Medium and low voltage integrated power distribution spare power automatic switching intelligent measurement and control system

Abstract

The invention provides a medium and low voltage integrated power distribution spare power automatic switching intelligent measurement and control system, which relates to the technical field of spare power automatic switching, and comprises a 6KV system comprehensive protection module, a 6KV system control module, a measurement and control acquisition module, an operation and maintenance management module, a communication switching module and a 400V switching control module, the communication switching module is electrically connected with the 6KV system comprehensive protection module, the 6KV system control module, the measurement and control acquisition module, the operation and maintenance management module and the 400V switching control module. The 6KV system comprehensive protection module collects incoming and outgoing line voltages and incoming and outgoing line currents of a 6KV bus, and sends a tripping command to the communication switching module when a fault occurs so as to correspondingly adjust the 6KV system control module and the measurement and control acquisition module. The 6KV system control module drives a 6KV circuit breaker and a bus tie switch in the 6KV system comprehensive protection module; and the 400V switching control module distributes 400V of a main transformer low-voltage bus to the 6KV system control module, the measurement and control acquisition module and the communication switching module. According to the invention, the anti-interference capability and the self-recovery capability can be enhanced.

Description

Technical Field

[0001] This invention relates to the field of automatic transfer switch technology, and in particular to an integrated intelligent monitoring and control system for automatic transfer switch of medium and low voltage power distribution. Background Technology

[0002] Automatic transfer switch (ATS), also known as standby power supply automatic transfer device, is widely used in power supply systems. Before restoring operation after power system maintenance, an ATS test is generally required to verify the logic of the ATS device and ensure power supply reliability. ATS generally operates in three modes: fully automatic, semi-automatic, and deactivated. Fully automatic mode: When a fault in the incoming line circuit causes a loss of voltage on the busbar, the incoming line switch trips after a delay, and then a closing command is issued to close the bus tie switch; when the incoming line voltage returns to normal, the return procedure is automatically initiated, disconnecting the bus tie switch and closing the incoming line switch. Semi-automatic mode: When the incoming line loses voltage, the incoming line switch trips after a delay, and only a closing command is issued to close the bus tie switch. Deactivated mode: ATS is deactivated. Currently, the common approach to conducting ATS tests is to switch the ATS to a specific mode on the monitoring system or the ATS device, and then, in this mode, simulate a busbar loss caused by an incoming line fault by opening and closing the upstream incoming power switch, observing the standby power supply activation status to verify the system's operation. For example, when conducting a test of the automatic transfer switch in "semi-automatic" mode, the automatic transfer switch mode needs to be switched to "semi-automatic" first, and then the upstream incoming power switch needs to be disconnected. At this time, the bus will lose voltage. When the automatic transfer switch determines that the backup power supply is ready to be put into operation, it will automatically disconnect the incoming switch and close the bus tie switch, thereby restoring power supply to the lost-voltage bus.

[0003] Chinese Patent CN110932395B discloses a communication system for low-voltage intelligent automatic transfer switching (ATS). The system includes a main station platform for receiving and processing data collected by the ATS. The ATS includes a low-voltage intelligent ATS device for connecting two distribution room busbars and collecting data from the busbar lines. This device wirelessly controls switches on each line to achieve automatic switching. The device is also wirelessly connected to an intelligent low-voltage monitoring terminal via Ethernet, which in turn is wirelessly connected to the main station platform. However, this solution uses only ordinary wireless / Ethernet, and the terminal only collects and reports data, lacking local PLC or distributed decision-making capabilities. This results in insufficient anti-interference and self-recovery capabilities. Therefore, providing a medium- and low-voltage integrated intelligent ATS monitoring and control system is essential to enhance anti-interference and self-recovery capabilities. Summary of the Invention

[0004] In view of this, the present invention proposes an integrated intelligent monitoring and control system for medium and low voltage power distribution with automatic transfer switch. By setting up a 6kV system protection module, the voltage and current of the busbar incoming and outgoing lines can be collected in real time. The monitoring and control acquisition module and the 6kV control module work together to ensure that each module can maintain key control and communication functions even when the main power supply is abnormal, thereby enhancing anti-interference capability and self-recovery capability.

[0005] This invention provides an integrated intelligent monitoring and control system for medium and low voltage power distribution automatic transfer switches, comprising a 6kV system comprehensive protection module, a 6kV system control module, a monitoring and control acquisition module, a communication switching module, an operation and maintenance management module, and a 400V transfer control module. The communication switching module is electrically connected to the 6KV system integrated protection module, the 6KV system control module, the measurement and control acquisition module, the operation and maintenance management module, and the 400V transfer control module, respectively. The 6kV system integrated protection module is used to collect the incoming and outgoing line voltages and currents of the 6kV bus, and in the event of a fault, it sends a trip command to the communication exchange module to adjust the 6kV system control module and the measurement and control acquisition module accordingly. The 6kV system control module is used to receive the opening / opening commands from the measurement and control acquisition module to drive the 6kV circuit breaker and bus tie switch in the 6kV system integrated protection module; The measurement and control acquisition module is used to collect the voltage, current, switch position and low-voltage bus status of the 6KV system protection module and the 400V transfer control module, and send corresponding control commands to the 6KV system protection module, the 6KV system control module, the operation and maintenance management module and the 400V transfer control module; The 400V transfer control module is used to distribute the 400V of the main transformer low-voltage bus to the 6KV system control module, the measurement and control acquisition module, and the communication exchange module.

[0006] Based on the above technical solutions, preferably, the tripping or closing commands of the 6KV system integrated protection module and the 6KV system control module are transmitted using IEC 61850 GOOSE high-speed messages, and the message period is less than 4 ms. The protection action records and fault waveforms are reported to the measurement and control acquisition module through IEC 61850 MMS or Modbus TCP.

[0007] Based on the above technical solutions, preferably, the backup automatic switching logic in the measurement and control acquisition module includes: When the incoming bus in the 6KV system integrated protection module or the 400V transfer control module loses voltage and continues for a preset delay, the measurement and control unit first sends a closing bus tie command, and then automatically returns after the main power supply is restored. Alternatively, if the incoming line of the 6KV system integrated protection module or the 400V transfer control module loses voltage, only a closing bus tie command is issued and no return trip is performed. Alternatively, it can disable any automatic tripping or closing operations and issue an alarm when the integrated low-voltage power distribution backup automatic transfer intelligent monitoring and control system malfunctions.

[0008] More preferably, the measurement and control acquisition module exchanges monitoring data and configuration parameters with the operation and maintenance management module via Modbus / TCP or OPC UA.

[0009] More preferably, the operation and maintenance management module includes a data acquisition unit, a historical storage and analysis unit, a fault diagnosis unit, and a human-computer interaction unit, wherein, The data acquisition unit polls the measurement and control acquisition module and the 6KV system control module for real-time data via an OPC UA client or Modbus TCP; the historical storage and analysis unit uses a time-series database to store current, voltage, switching counts, and alarm events, and automatically generates an operation evaluation report based on preset thresholds; the fault diagnosis unit imports fault waveform files reported by the 6KV system integrated protection module for offline fault playback and location operations; and the human-machine interaction unit supports remote parameter distribution and access control.

[0010] More preferably, the 400V transfer control module includes isolating switches 1G, 2G, 3G, 4G, 5G, and 6G; collateralized air circuit breaker Q1, Q2, and Q3; AC contactor KM8 and KM9; a dual power supply circuit; a backup automatic transfer circuit; and a load device. The first incoming line is connected to the dual power supply circuit, one end of the AC contactor KM8, and one end of the isolating switch 1G. The other end of the isolating switch 1G is connected to the backup automatic transfer circuit, the load device, and one end of the isolating switch 5G via the collateralized air circuit breaker Q1 and the isolating switch 2G. The second incoming line is connected to the dual power supply circuit, one end of the AC contactor KM9, and one end of the isolating switch 3G. The other end of the isolating switch 3G is connected to the backup automatic transfer circuit, the load device, and one end of the isolating switch 6G via the collateralized air circuit breaker Q2 and the isolating switch 4G. The collateralized air circuit breaker Q3 is connected to the other ends of the isolating switches 5G and 6G.

[0011] More preferably, the 400V transfer control module includes isolating switches 1G, 2G, 3G, 4G, 5G, and 6G; collateralized air circuit breaker Q1, Q2, and Q3; AC contactor KM8 and KM9; a dual power supply circuit; a backup automatic transfer circuit; and a load device. The first incoming line is connected to the dual power supply circuit, one end of the AC contactor KM8, and one end of the isolating switch 1G. The other end of the isolating switch 1G is connected to the backup automatic transfer circuit, the load device, and one end of the isolating switch 5G via the collateralized air circuit breaker Q1 and the isolating switch 2G. The second incoming line is connected to the dual power supply circuit, one end of the AC contactor KM9, and one end of the isolating switch 3G. The other end of the isolating switch 3G is connected to the backup automatic transfer circuit, the load device, and one end of the isolating switch 6G via the collateralized air circuit breaker Q2 and the isolating switch 4G. The collateralized air circuit breaker Q3 is connected to the other ends of the isolating switches 5G and 6G.

[0012] More preferably, the 400V transfer control module further includes a zero-sequence self-holding circuit, which includes terminal block XT5, AC contactor KM10, zero-sequence overcurrent relay GL1, AC contactor KM11, normally closed pushbutton SB1, AC contactor KM12, zero-sequence overcurrent relay GL2, AC contactor KM13, and normally closed pushbutton SB2. The coil of AC contactor KM10 is connected to one end of zero-sequence overcurrent relay GL1 and terminal block XT5, respectively. The other end of zero-sequence overcurrent relay GL1 is connected to terminal block XT5. The first common terminal of the normally open contact of AC contactor KM10 and the normally open contact of AC contactor KM11 is connected to the coil of AC contactor KM10. The second common terminal of the normally open contact of AC contactor KM10 and the normally open contact of AC contactor KM11 is connected to the coil of AC contactor KM11. The coil of AC contactor KM11 is connected to terminal block XT5 through normally closed button SB1. The coil of AC contactor KM12 is connected to one end of zero-sequence overcurrent relay GL2 and terminal block XT5, respectively. The other end of zero-sequence overcurrent relay GL1 is connected to terminal block XT5. The first common terminal of the normally open contact in AC contactor KM12 and the normally open contact in AC contactor KM13 is connected to the coil of AC contactor KM12. The second common terminal of the normally open contact in AC contactor KM12 and the normally open contact in AC contactor KM13 is connected to the coil of AC contactor KM13. The coil of AC contactor KM13 is connected to terminal block XT5 through normally closed button SB2.

[0013] More preferably, the 400V transfer control module further includes a PLC power supply circuit, which includes circuit breaker QF3, circuit breaker QF4, a power module, a switching power supply, and a CPU. The common terminal of circuit breaker QF3 and circuit breaker QF4 is connected to an external 220V AC power supply. The other end of circuit breaker QF3 is connected to a switching power supply. The switching power supply is connected to the dual power supply circuit, the backup automatic transfer circuit, and the load device. The power module is connected to the other end of circuit breaker QF4 and the CPU, respectively.

[0014] More preferably, the communication switching module supports one or more of VLAN, QoS, link aggregation, IEC 61850 GOOSE / MMS, Modbus TCP, and OPC UA.

[0015] The integrated low- and medium-voltage power distribution automatic transfer switch intelligent monitoring and control system provided by this invention has the following advantages over existing technologies: (1) By setting up a 6kV system integrated protection module, the voltage and current of the bus incoming and outgoing lines can be collected in real time. Once an abnormal fault is detected, a trip command can be sent to the communication exchange module in milliseconds. The linkage control module and the measurement and control acquisition module complete the fault isolation, significantly shortening the fault clearing time. The measurement and control acquisition module works in conjunction with the 6kV control module. It can automatically drive the circuit breaker and bus tie switch according to the operating status and opening / opening instructions, realize the automatic switching of medium and low voltage sides and standby automatic transfer, and ensure the continuity of power grid operation and power supply reliability. The communication exchange module electrically connects and uniformly schedules the five major functional units of integrated protection, control, acquisition, operation and maintenance and 400V transfer control, which simplifies the system architecture, improves the deployment flexibility and field scalability. At the same time, the 400V transfer control module directly takes from the transformer low voltage bus to provide an independent and stable auxiliary power supply for each measurement and control and communication unit, ensuring that each module can still maintain key control and communication functions when the main power supply is abnormal, so as to enhance the anti-interference capability and self-recovery capability.

[0016] (2) Seamless switching of the first and second incoming lines is achieved through two AC contactors, KM8 and KM9. Isolating switches 1G-4G work with circuit breakers Q1 and Q2 to ensure complete source isolation before each connection. Isolating switches 5G and 6G are linked with circuit breaker Q3 to cut off the cross feedback path of the two power supplies. The combination of multi-point isolating switches and circuit breakers effectively suppresses arc and surge current during the switching process. The dual power supply circuit and the backup automatic transfer circuit run in parallel. When the main circuit loses power, it can automatically switch to the backup circuit to ensure that the critical load is not interrupted. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This invention provides a schematic diagram of the framework of an integrated medium- and low-voltage power distribution automatic transfer intelligent monitoring and control system. Figure 2 A circuit diagram of the 6KV system integrated protection module provided by the present invention; Figure 3 A schematic diagram of a 400V bus tie automatic transfer circuit provided by the present invention; Figure 4 A circuit diagram of the PLC power supply circuit provided by the present invention; Figure 5 A circuit diagram of the dual power supply circuit provided by the present invention; Figure 6A circuit diagram of the zero-sequence overcurrent self-holding circuit provided by the present invention; Figure 7 This is a timing diagram of the first operation of the 400V adapter control module provided by the present invention; Figure 8 The second action timing diagram of the 400V adapter control module provided by the present invention.

[0019] Explanation of reference numerals in the attached diagram: 1. 6KV system integrated protection module; 2. 6KV system control module; 3. Measurement and control acquisition module; 4. Communication switching module; 5. Operation and maintenance management module; 6. 400V transfer control module. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] This invention discloses an integrated intelligent monitoring and control system for medium and low voltage power distribution automatic transfer switches, with reference to... Figure 1 The integrated low- and medium-voltage power distribution automatic transfer switch intelligent monitoring and control system includes a 6KV system comprehensive protection module 1, a 6KV system control module 2, a monitoring and control acquisition module 3, a communication exchange module 4, an operation and maintenance management module 5, and a 400V transfer control module 6. The communication switching module 4 is electrically connected to the 6KV system integrated protection module 1, the 6KV system control module 2, the measurement and control acquisition module 3, the operation and maintenance management module 5, and the 400V transfer control module 6, respectively. Among them, the 6KV system integrated protection module 1 can be a 6KV system integrated protection device, the 6KV system control module 2 can be a 6KV system control cabinet, the measurement and control acquisition module 3 can be an M580 measurement and control unit cabinet, the operation and maintenance management module 5 can be a digital intelligent platform, the communication switching module 4 can be a switch, and the 400V transfer control module 6 can be a 400V power distribution system.

[0022] The 6kV system integrated protection module 1 is used to collect the incoming and outgoing line voltages and currents of the 6kV busbar, and in the event of a fault, it sends a trip command to the communication exchange module 4 to adjust the 6kV system control module 2 and the measurement and control acquisition module 3 accordingly. The 6kV system control module 2 is used to receive the opening / opening commands from the measurement and control acquisition module 3 to drive the 6kV circuit breaker and bus tie switch in the 6kV system integrated protection module 1.

[0023] The 6KV control cabinet controls the original 6KV power distribution system; each 400V low-voltage cabinet controls its respective low-voltage system; automatic transfer switching for each system is completed in each local PLC controller. The 6KV system control module 2 adopts a dual-machine, dual-network hot standby configuration. The I / O module configuration consists of 6 DI 32-point digital input modules, 2 DO 32-point digital output modules, and 2 AI 16-point analog output modules.

[0024] If the voltage loss of bus tie sections I and IV in the 6kV system integrated protection module 1 causes the automatic transfer switch (ATS) of the 6kV system integrated protection module 1 to activate, the ATS signal needs to be sent to the 400V transfer control module 6 to block the ATS activation logic caused by the power loss at the upper end. The 400V transfer control module 6 itself has a 7-second delay to determine whether the voltage loss signal is distorted. If an electrical fault causes the voltage of the section to fail to recover even if the ATS of the 6kV system integrated protection module 1 activates, the electrical fault signal is sent to the 400V transfer control module 6. The 400V transfer control module 6 will then activate the ATS directly without a delay.

[0025] In one example, the 6kV control cabinet communicates with the newly added M580 monitoring and control unit cabinet to exchange signals; each 400V system control cabinet also communicates with the newly added M580 monitoring and control unit cabinet to exchange signals. The newly added M580 monitoring and control unit cabinet receives the action signals from the 6kV control cabinet and sends instructions to the corresponding 400V system controller to prevent frequent automatic transfer switching of the 400V plant power system caused by the automatic transfer switching of the 6kV medium-voltage backup power system. The automatic transfer switching function between the 6kV and each 400V power distribution system is implemented through hard-wiring of the PLC control system, and the integrated linkage signals of medium and low voltage are transmitted through communication.

[0026] The tripping or closing commands of the 6KV system integrated protection module 1 and the 6KV system control module 2 are transmitted using IEC 61850 GOOSE high-speed messages, and the message period is less than 4 ms. The protection action records and fault waveforms are reported to the measurement and control acquisition module 3 through IEC 61850 MMS or Modbus TCP.

[0027] Please see Figure 2 ,by Figure 2 Taking one large section as an example, the priority order of automatic transfer switching (ATS) for the 6KV large section is 6022, 6021, 611, 612, and 6403. The design logic for the ATS of the two large sections is the same, and the operating sequence of the power supply switches is 6052, 6051, 613, 614, and 6403.

[0028] As can be seen from the flowchart of the standby automatic transfer action above, the conditions for the standby automatic transfer action are: For a large segment of motherboards I, II, and III to lose pressure, the following three conditions are indispensable: DUMMY.DI_VALUE

[21] =1 (1) The analog voltage values ​​of the three bus sections I, II and III are all below the lower limit, and the bus line voltage is less than 15% of the rated value, that is, less than 1.0kV; (2) The switching quantities of the three bus sections I, II, and III all operate when the voltage is low; (3) Continue for 1 second.

[0029] The protection signals of the main line 6021, 6022, 6201, 6302 and bus tie switch did not activate. DUMMY.DI_VALUE

[25] =1, the protection signal of the main line 6403 tie switch did not activate. DI

[49] =0, the automatic transfer switch on the control panel of the plant power local control unit is activated. DI

[180] =1, the automatic transfer switch on the remote monitoring screen of the plant power is activated. DUMMY.DI_VALUE

[23] =1, the main line standby switch is not 0 and 6. DUMMY.DI_VALUE

[23] =1, the main line standby switch has not been deactivated. BZT1=1, the main line standby switch is not in test state. TESTBZT1=0 The main line main switch incoming voltage is abnormal, any of the following five conditions are met. (MS1=1 AND DI

[24] ) OR (MS1=2 AND DI

[18] ) OR (MS1=3 AND DI[3]) OR (MS1=4 AND DI[6]) OR (MS1=5 AND DI

[78] ). All of the following five conditions must be met: (1) Main switch 6022, the voltage of the 6022 input line is abnormal; (2) Main switch 6021, the voltage of the 6021 input line is abnormal; (3) Main switch 611, the voltage of the 611 incoming line is abnormal; (4) Main switch 612, the voltage of the 612 incoming line is abnormal; (5) Main switch 6403, the incoming voltage of 6403 is abnormal.

[0030] For a large section of incoming line switches that are not in an indeterminate state, the following five conditions must be met: NOT (DI

[19] =DI

[20] OR DI

[13] =DI

[14] OR DI[1]=DI[2]OR DI[4]=DI[5]OR DI

[47] =DI

[48] ): (1) Switch 6022 is not in an indeterminate state; (2) Switch 6021 is not in an indeterminate state; (3) Switch 611 is not in an indeterminate state; (4) Switch 612 is not in an indeterminate state; (5) Switch 6403 is not in an indeterminate state.

[0031] A large section of bus tie switches is closed, and the following two conditions must be met: (DI

[37] =1 AND DI

[38] =0) AND(DI

[42] =1 AND DI

[43] =0): (1) Switch 6203 is closed; (2) Switch 6302 is closed.

[0032] When a large segment of the automatic transfer switch (ATS) conditions are met, the ATS process is initiated after a 500-millisecond delay. First, the main switch with an abnormal incoming power supply is tripped, and then the available backup power switches are closed sequentially. Before closing a backup switch, it should be checked that there is voltage on the incoming side of that switch (the judgment condition is that the incoming voltage is normal). Otherwise, the next switch is closed. If the voltage does not recover after closing a switch or the switch fails to close, that switch is tripped, and then other backup power switches with normal incoming voltages are closed until a large segment of power supply is restored.

[0033] After the automatic transfer switch (ATS) process successfully completes steps 6021, 611, and 612, if power is lost again (after manually setting the unsuccessful switches to standby status before the operation), the cycle will still start from 6022 and execute switches that meet the standby conditions. However, when switch 6403 is finally closed, if a large section of power is restored successfully, the ATS process for that section will be deactivated; if a large section of power is still lost and power restoration fails, then switch 6403, and the ATS process for that section will also be deactivated.

[0034] The measurement and control acquisition module 3 is used to collect the voltage, current, switch position and low-voltage bus status of the 6KV system integrated protection module 1 and the 400V transfer control module 6, and send corresponding control commands to the 6KV system integrated protection module 1, the 6KV system control module 2, the operation and maintenance management module 5 and the 400V transfer control module 6.

[0035] The automatic transfer logic in the measurement and control acquisition module 3 includes: when the incoming bus of the 6KV system integrated protection module 1 or the 400V transfer control module 6 loses voltage and continues for a preset delay, the measurement and control unit first sends a bus tie closing command, and then automatically returns after the main power supply is restored; or when the incoming line of the 6KV system integrated protection module 1 or the 400V transfer control module 6 loses voltage, only a bus tie closing command is sent and no return is performed; or any automatic tripping and closing operations are prohibited, and an alarm is issued when the integrated low-voltage power distribution automatic transfer intelligent measurement and control system malfunctions.

[0036] The monitoring and control acquisition module 3 exchanges monitoring data and configuration parameters with the operation and maintenance management module 5 via Modbus / TCP or OPC UA. The communication exchange module 4 supports one or more of VLAN, QoS, link aggregation, IEC 61850 GOOSE / MMS, Modbus TCP, and OPC UA.

[0037] Furthermore, the compatibility of the 6kV system integrated protection module 1 was tested using the PO software logic functions. The test objects included the PO software, the 6kV control system, and its local PLC. Section I and Section II are two 6kV sections, with automatic transfer switch included in the entire process of automatic transfer and automatic reset. Conventional undervoltage confirmation and opening / closing delays were executed according to the field settings.

[0038] The test objectives and scope are to verify whether the automatic transfer switch logic of the 6kV I and II segments carried solely by the PO software is correct, to verify whether the 6kV local PLC can independently take over and complete the automatic transfer switch when the PO software does not operate or the operation process is incomplete, and to verify the feasibility and repeatability of the two test environments, including full simulation and semi-physical methods.

[0039] General prerequisites and success criteria: 6kV relevant circuit breakers and bus couplers are in working or test positions, remotely effective, and not in a deactivated or disconnected state; there are no manual tripping interlocks, no circuit breaker fault tripping interlocks, and no insufficient closing preparation conditions; the PO software, switch, and network topology are clear, with means for on-demand shielding, network disconnection, and process control; SOE and logs are enabled, capable of recording triggering, command issuance, arrival, and delay. Fifth, success criteria include correct action sequence, delay meeting set values, interlocking satisfied, SOE consistent with indications, and no false tripping in abnormal scenarios.

[0040] To disable the automatic transfer switch (ATS) function of the local PLC, only enable the 6kV I and II main sections' ATS functions in the PO software to verify the logic correctness. First, disable or disable the ATS functions of the I and II main sections' ATS functions in the local PLC of the 6kV control system. Second, enable the ATS functions of the I and II main sections' ATS functions in the PO software and verify the settings and delays. Third, prepare voltage, current, or protection test sources to simulate main section undervoltage or upstream tripping conditions.

[0041] The testing steps include simulating the undervoltage or equivalent triggering conditions of section I, observing the opening, closing, and self-recovery commands issued by the PO software, and verifying the sequence and delay; simulating similar operating conditions of section II for symmetrical verification. Thirdly, if necessary, branches such as restart, self-recovery failure, and failure exit are added to verify anomaly handling and interlocking.

[0042] The key criteria for judgment include that the PO software should independently complete the complete closed loop of automatic backup switching, and that the interlocks are correct, without any overstepping or erroneous connection, and that the SOE time meets the set value.

[0043] When the PO software fails to operate or its operation process is incomplete, the following scenarios are used to verify whether the 6kV local PLC can reliably take over and complete the automatic backup switching: Scenario 1: The PO software does not operate, and the local PLC takes over. Verification methods include disabling the automatic transfer switch function in the PO software, simulating a PO software process crash, or disconnecting the two network cables from the 6kV control system to switches A and B of the M580 main control cabinet to create a communication interruption with the PO. The actions involve generating undervoltage signals or upper-level tripping conditions in sections I and II respectively. The expected outcome is that the PO software will not issue an automatic transfer switch command, and the local PLC will independently complete the entire automatic transfer switch process after meeting the conditions and a delay. The self-reset strategy and settings will conform to the field settings, and the SOE record will be complete.

[0044] Scenario 2: The PO software's action flow is incomplete, and the local PLC takes over. Verification methods include starting only the first half of the automatic transfer switch process in the PO software or stopping it midway, making the process incomplete. The action is to create a pressure loss in either section I or section II. The expectation is that the local PLC will identify and take over the subsequent steps, completing the closed loop of switching and automatic reset. The SOE should reflect the takeover time and subsequent actions, with correct logic and no erroneous operation.

[0045] Record the command issuance and arrival times from both the PO software side and the local PLC side to verify whether takeover has been completed and the accuracy of the takeover. Secondly, after the network outage and system crash tests, reset each item according to the checklist to restore network and function shielding.

[0046] The test environment is set up using a spare Nanda Aotuo PLC CPU module to build a simulation environment. The software simulates undervoltage, switch positions, protection quantities and linkage points. Full simulation or semi-simulation tests are performed first, which is suitable for multiple rounds of regression and boundary verification. Alternatively, sixty-two sets of 6kV LCUs in operation can be used for semi-physical testing. By disconnecting the output relay or shielding the closing circuit, actual opening and closing are avoided. Undervoltage and switching tests are achieved by combining test sources or software point simulation. This must be carried out under the premise of permission window and safety measures in place.

[0047] The 400V transfer control module 6 is used to distribute the 400V of the main transformer low-voltage bus to the 6KV system control module 2, the measurement and control acquisition module 3, and the communication exchange module 4.

[0048] like Figure 3 As shown, the 400V transfer control module 6 includes isolating switches 1G, 2G, 3G, 4G, 5G, and 6G; collateralized air circuit breakers Q1, Q2, and Q3; AC contactors KM8 and KM9; a dual power supply circuit; a backup automatic transfer circuit; and a load device. The first incoming line is connected to the dual power supply circuit, one end of the AC contactor KM8, and one end of the isolating switch 1G. The other end of the isolating switch 1G is connected to the backup automatic transfer circuit, the load device, and one end of the isolating switch 5G in sequence through the collateralized air circuit breaker Q1 and the isolating switch 2G. The second incoming line is connected to the dual power supply circuit, one end of the AC contactor KM9, and one end of the isolating switch 3G. The other end of the isolating switch 3G is connected to the backup automatic transfer circuit, the load device, and one end of the isolating switch 6G in sequence through the collateralized air circuit breaker Q2 and the isolating switch 4G. The collateralized air circuit breaker Q3 is connected to the other end of the isolating switch 5G and the other end of the isolating switch 6G.

[0049] In this embodiment, seamless switching between the first and second incoming lines is achieved through two AC contactors, KM8 and KM9. Isolating switches 1G–4G, in conjunction with circuit breakers Q1 and Q2, ensure complete source isolation before each connection. Isolating switches 5G and 6G are linked with circuit breaker Q3 to cut off the cross feedback path of the two power supplies. The combination of multi-point isolating switches and circuit breakers effectively suppresses arcing and surge current during the switching process. The dual power supply circuit and the backup automatic transfer circuit run in parallel. When the main circuit loses power, it can automatically switch to the backup circuit to ensure that critical loads are not interrupted.

[0050] In one example, the conditions for sending the Q1 trip signal are: the I bus loses voltage and the Q1 pressure plate is activated, and the duration of the Q1 trip signal is 6 seconds. The conditions for issuing the Q2 trip signal are: the II busbar loses voltage and the Q2 pressure plate is engaged; the duration of the Q2 trip signal is 6 seconds. The automatic transfer switch (ATS) operation meets the following conditions (Q3): the ATS handle is engaged, any busbar is undervoltage, Q1 and Q2 are not both in the closed position, Q3 is in the open position, the zero-sequence protection of stage I and stage II is not activated, and the reverse ATS is not activated. After the conditions are met, a Q3 closing signal is sent after a 2-second delay. The conditions for sending the Q3 closing signal are that Q1 and Q2 are not both in the closed position, Q3 is in the open position, and the duration of the Q3 closing signal is 6 seconds. When the Q3 closing signal is sent, the standby automatic transfer action signal is also sent. After the Q3 closing signal is sent, the Q3 position contact is checked after 4 seconds. If it is still in the open position, the standby automatic transfer is judged to have failed. After the Q3 closing is successful, the program segment 37 signal is reset. The conditions for the Q3 switch to activate are: the automatic transfer switch lever is engaged, the reverse transfer switch lever is engaged, the I-section incoming line is energized, the II-section incoming line is energized, the automatic transfer switch is not activated, and Q3 is in the closed position. The Q3 signal is sent after a 2-second delay. The conditions for the reverse backup transfer to activate Q1 are: the automatic transfer switch is engaged, the reverse backup transfer switch is engaged, the I-section incoming line is energized, the II-section incoming line is energized, the automatic transfer switch is not activated, Q3 is in the open position, Q1 is in the open position, and the Q1 activation signal is sent after a 5-second delay. The conditions for the reverse backup transfer to activate Q2 are: the automatic transfer switch is engaged, the reverse backup transfer switch is engaged, the I-section incoming line is energized, the II-section incoming line is energized, the automatic transfer switch is not activated, Q3 is in the open position, and Q2 is in the open position. After a 5-second delay, the closing Q1 signal is sent. The duration of both the closing Q1 and Q2 signals is 6 seconds, and the duration of the opening Q3 signal is 6 seconds. The reverse backup transfer activation signal is sent simultaneously with the opening Q3 signal. The conditions for Q1 to open are: issuing a Q1 opening signal; the conditions for Q2 to open are: issuing a Q2 opening signal; the conditions for Q3 to close are: issuing a Q3 closing signal, Q1 or Q2 being in the open position, the zero-sequence protection of stage I or stage II not operating, and Q3 being in the open position. The conditions for Q1 to be combined are: Q1 is sent, Q3 is in the quantification position, and Q1 is in the quantification position. The conditions for Q2 to be combined are: Q2 signal is issued, Q3 is in the split position, and Q1 is in the split position. The conditions for Q3 tripping are either issuing a Q3 tripping signal, or the 6kV overcurrent tripping action and the 6kV overcurrent tripping Q3 pressure plate being engaged.

[0051] If Q1, Q2, and Q3 are all in the split position, and both the incoming lines of section I and section II are energized: 1. The backup automatic transfer meets the conditions of Q3, and the backup automatic transfer action meets Q3 after 2 seconds.

[0052] 2. After Q3 is closed, the conditions for the counter-backup shot Q3 are met, and the counter-backup shot Q3 is executed 2 seconds later.

[0053] 3. After Q3 is separated, it is still within the time of the backup switch lockout (6s), which satisfies the conditions of Q1 and Q2 for the backup switch. After 5s, the backup switch action combines Q1 and Q2.

[0054] Furthermore, the incoming circuit breaker for section I is designated Q1, the incoming circuit breaker for section II is designated Q2, and the bus tie circuit breaker is designated Q3. The mode switch SA has four positions: manual, zero position, automatic transfer with manual reset, and automatic transfer with automatic reset. The voltage relay is tested using two simulated threshold positions; 60 volts is commonly used to represent no voltage, and 120 volts and above represent voltage. The voltage loss confirmation delay is seven seconds. The technical interval between opening and closing actions is one second. During automatic reset, the bus tie remains in place for two seconds before opening.

[0055] General requirements before the test: 1. Confirm the test plan and identify the incoming line side requiring the drill. 2. Check that all three circuit breakers are in the working or test position, not in the disconnected or withdrawn position. 3. Ensure the circuit breakers are in a remote position, the control and protection circuits inside the cabinet are normal, and the PLC operation indication is normal. 4. Check that the mode selection meets the requirements of this test. 5. Check that the on and off voltage displays are consistent with the voltage relay input. 6. Ensure there are no manual tripping interlocks, no circuit breaker fault tripping interlocks, and no insufficient closing readiness conditions. 7. Confirm that the measurement and recording methods are in place and capable of recording SOE time.

[0056] Standard operating principles and success criteria: The operating sequence is to first disconnect the incoming line on the power failure side, then close the bus tie after a one-second delay. For automatic transfer and automatic reset, the bus tie is disconnected and held for two seconds before closing the incoming line on the restoration side and completing the reset. A maximum of two out of three circuit breakers are allowed to be in the closed position simultaneously. Automatic transfer should not occur if there is a blocking condition or if the conditions are not met. Success is demonstrated by correct operating sequence, delays meeting set values, no bypassing of cascading connections, and consistency between SOE and indication.

[0057] Automatic Transfer and Reset Experiment 1: Automatic transfer and reset triggered by stage I voltage loss: Initial state: Q1 closed, Q2 closed, Q3 open; mode: automatic transfer and reset; all three circuit breakers are in the working or test position. Maintain stage II voltage, and adjust the stage I voltage relay input to de-energized. After a seven-second confirmation, the system trips Q1, delays for one second, and then closes Q3, energizing the busbar via stage II. Subsequently, the stage I voltage is restored to positive and stabilized. Two seconds later, the system trips Q3, delays for another second, and then closes Q1, restoring the two incoming lines to separate operation. The test is deemed successful.

[0058] Self-transfer and self-recovery experiment two: Self-transfer and self-recovery triggered by stage II voltage loss: The initial state is the same as in experiment one. Maintain stage I voltage with positive voltage, and adjust stage II voltage to negative voltage. After a seven-second confirmation, the system trips Q2, and after a one-second delay, closes Q3. The stage II voltage is restored to positive voltage and stabilized. After two seconds, the system trips Q3, and after another one-second delay, closes Q2. The test is deemed successful.

[0059] Experiment 1: Automatic Transfer and Manual Reset - Section I Voltage Loss Triggers Automatic Transfer but Does Not Reset Automatically: Initial state: Q1 closed, Q2 closed, Q3 open; mode: automatic transfer and manual reset. Maintaining voltage in Section II, Section I is de-voltaged. After a seven-second confirmation, the system opens Q1 and closes Q3 after a one-second delay. Even if Section I regains voltage, the system maintains the Q1 open, Q2 closed, Q3 closed sequence, without automatic disconnection or return. If a voltage loss subsequently occurs in Section II, the system executes a reversal sequence: first opens Q2, then opens Q3, closes Q1 after a one-second delay, closes Q3 again after a one-second delay, and finally restores power supply from Section I.

[0060] Experiment 2: Automatic Transfer and Manual Reset - Stage II Voltage Loss Triggers Automatic Transfer but Does Not Automatically Reset: Initial conditions are Q1 closed, Q2 closed, Q3 open, mode is automatic transfer and manual reset. Stage I is kept under voltage, and Stage II is set to de-voltage. After a seven-second confirmation, the system opens Q2 and closes Q3 after a one-second delay. After Stage II regains voltage, it does not automatically reset, maintaining a parallel power supply mode with Q2 open, Q1 closed, and Q3 closed. If Stage I subsequently loses voltage, the system reverts to being powered by Stage II according to the switching sequence.

[0061] In automatic transfer and automatic reset mode, first reduce the voltage on one side to zero to trigger the standby automatic transfer, then raise that side to 120 volts or higher and maintain stability. The system should trip the bus tie after two seconds, then close the incoming line on that side after a one-second delay to complete the automatic reset. Perform this symmetrically on both sides once to confirm the consistency of the threshold and the back-off. In automatic transfer manual reset or automatic transfer and automatic reset mode, manually press the trip button to disconnect the incoming line switch that is currently supplying power, while confirming that the PLC has not issued a trip command and the protection has not issued a lockout. The system should determine that the manual trip is locked out and the standby automatic transfer function is locked out, and the mode indicator light will flash lockout. The reset method is to turn the mode switch to the zero position or manual position, close the manually tripped incoming line switch if necessary, and then put the automatic transfer mode back into operation.

[0062] If no feedback is received within five seconds after the incoming line tripping command is issued, the automatic transfer procedure should be deemed a failure and exited. Closing the bus tie should be prohibited, and an alarm should be issued and SOE recorded. If any circuit breaker is in the out or disconnected position, in the local position, in a state of no closing preparation, has a circuit breaker fault tripping lockout, or the PLC is not running, the system should not execute the backup automatic transfer action and should indicate that it is not ready or locked. When the 6kV side determines that the backup automatic transfer has failed, is locked, or has exited, or the upstream feeder switch has already tripped and there is no subsequent backup automatic transfer action, the 400V transfer control module can directly execute the incoming line tripping on the power failure side and close the bus tie after the technical interval without waiting for the seven-second power loss confirmation, in order to shorten the power outage time. When the 6kV side determines that an upstream electrical fault is unrecoverable and low-voltage side cross-section paralleling is not allowed, a lockout signal should be issued to the 400V side to prohibit the 400V backup automatic transfer triggered by the upstream power loss.

[0063] Key SOE (State of Emergency) time points need to be recorded, including the time of voltage loss confirmation, the time of issuance of each opening and closing command, and the time of arrival of each opening and closing position. Verify that the settings for seven-second confirmation, one-second interval, and two-second hold are met. Verify that the mode indication and voltage indication are consistent with the action process. The pass / fail criteria are: no false alarms, no bypassing of cascading circuits, and accurate action sequence and delay.

[0064] like Figure 4 As shown, the 400V transfer control module 6 also includes a PLC power supply circuit, which includes circuit breaker QF3, circuit breaker QF4, a power module, a switching power supply, and a CPU. The common terminal of circuit breakers QF3 and QF4 is connected to an external 220V AC power supply. The other terminal of circuit breaker QF3 is connected to a switching power supply. The switching power supply is connected to the dual power supply circuit, the backup automatic transfer circuit, and the load device. The power module is connected to the other terminal of circuit breaker QF4 and the CPU, respectively.

[0065] like Figure 5As shown, the dual power supply circuit includes circuit breaker QF1, circuit breaker QF2, AC contactor KM1, AC contactor KM2, AC contactor KM3, indicator light HR1, and indicator light HR2. One power supply is connected via circuit breaker QF1 to the coil of AC contactor KM3, one end of the normally open contact of AC contactor KM3, the coil of AC contactor KM1, one end of indicator light HR1, one end of the first normally open contact of AC contactor KM1, one end of the second normally open contact of AC contactor KM1, and one end of the third normally open contact of AC contactor KM1. The other end of the normally open contact of AC contactor KM3 is connected to the coil of AC contactor KM1 via the normally closed contact of AC contactor KM2. The other end of the first normally open contact of AC contactor KM1 is connected to the other end of indicator light HR1. Another power supply is connected via circuit breaker QF2 to one end of the first normally open contact of AC contactor KM2, one end of the indicator light HR1, and one end of the normally open contact of AC contactor KM2. One end of lamp HR2, one end of normally closed contact in AC contactor KM1, the coil of AC contactor KM2, one end of second normally open contact in AC contactor KM2, and one end of third normally open contact in AC contactor KM2 are connected. The other end of first normally open contact in AC contactor KM2 is connected to the other end of indicator light HR2. The other end of normally closed contact in AC contactor KM1 is connected to the coil of AC contactor KM2 through normally closed contact in AC contactor KM3. The common terminal of second normally open contact in AC contactor KM1 and second normally open contact in AC contactor KM2 is connected to the first incoming line. The common terminal of third normally open contact in AC contactor KM1 and third normally open contact in AC contactor KM2 is connected to the second incoming line.

[0066] like Figure 6 As shown, the 400V transfer control module 6 also includes a zero-sequence self-holding circuit. This circuit includes terminal block XT5, AC contactor KM10, zero-sequence overcurrent relay GL1, AC contactor KM11, normally closed pushbutton SB1, AC contactor KM12, zero-sequence overcurrent relay GL2, AC contactor KM13, and normally closed pushbutton SB2. The coil of AC contactor KM10 is connected to one end of zero-sequence overcurrent relay GL1 and terminal block XT5, respectively. The other end of zero-sequence overcurrent relay GL1 is connected to terminal block XT5. The first common terminal of the normally open contact of AC contactor KM10 and the normally open contact of AC contactor KM11 is connected to the coil of AC contactor KM10. The second common terminal of the normally open contact of AC contactor KM10 and the normally open contact of AC contactor KM11 is connected to the coil of AC contactor KM11. The coil of AC contactor KM11 is connected to terminal block XT5 through normally closed button SB1. The coil of AC contactor KM12 is connected to one end of zero-sequence overcurrent relay GL2 and terminal block XT5 respectively. The other end of zero-sequence overcurrent relay GL1 is connected to terminal block XT5. The first common terminal of the normally open contact in AC contactor KM12 and the normally open contact in AC contactor KM13 is connected to the coil of AC contactor KM12. The second common terminal of the normally open contact in AC contactor KM12 and the normally open contact in AC contactor KM13 is connected to the coil of AC contactor KM13. The coil of AC contactor KM13 is connected to terminal block XT5 through normally closed button SB2.

[0067] In this embodiment, once the zero-sequence relays GL1 / GL2 are activated, they self-close contactors KM10 / KM12 respectively. The self-holding contacts of KM11 / KM13 lock the state, ensuring that the fault signal will not reset even if it disappears momentarily. Zero-sequence detection and self-holding paths are set independently for each of the two power supplies, improving the coverage and reliability of grounding faults. Normally closed buttons SB1 and SB2 are placed in the self-holding circuit, which can be manually disconnected after the fault is cleared, realizing fault reset and system restart. The interlocking contacts between KM10 / KM11 (and KM12 / KM13) prevent mutual false excitation during opening / closing, eliminating false tripping or repeated operation caused by circuit jitter. The entire circuit is modularized and visualized. The self-holding circuit maintains the fault state until manual reset, effectively preventing power supply with faults and facilitating fault analysis and on-site maintenance.

[0068] In one example, the compatibility of the 400V transfer control module was tested using the PO software logic function. The test objects included the PO software, the 6kV system control and integrated protection, and the local PLCs for each 400V section. Section I and Section II are the 400V input lines on both sides; Section I and Section II are the two 6kV sections; there are two modes: automatic transfer and automatic reset, and automatic transfer and manual reset; the standard 400V undervoltage confirmation delay is seven seconds, which can be skipped under integrated acceleration conditions.

[0069] The test objectives and scope are: First, to verify the correctness of the 400V automatic transfer and automatic reset logic built into the PO software; second, to verify whether each 400V local PLC can independently take over and complete the backup automatic transfer when the PO software does not operate or the operation process is incomplete. Third, to verify whether, under integrated linkage conditions, the 400V side can act in advance without waiting seven seconds in cases such as 6kV side backup automatic transfer failure, lockout, exit, or lack of subsequent backup automatic transfer from the upstream feeder. Fourth, to confirm that both test environment setup methods can achieve repeatable simulation or semi-physical integration debugging.

[0070] General prerequisites and success criteria: 1. All involved circuit breakers are in the working or test position, remotely effective, and without being deactivated or disconnected. 2. There are no manual tripping interlocks, no circuit breaker fault tripping interlocks, and no insufficient closing preparation; the PLC and PO processes are in the established state. 3. The voltage relay or test source can stably output the simulated voltage and no-voltage levels. 4. SOE and network log are enabled and can record key timestamps. 5. Success criteria include correct action sequence, delay meeting settings, consistent lighting and display, the 400V side accelerating or locking as expected after the linkage condition is triggered, and no over-level paralleling or malfunctioning.

[0071] Under different operating conditions, two types of observation points are used. The first type is whether the actions of the PO software are executed as designed. The second type is whether each 400V local PLC can take over and complete the automatic transfer switch when the PO software does not operate or operates incompletely. If necessary, scenarios of "PO not participating" or "PO partially participating" are created by means of shielding, disconnecting the network, or simulating a system crash. Test preparation includes shielding the automatic transfer-related function blocks in each 400V local PLC or putting them in the exit state to ensure that the PO software dominates the field; and enabling the automatic transfer and automatic reset functions of stage I and stage II in the PO software respectively. Thirdly, the settings such as the seven-second voltage loss confirmation, switching interval, and bus tie maintenance before automatic reset are set to be consistent with the field.

[0072] The first method is automatic reset of Section I. Simulate a Section I voltage loss; after seven seconds, the PO software should issue a command to trip the Section I incoming line and simultaneously shut down the bus. Once the Section I voltage stabilizes, the bus tie should be maintained for two seconds before closing the Section I incoming line to complete the automatic reset. The second method is automatic reset of Section II. The method is the same as above, with symmetrical verification. The third method is manual reset of Section I. Simulate a Section I voltage loss, execute the tripping of the incoming line and simultaneous shut-down of the bus, and do not automatically return after power is restored; subsequently, if Section II experiences another voltage loss, power should be restored to Section I according to the switching sequence. The fourth method is manual reset of Section II. Symmetrical verification.

[0073] When the PO software does not operate or operates incompletely, to verify whether each 400V local PLC can independently complete the automatic transfer switch, the following scenarios are included: Scenario 1: The PO software is completely inactive, and the local PLC takes over. Verification methods include disabling the automatic transfer switch function in the PO software, simulating a PO software process crash, or disconnecting the network cables from the two Ethernet modules of the 400V control system to interrupt communication between the PO and the PLC. The action is to simulate an incoming line loss of voltage in either stage I or stage II. The expected outcome is that the PO side does not issue any commands, and each 400V local PLC independently completes the tripping of the incoming line on the power failure side and the bus joint switching after a seven-second confirmation, as well as the subsequent strategies of automatic transfer and manual reset. The record shows that the PO has no relevant SOE, while the PLC side has a complete SOE, indicating correct action.

[0074] Scenario 2: The PO software's action flow is incomplete, and the local PLC continues the process. Verification involves triggering only the first half or stopping midway through the automatic transfer switch process in the PO software, making the flow incomplete. The action is to simulate incoming line undervoltage in section I or II. The expectation is that the local PLC will identify the incomplete flow and take over subsequent steps to ensure a complete closed loop for the automatic transfer switch. The record shows that the PO-side process terminates midway, and the PLC completes the action and provides feedback.

[0075] When the acceleration conditions for integrated medium and low voltage are met, the 400V side can act ahead of time without a seven-second delay; when the upper-level interlocking conditions are met, the 400V side should lock the automatic transfer switch triggered by the upper-level power failure. The automatic transfer switch functions for the 6kV I and II sections in the PO software are activated, along with the automatic transfer switch functions for each 400V section I and II, enabling the integrated interlocking logic.

[0076] Scenario 1: The 6kV main section's automatic transfer switch fails. The steps include simulating a voltage loss in section I and initiating its automatic transfer switch while simultaneously setting the "automatic transfer switch failure" signal; then repeating this process for section II. The expected outcome is that the corresponding 400V section, upon receiving the failure criterion, will skip seven seconds for confirmation, prematurely execute the incoming line tripping and busbar combination switching, and meet interlocking and sequence requirements.

[0077] Scenario 2: A blocking signal for automatic transfer switch is present in the 6kV section. The procedure includes manually issuing a blocking signal for automatic transfer switch to section I, followed by tripping or undervoltage handling on the corresponding 400V section's upstream feeder. The expected behavior is that the integrated logic triggers an early action on the 400V side according to the design. If the scheme stipulates that blocking indicates the upper-level controller will no longer process the signal and authorizes the lower-level controller to accelerate, then the 400V side should act early; if the scheme stipulates that blocking simultaneously prohibits lower-level controllers from crossing the line, then the 400V side should be blocked and not act. Each clause of the linkage rules in the final project draft should be checked and recorded. This should be executed symmetrically for section II.

[0078] Operating Condition 3: The 6kV main section's automatic transfer switch is deactivated. The procedure includes manually deactivating the automatic transfer switch for section I, followed by tripping or undervoltage at the corresponding 400V section's upstream feeder side. The expected outcome is that the corresponding 400V side will operate ahead of schedule according to the integrated rules. This will be executed symmetrically for section II.

[0079] Condition 4: The upstream feeder loses voltage and there is no subsequent automatic transfer switch action. The steps include setting the upstream feeder to lose voltage and confirming that there is no subsequent automatic transfer switch action. It is expected that the corresponding 400V side will not need to wait seven seconds and will execute the automatic transfer switch in advance.

[0080] Clearly define the acceleration or interlocking rules and evidence points for each operating condition, including the higher-level state variables, linkage soft points, and 400V side SOE, and verify whether the advance action truly skips the seven-second delay. Thirdly, verify whether the protection interlocks of abnormal branches intercept erroneous parallel connections.

[0081] The test environment is set up using a spare M580 CPU and necessary I / O and network modules. Software simulates input / output and linkage points to construct a fully virtual or semi-virtual environment to replay various operating conditions, suitable for multi-round regression testing and boundary condition verification. Alternatively, an existing 400V power distribution system PLC can be used for on-site or semi-physical simulation testing. By disconnecting the switching relay or shielding the closing circuit, actual switching is avoided, and the switching between voltage and no-voltage states is achieved by combining the analog input of the voltage relay.

[0082] In one example, the 400V transfer control module 6 includes multiple 400V distribution cabinets, and the I / O module configuration is one DI32-point digital input module, one DO32-point digital output module, and two NOP0300 Ethernet modules.

[0083] Please see Figure 7 and Figure 8 When the 400V transfer control module controls three MT frame circuit breakers (two incoming circuit breakers and one bus tie circuit breaker), these three circuit breakers form a single busbar segmented power distribution structure. Under any circumstances, a maximum of two circuit breakers are allowed to be in the closed state simultaneously. This logic is implemented by electrical interlocking and the PLC program. The positions of the three circuit breakers corresponding to the automatic transfer mode are: all in the working position, all in the test position, or each in either the working or test position. If any circuit breaker is in the disconnected position, the automatic transfer function will not take effect. The working mode is selected via the selector switch SA on the bus tie cabinet. SA has four positions: "Manual," "0," "Automatic Transfer Manual Reset," and "Automatic Transfer Automatic Reset."

[0084] Manual operation refers to opening and closing the circuit breaker using the electrical buttons on the switchgear. This position is also used to reset the "automatic transfer interlock". When SA is in position 0, the circuit breaker cannot be manually closed, and the automatic transfer function is also disabled. This position is also used to reset the "automatic transfer interlock".

[0085] Automatic Transfer Switch Manual Reset: When both incoming lines are energized, the bus tie circuit breaker is open and both incoming line circuit breakers are closed. If power to one incoming line disappears, that incoming line circuit breaker will automatically open, and the bus tie circuit breaker will close. It will not automatically reset when power to the lost incoming line is restored, but it will automatically reset when power to the other incoming line disappears. For manual reset, first open the bus tie circuit breaker, then close the incoming line circuit breaker. This operation can be performed in both "Automatic Transfer Switch Manual Reset" and "Manual" modes.

[0086] Automatic transfer and automatic reset: When both incoming lines are energized, the bus tie circuit breaker is open and both incoming line circuit breakers are closed. If power to one incoming line is lost, the circuit breaker of that incoming line will automatically open and the bus tie circuit breaker will close. When power to the lost incoming line is restored, the bus tie circuit breaker will automatically open and the incoming line circuit breaker will close.

[0087] The bus tie cabinet has three indicator lights related to automatic transfer switching: The PLC operation indicator light is green; a solid green light indicates the PLC is running, and an off light indicates the PLC is not running. The automatic transfer manual reset indicator light is blue; a solid green light indicates the "automatic transfer manual reset" mode is active, and a flashing light indicates the mode is disabled or the automatic transfer is locked, meaning the system does not have automatic transfer functionality. The automatic transfer automatic reset indicator light is blue; a solid green light indicates the "automatic transfer automatic reset" mode is active, and a flashing light indicates the mode is disabled or the automatic transfer is locked, meaning the system does not have automatic transfer functionality.

[0088] Automatic transfer switch lockout caused by manual circuit breaker disconnection: In "Automatic Transfer Manual Reset" or "Automatic Transfer Automatic Reset" mode, if a circuit breaker that is currently supplying power is manually disconnected, the system considers this to be intentional for safety reasons and therefore prohibits subsequent automatic transfer and reset functions, i.e., "Automatic Transfer Lockout". Simultaneously, the "Automatic Transfer Manual Reset" and "Automatic Transfer Automatic Reset" indicator lights will flash, indicating that although SA is in the "Automatic Transfer Manual Reset" or "Automatic Transfer Automatic Reset" position, its automatic transfer function has been locked out. To unlock, rotate SA to the "0" position or "Manual" position, or manually close the circuit breaker that was just manually disconnected in "Automatic Transfer Manual Reset" mode.

[0089] Automatic transfer switch (ATS) lockout due to circuit breaker fault tripping: In "Automatic Transfer Manual Reset" or "Automatic Transfer Automatic Reset" mode, the ATS function is locked out when any circuit breaker trips due to a fault. Simultaneously, the "Automatic Transfer Manual Reset" and "Automatic Transfer Automatic Reset" indicator lights flash, indicating that although SA is in the "Automatic Transfer Manual Reset" or "Automatic Transfer Automatic Reset" position, its ATS function has been locked out. To unlock the circuit breaker, reset the fault and then rotate SA to the "0" position or "Manual" position.

[0090] Voltage relays: The contact signals of the voltage relays are sent to the PLC to determine the status of the incoming power supply. Each incoming line is equipped with 3 single-phase voltage relays. The incoming power supply is considered to be lost only when all 3 relays issue a power failure signal, in order to prevent unnecessary automatic switching of the system caused by the failure of one or two relays or the blown protection fuse.

[0091] Operation and maintenance management module 5 includes a data acquisition unit, a historical storage and analysis unit, a fault diagnosis unit, and a human-computer interaction unit. The data acquisition unit polls the real-time data of the measurement and control acquisition module 3 and the 6KV system control module 2 via the OPC UA client or Modbus TCP; the historical storage and analysis unit uses a time-series database to store current, voltage, switching counts and alarm events, and automatically generates an operation evaluation report based on preset thresholds; the fault diagnosis unit imports fault waveform files reported by the 6KV system integrated protection module 1 to perform offline fault playback and location operations; the human-machine interaction unit supports remote parameter distribution and permission management.

[0092] In this embodiment, the 6kV system integrated protection module can collect the voltage and current of the bus incoming and outgoing lines in real time. Once an abnormal fault is detected, a trip command can be sent to the communication exchange module 4 in milliseconds. The linkage control module and the measurement and control acquisition module 3 complete the fault isolation, significantly shortening the fault clearing time. The measurement and control acquisition module 3 works in conjunction with the 6kV control module and can automatically drive the circuit breaker and bus tie switch according to the operating status and opening / opening commands to realize automatic switching between medium and low voltage sides and automatic backup transfer, ensuring the continuity of power grid operation and power supply reliability. The communication exchange module 4 electrically connects and uniformly schedules the five major functional units of integrated protection, control, acquisition, operation and maintenance and 400V transfer control, simplifying the system architecture and improving deployment flexibility and field scalability. At the same time, the 400V transfer control module 6 directly draws power from the transformer's low-voltage bus to provide an independent and stable auxiliary power supply for each measurement and control and communication unit, ensuring that each module can still maintain key control and communication functions when the main power supply is abnormal, thereby enhancing anti-interference capability and self-recovery capability.

[0093] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A medium- and low-voltage integrated power distribution automatic transfer switch intelligent monitoring and control system, characterized in that, It includes a 6KV system integrated protection module (1), a 6KV system control module (2), a measurement and control acquisition module (3), a communication exchange module (4), an operation and maintenance management module (5), and a 400V transfer control module (6), among which, The communication switching module (4) is electrically connected to the 6KV system integrated protection module (1), the 6KV system control module (2), the measurement and control acquisition module (3), the operation and maintenance management module (5), and the 400V transfer control module (6), respectively. The 6KV system integrated protection module (1) is used to collect the incoming and outgoing line voltage and current of the 6kV bus, and in the event of a fault, it sends a trip command to the communication exchange module (4) to adjust the 6KV system control module (2) and the measurement and control acquisition module (3) accordingly. The 6KV system control module (2) is used to receive the opening / opening command from the measurement and control acquisition module (3) to drive the 6kV circuit breaker and bus tie switch in the 6KV system integrated protection module (1); The measurement and control acquisition module (3) is used to acquire the voltage, current, switch position and low-voltage bus status of the 6KV system protection module (1) and the 400V transfer control module (6), and send corresponding control commands to the 6KV system protection module (1), the 6KV system control module (2), the operation and maintenance management module (5) and the 400V transfer control module (6); The 400V transfer control module (6) is used to distribute the 400V of the main transformer low-voltage bus to the 6KV system control module (2), the measurement and control acquisition module (3), and the communication exchange module (4).

2. The integrated medium- and low-voltage power distribution automatic transfer intelligent monitoring and control system as described in claim 1, characterized in that, The tripping or closing commands of the 6KV system integrated protection module (1) and the 6KV system control module (2) are transmitted using IEC 61850 GOOSE high-speed messages, and the message period is less than 4 ms. The protection action record and fault waveform are reported to the measurement and control acquisition module (3) through IEC 61850 MMS or Modbus TCP.

3. The integrated medium- and low-voltage power distribution automatic transfer intelligent monitoring and control system as described in claim 1, characterized in that, The backup automatic switching logic in the measurement and control acquisition module (3) includes: When the incoming bus in the 6KV system integrated protection module (1) or the 400V transfer control module (6) loses voltage and continues for a preset delay, the measurement and control unit first sends a bus tie closing command, and then automatically returns after the main power supply is restored; Alternatively, when the incoming line of the 6KV system integrated protection module (1) or the 400V transfer control module (6) loses voltage, only the bus tie closing command is issued and the return trip is not performed; Alternatively, it can disable any automatic tripping or closing operations and issue an alarm when the integrated low-voltage power distribution backup automatic transfer intelligent monitoring and control system malfunctions.

4. The integrated medium- and low-voltage power distribution automatic transfer intelligent monitoring and control system as described in claim 1, characterized in that, The measurement and control acquisition module (3) exchanges monitoring data and configuration parameters with the operation and maintenance management module (5) via Modbus / TCP or OPC UA.

5. The integrated medium- and low-voltage power distribution automatic transfer switch intelligent monitoring and control system as described in claim 1, characterized in that, The operation and maintenance management module (5) includes a data acquisition unit, a historical storage and analysis unit, a fault diagnosis unit, and a human-computer interaction unit, wherein, The data acquisition unit polls the real-time data of the measurement and control acquisition module (3) and the 6KV system control module (2) through the OPC UA client or Modbus TCP; the historical storage and analysis unit uses a time-series database to store current, voltage, number of switching and alarm events, and automatically generates an operation evaluation report according to a preset threshold; the fault diagnosis unit imports the fault waveform file reported by the 6KV system integrated protection module (1) to perform offline fault playback and location operations; the human-machine interaction unit supports remote parameter distribution and permission management.

6. The integrated medium- and low-voltage power distribution automatic transfer intelligent monitoring and control system as described in claim 1, characterized in that, The 400V transfer control module (6) includes isolating switches 1G, 2G, 3G, 4G, 5G, and 6G; collateralized air circuit breaker Q1, Q2, and Q3; AC contactor KM8 and KM9; a dual power supply circuit; a backup automatic transfer circuit; and a load device. The first incoming line is connected to the dual power supply circuit, one end of the AC contactor KM8, and one end of the isolating switch 1G. The other end of the isolating switch 1G is connected to the backup automatic transfer circuit, the load device, and one end of the isolating switch 5G via the collateralized air circuit breaker Q1 and the isolating switch 2G. The second incoming line is connected to the dual power supply circuit, one end of the AC contactor KM9, and one end of the isolating switch 3G. The other end of the isolating switch 3G is connected to the backup automatic transfer circuit, the load device, and one end of the isolating switch 6G via the collateralized air circuit breaker Q2 and the isolating switch 4G. The collateralized air circuit breaker Q3 is connected to the other ends of the isolating switches 5G and 6G.

7. The integrated medium- and low-voltage power distribution automatic transfer intelligent monitoring and control system as described in claim 6, characterized in that, The dual power supply circuit includes circuit breaker QF1, circuit breaker QF2, AC contactor KM1, AC contactor KM2, AC contactor KM3, indicator light HR1, and indicator light HR2. One power supply is connected via circuit breaker QF1 to the coil of AC contactor KM3, one end of the normally open contact of AC contactor KM3, the coil of AC contactor KM1, one end of indicator light HR1, one end of the first normally open contact of AC contactor KM1, one end of the second normally open contact of AC contactor KM1, and one end of the third normally open contact of AC contactor KM1. The other end of the normally open contact of AC contactor KM3 is connected to the coil of AC contactor KM1 via the normally closed contact of AC contactor KM2. The other end of the first normally open contact of AC contactor KM1 is connected to the other end of indicator light HR1. Another power supply is connected via circuit breaker QF2 to one end of the first normally open contact of AC contactor KM2, the indicator light HR1, and the third normally open contact of AC contactor KM1. One end of the lamp HR2, one end of the normally closed contact in the AC contactor KM1, the coil of the AC contactor KM2, one end of the second normally open contact in the AC contactor KM2, and one end of the third normally open contact in the AC contactor KM2 are connected. The other end of the first normally open contact in the AC contactor KM2 is connected to the other end of the indicator light HR2. The other end of the normally closed contact in the AC contactor KM1 is connected to the coil of the AC contactor KM2 through the normally closed contact in the AC contactor KM3. The common terminal of the second normally open contact in the AC contactor KM1 and the second normally open contact in the AC contactor KM2 is connected to the first incoming line. The common terminal of the third normally open contact in the AC contactor KM1 and the third normally open contact in the AC contactor KM2 is connected to the second incoming line.

8. The integrated medium- and low-voltage power distribution automatic transfer switch intelligent monitoring and control system as described in claim 1, characterized in that, The 400V transfer control module (6) also includes a zero-sequence self-holding circuit, which includes terminal block XT5, AC contactor KM10, zero-sequence overcurrent relay GL1, AC contactor KM11, normally closed pushbutton SB1, AC contactor KM12, zero-sequence overcurrent relay GL2, AC contactor KM13, and normally closed pushbutton SB2. The coil of AC contactor KM10 is connected to one end of zero-sequence overcurrent relay GL1 and terminal block XT5, respectively. The other end of zero-sequence overcurrent relay GL1 is connected to terminal block XT5. The first common terminal of the normally open contact of AC contactor KM10 and the normally open contact of AC contactor KM11 is connected to the coil of AC contactor KM10. The second common terminal of the normally open contact of AC contactor KM10 and the normally open contact of AC contactor KM11 is connected to the coil of AC contactor KM11. The coil of AC contactor KM11 is connected to terminal block XT5 through normally closed button SB1. The coil of AC contactor KM12 is connected to one end of zero-sequence overcurrent relay GL2 and terminal block XT5, respectively. The other end of zero-sequence overcurrent relay GL1 is connected to terminal block XT5. The first common terminal of the normally open contact in AC contactor KM12 and the normally open contact in AC contactor KM13 is connected to the coil of AC contactor KM12. The second common terminal of the normally open contact in AC contactor KM12 and the normally open contact in AC contactor KM13 is connected to the coil of AC contactor KM13. The coil of AC contactor KM13 is connected to terminal block XT5 through normally closed button SB2.

9. The integrated medium- and low-voltage power distribution automatic transfer switch intelligent monitoring and control system as described in claim 6, characterized in that, The 400V transfer control module (6) also includes a PLC power supply circuit, which includes circuit breaker QF3, circuit breaker QF4, a power module, a switching power supply, and a CPU. The common terminal of circuit breaker QF3 and circuit breaker QF4 is connected to an external 220V AC power supply. The other end of circuit breaker QF3 is connected to a switching power supply. The switching power supply is connected to the dual power supply circuit, the backup automatic transfer circuit, and the load device. The power module is connected to the other end of circuit breaker QF4 and the CPU, respectively.

10. The integrated medium- and low-voltage power distribution automatic transfer switch intelligent monitoring and control system as described in claim 1, characterized in that, The communication switching module (4) supports one or more of VLAN, QoS, link aggregation, IEC 61850 GOOSE / MMS, Modbus TCP and OPCUA.

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