Why we use VCB circuit breaker in high Transimission system not ACB?

In high transmission systems, Vacuum Circuit Breakers (VCBs) are often preferred over Air Circuit Breakers (ACBs) for several reasons:

1. High Voltage Performance: VCBs are generally more suitable for high-voltage applications. They are designed to handle higher voltage levels, making them suitable for transmission systems where voltages are typically in the range of several kilovolts to hundreds of kilovolts.

2. Interrupting Capacity: VCBs typically have higher interrupting capacities compared to ACBs. Interrupting capacity is the ability of a circuit breaker to safely interrupt the current under fault conditions. In high transmission systems, the fault currents can be substantial, and VCBs are designed to handle these high levels of fault currents.

3. Reliability: VCBs are known for their reliability and require minimal maintenance. They use vacuum as the arc quenching medium, which eliminates the need for frequent maintenance associated with arc-chutes in ACBs. This makes VCBs a more attractive option for applications where reliability is critical.

4. Compact Design: VCBs are often more compact and lighter than equivalent-rated ACBs. This can be an important factor in high transmission systems where space may be limited, and weight considerations are significant.

5. Environmental Considerations: VCBs are considered more environmentally friendly than some alternatives. They don't use environmentally harmful substances like oil in their operation, making them a cleaner and more sustainable option.

6. Fast Operation: VCBs have a faster operating time compared to many ACBs. This quick response time is crucial in high transmission systems to swiftly isolate faulty sections and minimize damage.

7. Longer Electrical Life: VCBs generally have a longer electrical life compared to ACBs, making them suitable for applications where longevity is essential.

While VCBs have these advantages in high transmission systems, the choice of circuit breaker depends on various factors, including the specific requirements of the application, cost considerations, and local regulations. In some cases, ACBs may still be used, especially in medium-voltage applications or where other factors make them more suitable for the particular installation.