The Talcher - Kolar HVDC link is a high capacity link which transfers power from Talcher in the Eastern Region to Kolar in the Southern Region. In case the link trips, the W-E-NE Region is left with surplus power. Most of the surplus power rushes towards the western region (which has a large load) through relatively weak AC tie lines. The ensuing power swings (relative motion between generators) are not stable and the system separates into two regions due to loss of synchronism.

Therefore, in order to prevent ER-WR system separation, the following emergency scheme was concieved:

In case due to an unexpected contingency, the heavily loaded HVDC link trips, then a few generators at Talcher are also tripped immediately. This ensures that the W-E-NER system is not left with too much surplus power.

Note that the other asynchronous links to the Southern Region (e.g. the one at Gazuwaka) are of limited capacity and cannot suddenly push the excess power to the Southern Region unless they are lightly loaded. Moreover power flow through these links is regulated. Therefore, power can be ramped slowly by manual intervention. However, a strategy specifically suited to deal with this situation can be concieved.

The proposed plan for synchronous operation of NR and WR-ER-NER brings out interesting questions:

What will be the role of the existing back-to-back HVDC links (which asynchronously interconnect the two systems at present), when NR and WR-ER-NER systems are synchronized ?

Can the back-to-back HVDC links regulate the total power exchange between the two regions once they are synchronized ?