New record established for AC switching voltage1 January 2015
ABB has installed and commissioned in India an AC circuit breaker that at 1.2 million volts is established as the highest AC voltage breaker installed anywhere in the world. It will support the country’s plans for its ultrahigh voltage grid.
ABB has designed, manufactured, installed and commissioned a 1200 kV circuit breaker, the highest AC voltage level in the world for an installed switching unit.
Once the ultrahigh voltage (UHV) switchgear is fully operational, it will have a switching capacity of 10 400 MW - a switch capable of turning 'on' or 'off' the electricity generated by 10 large power plants or the combined average annual electrical load of Switzerland and Denmark, within milliseconds.
The circuit breaker, a GIS ELK-5 unit, the most recently introduced of ABB's ELK range of GIS HV switchgear, is deployed at the 1200 kV national test station constructed by Power Grid Corporation of India Limited (PGCIL), India's central transmission utility, at Bina in the central Indian state of Madhya Pradesh. Alongside the circuit breaker is what ABB describes as a 'state-of-the-art hybrid switchgear solution' comprising a gas-insulated disconnector, current transformers and monitoring and diagnostic equipment. As it is GIS, it requires only half of the floor space that would be needed for switchgear with conventional air-insulated designs. The configuration also protects critical components from environmental exposure and makes them more resilient to potential earthquake disturbances.
India is currently adding substantial amounts of power generation capacity to meet growing demand, amounting to 100 MW in the 12th 5-year plan, which in a large country like India also requires an efficient and reliable transmission and distribution infrastructure, capable of delivering the greatest possible amount of power over long distances with transmission losses kept as low as possible, but which at the same time saves space and reduces environmental impact. These are some of the considerations which have prompted India's central TSO to embark on the development of a 1200 kV transmission system.
“ABB has a long track record in India and we are pleased to continue to support the country in the development of an efficient and reliable power grid. Ultra high-voltage technologies are especially suitable for large countries such as India where power often has to be transmitted over large distances from generation to load centres in the most efficient way," said Bernhard Jucker, head of ABB's Power Products division.
“PGCIL is fully engaged in developing a robust and integrated national grid along with reliable partners ... This development takes us a step further in the development of our ultra high voltage transmission network," commented R N Nayak, chairman and managing director of PGCIL.
The commissioning of this substation in the 2 km line at Bina represents a milestone in a greater plan to create a new 1200 kV commercial AC line over 400 km between Wardha and Aurangabad by 2015. It is essentially a demonstrator, but will have the distinction of being the world's highest voltage power transmission line. At present, it is running at 400 kV but when the Power Grid Corporation of India is ready, the capacity of the line will be raised to 1200 kV.
The test line at Bina, intended as a field trial centre, was constructed in a co-operative effort by a number of transmission equipment manufacturers including BHEL, Areva and Siemens. It has two 1200 kV test bays for which various leading manufacturers provided the main equipment - transformers, surge arresters, circuit breakers, transformers and so on. among other components.
Installation in China
ABB operates in about one hundred countries but has a large presence in particular in China and India, and it is in China that the first ELK-5 was installed, at the Jingmen substation for State Grid Corporation of China, and part of the first UHV transmission line in the country. The design features circuit breakers with four interrupters in series, high capacity pre-insertion resistors and a very compact design.
Ultra high voltage above 800 kV is currently the highest voltage level in use for bulk AC power transmission across long distances. State Grid Corporation of China (SGCC) is operating UHV lines at 800 to 1000 kV to connect load centres to distant power plants and to improve network stability. Russia is planning a similar network. But it isn't new as a concept and a number of UHVAC circuits have already been constructed in different parts of the world. For example 2362 km of 1150 kV circuits were built in the former USSR and 427 km of 1000 kV AC circuits have been developed in Japan (the Kita- Iwaki powerline) while experimental lines at various voltages have also been constructed in several other countries. However, most of these lines are not currently operating at UHV - they are running at lower voltages owing to insufficient power demand or for other reasons.
The most operating UHVAC is to be found in China where nine UHV AC or DC circuits are completed or under construction. The completed UHVAC circuits are:
• Jindongnan-Nanyang-Jingmen (JNJ), a 654 km, 1000 kV circuit. Construction started in November 2006 and completed in December 2008 with a capacity of 2800 MW. Its capacity was expanded to 5000 MW in December, 2011.
• Huainan - Shanghai: 2x649km, a ±1000 kV double circuit UHVAC with 8000 MW capacity, Construction started in October 2011, and completed in September, 2013.
• There is one line under construction, the Zhejiang North - Fuzhou (ZF), a 2x603 km, ±1000 kV double circuit UHVAC with a capacity of 6800 MW. The line started construction in April, 2013, and is planned to be operational by March 2015.
(Originally published in MPS January 2015)