At Nalubaale Power Station (NPS) there are various Direct Current (DC) systems that are used in operation of the plant. They are mainly used for Protection, Control circuits, Stand by power supplies, Uninterruptible Power Supplies, Alarms and Communication. Among the DC systems are 110v and 50v battery systems. Each system consists of deep cycle flooded lead acid batteries, battery chargers and distribution boards.
The manufacturer’s rated useful life for the battery banks and chargers being 10 to 15 years, they had exceeded their useful lifetime hence the battery charger systems had to be replaced at NPS 50Vdc battery chargers and 110Vdc battery chargers in the 33kV plant house (2) and 110Vdc battery chargers in the 132kV plant house. A total of six battery chargers were replaced.
The 50Vdc Battery chargers were commissioned on 11th September 1990 and were therefore in service for 26 years. The formerly existing 110Vdc Battery chargers in the NPS 33kV planthouse were commissioned on 13th January 2004. They had therefore been in service for 12 years.
Battery chargers are very important during periods of stable AC supply to convert AC power to DC and charge the battery banks. The chargers supply critical DC loads like relays and switch gear. In case of interruptions in main supply, the battery chargers go off and battery cells discharge to supply the critical DC loads. This ensures continuous and reliable supply of DC power especially to protective devices.
The following are the benefits of replacing the battery chargers; -
- Guaranteed spare parts and technical support in case of equipment failure.
- Improved performance of battery chargers and guaranteed supply to critical DC loads.
- Elimination of risks associated with explosions resulting from charger failures which will damage nearby equipment.
- Improved safety of personnel working on the battery charger systems and nearby equipment.
- Reduction in maintenance costs quantified by limited system failures.