How do you adjust the opening speed of a power OCB?

The correct choice regarding the adjustment of the opening speed of a power oil circuit breaker (OCB) is to adjust the tail spring. The tail spring is a critical component in the operating mechanism of an OCB. It influences how quickly the moving contacts of the circuit breaker can separate when the breaker opens. By adjusting the tension of the tail spring, you can control the speed at which the contacts part, thereby affecting the opening speed of the breaker.

This option addresses the mechanical aspects of the circuit breaker’s operation, which is crucial for ensuring that the breaker functions effectively during fault conditions. The ability to fine-tune the opening speed is essential in protecting equipment and maintaining system stability.

Other methods such as changing voltage or size of the circuit do not directly affect the mechanical operation of the circuit breaker in terms of opening speed. Modifying the operating mechanism, while potentially relevant, is a broader and more complex approach than simply adjusting the tail spring, making it less practical for specific control of opening speed.