Alternative Grid-Tie Arrangements

Redundancies in electrical switching, protection and controls in the original designs by SEBs were eliminated and a set of eighteen standardized single line diagrams were developed for the fifty schemes. Grid tie arrangements were designed to connect the mini hydro to a nearby 11/33kV substation.
Lower Bhavani Scheme 

The powerhouse for the scheme would be located adjacent to the powerhouse of the recently commissioned 8 MW plant. The existing powerhouse is connected by a three circuit 11 kV line (each 6 km. long) to the nearby 110/11 kV substation at Bhavanisagar. Two alternative grid-tie arrangements for the proposed scheme are: 

(i) use of three new circuits of 11 kV lines to connect the scheme to the Bhavanisagar sub-station; 

(ii) linking the two powerhouses by a 200 meter long line (11 kV), installing a step-up transformer (11/110 kV) for the combined output (8+ 7 MW), and connecting by 110 kV to the Bhavanisagar sub-station. 

The extra cost of installing the 110 kV line for the second alternative could be offset by the costs of acquiring right of way for the additional 11 kV lines plus the energy losses under the first alternative. Hence further studies need to be conducted at the time of detailed design.

Brindavan Dam Scheme

The nearest sub-station is located at Belgola (110/11 kV) which is about 10 km from the powerhouse. Four circuits of 11 kV lines would be required to transfer the energy from the 10.5 MW scheme. In addition, the capacity of the Belgola sub-station would have to be expanded. The alternative would be to add a 11/110 kV step-up transformer at the powerhouse, and to connect the scheme to the Belgola sub-station with a 110 kV line. The reduction in costs due to energy losses may more than offset the increased cost of using the 110 kV line.

Maddur Canal Drop Scheme: 

The nearest sub-station to the powerhouse for the Maddur scheme is located 10 km away at Mandya. The load in the immediate vicinity of the scheme is slightly higher than 2 MW, the installed capacity at Maddur. By feeding the energy from the scheme directly into the local distribution lines, cost  as well as energy losses would be minimized.

Guntur Branch Canal Cluster: 

The cluster comprises five schemes (total capacity about 11 MW) along the canal in the Guntur District. The nearest sub-station, located near Narasaraopet which is about 16 km away from that stretch of the canal handles 11/33 kV. Energy losses are likely to be high if the schemes are connected by 11 kV lines to the sub- station. The alternative worth further evaluation would be to link all the powerhouses at one point, install a transformer to step up from 11 kV to 33 kV, and to transfer the energy at 33 kV to the sub-station.

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