Insulating pull rod, support, and vacuum interrupter for ZN12-40.5KV high-voltage circuit breaker

The pull rod and support rod of the ZN12 series vacuum circuit breaker are core components of its mechanical transmission system, responsible for transmitting the power from the operating mechanism to the moving contact of the vacuum interrupter to achieve reliable switching operations.

I. Functions and Roles

The pull rod and support rod together form the transmission chain of the circuit breaker body.

Insulating pull rod: Usually made of insulating materials such as epoxy resin, its core function is to provide reliable electrical insulation between the live moving conductive rod and the grounded mechanism box, while transmitting the mechanical force generated by the spindle rotation to the moving conductive rod.

Support part: Mainly refers to the mechanism box welded by angle steel plates and the epoxy resin cast insulators fixed on it. As mechanical supports, the insulators bear the weight and operating stress of all live parts such as the vacuum interrupter, upper and lower outgoing terminals, and ensure their insulation to ground.

II. Structure and Connection Relationship

Taking a typical structure as an example, the composition and connection sequence of its transmission and support system are as follows:

Support base: The mechanism box is the mechanical base of the entire circuit breaker.

Insulating support: Six epoxy resin insulators are vertically fixed on the mechanism box, providing insulation to ground and mechanical fixation for the three-phase circuit.

Interrupter fixation: The three-phase vacuum interrupters are respectively fixed on the corresponding insulators through cast aluminum upper and lower outgoing terminals.

Power transmission path:

Switch spindle: Driven by the operating mechanism to rotate.

Insulating pull rod: The spindle converts rotational motion into linear motion through three insulating pull rods (one per phase).

Lever and joint bearing: The insulating pull rod pushes the lever on the lower outgoing terminal. The lever is connected to the universal rod end bearing (or joint bearing) installed at the bottom of the moving conductive rod of the vacuum interrupter through a shaft pin.

Moving contact operation: Finally, the power is transmitted to the moving conductive rod through this bearing, driving the moving contact inside the vacuum interrupter to perform linear switching motion.

III. Key Component Description

Insulating pull rod: As a key component for transmission and insulation, it is required to have sufficient mechanical strength and electrical insulation performance. The adjustment of its length and connection points directly affects the contact stroke, overtravel and synchronization.

Universal rod end bearing: Installed at the bottom of the moving conductive rod, it is used to compensate for minor misalignment that may occur during transmission, reduce lateral force, ensure smooth operation, and protect the bellows of the vacuum interrupter from torsion damage.

Flexible connection: Installed between the moving conductive rod and the lower outgoing terminal, it uses flexible conductive materials (such as multi-layer copper foil), which ensures current conduction while allowing the moving conductive rod to perform linear motion.

IV. Maintenance and Fault Correlation

The status of the pull rod and support system directly affects the reliability of the circuit breaker:

Transmission faults: Loosening, deformation or falling off of the connecting pin of the insulating pull rod will lead to failure of power transmission, causing the circuit breaker to refuse operation or misoperation. There have been cases where the aging of the rubber sleeve of the limit screw indirectly caused the failure of the opening tripping.

Insulation degradation: If there are cracks, contamination or moisture on the surface of the insulating pull rod or support insulator, the insulation strength will be reduced, which may cause a ground flashover fault.

Mechanical wear: Long-term wear of moving pairs such as universal rod end bearings and shaft pins will lead to increased operating force and changed stroke, and may even jam in severe cases.

Routine inspection: During maintenance, check whether the insulating pull rod has cracks or bending, whether each connection part is firm, and whether the moving parts are well lubricated. Manual slow opening and closing operations are effective methods to check whether the transmission system is flexible and whether there is any jamming.

In summary, the pull rod and support rod system of the ZN12 circuit breaker is a precision mechanical structure integrating insulation, support and transmission. Its design and installation quality is the basis for ensuring the long-term stable operation of the circuit breaker.