Castell key application - Transformer interlocking utilising trapped key products

05/04/2010 by David Slade.

This arrangement ensures that transformers are isolated and earthed prior to access being gained to the transformer enclosures.

Condition 1
Transformer is locked on with the earth switch locked off and access cabinets locked closed.

Power to the transformer is isolated via an isolator, this releases key ‘A’. Key ‘A’ is taken to the ‘KL’ lock fitted to the transformer ‘ON’ mechanism. The mechanism is switched to the ‘OFF’ position and the key ‘A’ inserted which allows the extension of the ‘KL’ locking bolt and the release of key ‘B’. The transformer is now locked off. Key ‘B’ is taken to the transformer earth mechanism which is moved to the earthed ‘ON’ position and inserted which allows the extension of the ‘KL’ locking bolt and the release of key ‘C’. The earth is now locked on. Key ‘C’ is inserted into the time delay unit ‘D’ and the time delay initiated. The time delay is required to ensure that the capacitors are discharged prior to access. On completion of the delay key ‘D’ becomes available. Key ‘D’ is inserted into the key exchange box ‘X’ to release the access keys ‘E’. Access can now be gained to the enclosures via the access locks ‘D’ and ‘ATE’.

Posted in HV switchgear isolation, Transformer protection, Castell switching, switchgear | 1 Comment »