Transmission System Planning under Uncertainty in Indian Context

Transcription

1 Transmission System Planning under Uncertainty in Indian Context R.N. Nayak, Y.K. Sehgal and Subir Sen Abstract Indian power sector is passing through an evolutionary phase and radical changes are taking place continuously in the structural, institutional and operational arrangements. Electricity demand is expected to increase to over 450GW by 2022 & beyond for which total installed capacity of about 600GW is envisaged. The Electricity Act, 2003 has created new paradigm for the development of power sector and enabled setting up of IPPs along with open access. In this direction, large capacity addition has been envisaged through IPPs at various complexes in the State of Orissa, Jharkhand, Chhattisgarh etc. without firm beneficiaries/schedule. Such uncertainties along with right of way (RoW) pose challenges to the transmission planner for development of transmission system. Methodology for development of transmission system factoring into above uncertainties as well as cost recovery mechanism to ensure smooth transmission of power are discussed in this paper. A case study with specific reference to the development of high intensity transmission corridors for various IPPs in Jharkhand, Orissa in Eastern Region and Chhattisgarh, M.P in Western region is also presented. Index Terms Beneficiary, Investment, Transmission, Uncertainty P I. INTRODUCTION ower system in India is growing at an accelerated pace. Electricity demand is expected to be increased to more than 150,000MW in next 4-5 years for which over 78,570 MW generation capacity additions has been envisaged during 11th Plan. Additionally, about 14,000 MW has been envisaged to be added through harnessing grid interactive renewable energy resources which includes about 10,000 MW through wind energy. Currently, the sector is passing through an evolutionary phase and numerous radical changes are taking place in the structural, institutional and operational arrangements. Both Govt//Public and private sectors are participating in large scale in all facets of electricity supply chain i.e., generation, transmission and distribution. This has resulted into paradigm shift in the way with which the power sector is being viewed. Further, the consumer today is looking for Secure, reliable and quality power at affordable price. The Electricity Act, 2003 has created new paradigm for the development of power sector in our country. R.N. Nayak, Y.K. Sehgal and Subir Sen are with Power Grid Corporation of India Ltd., Plot-2, Sector-29, Gurgaon , Haryana ( subir@powergridindia.com). It has created a new competitive framework for the development of the Power Sector with focus on the consumer and safeguarding his interest through Independent Regulatory Commissions. The Act enables delicensing of generation, transmission as license activity, trading as distinct activity, non discriminatory Open Access in transmission, no more fixed formulae (erstwhile Gadgil formula) for allocation of power to the regional constituents rather they are to be determined based on Competitively bid generation tariff, consumers can procure power from different sources through competitive bidding process etc. As a result of above provisions in the Electricity Act 2003, large capacity addition of the order of 180,000MW has been envisaged under Govt. and private sector in next 4-5 years without identifying destination points i.e, beneficiaries of most of the generation projects. Mostly projects are proposed to be located at pocketed pit-head/resource areas with each location having capacity in the range of MW. This necessitates transfer of bulk power to the far-off load centers through long distance transmission system. Various factors like identification of system strengthening in the absence of firm beneficiaries, conservation of eco-sensitive Right-of- Way(ROW), protection of flora & fauna, flexibility to enhance corridor capacity, recovery of investment etc. are posing major challenges towards planning and development of suitable transmission system. In this paper, major considerations for transmission system planning under uncertainties for transfer of power from various generation projects to target destinations/direction are presented. Various issues that need to be addressed towards development high capacity transmission system, comprising 800kV, 6000MW HVDC and 400kV/765kV AC with provision to upgrade to 1200kV at a later date, taking into account other factors are also highlighted. A case study in this regard is also presented along with status of 1200kV AC technology in Indian context. II.OVERVIEW OF INDIAN POWER SYSTEM Indian Power System is demarcated into five electrical regions viz, Northern, Eastern, Western, Southern and Northeastern Regions. Various regions of Indian Power system as shown at Fig.1 below: 384

2 NORTHERN REGION EASTERN REGION NORTH EASTERN REGION As per Integrated Energy Policy: Report of the expert committee by Planning Commission, it is estimated that by 2022, demand would be about 450 GW for which total installed capacity of about 600 GW is envisaged. Growth pattern of demand-capacity requirement by 2022 is given at Fig. 3. WESTERN REGION 700 SOUTHERN REGION Installed Capacity Dem and(peak) Inter Regional Capacity GW Fig. 1: Regional boundary of Indian Power System Present Installed capacity of Indian Power System is about 143,000MW and the peak power demand is about 107,000MW. The trunk transmission system in all the regions is dominated by 400kV level networks. The grid comprises about 1700 ckt. kms 765kV lines, 76,000 ckt. km of 400kV and 115,000 ckt. km of 220kV lines. In addition, three(3) HVDC bipoles(1500/2500mw), seven(7) HVDC back-toback (500/1000MW) links are under operation. Today, as a part of National Grid, central grid comprises of Northern, Western, Eastern & North-eastern regions are operated as a single grid of more than 100,000MW and Southern grid of about 40,000MW capacity is interconnected through a number of HVDC systems. However, to cater the imbalance between demand and supply in the region, National Grid of 17,000MW capacity through inter-regional links were established for exchange of power between regions. A view of the present inter-regional transmission capacity of National Grid is shown at Fig Year Fig. 3: Growth pattern of demand-capacity requirement In order to enhance the capacity of inter-regional links to enable transfer of power across regions, National Grid capacity is being enhanced to more than 40,000 MW by 2012 which shall be enhanced progressively to about 150,000 MW by 2022 & beyond. A view of National Grid by 2012 is shown at Fig-4 KANKROLI ZERDA RAPP KOTA AGRA UJJAIN NAGDA WR SOLAPUR NR GWALIOR AURAIYA GORAKHPUR FATEHPUR BALIA MALANPUR VINDHYACHAL SIPAT CHANDRAPUR KORBA SIPAT RAIPUR M'SARAI SAHU PURI TALCHER 1000 BALIMELA MW MUZAFFARPUR PATNA B'SHARIFF BIRPARA BARH MALDA SILIGURI SASARAM ER DEHRI BUDHIPADAR NORTH KARANPURA RANCHI ROURKELA NER BONGAIGAON SALAKATI KOLHAPUR KOTA NR AGRA GWALIOR UJJAIN AURAIYA MALANPUR VINDHYACHAL GORAKHPUR BALIA KORBA SAHU PURI MUZAFFARPUR PATNA B'SHARIFF BIRPARA MALDA SASARAM ER DEHRI BUDHIPADAR NER BONGAIGAON SALAKATI LAKSHADWEEP PONDA 1000 MW BELGAUM NAGJHARI U.SILERU SR RAICHUR KOLAR GAZUWAKA HVDC BIPOLE HVDC BACK-TO-BACK 765 kv 400 kv Legend ANDAMAN & NICOBAR WR CHANDRAPUR 1000 MW RAIPUR BALIMELA TALCHER ROURKELA 220 kv KOLHAPUR U.SILERU Fig. 4: Schematic of National Grid by 2012 GAZUWAKA LAKSHADWEEP PONDA BELGAUM SR NAGJHARI KOLAR Fig. 2: Present National Grid HVDC BIPOLE HVDC BACK-TO-BACK 765 kv 400 kv 220 kv Legend ANDAMAN & NICOBAR III. CONCERNS IN TRANSMISSION SYSTEM DEVELOPMENT Pocketed generation resources and wide spread load centers across the country coupled with right-of-way problems necessitates development of high capacity transmission corridors. However, major concerns towards development of such corridors are : Long-term transmission planning keeping a horizon of

3 years and beyond Right-of-Way(ROW) and protection of flora and fauna Rehabilitation & Resettlement (R&R) aspects Flexibility to enhance the transfer capacity in view of uncertainty of generation projects, implementation in different phases Optimisation of transmission cost and losses Non-discriminatory Open Access To fulfill above requirements, need of the hour is to introduce emerging technologies into the transmission system. In this direction, many new technologies like 765kV AC, 800kV, 6000MW HVDC, FACTS devices, multi-conductor bundle line, High Surge Impedance Loading line, 1200kV AC etc. have already implemented/undertaken. IV. UNCERTAINTIES IN TRANSMISSION SYSTEM PLANNING In the current electricity supply regime, various uncertainties are associated with the transmission system development process. Some of the key uncertainties pushing a paradigm shift in transmission system planning are : Uncertainties in development of generation project No firm beneficiaries at the development stage of generation project due to introduction of competitively bid generation tariff Recovery of investment towards transmission development A. Uncertainties in development of generation project A large number of generation projects are proposed to be developed mainly in Orissa, Jharkhand, Chhattisgarh, M.P by private developers in addition to capacity addition envisaged by Govt. of India in 11 th Plan. Some of the developers have applied for long-term open access for transfer of power from projects. Past experience reveals that most of the time there is a big gap in planned and actual generation addition, which hampered the optimal utilization of overall planned transmission system. On the contrary, to address the RoW issue, it is necessary to develop high capacity transmission corridors (high power intensity corridor) from resource areas (generation complexes) to the load centers keeping in view long-term perspective. Proposed approach: It is important that most of the projects in the particular generation complex get materialized as per the schedule to ensure optimal utilization of transmission infrastructure. For this, an integrated resource planning approach is required. Further, as the generation projects are developed in phases, flexibility in upgradation of transmission corridor matching with phase-wise development of projects through integration of new technologies may be adopted to take care of uncertainty and optimize investment. B. Uncertainties in identification of beneficiaries Earlier the projects were planned as a regional generation projects(inter-state Generation System), in which all the constituents of a particular region were the beneficiaries or at least beneficiaries were known upfront. Accordingly the transmission system was planned based on the requirement of power transfer to the known destinations. However, to promote competition in the electricity supply industry, Govt. of India has issued guidelines for determination of Tariff by Bidding Process for Procurement of Power by Distribution Licensees. Due to introduction of such tariff based competitive bidding under Case-I/Case-II guidelines, generation developers don t have conformity from the beneficiary till they win the bid from distribution licensees. Therefore, in this scenario, generation developers are not able to commit upfront about the beneficiaries along with their allocation for the purpose of planning optimal transmission system. Further, development of number of Merchant Power Plant(MPP) have been envisaged and in such cases also by its nature there is no firm beneficiaries. In such scenario, it is becoming difficult to plan the transmission system in absence of information about the beneficiaries and quantum of drawl by each of them. Proposed approach: National Electricity Plan envisaged future demand supply scenario of various regions and Electric Power Survey report provides demand projection of different States. Further, based on the capacity addition programme in the State, future surplus-deficit situation may be estimated. Accordingly, developers may inform the target beneficiary(ies)/regions for power transfer from the respective projects. while evolving transmission system fitting into overall transmission plan. C. Recovery of investment for Transmission system Uncertainties in generation project schedule and firm beneficiaries, projects development in a few complexes, development of high intensity transmission corridors to take care of right-of-way issue etc, has resulted into complexity in recovery of investment in transmission corridors. In case only few generation projects materializes, the cost of transmission for the corridor would be high. On the other hand, generation developers are also not sure about the firm beneficiary and therefore, may be reluctant to share of transmission charges for a particular transmission corridor. This has made the overall transmission system planning process and development further difficult. Proposed approach: In order to rationalize the transmission charges of various corridors to take care of uncertainties and recovery of investment, it is proposed that transmission system of various private generation projects/mpp may be planned and segregated into two parts: Part-A: Portion of transmission system between generation project and grid interconnection point/power pooling station (Inter-state Transmission System) as dedicated transmission system of specific project. Further, being dedicated element, same may be built, owned, operated and maintained by the respective developer and cost to be borne by the particular generation developer. 386

4 TABLE-1 POWER INTENSITY (MW/M) AT DIFFERENT VOLTAGE LEVEL Part-B: Portion of transmission corridor beyond the grid interconnection point/pooling station may be developed as a common purpose transmission system to be utilized by other projects also and same to be treated as a part of regional system strengthening. Transmission charges are to be pooled with the Regional Transmission system. However, sharing of this part under regional pool needs to be agreed by the regional beneficiary. However, to ensure timely development of common purpose transmission corridor(s) in an environmental friendly manner, it is proposed that respective generation developers may share the transmission charge to provide comfort for the investment to the transmission developers. The generation developers in turn may make back-to-back arrangement with the procurers/beneficiaries for transmission charges recovery. V. CASE STUDY As discussed above, Government of India (GoI) has envisaged, capacity addition of about 78,570 MW in 11 th Plan (Central sector-39,860mw; State sector-27,950mw, Private- 10,760MW). In addition, many Independent Power Producers (IPP) have proposed to set up generation projects mainly in Orissa(16,500MW), Jharkhand(7,500MW), West Bengal(2,500MW), Chhattisgarh (42,000MW as per MOU signed with GoC), Madhya Pradesh(6000MW) etc. with capacity more than 75,000 MW. In most of the cases, firm beneficiaries of the IPPs are not known and only target beneficiaries or destination of power transfer requirement. This has cropped up plethora of uncertainties and challenges to the transmission planning and development process. Absence of information about beneficiaries from such large quantum projects of Private /Merchant developer as well as firm schedule of generation projects would need to make some assumption regarding destination of power transfer to plan the high capacity transmission system. As per National Electricity Plan/17 th Electric Power Survey report, scenario emerged that power would primarily need to be transferred to deficit regions like Northern/Western region. However considering the severe Right-of-way constraints in the States like Chhattisgarh which has about 50% dense forest/reserve areas and of the similar order in the States of Jharkhand and Orissa as well as quantum of power transfer requirement from the generation complexes in these states, it is required to develop high intensity transmission corridors with higher voltage level. A comparison of power intensity of transmission corridor at different voltage level is shown at Table-1: 220kV 400kV 765kV 500kV HVDC 800kV HVDC (approx.) 1200 kv (approx.) ROW (m) Capacity (MW) MW/m It is seen that power intensity of 765kV transmission corridor is about 9 times more than 220kV and 3 times higher than 400kV level. Further, intensity of 800kV HVDC/1200kV corridor is about 6 times higher than 400kV and almost double than 765kV corridors. A comparison for requirement of number of transmission corridors at different voltage level for transfer of about say 8,000MW power satisfying n-1 redundancy criteria is presented in Table-2 below: Voltage Level TABLE-2 TRANSMISSION CORRIDOR REQUIREMENT No. of Tr. corridors required Right-of-way requirement (m) 400 kv AC kv AC kv AC kV, 6000MW DC It is observed that for transfer of about 8,000MW even at 765kV level, there is a requirement of at least 4 nos. of transmission corridors which requires about 256 meter Rightof-way. Keeping this in view, it is the need of the hour to adopt even higher voltage level such as 800kV, 6000MW HVDC system, 1200 kv AC etc. (initially may be operated at lower voltage level when power transfer requirement is less) so as to utilize Right-of-way in an optimal manner. As per the information, complex wise proposed capacity addition in the above states by 2012 is shown in Table-3. TABLE-3 COMPLEX WISE CAPACITY ADDITION PROGRAMME State/Complex Capacity (MW) Orissa 16,500 Jharkhand 7,500 West Bengal 2,500 Madhya Pradesh 6,000 Chhattisgarh i) Raigarh 5,000 ii) Janjgir Champa 4,000 iii) Korba/Bilaspur 4,000 Power from the above generation complexes is envisaged to be transferred to different target beneficiaries in Western/Northern Region. Keeping this in view a composite but flexible transmission system was evolved based on the load flow studies. In the studies, entire transmission network of Eastern, North-eastern, Western, Northern and Southern Region grids corresponding to 11 th /early 12 th plan time frame was simulated and complex wise corridors are discussed: 387

5 A. Orissa/Jharkhand Complex From the studies it was observed that there is a need to develop large capacity corridors from the generation complexes to various load centres in WR/NR. For this, kv, 6000 MW HVDC bipole between generation complex of Orissa and load centres in NR (Barnala) as well as development of high capacity AC system directly from Eastern region to Northern region for transfer of power from generation projects in upper part of Jharkhand was evolved. Further, for transfer of power from lower part of Jharkhand and Orissa to NR/WR, 3 nos. 765/400kV pooling stations in Orissa at Jharsuguda, Dhenkanal and Angul for pooling of power from different generating stations in Orissa along with interconnection of these pooling stations through 765kV ring network was considered. A schematic of the above pooling stations is shown at Fig. 5. Fig. 5: Schematic of Pooling stations in Orissa For onward transfer of power to WR/NR, power from above three(3) pooling stations was proposed to be injected at new pooling station near Dhramjaygarh (Janjgir-Champa) in Chhattisgarh through 765kV lines (4xS/c or 2XD/c) between Dharamjaygarh and Jharsaguda(Orissa). Beyond Jharsuguda, high capacity transmission corridor via Pooling Station near Dharamjaygarh/Jabalpur(M.P), Bina in WR, Sawai Madhopur, Sikar, Moga & Jallandher in NR integrated with generation projects near Champa-Janjgir and Jabalpur(M.P) complex was considered. B. Raigarh Complex In order to facilitate transfer of power from generation projects in Raigarh complex, development of a 400kV Pooling station near Raigarh is proposed. For onward transfer of power, this Pooling Station may be connected with Raipur, a well connected grid dispersal point in Chhattisgarh. Considering serious ROW constraint beyond Raigarh/Raipur and quantum of power transfer, it was proposed to interconnect Raigarh and Raipur through high capacity lines (400kV quad) with a provision to upgrade to 1200kV level at a later date. In addition, keeping in view of serious ROW constraint and quantum of power transfer beyond Raipur, it was proposed to develop a parallel high capacity corridor through Raipur-Wardha-Aurangabad-Pune with provision to upgrade to 1200kV level. C. Korba/Bilaspur Complex For transfer of power from generation projects near Korba/Bilaspur complex a 400/765kV pooling station near Sipat was planned. This pooling station proposed to be connected with Ranchi in ER through 765kV lines for import of power from ER also. For transfer of power to load centers of WR beyond Pooling station, following high capacity corridors were considered: a)towards western side over high capacity Seoni Wardha Akola - Aurangabad transmission corridor, b)towards central/upper western part of WR, through Seoni Khandwa Rajgarh - Karamsad transmission corridor c)towards northern part of WR as well as further to NR through high capacity Seoni Bina Gwalior Agra transmission corridor. D. Janjgir-Champa Complex For transfer of power from Champa-Janjgir complex near Dharamjaygarh in Chhattisgarh, it was proposed to develop a 765/400kV Pooling Station near Dharamjaygarh to interconnect the projects. For onward dispersal of power and keeping in view the quantum of power transfer, Dharamjaygarh is proposed to be interconnected with Pooling station near Jabalpur through high capacity lines with a provision to upgrade at 1200kV level. Beyond Jabalpur, high capacity transmission corridor one towards NR via Bina and other towards western part of WR were considered. a) Towards NR through Bina Sawai Madjopur Agra Sikar Moga Jallandher corridor b) Towards WR through Bina Indore Baroda corridor A schematic of the different transmission corridors in WR is shown at Fig. 6. MUNDRA RANCHODPURA JETPUR BACHCHAU LIMBDI TO KANKROLI RAJKOT AMRELI ZERDA NARDIPUR DEHGAM WANAKBORI KARAMSAD PIRANA GANDHAR(GEB) BHARUCH KAWAS NAVSARI NAVSARI MAGARWADA VAPI TARAPUR NAVI MUMBAI KALWA VSC TO KALWA RPL NAGOTHANE DHABOL FINOLEX Extn KOYNA KOLHAPUR RAJGARH ASOJ SARDAR SAROVAR BARODA GANDHAR KAKRAPAR VALTHAN KHARADPADA KHADOLI MAPUSA UKAI BOISAR MUMBAI PADGHE PUNE KARAD PUNE LONIKHAND NAGDA JHABUA DHULE KOLHAPUR BtB AURANGABAD BABLESHWAR SHOLAPUR SAWAI MADHOPUR SOUTH SOLAPUR SHUJALPUR INDORE(PG) INDORE BHUSAWAL NARENDRA RAICHUR Fig.6: Schematic of transmission corridors in WR PARLI NARMADA SAGAR KHANDWA AKOLA SATPURA NEW PARLI BHOPAL MAUDA TO AGRA BINA ITARSI GWALIOR BINA(PG) WARDHA CHANDRAPUR STPS DAMOH KORADI SATNA MAHAN JABALPUR POOL BIRSINGHPUR JABALPUR POOLING SEONI STN BHADRAVATI TO RAMAGUNDAM BHATAPARA BHILAI LEGENDS SASAN VINDHYACHAL DHEERU MARUTI KORBA ARYAN+ KORBA(STPS) SPECTRUM RAIGARH POOL SIPAT RAIGARH PATHADI TO BUDHIPADAR RAIPUR ROURKELA RAIPUR POOL SINGRAULI DHARAMJAYGARH 1200 kv 765 kv 400 kv RANCHI JHARSAGUDA 388

6 Since all the generation projects generally does not materializing in the same time frame, therefore, the transmission system developed for composite requirement of the entire potential in the vicinity becomes too large for the initial project. In such scenario it is prudent to adopt a technological option which has flexibility to enhance transfer capacity of corridors. Keeping this in view, it was envisaged that initially 1200kV corridors may be charged at 400 kv level and as the power transfer requirement over the transmission corridor increases progressively, the corridor may be operated at 1200 KV level facilitating deferment/staggering of initial investment. This would also ensure optimal development of the transmission system to meet the future as well as long-term power transfer requirement. VI. RECOVERY OF INVESTMENT Towards recovery of investment in transmission, it was proposed that immediate evacuation system between generation project and Pooling Station/grid connection point for different generation projects need to be developed by the respective generation developer. However, the common purpose transmission system on various corridors would be developed in phases matching with the commissioning schedule of generation developers. Further, as the transmission corridors was identified based on the target beneficiaries/allocation, hence, developers need to share the transmission charges for particular corridor in proportion to their generation capacity for smooth development of system. VII. STATUS OF 1200KV TECHNOLOGY The 1200kV AC technology is being developed as next higher AC voltage in the country, which is the highest AC voltage level in the world. Development of this technology would go a long way for strengthening of National Grid capacity to take care of long-term power transfer requirement of the country. In order to develop this 1200kV AC technology indigenously, a unique effort has been made, which is first time in India Power Sector, through a collaborative effort between POWERGRID and manufacturers to establish a 1200kV UHVAC Test Station at Bina. This endeavor shall benefit Indian Power sector and manufacturers as availability of 1200KV class equipment within country will not only enable optimisation of transmission cost, but also help in making ease in execution and O&M phase. In this direction, POWERGRID along with 24 manufacturers is establishing a 1200kV UHVAC Test Station at Bina where a 1200KV test line is being constructed along with two 1200KV test bays in which the leading Indian manufacturers in transmission lines and substation are providing main equipment like transformers, surge arresters, circuit Breakers, CTs, CVTs and transmission line hardware etc. These test bays & test line shall be used by the manufacturers and POWERGRID for various field tests so that the results and feedback can be used for developing field proven equipment of 1200KV system in India as well as would facilitate manufacturer to export their equipment. Advanced test facilities like impulse generator as well dielectric test facilities shall also be made available at this test station. Broad insulation levels of 1200kV system have been identified along with rating and size of Surge Arrester and other substation equipment. VIII.CONCLUSION Tremendous growth of Indian Power sector in all fronts viz. generation, transmission and distribution is taking place. National Grid capacity is being enhanced from present level of MW to more than MW by 2012 which shall be further increased progressively. Large capacity addition was envisaged through IPPs/MPPs mainly confined in Orissa, Jharkhand, West Bengal in Eastern Region, Chhattisgarh and M.P in Western Region. However, various uncertainties are associated with above IPPs specially no information about firm beneficiaries, schedule of projects, recovery of investment in transmission etc. This made the transmission system planning and development a challenge. Development of high capacity transmission corridors comprising HVDC and AC system (with a provision to upgrade to 1200kV level at a later date) interconnecting various generation projects through suitable pooling station to major load centres in power deficit Western/Northern Region based on target beneficiaries were proposed. Further, to rationalize transmission charges, proposed transmission system was divided into generation specific-dedicated system to be developed by the respective developer(s) and common purpose system as a regional system strengthening project in which transmission charges also to be shared by the generation developers corresponding to their capacity for smooth development of system. ACKNOWLEDGMENT Authors are thankful to the management of POWERGRID for granting permission to present the paper. Views expressed in the paper are of authors only and need not necessarily be that of management. REFERENCES [1] Report of Working Group on Power for 11 th Plan, GoI: 2007 [2] Integrated Energy Policy-Report of the Expert committee, GoI: August