The drawer is a movable support that houses a vacuum interrupter (i.e., the main body of the vacuum circuit breaker) and can be moved flexibly. Its core function is to enable the conversion between the "working", "testing", and "isolating" states of the circuit breaker, ensuring absolute safety and convenience during equipment maintenance and repair. Now, let's break down how it works in detail.
The three core working positions of the drawer
The drawer moves along the guide rail of the switch cabinet and, through mechanical interlock devices, can precisely be positioned in three main positions:
1. Working position
State: The drawer is fully pushed into the cabinet.
Connection: The moving contacts (connected through the up and down arms of the circuit breaker) are in contact with the fixed static contacts (reliably connected on the busbar side and line side of the cabinet).
Function: At this time, the circuit breaker is connected to the main circuit and can normally switch load current or cut off fault current. The circuit breaker can perform remote or local closing and opening operations.
2. Test position
State: The drawer is pulled back from the working position to a certain distance, causing the moving and static contacts to completely separate, but the drawer remains in the cabinet.
Key feature:
Electrical isolation: There is a clear and compliant with safety standards air insulation distance between the moving and static contacts. This means that the circuit breaker has been physically disconnected from the main circuit, ensuring the power outage of the rear-end lines and allowing for safe maintenance.
Secondary circuit remains connected: The secondary connectors on the drawer (used for control, measurement, and protection signals) are still connected to the secondary circuit of the switch cabinet.
Function:
Safety tests: In this position, operations such as opening and closing the circuit breaker can be tested to check if the mechanical actions are normal without powering the main circuit.
Protection debugging: The relay protection device can be debugged and tested. This is a very important safety step before maintenance.
3. Open/Isolated position
State: The drawer is pulled further back from the test position, completely the cabinet. Or, in some designs, the test position and the open position are the same.
Function： At this time, the circuit breaker is completely disconnected from the main circuit and the secondary circuit. The drawer can be maintained, inspected, or replaced.
Key Components and Safety Interlocks for the Working of the Handcart
For the handcart to operate safely and reliably, several key components and precise design are required.
1. Moving Mechanism:
Operating Mechanism:
This is the core component for operation. The operator inserts the dedicated handle into the slot on the handcart panel and rotates it clockwise or counterclockwise. Using the screw transmission principle, the handcart is smoothly driven forward or backward along the guide rail. This design ensures smooth operation and precise control of force.
Note: The handle can only be inserted for operation when the circuit breaker is in the open position. This is a basic safety interlock.
2. Moving Contacts and Contact Arms:
Installed on the handcart and moving with it. Usually, there is an insulating cover to prevent accidental contact.
3. Grounding and Safety Interlocks:
Mechanical Interlock: This is the core for ensuring safety! Ensure the following sequence to prevent incorrect operation:
The circuit breaker can be closed only when the handcart is in the "working" or "test" position.
The handcart can only be rotated when the circuit breaker is in the "open" state.
The grounding switch cannot be closed when the handcart is between the "working" and "test" positions.
The grounding switch can only be closed after the handcart is moved out (to the test or open position), grounding the line. The grounding switch cannot be pushed into the working position when it is closed.
Summary: Advantages of Handcart Operation
The vacuum circuit breaker adopts the handcart design, bringing significant advantages:
High Safety: Through clear physical positions and mechanical interlocks, it completely prevents malicious misoperations such as pulling the handcart while it is under load.
Easy Maintenance: If the circuit breaker requires major repair or replacement, the faulty handcart can be pulled out and the handcart in standby position can be pushed in, minimizing power outage time and improving power supply reliability.
High Flexibility: Facilitates daily testing, debugging, and maintenance.
10kV indoor high-voltage isolation truck
10kV indoor high-voltage isolation truck produced by Shaanxi West Power Tongzhong Electrical Co., Ltd. is a key device for medium-voltage power distribution systems, usually installed in metal-clad removable switchgear of models such as KYN28A-12. Its main function is to isolate and segment the circuit in the power system, ensure safe power-off during equipment inspection and maintenance, and support flexible withdrawal or push-in for easy operation and maintenance. The isolation trolley does not have the arc extinguishing capability of the circuit breaker and needs to be used in conjunction with the circuit breaker.
The main assembly size is consistent with the VS1 circuit breaker trolley, which is convenient for switchgear design, manufacturing, installation and maintenance; the isolation trolley is equipped with a 220V (optionally 110V) AC/DC dual-purpose locking device; the chassis trolley can be configured with S8 and S9 auxiliary switches, and each auxiliary switch can be equipped with up to 6 docking points according to different user needs; the secondary part of the trolley adopts a 58-pin aviation plug socket.
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