The EUL Line and substation project involved upgrade of the Nalubaale Power Plant (NPS) Bus bar and Breaker failure protection system which had been in operation since 1996 (22years) and was declared obsolete in 2011 and an upgrade of the Kiira Power Plant (KPS) Line differential protection system, which had been in operation since 2000 (17 years) and declared obsolete in 2010.
Over the recent years, the systems were maintained through constant condition monitoring and use of existing spares. However, the number of failures increased, depleting all available spares. Due to obsolescence, technical support and critical spares weren’t available off shelf for both these systems, which necessitated an upgrade of these protection schemes to the latest supported technologies.
The KPS line differential protection scheme consists of two relays per unit: Type DLN 910-F manufactured by ABB. These relays measure the current across the two ends of the transmission line, and when the differential current exceeds the set parameters, trip signals are initiated to protect the line. The scheme is particularly important for KPS line protection of the short lines running from KPS Generator transformers 11 to 15 to the NPS switchyard. The project is beneficial to ensure availability of critical spares and technical support for newly installed protection relays and increased reliability and stability of the power system, thus improving on plant health.