The Sikkim government's failure to complete transmission line from Teesta-III hydro power station to Kishanganj substation has resulted in Rs 6 crore loss per day, All India Power Engineers' Federation said today. 

"The failure of Sikkim government to complete and commission the 400 kv transmission line from Teesta-III hydro power station to 400 kv grid substation Kishanganj (Bihar) has caused serious transmission bottleneck in Sikkim, resulting in loss of over 500 MW power continuously with financial impact of Rs 6 crore per day," an AIPEF white paper on the transmission line said. 

According to the paper, power generated from 6 hydro power stations in Sikkim is pooled at 400 kv (kilovolt) grid substation Rangpo, owned by Power Grid Corporation. This pooled power is transmitted from Rangpo to 400 kv grid substation at Binaguri (near Siliguri) about 150 km away in West Bengal. From Binaguri this hydro power is dispersed over eastern grid which in turn is linked with nor with northern, southern and western grid of the country. 

The 6 hydro stations which are connected to Rangpo are as NHPC Teesta-V (510 mw, Chuzachen (99 mw), Jorethang (96 mw), Teesta-III ( 1200 mw, with over load capacity of 1320 mw), Dikchu (96 mw), and Tashiding ( 97 mw). 

The combined capacity of these hydro stations is 2,098 MW. However, the only transmission line to evacuate this power to eastern grid is the 400 kV double circuit line from Rangpo to Binaguri. Since this lin has twin moose conductor, its capacity is about 1,700 mw (megawatt). This line was originally envisaged for Teesta V station of 510 mw, while power from Teesta III was to be evacuated to Kishanganj. 

During summer and monsoon, all these hydro power houses get sufficient water availability and operate at 100 per cent capacity on 24x7 basis. But, due to the limitation of Rangpo - Binaguri line with capacity 1,700 MW, the hydro stations of 2,098 mw have to be restricted to about 1,700 mw  and thereby have to be backed down to the extent of 398 MW, the paper said. 
Since, the Teesta-III power station of 1,200 mw has in-built overload capacity of 10 per cent and is designed for continuous rating of 1,320 mw, the enhanced generation capacity of the 6 power station becomes 2,098 plus 120 at 2,218 MW. With this capacity available, the quantum of backing down necessary to limit the line loading to 1,700 MW then becomes 518 MW, it added. 

In the summer/monsoon period of 2017, due to transmission constraint resulting from non-commissioning of Kishanganj  line, the Teesta-III power station had to be backed down and there was loss of energy to the extent of 1,462 MU (million units). This resulted in financial loss to TUL (now a Sikkim government company) of the order of Rs 500 crore, the paper noted. 

The All India Power Engineers' Federation (AIPEF) stressed that Central government should actively intervene so as to minimise further delay in commissioning of Teesta III- Kishanganj 400 kv line and minimize further loss at rate of Rs 6  crore per day. 

So far, the energy loss due to transmission bottleneck caused by the delay is of the same order as the capital cost of the 400 kv line, it added.