Significance of dispensing with surge chambers to lower the cost of hydroelectric stations: Fid-Bau Portal

Significance of dispensing with surge chambers to lower the cost of hydroelectric stations

Arshenevskii, N. N. / Trubitsyn, Yu. N.

Conclusions To reduce installation costs and construction times for diversion and dam hydroelectric stations, it is frequently possible and advisable to dispense with surge chambers.A criterion for the measures adopted in order to exclude surge chambers from a hydroelectric scheme may be the penstock constant of inertia $ T_{l} $. As a guide: for $ T_{l} $=4–6 sec, the closure time $ T_{s} $ of the guide vanes must be increased for the normal power plant installation: for $ T_{l} $=4–6 sec, the closure time $ T_{s} $ of the guide vanes must be increased for the normal power plant installation; for $ T_{l} $=6–10 sec, on increasing $ T_{s} $, changes are necessary in the design of the generator, ensuring reliability on attaining speeds of rotation approaching runaway during load shedding. Use of idle discharges enables a closure time $ T_{s} $ to be adopted, yielding an increase in rotational speed well below runaway; for $ T_{l} $>10–12 sec, it is necessary to install idle discharges.The use of idle discharges not only enables surge chambers to be dispensed with for high values of $ T_{l} $, but also provides a reduction in water hammer and consequently the design pressure in the penstocks, at the same time reducing metal consumption for manufacture.Complete calculations of the transient have to be carried out for each particular installation in the design stage, taking into account the characteristics of the turbines, regulators, and idle discharges. Only on the basis of a thorough and comprehensive analysis of the data and of the performance of the hydroelectric station on the system can the appropriate solution be adopted.Overall investigations have to be carried out for hydroelectric stations with long penstocks and with idle discharges, in order to study the features of the transients, flow instability, resonance phenornena, and vibrations in the unit and installations, particularly for heads of 150 to 300 m. Questions affecting the improvement of design discharge structures must also be resolved.