Special Protection Scheme for bus Reactor in Transfer bus Coupler Bay

GETCO network is expanding rapidly to meet the generation as well as demand requirements in the state. Also due to non availability of gas, government policies in the benefit of RE generation and implementation of merit order dispatch, power flow pattern has changed completely in last few years and load pockets have become generation pocket also. Earlier generation pockets in Gujarat were in southern region and power was flowing towards central, western and northern region. But, now power is flowing from western region to central, southern as well as northern parts of the Gujarat.

Moreover, western and northern region is having predominant agriculture load. Hence, during non agriculture season load consumption reduces considerably. In addition to that, transmission lines connecting these regions with central Gujarat are quite long. These long lines are loaded below SIL resulting in generation of excess reactive power causing high voltage at 400KV Buses in these areas. Because of Over Voltage, many 400KV Lines are required to be switched off to maintain voltage within acceptable limits. This, in turn, is jeopardizing grid availability and security.

To overcome Over Voltage, GETCO found the need of Reactors at 400KV strategic location (7 Places) based on system study. But, out of seven, four locations have the space constraint for providing Reactor bay. After brain storming, it was decided to utilize TBC bay as Bus Reactor bay by providing Bus reactor in Transfer bus coupler bay. The main consideration behind this decision was utilization of TBC bay on very few occasions in a year. On finalization of this modality, there are challenges regarding (i) Bus Reactor arrangement in TBC Bay, (ii) Control & Interlocking philosophies, (iii) Protection philosophies, (iv) Whether to utilize TBC Bay as TBC as well as Bus Reactor or either of the two. Challenges become harder as each substation has different Make and Type of TBC Panels, Different TBC interface schemes and Different Bus bar schemes. Also there are challenges regarding which type of panel is to be considered for Reactor.

The above scheme has really helped GETCO in mitigating Over Voltage problems substantiously and there-by strengthening security of grid. This paper shares the knowledge of implementing the scheme, issues & challenges faced and benefits achieved.