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1. INITIATING SIGNAL FOR SCHEME. In the proposed scheme the signal is getting initiated on the basis of pole blocking signal and antecedent level of power flow at the generator terminals : Initiating the signal on the above basis has following limitations :
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1. INITIATING SIGNAL FOR SCHEME In the proposed scheme the signal is getting initiated on the basis of pole blocking signal and antecedent level of power flow at the generator terminals : Initiating the signal on the above basis has following limitations : -- Does not take care of conditions during ground return mode . -- Does not take care of situations when some power is re-routed through Gazuwaka. -- Does not take care of the situations when some power is exchanged with ER / WR under STOA transactions through Talcher-kolar, by way of displacement. Suggestion: “ The blocking of poles signal can be initiated on the basis of change in level of power flow on Talcher-kolar link or at the interconnection, rather than on the antecedent level of power flow at the generator terminals ”
2. OPERATING NORMS The scheme suggests to limit the power flow through HVDC Talcher-kolar bipole to 1700 MW or Talcher ST-II ex-bus generation, whichever is minimum. Suggestion: “Such restrictions on operating norms are not desirable as it may come in the way of optimally utilizing the above link, more particularly in the event of lower level of generation at Talcher ST-II (when one or more units are under planned /forced shut down).
3. RESTRICTION OF POWER INRUSH TO ER / WR UPTO 450 MW The following points deserve consideration on this issue: a)Situations which may lead to sudden inrush of power from SR to ER/WR are : - Tripping of HVDC Talcher-Kolar ….. upto 2000 MW - Tripping of HVDC BTB bipole at Gazuwaka ….. upto 1000 MW - Tripping of HVDC BTB bipole at Bhadravati ….. upto 1000 MW …Tripping of bipole at Gazuwaka can also lead to sudden inrush of power. No special tripping is envisaged in such conditions. b)In the recent past on two occassions there were tripping of Talcher-Kolar Bipole and power of more than 900 MW was impunged on ER/WR - on 28.04.05 at 1530 hrs. …. Power inrush to ER/WR 1200 MW - on 13.06.05 at 1812 hrs. …. Power inrush to ER/WR 900 MW ....... On both the occassions ER/WR system was able to withstand the above inrush of power.
3. RESTRICTION OF POWER INRUSH TO ER / WR UPTO 450 MW (contd..) Very shortly NR is also going to be synchronised with ER through AC links. ….Thereafter the net increase in the loading of ER/WR EHV ckts. under such conditions shall further reduce. Suggestion: “ In view of the above facts the possibility of permitting a higher level of power injection to ER/WR may please be explored.
4. TRIPPING OF THE UNITS VIS A VIS RUNBACK The following points deserve consideration in the respect of above issue: - In event of tripping of the units at Talcher ST-II, there would be loss of generation for prolonged duration (hours), even in the event of tripping of Talcher-kolar link on transient fault ( for few minutes). - As per the indication from Talcher Stage – II (NTPC), the units can safely shed generation upto 1000 MW (200 MW each on units 3 & 4 and 300 MW on units 5 & 6) in a short span of …. Seconds. Suggestion: “To the extent possible the relief by runback of the generating units would be preferable instead of tripping of the units.”