light sensing unit is configured to collect arc light data from the cable compartment; The current sensing unit is configured to collect current data from the cable compartment; The pressure sensing unit is configured to collect pressure data from the cable compartment. The master latch is configured to store the first threshold, the second threshold, and the third threshold. The first identification unit is configured to generate detection commands or standby commands based on arc light data; The second identification unit is configured to generate a pressure relief command based on detection commands, current data, or pressure data. The actuator is configured to perform a pressure relief action based on a pressure relief command; The environmental data acquisition unit is configured to collect environmental data from the switchgear. The load acquisition unit is configured to acquire load data from the switchgear. The host computer is configured to update the first threshold and the second threshold based on environmental data and load data; The cache is configured to store the first threshold and the second threshold; and the first flip-flop and the second flip-flop, wherein, After the host computer outputs the first threshold and the second threshold, it generates an update signal. After the first trigger receives the standby command, it outputs a load signal. The main latch reads the first threshold and the second threshold from the buffer based on the load signal and the update signal. After the second trigger receives the detection command, it outputs an activation signal, which is sent to the output of the second identification unit.

[0010] In this invention, the first identification unit includes a first comparator, a hysteresis resistor, and a positive feedback resistor. The non-inverting input of the first comparator is connected to the arc light sensing unit. The inverting input of the first comparator is connected to the arc light storage module of the main latch via a hysteresis resistor. The output of the first comparator is connected to the inverting input via a positive feedback resistor. The output of the first comparator and the output of the second flip-flop are connected to a first OR gate module.

[0011] In this invention, the second identification unit includes two sets of second comparators and second OR gate modules. The non-inverting input of one second comparator is connected to a current sensing unit, the inverting input is connected to the current storage module of the main latch, and the output is connected to the second OR gate module. The non-inverting input of the other second comparator is connected to a pressure sensing unit, the inverting input is connected to the pressure storage module of the main latch, and the output is connected to the second OR gate module. The output of the second OR gate module and the output of the first OR gate module are connected to a first AND gate module, and the output of the first AND gate module is connected to an actuator.

[0012] In this invention, the first trigger includes an inverter, a second AND gate module, and a rising edge detection circuit. The standby command of the first comparator is input to the second AND gate module via the inverter. The update signal of the host computer is input to the second AND gate module. The output of the second AND gate module is connected to the rising edge detection circuit. The output of the rising edge detection circuit is connected to the latch switch of the main latch.

[0013] In this invention, the second trigger includes a monostable circuit, a timing resistor, and a timing capacitor. The detection command of the first comparator is input to the rising edge of the monostable circuit. The timing resistor and the timing capacitor are respectively connected to the resistor timing terminal and the capacitor timing terminal of the monostable circuit. The output terminal of the monostable circuit and the first comparator are connected to the first OR gate module.

[0014] In this invention, an auxiliary latch and a third trigger are also included. The host computer sends the updated value of the timing resistor or the updated value of the timing capacitor to the auxiliary latch. The host computer and the first identification unit are connected to the third trigger, which controls the read switch of the auxiliary latch.

[0015] The present invention provides a method for arc detection and an arc pressure relief device for a switchgear cable compartment. The advantages of this method are as follows: The invention updates the detection threshold by combining environmental and load data, making the identification of arc faults more consistent with the specific installation environment and operating status of the switchgear. After the arc detection is completed, a loading signal is generated, and the updated threshold is stored in the main latch, avoiding conflicts between arc detection and threshold update. Furthermore, the invention can update the preset duration of the detection state, ensuring timely identification of current and pressure changes after the arc light signal occurs, while avoiding the loss of the next arc light signal due to excessive identification time. The arc pressure relief device of the present invention separates the arc detection circuit from the threshold update circuit; during the arc detection process, the threshold is in a latched state. The arc detection circuit is built using basic circuit components such as gate circuits, and the detection state duration is realized through the level state of a trigger, avoiding the use of upper-level computer chip control software. This allows for faster identification of arc phenomena and timely pressure relief actions. Attached Figure Description

[0016] Figure 1 This is a flowchart of the arc detection method for the cable compartment of the switchgear of the present invention; Figure 2 This is a schematic diagram of arc light data when an arcing failure occurs; Figure 3 This is a schematic diagram of current data during an arcing fault. Figure 4 This is a schematic diagram of pressure data when an arcing failure occurs; Figure 5 This is a schematic diagram of the layout of the switchgear of the present invention; Figure 6 This is a comparison diagram of the level states of the host computer update signal, the first identification unit loading signal, and the main latch latch enable signal at different times in this invention. Figure 7 This is a schematic diagram of the arc relief device for implementing the arc identification method in the cable compartment of the switchgear according to the present invention; Figure 8 This is a schematic diagram showing the connection of the first identification unit, the second identification unit, the first trigger, and the second trigger of the present invention. Figure 9 This is a schematic diagram showing the connection between the third trigger and the auxiliary latch of the present invention; Figure 10 This is a schematic diagram of the connection of the host computer of the present invention; The reference numerals in the attached drawings are: Instrument compartment 10, Handcart compartment 20, Circuit breaker 21, Busbar compartment 30, Busbar bar 31, Cable compartment 40, Cable 41, and Sensing component 50. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Example 1

[0018] This invention discloses a method for arcing identification in the cable compartment of a switchgear. The invention confirms the working priority through update signals, activation signals, and loading signals, avoiding conflicts between arcing identification and threshold update operation logic. The updated threshold is used to identify arcing faults, making arcing fault identification more consistent with the specific installation environment and operating status of the switchgear. Figures 1 to 6 The present invention provides a method for arc detection in the cable compartment of a switchgear, comprising the following steps.

[0019] Step 1: Obtain the structural data and design objectives of the cable compartment, and initialize the first, second, and third thresholds. The structural data includes the minimum arcing distance, free volume, and cabinet reflection coefficient of the cable compartment. The design objectives include rated voltage and short-circuit capacity. As described in Embodiment 2, this invention calculates the arcing illuminance based on the minimum arcing distance, and initializes the first threshold by combining the cabinet reflection coefficient and the arcing illuminance; it calculates the minimum two-phase short-circuit current based on the rated voltage and short-circuit capacity, and initializes the second threshold by the product of a sensitivity coefficient and the minimum two-phase short-circuit current. The power density is calculated based on the minimum two-phase short-circuit current and free volume, and then the third threshold is initialized by combining the duration of the second cycle and the power density.

[0020] Step 2: At each interval of the first cycle, a set of environmental and load data for the cable room is collected. The first and second thresholds are updated, and an update signal is generated after outputting the first and second thresholds to the buffer. As described in Example 2, the environmental data in this example includes real-time temperature and real-time humidity. The temperature correction factor is updated based on the real-time temperature, and the humidity correction factor is updated based on the real-time humidity, before updating the first threshold. The load data is the maximum load current in the current first cycle. The larger value of the product of this maximum load current, the sensitivity coefficient, and the minimum two-phase short-circuit current is updated as the second threshold.

[0021] Step 3: Every second cycle, collect a set of arc light data, current data, and pressure data. If the arc light data is greater than the first threshold of the main latch, generate an activation signal and proceed to Step 4; otherwise, generate a loading signal and proceed to Step 7. The arc light data and current data are the current values ​​of light intensity and current, and the pressure data is the absolute difference in pressure between the current cycle and the previous cycle. Referring to Example 5, after returning to Step 3, the duration of the activation signal can be adjusted based on the execution status of each step in the previous cycle. This invention extracts multiple sets of state transition durations from the detection state to the depressurization state, corrects the pressure wave velocity based on real-time temperature, updates the pressure response duration based on the pressure wave velocity and the maximum arcing distance, and adjusts the duration of the activation signal based on the state transition duration and the pressure response duration. Since the arcing phenomenon is a sudden phenomenon, the environmental data and load data change slowly, and the duration of the first cycle is longer than that of the second cycle. The duration of the first cycle is, for example, 10 min to 1 h, and the duration of the second cycle is, for example, 2 ms to 50 ms.

[0022] Step 4: Enter the detection state. If the current data is greater than the second threshold of the main latch or the pressure data is greater than the third threshold of the main latch, proceed to step 5; otherwise, proceed to step 6. Arc light data is the core data; current and pressure are used for secondary arc detection to avoid external light sources such as flashlights affecting the accuracy of the detection. After entering the detection state, this invention continuously compares the current and pressure data to confirm whether an arcing phenomenon has occurred.

[0023] Step 5: Enter the pressure relief state, identify the arcing fault and execute the pressure relief action to end the task. The pressure relief action includes, but is not limited to, opening the pressure relief valve in the pressure relief channel and disconnecting the bus switch. After the arcing data, current data, and pressure data all meet the corresponding thresholds, the external equipment can restart the pressure relief valve or bus switch.

[0024] Step 6: If the activation signal ends, return to step 2; otherwise, repeat step 4. Figures 2 to 4 As shown, current and pressure anomalies may occur after the arc signal, especially pressure anomalies, which typically lag behind the arc signal by about 10ms. Simultaneous comparison of arc data with current and pressure data may delay arc detection. This invention creates an activation signal after identifying an arc data anomaly. While the activation signal is high, the current and pressure data are repeatedly compared. The duration of the detection state depends on the duration of the activation signal, which is, for example, 15 to 100ms. This invention further discloses that the host computer adjusts the duration based on historical arc phenomena to ensure timely arc detection after the arc signal occurs, while avoiding excessive time that could lead to the loss of other real arc data.

[0025] Step 7: Enter standby mode. The main latch reads the first and second thresholds from the buffer based on the load and update signals, and returns to step 2. In the detection mode, the thresholds updated by the host computer are stored in the buffer, and the main latch is in a latched state. After entering standby mode, the latch enable pin of the main latch is activated, and the thresholds in the buffer are sent to the main latch. Figure 6 As shown, when both the update signal and the load signal are high, the latch enable signal also goes high, and the latch enable terminal of the main latch is available. Therefore, in the detection state, arcing has a higher priority, the main latch latches the threshold, and the first identification unit can smoothly read data from the main latch, avoiding the threshold being updated during reading, which would affect the arcing identification speed. When entering standby mode and simultaneously receiving an update signal from the host computer, the main latch reads data from the buffer to update the threshold. Example 2

[0026] This embodiment further discloses a preferred method for initializing and updating the first threshold, the second threshold, and the third threshold.

[0027] Based on the minimum arc distance d min Calculate arc illuminance E arc The first threshold is initialized by combining the cabinet's reflectivity and the arc illuminance. The luminous intensity I for arc ignition is then set. source The luminous intensity I of arc-induced detonation source The empirical value is usually 300 to 400 cd. Direct illuminance E arc =I source / d min2 Arcing typically occurs at cable joints and bends. (Refer to...) Figure 5 d min The minimum distance between the arc sensor unit's installation location and cable joints or corners can be selected. The inner wall of the switch cabinet is typically made of painted steel plate. Light undergoes multiple reflections through this plate within the enclosed space, increasing the total received light intensity E. total It is higher than the direct illuminance. Therefore, the total luminous intensity E total =E arc / (1-ρ). ρ is the cabinet reflectivity. The inner wall of the switch cabinet cable compartment is usually made of light gray or milky white painted steel plate, and the cabinet reflectivity ρ≈0.55 to 0.70. In this embodiment, the total light intensity is the initial first threshold β1, i.e., β1=E total In a more preferred embodiment, the total light intensity can be further corrected by considering the device aging factor and sensor sensitivity.

[0028] Calculate the minimum two-phase short-circuit current based on the rated voltage and short-circuit capacity. Initialize the second threshold based on the product of the sensitivity coefficient and the minimum two-phase short-circuit current. The per-unit reactance value of the equipment is X1 = S0 / S1, where S0 is the base capacity of the power distribution system and S1 is the short-circuit capacity of the power distribution system. The per-unit reactance value of the cable is X2 = R1S0 / U1. 2 U1 is the rated voltage of the power distribution system (high-voltage side), and R1 is the total cable resistance in the cable room. Minimum two-phase short-circuit current I min =S0 / [2U1(X1+X2)]. According to the relay protection regulations, the sensitivity coefficient k of the instantaneous overcurrent protection under the minimum operating mode is... sen It must not be less than 1.5. The second threshold β2 = I min k sen If we further consider the changes in the current transformer measurement method, the second threshold can be optimized by adjusting the step-down ratio.

[0029] The power density is calculated based on the minimum two-phase short-circuit current and free volume, and then the third threshold is initialized by combining the duration of the second cycle and the power density. The minimum two-phase short-circuit voltage U2 corresponding to the minimum two-phase short-circuit current is calculated using the empirical formula U2 = I. min λ (b1+b2d3), where b1 and b2 are fitting coefficients, typically b1=20 and b2=534. λ is related to the cable material; for copper core cables, λ can be 0.12. d3 is the cable length. Power density w=(k p -1)U2I min / V. V is the free volume of the cable compartment, k p The heat conversion coefficient is typically taken as 1.2 to 1.5. The third threshold β3 is the allowable pressure increment ΔP during the second cycle. For the second cycle duration t1, β3 = ΔP = wt1.

[0030] The temperature correction factor is updated based on real-time temperature, the humidity correction factor is updated based on real-time humidity, and then the first threshold is updated. Temperature and humidity primarily affect the response of the arc sensing unit; typical silicon photodiodes experience decreased sensitivity at high temperatures, resulting in a lower output signal. Temperature correction factor K T =1-α T (TT ref T represents the current temperature. ref This is the reference operating temperature for the sensing unit, for example, 25°C. α T This is a temperature coefficient, dependent on sensor characteristics, for example, 0.005 / ℃ or -0.005 / ℃. High humidity increases light scattering, leading to increased background light noise. Humidity correction factor K. R =1+α R ⋅max(0,RR ref R is the current humidity. ref For reference humidity (e.g., 60%). α R This represents the humidity coefficient (e.g., 0.003 / %RH, where RH is the humidity unit). A first-order smoothing filter is used, with a filter parameter γ1 set to less than 1, β1 = γ1(E total K T K R )+(1-γ1)E total In a simpler embodiment, the specific size of the correction factor can be determined using an algorithm calibrated by the manufacturer of the arc sensing unit.

[0031] The load data is the maximum load current within the current first cycle. The larger of the product of this maximum load current and the minimum two-phase short-circuit current is updated as the second threshold. A sampling window with a duration equal to the first cycle is maintained, and the maximum load current I within this sampling window is extracted. max Because equipment start-up and shutdown may occur during the sampling window, the load current may surge briefly during these periods. To prevent false triggering due to load fluctuations during normal start-up and shutdown, a load avoidance factor k is typically set. load Adjust the maximum load current, k load Typically, a value of 1.2 to 1.5 is chosen. The updated second threshold β2 is k. load I max with I min k sen The larger one, i.e., β2 = max(k load I max ,I min k sen Similarly, a filter parameter γ1 less than 1 can be set to perform first-order smoothing filtering on the second threshold. Example 3

[0032] This invention also discloses an arc-relief device for implementing the arc identification method in the cable compartment of the switchgear. This arc-relief device separates the arc identification circuit from the threshold update circuit, and the threshold is latched during the arc identification process. Figure 5 The switchgear includes an instrument compartment 10, a truck compartment 20, a busbar compartment 30, and a cable compartment 40. Cable 41 connects to the busbar 31 in the busbar compartment 30 via the cable compartment 40. Cable 41 also connects to the circuit breaker 21 in the truck compartment 20 for disconnecting the main circuit. An arc-relieving device is typically installed in the cable compartment 40. Arc sensing units, current sensing units, and pressure sensing units are encapsulated in sensing components 50 and arranged in different areas of the cable compartment 40. An environmental acquisition unit is installed in the cable compartment 40, and a load acquisition unit is connected in parallel to cable 41.

[0033] like Figures 7 to 10 As shown, an arc-dissipating pressure relief device for implementing the arc identification method in the cable compartment of the switchgear according to the present invention includes: an arc light sensing unit, a current sensing unit, a pressure sensing unit, a main latch, a first identification unit, a second identification unit, an actuator, an environmental acquisition unit, a load acquisition unit, a host computer, a buffer, and a first trigger and a second trigger.

[0034] The arc light sensing unit is configured to collect arc light data from the switchgear cable compartment. It employs a passive fiber optic design to achieve photoelectric isolation and electromagnetic interference resistance. The current sensing unit is configured to collect current data from the switchgear cable compartment. It uses a wide-frequency response Hall effect sensor, outputting an electrical signal proportional to the load current during normal operation. The pressure sensing unit is configured to collect pressure data from the switchgear cable compartment. It uses a high-frequency response differential pressure transmitter. The environmental acquisition unit is configured to collect environmental data from the switchgear. This unit could be a general-purpose temperature and humidity sensor, a smoke detector, etc. The load acquisition unit is configured to collect load data from the switchgear. This unit can be multiplexed with the current sensing unit and is invoked by the host computer within the first cycle.

[0035] The first identification unit is configured to generate a detection command or a standby command based on arc light data. The second identification unit is configured to generate a pressure relief command based on the detection command, current data, or pressure data. The actuator is configured to perform a pressure relief action based on the pressure relief command. The host computer is configured to update the first and second thresholds based on environmental and load data. The main latch is configured to store the first, second, and third thresholds. The buffer is configured to store the first and second thresholds. The first trigger is used to activate the latch enable terminal of the main latch, facilitating the loading of threshold data by the main latch. The second trigger is used to maintain the activation signal, ensuring the detection state continues.

[0036] In this arc-induced pressure relief device, the environmental acquisition unit and the load acquisition unit first acquire a set of environmental and load data every first cycle. The host computer updates the first and second thresholds and outputs the first and second thresholds to the buffer to generate an update signal. The arc light sensing unit, the current sensing unit, and the pressure sensing unit acquire a set of arc light data, current data, and pressure data every second cycle. When the first identification unit determines that the arc light data is greater than the first threshold of the main latch, the first identification unit generates a detection command. After receiving the detection command, the second trigger outputs an activation signal, which is connected in parallel to the second identification unit. During the duration of the activation signal, if the second identification unit determines that the current data is greater than the second threshold of the main latch or the pressure data is greater than the third threshold of the main latch, it identifies an arc fault, outputs a high level to the actuator, and the actuator performs a pressure relief action. If the first identification unit determines that the arc light data is less than or equal to the first threshold of the main latch, or if no abnormal current or pressure data is detected during the duration of the activation signal, the first identification unit outputs a standby command, and the first trigger outputs a loading signal after receiving the standby command. The master latch reads the first and second thresholds from the buffer based on the load and update signals to complete the threshold update. Example 4

[0037] This embodiment discloses a preferred arc-induced pressure relief device. This device employs a simpler comparator (logic judgment circuit) and AND / OR gate circuits. The circuit response time is controlled by the level state of a flip-flop, avoiding the need for host computer chip control software. Compared to control software, the circuit structure of this embodiment can achieve millisecond-level response, enabling faster identification of arcing phenomena and timely pressure relief.

[0038] The first identification unit includes a first comparator, a hysteresis resistor, and a positive feedback resistor. The non-inverting input of the first comparator is connected to the arc light sensing unit, and the inverting input of the first comparator is connected to the arc light storage module of the main latch via a hysteresis resistor. If the arc light data of the arc light sensing unit is greater than the first threshold of the arc light storage module, a high level is output. The first comparator can be an LM393 comparator or a TLV3201 comparator. The positive feedback resistor can be selected from 10kΩ to 100kΩ, and the hysteresis resistor can be selected from 1kΩ to 100kΩ. The output of the first comparator is connected to the inverting input via a positive feedback resistor. The high level output is accumulated to the input through the positive feedback resistor to avoid repeated jumps in the output level when the arc light data is close to the first threshold. The output of the first comparator and the output of the second flip-flop are connected to a first OR gate module.

[0039] The second identification unit includes two sets of second comparators and second OR gate modules. One second comparator's non-inverting input is connected to current data, its inverting input is connected to the current storage module of the main latch, and its output is connected to the second OR gate module. The other second comparator's non-inverting input is connected to pressure data, its inverting input is connected to the pressure storage module of the main latch, and its output is connected to the second OR gate module. The second comparators can be low-cost TC75W71FU comparators. The second OR gate module is, for example, an SN74LVC1G32 OR gate. The SN74LVC1G32's high output drive current of 32mA can directly drive the subsequent first AND gate module. The first AND gate module is, for example, an SN74LVC1G08 AND gate, which, like the SN74LVC1G32, belongs to TI's LVC series. Their supply voltage, propagation delay, and drive capability are fully matched, and their logic levels meet compatibility requirements when used together. The outputs of the second OR gate module and the first OR gate module are connected to a first AND gate module, and the output of the first AND gate module is connected to an actuator. Actuators include relays, pressure relief valves, and circuit breakers. Thus, within a certain period after the arc light data reaches the threshold, when the current or pressure data reaches the threshold, a high-level output is triggered.

[0040] The first trigger includes an inverter, a second AND gate module, and a rising edge detection circuit. The standby command is input to the second AND gate module via the inverter, and the update signal from the host computer is also input to the second AND gate module. The output of the second AND gate module is connected to the rising edge detection circuit, and the output of the rising edge detection circuit is connected to the latch switch of the main latch. The inverter is used to output a signal opposite to that of the first comparator and can be a single-channel inverter (SN74LVC1G04). The rising edge detection circuit outputs a high level when the input rises from a low level to a high level, and is typically composed of a delay unit, an SN74LVC1G04 inverter, and an SN74LVC1G08 AND gate. The latch switch is the latch enable terminal of the main latch and can be implemented using internal pin logic. When the latch switch input is high, the latch enable terminal of the main latch is active, and data can be read from the buffer.

[0041] The second trigger includes a monostable circuit, a timing resistor, and a timing capacitor. The detection command from the first comparator is input to the rising edge of the monostable circuit. The timing resistor and timing capacitor are connected to the resistor timing terminal and capacitor timing terminal of the monostable circuit, respectively. The output of the monostable circuit and the first comparator are connected to a first OR gate module. The monostable circuit can be an NE555 analog delay circuit, which has a built-in Schmitt trigger for strong anti-interference capability and low power consumption. When the rising edge of the detection command arrives, the output of the monostable circuit immediately flips to a high level and maintains it precisely for a duration before automatically returning to a low level. This activation duration is determined by the external timing resistor and timing capacitor. In a preferred embodiment, the timing resistor can be adjusted via a host computer; the timing resistor is, for example, an AD5293 digital potentiometer. External signals can change the actual output resistance through potentiometer taps. Due to the difficulty of adjusting the capacitor, this embodiment only adjusts the timing resistor; a fixed capacitor can be used for the timing capacitor.

[0042] The host computer is located away from the cable room and can be a microcontroller installed in the instrument room. The host computer includes a human-machine interface, an input interface, a data processing module, a first storage management module, a second storage management module, a first output control module, and a second output control module. Unlike the first and second identification units, the host computer does not require millisecond-level response and its functionality can be implemented by programming an integrated chip. The human-machine interface is used to acquire input commands from the outside, and the input interface is used to acquire environmental and load data. The threshold update program can be programmed into the data processing module. The first storage management module outputs the updated values ​​of the first and second thresholds. The second storage management module outputs the updated value of the timing resistor. The first and second output control modules are used to output the data update status; that is, when the first storage management module outputs data, the first output control module provides a short-time high level, followed by a wide-time update signal from the first trigger. When the second storage management module outputs data, the second output control module provides a short-time high level, followed by a wide-time signal from the third trigger. In terms of physical structure, the input interface, data processing module, first memory management module, and second memory management module can be integrated into the microcontroller. The functions of different modules are implemented through programming. The microcontroller uses an embedded STM32F4 series microcontroller, employing RS-485 as the main communication interface and RS-232 as the debugging interface. The first and second output control modules can be implemented using communication transceivers, such as the ADM2587EBRWZ transceiver, for outputting short-time level signals. Example 5

[0043] The present invention further discloses a preferred embodiment of adjusting the duration of the activation signal after returning to step 3, which ensures timely identification of arcing after arcing occurs, and avoids the first identification unit losing the next arcing signal due to excessive activation time.

[0044] First, the pressure wave velocity is corrected based on the real-time temperature. Then, the pressure response time is updated based on the pressure wave velocity and the maximum arcing distance. The preset duration should satisfy the propagation time of the pressure signal. The pressure wave velocity v is corrected based on the real-time temperature from the environmental acquisition unit. sound (The velocity of sound at the current real-time temperature can be used as a substitute), pressure response time t2=d max / v sound +t margin . d max The maximum arcing distance is typically taken as the diagonal length of the cable room or the maximum straight-line distance from the cable joint to the pressure sensing unit. margin For margin, a range of 3–8 ms is used.

[0045] Then, the state transition durations from the detection state to the depressurization state in multiple sets during the historical arc recognition process are extracted. The duration of the activation signal is adjusted by combining the state transition duration and the pressure response duration. The maximum value t3 of the multiple historical state transition durations is extracted. The duration t of the activation signal is then determined. active =max(t2,t3)×k safe k safe For safety margin, k safe >1. To avoid frequent adjustments to the duration, t can be adjusted. active Perform low-pass filtering.

[0046] Finally, the updated timing resistor is calculated. This invention adjusts the sustaining time using a monostable circuit. In the monostable circuit, t... active =K EXT R EXT ×C EXT K EXT Refer to the monostable circuit manual; configuration is typically via chip pins. The timing capacitor C is usually... EXT The timing resistor R remains unchanged after the update. EXT =t active / (K EXT C EXT For the NE555 trigger, K EXT =1.1, C EXT= 1.0µF. If a 22ms duration is required, the updated timing resistor R... EXT =20kΩ.

[0047] like Figure 9 and Figure 10To adjust the duration of the activation signal, the arc-relieving device of this invention also includes an auxiliary latch and a third trigger. The host computer sends the updated value of the timing resistor or the updated value of the timing capacitor to the auxiliary latch. The host computer and the first identification unit are connected to the third trigger, which controls the read switch of the auxiliary latch. The structure of the third trigger can be the same as the first trigger. The third trigger can be an SN74LVC1G123 trigger, and the auxiliary latch can be an 8-bit SN74ACT373PWR latch. The host computer sends a high level to the third trigger, which generates a sufficiently wide time signal and connects to the latch pin (output enable terminal) of the auxiliary latch. The auxiliary latch then "snap down" the value at the data input terminal (pins D0-D7) and latches it to the output terminal (pins Q8-Q13). Unlike the main latch, the third trigger controls the read switch of the auxiliary latch, i.e., the output enable terminal (OutputEnable). The timing resistor update also needs to be isolated from arc detection. To ensure the wide-time signal can wait until the detection state ends, the width of the wide-time signal should be greater than the duration of the activation signal. After the host computer outputs the updated value of the timing resistor to the auxiliary latch, the third flip-flop is triggered to a high level, activating the output enable terminal of the auxiliary latch, and the auxiliary latch outputs the updated value to the timing resistor.

[0048] 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 and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for identifying arcing in the cable compartment of a switchgear, characterized in that, Includes the following steps: Step 1: Obtain the structural data and design objectives of the cable room, and initialize the first threshold, second threshold, and third threshold; Step 2: Collect a set of environmental and load data for the cable room at each interval of the first cycle, update the first threshold and the second threshold, and output the first threshold and the second threshold to the buffer to generate an update signal; Step 3: Collect a set of arc light data, current data, and pressure data every second cycle. If the arc light data is greater than the first threshold of the main latch, generate an activation signal and proceed to step 4; otherwise, generate a loading signal and proceed to step 7. Step 4: Enter the detection state. If the current data is greater than the second threshold of the main latch or the pressure data is greater than the third threshold of the main latch, proceed to step 5; otherwise, proceed to step 6. Step 5: Enter the depressurization state, identify the arcing fault and execute the depressurization action to end the task; Step 6: If the activation signal ends, return to step 2; otherwise, repeat step 4. Step 7: Enter standby mode. The main latch reads the first threshold and the second threshold from the buffer based on the load signal and the update signal, and returns to step 2.

2. The arc detection method for the cable compartment of a switchgear according to claim 1, characterized in that, In step 1, the structural data includes the minimum arcing distance, free volume, and cabinet reflection coefficient of the cable compartment. The design objectives include rated voltage and short-circuit capacity. The arcing illuminance is calculated based on the minimum arcing distance, and the first threshold is initialized by combining the cabinet reflection coefficient and the arcing illuminance. Calculate the minimum two-phase short-circuit current based on the rated voltage and short-circuit capacity, and initialize the second threshold based on the product of a sensitivity coefficient and the minimum two-phase short-circuit current; calculate the power density based on the minimum two-phase short-circuit current and free volume, and then initialize the third threshold based on the duration of the second cycle and the power density.

3. The arc detection method for the cable compartment of a switchgear according to claim 2, characterized in that, In step 2, the environmental data includes real-time temperature and real-time humidity. The temperature correction factor is updated by the real-time temperature, and the humidity correction factor is updated by the real-time humidity. Then, the first threshold is updated. The load data is the maximum load current in the current first cycle. The larger value of the product of the maximum load current and the minimum two-phase short-circuit current is updated as the second threshold.

4. The arc detection method for the cable compartment of a switchgear according to claim 1, characterized in that, In step 3, multiple sets of state transition durations from the detection state to the depressurization state are extracted. The pressure wave velocity is corrected according to the real-time temperature. The pressure response duration is then updated according to the pressure wave velocity and the maximum arc distance. The duration of the activation signal is adjusted by combining the state transition duration and the pressure response duration.

5. An arc-relief device for implementing the arc identification method for the cable compartment of a switchgear as described in claim 1, characterized in that, include: The arc light sensing unit is configured to collect arc light data from the cable compartment; The current sensing unit is configured to collect current data from the cable compartment; The pressure sensing unit is configured to collect pressure data from the cable compartment. The master latch is configured to store the first threshold, the second threshold, and the third threshold. The first identification unit is configured to generate detection commands or standby commands based on arc light data; The second identification unit is configured to generate a pressure relief command based on detection commands, current data, or pressure data. The actuator is configured to perform a pressure relief action based on a pressure relief command; The environmental data acquisition unit is configured to collect environmental data from the switchgear. The load acquisition unit is configured to acquire load data from the switchgear. The host computer is configured to update the first threshold and the second threshold based on environmental data and load data; The cache is configured to store the first threshold and the second threshold; and the first flip-flop and the second flip-flop, wherein, After the host computer outputs the first threshold and the second threshold, it generates an update signal. After the first trigger receives the standby command, it outputs a load signal. The main latch reads the first threshold and the second threshold from the buffer based on the load signal and the update signal. After the second trigger receives the detection command, it outputs an activation signal, which is sent to the output of the second identification unit.

6. The arc-relieving device according to claim 5, characterized in that, The first identification unit includes a first comparator, a hysteresis resistor, and a positive feedback resistor. The non-inverting input of the first comparator is connected to the arc light sensing unit. The inverting input of the first comparator is connected to the arc light storage module of the main latch via a hysteresis resistor. The output of the first comparator is connected to the inverting input via a positive feedback resistor. The output of the first comparator and the output of the second flip-flop are connected to a first OR gate module.

7. The arc-relieving device according to claim 6, characterized in that, The second identification unit includes two sets of second comparators and second OR gate modules. The non-inverting input of one second comparator is connected to a current sensing unit, the inverting input is connected to the current storage module of the main latch, and the output is connected to the second OR gate module. The non-inverting input of the other second comparator is connected to a pressure sensing unit, the inverting input is connected to the pressure storage module of the main latch, and the output is connected to the second OR gate module. The output of the second OR gate module and the output of the first OR gate module are connected to a first AND gate module, and the output of the first AND gate module is connected to an actuator.

8. The arc-relieving device according to claim 7, characterized in that, The first trigger includes an inverter, a second AND gate module, and a rising edge detection circuit. The standby command of the first comparator is input to the second AND gate module via the inverter. The update signal of the host computer is input to the second AND gate module. The output of the second AND gate module is connected to the rising edge detection circuit. The output of the rising edge detection circuit is connected to the latch switch of the main latch.

9. The arc-relieving device according to claim 8, characterized in that, The second flip-flop includes a monostable circuit, a timing resistor, and a timing capacitor. The detection command of the first comparator is input to the rising edge of the monostable circuit. The timing resistor and the timing capacitor are respectively connected to the resistor timing terminal and the capacitor timing terminal of the monostable circuit. The output terminal of the monostable circuit and the first comparator are connected to the first OR gate module.

10. The arc-relieving device according to claim 9, characterized in that, It also includes an auxiliary latch and a third trigger. The host computer sends the updated value of the timing resistor or the updated value of the timing capacitor to the auxiliary latch. The host computer and the first identification unit are connected to the third trigger, which controls the read switch of the auxiliary latch.

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