Section 8(5) in Tamil Nadu Electricity Grid Code, 2005
(5)Scheduling and Despatch procedure:(i)The generation scheduling and despatch data shall be as per format in Annexure D-1. The procedure has been devised taking into account the ABT (Available Based Tariff) regime.(ii)Each day starting from 00.00 hours will be divided into 96 time blocks of 15 minutes intervals.(iii)By 10.00 a.m. every day all the generating stations in the States shall furnish to the SLDC, the station wise ex-power plant MW and MWh capability foreseen for each time block of the next day i.e. from 00.00 hours to 24.00 hours of the following day.(iv)The SSLDC shall inform the SLDC the MW and MWh requirements for different hours for the next day by 11.00 AM. The SLDC shall receive information from RLDC regarding the MW and MWh entitlements from Central Generating stations for different hours and blocks for the next day by 11.00 AM.(v)The above information of the foreseen capabilities of the State generating stations received from SSLDC and entitlements from CGS given by RLDC shall be compiled by the SLDC everyday for the next day, and advised to all SSLDC by 12 AM.(vi)The SSLDCs shall review it vis-a-vis their foreseen load pattern based on the drawal schedule of all the beneficiaries/ distribution licensees and shall advise the SLDC by 1.00 PM, the sub station wise MW and MWh requirements foreseen for different hours for the next day i.e., from 00.00 hours to 2400 hours of following day to the SLDC.(vii)The SLDC shall review the foreseen load pattern and the generation capacity available including bilateral exchanges if any, and advise the RLDC by 3.00 PM. their drawal schedule for the next day for each of the generating stations in which they have shares and the other generating companies in the State, their despatch schedule.(viii)By 5 PM each day, the RLDC shall convey the ex-power plant "despatch schedule" to each of the Inter State Generating Stations, and "net drawal schedule" to each SLDC / beneficiary in MW for different hours, for the next day.(ix)By 6 PM each day, the SLDC shall convey the ex-power plant "despatch schedule" to each of the State generating stations and "net drawal schedule" to each of the State beneficiary / distribution licensee through SSLDC in MW for different hours, for the next day.(x)The summation of the station-wise ex-power plant generation schedules for all generating stations after deducting the apportioned transmission losses (estimated), shall constitute the State beneficiaries / distribution licensees drawal schedule(xi)While finalizing the above daily generation schedules for the generating stations, the SLDC shall ensure that the same 3je operationally reasonable, particularly in terms of ramping-up /ramping-down rates and the ratio between minimum and maximum generation levels. Additional charges payable to the generating companies on account of such plant operations requiring oil support and / or unit shut-down / start-up shall also be considered by SLDC.(xii)The generating companies in the State may inform through SSLDC any modification / changes to be made in station wise drawal, schedule / foreseen capabilities, if any, to SLDC by 9.00 PM.(xiii)Based on the surplus, if any, the SLDC may arrange for bi-lateral exchanges. Such arrangement shall be intimated to RLDC by the SLDC by 10.00 PM.(xiv)The SLDC shall receive the final 'drawal schedule' against Central allocation along with bilateral exchange of power, if any by 11.00 PM.(xv)The SLDC shall inform the final drawal schedule for the next day to SSLDC by 11.15 PM(xvi)The SSLDC shall, in turn, inform the beneficiaries / distribution licensees the drawal schedule for the next day by 11.30 PM and it is freezed.(xvii)In the event of any contingency, SLDC will revise the schedules on the basis of revised declared capability by the generators. The revised schedules will become effective from the 4th time block, counting the time block in which the revision is advised by the generator to be the first one. The revised declared capability will also become effective from the 4th time block.(xviii)In the event of bottleneck in evacuation of power due to any constraint, outage, failure or limitation in the transmission system, associated switchyard and substations owned by STU (as certified by SLDC) necessitating reduction in generation, SLDC will revise the schedules which will become effective from the 4th time block, counting the time block in which the bottleneck in evacuation of power has taken place to be the first one. Also, during the first, second and third time blocks of such an event, the scheduled generation of the station will be deemed to have been revised to be equal, to actual generation and also the scheduled drawals of the beneficiaries / distribution licensees will be deemed to have been revised to be equal to their actual drawals.(xix)In case of any grid disturbance, scheduled generation of all the generating stations and scheduled drawal of all the beneficiaries / distribution licensees shall be deemed to have been revised to be equal to their actual generation/drawal for all the time blocks affected by the Grid Disturbance. Certification of Grid Disturbance and its duration shall be done by SLDC.(xx)Revision of declared capability by generator(s) and requisition by beneficiaries / distribution licensees for the remaining period of the day will also be permitted with advance notice. Revised schedules/declared capability in such cases shall become effective from the 6th time block, counting the time block in which the request for revision has been received in SLDC to be the first one.(xxi)If, at any point of time, SLDC observes that there is need for revision of the schedules in the interest of better system operation, it may do so on its own and in such cases, the revised schedules shall become effective from the 4th time block, counting the time block in which the revised schedule is issued by SLDC to be the first one. To discourage frivolous revisions, SLDC may, at its sole discretion, refuse to accept schedule/capability changes of less than 50 MW(xxii)Generation schedules and drawal schedules issued/revised by SLDC shall become effective from designated time block irrespective of communication success.(xxiii)For any revision of scheduled generation, including post facto deemed revision, there shall be a corresponding revision of scheduled drawals of the beneficiaries.(xxiv)While finalizing the drawal and despatch schedules as above, the SLDC and SSLDCs shall also check that the resulting power flows do not give rise to any transmission constraint. In case any impermissible constraints are foreseen, the SLDC shall moderate the schedules to the required extent, under intimation to the concerned Users. Any changes in the scheduled quantum of power which are too fast or involve unacceptably large steps, may be converted into suitable ramps by the SLDC.(xxv)On completion of the operating day, by 24.00 hours, the schedule finally implemented during the day (taking into account all before-the-fact changes) in despatch schedule of generating stations and drawal schedule of the Users shall be issued by SLDC. This schedule shall be the datum for commercial accounting. The average ex-bus capability for each of the generating stations shall also be worked out based on all before-the-fact advice to SLDC.(xxvi)The SLDC and the SSLDCs shall properly document all the above information i.e. station-wise foreseen ex-power plant capabilities advised by the generating stations, the drawal schedule indented by the beneficiaries / distribution licensees, all schedules issued by the SLDC / SSLDCs, and all revisions / updating of the above.(xxvii)The procedure for scheduling carried out by SLDC/ SSLDCs, shall be open to all entities for any checking / verification. In case any mistake / omission is detected, the SLDC and SSLDCs shall forthwith make a complete check and rectify the same.(xxviii)A procedure for recording the communication regarding changes to schedules duly taking into account the time factor shall be evolved by STU.
