Diesel generator sets are needed in many places. Normally, these facilities can be powered by the city's electrical grid. However, due to natural disasters such as earthquakes and typhoons, or human factors, the city power may not be sufficient, leading to power outages. In such cases, pre-installed backup generator sets should quickly start up and maintain continuous operation to ensure a steady power supply for critical engineering loads. These backup generator sets also fall under the category of common power generation units. Common power generation units have longer continuous operating times, greater fluctuations in load curves, and require different selection criteria for capacity, number of units, and types, as well as control methods compared to emergency units.

1. Determining the capacity of commonly used diesel generator sets; the output power of the set should be able to meet the calculated load of the entire project for long-term continuous operation, and the capacity of the standby generator set should be determined based on the importance of the load. The continuous output power of the diesel engine is generally 0.9 times the rated power.

2. Determination of the number of common diesel generator sets; the number of common diesel generator sets is typically set at two or more to ensure continuous power supply and adapt to changes in the electrical load curve. With more sets, the number of generators in operation can be adjusted according to the electrical load variations, allowing diesel engines to operate frequently under economic load conditions, thereby reducing fuel consumption rates and lowering power generation costs. The economic operating state of the diesel engine is between 75% to 90% of the rated power. To ensure continuous power supply, the common generator sets themselves should consider having standby sets in place. This ensures that during scheduled maintenance or shutdown for inspection, the power generation sets can still meet the continuous power supply requirements for critical electrical loads.

3. Determination of the speed of commonly used diesel generator sets; to reduce wear and extend the service life of the generator sets, it is advisable to choose medium and low-speed sets with a rated speed not exceeding 1000 r/min for commonly used generator sets. Their standby sets can be medium and high-speed sets. Generator sets of the same power station should be of the same type and capacity to facilitate the use of the same spare parts and make maintenance and management easier. For projects with significant load changes, sets of the same series but different capacities can also be chosen. The determination of the generator's rated output voltage is the same as for emergency generator sets, generally 400V, but for projects with high electricity consumption and long transmission distances, high-voltage generator sets can be selected.

4. Control of commonly used diesel generator sets; General units should be designed for parallel operation to simplify the main distribution circuit, ensuring uninterrupted power supply during start-up, shutdown, and switching operations by means of paralleling, load transfer, and unit switching. The units should be equipped with measurement and control devices, and the speed and excitation control devices should meet the requirements for parallel operation. For backup generator sets supplying critical loads, it is advisable to choose automated diesel generator sets that can quickly and automatically start up following an external power failure to restore power to critical loads. The operation of diesel generators can produce significant noise in the engine room, making automated units easier to convert into enclosed operation and automated monitoring systems. When the generator set is operating normally, operators do not need to enter the engine room and can monitor the diesel generator set from the control room.