Intelligent reconstruction method for secondary protection system of low-voltage power distribution cabinet

Abstract

The application provides a low-voltage power distribution cabinet secondary protection system intelligent transformation method, and relates to the technical field of electrical system transformation, which comprises the following steps: based on the target power distribution cabinet state evaluation result, a transformation technical scheme is formulated; power-off operation is performed, old parts are removed, new circuit breakers, intelligent protectors and anti-misoperation devices are installed, new wires are laid according to process standards to construct a secondary circuit system; according to the equipment type and working condition, the intelligent protectors and anti-misoperation devices are subjected to differentiated setting of protection parameters, and item-by-item function debugging is performed through simulation of various faults; insulation and grounding resistance tests are performed on the secondary circuit system, after confirming that the tests meet the standards, power-on load trial operation is performed, electrical parameters are monitored and recorded, the function of the intelligent monitoring device is verified, and comprehensive performance confirmation is completed based on the acceptance standard. The above method is comprehensive and accurate in protection function, realizes fault early warning and rapid and accurate positioning, and the reliability of the secondary circuit can realize quantitative and verified guarantee.

Description

Technical Field

[0001] This invention relates to the field of electrical system renovation technology, and in particular to a method for intelligent renovation of a low-voltage distribution cabinet secondary protection system. Background Technology

[0002] In industrial power systems, the low-voltage motor control center (MCC) is a key node for power distribution and motor control. The reliability and intelligence level of its secondary protection system directly affect the safe and stable operation of downstream electrical equipment, especially important auxiliary equipment such as fans and pumps. As equipment service life increases, control technology iterates, and safety production standards continue to improve, the MCC switchgear put into operation in the early stages has gradually become unable to meet the stringent requirements of modern industry for power supply continuity and rapid fault response in terms of protection configuration, monitoring capabilities, and circuit reliability. Therefore, systematically and standardizedly improving the intelligence of secondary protection of existing MCC cabinets has become an important technical issue for ensuring the inherent safety of power systems and improving operation and maintenance efficiency.

[0003] However, in practice, the following prominent problems generally exist: First, traditional protection devices have single functions, poor operating accuracy, high failure rate, and lack coordination, which can easily lead to electrical cascading trips and expand the scope of power outages; Second, the system has weak monitoring capabilities and lacks real-time acquisition and intelligent analysis functions for electrical parameters. After a fault occurs, manual investigation is required, which is time-consuming and seriously affects the continuity of production; Third, due to long-term operation, secondary circuits generally have hidden dangers such as insulation aging and terminal corrosion, which directly affect the reliability of the protection function.

[0004] Therefore, a method for intelligent transformation of low-voltage distribution cabinet secondary protection systems that can systematically achieve comprehensive protection function coverage, precise operation, real-time monitoring, and high circuit reliability is urgently needed. Summary of the Invention

[0005] To address the shortcomings of the existing technologies, this invention provides an intelligent transformation method for the secondary protection system of low-voltage distribution cabinets, which solves the technical problems of single function, weak monitoring capability, and aging secondary circuits in the existing MCC cabinet protection devices.

[0006] This invention provides a method for intelligent upgrading of a low-voltage distribution cabinet secondary protection system, comprising: Based on the status assessment results of the existing protection system of the target distribution cabinet, the electrical components to be replaced and the intelligent monitoring devices to be added are identified, and a transformation technical plan is formulated according to the preset electrical safety specifications. The transformation technical plan includes wiring process standards, wiring process standards and differentiated settings of protection parameters. According to the aforementioned modification technical solution, a power outage operation is performed on the target distribution cabinet, the original circuit breaker, protection module and secondary circuit wires are removed, and a current-limiting high breaking capacity molded case circuit breaker, a motor intelligent protector and an anti-misoperation intelligent device are installed. Based on the aforementioned wiring process standard and the aforementioned connection process standard, new secondary circuit wires are laid to form a secondary circuit system. Based on the equipment type and operating conditions of the target power distribution cabinet, the protection parameters of the intelligent motor protector and the anti-misoperation intelligent device are set differently. By simulating various fault types, the secondary circuit system is debugged item by item. Insulation resistance and grounding resistance tests are performed on the secondary circuit system. After ensuring that the insulation performance and grounding reliability of the secondary circuit system meet the preset standards, a load test is conducted under power-on conditions to monitor and record electrical parameters, verify the real-time data acquisition, fault recording and remote transmission functions of the intelligent monitoring device, and confirm the comprehensive performance of the modified secondary circuit system based on the preset acceptance standards.

[0007] Optionally, the wiring process standards include: laying power circuits and signal circuits in layers within the target power distribution cabinet, with a laying interval of not less than 150mm; bending radius of all wires not less than 8 times the outer diameter, and securing them with cable ties every 300mm; and attaching waterproof wires to both ends of each wire.

[0008] Optionally, the wiring process standards include: after stripping the wires, using cold-pressed terminals for crimping, and ensuring the tensile force of the crimped terminals is not less than 80N; using a torque wrench to tighten the terminals, wherein for 2.5mm... 2 The wires are tightened to a torque of 1.2 N·m to 1.5 N·m; the phase and neutral wires of the leakage protection module are connected according to the markings; the voltage sampling lines of the intelligent motor protector are connected to the three phases L1, L2, and L3 respectively.

[0009] Optionally, after laying new secondary circuit wires based on the wiring process standard and the connection process standard to form a secondary circuit system, the method further includes: inspecting each secondary circuit wire in the secondary circuit system to ensure that the wire number of the secondary circuit wire corresponds to the drawing, the DC power supply and CT polarity are correct, and the terminal contacts are firmly in contact without loosening.

[0010] Optionally, the differentiated protection parameter settings include: for motor-type loads, setting an inverse-time overload protection curve based on the starting current multiple, operating current, and thermal capacity characteristics; for power distribution circuits, setting an instantaneous overcurrent protection setting based on the downstream load capacity and short-circuit current level.

[0011] Optionally, the step of simulating multiple fault types to perform item-by-item functional debugging of the secondary circuit system protection system includes: simulating at least two of the following faults: overcurrent, overload, leakage current, phase loss, and overvoltage, to perform item-by-item functional debugging of the secondary circuit system in order to verify the accuracy and response time of the secondary circuit system protection action.

[0012] Optionally, the step of performing item-by-item functional debugging on the secondary circuit system protection system includes: using a relay protection tester to simulate fault current and fault voltage, and verifying the action values ​​and action times of the motor intelligent protector for overcurrent, locked rotor, and unbalance protection item by item, requiring that the setting error does not exceed ±5% and the action time error does not exceed ±10%; and performing logic interlocking function testing on the anti-misoperation intelligent device to verify whether the closing permission logic of the anti-misoperation intelligent device under different working states complies with the five-prevention rules.

[0013] Optionally, the insulation resistance test of the secondary circuit system includes: after all secondary circuit wiring is completed and before power is applied, using a 500V insulation resistance tester to test the insulation resistance between the phase line and ground, the neutral line and ground, and the phase line and neutral line in the power supply circuit, requiring the resistance value to be not less than 2 MΩ; the insulation resistance of the communication signal circuit to the shell or shielding layer is not less than 5 MΩ.

[0014] Optionally, the step of conducting a load test run under power-on conditions to monitor and record electrical parameters and verify the real-time data acquisition, fault recording, and remote transmission functions of the intelligent monitoring device includes: acquiring and recording the three-phase current, voltage, power, power factor, and energy data of the motor in real time through the intelligent monitoring device; verifying the fault recording function of the intelligent monitoring device by simulating a momentary fault and checking whether the device can completely record electrical waveforms of no less than 10 cycles before and after the fault; and verifying the remote data transmission function to ensure that the monitoring data can be stably uploaded to the local monitoring backend or remote centralized control system.

[0015] Optionally, the comprehensive performance confirmation of the modified secondary circuit system based on preset acceptance criteria includes: when debugging the protection system of the secondary circuit system item by item, the error between the action time of the motor intelligent protector and the anti-misoperation intelligent device and the set value does not exceed ±10%; the measured value of the insulation resistance of the secondary circuit system is not less than 2 MΩ, and the measured value of the grounding resistance is not greater than 2Ω; the measured values ​​of the overcurrent action value, overload action time and leakage current of the motor intelligent protector do not exceed ±10% of their set values.

[0016] The intelligent transformation method for the secondary protection system of low-voltage distribution cabinets provided by this invention formulates a transformation technical solution based on the condition assessment results to implement differentiated setting of protection parameters. Specifically, it is customized according to the cabinet status and equipment type, ensuring the rationality of protection configuration from the source. Furthermore, by accurately adjusting the differentiated parameters of the intelligent motor protector and the anti-misoperation intelligent device, and simulating various faults for item-by-item debugging, the protection action value and action time can be accurately matched with the electrical characteristics of upstream and downstream equipment, realizing the selectivity and accuracy of protection. The entire transformation process not only updates the protection devices, but also builds a complete digital perception and diagnostic layer. By adding intelligent monitoring devices and verifying their functions in load-bearing trial operation, real-time visualization of electrical parameters, automatic recording and remote transmission of fault events are realized, forming intelligent analysis for fault location, significantly improving the efficiency of operation and maintenance response. By formulating and implementing wiring process standards and connection process standards, and conducting insulation resistance and grounding resistance tests, the physical reliability of the secondary circuit is doubly guaranteed, eliminating the hidden fault risks caused by wire insulation cracks and loose terminals, restoring the secondary circuit to a healthy and reliable state in the long term. The above method forms a multi-layered protection system with precisely configurable parameters, providing comprehensive and accurate protection. With the help of real-time data acquisition and remote transmission, maintenance personnel can remotely monitor the equipment status, achieve fault early warning and rapid and accurate location, and ensure the reliability of the secondary circuit through quantification and verification. Ultimately, it forms a standardized and replicable engineering technology method.

[0017] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings.

[0018] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0019] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the overall process of the intelligent transformation method of the secondary protection system of low-voltage distribution cabinet in one embodiment of this application. Detailed Implementation

[0020] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0021] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0022] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0023] This invention provides a method for intelligent upgrading of the secondary protection system of a low-voltage distribution cabinet, such as... Figure 1As shown, the method includes: based on the status assessment results of the existing protection system of the target distribution cabinet, determining the electrical components to be replaced and the intelligent monitoring devices to be added, and formulating a modification technical plan according to the preset electrical safety specifications. The modification technical plan includes wiring process standards, connection process standards, and differentiated settings of protection parameters. According to the modification technical plan, a power outage operation is performed on the target distribution cabinet, removing the original circuit breakers, protection modules, and secondary circuit wires, and installing current-limiting high-breaking capacity molded case circuit breakers, motor intelligent protectors, and anti-misoperation intelligent devices. New secondary circuit wires are laid based on the wiring process standards and connection process standards to form a secondary circuit. Secondary circuit system: Based on the equipment type and operating conditions of the target distribution cabinet, differentiated protection parameters are set for the motor intelligent protector and anti-misoperation intelligent device. By simulating various fault types, the secondary circuit system is functionally debugged item by item. Insulation resistance and grounding resistance tests are performed on the secondary circuit system. After ensuring that the insulation performance and grounding reliability of the secondary circuit system meet the preset standards, a load test is conducted under power-on conditions to monitor and record electrical parameters, verify the real-time data acquisition, fault recording and remote transmission functions of the intelligent monitoring device, and confirm the comprehensive performance of the modified secondary circuit system based on the preset acceptance standards.

[0024] The intelligent transformation method for the secondary protection system of low-voltage distribution cabinets provided by this invention formulates a transformation technical solution based on the condition assessment results to implement differentiated setting of protection parameters. Specifically, it is customized according to the cabinet status and equipment type, ensuring the rationality of protection configuration from the source. Furthermore, by accurately adjusting the differentiated parameters of the intelligent motor protector and the anti-misoperation intelligent device, and simulating various faults for item-by-item debugging, the protection action value and action time can be accurately matched with the electrical characteristics of upstream and downstream equipment, realizing the selectivity and accuracy of protection. The entire transformation process not only updates the protection devices, but also builds a complete digital perception and diagnostic layer. By adding intelligent monitoring devices and verifying their functions in load-bearing trial operation, real-time visualization of electrical parameters, automatic recording and remote transmission of fault events are realized, forming intelligent analysis for fault location, significantly improving the efficiency of operation and maintenance response. By formulating and implementing wiring process standards and connection process standards, and conducting insulation resistance and grounding resistance tests, the physical reliability of the secondary circuit is doubly guaranteed, eliminating the hidden fault risks caused by wire insulation cracks and loose terminals, restoring the secondary circuit to a healthy and reliable state in the long term. The above method forms a multi-layered protection system with precisely configurable parameters, providing comprehensive and accurate protection. With the help of real-time data acquisition and remote transmission, maintenance personnel can remotely monitor the equipment status, achieve fault early warning and rapid and accurate location, and ensure the reliability of the secondary circuit through quantification and verification. Ultimately, it forms a standardized and replicable engineering technology method.

[0025] Specifically, in the above embodiments, the wiring process standards include: in the target power distribution cabinet, the power circuit and signal circuit are laid in layers with a laying interval of not less than 150mm; the bending radius of all wires is not less than 8 times the outer diameter, and they are fixed with cable ties every 300mm; and waterproof wire numbers are pasted on both ends of each wire.

[0026] In this implementation, the core of the cabling process standard lies in ensuring the reliability and long-term stability of the secondary circuit's physical structure through three quantifiable and verifiable process requirements. First, the power circuit and signal circuit are laid in layers with a spacing of no less than 150mm. This aims to effectively attenuate the interference of the strong electromagnetic field of the power circuit on the weak signal circuit by utilizing spatial distance, which is a key anti-interference measure to ensure the accuracy of intelligent monitoring data. Second, the bending radius of all conductors is no less than 8 times the outer diameter, and cable ties are used every 300mm to fix the conductors to prevent damage to the internal core wires when bending. Regular fixing also prevents wear or loosening due to vibration, improving mechanical strength. Finally, waterproof wire markings are affixed to both ends of each conductor, providing clear and permanent routing identification for construction, commissioning, and future maintenance. This is the foundation for accurate wiring and efficient fault diagnosis. The above cabling standards together constitute the physical basis of a highly reliable secondary circuit.

[0027] Specifically, in the above embodiments, the wiring process standards include: after stripping the wires, using cold-pressed terminals for crimping, and the tensile force of the crimped terminals is not less than 80N; using a torque wrench to tighten the terminals, wherein, for 2.5mm... 2 The wires should be tightened to a torque of 1.2 N·m to 1.5 N·m; the phase and neutral wires of the leakage protection module should be connected according to the markings; the voltage sampling lines of the motor intelligent protector should be connected to the three phases L1, L2, and L3 respectively.

[0028] In this embodiment, the wiring process standard focuses on the mechanical reliability and electrical correctness of the electrical connection. First, after stripping the wires, cold-pressed terminals are used for crimping, and the tensile force of the crimped terminals is not less than 80N. This ensures that the connection between the wires and terminals has sufficient mechanical strength to resist the electrodynamic forces and vibrations during long-term operation, preventing loose connections or disconnections. Second, a torque wrench is used to tighten the terminals. Through quantitative control of the tightening torque, it can ensure stable contact resistance and low heat generation, while preventing damage to terminals or wires due to excessive tightening. Third, the phase and neutral wires of the leakage protection module are connected according to the markings to ensure the normal operation of its leakage detection function. The voltage sampling lines of the motor intelligent protector are connected to the three phases L1, L2, and L3 respectively, which is a necessary condition for realizing accurate protection functions such as phase loss and voltage imbalance. This standard system comprehensively ensures the reliability of the secondary circuit electrical performance from connection strength, contact quality to wiring logic.

[0029] Specifically, in the above embodiments, after laying new secondary circuit wires based on wiring process standards and connection process standards to form a secondary circuit system, the method further includes: inspecting each secondary circuit wire in the secondary circuit system to ensure that the wire number of the secondary circuit wire corresponds to the drawing, that the DC power supply and CT polarity are correct, and that the wiring terminals are firmly in contact without loosening.

[0030] In this implementation, a crucial intermediate inspection and process verification step is introduced between the system construction and debugging steps. This step requires a specific inspection of each secondary circuit that has been laid and wired. The inspection points cover three aspects: First, check that the wire numbers correspond to the drawings to ensure that the actual wiring is completely consistent with the design schematic and prevent incorrect connections; second, check that the DC power supply and CT polarity are correct, as this involves the power supply logic and current sampling direction of the protection device. Incorrect polarity will directly lead to protection logic disorder or failure to operate; third, check that the wiring terminals are firmly in contact without looseness, which is the final verification of the wiring process. This step, as a quality control node, aims to systematically eliminate human error and process omissions, ensuring that the correctness and robustness of the physical circuit have been verified before entering the complex parameter setting and functional debugging, thereby significantly improving the efficiency of subsequent debugging and the first-time success rate.

[0031] Specifically, in the above embodiments, the differentiated setting of protection parameters includes: for motor-type loads, setting an inverse-time overload protection curve based on the starting current multiple, operating current and thermal capacity characteristics; for power distribution circuits, setting an instantaneous overcurrent protection setting based on the downstream load capacity and short-circuit current level.

[0032] In this embodiment, the differentiated protection parameters are precisely set based on the electrical characteristics of the protected object. For motor-type loads, there is a significant inrush current (multiple of the starting current) during the starting process, and overload may occur during operation. Therefore, an inverse-time overload protection curve is set to simulate the heating characteristics of the motor. The action time is shorter when the overload current is larger, and a longer running time is allowed under slight overload. This protects the motor from overheating damage and avoids unnecessary tripping. For distribution circuits, such as feeder switches, multiple loads may be connected downstream. The main goal of protection is to quickly disconnect short-circuit faults. Therefore, an instantaneous overcurrent protection setting is set. This setting needs to be calculated based on the downstream load capacity and short-circuit current level to ensure that there is no delay in action when a short circuit occurs, quickly isolates the fault, and prevents the accident from escalating.

[0033] Specifically, in the above embodiments, the secondary circuit system protection system is debugged item by item by simulating various fault types, including: by simulating at least two of the faults of overcurrent, overload, leakage current, phase loss and overvoltage, the secondary circuit system is debugged item by item to verify the accuracy and response time of the secondary circuit system protection action.

[0034] In this embodiment, the scope of functional debugging is defined, and the types of faults that must be covered by the debugging are clarified. These fault types must include at least two of the following: overcurrent, overload, leakage current, phase loss, and overvoltage faults. This limitation requires that debugging not only verify a single type of fault but also conduct multi-scenario, composite functional tests. For example, simultaneously testing overcurrent and phase loss protection can verify the action logic and priority of the protection device under complex fault conditions. Through item-by-item functional debugging, the secondary circuit system can be comprehensively and systematically verified, especially the response capabilities of the motor intelligent protector and anti-malfunction intelligent device in the face of different electrical anomalies. The ultimate goal is to confirm that the accuracy and response time of its protection actions meet the design requirements, thereby establishing complete functional reliability before commissioning.

[0035] Specifically, in the above embodiments, the secondary circuit system protection system is debugged item by item, including: using a relay protection tester to simulate fault current and fault voltage, verifying the action values ​​and action times of the motor intelligent protector for overcurrent, locked rotor, and unbalance protection item by item, and requiring the setting error to not exceed ±5% and the action time error to not exceed ±10%; and conducting logic interlocking function tests on the anti-misoperation intelligent device to verify whether the closing permission logic of the anti-misoperation intelligent device under different working states complies with the five-prevention rules.

[0036] In this embodiment, the execution method and accuracy requirements for functional debugging are further specified. First, for the debugging of the motor intelligent protector, it is stipulated that a relay protection tester must be used to simulate fault current and fault voltage. This is a standardized and high-precision testing method that can accurately output simulated fault signals. The debugging items include overcurrent, locked rotor, and unbalance (phase loss) protection, and the action value and action time of each protection are verified item by item. More importantly, quantitative accuracy indicators are proposed, namely, the set value error does not exceed ±5% and the action time error does not exceed ±10%. This is not only the debugging target, but also constitutes the acceptance standard for the performance of the intelligent protector, ensuring the accuracy of protection. Second, the debugging of the anti-misoperation intelligent device focuses on the logic interlocking function test, that is, verifying whether its closing permission logic in different working states such as operation, testing, and maintenance complies with the five-prevention rules, namely preventing the accidental opening and closing of circuit breakers, preventing the opening and closing of disconnecting switches under load, etc., effectively ensuring operational safety and preventing human error.

[0037] Specifically, in the above embodiments, the insulation resistance test of the secondary circuit system includes: after all the secondary circuit wiring in the secondary circuit system is completed and before power is applied, using a 500V insulation resistance tester to test the insulation resistance between the phase line and ground, the neutral line and ground, and the phase line and neutral line in the power supply circuit, requiring the resistance value to be not less than 2MΩ; the insulation resistance of the communication signal circuit to the shell or shielding layer is not less than 5MΩ.

[0038] In this embodiment, the testing is limited to the final electrical isolation performance check after all secondary circuit wiring is completed and before power-on, ensuring safe power supply. A 500V insulation resistance tester is used, specifically the standard test voltage applicable to low-voltage secondary circuits. The test scope covers critical circuits: firstly, the insulation resistance between phase line to ground (L-PE), neutral line to ground (N-PE), and phase line to neutral line (LN) in the power supply circuit, which is required to be no less than 2MΩ. This standard ensures the insulation strength of the power supply circuit itself and to ground, preventing leakage or short circuits; secondly, the insulation resistance of the communication signal circuit to the outer casing or shielding layer is required to be no less than 5MΩ. Higher requirements aim to prevent signal interference or leakage due to poor insulation. The above two tests together establish a reliable electrical isolation barrier for the secondary circuit system.

[0039] Specifically, in the above embodiments, a load test run is performed under energized conditions to monitor and record electrical parameters, verifying the real-time data acquisition, fault recording, and remote transmission functions of the intelligent monitoring device. This includes: real-time acquisition and recording of the motor's three-phase current, voltage, power, power factor, and energy data through the intelligent monitoring device; verification of the intelligent monitoring device's fault recording function by simulating a momentary fault and checking whether the device can completely record electrical waveforms for at least 10 cycles before and after the fault; and verification of the remote data transmission function to ensure that the monitoring data can be stably uploaded to the local monitoring backend or remote centralized control system.

[0040] This implementation clarifies the verification content of the intelligent monitoring device's functions during the load-bearing trial operation phase, entering the level of in-depth data and functional verification. Firstly, real-time acquisition and recording of the motor's three-phase current, voltage, power, power factor, and energy data verifies the completeness and accuracy of the monitoring device's basic data acquisition and metering functions. Secondly, verification of the fault recording function involves simulating a transient fault and checking whether the device can completely record electrical waveforms for at least 10 cycles before and after the fault. This is crucial for post-fault analysis of complex fault causes; a recording capability of more than 10 cycles can capture transient data throughout the entire process of fault occurrence, development, and protection actions. Thirdly, verification of the remote data transmission function ensures that data can be stably uploaded to the local monitoring backend or remote centralized control system, which is the foundation for achieving remote monitoring and intelligent operation and maintenance. These three verifications collectively ensure the effective functioning of the intelligent monitoring device and the availability of data, achieving the intelligent transformation goal.

[0041] Specifically, in the above embodiments, the comprehensive performance of the modified secondary circuit system is confirmed based on preset acceptance criteria, including: when debugging the protection system of the secondary circuit system item by item, the error between the action time of the motor intelligent protector and the anti-misoperation intelligent device and the set value does not exceed ±10%; the measured value of the insulation resistance of the secondary circuit system is not less than 2MΩ, and the measured value of the grounding resistance is not greater than 2Ω; the measured values ​​of the overcurrent action value, overload action time and leakage current of the motor intelligent protector do not exceed ±10% of their set values.

[0042] In this implementation, the comprehensive performance verification is concretized into a series of quantifiable acceptance criteria. First, the timing accuracy of protection actions requires that the error between the action time and the set value during commissioning not exceed ±10%. Second, the electrical safety indicators of the circuit itself require that the measured insulation resistance not be less than 2MΩ and the measured grounding resistance not be greater than 2Ω. Third, the setting accuracy of core protection parameters requires that the measured values ​​of overcurrent action value, overload action time, and leakage current action current all have an error of no more than ±10% from their set values. These standards are all objective and measurable technical indicators, collectively constituting the final technical basis for judging the success of the renovation project. Specifically, the renovation effect is transformed from subjective evaluation to objective data comparison, ensuring that each renovation achieves uniform and high-level quality requirements, and realizing a targeted closed-loop solution to the background technical problems.

[0043] This application provides an embodiment of an intelligent transformation method for a low-voltage switchgear secondary protection system: First, a status assessment was conducted on the existing protection system of the target distribution cabinet (i.e., multiple drawer switch cabinets of the Phase III desulfurization MCC). The assessment revealed that the traditional thermal-magnetic circuit breakers and simple motor protectors used in the original distribution cabinet had limited functions; the insulation layer of the secondary circuit wires was generally cracked, and the insulation resistance of the sampled test was less than 1MΩ; the oxidation corrosion rate of the wiring terminals was about 35%; there was no intelligent monitoring unit in the cabinet, and the fault diagnosis relied entirely on manual inspection.

[0044] Based on this assessment, the core contents of the renovation were determined to be: replacement of electrical components, replacing all the original circuit breakers with current-limiting high-breaking capacity molded case circuit breakers with communication functions; replacing all the original low-voltage motor integrated protectors with digital motor intelligent protectors; and adding intelligent monitoring devices, installing anti-misoperation intelligent devices in each drawer unit, and adding a local anti-misoperation intelligent monitoring backend in the power distribution room.

[0045] Subsequently, based on the "Code for Design of Low-Voltage Power Distribution" (GB50054-2011), the "Code for Design of Relay Protection and Automatic Devices for Power Installations" (GB / T50062-2008), and the "Code for Construction and Acceptance of Low-Voltage Electrical Equipment in Electrical Installation Engineering" (GB50254-2014), a detailed renovation technical plan was formulated, which clarified the following core standards: According to wiring standards, power circuits (AC220V) and signal circuits (RS485) must be laid in layers within the cabinet, with a minimum parallel spacing of 150mm. Shielded cables must be used for signal circuits, with the shield grounded at one end on the monitoring backend side. The bending radius of the conductors must be at least eight times their outer diameter, and they must be secured with nylon cable ties every 300mm. Waterproof wire numbers must be affixed to both ends of all conductors in the format "Circuit Number-Terminal Number," such as M1-L1-101, to ensure compliance with electrical principles. Figure 1 One-to-one correspondence.

[0046] Wiring process standards: wire stripping length controlled at 6-8mm; cold-pressed terminals used for crimping; crimping point tension required not less than 80N; use a measured torque wrench to tighten terminals; for wires with a cross-section of 2.5mm², tightening torque set to 1.2N·m to 1.5N·m; leakage protection modules must strictly distinguish between phase wire (L) and neutral wire (N) connection; voltage sampling lines of motor intelligent protectors must be correctly connected to the three phases L1, L2, and L3.

[0047] The protection parameter differentiation setting strategy is based on the technical files of the load equipment. For motor loads such as fans and water pumps, the inverse time overload protection characteristics are set in the motor intelligent protector according to their starting current multiple (such as 6-8 times the rated current) and thermal capacity curve. For feeder circuits, the instantaneous overcurrent protection setting value is set according to the downstream calculated load and short-circuit current.

[0048] Replacement standards for aging components: All wires with insulation resistance test values ​​below 2MΩ or with visible cracks shall be replaced; all terminals with corrosion, deformation or tightening torque less than 1.0N·m shall be replaced.

[0049] Before construction, safety barriers were set up in the work area, and insulated gloves, voltage detectors, and fire extinguishers were provided. The specific implementation was carried out according to the following steps: Power outage and verification (approx. 30 minutes / cabinet): Confirm the power outage area according to the work order, complete the power outage operation, and verify the voltage is correct before removing the target drawer switch; Old component removal and cleaning (approx. 60 minutes / cabinet): Record the original wiring method, remove the old circuit breaker, protector, and all aging secondary wires. Thoroughly clean the dust inside the cabinet and check the reliability of the cabinet grounding; New component installation and wiring (approx. 90 minutes / cabinet): Install new intelligent molded case circuit breakers, intelligent motor protectors, and anti-misoperation intelligent devices. Strictly adhere to the aforementioned wiring process standards when laying new secondary circuit wires, ensuring they are horizontally and vertically aligned and securely bound. Wiring and intermediate checks (approximately 90 minutes / cabinet): Wiring is performed according to the schematic diagram. After each circuit is completed, a continuity test is conducted using a multimeter. After all wiring is completed, a three-step intermediate check is performed: 1. All wire numbers correspond exactly to the diagram; 2. The polarity of the DC power supply and the current transformer (CT) polarity are correct; 3. Each terminal block is securely connected and free from looseness. Parameter setting and function debugging: According to the preset strategy, parameters for each motor intelligent protector and anti-misoperation intelligent device are set using dedicated software or a control panel. Subsequently, a relay protection tester is used to simulate faults and perform item-by-item debugging. For faults such as current leakage, stall, and phase loss (imbalance), verify that the operating value error of the motor intelligent protector does not exceed ±5% and the operating time error does not exceed ±10%; simulate different cabinet states to verify the accuracy of the five-proof logic interlocking function of the anti-misoperation intelligent device; insulation and grounding test (approximately 60 minutes / cabinet): before power-on, use a 500V insulation resistance tester to test the secondary circuit; the test results show that the insulation resistance of all power circuits (LN, L-PE, N-PE) is greater than 2MΩ, and the insulation resistance of all communication signal circuits to the shielding layer is greater than 5MΩ. Using a grounding resistance tester, the grounding resistance of the protective grounding (PE) busbar is measured to be 1.5Ω, which meets the requirement of not exceeding 2Ω.

[0050] After completing the above steps, a power-on test run was conducted. First, a 30-minute no-load test run was performed, and the voltage and current of each circuit were monitored and found to be normal, with the data refresh of the intelligent monitoring device being smooth. Then, a 2-hour load test run was conducted. During this period, the intelligent monitoring device collected and recorded parameters such as the three-phase current, voltage, power, and energy of the motor in real time. A momentary ground fault was simulated, and the intelligent monitoring device accurately triggered and recorded electrical waveforms of no less than 10 cycles before and after the fault. All operational data was stably uploaded to the local monitoring backend. Finally, comprehensive performance was confirmed according to preset acceptance standards. For the main control items, the protection function's accuracy rate was 100%, the insulation resistance and grounding resistance of the secondary circuits all met standards, and the measured errors of parameters such as the overcurrent setting and action time of the motor intelligent protector were all within ±10%. For general items, components were securely installed, clearly labeled, the wiring was neat and aesthetically pleasing, the wire numbers were accurate, the error between the displayed values ​​of the intelligent monitoring device and the measured values ​​of the on-site standard meters was less than 2%, and historical fault records could be queried and exported normally. Through the complete implementation of this embodiment, the target MCC cabinet successfully constructed a five-fold protection system for overcurrent, overload, leakage current, phase loss, and overvoltage, achieving the transformation goals of precise protection parameters, intelligent monitoring functions, and high reliability of the secondary circuits. The average fault location time was shortened from more than 4 hours to less than 30 minutes, and the circuit failure rate was significantly reduced, verifying the effectiveness, operability, and significant technical benefits of the method of this invention.

[0051] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for intelligent upgrading of a secondary protection system for a low-voltage distribution cabinet, characterized in that, include: Based on the status assessment results of the existing protection system of the target distribution cabinet, the electrical components to be replaced and the intelligent monitoring devices to be added are identified, and a transformation technical plan is formulated according to the preset electrical safety specifications. The transformation technical plan includes wiring process standards, wiring process standards and differentiated settings of protection parameters. According to the aforementioned modification technical solution, a power outage operation is performed on the target distribution cabinet, the original circuit breaker, protection module and secondary circuit wires are removed, and a current-limiting high breaking capacity molded case circuit breaker, a motor intelligent protector and an anti-misoperation intelligent device are installed. Based on the aforementioned wiring process standard and the aforementioned connection process standard, new secondary circuit wires are laid to form a secondary circuit system. Based on the equipment type and operating conditions of the target power distribution cabinet, the protection parameters of the intelligent motor protector and the anti-misoperation intelligent device are set differently. By simulating various fault types, the secondary circuit system is debugged item by item. Insulation resistance and grounding resistance tests are performed on the secondary circuit system. After ensuring that the insulation performance and grounding reliability of the secondary circuit system meet the preset standards, a load test is conducted under power-on conditions to monitor and record electrical parameters, verify the real-time data acquisition, fault recording and remote transmission functions of the intelligent monitoring device, and confirm the comprehensive performance of the modified secondary circuit system based on the preset acceptance standards.

2. The method according to claim 1, characterized in that, The wiring process standards include: Inside the target distribution cabinet, the power circuit and signal circuit are laid in layers, with a spacing of not less than 150mm. All wires must be bent to a radius no less than 8 times their outer diameter and secured with cable ties every 300 mm. Apply waterproof tape to both ends of each wire.

3. The method according to claim 1, characterized in that, The wiring process standards include: After the wires are stripped, cold-pressed terminals are used for crimping, and the tensile strength of the crimped terminals is not less than 80N. Use a torque wrench to tighten the terminals, especially for 2.5mm terminals. 2 For the conductor, the tightening torque is 1.2 N·m to 1.5 N·m; The phase and neutral wires of the leakage current protection module are connected according to the markings; The voltage sampling lines of the motor intelligent protector are respectively connected to the three phases L1, L2, and L3.

4. The method according to claim 1, characterized in that, After laying new secondary circuit conductors based on the wiring process standard and the connection process standard to form a secondary circuit system, the method further includes: Inspect each secondary circuit wire in the secondary circuit system to ensure that the wire number corresponds to the drawing, the DC power supply and CT polarity are correct, and the terminals are securely connected without looseness.

5. The method according to claim 1, characterized in that, The differentiated protection parameter settings include: For motor-type loads, an inverse-time overload protection curve is set based on the starting current multiple, operating current, and thermal capacity characteristics; For power distribution circuits, instantaneous overcurrent protection settings are set based on downstream load capacity and short-circuit current levels.

6. The method according to claim 1, characterized in that, The process of simulating various fault types to perform item-by-item functional debugging of the secondary circuit system protection system includes: The secondary circuit system is tested item by item by simulating at least two of the following faults: overcurrent, overload, leakage current, phase loss, and overvoltage, in order to verify the accuracy and response time of the protection action of the secondary circuit system.

7. The method according to claim 1, characterized in that, The step-by-step functional debugging of the secondary circuit system protection system includes: Using a relay protection tester to simulate fault current and fault voltage, the action values ​​and action times of the motor intelligent protector for overcurrent, locked rotor, and unbalance protection are verified item by item, and the setting error is required to be no more than ±5% and the action time error is required to be no more than ±10%. The logic interlocking function of the anti-misoperation intelligent device was tested to verify whether the closing permission logic of the anti-misoperation intelligent device under different working states complies with the five-prevention rules.

8. The method according to claim 1, characterized in that, The insulation resistance test of the secondary circuit system includes: After all the secondary circuit wiring in the secondary circuit system is completed and before power is applied, a 500V insulation resistance tester is used to test the insulation resistance between the phase line and ground, the neutral line and ground, and the phase line and neutral line in the power supply circuit. The resistance value is required to be no less than 2 MΩ. The insulation resistance of the communication signal circuit to the outer shell or shielding layer shall not be less than 5 MΩ.

9. The method according to claim 1, characterized in that, The process of conducting a load-bearing test run under power-on conditions to monitor and record electrical parameters, and to verify the real-time data acquisition, fault recording, and remote transmission functions of the intelligent monitoring device, includes: The intelligent monitoring device collects and records the motor's three-phase current, voltage, power, power factor, and energy data in real time. To verify the fault recording function of the intelligent monitoring device, simulate a momentary fault and check whether the device can completely record electrical waveforms of no less than 10 cycles before and after the fault. Verify the remote data transmission function to ensure that monitoring data can be stably uploaded to the local monitoring backend or remote centralized control system.

10. The method according to claim 1, characterized in that, The comprehensive performance verification of the modified secondary circuit system based on preset acceptance criteria includes: When performing item-by-item functional debugging of the secondary circuit system protection system, the error between the action time of the motor intelligent protector and the anti-misoperation intelligent device and the set value shall not exceed ±10%; The measured insulation resistance of the secondary circuit system is not less than 2 MΩ, and the measured grounding resistance is not greater than 2Ω. The measured values ​​of the overcurrent action value, overload action time, and leakage current of the motor intelligent protector do not exceed ±10% of their set values.

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