The Load Break Disconnect Switch: Purpose and Operation
A Load Break Disconnect Switch (LBDS) is a critical component in medium-voltage electrical distribution systems. It has a clear and vital function：to safely cut off and establish load current under normal operating conditions. This feature makes it different from a simple isolator. An isolator is only meant to open a circuit after another device has de-energized it，and it provides a visible air gap for safety.
Key Function: Making and Breaking Load Current
The main purpose of an LBDS is to perform switching operations on energized circuits. It handles tasks like these：
- Isolating a section of a feeder for maintenance work.
- Transferring load from one source to another.
- Switching off transformers or capacitor banks when they are under load.
To do these tasks safely，the switch is equipped with specialized arc-interruption technology. But we need to note that，unlike circuit breakers which can cut off high-magnitude short-circuit faults，an LBDS is only designed for rated load currents and minor overloads.
Arc Interruption Mechanism
The switch’s ability to break load current comes from its engineered arc control. A common and effective design uses arcing horns or contacts with spring-assisted，quick-make/quick-break mechanisms. When the operator opens the switch，the main contacts separate first. This action transfers the current to the arcing contacts. As these arcing contacts separate，an electric arc is formed.
The switch is designed to stretch and cool this arc quickly. For air-insulated switches，electromagnetic forces and thermal buoyancy drive the arc upwards. Often，the arc is pushed into arc chutes made of deionizing plates. These plates split the arc into smaller segments，cool it down，and make sure it is extinguished when the current crosses zero for the first time. In other designs，a puff of air or gas may be used to help put out the arc.
Safety and Interlocking
Safety is the top priority here. Load break switches are usually operated manually with an insulated pole from ground level. They are often integrated with strong mechanical interlocks. These interlocks prevent the switch from operating when the associated circuit breaker is closed. This ensures the switch never opens under a fault condition that it is not rated to handle.
The abimat Load Break Disconnect Switch is a purpose-built device. It offers both the safety of visible isolation and the operational flexibility of on-load switching. Its specialized arc-interruption capability makes it an indispensable device. It helps manage and isolate sections of a live electrical network safely and efficiently.
