The main factors that should be considered when selecting a unit are mechanical and electrical performance, the purpose of the unit, the capacity and variation range of the load and the automation function.
The purpose of (1) unit. Because diesel generator sets can be used in three situations: common use, standby and emergency. Therefore, different uses have different requirements for diesel generator sets.
(2) load capacity. The load capacity and load variation range should be selected according to different purposes, and the single machine capacity and standby diesel generator capacity should be determined.
(3) Environmental conditions for unit operation (mainly referring to altitude and climate conditions)
(4) Selection of diesel generator
(5) Selection of generator and excitation mode
(6) Selection of automation function of diesel generator
Second, the diesel generator set procurement standards
Twenty-four performance indicators specified in the Detailed Rules for the Implementation of Quality Certification and Testing of Communication Diesel Generator Sets:
1. Appearance requirements
(1) The overall dimensions, installation dimensions and connection dimensions of the diesel generator set meet the factory product drawings approved by the specified procedures.
(2) The welding of the unit shall be firm, the weld shall be uniform, and there shall be no defects such as penetration, undercut, slag inclusion and blowhole, and the welding slag flux shall be removed; The paint film should be uniform, without obvious cracks and shedding; The coating should be smooth, without leakage and corrosion; Fasteners of the unit shall not be loose.
(3) The electrical installation of the diesel generator shall conform to the circuit diagram, and the joints of each wire of the unit shall have obvious signs that it is not easy to fall off.
(4) The diesel generator shall have terminals with good grounding.
(5) The logo of diesel generator is complete.
2. Insulation resistance and insulation strength
(1) insulation resistance: the insulation resistance between each independent circuit and the ground shall be greater than 2M.
(2) Insulation strength: Each independent electrical loop of the unit should be able to withstand the AC test voltage between the ground and the loop, and there should be no breakdown or flicker.
Loop voltage test voltage
& lt100V 750V
≥100V1440V
3. Phase sequence requirements. The phase sequence of control panel terminals of diesel generator set should be arranged from left to right or from top to bottom when viewed from the front of the control panel.
4. Requirements for diesel generator to keep ready for operation. The unit shall be equipped with a heating device to ensure that the oil temperature and cooling medium temperature are not lower than 15℃ during emergency start-up and rapid loading.
5. Reliability check of automatic power start and automatic stop.
(1) Diesel power generation shall be able to start automatically after receiving the start instruction of automatic control or remote control.
(2) When the unit fails for the third time after automatic start-up, a start-up failure signal shall be issued; When there is a standby unit, the program startup system should be able to automatically transfer the startup instruction to another standby unit.
(3) The time from the automatic start instruction to the power supply to the load shall not exceed 3min.
(4) After the diesel generator is automatically started successfully, the initial load shall not be less than 50% of the rated load.
(5) The unit shall be able to stop automatically after receiving the stop instruction of automatic control or remote control; For standby units used in cooperation with commercial power grid, when the power grid returns to normal, diesel generators should be able to automatically switch or automatically stop, and the shutdown mode and shutdown delay time should meet the requirements of product technical conditions.
6, automatic startup success rate. The success rate of automatic startup is not less than 99%.
7, no-load voltage setting range requirements. The no-load voltage setting range of the unit shall not be less than 95%- 105% of the rated voltage.
8. Automatic replenishment function requirements. The device shall be capable of automatically charging the starting battery.
9, automatic protection function requirements. The unit should have the protection of open phase, short circuit (not more than 250KW), overcurrent (not more than 250KW), overspeed, high water temperature in the water tank and low oil pressure.
10, sine distortion rate of line voltage waveform. Sinusoidal distortion rate of line voltage waveform under no-load calibration voltage and calibration frequency
1 1, voltage steady-state regulation rate
≤250 kw & gt； 250 kw
3% 2%
12, voltage transient regulation rate
≤250 kw & gt； 250 kw
20% 15%
13, voltage stabilization time
≤250 kw & gt； 250 kw
≤2s ≤ 1.5s
14, voltage fluctuation
≤250 kw & gt； 250 kw
0.8% 0.5%
15, frequency steady-state adjustment rate
≤250 kw & gt； 250 kw
3% 3%
16, frequency transient adjustment rate
≤250 kw & gt； 250 kw
9% 9%
17, frequency stabilization time
≤250 kw & gt； 250 kw
5s ≤5s
18, frequency fluctuation
≤250 kw & gt； 250 kw
≤0.8% ≤0.5%
19, voltage deviation under three-phase asymmetric load
The diesel generator set shall be able to work normally under 25% three-phase symmetrical load and 25% rated phase power resistive load in any phase, and the maximum or minimum line voltage shall be 5% of the average three-line voltage.
20. Noise
Average noise sound pressure at 1m from the diesel engine and generator of the unit:
≤250 kw & gt； 250 kw
≤ 102 dB (A)≤ 108 dB (a)
Noise standard:
sleep
work
Children who listen to music for 80db live in a noise environment above 80 dB, resulting in 50% people being deaf. Only when the noise level is below 80 decibels can they work continuously for 40 years without deafness. At 100 decibel, only 60% people will not be deaf. If people live in an environment above 80 decibels for a long time, it will cause emotional irritability and hearing loss. Noise is harmful to people's central nervous system and can induce cardiovascular diseases. When eating in a noisy environment, gastrointestinal capillaries will contract, digestive juice secretion and gastrointestinal peristalsis will be weakened, and normal blood supply will be destroyed. Strong noise can also cause abnormal pregnancy and mental retardation of children. Therefore, we should minimize the source and spread of noise in our daily life.
Less than 85 decibels will cause slight hearing damage;
85 decibels -90 decibels can cause noise deafness in a few people;
90- 100 decibel can cause a certain amount of noise deafness;
More than 100 decibel will cause a considerable amount of noise deafness, which belongs to chronic noise deafness.
/kloc-above 0/05 decibel-schizophrenia for 5 minutes.
2 1, fuel consumption rate. The rated power of the unit is 120.
22, diesel generator consumption rate. The rated power of the unit is >: 40KW, and the unit consumption rate is ≤ 3.0g/kW h.
23. Run the test under calibration conditions.
Under the specified working conditions (Section 4.2 of GB2820), the generator set shall be able to run normally and continuously 12h (including 1h 10% operation) under the calibrated working conditions, and the diesel generator set shall be free of water leakage and air leakage.
24, remote control, remote communication and telemetry performance
(1) intelligent unit
Units above 200KW should be intelligent, and their monitoring contents and interface requirements are as follows:
① Remote control: start/stop, emergency stop, and switch between main and standby machines.
② Communication: working state (running/stopping), working mode (automatic/manual), main unit, overvoltage, undervoltage, overcurrent and frequency.
③ Telemetry: three-phase output voltage, three-phase output battery voltage and output power.
④ Interface: It should have communication interfaces (RS-232 and RS-485/422) and provide a complete communication protocol.
(2) Non-intelligent unit
Non-intelligent units of 200KW and below have no requirements for remote control, remote communication and telemetry.
Third, the choice of emergency diesel generator
Emergency diesel generators are mainly used in important places. When power is cut off in an emergency or accident, the emergency generator set can quickly recover and extend the power supply time. This kind of electric load is called class I load. Equipment, instruments and computer systems that have strict requirements on power outage time should be equipped with batteries or UPS for power supply in addition to generators.
Emergency diesel generators have two characteristics:
1 is characterized by emergency use and short continuous working time. Generally, it only needs to run for a few hours (≤ 12h).
The second feature is standby, and emergency generator sets are usually in standby state. Only when the main power supply is completely cut off, the emergency diesel generator set will start to operate to supply power to the emergency power load, and when the main power supply returns to normal, the power will be cut off immediately.
(1) Determination of generator capacity of emergency diesel generator
The calibrated capacity of emergency diesel generator set is 12h calibrated capacity after atmospheric correction, and its capacity should meet the total calculated load of emergency electricity, and it should be checked according to the starting requirements of single motor whose generator capacity can meet the maximum capacity in the first-class load. Three-phase AC synchronous generator is generally selected for emergency generator, and its rated output voltage is 400V V V.
(2) Determination of the number of emergency diesel generator sets
When there are multiple generator sets for standby, only 1 emergency diesel generator set is generally set. Considering the reliability, two generator sets can also be selected to supply power in parallel. In general, the number of emergency generator sets should not exceed 3. When selecting multiple units, complete sets of equipment with the same model, the same capacity and similar characteristics of voltage regulation and speed regulation should be selected as far as possible, and the properties of fuel used should be consistent, so as to facilitate maintenance and spare parts. When there are two emergency generator sets, the self-starting device should make the two sets stand by each other, that is, after confirming the power failure of the mains through delay, send out the self-starting instruction. If 1 unit fails to start for three consecutive times, it shall send out an alarm signal to automatically start the second diesel generator.
(3) Selection of emergency diesel generator
The emergency generator set shall be a diesel generator set with high speed, supercharging, low fuel consumption and the same capacity. High-speed supercharged diesel engine has large capacity and small occupied space; Diesel engine is equipped with electronic or hydraulic speed regulating device, which has good speed regulating performance; The generator should choose synchronous motor with brushless excitation or phase compound excitation device, which is more reliable, with low failure rate and convenient maintenance. When the capacity of a single air conditioner or motor in a load is large, the generator set excited by the third harmonic should be selected; The machine is assembled on the chassis with shock absorber; Mufflers should be installed at the outlet of smoke exhaust pipes to reduce the impact of noise on the surrounding environment.
(4) Control of emergency diesel generator set
The control of emergency generator set should have quick self-start and automatic input device. When the main power supply is cut off, the emergency device should be able to start quickly and restore power supply. The allowable power-off time of the first-class load varies from ten seconds to tens of seconds, depending on the specific situation. When the main power supply of an important project is cut off, it should take 3-5S to determine the time to avoid instantaneous voltage drop and the time to shut down the municipal power grid or automatically put the standby power supply into operation, and then issue the instruction to start the emergency generator set. It will take some time from command, unit start-up, speed increase to full load. Generally, large and medium-sized diesel engines also need to be pre-lubricated and warmed up to make the oil pressure, oil temperature and cooling water temperature meet the technical requirements of the factory. Pre-lubrication and preheating can be carried out in advance according to different conditions. For example, emergency units such as military communications, important foreign affairs activities in large hotels, large-scale mass activities in public buildings at night, and important surgical operations in hospitals should be in a state of pre-lubrication and pre-heating at ordinary times, so as to start quickly at any time and minimize the power outage time.
After the emergency unit is put into operation, in order to reduce the mechanical and current impact when the load suddenly increases, it is best to increase the emergency load in stages according to the time interval under the condition of meeting the power supply requirements. According to the national standards and national military standards, the first allowable load after the automatic unit is successfully started is: if the rated power is not more than 250KW, the first allowable load is not less than 50% of the rated load; Rated power greater than 250KW shall be specified in the technical conditions of the manufacturer. If the requirements of instantaneous pressure drop and transition process are not strict, the sudden load increase or sudden load decrease of the general unit should not exceed 70% of the rated capacity of the unit.
Four, the choice of commonly used diesel generator set
Some diesel generator sets, as a common power supply for electric loads, need to run continuously for a certain period of time or often for a long time. This kind of generator set is called ordinary generator set. Ordinary generator sets can be used as ordinary generator sets and standby generator sets. In towns, islands, forest farms, mines, oil fields and other areas far away from the large power grid or industrial and mining enterprises, in order to supply power to the factories and lives of local residents, it is necessary to install diesel generators, which should be continuously operated at ordinary times.
National defense projects, communication hubs, radio stations, microwave relay stations and other important facilities should be equipped with standby diesel generator sets. When power levels are used, such facilities can be powered by the main grid. However, due to natural disasters such as earthquake, typhoon, war or human factors, after the urban power grid is damaged or blacked out, the standby generator set should be started quickly and continuously for a long time to ensure continuous power supply to these important engineering loads. The standby generator set also belongs to the common generator set type. The commonly used generator sets work for a long time and the load curve changes greatly. The selection of unit capacity, quantity and type and the control mode of the unit are different from those of the emergency unit.
1. Determination of the capacity of common diesel generator sets
According to the long-term continuous operation of the unit, the output power can meet the maximum calculation load selection of the whole project, and the standby unit capacity of the generator set should be determined according to the importance of the load. The continuous output power of diesel engine is generally 0.9 times of rated power.
2. Determination of the number of commonly used diesel generator sets
The number of commonly used diesel generator sets is usually more than 2 to ensure the continuity of power supply and adapt to the change of power load curve. Only when there are a large number of diesel engines, can the number of diesel engines put into operation be determined according to the change of power load, so that diesel engines can often run under economic load to reduce fuel consumption rate and power generation cost. The best economic operation state of diesel engine is between 75% and 90% of rated power. In order to ensure the continuity of power supply, common units should consider setting up their own standby units, so that when the units are overhauled or shut down, the generating units can still provide uninterrupted power supply to important power loads.
3. Determination of common diesel generator speed
In order to reduce the wear and prolong the service life of the generator set, the ordinary generator set should choose the medium and low speed generator set with rated speed not more than 1000r/min, and the standby generator set can choose the medium and high speed generator set. Units in the same power station should have the same model and capacity, so as to use the same spare parts and facilitate maintenance and management. For projects with large load changes, the same series of units with different capacities can also be selected. The rated output voltage of the generator is the same as that of the emergency generator set, generally 400V V V. High-voltage generator sets can be used for projects with large electricity consumption and long transmission distance.
4. Control of ordinary diesel generator set
Generally, parallel connection should be considered for commonly used units to simplify the main wiring of distribution, so that when the units are started and stopped alternately, the power supply will not be interrupted due to parallel operation, load transfer and unit switching. The unit should be equipped with the measurement and control device of the unit, and the speed regulation and excitation adjustment device of the unit should meet the requirements of parallel operation of fish. For the standby generator set that supplies power to important loads, it is advisable to choose automatic diesel generator set, which can automatically start after the failure of external power supply and quickly restore power supply to important loads. When the diesel engine is running, there is a lot of noise in the engine room, which is convenient for the automatic unit to be modified into a generator set that operates in different compartments and is automatically monitored. When the generator set is running normally, the operator can monitor the diesel generator set in the control room without entering the diesel engine room.
Verb (abbreviation of verb) Order requirements for diesel generator sets
After making the above selection, the order of diesel generator set shall generally indicate the following contents:
(1) Model, rated power, rated frequency, rated voltage, rated current, phase number, power factor and connection mode of the unit.
(2) Function and performance requirements of unit automation.
(3) Requirements for the structure, performance and installation dimensions of diesel engine, generator and control panel.
(4) Requirements for parallel operation of units: whether it is required to purchase multiple units at the same time, and whether it is necessary to provide measuring instruments and devices required for parallel operation.
(5) Requirements for auxiliary equipment of the unit: Many domestic manufacturers count the cooling water tank (radiator), oil tank, exhaust muffler and battery. As auxiliary equipment, some installation requirements are allowed when ordering.