MV AC Switchgear

Typical mechanical interlocks in MV metal clad switchgear according to IEEE standard

  • To prevent moving the removable element to or from the connected position when the switching device is in the closed position.
  • To prevent closing the switching device unless the primary disconnecting devices are in full contact or are separated by a safe distance.
  • Means shall be provided for positively holding the removable element in place in the housing when it is in either the connected position or the test position.
  • To prevent the disconnection of access to fuses on the primary side of control power transformers unless the secondary circuit is open
  • CBs shall be designed to prevent the release of the stored energy unless the mechanism has been fully charged.
  •  Operators shall be protected from the effects of accidental discharge:
    1. Interlocks provided in the housing to prevent the complete withdrawal of the CB from the housing when mechanism is charged
    2. A suitable device provided to prevent the complete withdrawal of the CB until the closing function is blocked
    3. A mechanism provided to automatically discharge the stored energy before or during the process of CB withdrawing
  • Means shall be provided to prevent moving CBs into the connected position
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