By bappaditya paul
For quicker augmentation of the faulty distribution mechanism often blamed for blackouts in the state, the state power department is shifting its focus to a comparatively new type of power sub-station that takes half as long to build as a conventional one.
A gas-insulated substation (GIS) can be ready in about six months, while its conventional counterpart ~ an air-insulated sub-station (AIS) ~ takes a year. Given this, GIS sub-stations are considered an ideal option for West Bengal, where citizens often suffer power cuts despite surplus generation.
“Our present power-generation capacity is 4,933 megawatts and the average peak-hour demand is pegged at around 4,500 megawatts,” said state power minister Manish Gupta.
“Going by our assessment of the demand scenario, we are capable of meeting the further increase in demand for at least the next year. But despite this, people in the state are sometimes witnessing power cuts and low voltage because of lapses in the distribution mechanism,” he said.
“To address this problem, we have decided to streamline the supply network and construct more 33/11 kV power sub-stations as soon as possible. For this, we have asked the state-owned power distribution companies to go for GIS sub-stations, which become ready in six months and are also more efficient,” he said. At present, the state has only one GIS sub-station ~ a 400 kV version at the Purulia Pump Storage Scheme. In the 2012-13 fiscal year, the power department has set a target of constructing 18 new 33/11 kV substations. Work has already started on a GIS sub-station for the West Bengal State Electricity Distribution Company Ltd at Barrackpore in North 24-Parganas. Two more GIS substations are being constructed by the West Bengal State Electricity Transmission Company Ltd at Bagnan in Howrah and in Murshidabad. Another is planned for Cooch Behar.
To the advantage of the power department, a GIS sub-station needs only a quarter of the land required for an AIS substation. “This is because, in an AIS sub-station, the busbars and equipment terminations are installed in an open ground with specified gaps in between and this increases the land requirement,” a senior power department official said.
“Whereas, in the case of a GIS sub-station, all major equipment ~ such as isolators and breakers ~ is housed in a compact metal case with sulphur hexafluoride (SF6) gas playing the role of the insulating medium. This reduces the land requirement by about three-quarters,” the official said.
While about one acre land is needed for a 33/11 kV AIS substation in the state, the GIS sub-station requires only 25 decimals. The cost of building a GIS sub-station, however, is higher (Rs 5 crore), than the cost of building a conventional AIS sub-station (Rs 4 crore).
(The author is on the staff of The Statesman, India. This piece first appeared in The Statesman on 16 July 2012.)