The Islanding Scheme for Delhi during grid disturbances has been announced.
Speaking at a press meet where Delhi Chief Minister Sheila Dikshit was also present, Union Power Minister Veerappa Moily stated that as per request made by Dikshit, Union Power Ministry has completed all formalities for Islanding Delhi during grid disturbances.
The task which was to be completed within three months have been accomplished much earlier.
Dikshit while conveying her gratitude to Moily stated that there is a dire need to provide uninterrupted power supply in the Capital City as it is home to the Union Government, all important installations, embassies and all agencies providing essential services. Dikshit added that our government demanded Islanding on the lines of Islanding facilities in Mumbai, the Union Ministry after due consultations with all concerned has, in fact, agreed to put in place a better Islanding technology which would also be upgraded phase-wise.
It would be upgraded to make it operational as per intelligent mechanism. It is expected that the real operation of Islanding would come into force within next two months. Delhi Power Minister Haroon Yusuf, the Chief Secretary P.K. Tripathi and Pr.Secretary Power Shakti Sinha were also present on this occasion.
Subsequent to two major grid disturbances during July 2012, in a meeting taken by Union Minister of Power with the Chief Minister/Power Minister of Northern Region States on 6th August, 2012, It was agreed that States would prepare their islanding schemes in consultation with CEA, NRPC and PGCIL within next three months and ensure their implementation within next six months.
The Enquiry Committee constituted by MoP, GOI to look into the detailed causes of these disturbances has also recommended that efforts should be made for formation of electrical islands in case of imminent grid disturbance. The Study Group, constituted by CEA, for this purpose, deliberated on finer aspects of islanding and also interacted with experts from Tata Power, Mumbai and CESC, Kolkata to share their experiences of islanding scheme in respective areas,. Based on these deliberations, DTL submitted its report, on Delhi islanding scheme, to CEA.
The proposed islanding scheme for Delhi envisages to isolate Delhi System and continue to supply power to essential services like Delhi Metro Rail, Water Treatment load, Indian Railways Load, hospitals and other critical areas etc. This scheme will also help to extend start up supply to generating stations in adjoining areas to facilitate early restoration of the grid.
The proposed islanding scheme envisages that when grid disturbance is imminent, four islands of Delhi’s power system, capable of meeting essential loads will be created. Delhi SLDC will have overall responsibility of operation of the islanded system.
The power network of Delhi is far more complex than Tata system of Mumbai and CESC system of Kolkata which makes islanding scheme for Delhi more complicated. Keeping in view the complexity of the Delhi power network, creation and survival of the islands some additional features like development of intelligent system for centralized decision making, augmentation of generation within Delhi, maintaining dual source of supply to essential loads, training of system operators, etc. are proposed to be taken up under this scheme.
During the grid disturbances, when the system frequency starts falling, cascade tripping of generating units and transmission lines may occur leading to possible collapse of the entire grid. For such cases first line of defense mechanism is to shed load automatically through Under Frequency Relays (UFRSs) and rate of change of frequency (DF/DT) relays to save the grid. If this does not work and total collapse of the grid is eminent, smaller power sub-systems may be created having group of generating stations and matching loads.
Each sub-system becomes a sustainable island and this defense scheme is named as islanding scheme. Apart from supply of identified essential loads, these islands are helpful in faster restoration of grid from grid disturbance.
The islanding scheme for Delhi has been envisaged to meet the following objectives:
To isolate Delhi’s power system from the regional grid when grid disturbance is imminent and after isolation, continue to meet at least emergency loads of essential services Delhi Metro Rail, Water treatment load, Indian Railways Load and hospitals, Present quantum of essential load spread across various distribution companies of Delhi is about 930 MW and to extend start up supply to generating stations in adjoining area to facilitate early restoration.
The islanding scheme envisages that fall of frequency to 47.9 Hz will be taken as indication that grid disturbance is imminent and islanding will initiated. Four (4) islands of Delhi’s power system, viz. Dabri –Jajjhar-Pragati (part), Bawana CCGT, BTPS- Pragati (part) and Rithala CCGT, which together would generate about 4200 MW and would be capable of meeting about 3400 MW of load, during peak conditions, have been planned.
The scheme is designed so as to involve minimum control agencies, for better coordination during emergency and with clear control responsibility.
During the islanded operation, Delhi SLDC will have overall responsibility of operation of the islanded systems. All the generating companies, distribution licensees, DTL and POWERGRID sub-stations which are part of the islands, will comply with advice of Delhi SLDC. The latter will be in regular communication with NRLDC.
Caption: Dikshit alongwith Moily announces the islanding scheme for Delhi during grid disturbances