Surge Shaft Stability with Pumped‐Storage Schemes

Abstract

The stability of surge tanks is investigated taking into account the friction losses in the pipe, surge tank and the junction losses. Three surge shaft stability problems are investigated for a surge shaft layout. Pump operation is analyzed to establish the influence of a shaft on the surge behavior of pumps. The influence of penstock and junction losses on shaft stability in turbine operation are examined. The stability of tailrace surge shafts in turbine operation is analyzed. All the results obtained are for small amplitude oscillations and any increases in the required shaft area for stability are in addition to those which may be required due to the effect of large amplitude (nonlinear) oscillations. The method of incorporating the junction losses (i.e., approximating them by their steady state values) is valid for a small amplitude study but for large surge amplitudes it will generally be necessary to take account of the variations of the loss coefficients with the flow ratios at the junction.