Emergency Diesel generator sets are primarily used in critical locations. In emergencies, accidents, or momentary power outages, they can quickly restore power and extend the duration of power supply. These are considered primary loads. For equipment, instruments, and computer systems with stringent power outage requirements, batteries or an uninterruptible power supply (UPS) are required in addition to the generator set.
Emergency Diesel generator sets have two key operational characteristics: First, they are primarily used for emergency situations and typically operate for a short period of time, typically only a few hours (less than 12 hours). Second, they serve primarily as backup equipment. Emergency generator sets are typically in standby mode. They can only begin operating and supply emergency loads after a complete main power failure. Once the main power is restored, they immediately switch to standby mode.
1) Determine the generator capacity of the emergency diesel generator set.
The rated capacity of the emergency diesel generator set is the 12-hour rated capacity after atmospheric correction. It should be able to meet the calculated total emergency power load and be verified by ensuring that the generator capacity can meet the requirements for starting the largest single motor in the primary load. Emergency generators typically use three-phase brushless AC synchronous generators with a rated output voltage of 400 volts.
2) Determine the Number of Emergency Diesel Generator Sets
Depending on the emergency load capacity, only one emergency diesel generator set is typically installed, but two or more units can be operated in parallel. Advances in parallel technology have resulted in over 20 parallel diesel generator sets being used for emergency backup power in data centers. When selecting multiple diesel generator sets, consider using complete sets of the same model and capacity, with similar voltage and speed regulation characteristics. The fuel properties used should also be consistent to facilitate operation, maintenance, and spare parts sharing. When two emergency backup generator sets are used, the automatic start device should ensure that the two units provide backup for each other. After a delayed confirmation, the system will issue an automatic start command. If the first unit fails to automatically start three times in a row, an alarm signal will be issued, and the second unit will be automatically started.
3) Selecting Emergency Diesel Generator Sets
Emergency generator sets should be high-speed, supercharged, low-fuel-consumption, highly reliable, and of the same capacity. High-speed supercharged diesel engines offer high power output and occupy a small space. The diesel engine should be equipped with an electronic speed controller for excellent speed regulation. The generator should be a brushless excitation synchronous generator.
4) Management and Control of Emergency Diesel Generator Sets
The control system of the emergency diesel generator set should have fast start-up and automatic switchover capabilities. In the event of a main power failure, the emergency generator set should be able to quickly start and restore power. The allowable power outage time for primary load ranges from ten to several dozen seconds, depending on the equipment. In the event of a main power failure in a critical project, a confirmation period of 3-58 seconds should be allowed before issuing the command to start the emergency generator set to avoid transient voltage fluctuations and grid shutdown or automatic switching of the backup power supply. From the time the command is issued, the unit will require a certain amount of time to start and reach full load. Generally, large and medium-sized diesel engines require pre-lubrication and heating to ensure that the oil pressure, oil temperature, and cooling water temperature during emergency loading meet the product specifications. Pre-lubrication and heating can be performed in advance depending on the specific situation. This ensures that the unit is always pre-lubricated and heated, enabling rapid start-up at any time and minimizing the power outage time.
After the emergency diesel generator set is put into operation, it is recommended to gradually increase the emergency load, preferably at intervals, to reduce the mechanical and current shock caused by a sudden increase in load. After the automatic diesel generator set is successfully started, the initial allowable load is as follows: for generator sets rated less than 250kW, the initial allowable load must not be less than 50% of the rated load; for generator sets rated greater than 250kW, the relevant product specifications must be followed. If the requirements for transient voltage drop and transient behavior are not particularly stringent, the sudden or increased load of the generator set should generally not exceed 70% of its rated capacity.
