New 1200 kV Test Station Will Support Development of UHV Network in India

New 1200 kV Test Station Will Support Development of UHV Network in India

UTILITY PRACTICE & EXPERIENCE

New 1200 kV Test Station Will Support Development of UHV Network in India

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A key milestone in this process was the recent commissioning of the National Test Station located in Bina, in the central State of Madhya Pradesh. INMR Columnist Alberto Pigini travels to Bina and reports on the impressive infrastructure as well as what it hopes to accomplish.

Photos: Courtesy Alberto Pigini

ast year, the electrical power industry serving the world’s second most populous nation took an important step in transforming a grid that spans more than 3.3 million sq. km. Spurred on by projected 8 to 9 percent annual growth in demand, engineers in India have been busy laying the framework for an ambitious move into UHV that will result in 1200 kV lines each transporting from 6000 to 8000 MW of bulk power along expanded existing corridors.

Different phases on towers at Bina will be used for comparative assessment of insulator and hardware designs from different local suppliers.

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1200 kV single (energized May 2012) and double circuit suspension towers (energized October 2012). Single circuit tower requires right of way of 89 m.

India’s sprawling transmission grid consists of some 95,000 circuit-km of 400 kV (mainly) and 765 kV lines as well about 125,000 circuit-km of lines operating at 220 kV. In addition, there is a DC system comprising around 7500 km of ± 500 kV lines.

Vast as that system is, however, it cannot cope with the lofty projections for incremental power throughput required to meet economic development targets over the coming decade.

Phots: Courtesy Alberto Pigini

For example, based on estimated average GDP growth in coming years, peak demand is expected to increase from the present 168 GW to 250 GW in 2017 and then to 372 GW by 2022. To transport the additional power needed under such a scenario, the existing number of transmission corridors would have to be significantly increased. But in the case of India, with limited land availability, growing ecological advocacy and many landowners, this would prove a formidable if not impossible challenge.

It was these types of considerations that drove planners at India’s PowerGrid to look toward UHV as the only realistic alternative to meet the country’s future electricity requirements by making maximum use of existing or slightly expanded power corridors.

All diagrams: Courtesy PowerGrid of India

While 1200 kV may seem as breaking new ground, the first application of such a system voltage was actually tested and commissioned almost 30 years ago in the former Soviet Union. Even before that, Japan had energized a limited 1000 kV system while researchers in Italy also developed and tested equipment for such a system. China started R&D on its own 1100 kV network in 2005 and a 650 km pilot project was launched in early 2009 that is the basis for additional lines now on the drawing boards or already under construction (see INMR Q1 2010 & Q4, 2012).

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Phots: Courtesy Alberto Pigini

Example of one of three competing designs of 1200 kV capacative voltage transformer (center left).

1200 kV breaker for R phase designed for 2400 kV lightning impulse withstand, 1800 kV switching impulse withstand, 5000 A normal current and 50 kA breaking current.

In the case of the new Bina facility, the investment was shared by the publically owned grid operator as well as a consortium that now numbers some 35 indigenous suppliers of electrical equipment and components. While PowerGrid provided the test bed for the field trials, all equipment was internally developed and financed by these individual suppliers. The goal behind this partnership was to promote rapid development of domestic expertise in UHV, especially in light of the fact that there are still no international standards to rely on.

One of the interesting features in building the test circuits at Bina was that construction techniques and equipment used for tower erection and stringing had to replicate, as much as possible, what would reasonably be available to crews in the field – even across the more remote areas of the country. The test station’s circa one kilometer single circuit and double circuit lines will also provide Indian engineers with valuable information on operational and safety requirements at such a UHV level.

Among the more notable features of the technology now in place at Bina is that it was apparently developed from system studies at 1200 kV and not based on simply extrapolating parameters from existing 400 kV/765 kV networks. Moreover, the decision to go with an operating voltage of 1150 kV versus the 1000 kV level selected by engineers in China was to obtain higher power transfer capabilities while keeping basically the same switching and lightning impulse insulation levels using high performance, multi-column surge arresters. The somewhat reduced insulation level margin would then be offset by gains in optimizing cost and sizing of associated equipment, the latter especially important given limitations in transport infrastructure.

In order to best allow comparative assessment of performance, much of the equipment such as the 1200 kV single-phase transformers, capacitive voltage transformers and polymeric surge arresters involve a different supplier for each phase. This applies as well to the 1200 kV circuit breakers, one of which utilizes two-column composite housed bushings while the other is designed with huge onepiece composite housings.

1200 kV bus post insulators for all phases come from only one local supplier.

Second phase charging of the test station is currently scheduled for August of next year. ď ¸

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