University of Tasmania, Australia

Unsteady operation of hydro-electric turbines

The ability to rapidly start hydroelectric turbines and related equipment is of significant value to electricity utilities as it provides the opportunity to sell capacity to the National Electricity Market in case of sudden increases in load or reduction in generation capacity. In addition to this, the integration of wind power into the network increases the likelihood for rapid changes in generation to occur.

Most hydroelectric units have the ability to operate in what is known as tail water depression (TWD) mode. In TWD mode air is forced into the runner cavity such that the runner is able to spin at synchronous speed in air rather than water. Operation in TWD mode enables very rapid machine start-up and is extremely well suited to Tasmanian conditions as it also increases system inertia, provides reactive power control and eliminates the need to operate at low efficiency.

On start up, the introduction of water to the turbine causes an extremely complex flow, and a significant power dip (requirement for power to be supplied to continue to spin the turbine) has been observed to occur for several seconds while the turbine water flow is established.

The purpose of this research is to develop an understanding of the unsteady flow mechanisms through model testing, field testing and computational fluid dynamics. This understanding will then be applied to developing control or operational methods to reduce the power dip and facilitate more rapid turbine loading.