Late at night, the lights of thousands of homes went out one after another, and people who had been tired all day fell asleep, and at this time, the pilot project of power supply transformation of a subway platform door had just started.

As the primary load of urban rail transit, the power supply of the platform door is directly related to driving safety and passenger travel, and all construction is strictly locked in the subway shutdown window period from 01:20 to 04:50 every day, and the whole process follows the operation principle of "every second counts, interlocking", taking into account construction efficiency and operational safety, and finally realizes zero operational impact and stable compliance with the whole system during the transformation.

01:20-01:30|Standardize power outage

After clarifying that the back-end load can be safely powered off, the construction team immediately starts the power-off operation, and the whole process is accurate, compliant, efficient and orderly. The operators are dressed in reflective tooling and operate one by one under the light in the cabinet, strictly following the preset switch state requirements: disconnect the drive distribution cabinet switch and the control integrated cabinet switch in turn; Then turn off the relevant switches of the rectifier module; Finally, the Emerson UPS system shutdown was completed according to the procedures, including disconnecting the UPS input, output and battery switch to ensure the safety of the whole link of power off.

At 01:30, all power-off operations were completed on time to build a solid safety defense line for subsequent operations.

01:30-02:20|Temporary power supply guarantee

In order to maintain the basic function of the platform door system and avoid power supply faults during the transformation, the construction team quickly carried out the construction of temporary power supply links, directly connected the AC mains power to the input bus of the rectifier module, and built a reliable temporary power supply system: the drive load is provided by the mains power through the rectifier module to meet the core needs of platform door drive; The control loop maintains dual DC 24V power supply to ensure the normal transmission of control signals, one of which drives the AC/DC centralized cabinet to supply power, continuing the original dual-channel support mode on site; The industrial computer is directly powered by AC220V mains power to ensure uninterrupted equipment monitoring. After the operation is completed, the team performs insulation testing and power-on verification one by one to confirm that the power supply of each circuit is stable and abnormal, providing a safe and reliable power supply foundation for subsequent equipment dismantling and installation.

02:20—04:30|Equipment iteration installation

This link is the core of night construction, and the construction team divides labor and cooperates, promotes efficiently, and maximizes the use of the limited window period.

The first step is to dismantle the old equipment: accurately dismantle the original UPS cabinet, transformer and control rectifier module, carefully clean the cabinet base and residual cables to ensure that there are no debris leftovers, wireless circuits are loose, and avoid affecting the installation of new equipment;

In the second step, the new cabinet is in place: the new intelligent power cabinet (including pre-installed drive modules, DC/DC modules, two strings of two parallel diodes and battery management units, etc.) is accurately hoisted to the original UPS position, and the construction personnel work together to adjust the positioning and fix it firmly;

The third step, preliminary debugging: complete the cabinet terminal verification, circuit combing and preliminary insulation inspection, confirm the installation specifications of the new cabinet, and the prefabricated modules are well connected. Thanks to the modular factory pre-installation design, the on-site installation efficiency is greatly improved, and the whole process is standardized and orderly, with no potential safety hazards.

04:30-04:50|Re-inspection and emergency standby

In the final stage of the night construction, the team carried out a comprehensive re-inspection before powering on, confirming the firmness of the equipment connection, the complete inventory of construction tools, and the reliability of the grounding system one by one, so as to eliminate any omissions in details. At the same time, the mobile emergency power supply vehicle is stationed next to the ATS switching box throughout the whole process, with DC110V/200A, DC24V/120A and 24-60V/6A multi-channel output capabilities, and the wiring port is preset in advance and can be quickly connected, forming a double guarantee of "new cabinet + emergency power supply" to ensure that the subway operation is not affected in any way the next day.

Follow-up improvement and system verification

During the day the next day, the construction team transferred to the battery transformation process, and the whole process was meticulous and accurate: lay insulation and leak-proof trays in the battery cabinet (corresponding to 1 for each battery), adjust the battery shelf to 3 layers, and accurately arrange the new battery pack according to the drawings; Install GDB2-12V battery acquisition unit and GDB2-U concentrator, connect the battery interconnection wire, inspection sampling line and main loop communication line one by one, and repeatedly check the polarity and firmness of the wiring to ensure the normal operation of the battery management system.

On the night of the third day, the construction team once again entered the shutdown window period and completed the full connection between the new power cabinet and the AC/DC centralized cabinet and the control integration cabinet, including AC input link, DC output bus, dry contact fault signal (main power failure, module failure, etc.) and RS232 communication interface (Modbus protocol), reconstructing the fault alarm system to ensure accurate upload of background signals.

System-wide joint debugging test results

After the transformation was completed, the team carried out system-wide joint commissioning tests, and all indicators met the design specifications:

1. The platform door opens and closes normally, and the response is accurate;
2. The three-level control function of PSC/PSL/IBP is effective and the control is smooth;
3. The battery charge and discharge, voltage and current monitoring and internal resistance detection are normal, and the charging state can be manually switched;
4. Stable background signal upload, accurate and reliable dry contact fault alarm;
5. After the transformation, the equipment runs stably for 72 consecutive hours, without any abnormal alarm records, and successfully completes the pilot transformation task.

This pilot strictly follows the standardized process of "power outage-temporary power supply-dismantling-installation-re-inspection", and realizes the safety iteration of equipment within a limited window period, without affecting the next day's operation.

In the whole transformation, the construction team efficiently completed the equipment iteration within a limited window period with the execution of every second and the rigor of interlocking, and guarded the "lifeline" of urban rail transit with professionalism and perseverance.