Performance Improvement of Hydro Electric Power Plant using Electrical/Dynamic Braking System (Case study:- Gilgel Gibe II Hydro Electric Power Plant)

Abstract

Gilgel Gibe II Hydroelectric power plant is not operated as a base load power plant like Beles and Genale-Dawa III hydroelectric power plant rather it operates as a peak load power plants. Therefore, depending on the system load and other factor all the four units can start and stop based on demand load hence the main problem of the plant is all the unit needs 58 min each for any daily frequent stopping of generator set. Therefore, the primary aim of this thesis is to model Gilgel Gibe II Hydro Electric Power Plant units when the generator needs daily frequent stopping of generator set and tripped off due to normal or emergency condition, bring the machine immediately to the standstill condition within five minutes. To bring the machine immediately to the standstill condition within five minutes, extra braking force will be apply electrically operated Electrical/Dynamic braking system integrating with existing pneumatically operated mechanical barker system. Dynamic/Electrical braking system is applied to the plant generators to bring the machine immediately to the standstill condition by providing extra braking force. This force is an additional braking force in which the unit excitation system is energized by a separate auxiliary supply and DC field supply to the unit rotor. As a result the generator stator is shorted by the Isolator/disconnector providing in the dynamic braking cubicle. The tapping of this cubicle is taken from the unit bus duct terminals & is generally kept near to the generator bus duct on the generator floor. As a result by applying Dynamic/Electrical braking system the power plant becomes less restoration time due to this the plant can generate optimum output power (Annual Energy production), increase its plant availability and decrease restoring time of the plant.