Alok Roy

UHV/EHV Level HV/MV Level LV Level The Concept of a power grid

Evolution of IndianPower Grid Evolution of Indian Power Grid Phenomenal expansion since Independence  Generation : 1349 MW 101,866 MW (in 1947) (in 2001)  Grid : Local grid – at the time of Independence. State Grids – emerged in 1960s. Regional Grids – in 1970s. Five Regional Grids – Northern, Western, Southern, Eastern & North-eastern National Grid – under progress.

Power Scenario – at a Glance Existing Installed capacity - 101,866 MW Coal – 71%  Hydro – 25 Nuclear & others – 4% Peak demand  Peak power - 78,000 MW  Energy (average) MU/day Availability  Peak power - 68,000 MW  Energy (average) MU/day Shortage  Peak power - 10,000 MW (12.8%)  Energy MU/day (7.7%)

OPERATION OF LARGE INTERCONNECTED SYSTEM W.R.T. INDIAN CONTEXT OPERATION OF LARGE INTERCONNECTED SYSTEM W.R.T. INDIAN CONTEXT Indian Power System is ‘Large’ geographically and very wide-spread in terms of generation and load locations Various electrical regions characteristically different w.r.t. the generation mix, system size, load factors, grid parameters etc.

Evolution from state level entities to the present regional system still has inadequacies in true sense of ‘power system’ Almost ‘Stiff’ power system elements (e.g. most Indian generators) do not rise to occasion at the time of parameter variation or contingency. In absence of higher order control (in terms of hierarchy) such as the AGC and near-absence of parameter based local variations in our control techniques, technical solution can not be ensured presently for steady-state operation. Dynamic and transient modes shall continue to be vulnerable areas.

BIGGER CHALLENGE TO SYSTEM OPERATORS compared to that for operators of perfect or near-perfect power system in developed countries WHAT NEXT? COMMERCIAL MECHANISM IS THE ONLY ANSWER Result ??

REACTIVE POWER CONTROLB.1 REACTIVE POWER CONTROL LOW VOLTAGE Accountability of Load Power factor missing at present Severe inadequacy in compensation at the point of drawal No or low redundancy in transmission and sub- transmission levels Overloading of distribution circuits in part or full Lumping of capacitive compensation, sometimes at higher voltages rather than at distribution levels ‘Mental block’ of generation engineers to generate MVAR upto rated value of machines

Movement of reactive power over long distances - physically and electrically Low voltages, sometimes severe, even on EHV sub-stations, more accentuated when coupled with low grid frequency Fall-out: Low output and in-efficient working of voltage sensitive equipment including certain generating station auxiliaries, high system losses, tripping of healthy transmission lines on distance-relay load encroachment at times, burning of certain equipment due to over- current etc.

Capability Curve of a typical 210 MW BHEL Generator

Capability Curve of a typical 500 MW BHEL Generator

REACTIVE POWER CONTROLB 2. REACTIVE POWER CONTROL (Contd......) HIGH VOLTAGE: Though not encountered as frequently and as severely as Low Voltage cases/spreads in the country, but are caused mainly due to Underloaded system/sub-system elements Non-switched capacitors/banks resulting in lumped surplus MVAR in case of load drop Even bigger ‘Mental Block’ of generation engineers to absorb MVAR upto machine rating, usually ‘stiff’ AVR for cross-over to left. Non-provision of certain switched/non-switched shunt reactors on EHV/UHV lines or bus reactors

High Voltages in the affected pockets, sometimes even at EHV/UHV Levels, more accentuated when coupled with high frequency conditions in the grid. Fall-out:Tripping of overvoltages-sensitive elements including trunk EHV/UHV Lines, dielectric failures/accelerated ageing of equipment, avoidable power loss, common failure of heating elements etc.

Power Scenario – at a Glance All figs. are in MW RegionPeakInstalled Peak DemandCapacity Surplus/Deficit Northern21,00027, ,100 Western25,00030,800- 4,500 Southern20,40024,800- 2,600 Eastern 7,80015, ,000 North-eastern 950 1, Limited exchange of power between Regions --- Main reasons: –Inadequate interconnectors, especially from Eastern Region –Lack of proper Commercial and administrative mechanisms

Demand-Availability Scenario – by Assumptions: Demand – as per 16 th Electric Power Survey Report (EPS). Capacity addition – as per information available from MoP & CEA. Generation availability (average) – 75%. All figs. are in MW Region Demand Installed Availability Deficit/ Capacity Surplus Northern Western Southern Eastern+ North-east

Power Transfer Envisaged from ER and NER by 2012

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NeedforNationalGrid Need for National Grid Uneven disposition of energy resources  Major Hydro resources in NER & NR  Coal reserves mostly in Bihar/Orissa/West Bengal  Cost of power transmission (1.11 cents/kwh) lower than cost of fuel transportation (3.33 cents/kwh). Some Regions are no longer Self-sufficient  Major resources in SR exhausted  In NR, mainly hydro resources having long gestation period Unbalanced Growth of different Regions  Some regions are surplus and some are deficit. Optimisation of generation capacity addition  Utilising time diversity  Spinning reserve optimisation

Development of National Grid – Major Considerations Development in a phased manner – commensurate with generation/ load growth Conservation of Right-of-Way - especially in areas with scarcity of ROW ---- viz. area near hydro, chicken-neck area, forest area, town etc.  In forest area with rich flora & fauna, construction of line with high towers ---- no forest cutting required. Minimisation of transmission cost - immediate as well as long-term basis. Flexible enough to accommodate change in load- generation pattern.

Plan for National Grid PHASE-I (By 2002):  Interconnection through HVDC Back-to-Back links- P North – West: 500MW Vindhyachal Back-to-Back Under P West – South: 1000MW Chandrapur Back-to-Back Opera- P East – South: 500MW Gazuwaka Back-to-Back tion P East – North: 500MW Sasaram Back-to-Back – expected by (AC line of this project in operation transferring 350 MW in radial mode) With the completion of Sasaram HVDC Back-to-back link, framework of National Grid would be completed.

Plan for National Grid PHASE-II (By 2007): High capacity “Transmission highways” envisaged alongwith major generation projects- East-South  2000 MW HVDC bipole between Talcher-Kolar  Augmentation of Gazuwaka HVDC back-to-back by 500MW East – North  High capacity 400 kV link from Tala to Delhi  2500 MW HVDC bipole between Hirma – Jaipur East – West  400kV AC link between Rourkela and Raipur –2003  400kV AC link between Hirma and Raipur & Sipat MAP

Plan for National Grid PHASE-III (By 2012): Establishment of a ring of 765kV lines traversing across Northern, Western and Eastern Regions Construction of various sections of Ring progressively along with major generation projects viz. Barh, Kahalgaon, North Karanpura etc. Strengthening of East-South interconnection through another 2500MW bipole MAP

National Grid: Cost-benefit analysis Cost  Investment required  Rs. 23,000 crores Benefits  Reduction in capacity addition requirement by about MW--- hence saving on investment of Rs. 55,000 crore. (due to peak time diversity and saving in spinning reserve)  Transmission highway would enable setting up of large pit head stations having lower cost of energy  Savings on account of this - Rs crores per annum.  In addition, Nation’s investment towards fuel transportation infrastructure could be avoided.  Better overall hydro-thermal mix  Very low for ER and WR ( ER – 15 : 85, WR - 17 : 83 ) – affecting grid operation  With National Grid, it would become 33 : 67 on all India basis..