Low-voltage switchgear control circuit

Abstract

The utility model relates to a power distribution cabinet technical field discloses a kind of low-voltage power distribution cabinet control circuit, including incoming line cabinet, feeder cabinet, the inside of the incoming line cabinet is provided with first main bus, first main bus one end is connected with the cable under the cabinet bottom by the circuit breaker QF in incoming line cabinet, the cable under the cabinet bottom is used to introduce commercial power, the other end of first main bus is connected with branch bus, the inside of the feeder cabinet is provided with second main bus connected with branch bus, and second main bus respectively supplies power to multiple fire electrical branch and standby branch.The utility model in the circuit is introduced to branch power supply from commercial power, and hierarchical management and control are realized by main bus, branch bus and circuit breaker, the continuous power supply of important load such as fire protection is guaranteed, and through the design of energy storage, logic linkage of closing and opening, automatic tripping of fault, grounding protection and the like, misoperation and fault expansion are avoided.

Description

Technical Field

[0001] This utility model relates to the field of power distribution cabinet technology, and in particular to a control circuit for a low-voltage power distribution cabinet. Background Technology

[0002] In industrial production, commercial buildings, and residential communities, low-voltage switchgear serves as the core equipment for power distribution and control. It plays a crucial role in converting high-voltage mains power into low-voltage electrical energy and distributing it to various electrical loads (such as lighting, power equipment, and fire protection systems). Its operational stability directly affects electrical safety and the order of production and daily life. Therefore, it is necessary to develop a low-voltage switchgear control circuit.

[0003] With the continuous growth of social electricity demand, the capacity and complexity of power distribution systems are constantly increasing. Traditional low-voltage switchgear control circuits are gradually revealing various limitations. Traditional control circuits primarily rely on manual control for operations such as energy storage and switching on / off, lacking status linkage and visual indication, making it difficult to meet the reliability requirements of intelligent monitoring systems. Utility Model Content

[0004] To overcome the above shortcomings, this utility model provides a low-voltage distribution cabinet control circuit, which aims to improve the problem that the energy storage, closing and opening operations of traditional control circuits in the prior art are mostly single manual control, lacking status linkage and visual indication, and making it difficult to meet the reliability requirements of intelligent monitoring systems.

[0005] To achieve the above objectives, this utility model provides the following technical solution: a low-voltage distribution cabinet control circuit, including an incoming line cabinet and a feeder cabinet. The incoming line cabinet has a first main busbar inside. One end of the first main busbar is connected to a bottom-mounted cable via a circuit breaker QF inside the incoming line cabinet. The bottom-mounted cable is used to introduce mains power. The other end of the first main busbar is connected to a branch busbar. The feeder cabinet has a second main busbar inside, connected to the branch busbar. The second main busbar supplies power to multiple fire-fighting power branches and backup power branches. Each fire-fighting power branch and backup power branch is equipped with... The device includes a circuit breaker (QF) and a multi-function monitoring meter (PM). The current signal acquisition terminal of the multi-function monitoring meter (PM) is connected to the secondary winding of a current transformer. The primary winding of the current transformer is connected in series in the three-phase line of the fire-fighting power supply branch. The multi-function monitoring meter (PM) is connected to the three-phase line of the corresponding branch through the current transformer to acquire current signals, and connected to the three-phase power supply line to acquire voltage signals. The multi-function monitoring meter (PM) is equipped with an RS485 communication interface for data transmission. The three-phase lines of both the fire-fighting power supply branch and the backup branch are connected to a PE busbar for grounding protection.

[0006] Preferably, the incoming line cabinet is equipped with a secondary control circuit, which includes a power supply circuit, an energy storage control and indication circuit, a closing control circuit, a opening control circuit, an opening and closing indication circuit, and a fault feedback circuit. In the energy storage control and indication circuit, the indicator light HW is connected to the energy storage unit of the circuit breaker QF to indicate the energy storage status. In the opening and closing control circuit, the closing button SF1 is connected to the closing unit of the circuit breaker QF to control closing, and the opening button SF2 is connected to the opening unit of the circuit breaker QF to control opening. In the opening and closing indication circuit, the opening indicator light HG and the closing indicator light HR are connected through the auxiliary contacts of the circuit breaker QF to indicate the opening and closing status of the circuit breaker QF.

[0007] Preferably, the phase line L1 in the power supply circuit is connected to a fuse FU4 for leading out a line to provide power to the secondary control circuit, and the neutral line N in the power supply circuit serves as the circuit neutral line.

[0008] Preferably, the energy storage control and indication circuit includes an energy storage indicator light HW, one end of which is connected to a fuse FU4 and the other end to terminal B3 of a circuit breaker QF. The energy storage motor MCH inside the circuit breaker QF is connected in series with the energy storage contact CH, one end of which is connected to terminal B2 of the circuit breaker QF and the other end to terminal B1. The closing control circuit includes a closing button SF1, one end of which is connected to the fuse FU4 and the other end to terminal A2 of the circuit breaker QF. One end of the closing coil XF inside the circuit breaker QF is connected to terminal A2 and the other end to terminal A1.

[0009] Preferably, the tripping control circuit includes a tripping button SF2, one end of which is connected to a fuse FU4, and the other end is connected to terminal C2 of circuit breaker QF. One end of the tripping coil MX inside circuit breaker QF is connected to terminal C2, and the other end is connected to terminal C1. The tripping / closing indication circuit includes a tripping indicator light HG and a closing indicator light HR. One end of the tripping indicator light HG is connected to fuse FU4, and the other end is connected to terminal 12 of circuit breaker QF. One end of the closing indicator light HR is connected to fuse FU4, and the other end is connected to terminal 14 of circuit breaker QF. The tripping auxiliary contact OF1 inside the circuit breaker QF is connected to terminals 12 and 14 at one end and terminal 11 at the other end. Terminals B1, A1, C1, and 11 of the circuit breaker QF are all connected to the neutral line N. The closing auxiliary contact OF2 inside the circuit breaker QF is connected to terminals 22 and 24 at one end and terminal 21 at the other end. The fault feedback contact SDE in the fault feedback circuit is connected to terminals 82 and 84 at one end and terminal 81 at the other end. Terminals 22, 24, and 127 of the circuit breaker QF, as well as terminals 82, 84, and 127, are respectively connected to different line numbers of the secondary control circuit.

[0010] Preferably, the multi-functional monitoring meter PM in the incoming line cabinet is a PMS963M model. Its current signal acquisition terminal is connected to the three-phase line through three-phase current transformers 1TAa, 1TAb, and 1TAc, respectively. The other ends of the current transformers 1TAa, 1TAb, and 1TAc are all grounded. The voltage signal acquisition terminals of the multi-functional monitoring meter PM in the incoming line cabinet are respectively connected in series with fuses FU1, FU2, and FU3 to acquire the voltages of the three-phase power supply L1, L2, and L3. Fuse FU1 is connected in series in the connection line between the L1 phase power supply and the corresponding voltage acquisition terminal of PM. Fuse FU2 is connected in series in the connection line between the L2 phase power supply and the corresponding voltage acquisition terminal of PM. Fuse FU3 is connected in series in the connection line between the L3 phase power supply and the corresponding voltage acquisition terminal of PM. When the multi-functional monitoring meter PM in the incoming line cabinet communicates with external devices through the RS485 communication interface, a shielded cable is used.

[0011] Preferably, the multi-functional monitoring meter PM in the feeder cabinet is a PMS723M model. Its current signal acquisition terminal is connected to the three-phase line through three-phase current transformers TAa, Tab, and Tac respectively. The other end of the current transformers TAa, Tab, and Tac is grounded. The voltage signal acquisition terminal of the multi-functional monitoring meter PM in the feeder cabinet is connected in series with fuses FU1, FU2, and FU3 respectively to acquire the voltage of the three-phase power supply L1, L2, and L3. When the multi-functional monitoring meter PM in the feeder cabinet communicates with external devices through the RS485 communication interface, a shielded cable is used.

[0012] Preferably, the feeder cabinet is provided with a moving contact terminal 1TX and a stationary contact terminal 2TX. The moving contact terminal 1TX and the stationary contact terminal 2TX are provided with terminals for connecting to external lines, for transmitting signals and power with external equipment and lines.

[0013] This utility model has the following beneficial effects: 1. In this utility model, the circuit introduces power from the mains to the branch circuit, and achieves hierarchical control through the main bus, branch bus, and circuit breaker to ensure continuous power supply to important loads such as fire protection. Through energy storage, logical linkage of closing and opening switches, automatic tripping in case of fault, and grounding protection, it avoids misoperation and fault expansion. Through instrument transformer isolation measurement, PM parameter acquisition, and shielded wire anti-interference communication, it realizes real-time monitoring and remote management of power distribution status, providing accurate data support for system operation and maintenance. The overall circuit takes into account safety, reliability, and intelligence, and meets the core design requirements of low-voltage power distribution systems.

[0014] 2. In this utility model, the secondary control circuit of the incoming line cabinet achieves the complete functions of "power protection - action control - status feedback - fault alarm" through the coordinated design of each circuit. The power supply circuit provides safe power supply for the control logic, the energy storage and closing / opening circuits ensure the reliability and condition limitations of the circuit breaker operation, and the indicator circuit and fault feedback circuit realize status visualization and remote monitoring, ultimately ensuring the safe and efficient operation of the entire low-voltage distribution cabinet system. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the secondary wiring principle of a low-voltage distribution cabinet control circuit proposed in this utility model. Figure 2 This is a schematic diagram of the power circuit structure of a low-voltage distribution cabinet control circuit proposed in this utility model. Figure 3 This is a schematic diagram of the fire-fighting power branch structure of a low-voltage distribution cabinet control circuit proposed in this utility model; Figure 4 This is a schematic diagram of the secondary control circuit structure of a low-voltage distribution cabinet control circuit proposed in this utility model. Detailed Implementation

[0016] The technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0017] Reference Figure 1 , Figure 2 and Figure 3This utility model provides an embodiment of a low-voltage distribution cabinet control circuit, including an incoming line cabinet and a feeder cabinet. The incoming line cabinet has a first main busbar inside, one end of which is connected to a bottom-mounted cable via a circuit breaker QF inside the cabinet. This bottom-mounted cable is used to introduce mains power. The other end of the first main busbar is connected to a branch busbar. The feeder cabinet has a second main busbar inside, connected to the branch busbar. The second main busbar supplies power to multiple fire-fighting power branches and backup power branches. Each fire-fighting power branch and backup power branch is equipped with a circuit breaker QF. The multi-functional monitoring meter PM has a current signal acquisition terminal connected to the secondary winding of a current transformer. The primary winding of the current transformer is connected in series in the three-phase line of the fire-fighting power supply branch. The multi-functional monitoring meter PM is connected to the three-phase line of the corresponding branch through the current transformer to acquire current signals, and connected to the three-phase power supply line to acquire voltage signals. The multi-functional monitoring meter PM is equipped with an RS485 communication interface for data transmission. The three-phase lines of the fire-fighting power supply branch and the backup branch are all connected to a PE busbar for grounding protection. Specifically, the feeder cabinet distributes the power obtained from the incoming cabinet to various power branches. The incoming cabinet is mainly responsible for drawing power from the mains and initially distributing it to the feeder cabinet. The first main busbar inside the incoming cabinet is connected at one end to the incoming cable at the bottom of the cabinet via a circuit breaker (QF). This incoming cable is used to draw in mains power. The circuit breaker (QF) plays a crucial control and protection role. During normal operation, it can be manually or automatically closed as needed to ensure smooth mains power access to the first main busbar, supplying power to the entire low-voltage distribution cabinet system. When overload or short-circuit faults occur on the mains side, the circuit breaker (QF) can quickly and automatically trip, cutting off the power supply, preventing the fault from escalating, and protecting downstream electrical equipment from damage. The other end of the first main busbar connects to the branch busbars. As a key component in the incoming cabinet that collects mains power, the first main busbar can efficiently and stably transmit power to the branch busbars. The branch busbars act as a power distribution relay, rationally distributing the power obtained from the first main busbar to the second main busbars of each feeder cabinet. This achieves the initial distribution of mains power in different areas or functional units, ensuring the rationality of the power supply layout of the entire power distribution system. Inside the feeder cabinets, there are second main busbars connected to the branch busbars, which can supply power to multiple fire-fighting power branches and backup branches. The second main busbars act as the power distribution hub within the feeder cabinets. After receiving power from the branch busbars, they accurately deliver power to each fire-fighting power branch and backup branch according to their power requirements. This connection ensures that each branch receives a stable and reliable power supply, meeting the power requirements of different loads. Each fire-fighting power branch and backup branch is equipped with a circuit breaker (QF) and a multi-function monitoring meter (PM). The circuit breaker (QF) is mainly responsible for controlling the on / off state of the branch and protecting the branch equipment. When a branch circuit experiences overload or short circuit faults, the circuit breaker QF can promptly disconnect the circuit, preventing the fault's impact from spreading to other branches and the entire power distribution system. During normal operation, maintenance personnel can also manually control the branch circuit's power supply status by operating the circuit breaker QF. The multi-function monitoring meter PM can monitor the branch circuit's electrical parameters in real time. By connecting to a current transformer and three-phase power lines, it can accurately collect current and voltage signals, thereby calculating parameters such as power and energy, facilitating real-time monitoring of branch circuit power consumption and timely detection of potential faults. The current transformer proportionally transforms the AC current, converting the large current in the three-phase lines of the fire protection power branch into a smaller current, which is then transmitted to the current signal acquisition terminal of the multi-function monitoring meter PM. This not only allows the multi-function monitoring meter PM to safely and accurately measure large currents but also enhances the electrical isolation between the secondary and primary circuits through the isolation effect of the current transformer, improving the system's safety and reliability.The multi-functional monitoring meter (PM) connects to the three-phase power line to accurately measure the three-phase voltage. Combined with the collected current signal, the PM can further calculate key electrical parameters, providing data support for power system operation management and energy optimization. Equipped with an RS485 communication interface, the PM can quickly and stably transmit various collected electrical parameters to external devices in digital signal form. This allows maintenance personnel to obtain real-time power consumption information for each branch from a remote monitoring center, facilitating centralized management, remote control, and fault diagnosis of the entire low-voltage distribution cabinet system, thus improving the system's intelligent management level and operational efficiency. All three-phase lines of the fire protection and backup branches are connected to a PE (protective earth) busbar. During normal operation, the PE busbar is at zero potential. When insulation damage occurs, causing the casing to become energized, the fault current can quickly flow to the ground through the PE busbar. This ensures that the potential of the leaking equipment casing is close to the ground potential, preventing electric shock. Simultaneously, the fault current can also trigger the circuit breaker (QF) in the line to trip, promptly disconnecting the faulty circuit and ensuring the safe operation of the entire power distribution system.

[0018] Reference Figure 1 and Figure 4 The incoming line cabinet is equipped with a secondary control circuit, which includes a power supply circuit, an energy storage control and indication circuit, a closing control circuit, a tripping control circuit, a tripping and closing indication circuit, and a fault feedback circuit. In the energy storage control and indication circuit, the indicator light HW is connected to the energy storage unit of the circuit breaker QF to indicate the energy storage status. In the tripping and closing control circuit, the closing button SF1 is connected to the closing unit of the circuit breaker QF to control closing, and the tripping button SF2 is connected to the tripping unit of the circuit breaker QF to control tripping. In the tripping and closing indication circuit, the tripping indicator light HG and the closing indicator light HR are connected through the auxiliary contacts of the circuit breaker QF to indicate the tripping and closing status of the circuit breaker QF. Specifically, in the energy storage control and indication circuit, the energy storage unit stores mechanical energy for the closing action of the circuit breaker QF. Once energy storage is complete, the energy storage contact CH automatically switches states, and the energy storage indicator light HW illuminates, visually indicating that energy storage is complete and prompting the operator that the circuit breaker is ready to close. If energy storage is incomplete, the energy storage contact CH opens, and the indicator light HW goes out, preventing misoperation. This linkage design between energy storage and indication ensures the reliability of the circuit breaker's closing action. In the closing control circuit, when the operator presses the closing button SF1, the closing coil XF is energized, generating electromagnetic force that drives the main contacts of the circuit breaker QF to close, thus energizing the main circuit. The closing coil XF only operates when energy storage is complete, the energy storage contact CH is closed, and the closing button SF1 is triggered, preventing closing failures due to lack of energy storage and ensuring the effectiveness and safety of the closing action. In the tripping control circuit, when the main circuit needs to be disconnected, pressing SF2 energizes the tripping coil MX, driving the main contacts of the circuit breaker QF to open and quickly disconnect the power supply. The tripping control circuit is crucial for system safety. In case of overload, short circuit, or other faults in the main circuit, the tripping coil MX can be linked by a protection signal to automatically trip the circuit breaker. In emergencies, operators can also force tripping via SF2 to prevent the accident from escalating. In the closing control circuit, auxiliary contacts are linked to the main contacts of the circuit breaker. When the main contacts close, the closing auxiliary contact OF2 closes, and the closing indicator light HR illuminates, indicating that the circuit breaker QF is in the closed state. When the main contacts open, the opening auxiliary contact OF1 closes, and the opening indicator light HG illuminates, indicating that the circuit breaker QF is in the open state. This allows operators to quickly determine the operating status of the circuit breaker through indicator lights without directly observing the main contacts, facilitating daily inspections and troubleshooting. In the fault feedback loop, when the circuit breaker automatically trips due to a fault, the fault feedback contact SDE will activate synchronously, sending a fault signal to the remote monitoring system to achieve automatic fault alarm. This loop can convert the local fault status into a remotely identifiable signal, making it easier for maintenance personnel to detect and handle anomalies in a timely manner.

[0019] Reference Figure 1 and Figure 2 In the power supply circuit, the phase line L1 is connected to a fuse FU4, which is used to lead out the line to provide power to the secondary control circuit. The neutral line N in the power supply circuit serves as the circuit neutral line. Specifically, the phase line L1 is led out through fuse FU4 to provide power to the entire secondary control circuit. The neutral line N serves as the common neutral line for the circuit, forming a complete power supply loop. Fuse FU4 is the core protection component of the power supply loop. When the secondary control circuit experiences overload, short circuit, or other faults, fuse FU4 will quickly melt, cutting off the power supply and preventing the fault from spreading to the main circuit or damaging secondary components, thus ensuring the safe and stable operation of the control circuit. The neutral line N provides a unified potential reference point for all loops, ensuring voltage stability in each loop and preventing control logic malfunctions caused by potential deviations.

[0020] Reference Figure 1 and Figure 4 The energy storage control and indication circuit includes an energy storage indicator light HW. One end of the energy storage indicator light HW is connected to the fuse FU4, and the other end is connected to the B3 terminal of the circuit breaker QF. The energy storage motor MCH inside the circuit breaker QF is connected in series with the energy storage contact CH. One end is connected to the B2 terminal of the circuit breaker QF, and the other end is connected to the B1 terminal. The closing control circuit includes a closing button SF1. One end of the closing button SF1 is connected to the fuse FU4, and the other end is connected to the A2 terminal of the circuit breaker QF. One end of the closing coil XF inside the circuit breaker QF is connected to the A2 terminal, and the other end is connected to the A1 terminal. Specifically, fuse FU is connected in series at the power supply front end of the energy storage indicator HW and the energy storage motor MCH. When an overload or short circuit occurs in the circuit, FU4 blows to cut off the power supply, preventing damage to the indicator HW and the energy storage motor MCH, and ensuring the safety of the energy storage circuit. The energy storage motor MCH can store mechanical energy for the circuit breaker QF to close. When the circuit breaker opens, the energy storage contact CH is in the closed state by default. At this time, the energy storage motor MCH is energized and starts to store energy. When energy storage is complete, the energy storage contact CH automatically opens, cutting off the motor power supply and preventing the motor from burning out due to overload. Through the linkage design between energy storage and contacts, the energy storage process is automatically stopped, ensuring that the energy storage is sufficient but not excessive. B1 is a common neutral terminal, uniformly connected to the circuit neutral wire. B2 is the power input terminal of the energy storage motor, and B3 is the connection terminal between the energy storage contact and the indicator light. Through standardized terminal design, the wiring inside the cabinet is clear, facilitating installation and maintenance. SF1 is a normally open button, which is open in the normal state and closes when pressed, making the circuit conductive. Its function is to manually trigger the closing command. Only when the operator actively presses SF1 or a remote control signal simulates SF1 closing can the closing coil XF be energized, preventing accidental closing. A2 is the power input terminal of the closing coil XF, and A1 is the output terminal of the coil, connected to the neutral wire N. When the closing button SF1 is closed and energy storage is complete, the energy storage contact CH closes, providing the mechanical conditions for closing. The closing coil XF is energized, generating electromagnetic force, which drives the main contacts of the circuit breaker to close, realizing the energization of the main circuit. This ensures reliable closing operation.

[0021] Reference Figure 1 and Figure 4 The tripping control circuit includes a tripping button SF2. One end of the tripping button SF2 is connected to fuse FU4, and the other end is connected to terminal C2 of circuit breaker QF. One end of the tripping coil MX inside circuit breaker QF is connected to terminal C2, and the other end is connected to terminal C1. The tripping / closing indication circuit includes a tripping indicator light HG and a closing indicator light HR. One end of the tripping indicator light HG is connected to fuse FU4, and the other end is connected to terminal 12 of circuit breaker QF. One end of the closing indicator light HR is connected to fuse FU4, and the other end is connected to terminal 14 of circuit breaker QF. The internal tripping auxiliary contact OF1 is connected to terminals 12 and 14 at one end and terminal 11 at the other end. Terminals B1, A1, C1, and 11 of circuit breaker QF are all connected to the neutral line N. The internal closing auxiliary contact OF2 of circuit breaker QF is connected to terminals 22 and 24 at one end and terminal 21 at the other end. The fault feedback contact SDE in the fault feedback circuit is connected to terminals 82 and 84 at one end and terminal 81 at the other end. Terminals 22, 24, and 127 of circuit breaker QF, as well as terminals 82, 84, and 127, are respectively connected to different line numbers of the secondary control circuit. Specifically, in the tripping control circuit, pressing SF2 energizes the coil, driving the circuit breaker to trip, while the fuse FU protects the circuit from overload and short circuit effects. In the tripping and closing indication circuit, the tripping indicator HG and the closing indicator HR are linked to the neutral line N via internal tripping auxiliary contact OF1 and closing auxiliary contact OF2, respectively. When the circuit breaker trips, OF1 closes, illuminating the tripping indicator HG; when it closes, OF2 closes, illuminating the closing indicator HR, providing direct feedback on the operating status. Terminals B1, A1, C1, and I1 are all connected to the neutral line N to ensure uniform potential across all circuits and prevent signal interference. Terminal 22 of circuit breaker QF is connected to auxiliary contact OF2 via line 123, and terminal 24 is connected to auxiliary contact OF2 via line 125, and then connected to the outside via line 121. Terminal 82 of circuit breaker QF is connected to fault feedback contact SDE via line 129, and terminal 84 is connected to fault feedback contact SDE via line 131, and then connected to the outside via line 127, realizing auxiliary control and fault feedback functions. Hardwiring clearly distinguishes the transmission paths of opening / closing status signals and fault signals, ensuring clear control logic and reliable signal transmission. Ultimately, this achieves safe triggering of circuit breaker opening operations, visualized monitoring of operating status, and accurate uploading of fault information, comprehensively improving the controllability and safety of the low-voltage power distribution system.

[0022] Reference Figure 1 and Figure 2The multi-functional monitoring meter PM in the incoming line cabinet is a PMS963M model. Its current signal acquisition terminal is connected to the three-phase line through three-phase current transformers 1TAa, 1TAb, and 1TAc, respectively. The other end of the current transformers 1TAa, 1TAb, and 1TAc is grounded. The voltage signal acquisition terminal of the multi-functional monitoring meter PM in the incoming line cabinet is connected to the three-phase power supply L1, L2, and L3 through lines connected in series with fuses FU1, FU2, and FU3, respectively. Fuse FU1 is connected in series in the connection line between the L1 phase power supply and the corresponding voltage acquisition terminal of PM. Fuse FU2 is connected in series in the connection line between the L2 phase power supply and the corresponding voltage acquisition terminal of PM. Fuse FU3 is connected in series in the connection line between the L3 phase power supply and the corresponding voltage acquisition terminal of PM. In the connection lines of the voltage acquisition terminals, the multi-function monitoring meter PM in the incoming line cabinet uses shielded wires when communicating with external equipment via the RS485 communication interface; the multi-function monitoring meter PM in the feeder cabinet is a PMS723M model, and its current signal acquisition terminal is connected to the three-phase lines through three-phase current transformers TAa, Tab, and Tac respectively. The other ends of the current transformers TAa, Tab, and Tac are all grounded. The acquisition terminals of the voltage signal acquisition terminal of the multi-function monitoring meter PM in the feeder cabinet are respectively connected in series with fuses FU1, FU2, and FU3 to acquire the voltages of the three-phase power supply L1, L2, and L3. The multi-function monitoring meter PM in the feeder cabinet uses shielded wires when communicating with external equipment via the RS485 communication interface. Specifically, the incoming line cabinet uses a PMS963M multi-function monitoring meter (PM). Three-phase line current is collected via 1TAa, 1TAb, and 1TAc three-phase current transformers. The other end of the transformers is grounded for protection. This utilizes the transformer's current-converting function to convert high current into a small current that the PM can safely measure. Grounding also prevents high voltage from entering the secondary circuit in case of insulation faults, ensuring equipment and personnel safety. Furthermore, the voltage acquisition terminals are connected in series with phases L1, L2, and L3 via FU1, FU2, and FU3 respectively. Fuses quickly blow in case of overload or short circuit in the voltage acquisition line, preventing damage to the PM's voltage acquisition section. The feeder cabinet uses a PMS723M multi-function monitoring meter (PM). Current acquisition is achieved through TAa, Tab, and Tac transformers. Similar to the incoming line cabinet, voltage acquisition is also connected to the three-phase power supply via corresponding fuses, ensuring the safety and accuracy of electrical parameter measurements in branch circuits. Both types of PMs connect to external devices via RS485 communication interfaces and use shielded cables for transmission. The shielding layer effectively isolates electromagnetic interference generated by circuit breakers, contactors, and other equipment within the distribution cabinet, while also preventing communication signals from radiating outwards and interfering with other circuits. This ensures that monitoring data such as current, voltage, and power are stably uploaded to the monitoring system. The overall design achieves accurate monitoring, fault early warning, and remote control of electrical parameters for the incoming main line and feeder branches, providing reliable data support for the safe operation and intelligent management of low-voltage power distribution systems.

[0023] Reference Figure 2 The feeder cabinet is equipped with a moving contact terminal 1TX and a stationary contact terminal 2TX. The moving contact terminal 1TX and the stationary contact terminal 2TX are equipped with terminals for connecting external lines, which are used to transmit signals and power with external equipment and lines. Specifically, the main function of the feeder cabinet is to distribute the electrical energy obtained from the incoming cabinet to various power branches. It needs to frequently make electrical connections with external loads and electrical equipment, and requires convenient disconnection and connection of circuits during system maintenance, equipment replacement, or line adjustments. The use of moving contact terminal 1TX and stationary contact terminal 2TX allows the feeder cabinet to connect to external lines more flexibly, facilitating power supply control and maintenance operations for each branch. By centrally locating the moving contact terminal 1TX and stationary contact terminal 2TX within the feeder cabinet, its functions are made more complete and independent, facilitating installation, commissioning, and maintenance. Simultaneously, it allows for a relatively simple structure of the incoming cabinet, focusing on power input and basic power distribution functions.

[0024] Working Principle: In operation, mains power is first supplied through the bottom cable at the bottom of the incoming cabinet, and the circuit breaker QF inside the cabinet controls the switching on and off. The circuit breaker QF acts as the main switch for the main circuit; during normal operation, it closes and conducts, introducing mains power into the first main busbar of the incoming cabinet. When an overload or short circuit occurs on the mains side, QF automatically trips to cut off the power supply, preventing the fault from spreading to downstream circuits. After collecting mains power through the first main busbar, the power is transmitted to the second main busbar of each feeder cabinet via branch busbars. The branch busbars act as a transfer and distribution hub, allocating the total power from the incoming cabinet to different feeder cabinets according to load requirements, achieving initial power division from the main circuit to the branches. The power is then distributed to the second main busbar of each feeder cabinet via the branch busbars, and from there to downstream loads such as fire protection power branches and backup power branches, forming a hierarchical power transmission link from mains power to the incoming cabinet, to the feeder cabinet, and finally to the electrical load. Each branch circuit is equipped with an independent circuit breaker (QF), which controls the on / off state of the branch and can trip independently in case of overload or short circuit, preventing a single branch fault from affecting other circuits and ensuring reliable power supply for critical loads such as fire protection. Simultaneously, all three-phase lines of all branches are connected to the protective earth (PE) busbar. When equipment insulation fails and the casing becomes energized, the fault current quickly flows to ground through the PE busbar, reducing the risk of electric shock and triggering the protective device to cut off the power supply. In the secondary control circuit, the power supply is drawn from the phase line L1 of the incoming cabinet via fuse FU, with the neutral line N serving as a common circuit to provide stable voltage for energy storage, closing / opening, and indicating circuits. The power supply circuit of the incoming line cabinet leads to the control power supply through fuse FU. The energy storage control and indication circuit uses the energy storage motor MCH to store the mechanical energy for closing. The energy storage status is fed back through the linkage between the energy storage contact CH and the indicator light HW. The opening and closing control circuit realizes the manual and automatic opening and closing of the circuit breaker through the buttons SF1 and SF2 and the corresponding coils XF and MX. It also displays the opening and closing status in real time through the linkage between the auxiliary contacts OF1 and OF2 and the indicator lights HG and HR. The fault feedback circuit transmits the circuit breaker fault signal to the external system through a specific line through the fault contact SDE to realize abnormal early warning. The PMS963M type multi-function monitoring meter PM used in the incoming line cabinet and the PMS723M type multi-function monitoring meter PM used in the feeder cabinet collect three-phase current through the current transformer TA and three-phase voltage through fuses FU1, FU2, and FU3, respectively. Both types of multi-function monitoring meters PM communicate with external monitoring equipment through RS485 communication interface and use shielded wire for transmission. The metal shielding layer of the shielded wire can block electromagnetic interference generated by circuit breakers, contactors and other equipment in the distribution cabinet, while preventing communication signals from radiating outwards and interfering with other circuits. It ensures that data such as voltage, current and fault status are uploaded stably, thereby realizing remote monitoring, data analysis and intelligent management of the power distribution system. At the same time, each branch is grounded through the PE busbar to form protection. The working principle of the low-voltage distribution cabinet control circuit is to achieve closed-loop operation of mains power introduction, power distribution, safety protection and status monitoring through hierarchical power transmission paths and intelligent monitoring and control logic. The overall circuit, through the coordinated design of main circuit power transmission, secondary circuit control and protection and monitoring system data feedback, ensures that the mains power is stably distributed to each load, can quickly cut off faults through protective components, and realizes real-time parameter monitoring and remote management through monitoring equipment, ultimately ensuring the safe, reliable and intelligent operation of the low-voltage power distribution system.

[0025] Finally, it should be noted that the above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Although the present utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A low-voltage distribution cabinet control circuit, comprising an incoming line cabinet and a feeder cabinet, characterized in that: The incoming line cabinet is equipped with a first main busbar. One end of the first main busbar is connected to the bottom incoming cable of the cabinet via a circuit breaker QF inside the cabinet. The bottom incoming cable is used to introduce mains power. The other end of the first main busbar is connected to a branch busbar. The feeder cabinet is equipped with a second main busbar connected to the branch busbar. The second main busbar supplies power to multiple fire-fighting power branches and backup branches. Each fire-fighting power branch and backup branch is equipped with a circuit breaker QF and a multi-function monitoring meter PM. The current signal acquisition terminal of the multi-function monitoring meter PM is connected to the secondary winding of a current transformer. The primary winding of the current transformer is connected in series in the three-phase line of the fire-fighting power branch. The multi-function monitoring meter PM is connected to the three-phase line of the corresponding branch through the current transformer to acquire current signals and to the three-phase power supply line to acquire voltage signals. The multi-function monitoring meter PM is equipped with an RS485 communication interface for data transmission. The three-phase lines of the fire-fighting power branch and backup branch are all connected to a PE busbar for grounding protection.

2. The low-voltage distribution cabinet control circuit according to claim 1, characterized in that: The incoming line cabinet is equipped with a secondary control circuit, which includes a power supply circuit, an energy storage control and indication circuit, a closing control circuit, a tripping control circuit, a tripping and closing indication circuit, and a fault feedback circuit. In the energy storage control and indication circuit, the indicator light HW is connected to the energy storage unit of the circuit breaker QF to indicate the energy storage status. In the tripping and closing control circuit, the closing button SF1 is connected to the closing unit of the circuit breaker QF to control closing, and the tripping button SF2 is connected to the tripping unit of the circuit breaker QF to control tripping. In the tripping and closing indication circuit, the tripping indicator light HG and the closing indicator light HR are connected through the auxiliary contacts of the circuit breaker QF to indicate the tripping and closing status of the circuit breaker QF.

3. The low-voltage distribution cabinet control circuit according to claim 2, characterized in that: In the power supply circuit, the phase line L1 is connected to a fuse FU4, which is used to lead out a line to provide power to the secondary control circuit. The neutral line N in the power supply circuit serves as the circuit neutral line.

4. The low-voltage distribution cabinet control circuit according to claim 2, characterized in that: The energy storage control and indication circuit includes an energy storage indicator light HW. One end of the energy storage indicator light HW is connected to the fuse FU4, and the other end is connected to the B3 terminal of the circuit breaker QF. The energy storage motor MCH inside the circuit breaker QF is connected in series with the energy storage contact CH. One end of the contact is connected to the B2 terminal of the circuit breaker QF, and the other end is connected to the B1 terminal. The closing control circuit includes a closing button SF1. One end of the closing button SF1 is connected to the fuse FU4, and the other end is connected to the A2 terminal of the circuit breaker QF. One end of the closing coil XF inside the circuit breaker QF is connected to the A2 terminal, and the other end is connected to the A1 terminal.

5. A low-voltage distribution cabinet control circuit according to claim 2, characterized in that: The tripping control circuit includes a tripping button SF2, one end of which is connected to fuse FU4, and the other end is connected to terminal C2 of circuit breaker QF. One end of the tripping coil MX inside circuit breaker QF is connected to terminal C2, and the other end is connected to terminal C1. The tripping / closing indication circuit includes a tripping indicator light HG and a closing indicator light HR. One end of the tripping indicator light HG is connected to fuse FU4, and the other end is connected to terminal 12 of circuit breaker QF. One end of the closing indicator light HR is connected to fuse FU4, and the other end is connected to terminal 14 of circuit breaker QF. The tripping... The tripping auxiliary contact OF1 inside the circuit breaker QF is connected to terminals 12 and 14 at one end and terminal 11 at the other end. Terminals B1, A1, C1, and 11 of the circuit breaker QF are all connected to the neutral line N. The closing auxiliary contact OF2 inside the circuit breaker QF is connected to terminals 22 and 24 at one end and terminal 21 at the other end. The fault feedback contact SDE in the fault feedback circuit is connected to terminals 82 and 84 at one end and terminal 81 at the other end. Terminals 22, 24, and 127 of the circuit breaker QF, as well as terminals 82, 84, and 127, are respectively connected to different line numbers of the secondary control circuit.

6. The low-voltage distribution cabinet control circuit according to claim 1, characterized in that: The multi-functional monitoring meter PM in the incoming line cabinet is a PMS963M model. Its current signal acquisition terminal is connected to the three-phase line through three-phase current transformers 1TAa, 1TAb, and 1TAc, respectively. The other end of each current transformer 1TAa, 1TAb, and 1TAc is grounded. The voltage signal acquisition terminal of the multi-functional monitoring meter PM in the incoming line cabinet is connected in series with fuses FU1, FU2, and FU3 to acquire the voltages of the three-phase power supply L1, L2, and L3, respectively. Fuse FU1 is connected in series in the connection line between the L1 phase power supply and the corresponding voltage acquisition terminal of PM. Fuse FU2 is connected in series in the connection line between the L2 phase power supply and the corresponding voltage acquisition terminal of PM. Fuse FU3 is connected in series in the connection line between the L3 phase power supply and the corresponding voltage acquisition terminal of PM. The multi-functional monitoring meter PM in the incoming line cabinet uses a shielded cable when communicating with external devices through the RS485 communication interface.

7. A low-voltage distribution cabinet control circuit according to claim 1, characterized in that: The multi-functional monitoring meter PM in the feeder cabinet is a PMS723M model. Its current signal acquisition terminal is connected to the three-phase line through three-phase current transformers TAa, Tab, and Tac respectively. The other end of the current transformers TAa, Tab, and Tac is grounded. The voltage signal acquisition terminal of the multi-functional monitoring meter PM in the feeder cabinet is connected in series with fuses FU1, FU2, and FU3 respectively to acquire the voltage of the three-phase power supply L1, L2, and L3. The multi-functional monitoring meter PM in the feeder cabinet uses a shielded cable when communicating with external devices through the RS485 communication interface.

8. A low-voltage distribution cabinet control circuit according to claim 1, characterized in that: The feeder cabinet is equipped with a moving contact terminal 1TX and a stationary contact terminal 2TX. The moving contact terminal 1TX and the stationary contact terminal 2TX are provided with terminals for connecting to external lines, for transmitting signals and power with external equipment and lines.

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