16th IMEKO TC4 Symposium Sept. 22-24, 2008, Florence, Italy A Grid Transaction Index for a Power System with Availability Based Tariff Geetha T 2 , Jayashankar V 1 , Jagadeesh Kumar V 1 , Sankaran P 1 1 Professor (Indian Institute of Technology, Madras, e-mail-jshankar@ee.iitm.ac.in) 2 Research Scholar(Indian Institute of Technology, Madras, e-mail-geethajc@yahoo.com) Abstract- The Indian power system is a large network with an installed capacity of 140GW. It is unique in that it is the only network which allows the operating frequency to vary over a band from 0.5 Hz to -1.0 Hz from the nominal 50 Hz. The pricing for power purchased is a function of the operating frequency following a commercial mechanism called availability based tariff. Since the network consists of several states which are each commercially independent, an elaborate metering system is required at the interconnecting 400 kV grid. Since 2004, 461 special energy meters with 0.2 class accuracy have been erected across the network. They provide online information about key network parameters in addition providing the data for commercial transactions. We show several examples of the utility of this measuring system with regard to scheduling plants in the network, planning and control studies. We propose a grid transaction index that would help assess the state of the network and the performance of various state’s dispatchers. All discussions are based on the data of Tamil Nadu Electricity Board (TNEB), a utility in the Southern region. I. Introduction The Indian power System is demarcated into five regions – Northern, Southern, Western, Eastern and North_Eastern. Of these the Western, Eastern, North Eastern and Northern regions are synchronously tied (since 2003) while Southern region is on HVDC links. Figure 1 shows the Indian power network with the major tie lines and installed capacity. Each region has four or five states and most of the state generation is owned by the State Electricity Boards (SEBs) which are vertically integrated utilities. Apart from this, each state is entitled to a fixed percentage of power from Central government owned generation. The growth of Independent Power Producers (IPP) is also significant in the past two decades. Synchronous NORTH NORTHERN EASTERN EASTERN 33256 MW 18020 MW 2333 MW Synchronous Figure 1. Schematic of the Indian power network. Automatic generation control is not implemented for dispatch and most of the governors of the state generating stations are blocked. Instead generation is controlled once in 15 minutes in response to a price signal generated by the Availability based tariff (ABT) mechanism [1, 2]. This commercial mechanism was introduced in Indian Electricity Act 2003 by Central Electricity Regulatory Commission (CERC) and it defines the tariff structure for bulk power purchase by state utilities from Central Generating Stations(CGS). It was based on the recommendations of the study carried out by M/s ECC of USA sponsored by World Synchronous WESTERN 34020 MW Synchronous HVDC HVDC SOUTHERN 37372 MW