All internal metal parts of the transformer, with the exception of individual laminations and their individual clamping plates shall be earthed.The top clamping structure shall be connected to the tank by a copper strap. The bottom clamping structure shall be earthed by one or more the following methods:
a)       By connection through vertical tie-rods to the top structure.
b)      By direct metal to metal contact with the tank base.
c)       By a connection to the structure on the same side of the core as the main earth connection to the tank.
The magnetic circuit shall be connected to the clamping structure at one point only and this shall be brought out of the top cover of the transformer tank through a suitably rated insulator. A disconnecting link shall be provided on transformer tank to facilitate disconnections from ground for IR measurement purpose. Coil clamping rings of metal at earth potential shall be connected to the adjacent core clamping structure on the same side as the main earth connections.
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