Transmission

An Overview of Power Transmission in India

At the time of Independence power systems in the country were essentially isolated systems developed in and around urban and industrial areas. The highest transmission voltage at the time was 132 kV. The frame work for development of power sector was set with the enactment of Electricity (Supply) Act, 1948 providing for establishment of CEA for coordinated development of Power Sector and was made responsible for formulating plans for power development and coordinating the activities of the planning agencies in relation to the control and utilization of national power resources. The Act also provided for formation of State Electricity Boards (SEBs) in the States. The SEBs were responsible for development of generation, transmission, distribution and utilization of electricity in their respective States. The objective of development was to have a coordinated process towards integrated system.

The systems around urban and industrial areas grew into full fledged State Grid systems. In 1964, the country was demarcated in to five Regions viz. Eastern Region, Northeastern Region, Northern Region, Western Region and Southern Region, also the Regional Electricity Boards were established in each of the regions for facilitating integrated operation of state systems and encouraging exchange of power among the states. For the purpose, inter-state lines were planned which were treated as centrally sponsored schemes.

In 1975, Central Sector generation utilities viz. NHPC and NTPC were created, the construction of associated transmission system for evacuation of power as well as delivery of power to the constituent states was also entrusted to these corporations. With this, the focus of planning and development in the transmission system shifted from State Grid system to Regional Grid system. As a result, regional networks were formed and by the end of 1980's strong regional networks came into existence.

In 1989, the transmission wings of these Central Generating companies were separated to set up Power Grid Corporation of India (POWERGRID) to give thrust to implementation of transmission system. A few inter-regional links were also planned and developed to facilitate exchange among the various regions. However, these inter-regional links were planned for emergency assistance and transfer of operational surplus between the regions in a limited manner only. The operational mechanism including resource planning as well as grid operation and consequently the operational frequencies of various regions continued to be Region specific. Hence, as the operational frequencies of the regions were different, the power exchanges through AC lines could take place only in a limited manner through radial mode operation. To facilitate inter-regional exchanges between asynchronously operating regional grids, HVDC back-to-back links were developed. This included 500 MW link between Northern and Western Region at Vindhyachal, 1000 MW Western and Southern Region link at Bhadravati and 500 MW between Eastern and Southern Region link at Gazuwaka.

Development of the transmission network has been done in tandem with growth in generation capacity. The growth in transmission system is characterized by the physical growth in transmission network as well as introduction of higher transmission voltages and new technologies for bulk power transmission. Landmark of this growth had been introduction of 220 kV in 1960, 400 kV in 1977, HVDC back-to-back link in 1989,±500kV, HVDC bi-pole line in 1990 and 765 kV transmission line (initially charged at 400 kV) in 2000. The future growth plan is 765kV operation of 765kV line in 2007 (with Sipat transmission system) and ±600kV, 4000 MW HVDC bi-pole line in 2011 (with Subansiri transmission system).

Power Grid Corporation of India 

The Power Grid Corporation of India (POWERGRID), India's national transmission utility, is the main implementing agency of this program. Currently, there are five regional transmission grids for the northern, eastern, north-eastern, western and the southern regions. In India, transmission is a Central as well as state subject, with transmission activities at inter-state level are controlled by the Centre and at intra-state level is controlled by the State. Development of the transmission network has been done simultaneously with growth in installed generation capacity. Introduction of 220 kV in 1930, 400 kV in 1997, HVDC back-to-back link in 1989 and 765 kV transmission line (initially charges at 400 kV) in 2000 and increased in total length of high tension transmission lines at 132 kV and above in the country from 2708 ckm in 1950 to more than 2,25,720 ckm of transmission lines by 1995 and 3,17,500 ckm by 2007 are some of the indicators of the progress.

PGCIL owns and operates a network of 92,946 ckm of lines, 150 EHVAC/HVDC Substations and a transformation capacity of about 1,24,525 MVA. The network currently wheels about 51% of the total power generated. Currently, four of the five regional grids have started operating in synchronous mode, forming the North East West (NEW) grid. The current inter regional power transfer capacity of the national grid is 28,000 MW. In 2008-09, 46000MUs of inter regional power exchange helped meet the demand in energy deficit regions. An investment of RS 1400 billion has been planned for transmission sector projects ( 220kV and above) during the XI plan period. Of this PGCIL is likely to invest INR 500 billion.

An extensive network of Transmission and Distribution lines has been developed over the years for evacuating power produced in the various generating stations and distributing the same to the consumers. Depending upon the quantum of power and the distance involved lines of appropriate voltages are laid. The nominal Extra High Voltage lines in vogue are HVDC, 400 KV, 230/220 KV, 110 KV and 66 KV lines have been introduced so far by the SEBs are Punjab, U.P, W.B, M.P. Maharashtra, Gujarat, Karnataka, Bihar and Orissa as also by BBMB (Punjab) and Central Sector only.

The standard voltage of operation on the distribution side are 33 KV, 22 KV,11KV, 400/230 Volts besides 6.6 KV, 3.3 KV and 2.2 KV. The low voltage system has 3 phase 4 wires supply giving 400/420 volts between 2 phases and 220/240 volts between phase and neutral. This has been universally adopted throughout the country.

One of the major reasons of power shortage in the country is high transmission and distribution losses which include power thefts and non-payment by priority sectors. In addition to this is the poor financial conditions of SEBs many of whom have mounting dues aggregating over Rs 100 billion. The restructuring of the power sector, reform of the SEBs rationalization of tariff, improvement in not only generation but also in distribution and transmission, and above all a commercial re-orientation of the entire sector are the core issues to be dealt with for toning up the sector performance.

 Transmission System operation

The Power sector in India is undergoing changes. The movement is from a controlled electricity sector towards a competitive and market driven sector. Government owned vertically integrated big electricity utilities have given way to independent generation, transmission, distribution, and trading companies. India has a regulator in place, to take care of the market imperfections, due to restricted number of players or natural monopoly. In India, at present, the power system the functions being performed by the System Operator, called as the Load Dispatch Centre. In a modern power system the functions being performed by the System Operator, called the Load Dispatch Centre, are normally the following:

  • Provides open access to the transmission system,
  • Monitors and controls system operations to ensure a moment-to-moment energy balance,
  • Manages congestion.
  • Schedules generation (or reviews the technical feasibility of schedules submitted by others),
  • Acquires ancillary services such as operating reserves and voltage support,
  • Plans or approves requests for maintenance of transmission and generation facilities.
  • Many system operators also administer spot and real-time balancing energy markets. These operators generally perform metering, accounting, settlement, and billing for the markets.

India has been divided into five Regional Grids namely Northern, Southern, North-Eastern, Eastern & Western Regions for Power System Planning, operation and control. The rapid growth coupled with vast geographic spread of the Indian Power System has made the task of operation and management of such an integrated Power System complex and challenging. It requires coordination amongst various Central and State sector generation, transmission and distribution utilities. Each of the regional grids requires adequate mechanism to ensure smooth operation both under steady state and emergency conditions. All the users have to strictly adhere to the generation and load schedules and maintenance of voltage and frequency parameters.

This necessitated modernization of the existing Load Despatch and communication facilities to operate the national and regional grids so that it could deliver quality power economically, reliably and securely. In 1992, the Government of India started implementation of a Unified Load Dispatch and Communication Scheme (ULDC) in the country for creating a modern infrastructure to operate the transmission system.

The Load Despatch and Communication Scheme was initiated for all the five Regional Grids of the country for implementation in a phased manner for real time Grid Management and economic despatch of power in a unified manner, with state-of-the-art Supervisory Control and Data Acquisition (SCADA), Energy Management System (EMS) and dedicated Communication System at an investment of about Rs 2200 crores. These schemes ensure real time monitoring and control of Regional Grids and minimize Grid disturbances. The scheme is expected to culminate by December 2007 with the full fledged establishment of the National Load Dispatch Center to supervise the real time grid operation at National level. Under these schemes, the data of the entire power system in a particular region are electronically collected and transferred to a Regional Load Dispatch Centre using dedicated broadband communication system. The hierarchy of system operations at different levels consists of National Load Despatch Centre (NLDC), Regional Load Despatch Centre (RLDC's), State Load Despatch Centre (SLDC) and Regional transmission Units (RTU).

Private Sector Participation in Transmission

To encourage private investment in the transmission business, the Central Government enacted the Electricity Laws (Amendment) Act in August 1998. This Act provides for state transmission utilities and transmission licensees, and thereby facilitates state power reform and private investment in power transmission. Two distinct routes for private sector participation in transmission have been envisaged.One route is through Joint Venture, with equity participation, of at least 26%, by CTU or STU (State Transmission Utility) with by the Joint Venture Partner (JVP), a private agency. The Joint Venture Partner is selected through the competitive bidding process. The first project implemented by the JV route was the Tala-Delhi transmission link. These lines are associated with the Tala hydel power plant in Bhutan, East-North inter-connector and the northern region transmission system, to add to the existing 400 kV Bongaigaon-Siliguri D/C (direct current) transmission line, and the 200 kV Salakati-Birpara D/C link to transfer electricity from the eastern and north-eastern regions to electricity-deficit northern belt. The project was successfully implemented by the Powerlinks Transmission Ltd, a 49:51 joint venture of PGCIL with Tata Power.

Second route is through Independent Private Transmission Company (IPTC), with full fund mobilisation by the private entrepreneur, i.e, 100 percent equity shall be owned by the private entity. The IPTC is also selected through a competitive bidding process. The project taken up through the IPTC route, for implementation on build, own, operate and transfer (BOOT) basis, was the 400 kV D/C line from Bina to Dehgam via Nagda for moving power from Sipat power station of NTPC in Madhya Pradesh, Rajasthan and Gujarat.

In January 2007, In a bid to attract private sector participation in the power transmission sector, the Government at Centre has decided to award 14 large transmission projects, entailing a total investment of about Rs 20,000 crore, through tariff-based competitive bidding route. The projects, awarded on a build-own-operate (BOO) basis, were managed through special purpose vehicles (SPVs) set up by two State-owned finance firms, viz. the Power Finance Corporation Ltd (PFC) and the Rural Electrification Corporation (REC), as the nodal agencies. The SPVs looked into the contentious issues such as initial and detailed surveys and feasibility reports, obtaining transmission licence, obtaining right of way, site identification and land compensation before giving these projects to the developers.

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