Interlocking Systems

Interlocking systems are designed to prevent unsafe operations in the switchyard by ensuring that equipment is operated in a predetermined sequence. This is crucial for maintaining operational safety and preventing damage to equipment.

1. Mechanical Interlocking

   • Principle: Uses physical locks and keys to enforce safe operating sequences.
   • Application: Commonly used in older switchyards and in situations where simple, robust solutions are required.

2. Electrical Interlocking

   • Principle: Uses electrical circuits and relays to control the operation sequence of switchyard equipment.
   • Components:
     • Interlock Relays: Prevent the operation of certain equipment until predefined conditions are met.
     • Auxiliary Contacts: Provide status feedback to the control system.
   • Example: Preventing the closing of a circuit breaker until the associated isolator is closed.

3. Logical Interlocking

   • Principle: Uses software logic to enforce interlocking rules.
   • Integration: Implemented in PLCs or SCADA systems.
   • Advantages: Provides greater flexibility and can handle complex interlocking schemes.

4. Key Interlocking Systems

   • Principle: Combines mechanical and electrical interlocking using keys that control access to operation points.
   • Usage: Common in high-security environments where multiple levels of interlocking are required.