Fixing India’s grid – a lesson in dynamic control4 April 2014
Alstom says that its new e-terra3.0 product is the most advanced suite of products for the 21st century grid. This claim will be tested to the full when it is installed by PGCIL which operates the largest synchronised grid in the world. Dynamic grid control on this scale has never been attempted before.
The Indian electricity network is today the world's largest synchronised grid with a capacity of 232 GW. But the widespread power blackouts of 2012, unprecedented anywhere in the world at that time, raised many questions about the security of the country's grid, and among the raft of proposals that came from the studies that followed the event was a determination to improve out of hand the grid's information gathering systems.
As part of its commitment to the ideal of protecting the grid, Power Grid Corporation of India Limited, India's central transmission utility, has contracted with Alstom T&D India to deliver its latest generation of grid security technologies for a critical energy management programme, entitled 'The Unified Real-Time Dynamic State' project.
In what will be the world's largest grid-based wide area monitoring system, this significant development will enable nation-wide monitoring of power flows across the grid, responding to fluctuations within a fraction of a second. Real-time data will ensure that PGCIL can intervene immediately to match electricity supply to demand.
Valued at INR 3817 million (€41 million), the contract covers the supply of a state-of-the-art hardware and software solution. For the hardware, Alstom will provide more than 1300 MiCOM P847 phasor measurement units (PMU), to collect over 18 000 real-time synchronised measurements from 351 substations across the country. Phasor measurement units are precision devices which measure the electrical characteristics of an electricity grid in real time.
This precision in phase measurement has been made possible by the existence of extremely accurate clocks linked to the global satellite system, able to use a global time source for synchronisation. Alstom will also equip 34 control centres at existing national, regional and state load dispatch sites with a product called 'e-terraphasorpoint', part of the 'e-terraplatform' portfolio of EMS products, a WAMS software solution that analyses weak spots in the system in real-time. It will detect evolving disturbances, tap into latent electricity capacity across electrical transmission corridors, and provide actionable information to system operators that can then take decisions quickly enough to prevent blackouts.
The wide area monitoring system provides, in terms of the scale of the operation, a time-synchronised snapshot of conditions across the entire country. Although versions of the system have been deployed already in the USA and South Africa, nothing on this scale has yet been attempted.
It will provide visibility on power system dynamics and wide-area stress indicators across India's vast circuit of some 102 100 km of electrical grid, which ranges from 132 kV to 765 kV AC, with 172 substations. Achieving this ambition would be a major milestone in ensuring the reliability of electricity supply across the country.
Patrick Plas, senior vice president, Power Electronics & Automation, Alstom Grid, commented: "This is a significant step change in India's energy management. The timeliness and quality of the data will provide control room operators with the smartest tool yet to optimise the existing grid assets. This will ensure reliability, and ultimately provide the highest availability of electricity to India's citizens. This is unmatched in the history of grid management."
Alstom says that its new e-terra3.0 product is the most advanced, fully integrated, smart grid-ready suite of products for the 21st century grid. It is a flexible, scalable and extensible phasor-based wide area management system integrated with the e-terraplatform solutions for energy management systems order to transform phasor data into actionable information to improve system security and capacity, co-ordinate WAMS and EMS to provide a unified view of the power system, enhancing operator and analyst decision-making, and enable strategic development of control centre systems with the critical involvement of phasor-based information sources.
Management functions include transfer constraint relief, power system dynamics risk assessment, dynamic model validation, tuning of power system stabilisers, and managing islanded situations and resynchronisation. It is, says Alstom, able to exploit the synergies among WAMS, EMS and dynamic security assessment to improve performance in operations, analysis, modelling and control.
Benefits: managing the risks of blackouts
The system is said to manage the risks of blackouts while not over-constraining the grid. Dynamic threats such as oscillations, separation and major disturbances can be observed and managed. This is achieved by functions that include situational awareness & operational response - the system alerts an operator to an emerging problem for defined corrective action to be taken, a wide area alarm alert system, constraint relaxation (relieving constraints based on oscillation damping; it can also be used for other forms of constraint relief including angle-based limits).
Other features include model validation - improving dynamic models using phasor measurements and continuous observation of oscillations, leading to better design of stability controls; the connection of renewable energy - the capability of the network to accommodate intermittent renewable resources can be increased through the use of angle-based controls, while stability issues such as frequency stability, common-mode disturbance and model validation can also be addressed; and compliance monitoring, that is, retaining information to comply with regulatory disturbance reporting requirements.