What to choose for a gas-insulated switch - spring-hydraulic or spring-loaded drive?

Good day, Sergey.

The questions “What to choose” and “What is more reliable” direct the questioner to diverging logical paths of choice.

For your SF6 circuit breaker, I advise you to select the drive provided by the manufacturer. After all, the highly reliable drive of another plant may have a different approach to the transfer of force from the drive mechanism to the switch. We will have to modify the design, which promises a series of approvals with the developers of the enterprise. Your corrections can cause unpredictable changes in dynamic characteristics, which will reduce the reliability of the circuit breaker.

If your circuit breaker is adapted by the manufacturer to the version of spring-hydraulic and spring-loaded drives, then the question of choice dictates the presence of a constant operational duty officer. In other words, if the spring works, then to restore the power supply you will need to cock the drive manually. Consumers of the third category of reliability - they can wait, the rest need urgent restoration of electricity supply. If you choose a spring-hydraulic, controlled by automation / telemechanics, then the staff is not needed.

The problem of choice, I note, is mainly solved by the “accounting department” - the solid budget of the enterprise allows to purchase modern foreign reliable equipment, the scarce supply of funds dictates costing the domestic inexpensive.

There is another approach to reliability - the fewer elements and parts of the drive, the more reliable it is.