Units 9 and 10

The objective of the current extension project is thus to add 200 MW generating capacity, raising the capacity of Mangla power station to 1000 MW. This will be the fourth and final extension at Mangla; the potential of each tunnel will then be fully exploited.

Feasibility studies had originally been carried out for raising the heights of the dams by 12.2 m which would give maximum storage capacity of 11.84×10⁹ m³ live storage_; However, recent studies have shown that the cost benefits in terms of the additional water for irrigation and power generation do not justify the additional cost of heightening the dams at this stage.

Installation of units 9 and 10 on tunnel 5 without raising the dam has been found to be justifiable on the following operating basis:

• peaking duty for 4 h during the system peak demand period; and,

• operation at full capacity for 24 h per day during the months of May to August.

Operation of all ten units at Mangla during peak hours will require storage of water during

non-peak times of the day. It will then be released in large quantities in a short time during peak demand hours. This sharp fluctuation in water releases would result in surges downstream, causing undesirable fluctuations in the withdrawal head of the connected irrigation canals (Lower Jhelum canal and Rasul Qadirabad link canal) emanating from the Rasul barrage, about 75 km downstream of Mangla dam. Studies proved the reservoir capacity of Rasul barrage to be sufficient for re-regulation of water supplies, but some modifications at Rasul were necessary. These modifications involved remodelling of the upstream earth embankment and stone pitching of the upstream, training works from the high automating operation of the head gates for both the canals was also found to be necessary. These work are being carried out prior to commissioning units 9 and 10 at Mangla.

Engineering works:

The civil engineering work consists of:

• extension of the existing power station to accommodate the two additional 100 MW units;

• concrete encasement and grouting of the tunnel's steel lining and bifurcation; and, completion of draft tubes;

• provision of a loading buy next to unit 10, and аn administration building;

• erection of a temporary cofferdam and draft tube gates;

• extension of switchyard works;

• construction of residential and non-residential buildings.

The units are rated at 100 MW each at the rated head of 90 m. However, up to 20 per cent more output can be achieved at heads higher than the rated head.

Дата добавления: 2015-11-16