Power grid main characteristics
In India, the high and extra-high voltage electricity transmission network, operated by POSOCO, comprises of 101,886 kilometres of power lines ((765/400/220 /132kV) EHV AC / (±500kV) HVDC). Two main physical characteristics are as follows:
The Indian Power system has a federal structure and Electricity is a concurrent subject with both Central and States having jurisdiction. The country is demarcated into five regional grids for planning and operational purposes. Out of the five regional grids, four grids viz Northern, Western, Eastern and North-Eastern regions with capacity of about 168 GW have been synchronized with one another while the remaining Southern grid (56 GW) is expected to be synchronized with the rest of the grids by 2014.
Presently, the country has total inter-regional transmission capacity of about 31,000 MW which is expected to be enhanced to about 65,000 MW by 2017. Synchronisation of all regional grids will help in optimal utilization of scarce natural resources by transfer of Power from Resource centric regions to Load centric regions.
Major incidents & preventive measures
In India, there was a major grid disturbance in Northern Region on 30th July, 2012. Northern Regional Grid load was about 36,000 MW at the time of disturbance. Subsequently, there was another grid disturbance on 31stJuly, 2012 resulting in collapse of Northern, Eastern and North-Eastern regional grids. The total load of about 48,000 MW was affected in this black out.
Ministry of Power, Government of India constituted an Enquiry Committee, to analyse the causes of the disturbances and to suggest measures to avoid recurrence of such disturbances in future. The Enquiry Committee report was submitted on 16th August, 2012. The Enquiry Committee is of the opinion that no single factor was responsible for grid disturbances and mentioned that multiple factors such as Weak Inter-regional Corridors due to multiple outages, High Loadings on Inter-regional tie-lines and inadequate response to the instructions of RLDCs led to the initiation of the Grid Disturbances on 30th & 31stJuly, 2012.
Progressive measures have been taken post disturbances in major areas like restricting the Area Control Error (ACE), mandating primary response from generators, tightening of frequency band, protection and outage planning co-ordination with all stakeholders, firming up of Defense plans at all levels, visualization and situational awareness throughout the system and ensuring reliability of supply through adequacy in all time horizons.