Section 15 in The Orissa Grid Code (OGC) Regulations, 2006
15. Name of the Organisation :
Chapter-6 Scheduling and Despatch Code6.1Introduction.- This Chapter specifies the procedure to be adopted for the scheduling and despatch of Generating Units to meet demand and drawal allocation requirements.If further sets down the procedures to be followed by Users so that the SLDC can meet its daily Drawal Schedule whilst ensuring that reactive power drawals/returns are minimised.This Chapter sets out the -(a)Demarcation of responsibilities between Various Users and SLDC in Scheduling and despatch.(b)Procedure for scheduling and despatch(c)Complementary Commercial Mechanism (Annexure-I to Chapter-6)6.2Objective - This code deals with the procedures to be adopted for scheduling of the State Generating Stations (SGS) including ISGS so far as injection to grid and net Drawals of concerned Users on a daily basis with the modality of the flow of information between the SGS/SLDC/Beneficiaries of the State grid. The procedure for submission of capability declaration by each SGS and submission of Drawal Schedule by each Beneficiary is intended to enable SLDC to prepare the Despatch Schedule for each SGS and Drawal Schedule for each Beneficiary. It also provides methodology of issuing real time despatch/ drawal instructions and rescheduling, if required, to SGS and Beneficiaries along with the commercial arrangement for the deviations from schedules, as well as, mechanism for reactive power pricing. The provisions contained in this chapter are without prejudice to the powers conferred on SLDC under Sections 32 and 33 of the Act.6.3Scope - This Section will be applicable to SLDC, SGS, Distribution Licensees/ STUs and other Beneficiaries in the State grid including CGPs and Open Access Customers.6.4Demarcation of Responsibilities - (1) The Regional grids shall be operated as loose power pools (with decentralized scheduling and despatch), in which the State shall have full operational autonomy, and SLDC shall have the total responsibility as per following guideline for (i) scheduling/despatching State's own generation (including generation of its embedded licensees), (ii) regulating the demand of its customers, (iii) scheduling its drawal from the ISGS (within its share in the respective plant's expected capability), (iv) arranging any bilateral interchanges, and (v) regulating its net drawal from the Regional grid.(2)The system of the State shall be treated and operated as a notional control area. The algebraic summation of scheduled drawal from ISGS/ SGS/CGP and any bilateral interchange shall provide the Drawal Schedule of the State, and this shall be determined in advance on daily basis. While the State would generally be expected to regulate its generation and/or consumers' load so as to maintain its actual drawal from the regional grid close to the above schedule, a tight control is not mandated. The States may, at its discretion, deviate from the Drawal Schedule, as long as such deviations do not cause system parameters to deteriorate beyond permissible limits and/or do not lead to unacceptable line loading.(3)The above flexibility has been proposed in view of the fact that the State does not have all requisite facilities for minute-to-minute on-line regulation of the actual net drawal from the regional grid. Deviations from net Drawal Schedule are however, to be appropriately priced through the Unscheduled Interchange (Ul) mechanism.(4)Provided that the State, through its SLDC, shall always endeavour to restrict is net drawal from the grid to within its Drawal Schedules as specified at Sections 5.3(3)(a)(ii) and 5.3(3) (c) (i) of Chapter-5 of the OGC.(5)The SLDC/STU shall regularly carry out the necessary exercises regarding short-term and long-term demand estimation for the State grid, to enable them to plan in advance as to how they would meet their consumers' load without overdrawing from the grid.(6)The SGS/CGP shall be responsible for power generation injection generally according to the daily schedules advised to them by the SLDC on the basis of the requisitions received from the Distribution Licensees and Beneficiaries and for proper operation and maintenance of their generating stations, such that these stations achieve the best possible long-term availability and economy.(7)While the SGS and CGP would normally be expected to generate power according to the daily schedules advised to them, it would not be mandatory to follow the schedules tightly. The SGS and CGP may also deviate from the given schedules depending on the plant and system conditions. In particular, they would be allowed/encouraged to generate beyond the given schedule under deficit conditions. Deviations from the ex-Power Plant generation/ injection schedules shall, however, be appropriately priced through the Ul mechanism.(8)Provided that when the frequency is higher than 50.5 Hz or falls below 49.5 Hz, the actual net injection and the scheduled despatch for that hour shall be regulated as specified at Section 5.3 (3) of the OGC.(9)However, notwithstanding the above, the SLDC may direct the Distribution Licensees/Trading Licensees/Bulk Consumers/SGS/CGP to increase/decrease their drawal/generation in case of contingencies e.g. overloading of lines/ transformers, abnormal voltages and threat to system security. Such directions shall immediately be acted upon. In case the situation does not call for very urgent action, and SLDC has some time for analysis, it shall be checked whether the situation has arisen due to deviations from schedules, or due to any power flows pursuant to short-term Open Access. These shall be got terminated first in above sequence, before an action, which would affect the scheduled supplies from SGS/CGP to the Long Term Customers is initiated.(10)[For all outages of Generation and Transmission System, which may have an effect on the State grid, all Users shall co-operate with each other and co-ordinate their actions through Power System Operational Co-ordination Committee of the SLDC for outages foreseen sufficiently in advance and through SLDC (in all other cases)as per procedures finalized separately by this Committee. In particular, outages requiring restriction of ISGS/SGS/ CGP generation and/or restriction of ISGS share which a Beneficiary can receive (and which may have a commercial implication) shall be planned carefully to achieve the best optimisation.] [Substituted vide. O.G.E. No. 1953 dated 29.10.2008.](11)All ABT Users should abide by the concept of frequency-linked load despatch and pricing of deviations from schedule, i.e., unscheduled interchanges. All Generating Units and the licensees should normally be operated according to the standing frequency-linked load despatch guidelines issued by the RLDC, to the extent possible, unless otherwise advised by the RLDC/SLDC.(12)It shall be incumbent upon the SGS/ISGS to declare the plant capabilities faithfully, i.e., according to their best assessment. In case, it is suspected that they have deliberately over/under declared the plant capability contemplating to deviate from the schedules given on the basis of their capability declarations (and thus make money either as undue capacity charge or as the charge for deviations from schedule), the SLDC may ask the SGS/ISGS to explain the situation with necessary back-up data.(13)[The STU shall install special energy meters on all inter connections between the Users/Beneficiaries and other identified points for recording of actual net MWh interchanges and MVArh drawals as per relevant CEA Regulation on metering. The type of meters to be installed,metering scheme,metering capability, testing and calibration requirements and the scheme for collection and dissemination of metered data are detailed in Chapter-10. All concerned entities (in whose premises the special energy meters are installed) shall fully co-operate with the STU/SLDC and extend the necessary assistance for taking weekly meter reading by STU and transmitting them to the SLDC.] [Substituted vide O.G.E. No. 1953 dated 29.10.2008.](14)The SLDC shall be responsible for computation of actual net MWh injection of each SGS/CGP/ISGS and actual net drawal of each Beneficiary, 15 minutewise, based on the above meter readings. The data shall be processed by SLDC to prepare monthly energy account, weekly Ul account and reactive energy account. The processed statement shall be forwarded to GRIDCO/ STU to prepare and issue the relevant invoice. All computations carried out by SLDC/GRIDCO/STU shall be open to all Users/Beneficiaries for checking/ verifications for a period of 15 days. In case any mistake/omission is detected, the SLDC shall forthwith make a complete check and rectify the same.(15)SLDC shall periodically review the actual deviation from the despatch and net Drawal Schedules being issued, to check whether any of the Beneficiaries/ ISGS/SGS who are allowed open access are indulging in unfair gaming or collusion. In case any such practice is detected, the matter shall be reported to the SLDC for further investigation/action.6.5Scheduling and Despatch Procedure - (1) Generation Scheduling - All Generators shall provide the fifteen minutes block MW/MVAr availability (00.00 - 24.00 hours) of all Generating Units, to SLDC on the day ahead basis by 10.00 hours. CGPs shall provide the fifteen minutes block import/export figures on the day ahead basis by 10.00 hours. In working out the MW/MVAr availability, Hydro Power Stations shall take into account their respective reservoir levels and any other restrictions and shall report the same to SLDC. SLDC shall obtain from ERLDC, capabilities and fifteen minutes block MW and MWh entitlements from ISGS and fifteen minutes block MW and MWh in the case of Chukha Hydro Power Station, by 10 A.M. on a day ahead basis. The SLDC shall review it vis-a-vis its foreseen load pattern and State's own generating capability including bilateral exchanges, if any, and advise the RLDC by 3 P.M. its Drawal Schedule for each of the ISGS and Chukha Hydro Power Station in which the State has shares, long-term bilateral interchanges, approved short-term bilateral interchanges and composite request for day-ahead open access and scheduling of bilateral interchanges.In preparation of the schedule, SLDC shall take into account of the relative commercial costs to the licensee of the operation of Generation units.SLDC will receive fifteen minutes block "Net Drawal Schedule" in MW from ERLDC by 17-00 hours for the next day (00.00 hours to 24.00 hours) as summation of the stationwise ex-Power Plant Drawal Schedules for all ISGS and Chukha, after deduction of apportioned transmission losses (estimated).SLDC shall intimate the generation schedule/import schedule for the following day to all State's generators/CGPs by 18-00 hours.Generators shall promptly report to SLDC, she can ges of Generating Unit availability or capability,or any unexpected situation, which could affect its operation. All CGPs shall similarly report regarding their export to the State grid. SLDC may inform any modification/changes to be made stationwise Drawal Schedule and bilateral interchanges/foreseen capabilities, if any, to ERLDC by 22-00 hours.SLDC shall advise Users as soon as possible of any necessary rescheduling.SLDC shall receive final Drawal Schedule from ERLDC by 23.00 hours,.SLDC shall prepare the day ahead generation schedule keeping in view the followings:(i)Transmission System constraints from time to time.(ii)Fifteen minutes block load requirements as estimated by SLDC.(iii)The need to provide Operating Margins and reserves required to be maintained.(iv)The availability of generation from State Generators, ISGS and CGPs together with constraints, if any, , in each case.(v)Overall economy to the license and customers.SLDC shall instruct generators to hold capacity reserves (spinning and/or stand by) to the agreed ERLDC guidelines or as determined for Local conditions (with due consideration of wastage of water/fuel as the case may be.SLDC may also require the generators/CGPs to generate MVAR within their respective capability limit, i.e. without sacrificing the active generation, to hold station bus bar voltage at specified levels.(2)Generation Despatch - All generators shall regulate generation and CGPs regulate their export according to the daily generation schedule.All Generating Units, other than those in a CGP, will be subject to central despatch instructions. CGPs will be subject to these instructions as applicable to their respective exports to the licensee.SLDC will despatch by instruction all generation and imports from CGPs according to the fifteen minutes block day ahead generation schedule, unless, rescheduling is required due to unforeseen circumstances.On the day of operation (00.00 to 24.00 hours), in the event of a contingency, SLDC may revise their Drawal Schedule from any/all ISGS and Chukha Hydro Power Station within entitlement. ELRDC will revise and issue Drawal Schedule in consultation with SLDC. All such revisions shall be effective one hour after first advice given to ERLDC.In absence of any despatch instructions by SLDC, State Generators and CGPs shall generate/export according to the day ahead generation schedule.Despatch instructions shall be in standard format. These instructions will recognise declared availability and other parameters, which have been made available by the State Generator to SLDC. These instructions shall include time, Power Station, Generating Units (total export in the case of CGP), name of operators sending and receiving the same.Despatch instructions may include :(i)To switch a generator into or out of service.(ii)Details of reserve to be carried on a unit.(iii)To increase or decrease MVAr generation to assist with voltage profile.(iv)To begin pre-planned Black Start procedures.(v)To hold spinning reserve.(vi)To hold Generating Units on standby.(3)Communication with Generators - Despatch instructions shall be issued by e-mail/telephone, confirmed by exchange of names of operators sending and receiving the same and logging the same at each end. All such oral instructions shall be complied with forthwith and written confirmation shall be issued promptly by Fax, Teleprinter or otherwise.6.6Action Required By Generators - All generators and CGPs shall comply promptly with a despatch instruction issued by SLDC unless this action would compromise the safety of plant or personnel.The Generators and CGPs are required to abide by Sections 5.3 and 5.2 regarding operation of governors and AVRs respectively.The generator and CGPs shall promptly inform SLDC in the event of any foreseen difficulties in carrying out an instruction.Generators shall immediately inform SLDC by telephone of any loss or change (temporary or otherwise) to the operational capability of any Generating Unit which is synchronised to the system or which is being used to maintain system reserve. Generators shall inform SLDC any removal of AVR and/or governor from service with reasons.CGPs shall similarly inform any change instatus affecting their ability in complying with despatch instructions.Generators shall not de-synchronise Generating Units, other than in respect of CGPs. without instruction from SLDC except on the grounds of safety to plant or personnel, which shall be promptly reported to SLDC.Generators and CGPs shall report any abnormal voltage and frequency related operation of Generating Units/feeders promptly to SLDC.Generators shall not synchronose Generating Units, other than in respect of CGPs, without instruction from SLDC. In emergency situations, the generator may synchronise Units with the grid without prior intimation in the interest of the operation of the grid following standing institutions developed for such purpose under "Contingency Planning".Should a generator fail to comply with any of the above provisions, it shall inform SLDC promptly of this failure.6.7Enhancement of Schedule and Despatch Procedure - Schedule and despatch procedures shall be suitably enhanced to cater to tariff agreements as soon as any such agreement is reached with generators, IPPs, and CGPs.6.8Data Requirements - Users shall provide SLDC with data for this Section as specified in the Data Registration Chapter.Annexure-1 to Chapter-6{Refer Clause 6.1 (c)}Complementary Commercial Mechanisms
