Substation Up-Rating Challenges and Solutions in a Live Hydro Plant Environment

(RMU) of a 4 x 36 MW run-of-river hydroelectric project commissioned in the early 1980s.

The RMU programme increased the installed capacity from 144 MW to 156 MW, necessitating significant upgrades to the electrical, protection, and control systems, with particular emphasis on the 132-kV switchyard to accommodate a higher short circuit rating.

The existing substation configuration, characterised by a non-segregated flexible conductor busbar arrangement integrating generator transformer and line bays, posed considerable challenges for modernization under live operating conditions. The project scope included redesigning the busbar scheme, replacing obsolete switchgear, adding a new transformer bay, and implementing an IEC 61850-based protection and SAS using numerical relays [2]. A phased, bay-wise execution philosophy was adopted to execute dismantling, erection, testing, and commissioning activities while ensuring uninterrupted generation [4].

The paper outlines the engineering approach, installation methodology, safety checkpoints, and interface management between civil, electrical, and auxiliary systems. It also highlights key lessons learned from executing complex brownfield substation upgrades without prolonged outages, offering valuable insights for utilities and system operators undertaking similar refurbishment projects.