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|Basis for purchasing diesel generator sets|
1. The performance and quality of the selected diesel generator set must meet the requirements of relevant standards
Diesel generators are widely used in telecommunication, financial and financial departments, hospitals, schools, businesses and other departments, industrial and mining enterprises and residential emergency backup power supplies, military and field operations, vehicles and ships and other special independent power supplies.
As a communication diesel generator set, it must meet the requirements of G3 or G4 in GB2820-1997, and it must meet the 24 performance index requirements specified in the Implementation Rules for the Quality Inspection and Certification of Communication Diesel Generating Units. Strict inspection by the quality supervision and inspection center of telecommunication power equipment set up by the industry authority in China.
As a military communications diesel generator set, it must meet the relevant GB2820-1997, GJB related standards and the "Quality Test Standards for Communication Power Equipment" formulated by the relevant departments of the army, and must pass strict inspections of equipment quality by relevant organizational departments.
2. The main factors that should be considered in the selection of diesel generator sets
The factors that should be considered in the selection of the unit mainly include mechanical and electrical performance, the purpose of the unit, the capacity and change range of the load, and the automation function.
The performance requirements for the implementation of the quality inspection of the diesel generator set for communication in the network> 24 requirements of the performance indicators:
1. Appearance requirements (1) The boundary size, installation size and connection size of the diesel generator set are in accordance with the factory design approved by the prescribed procedures. (2) The welding of the unit should be firm, and the welding seam should be uniform, without welding penetration, undercuts, clips Defects such as slag and porosity, the welding slag and flux should be removed; the paint film should be uniform without obvious cracks and peeling; the coating should be smooth without missing plating spots and rust;
2. Insulation resistance and insulation strength (1) Insulation resistance: The insulation resistance of each independent electrical circuit to ground and between circuits should be greater than 2M
Loop voltage test voltage
3. Phase sequence requirements. The phase sequence of the terminals of the diesel generator set control screen should be from left to right or top to bottom when viewed from the front of the control screen.
4. Diesel generators are required to maintain a ready-to-run state. The unit should have a heating device to ensure that the oil temperature and cooling medium temperature during emergency startup and rapid loading are not lower than 15 ℃
5. Reliability check of automatic start power supply and automatic shutdown (1) After receiving the start command of self-control or remote control, diesel generator should be able to start automatically.
6. Automatic startup success rate. The automatic startup success rate is not less than 99%.
7. No-load voltage setting range requirements. The no-load voltage setting range of the unit is not less than 95% -105% of the nominal voltage.
8, automatic supply function requirements. The unit should be able to charge the start-up battery automatically.
9, automatic protection function requirements. The unit should have phase loss, short circuit (not more than 250KW), overcurrent (not more than 250KW), overspeed, high water temperature cylinder temperature, low oil pressure protection.
10. Sine distortion of line voltage waveform. Under no-load calibration voltage and calibration frequency, the sinusoidal distortion rate of the line voltage waveform is less than 5%.
11.Voltage steady-state adjustment rate ≤250KW> 250KW
12.Voltage transient adjustment rate ≤250KW> 250KW
13.Voltage stabilization time ≤250KW> 250KW
14.Voltage fluctuation rate ≤250kw> 250kw
15.Frequency steady state adjustment rate ≤250kw> 250kw
16.Frequency transient adjustment rate ≤250kw> 250kw
17.Frequency stabilization time ≤250kw> 250kw
18.Frequency fluctuation rate ≤250kw> 250kw
19. Voltage deviation under three-phase asymmetric load. Under 25% three-phase symmetrical load, a diesel generator set is added with a resistance load of 25% of nominal phase power in any phase. Minimum and 5% of the three-wire voltage average.
20.The average value of noise sound pressure at 1m from the diesel engine and generator of the unit:
21. Fuel consumption rate. Unit rated power at 120
23. Running the test unit under calibration conditions Under the specified working conditions (Section 4.2 in GB2820), the unit can normally run continuously for 12 hours (including 10% overload for 1 hour) under calibration conditions, and the diesel generator set should No water leakage and air leakage.
24. Remote control, remote signaling and telemetry performance (1) Intelligent unit
(2) Non-intelligent unit
Emergency diesel generators are mainly used in important places. The power is cut off immediately after an emergency or accident, and the emergency generator set is used to quickly recover and extend the power supply period. This type of electrical load is called a primary load. Equipment, meters, and computer systems that have strict requirements for power failure time should be equipped with batteries or UPS in addition to generators.
The work of an emergency diesel generator has two characteristics:
(1) Determination of emergency diesel generator generator capacity
The calibrated capacity of the emergency diesel generator set is the 12h calibrated capacity after atmospheric correction. Its capacity should be able to meet the total calculated load of the emergency power, and it should be verified that the generator capacity can meet the requirement of starting a single maximum-capacity motor in the first-level load. . Emergency generators generally use three-phase AC synchronous generators with a nominal output voltage of 400V
(2) Determination of the number of emergency diesel generator sets
When there are multiple generator sets in standby, generally only one emergency diesel generator set is provided. For reliability considerations, two units can also be used in parallel to supply power. Generally, the number of generator sets for emergency use should not exceed three. When multiple units are selected, the units should try to use complete sets of equipment with the same model and capacity, similar pressure and speed characteristics, and the fuel properties used should be the same for maintenance and shared spare parts. When there are two generator sets for emergency use, the self-starting device should enable the two units to be used as backups for each other, that is, after a delay in confirmation of a power failure in the mains power supply, a self-starting command is issued. If the start fails, an alarm signal shall be issued and the second diesel generator shall be started automatically.
(3) Selection of emergency diesel generator
For emergency units, high-speed, supercharged, low fuel consumption, and diesel generators of the same capacity should be selected. High-speed turbocharged diesel engines have a large single-unit capacity and occupy a small space; diesel engines are equipped with electronic or hydraulic speed regulators for better speed regulation performance; generators should use synchronous motors with brushless excitation or phase compound excitation devices for reliable and faulty operation The rate is low, and maintenance is convenient; when the capacity of a single air conditioner or the motor is large in the first-level load, a third-harmonic excitation generator set should be selected; the machine is assembled on a common chassis with shock absorbers; exhaust smoke Mufflers should be installed at the pipe outlet to reduce the impact of noise on the surrounding environment.
(4) Control of emergency diesel generator set
The control of the emergency generator set should have fast self-starting and automatic input devices. When the main power fails, the emergency unit should be able to quickly start and resume power supply. The allowable power-off time of the first-level load ranges from 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, a certain time of 3-5S should be passed to avoid the instantaneous voltage drop and the time when the city grid is closed or the standby power is automatically turned on, and then the command to start the emergency generator set is issued. . It takes a period of time from the issue of the command, the start of the unit, the speed increase to the full load. Generally, large and medium-sized diesel engines also require pre-lubrication and warm-up processes, so that the oil pressure, oil temperature, and cooling water temperature of the engine during emergency loading conform to the technical specifications of the product; the pre-lubrication and warm-up processes can be performed in advance according to different situations. For example, military communications, important foreign affairs activities of large hotels, large-scale mass activities in public buildings at night, emergency surgical operations in hospitals, etc. should always be pre-lubricated and warmed up, so as to start quickly at any time and minimize power failure time. .
After the emergency unit is put into operation, in order to reduce the mechanical and electrical shock when the load is suddenly applied, it is best to increase the emergency load in steps according to the time interval when the power supply requirements are met. According to national standards and national military standards, the first allowable loading capacity of an automated unit since its successful start is as follows: For those with a calibrated power not greater than 250KW, the first allowable load is not less than 50% of the calibrated load; for those with a calibrated power greater than 250KW, according to the factory Product technical conditions. If the instantaneous voltage drop and transient process requirements are not strict, the sudden load or unload of the general unit should not exceed 70% of the unit's rated capacity.
Fourth, the choice of commonly used diesel generators
Some diesel generator sets need to be continuously performed for a certain period of time or often for a long period of time as a common power supply source for electrical loads. Such generator sets are called common generator sets. Commonly used generator sets can be used as common and standby units. In towns, islands, forest farms, mines, oil fields and other areas or industrial and mining enterprises far away from the large power grid, diesel generators need to be installed in order to supply local residents' plants and domestic electricity. Such generator sets should be carried out without interruption.
National defense projects, communications hubs, radio stations, microwave relay stations and other important facilities should be provided with spare diesel generator sets. Such facilities can be supplied by the utility power grid at the time of use. However, due to earthquakes, typhoons, wars and other natural disasters or man-made factors, after the power grid is damaged and the power supply is interrupted, the installed backup units should be started quickly and insist on continuous and long-term uninterrupted operation to ensure the use of electricity for these important projects. Continuous power supply of loads, this type of backup generator set also belongs to the common type of generator set. Common generator sets have a long continuous working time, a large change in load curve, and the choice of unit capacity, number, type, and control method of the unit are different from emergency units.
Determination of the capacity of commonly used diesel generators
According to the long-term continuous operation output power of the unit can meet the maximum calculation load selection of the entire project, and the standby unit capacity of the generating unit should be determined according to the importance of the load. The continuous output power of a diesel engine is generally 0.9 times the nominal power.
2. Determination of the number of commonly used diesel generating sets
The number of commonly used diesel generator sets is usually more than two to ensure the continuity of power supply and adapt to changes in the load curve. Only a large number of units can determine the number of generator units to be put into operation based on changes in the power load, so that diesel engines are often operated under economic loads to reduce fuel consumption and reduce power generation costs. The best economic operating state of a diesel engine is between 75% -90% of the rated power. In order to ensure the continuity of power supply, the common unit should consider setting up a standby unit. When the unit is overhauled or shut down, the generator set can still meet the uninterrupted and continuous power supply to important power loads.
3. Determination of the speed of common diesel generators
In order to reduce the wear and increase the service life of the unit, the commonly used generator set should choose the medium and low speed unit with the rated speed not greater than 1000r / min, and its standby unit can choose the medium and high speed unit. Units of the same power station should use units of the same model and capacity in order to use the same spare parts and facilitate maintenance and management. For projects with large load changes, units of the same series with different capacities can also be selected. The determination of the output calibration voltage of the generator is the same as that of the emergency generator set, which is generally 400V. Individual projects with large power consumption and long transmission distances can choose high-voltage generator sets.
4. Control of common diesel generator sets
Commonly used units should generally be considered in parallel to simplify the main wiring of the power distribution, so that when the units start, stop and rotate, they can pass parallel loading, transfer loads, and switch units without interrupting power supply. The unit should be installed with the measurement and control device of the organic group, and the speed regulation and excitation adjustment device of the unit should be suitable for the requirements of parallel fish and fish. For backup generator sets that supply power to important loads, an automatic diesel generator set should be selected. When the external power supply fails, it can start quickly and resume power supply to important loads. The engine room is very noisy when the diesel engine is running, and the automatic unit is easy to be transformed into a compartment-operated and automatically monitored generator set. When the generator set is running normally, the operator does not need to enter the diesel engine room, and can monitor the diesel generator set in the control room.
Five, order requirements for diesel generators
After making the above choices, the order of diesel generators should generally indicate the following:
|Source: Zhongsheng Generator Time: 2017/3/22|