TT earthing system

A TT earthing system earths the power source directly. The consumer installation uses its own local earth electrode, separate from the utility earth. So the operating earth on the generator side and the earth on the load side are separate connections to ground. TT is common in home installations in many European countries. Some Solis models do not support IT grids or advise against TN-C, but every model listed supports TT. SMA backup configurations accept either a TN or a TT utility grid.

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• sentence 4: support check: partial - The Solis table shows TT supported for every model, some with IT unsupported and some with TN-C not recommended. For SMA, u21 only shows 'TN or TT system' for the utility grid in a table row, and the passage doesn't say it is a backup configuration.
• sentence 4: review: partial - The Solis table backs the IT/TN-C/TT statements, but the SMA row only lists 'TN or TT system' for the utility grid and the passage text never says this is a backup configuration. -->