Emergency diesel generator sets are emergency power supplies used in emergency situations or after power outages due to accidents.
Emergency diesel generator sets have two characteristics when in use:
1. Emergency use. Emergency diesel generator sets will not be in continuous operation for too long, and generally run for a few hours (≤12H).
2. Standby. Emergency generator sets are usually in a shutdown waiting state. Only when the main power supply fails and the power is cut off, the unit will start to supply emergency power load. When the main power supply returns to normal, it will switch to shutdown immediately.
The rated capacity of the emergency diesel generator set is the 12h rated capacity after atmospheric correction. Its capacity should be able to meet the total calculated load of emergency power, and it should be calibrated according to the requirements for starting a single large-capacity motor in the generator capacity load. Emergency generators generally use three-phase AC synchronous generators with a rated output voltage of 4V.
When there are multiple generator sets in standby, generally only one emergency diesel generator set is set. From the perspective of reliability, two units can also be selected for parallel power supply. The number of generator sets for emergency use is generally not suitable for 3. When multiple units are selected, the units should try to use complete sets of equipment with the same type and capacity, similar voltage and speed regulation characteristics, and the fuel used should be consistent in nature to facilitate maintenance and shared spare parts. When there are two generator sets for emergency use, the self-starting device should enable the two units to serve as backup for each other, that is, after the mains power outage is delayed, the self-starting command is issued. If the first unit fails to start three times in a row, an alarm signal should be issued and the second diesel generator should be automatically started.
Emergency diesel generators should be selected with high pressure, boost, low fuel consumption and the same capacity. The turbocharged diesel engine has a large capacity and occupies a small space; the diesel engine is equipped with electronic or hydraulic speed control equipment, which has better speed control function; the generator should be equipped with a synchronous motor with brushless excitation or phase compound excitation equipment, which is more reliable, has a low error rate, and is more convenient for maintenance and repair; when the capacity of a single air conditioner or motor in the load is large, a generator set with third harmonic excitation should be selected; the unit is installed on a common chassis with a shock absorber; a muffler should be installed at the outlet of the exhaust pipe to reduce the impact of noise on the surrounding environment.
The control of the emergency generator set should have self-starting and automatic input equipment. When the main power supply is cut off, the emergency unit should be able to start automatically and resume power supply. The load's allowable power-off time ranges from more than ten seconds to tens of seconds, which should be determined according to the specific situation. When the main power supply of an important project is cut off, it should take 3-5S to confirm the time to avoid the instantaneous voltage drop and the time when the city power grid is closed or the backup power supply is automatically put into use, and then issue the command to start the emergency generator set. It takes some time from the announcement of the command, the start of the unit, the speed increase to the full load. Generally, large and medium-sized diesel engines also need pre-lubrication and warm-up process to make the oil pressure, oil temperature and cooling water temperature meet the requirements of the factory technical conditions during emergency loading; the pre-lubrication and warm-up process can be carried out in advance according to different conditions. For example, emergency units for military communications, important foreign affairs activities of large hotels, large public activities at night in public buildings, and important surgical operations should usually be in pre-lubrication and warm-up state to start and shorten the power outage time as much as possible.
