What came as a blessing in disguise for the southern region and saved it from a network crash when 21 States in the north, the east and the northeast witnessed serial electricity grid collapse on July 30 and 31 was principally the fact that the south was not inter-connected with the rest.
Strictly enforced grid discipline was a second factor. Although the crisis in the upcountry regions did cause substantial power losses to the southern States, sophisticated protection mechanisms adopted by the grid also saved the day.
Tamil Nadu normally gets 1,050 megawatt (MW) from the eastern region, but the grid collapse stanched it. As of August 1, supply to the extent of 250 MW was restored, and steps are on to make up for the rest.
Ironically, the absence of inter-connectivity has been viewed by the southern States as a handicap, as they were not able to draw from power-surplus regions. Particularly during summer, the south felt the pinch in two ways. The region could not receive the contracted quantum from others. And, the rate at which power was offered to them was nearly four times the rate at which others got it.
Grid discipline has been good in the south. At present, the frequency can go down up to 49.5 cycles against the ideal level of 50. If in any State it crosses the threshold, the Southern Region Load Despatch Centre pulls up the State concerned. Such monitoring and enforcement on a real-time basis force the States to fall in line. In order to observe grid discipline, the quantum of load shedding has gone up in the last few days.
In Kerala, however, the upcountry outage necessitated load shedding. A top official said the Kerala State Electricity Board (KSEB) had to resort to cyclical load shedding during the day and late in the evening. Load shedding varied from 30 minutes to one hour, and in some areas, it had to be done more than once. “We had to go for load shedding and also increase the generation of hydro power to the maximum extent the last two days to minimise the impact of the north Indian power outage,” he said.
The hydel stations provide a cushion in such situations. Due to the indifferent monsoon, the KSEB had been conserving the storage.
During the evening peak hour, the load in the KSEB system had been in the range of 3,100 to 3,200 MW in recent weeks. But in the last few days, the KSEB could not sustain the load beyond the level of 2,500 MW because of a steep drop in supply from outside the State.
According to officials in Andhra Pradesh, the State would have faced a blackout but for the automatic systems allied to the 400-kV transmission lines from the north. These transmission lines have 400-kV sub-stations at Gajuwaka near Visakhapatnam and Chandrapur in Maharashtra, which are fitted with special high voltage direct current (HVDC) facilities and other systems.
Normally, when power is supplied from any upcountry grid to any State in the southern grid, it has to be routed through one of these lines. Power reaches these sub-stations as alternating current at the frequency of the supplying grid. The HVDC and automatic systems at Chandrapur and Gajuwaka convert this into HVDC to synchronise the frequency with that of the southern grid. Once the frequency is synchronised, HVDC is re-converted into AC and supplied.
A senior official in the Karnataka Power Transmission Corporation said protection mechanisms saved the day. The Under Frequency Relay mechanism automatically sheds the load when the frequency drops due to any drastic reduction in availability of power, or when there is a demand surge. To make up for shortages, the automatic system facilitates load shedding.
Karnataka’s share of 350-400 MW from Talcher was hit during the grid collapse. This led to load shedding.
M. G. Devasahayam, a former Chairman of the Haryana State Electricity Board, said the absence of a management philosophy and less importance given to distribution and delivery efficiency were the fundamental causes of the grid collapse. “What the authorities keep harping on is more and more generation, that too only centralised, because these are highly capital-intensive and offer good scope for corruption.” The only solution is a holistic approach that combines decentralised distributed generation (off-grid anchoring on renewable energy sources), distribution and delivery modernisation, demand side management and end-use energy efficiency, he says.