ANALYSIS OF SURGE TANK SYSTEM

Abstract

Load fluctuations in a hydroelectric power system will generally cause water hammer in the power conduits feeding water to the turbines. The pressure caused by the water hammer in the conduits could be much grater than the steady state pressure. This excessive pressure shall require prohibitively expensive designs of the conduits. The water hammer pressure can be reduced considerably by providing an artificial reservoir in the form of a surge tank as near the power station as it is economically and topographically feasible. The height of surge tank is governed by the highest possible water level that can be anticipated during the operation. The theoretical treatment of oscillation on a surge tank is made difficult on account of non-linearity of the friction term in the governing differential equation of the system. The present study has been aimed at developing a numerical model of water level oscillation in surge tank accounting for the variation of friction factor with Reynolds number. Subsequently numerical experiments were conducted on the model to study the error (in the computed water level oscillations) caused by ignoring variability of friction factor with Reynolds number. Further numerical experiments were conducted on the model to generate numerical data of maximum upsurge in response to a load rejection under varying hydraulic conditions. Subsequently the generated data were subjected to regression analysis to arrive at an approximate closed form equation for maximum upsurge accounts for the pipe friction.