Section 5(7) in Tamil Nadu Electricity Grid Code, 2005
(7)Transmission System Planning: (a) The planning criterion are based on the security philosophy on which the STS has been planned. The security philosophy may be as per the Transmission Planning Criteria and other guidelines as given by CEA. The general criteria shall be as detailed below:(i)As a general rule, the STS shall be capable of withstanding and be secured against the following contingency outages without necessitating load shedding or rescheduling of generation during Steady State Operation:- Outage of a 110 kV D/C line or,- Outage of a 230 kV D/Cline or,- Outage of a 400 kV S/C line or,- Outage of single Interconnecting Transformer.(ii)The above contingencies shall be considered assuming a pre contingency system depletion (Planned outage) of another 230 k V D/C line or 400 kV S/C line in another corridor and rot emanating from the same substation. All the Generating Units may operate within their reactive capability curves and the network voltage profile shall also be maintained within voltage limits specified.(b)The STS shall be capable of withstanding the loss of most severe single system infeed without loss of stability.(c)Any one of these events defined above shall not cause:(i)Loss of supply.(ii)Prolonged operation of the system frequency below and above specified limits.(iii)Unacceptable high or low voltage.(iv)System instability.(v)Unacceptable overloading of STS elements.
