Commonly used generator sets operate continuously for long periods, with significant variations in load curves. The selection of unit capacity, number, type, and control methods differ from those of emergency generator sets. (1) Capacity determination: The unit's long-term continuous output power should meet the maximum calculated load of the entire project, and the capacity of standby generator sets should be determined based on the importance of the load. The continuous output power of diesel engines is generally 0.9 times the rated power. (2) Number determination: Generally, two or more units are set to ensure continuous power supply and adapt to changes in the electrical load curve. Having more units allows adjusting the number of operating generators according to load changes, enabling diesel engines to run frequently at economic loads, reducing fuel consumption and lowering power generation costs. The optimal economic operating state of diesel engines is between 75% and 90% of rated power. To ensure continuous power supply, standby units should be considered for commonly used units. (3) Speed determination: For civilian use, high-speed units with speeds of 1000 to 1500 rpm are preferred, while low-speed units with speeds of 300 to 350 rpm are suitable as main engines for ships. (4) Voltage determination: The output voltage of generators is determined similarly to emergency generator sets, generally 400V. For projects with large power consumption and long transmission distances, high-voltage generator sets can be selected.