The islanding scheme proposes that in event of a grid blackout, as was seen in the July 2012 outage which cut power to states in north India, Mumbai can be cut off from the grid, thus isolating it from the effects of a large outage.
However, for the scheme to work, the city needs to produce sufficient power to meet its demand.
Mumbai has an existing generation capacity of 2377 MW, distributed between Tata Power Ltd and Reliance Infrastructure Ltd. The city also receives power from state-owned Maharashtra State Power Generation Co.
The city sees a peak demand of 3350 MW, usually in the summer. The Maharashtra State Electricity Transmission Co said peak demand for power may touch 4540 MW in FY19, which implies the current power deficit of about 1742 MW in FY14 could reach 2829 MW in FY19.
All these numbers are assuming a plant load factoror capacity utilisationat 100%, which is rarely the case. MSETCL, in its document, assumed a PLF of 72%, which means at any given time, MSETCL expects 1711 MW of generation from all the utilities in Mumbai, on a conservative basis.
With the load increasing in Maharashtra and no increase in captive generation, islanding is not possible to be set up for the entire
Mumbai city, Tata Power director
Anil Sardana said in a conference held recently.
On September 2, Mumbai witnessed a widespread power outage when a 500 MW so-called Unit-5 operated by Tata Power in its Trombay station shut down due to a technical glitch. Tata Powers Unit-8 with 250 MW capacity has been offline due to a fire incident from January. The companys 500 MW Unit-6, a diesel-powered generation unit, had been on cold stand-by following procurers refusing to pay the high bills the unit generated. This meant at the time Unit-5 shut down, it reduced generation within the city by 1250 MW on a cumulative basis.
The city was facing a peak demand of 2950 MW on September 2. With a shortage of 1823 MW, the city immediately looked to import power from the grid. MSETCL officials said the increased demand congested its lines, making it impossible to meet the additional demand and major swathes of the city lost power supply. So, till FY19, the city will have to rely on importing power to meet its demand.
The transmission lines importing power to Mumbai can bear a maximum capacity of 1500 MW. While MSETCL pegs power generation in Maharashtra (including allocation from central government) to rise by 24% from FY15 to FY19 and the state (including Mumbai) will face a deficit of 135 MW in FY19 this still shows a picture of Mumbai being dependent on grid imports.
In such a scenario, it is essential to increase the capacity of transmission lines importing power to Mumbai or enhancing the existing infrastructure to carry more load.
The MSETCL document shows the company is planning a 400 KV Kharghar-Vikhroli DC line23.1 km, to increase power output to Mumbai from the national power grid. The proposal will bring reliable and cheap power to Mumbai to mitigate the shortage faced today. It states the plan has been approved by the state regulator. It expects the line to be set up by FY16.
Apart from that, MSETCL will setup a 220kV sub-station at Trombay, to enable bulk power to be brought into the Mumbai grid and to cater to the electrical demand of developing Mumbai, specially South and North Mumbai. This will reduce the loading on Kalwa Salsette and BO-BO Lines. This is necessary as there are no permissions to set up new generating plants in Mumbai.
The state-owned utility also plans to a 400 KV DC line from Dehrand in Raigad district to Nagothane (45 km) and a 400 KV DC line from Dehrand to Vikhroli (51.3 km), to evacuate power generated from the proposed Dehrand generating station to bring bulk input power to Mumbai. The completion date is estimated to be FY19.