In the TN-C Network, it is prohibited to cut earth cable, as the Earth Cable is linked with the neutral of the System.
When ID-RCCB is connected on the TN-C Network, the protection conductor of the RCCB will not differentiate the PE conductor and Neutral conductor, as the PE Conductor and the Neutral are connected together in the TN-C Network. The RCCB will not be able to detect the potential variations that would arise due to operating current and insulation defect currents in this scenario and will fail to provide any protection. In fact it might cause nusciance tripping also.