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Enterprises who choose to buy emergency diesel generator sets should pay attention to these issues
June 09, 2022
The emergency diesel generator set is mainly used for the continuous working time is not long, generally it only needs to run continuously for a few hours (up to 12 hours), or only when the power supply fails and the power is cut off, the emergency diesel generator set is used for emergency use. At present, some large industrial enterprises and civil construction projects should be equipped with emergency diesel generator sets for units or projects that supply power to electrical loads. Do you know what problems should be paid attention to when choosing to buy emergency diesel generator sets?
1. Determination of the capacity of the emergency power station generator set
The rated capacity of the emergency diesel generator set is the 12h calibration capacity after atmospheric correction, and its capacity should be able to meet the total calculated load of emergency power consumption of the whole project, and according to the capacity of the generator set can meet the first-level load, the single largest capacity motor starts. Verification is required. The rated output voltage of the emergency generator is usually selected as three-phase 400V. It is not suitable to use a high-voltage generator. Individual projects with a large power load and a long transmission distance can consider using a high-voltage generator set.
2. Determination of the number of emergency power station generator sets
Most emergency power stations generally only have one emergency diesel generator set. Considering the reliability, two sets can also be selected to operate in parallel for power supply. Generally, the number of units in each emergency power station should not exceed three. When selecting multiple diesel generator sets, the generator sets should try to choose complete sets of equipment with the same model and capacity, and similar pressure regulation and speed regulation characteristics. When an emergency power station is equipped with two generator sets, the self-starting device should enable the two sets to be used as backup for each other, that is, the mains power fails. If the self-start fails, an alarm signal should be issued and the second unit should be started automatically.
3. Selection of diesel generator sets
The emergency diesel generator set should choose the diesel generator set with high speed, supercharger and low fuel consumption. Compared with the diesel generator set of the same capacity, the higher the rated speed, the lighter the weight, the smaller the volume, and the less space it occupies. It can save the construction area of the power station; the diesel engine with the supercharger has a larger capacity and a smaller volume; the diesel engine with electronic or hydraulic speed control device is selected, and the speed control performance is better; the generator should be equipped with brushless excitation or phase compound excitation. The synchronous motor of the device has reliable operation, low failure rate, and convenient maintenance. When the capacity of the single largest motor in the primary load is larger than that of the generator, the generator set with third harmonic excitation should be selected: diesel engine and generator The machine should be assembled on a public chassis with shock absorbers for installation in the power station: a muffler should be installed at the outlet of the exhaust pipe to reduce the impact of noise on the surrounding environment.
4. Control of emergency diesel generator sets
The control of emergency diesel generator set shall have fast self-starting and automatic input device. When the main power supply fails and is cut off, the emergency unit should be able to quickly self-start to restore the power supply. The allowable power-off time of the class load is from ten to several tens of seconds, which should be determined according to the specific situation. When the main power supply of an important project is cut off, the confirmation time of 3~5s should be passed first to avoid the time when the instantaneous voltage drop and the reclosing of the municipal power grid or the automatic input of the backup power supply, and then the alarm to start the emergency diesel generator set is issued. instruction. It takes a period of time from when the command is issued, the unit starts to start, and the speed rises to being able to carry the load. Generally, large and medium-sized diesel engines also need pre-lubrication and warm-up process, so that the oil pressure, oil temperature and cooling water temperature during emergency loading meet the requirements of product technical conditions. The pre-lubrication and warm-up process can be carried out in advance according to different situations. For example, when a large hotel has important foreign affairs activities, when a large mass gathering is held in a public building at night, when a hospital performs an important surgical operation, etc. The emergency power stations of some important factories or projects usually keep the emergency diesel generator set in the pre-lubricated and warm-up state, so as to start quickly in case of emergency and shorten the time of power failure as much as possible.
After the emergency unit is put into operation, in order to reduce the mechanical and current impact when the load is suddenly applied, the emergency load should preferably be increased in stages according to the time interval under the condition that the power supply requirements are met. According to the national standards, the first allowable load of automatic diesel generator sets after the successful start-up is not less than 50% of the rated load for rated power not greater than 250kW; for rated power greater than 250kW, according to product technical conditions. If the requirements for the instantaneous voltage drop and transition process are not strict, the general unit suddenly added or suddenly unloaded load should not exceed 70% of the unit's rated capacity.
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