Modular Integrated Structure
Highly Integrated Functional Units: Core components-such as circuit breakers, voltage transformers (PTs), isolating contacts, and surge arresters-are integrated with operating mechanisms and contact systems into a single unit. Different types of withdrawable units (e.g., circuit breaker units, PT units, isolation units) can independently perform their respective electrical functions.
Chassis Rail Design: Features two mainstream structural designs: "middle-mounted" (rails located in the middle of the cabinet) and "floor-mounted" (rails on the ground). Smooth insertion and withdrawal are achieved via a lead-screw crank or an intelligent drive system; some models allow for direct movement on the floor without the need for an additional transfer trolley.
Standardized Mechanical Interfaces: Units of the same specification feature uniform external dimensions and mounting hole locations. They are designed to match the rail and stationary contact layout of the corresponding cabinet type, allowing for installation without further adjustment.
Multi-Position Status Switching
The withdrawable unit features three distinct locked positions within the cabinet, corresponding to different electrical connection states:
Service Position:The unit is fully inserted; both primary and secondary circuits are connected, and the equipment is in normal operating mode.
Test Position: The unit is partially withdrawn; the primary circuit is fully disconnected while the secondary circuit remains connected. This allows for mechanical operation tests (opening/closing) without affecting the energized state of the main circuit.
Maintenance Position: The unit is fully withdrawn from the cabinet; both primary and secondary circuits are disconnected. Shutters covering the stationary contacts close automatically to provide physical isolation, ensuring safety during maintenance operations.