With the rapid development of urban rail transit systems, safety has become a top priority in operation management. Rail transit facilities involve many electrical, mechanical and signal systems, and any mistake may lead to serious accidents. Therefore, how to build a control and protection system that is both safe and efficient is the focus of continuous attention in the industry. In this context, Trapped Key Interlocking is being widely used in the rail transit industry due to its advantages such as simple structure, high reliability, and no need for power control.
This article will deeply explore the principles, composition, typical application scenarios and practical advantages of the trapped key interlocking system in the rail transit industry.
1. What is trapped key interlocking?
Trapped key interlocking is a physical interlocking system with "key management" as its core. Its core concept is that before a specific safety operation is completed, the key is always "trapped" and cannot be operated subsequently. The operation sequence control and access permission restriction are enforced through mechanical structure.
1.1 Working principle
The trapped key interlocking system usually consists of multiple mechanical interlocking units, each of which contains one or more pluggable keys. Only when an operation is completed and the relevant key is released can the next operation step be continued. The entire system relies on the "key transfer" and "key trapping" logic to achieve physical level control of the equipment status and avoid operational errors.
1.2 Main components
Key: The core transmission medium of system operation, with a unique code.
Key Switch: Connected to the electrical system, often used for signal linkage.
Bolt Lock: Used to lock mechanical positions, such as circuit breakers, switches, etc.
Key Exchange Box: Perform multi-key distribution and recycling management.
2. Security challenges in the rail transit industry
The rail transit system is a highly complex system engineering, and its operation involves many types of equipment, such as traction substations, trackside equipment, electric switch machines, signal systems, turnout control systems, communication systems, etc. During equipment maintenance and operation, if there is no strict operation sequence control and authority management, the following safety hazards are very likely to occur:
Misoperation: If you enter the high-voltage distribution cabinet without turning off the power, it may cause electric shock to personnel.
Double operation: In the same track section, multiple work groups concurrently operate and cause equipment conflicts.
Unauthorized access: Unauthorized personnel enter the trackside equipment area or vehicle maintenance workshop, threatening equipment and personal safety.
Signal confusion: Switching track signals before confirming the equipment status may cause train operation risks.
In order to avoid these problems, mandatory sequential operation control must be implemented, and trapped key interlocking is the ideal choice to meet such needs.
3. Typical application scenarios of trapped Key Interlocking in rail transit
3.1 Maintenance and overhaul of traction substations
Traction substations undertake the important task of supplying power to trains, with high voltage and high danger. The trapped key interlocking system can be used for the following process control:
Before performing maintenance operations, the main power switch must be disconnected through the trapped key interlocking system to release the corresponding key;
The released key must be inserted into the lock tongue device to open the high-voltage distribution cabinet door;
After the overhaul is completed, the door lock must be closed, the key must be taken out, and then returned to the main switch before power can be re-powered.
Through the above operations, it is ensured that the power supply cannot be restored before the maintenance is completed, and the possibility of wrong power supply is fundamentally eliminated.
3.2 Safe access control of trackside equipment cabinets
Trackside control cabinets are usually deployed on the side of the track to connect key equipment such as signals and turnouts. The trapped key interlocking system can be used in the following scenarios:
Staff need to use the trapped key interlocking key to open the equipment cabinet;
The key is trapped after insertion and cannot be pulled out;
The key can only be pulled out to restore the control system after the cabinet door is completely closed and locked;
The same key can control multiple levels of operation permissions to prevent unauthorized entry.
This design not only avoids misoperation during maintenance, but also traces the responsibility of operators.
3.3 Maintenance of electric switch machines and turnouts
When maintaining turnouts or electric switch machines, it is necessary to ensure that trains on the track cannot enter the relevant operation area. The trapped key interlocking system can realize the following linkage logic:
The operator sets the turnout to the "maintenance lock" state through the trapped key interlocking system;
The track operation area can only be entered after the corresponding key is released;
If the key is not returned, the signal system cannot switch the turnout to the operation state;
After the operation is completed, the original state is restored, the key is returned, and the system automatically unlocks the operation permission.
This interlocking strategy ensures the hard safety rule of "trains cannot enter unless people leave the track".
3.4 Access control of the depot/subway maintenance workshop
The depot or maintenance workshop must ensure that no personnel enter at will or the train starts by mistake during the train maintenance. The trapped key interlocking system can realize:
The staff can only open the maintenance area security door with the key;
Once the door is opened, the train control system is in a locked state;
After the personnel leave the area, they must close the door and return the key to release the train start lock.
This method is particularly suitable for subway depots with multiple stations and multiple areas operating simultaneously, effectively reducing the risk of misoperation and personal injury.
4. Advantages of the trapped key interlocking system in the rail transit industry
4.1 Passive design, adaptable to extreme environments
The trapped key interlocking system is a mechanical design that does not require power drive. It is suitable for complex working conditions such as humidity, high temperature, dust, vibration, etc. It is an ideal choice for outdoor or underground equipment in rail transit.
4.2 Forced sequence control to prevent misoperation
Through the "trapping" and "release" mechanism of the key, the operator is forced to operate in a predetermined order, effectively avoiding skipping steps or missing links.
4.3 Clear authority management and traceable responsibility
Different key codes correspond to different authorities. Through the trapped key interlocking system, clear management of "who has the right to do what" can be achieved, and auditing can be carried out in conjunction with the entry and exit record system.
4.4 Flexible system expansion and easy maintenance
The modular design of the trapped key interlocking system is easy to integrate with the original system. If new equipment is added in the future, only the corresponding lock tongue and key components need to be expanded without changing the overall structure.
The Trapped Key Interlocking system provides a solid guarantee for the safe operation of rail transit with its unique mechanical interlocking mechanism. Through its wide application in multiple scenarios such as power distribution systems, trackside equipment, signal turnouts, and maintenance workshops, rail transit operators can effectively avoid misoperation, control access rights, and improve security levels. With the continuous improvement of industry safety standards, the trapped key interlocking system will surely play a more important role in the field of rail transit.
As a professional trapped key interlocking seller, we are well aware of the high standards of safety and operating specifications in the rail transit industry. We supply trapped key interlocking that meets international safety standards, has high reliability and adaptability, and can be customized according to customer needs. It is widely used in key scenarios such as traction substations, turnout control, trackside equipment and vehicle depot maintenance. Through mandatory operation sequence control and physical level permission management, it helps rail transit operators effectively prevent misoperation and unauthorized access, greatly improving overall operational safety and efficiency.
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