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