Abstract Recently, the expansion in power system capacities leads to the development of large-scale steam turbine generator units. As a result, a fault on the power system may induce large fault current and give rise to serious torque vibrations on turbine shafts and blades, which ought to be improved in order for the reliable operation of a turbine-generator system. In the thesis, countermeasures are proposed from electrical viewing-point and from mechanical viewing-point respectively. Based on electrical viewing-point, the apparatus in the generator stator side and in the rotor side respectively is applied to suppress the induced disturbing source. The high temperature superconductive fault current limiter bank introduces a large normal-state resistance to restrict the dc component of stator fault current. The choke coil acts as a low pass filter to restrict the system-frequency component of field fault current. Both of them lead to the reduction in electromagnetic torque of system-frequency and effectively improve the vibrating behavior of blades. Based on mechanical viewing-point, it is found from the electromechanical analysis that the Generator/LP-Turbine shaft stiffness and the Generator rotor inertia constant determine the responses of all turbine blades. Once the stiffness on this shaft section is reduced by replacing the rigid shaft coupling with a flexible one or the inertia constant is augmented by a system-frequency mechanical filter, the blades become intrinsically less responsive to electrical disturbances. As a result, the blades will bear less stress impact and can be designed with smaller safety factor. On the other hand, LP-turbine long blades operated in corrosive environment and underwent the statistical stress impact due to randomly distributed negative sequence current is studied also. In such situation, the blades may be subjected to corrosion fatigue and the long term effects of power system unbalance may become the cause of fatigue damage on blades though the negative sequence current is still within the limitation of generator thermo-rating. As a result, turbine blades are possibly unprotected by traditional system unbalance protection scheme. Therefore, it will depend on the operating environments and the blade materials whether such long-term stress can be neglected or not. If there is the potential of blade damage, one has to reconsider the I2 protection settings and rearrange the load distribution to limit the system unbalance.

Aim of my work is influence of high level breeding of Euroasian perch on quality of water and operation of mechanicle drum filter and fluized bed biofilter. Euroasian perch is reared in recirculating aquaculture systeme. Fish were devide into six groups in dependence on their body weight. Groups of fish with avarage start weight (g) {$\pm$} SD; biomass (kg) 232,9 {$\pm$} 10,0; 15,14 (I), 196,4 {$\pm$} 8,1; 15,32 (II), 139,8 {$\pm$} 6,1; 15,10 (III), 102,4 {$\pm$} 5,5; 15,06 (IV), 59,4 {$\pm$} 5,5; 15,04 (V), 37,7 {$\pm$} 7,5; 15,00 (VI) were put into plastic tank (600l). Three measurement was with fed fish and three measurement with food-deprived fish. Fed day was organised like feeding period (light phase) 12 hours and 12 hours non-feeding period (dark phase). First part of my project was about impact mechanicle filtration to remove solids from water. Mechanical filter can keep the water quality on perfect level for fish farming. Second part was about evaluation of nitrifying biologickle filters. Biologicle filtration was did her function well, because levels of amonia, nitrite and nitrate were keep on optimum values. Third part of my project was about measurement of oxygen consumption and amonia excretion. Was observed significant diurnal changes of oxygen consumption and amonia excretion for fed fish. For food-deprived fish was observed significant diurnal changes of oxygen consuption. Changes of amonia excretion were not significant.