Hydraulic Transient
In a closed conduit, when the flow is unsteady that is the discharge at each section is varying rapidly from one instant to the next, sudden pressure changes occur inside the circuit. Such pressure changes caused by flow changes are termed as hydraulic transient.

Main Causes of Hydraulic Transient in a Hydro Powerplant: 

• Star-up and shut-down.
• Modification of operating point.
• Emergency stop.
• Out of phase synchronization during start-up.
• Earth fault.

Operational inputs for the calculation of hydraulic transients
The turbine operating characteristics provided for the assessment of hydraulic transients, will have a considerable impact on the design and cost of hydropower plant. Turbine speed and pressure regulation characteristics must be provided in accordance with the performance requirements, optimizing pressurized water system design and generator inertia.

Capability of hydro units for speed or frequency regulation of the interconnected power system cause hydraulic pressure transients in penstocks which may affect strength (wall thickness), diameter and material. Penstock and pressure water system constitutes significant cost in hydro stations.

Means for controlling pressure and frequency

• Provide additional flywheel effect
• Regulate the opening and closing rate of wicket gates
• Provide pressure regulatory valves or synchronous by-pass
• Provide surge tank

Simulation Technology
This is a complex problem and to ensure plant safety, optimize operating parameters and define the most suitable economic solution, a plant simulation model is needed to investigate all worst cases. The simulation of the dynamic behavior is usually carried out separately for the hydraulic and electrical part of the plant, allowing to determine the set of parameters related to the safety of each part. Then the control command parameters must be calculated considering the stability of operation. Several methods were developed since the end of 19th century, aiming to simulate the real behavior of the hydraulic system, being still subject of studies. Some of them are more suitable for estimating a certain desired characteristic, others for solving another part of the problem. However, undoubtedly the state-of the-art is the use of a proven specialized computer program to carry out this type of simulation.

FLOVEL’s Design and Engineering team relies on SIMSEN transient calculation software to accomplish this task. SIMSEN was developed by the EPFL (École Polytechnique Fédérale de Lausanne) and is used by most hydroelectric equipment manufacturers, universities, and consultants.

SIMSEN software is an advanced numerical tool for simulating the dynamics of power systems, with a strong capability to model entire hydropower plant, including complex hydraulic machinery, hydraulic waterways, and systems, as well as electrical machines, power electronics and the control systems.

Considering the complexity of the problem, that requires the simulation of alternatives for the same project, the use of this program allows us to quickly define the optimized solution.

About FLOVEL:

FLOVEL name has been synonymous with the hydro power sector for over four decades. FLOVEL is a full-line supplier of electromechanical equipment and services for small and medium size hydro power plants manufacturer of hydraulic turbines, valves and turnkey supplier of electro mechanical packages for hydro power projects and ranks amongst the leading players globally. FLOVEL manufacturers complete range of Pelton, Francis, Kaplan, Axial Flow turbines and Valves for hydropower projects. The strength of FLOVEL is in its ability to offer all-inclusive solutions (Electro Mechanical-Turnkey Packages).