Avbördningskapacitet för Traryd kraftverk
en modellstudie vid dimensionerande flöde
Sydkraft Vattenkraft AB owns and operates the Traryd hydropower plant, located in the river Lagan in the southern part of Sweden. The gravity dam is classed according to RIDAS guidelines (Hydropower Industry Dam Safety Guidelines) as a class 1B dam. This means that the dam must discharge a class 1-flow which has a return period of 10 000 years. The inflow into the dam has been calculated in an earlier report to 495 m3/s, with a waterline at an elevation of 126, 3 meters above sea level. The gravity dam has a discharge system with two rectangular weirs, which results in a smaller discharge than the necessary 495 m3/s. The discharge capacity is normally calculated with theoretical relationships, which include discharge coefficients for various conditions. Characteristic values are given in the literature. For better estimations numerical simulations or laboratory flume experiments can be carried out. After some considerations, it was decided to perform a laboratory model study in scale 1:66. The modelling was initially used to estimate the discharge capacity and secondly, to test modifications of the weir inflow. The experimental modelling resulted in a discharge capacity of 452 ± 14 m3/s when the surface level was 126, 3 meter above sea level. This can be compared to the results of the theoretical calculation 462 m3/s. Furthermore, including the use of a reconstructed old weir increased the discharge capacity to 509 ± 20 m3/s.