country ran on the Harbour Line between Bombay's Victoria Terminus and Kurla on 3 February 1925. The first high-voltage laboratory of India was established at the Government Engineering College, Jabalpur in 1947. On 18 August 2015, Cochin International Airport became the world's first fully solar powered airport with the inauguration of a dedicated solar plant. India began using grid management on a regional basis in the 1960s. Individual State grids were interconnected to form 5 regional grids covering mainland India, the Northern, Eastern, Western, North Eastern and Southern Grids. These regional links were established to enable transmission of surplus electricity between states in each region. In the 1990s, the Indian government began planning for a national grid. Regional grids were initially interconnected by asynchronous high-voltage direct current (HVDC) back-to-back links facilitating the limited exchange of regulated power. The links were subsequently upgraded to high capacity synchronous links. The first interconnection of regional grids was established in October 1991 when the North Eastern and Eastern grids were interconnected. The Western Grid was interconnected with these grids in March 2003. The Northern grid was also interconnected in August 2006, forming a Central Grid that was synchronously connected and operating at one frequency. The sole remaining regional grid, the Southern Grid, was synchronously interconnected to the Central Grid on 31 December 2013 with the commissioning of the 765 kV Raichur-Solapur transmission line, establishing the National Grid. By the end of the calendar year 2015, despite poor hydroelectricity generation, India had become a power surplus nation with huge power generation capacity idling for want of demand. The calendar year 2016 started with steep falls in the international price of energy commodities such as coal, diesel oil, naphtha, bunker fuel, and liquefied natural gas (LNG), which are used in electricity generation in India. As a result of the global glut in petroleum products, these fuels became cheap enough to compete with pit head coal-based power generators. Coal prices have also fallen. Low demand for coal has led to coal stocks building up at power stations as well as coal mines. New installations of renewable energy in India surpassed installations of fossil fuel for the first time in 2016–17. On 29 March 2017, the Central Electricity Authority (CEA) stated that for the first time India has become a net exporter of electricity. India exported 5,798 GWh to neighboring countries, against a total import of 5,585 GWh.