1 Operating Experience of Regional Interconnections In India Anjan Roy, S. A. Khaparde, Senior Member, IEEE, P. Pentayya, S. Usha, A. R. Abhyankar Abstract— That regional interconnections can benefit intercon- nected grids is accepted by the decision makers owing to optimal utilization of resources, diversity of load patterns, increased security and improved system performance. However, there are “oportunities and threats” depending on how commercial, operational and security issues are tackled. The threats stem from potential seaming problems in the integration and lack of adequate defense mechanisms. In India, five large sized regional grids operate and these are interconnected either synchronously or asynchronously. The operating strategies for interconnections have evolved through trial operations on exiting system which are covered in this paper. The paper overviews the salient features of all the regional interconnections in India. The commercial mechanism, Availability Based Tariff (ABT), adopted by India has facilitated seamless integration on commercial front to a good extent as described in this paper. ABT links part of tariff with a universally available signal of system frequency. From experience gained over last few years, the operational and security issues have been discussed. With Open Access in operation, the interconnecting corridors have to play a significant role in the operation of the interconnected system. The need for evolving standards for the integrated operation became evident from the experience. The guiding principles for such standardization are also reported in this paper. Index Terms— Regional Interconnections, Operation and Con- trol I. I NTRODUCTION W ITH population over 1 billion people, India is one of the fastest growing economy. Electric Supply Industry plays a key role in development. Building the regional inter- connections, though a most welcome step, remains a complex and challenging task for planning and operation. In literature, [1] [2] and [3] have dealt with Interconnection issues in China and Arab world. In [2], it is pointed out that if the growth rate is low, the weaker links may be preferable. This is at the cost of potential problems of stability. Though there are generic principles governing the philosophy of interconnections, some issues are system specific to a nation. India has to deal the system specific issues in an innovative way. The special features of Indian power system include generation deficiency, large frequency deviations and different operational practices in different regions. Some references to Indian power systems conditions are reported in literature. One of them deals with Chandrapur HVDC interconnecting link design details [4]. In S A Khaparde (email: sak@ee.iitb.ac.in) and A R Abhyankar (email: abhijit@ee.iitb.ac.in) are with Department of Electrical Engineering, Indian Institute of Technology Bombay Mumbai, 400076, INDIA. Anjan Roy (email: gmwrldc@rediffmail.com), P.Pentayya (email: ppentayya@indiatimes.com, S. Usha (email: usha s gopi@rediffmail.com ) are with Western Regional Load Dispatch Center (WRLDC), Power Grid Corporation of India Ltd., Mumbai, India. [5], [6], interconnections in South Asia in Indian context are briefly described. Building of Indian Grid and its benefit to China is discussed in [7]. The international interconnection scheme for Greater Mekong Subregion connecting six Asian countries is reported in [8]. In India, the regional intercon- nections have become operational since last two years. The experience gained from these operations is subject matter of this paper. The paper overviews all regional links with their special features in an exhaustive manner. The paper also comments on possible National grid operation. The standard practices for regional link operation have been suggested. The Indian power system is having an installed capacity of 110 GW and is meeting a peak demand of around 70 GW [9]. The Indian power system is operated as five Regional grids viz., Northern Regional grid (NR), Western Regional grid (WR), Eastern Regional grid (ER), Southern Regional grid (SR) and North Eastern Regional grid (NER). Three of the regions, viz. NR, WR and SR suffer from severe deficits while ER is having surplus generation of about 2500 MW and NER is having marginal surplus based on hydro reservoir levels. The regions are connected to each other either through asynchronous links (HVDC back-to-back) or AC links to enable exchange as and when available surpluses. The objectives of interconnecting the five regional grids in the country through synchronous and asynchronous links are to enable transfer of power from surplus regions to deficit regions, to enable optimal development and utilization of coal, gas and hydro resources in the overall interest of the nation and to improve economy, reliability and quality of power supply. With the Open Access in transmission since May 2004, the interconnection of grids shall achieve the objective of cheaper power displacing the costlier power and reduction of cost to the consumer. The regional interconnections involve operating large grids in tandem and there are opportunities as well as threats to deal with and these are summarized below: Opportunities: Help in exchanging power as and when available, i.e. infirm and economy exchanges. Increased stiffness in the case of synchronous inter- connection. HVDC back to back helps in inter-connecting regions with different frequencies. Faster emergency frequency control. Evacuation of surplus power in some regions like ER and NER. Increased open access transactions with cheaper power displacing costlier power. Authorized licensed use limited to: INDIAN INSTITUTE OF TECHNOLOGY BOMBAY. Downloaded on December 4, 2008 at 05:12 from IEEE Xplore. Restrictions apply.