Insulated pull rod support for ZN12-40.5KV high-voltage circuit breaker accessories, vacuum interrupter

The pull rods and support rods of the ZN12 series vacuum circuit breakers are the core components of their mechanical transmission system, responsible for transmitting the power of the operating mechanism to the moving contacts of the vacuum interrupters to achieve reliable opening and closing operations.

I. Functions and Roles

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

Insulated pull rod: Usually made of insulating materials such as epoxy resin, its core function is to provide reliable electrical insulation between the charged moving conductive rod and the grounded mechanism box, and at the same time transmit the mechanical force generated by the rotation of the main shaft to the moving conductive rod.

Support part: Mainly refers to the mechanism box welded from angle steel plates and the epoxy resin poured insulators fixed on it. As a mechanical support, the insulator bears the weight and operating stress of all charged components such as the vacuum interrupter and the upper and lower outlet terminals, and ensures its insulation to ground.

II. Structure and Connection Relationship

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

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

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

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

Power transmission path:

Switch main shaft: Driven to rotate by the operating mechanism.

Insulated pull rods: The main shaft converts rotary motion into linear motion through three insulated pull rods, one for each phase.

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

Moving contact action: Finally, the power is transmitted to the moving conductive rod through this bearing, driving the moving contact in the vacuum interrupter to perform linear opening and closing movements.

III. Description of Key Components

Insulated pull rod: As a key component of transmission and insulation, it requires mechanical strength and electrical insulation performance. The adjustment of its length and connection points directly affects the stroke, overtravel and synchronism of the contacts.

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

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

IV. Maintenance and Fault Correlation

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

Transmission faults: Loosening, deformation of the insulated pull rod or falling off of the connecting pin will lead to failure of power transmission, causing the circuit breaker to refuse to operate or malfunction. There was a case where the aging of the rubber sleeve of the adjusting limit screw indirectly caused the opening trip failure.

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

Mechanical wear: Long-term wear of moving pairs such as universal rod end bearings and pin shafts will lead to increased operating force and stroke changes, and may cause jamming in severe cases.

Routine inspection: During maintenance, check whether the insulated pull rod has cracks and bending, whether all connecting parts are firm, and whether the moving parts are well lubricated. Manual slow opening and closing operation is an effective method to check whether the transmission system is flexible and has no jams.

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