Analysis of hydraulic transition process and water hammer protection in long-distance water transmission system

Aiming at the problem of harmful hydraulic transition process due to improper adjustment of pump outlet valves during power failure and pump shutdown of long-distance water transmission pumping station system, digital simulation method is adopted to analyze the hydraulic transition process and explore different valve shutdown laws to determine the optimal valve shutdown procedure. The results show that the use of the two-stage valve shutdown law can better control the parameters such as the maximum counter-speed of the unit, the maximum water hammer pressure behind the valve and the water level fluctuation of the regulating well to within the specification requirements. Through simulation calculations and comparison of working conditions, the first stage of the shutdown procedure is proposed to be 7 s to close $95 \%$ of the valve opening, and the second stage of the complete shutdown time is 40 s. The first stage of the shutdown procedure is proposed to be 7 s to close $95 \%$ of the valve opening.