Limit revised for inter-regional power transmission
Grid collapse could have been caused due to heavy flow of power on single circuit
Manish Sirhindi/TNS
Ambala, August 3
Even as the northern states are blaming each other for the recent grid collapses which caused complete blackouts in many northern and eastern states, the National Load Dispatch Centre (NLDC) has hinted that it might have been caused due to a heavy flow of power on a single circuit during the inter-regional power transmission.
The NLDC has revised the limits of inter-regional power transmission from 765-KV and 400-KV transmission lines in view of the recent grid failures.
The NLDC has pointed out that in the cases of both grid failures, there was a heavy power flow on the 400-KV Bina-Gwalior-Agra single circuit section, crossing 1000 MW on the single circuit available.
The 765-KV transmission line was being operated at 400 KV. The second circuit of 400-KV Bina-Gwalior-Agra line was under outage since July 28 as it was being upgraded to 765 KV. A grid failure was averted earlier at 3.10 pm on July 29 under similar conditions. The grids had failed on July 30 at 2.32 am and again on July 31 at 1 pm.
A senior power sector expert said that since the upgradation of the 400-KV Bina-Agra transmission line was planned work, it should have been taken up during the lean period. It was known that the power load in the northern region was at its peak during the paddy season. Moreover, the demand for power had also shot up due to poor monsoon.
Meanwhile, the NLDC in consultation with Central Electricity Authority and CTU has worked out the Short Term Open Access (STOA) approvals to be given by Regional Load Dispatch Centres (RLDC). Further, it was worked out how during an emergency RLDCs would take action necessary to ensure system security, including curtailment of transactions.
The available margin for short-term open access from the western grid to northern grid through the 400-KV Bina-Gwalior-Agra line has been fixed at 790 MW. Similarly, the power transfer from the eastern grid to northern grid has been fixed at 2,492 MW through the 400-KV Kahalgoan-Biharsharief transmission lines. Similar power transfer limits have been revised for other inter-regional power transfers also.
Power experts said it was unlikely that overdrawals could have caused the grid failure as the frequency of the gird during the first collapse was 50.46Hz which was within the permissible limit and during the second collapse, the frequency was 49.7Hz.