The Indian power transmission grid is one of the largest operational synchronous grids in the world, with 85,000 MW of interregional transfer capacity. While it facilitates the optimum utilisation of assets, it makes grid planning and operation a highly complex task. Today, grid planning operations have become highly complex with the increasing demand for power, restricted transmission grid expansion, the rising share of renewables and a growing number of distributed energy resources (mostly connected at the distribution level). Monitoring and measurement technologies play an important role in addressing these grid complexities.
The supervisory control and data acquisition (SCADA) system has been a key technology used by transmission utilities to obtain data on energy flows in the grid for its management. However, the increased complexities in the grid have necessitated the use of new monitoring methods and technologies. Wide area monitoring systems (WAMS) and phasor measurement units (PMUs) are two such technologies that enable real-time monitoring of the grid, facilitate enhanced grid management and maximise power transfer. To this end, Power Grid Corporation of India Limited (Powergrid) is implementing the Unified Real Time Dynamic State Measurement (URTDSM) project, which envisages the installation of over 1,700 PMUs across the country. Over 75 per cent PMUs are in place so far. Although progress under the project has been tardy, it is expected to enhance grid management significantly upon completion.
The project was rolled out in 2012 with the aim of improving system operations through the implementation of WAMS. Based on the phasor measurement technology for data acquisition, WAMS consists of four key elements: PMUs, phasor data concentrators (PDCs), communication networks and analytical software. As part of the project, 1,669 PMUs were initially planned to be installed across the five regional grids. However, the number of PMUs was increased to over 1,700 due to the commissioning of new stations and feeders during the course of the project. The project is also expected to see the installation of 57 PDCs and 16 remote consoles, and the establishment of a communication network.
The Rs 3.81 billion project was awarded to GE Power (previously Alstom) in January 2014. The WAMS solution will obtain input data 25 times per second from all the PMUs installed as compared to the conventional SCADA system that collects data once in five seconds. It will also include geographic displays to provide real-time views of the grid, analytical applications and have the capacity to store 500 TB of data. With latest firewall policies incorporated, it will fully secure the grid from cybersecurity threats. Almost 70 per cent of the project cost is being funded by the Power System Development Fund (PSDF). For URTDSM implementation, Powergrid received Rs 1.16 billion and Rs 0.63 billion from the PSDF in 2017-18 and 2016-17 respectively.
Awarded in January 2014, the project was to be completed within 24 months. However, the implementation has been slow. As of March 2018, only 1,314 PMUs were installed under the URTDSM, covering 316 substations. Of these, 1,165 PMUs were integrated with the regional load despatch centres. Once fully commissioned, the WAMS solution will be the world’s largest, covering 34 control centres and 350 substations in the national grid.
Stage I of the project was commissioned in July 2018. This has enabled Powergrid to monitor the power flow across 110 substations in the northern grid. The northern grid covers nine control centres – Punjab, Haryana, Rajasthan, Delhi, Uttar Pradesh, Uttarakhand, Himachal Pradesh, Jammu & Kashmir, and Chandigarh. In October 2018, the Southern Regional Power Committee commissioned the PMUs and associated equipment envisaged under Stage I of the project for the southern region.
Analytics applications such as line parameter estimation, vulnerability analysis of distance relay, and linear state estimation have been developed in association with IIT Bombay and are being deployed at control centres across the country.
The project is nearing completion now. Once in place, it will be critical to addressing power demand-supply imbalances and ensuring grid stability in light of the large-scale grid integration of renewables. The project will enable grid operators to respond to fluctuations within a fraction of a second. This will increase the effective capacity of congested corridors, improve transmission asset utilisation, and lower energy costs for consumers. n