Section 7(3)(xiii) in Tamil Nadu Electricity Grid Code, 2005
(xiii)All State entities shall provide automatic under-frequency load shedding, based on the operation of df/dt or constant frequency setting relay in their respective systems, to arrest frequency decline that could result in a collapse / disintegration of the Grid, as per the plan separately finalised by SLDC in consultation with STU, and shall ensure its effective application to prevent cascaded tripping of generating units in case of any contingency. All entities shall ensure that the under-frequency load shedding / islanding schemes are functional and no under-frequency relay is bv-passed or removed without prior consent of SLDC.