High Voltage Circuit BreakerHV AC Switchgear

Switchgear operating mechanism material and important specifications

Special attention has to be paid to the material specification and design of shaft and latch bearings in order to ensure operation without hesitation even after very prolonged periods of inactivity.
The moving contacts should still part within about 25 ms when the protection system issues an opening command. Trip and close latches are designed to be relatively lightly loaded in order to minimize trip and closing coil burdens. To achieve this, they have a high mechanical advantage.However, this brings with it a high velocity ratio with resultant high-impact speeds of the latch faces.

Operating mechanisms important specifications:

  • Trip free:
    The operating mechanism must be able to trip at any part of the closing stroke, and the trip signal will always take precedence over a closing signal.
  • Independent operation:
    Sufficient power must be applied independently of the operator to fully close or open under all conditions
  • Electrical trip :
    For local and remote operation, including protection tripping
  • Manual trip:
    Local operation only
  • Electrical close:
    Usually only for remote operation
  • Manual close:
    Local operation only

Fig shown spring type operating mechanism inside.

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Source
Methods of Operating Mechanisms of High Voltage Circuit Breakers -An Overview articleDistribution Switchgear book By Stan Stewart (IEE)

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