Fixing approximate powerhouse dimensions

Dimensioning of a powerhouse

The size of the powerhouse is determined by the equipment, its erection, maintenance and operation needs. The process:

1. Fix the number, type and rating of units and their principal sizes (runner diameter $D$, spiral casing, generator and draft tube dimensions) from manufacturers' data or empirical relations.
2. Fix the unit spacing (bay width) from the spiral casing and generator clearances, usually about 3 to 4 $D$.
3. Add the erection (service) bay and end clearances to get the length.
4. Fix the breadth from the width of the generator/turbine section plus galleries and auxiliary side.
5. Fix the height from the draft tube floor up to the crane rail and roof.
6. Check the levels against tailwater flood level and the turbine setting.
7. Check the layout for access, safety and expansion, and balance cost and operation.

Functional requirements fixing the dimensions

• Hydraulic and mechanical: sizes of spiral casing, draft tube, valves and runner; the setting level of the turbine (cavitation); minimum water cover and tailwater level.
• Generation: generator floor space, clearance for rotor removal, bearings and exciters.
• Erection and maintenance: an erection bay large enough for the heaviest part (the rotor or runner) and space for dismantling a unit; crane capacity and hook height to lift the largest piece over equipment.
• Control and switching: control room, switchgear, batteries and cable galleries close to the machines.
• Auxiliary services: cooling water, drainage, dewatering, compressed air, oil handling, ventilation and fire protection.
• Access and safety: corridors, stairs, emergency exits, loading/unloading space for trucks, and workshops.
• Structural: loads from machines and crane, vibration, flood protection and foundation conditions.
• Future expansion: extra bay for additional units.