一、The basis of a diesel generator unit of choose and buy
1.The selected the performance of the diesel generator set and the quality must conform to the requirements of the relevant standards
Diesel generator is widely used in telecommunications, financial department, hospital, school, business and other departments, industrial and mining enterprises and residential emergency standby power, military and fieldwork, vehicle and ship special purposes such as independent power supply.
As communication diesel generating sets, must achieve GB2820 G4-1997 grade G3 or the requirements of the class, and at the same time, the communication network access of diesel generating sets of quality certification testing out detailed rules for the implementation of "regulations of 24 performance requirements, at the same time, through to our country industry established by the competent department of communication power supply equipment quality supervision and inspection center strict inspection.
As a military communication credit diesel generator set, it must meet the relevant gb2820-1997, GJB related standards and the provisions of the "communication power supply equipment quality inspection standards" formulated by the relevant departments of the army, and through the relevant organizations and departments of the quality of the equipment for strict inspection.
2.The choice of diesel generator set should consider the main factors
Unit selection should consider the factors mainly include mechanical and electrical properties, the purpose of the unit, load capacity and range, automation, etc.
（1） The purpose of the unit. Due to the diesel generator set can be used on three kinds of commonly used, standby and emergency situations. Therefore different USES is different to the requirement of diesel generator set.
（2） Load capacity. Should choose according to different purposes of load capacity and load range, determine the diesel generating set of machine capacity and standby diesel generator set capacity.
（3） Unit using environmental conditions (mainly refers to the altitude and climate conditions)
（4） The choice of diesel generators
（5） The generator and excitation mode choice
（6） Diesel generator automation function of choice
二、Diesel generating sets the standard of choose and buy
Communication network access of diesel generating sets of quality certification testing rules > > 24 performance index prescribed requirements：
（1） The boundaries of diesel generating set size, the size of the installation and connection size are conform to the prescribed procedures approved by the product design.
（2） Welding of the unit should be strong, weld should be uniform, no welding wear, bite edge, slag inclusion and porosity defects, such as welding slag welding flux should be cleared; Coating should be uniform, without obvious crack and fall off; Coating shall be smooth, no plating leakage spots, such as corrosion phenomenon; Fasteners should be no loose unit.
（3） Diesel generator electrical installation shall comply with the circuit diagram, the each wire connection of the unit should have obvious sign of not easy to fall off.
（4） Diesel generator should be good grounding terminals.
（5） Diesel generator panels complete content.
2.Insulation resistance and dielectric strength
（1） The electric circuits of the insulation resistance: the independence of the ground and the insulation resistance between circuit should be greater than 2 m.
（2） Dielectric strength: the unit of each independent electric loop and loop should be able to withstand the test voltage for 1 min, communication between should be no breakdown or flashing phenomenon.
Circuit voltage test voltage
3.Phase sequence. Diesel generator set control panel terminal phase sequence of the look from the front control panel should be sorted from left to right or from top to bottom.
4.Diesel generators to maintain for running state requirements. Unit should have heating device, ensure the emergency start and rapid loading when the oil temperature, cooling medium temperature is not lower than 15 ℃.
5.Automatic startup power supply and the reliability of the automatic stop check
（1） Joint control or remote control of the startup command, the diesel generator should be able to start automatically.
（2） Unit start automatically after the 3rd time failure, should signal launch failure; Has a spare unit, program should be able to start the system will automatically start instructions transmitted to another spare units.
（3） From the automatic startup instruction to supply power to the load time should not more than 3 min
（4） After the success of the diesel generator automatically start, loading calibration load should be not less than 50% for the first time.
（5） After receiving automatic control or remote control stop instruction, the unit should be able to stop automatically; For the standby units used with the municipal power grid, when the power grid returns to normal, the diesel generator should be able to automatically switch or automatically shut down, and the shutdown delay time of the shutdown mode should meet the technical requirements of the product.
6、Automatic startup success rate. Automatic startup success rate is not less than 99%.
7、No-load voltage setting range. No-load voltage setting range of the unit is not less than 95% 105% calibration voltage.
8、Automatic recharge function requirements. The unit should be able to automatically to launch the battery.
9、Automatic protection function. Units should be lack of phase, short circuit (not more than 250 kw), over-current (not more than 250 kw), tachycardia, high water temperature cylinder temperature, low oil pressure protection.
10、Line voltage waveform sine distortion rate. In the no-load voltage calibration, calibration frequency, line voltage waveform sine distortion rate < 5%.
11、Steady-state voltage regulation
12、The transient voltage regulation rate
13、Voltage stability time
14、Voltage fluctuation rate
15、Frequency steady state regulation
16、Transient frequency regulation
17、Frequency stability time
18、Frequency of volatility
19、Three phase voltage deviation under asymmetry load
Diesel generating sets under the three-phase symmetrical load of 25%, plus 25% at any phase calibration phase power of resistive load, the unit should be able to work properly, line voltage of the maximum or minimum value with the three line voltage average value of 5%.
From the noise of the diesel engine and generator unit 1 m in average sound pressure:
The noise standard:
Sleep < 45 db residential area of the ambient noise, should not exceed 50 decibels during the day, night should be below 45 decibels (40)
Work <65 db average person can maintain normal reaction and attention below the sound of 40 decibels or so, but work in the environment of 50 decibels or above, for a long time, can appear hearing loss, mood be agitated, can appear neurasthenic wait for a phenomenon even.
Listen to music 80db children live in the noise environment of 80 decibels above, cause deaf and dumb person to be able to amount to 50%, when noise level is in 80 decibels only below, ability maintains 40 years of long-term work to send not deaf; At 100 decibels, only 60 percent of people are not deaf. If people live in the environment above 80 decibels for a long time, it will cause emotional irritability and hearing loss. Noise has damage effect to the central nervous system of the person, and can cause cardiovascular system disease, take food in intense noise environment, the capillary of gastric bowel can produce systole, of digestive juice secrete and gastric bowel wriggle can abate, make normal blood is supplied be destroyed. Loud noises can also cause abnormal pregnancies and mental retardation in children. Therefore, in daily life to minimize the source and spread of noise.
Below 85 decibels can cause mild hearing loss；
85 db - 90 db noise can cause a few deaf；
90-100 decibels can cause a certain amount of noise deafness；
100 decibels, can cause a considerable amount of noise deafness, these belong to chronic noise deafness.
105 decibels - 5 minutes of schizophrenia
21、Specific fuel consumption. Unit nominal power in 120. H
22、Diesel generator consumption rate. Power unit calibration > 40 KW, the unit consumption of 3.0 G/KW or less. H
23、In the calibration run under the condition of test
Units specified working conditions (section 4.2) in GB2820, 12 h to calibration condition of normal continuous operation (including the 1 h overload 10%), and diesel generator set should be no water and air.
24、Remote control, remote and remote sensing performance
（1） Intelligent unit
More than 200 kw unit should be intelligent, its monitoring content and interface requirements are as follows：
①Remote control: turn on/off switch, emergency stop, the standby unit.
②Remote communication: working status (run/stop), work (to be automatic/manual), mainly use unit, overvoltage, undervoltage, over current, frequency.
③Remote sensing: three-phase output voltage, three-phase output dynamic battery voltage, the output power.
④Interface: should have communication interface (RS - 232 and RS - 485/422) and can provide complete communication protocol.
（2）The intelligent unit
Below 200 kw and the non intelligent unit without the remote control, remote and remote sensing requirements.
三、The choice of emergency diesel generator
Emergency diesel generator is mainly used in important places. In case of emergency or power failure, the generator set can be quickly restored and extended for a period of time. This type of electrical load is called a primary load. For equipment, instruments and computer systems with strict requirements for power off time, batteries or UPS power supply shall be provided in addition to generators.
The emergency diesel generator work has two features:
The first characteristic is for emergency use, continuous working time is not long, generally only needs to continue to run a few hours (12 h) or less;
The second characteristic is as a standby, stop waiting for emergency generator at ordinary times, only when the main drum with power supply all disabled after power, emergency diesel generator set to begin running supply emergency power load, when the main power supply back to normal after the switch immediately stop.
（1） The determination of the emergency diesel generator generator capacity
The calibrated capacity of the emergency diesel generator set is 12h calibrated capacity after atmospheric correction. The capacity should be able to meet the total calculation load of emergency electricity, and the calibration should be carried out according to the requirement that the generator capacity can meet the starting of a single maximum capacity motor in the first level load. Three-phase ac synchronous generator is generally used in emergency generators, and its calibrated output voltage is 400V.
（2） The determination of emergency diesel generator sets
When there are more than one generator set for standby, only one emergency diesel generator set is usually set. Considering the reliability, two generator sets can also be selected for parallel power supply. The number of generator sets in urgent need should not exceed 3. If more than one unit is selected, the unit shall try to select complete sets of equipment with the same model, same capacity, similar characteristics of pressure regulation and speed regulation, and the nature of fuel used shall be consistent for maintenance and sharing of spare parts. When there are two generator sets in urgent use, the self-starting device should enable the two sets to be standby for each other, that is, after the delay confirmation of the failure of the mains power supply, the self-starting instruction should be issued. If the first set fails to start itself for three times continuously, the alarm signal should be sent and the second set of diesel generator should be started automatically.
（3） The choice of emergency diesel generator
Emergency units should be selected high speed, supercharged, low fuel consumption, with the same capacity of diesel generator set. The single engine of high speed supercharged diesel engine has larger capacity and occupies less space. The diesel engine is equipped with electronic or hydraulic speed regulating device, which has good speed regulating performance. Generator should be equipped with brushless excitation or phase compound excitation of synchronous motor, more reliable, low failure rate, more convenient maintenance; When the capacity of a single air-conditioner or a motor is large in the first stage load, the generator set with third harmonic excitation should be selected. The unit is mounted on a common chassis with shock absorbers; A muffler should be installed at the outlet of the exhaust pipe to reduce the impact of noise on the surrounding environment.
（4） Emergency diesel generator set control
The control of emergency generator set should be provided with fast self-starting and automatic putting device. When the main power supply failure power off, the emergency unit should be able to quickly start and restore power supply, the allowable power off time of the primary load from ten seconds to dozens of seconds, should be determined according to the specific situation. When the main power supply of an important project is cut off, the time should first be determined by 3-5s to avoid the instantaneous voltage reduction and the time when the municipal power grid closes or the standby power supply is automatically put into use, and then the instruction to start the emergency generator set is issued. It will take some time from the instruction, starting of the unit, raising speed to the full load. General large and medium-sized diesel engines also need pre-lubrication and warm-up process, so that the oil oil pressure, oil temperature and cooling water temperature during emergency loading meet the requirements of the technical conditions of the plant; 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, important surgical operations in hospitals, etc., should be pre-lubricated and warmed up at ordinary times, so as to start up quickly at any time 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 during sudden loading, it is better 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 standard and the national military standard, the first allowable load of the automatic unit after starting successfully is as follows: the first allowable load is not less than 50% of the calibrated load if the calibrated power is no more than 250KW; For the calibration power greater than 250KW, according to the factory technical conditions. If the instantaneous voltage drop and the transition process requirements are not strict, the general unit sudden loading or unloading should not exceed 70% of the unit calibration capacity.
四、The choice of commonly used diesel generator set
Some diesel generator sets in a certain period of time or often need to be carried out for a long time continuously, in order to serve as the common power supply source of electricity load, this kind of generator set is called the common generator set. Common generator sets can be used as common and standby units. For towns, islands, forest farms, mines, oil fields and other areas or industrial and mining enterprises far away from the large power grid, in order to supply local residents with electricity for production and living, they need to install diesel generators, which should be carried out continuously 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. Such facilities can be supplied by the mains power grid in normal times. However, because of the earthquake, typhoon, war and other natural disasters or man-made factors, make the damage to the city power grid and power outages, is set of spare units should be starting soon, and insisted on non-stop for a long time, to ensure continuous power supply for these important engineering power load, the standby generator also belong to common type generator set. The common generator set has a long working time, the load curve changes greatly, the unit capacity, the number of units, the type selection and the unit control mode are different from the emergency unit.
1. The determination of commonly used diesel generator unit capacity
According to the unit operation output power for a long time can meet the engineering computation load biggest choice, and should be determined according to the importance of the load generator spare unit capacity. Continuous output power of diesel engine, generally for the nominal power of 0.9 times.
2. The determination 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 the number of units is large, can the number of units put into the generator set be determined according to the change of power load, so that the diesel engine often operates under economic load, so as to reduce fuel consumption and power generation cost. The optimum economical operation of diesel engine is between 75% and 90% of the nominal power. In order to ensure the continuity of power supply, the common units themselves should consider setting up standby units, when the unit failure maintenance or shutdown inspection, so that the generator set can still meet the important load of uninterrupted continuous power supply.
3. Commonly used diesel generator set control
In general, the common units should be considered to be able to be connected in parallel, so as to simplify the main distribution wiring, so that when the units start, stop and rotate, the power supply will not be interrupted by running in parallel, transferring load and switching the units. The unit shall be installed with the measuring and control device of the unit, and the speed regulation and excitation control device of the unit shall be applicable to the requirements of fish parallel operation. For backup generator sets that supply power to important loads, it is advisable to select automatic diesel generator sets that can start up automatically and restore power supply to important loads when external power failure occurs. The engine room is noisy when the diesel engine is running. The automatic generator set is easy to be transformed into a generator set with compartment operation and automatic monitoring. When the generator set is running normally, the operator does not need to enter the diesel engine room, but can monitor the diesel generator set in the control room.
4. Commonly used determine the rotational speed of diesel generator set
In order to reduce the wear and increase the service life of the unit, the normal generator set should use medium and low speed units with a nominal speed of no more than 1000r/min, and the standby unit can choose medium and high speed units. Units of the same power station should be of the same type and capacity, so as to use the same spare parts and facilitate maintenance and management. For projects with large load variation, the same series of units with different capacity can also be selected. The calibration voltage of generator output is determined as the same as that of emergency generator set, which is generally 400V. High voltage generator set can be selected for projects with large power consumption and long transmission distance.
五、Diesel generator set order
After make the choices, diesel generating sets order shall indicate the following content commonly:
（1） The unit model, rated power, rated frequency, rated voltage, rated current, phase number, power factor and connection mode, etc.
（2） To the automated functional and performance requirements.
（3） On diesel engine, generator and control panel structure, performance, installation size requirements.
（4） For parallel operation of the unit requirements: to buy more units at the same time, whether to ask in parallel, such as the need to be parallel, whether should also put forward a need to provide the necessary parallel measuring instruments and devices.
（5） Accessory equipment requirements for the unit: many domestic manufacturers put the water cooling tank, radiator, fuel tank and exhaust muffler, among other ancillary equipment, battery when placing order, allow to install some requirements are put forward.