Isolation handcart

TOONICE’s the isolating switchgear truck is a movable device used for electrical isolation in high-voltage switchgear cabinets. Its core function is to reliably isolate the part to be repaired from the live power source during the maintenance of high-voltage equipment, forming a visible safe break point to prevent electric shock accidents and ensure the safety of maintenance personnel. It does not have the capability to make or break load current or short-circuit current, and is only used as a “safety barrier”.

I. Structure and Principle

1. Core Components:

① Current-carrying parts: Include static contacts (connecting busbars) and moving contacts (installed on the truck to connect downstream equipment). Most are made of copper alloy to ensure reliable electrical conductivity.

② Mechanical structure: Consists of a chassis truck (with rollers to support the truck’s movement), a propulsion mechanism (lead screw or rack to control the truck’s entry and exit), and a locking device (fixes the truck’s position to prevent misoperation).

③ Interlocking device: A key safety design that includes functions such as “The truck cannot be closed if not in place” and “The truck cannot be pushed in if the earthing switch is not open”. It enforces safe operation procedures and avoids misoperation.

2. Working Process:

① Normal operation: The isolating switchgear truck is in the “working position”, where moving contacts are in close contact with static contacts, and high-voltage current is conducted to downstream equipment (e.g., circuit breakers, transformers) through the truck.
② Fault Response: During normal operation, the voltage of the open delta is 0; when single-phase grounding occurs, the zero-sequence voltage triggers the protection device to operate via the open delta.

II. Design Advantages and Technical Features

1. High safety priority: No arc-extinguishing device (as it is not used for making and breaking current), while “isolation reliability” is emphatically enhanced. For example, the contact opening distance meets national standards (usually ≥125mm for the 12kV class) to ensure insulation safety.

2. Convenient operation: The truck can be pulled out of the cabinet as a whole. There is no need to dismantle individual components during maintenance. With a special handle, a single person can complete pushing-in / pulling-out operations.

3. Strong compatibility: It has uniform dimensions with circuit breaker trucks and PT trucks, and can be adapted to switchgear cabinets of the same model (such as the KYN28-12 type), facilitating flexible configuration and replacement of equipment inside the cabinet.

III. Key Technical Parameters

1. Voltage class: Common classes are 12kV, 24kV, and 40.5kV, suitable for medium and high-voltage power distribution systems.

2. Insulation level: For the 12kV class, the power frequency withstand voltage is ≥42kV (for 1 minute), and the lightning impulse withstand voltage is ≥75kV (peak value), meeting insulation requirements in high-voltage environments.

3. Mechanical life: The number of pushing-in / pulling-out operations is ≥1000 times, ensuring long-term operational reliability.

IV. Maintenance operation

1. First, open the downstream circuit breaker (to cut off the current);

2. Withdraw the isolating switchgear truck to the “test position” and confirm that the contacts are completely open;

3. (Optional) Close the earthing switch to discharge residual charges;

4. Maintenance personnel enter the site for work. At this point, the equipment to be maintained is completely isolated from the power source.