The high-voltage generator set is powered by domestic and foreign high-quality brand diesel engines, in accordance with the provisions of the national standard GB2820 General Technical Conditions for Power Frequency Diesel Generator Sets, and with reference to IEC34-IInternational Electrotechnical CommissionRotating motor standard, high voltage series produced by high-quality generators at home and abroadGenerator Set。
With the increasing integration of communication equipment and the growing data business, the power consumption of the communication hub building is also growing rapidly, which requires the use of multiple large capacity generator sets to provide backup power.If the traditional 380 V generator set is used for power supply, a lot of power cables and cable channel space will be consumed.Moreover, many generator units often cannot solve the problems of installation location, air inlet and exhaust, smoke exhaust, noise elimination, etc. in the hub building, and need to be installed in the supporting machine room at a certain distance, which consumes more cables and cable channels.Therefore, in recent years, the industry has proposed to use the 10 kV generator set as the standby power supply, which can significantly save power cables, reduce line loss, and save cable channels and civil engineering costs compared with the conventional 380 V generator set.In the construction of communication hub buildings or data centers with large power consumption, this can be listed as an important backup generator set solution.
High voltage generator sets are mainly divided into 6 kV and 10 kV.These two voltage levels are called medium voltage in the power industry.This textbook calls it high voltage, which is mainly relative to 380 V low voltage.Since the medium voltage power supply level of the State Grid for general industrial users is 10 kV, the high-voltage units used in the communication industry are all 10 kV, so this textbook only introduces 10 kV generator units.
Chinese name
High voltage generator set
Related dimensions
《IEC34-I》
Category
Motor set
Features
High voltage regulation accuracy and good dynamic performance
High pressure generator set is divided into diesel and heavy oil, with high pressure regulation accuracy,Dynamic performanceGood, small voltage waveform distortion, high efficiency, compact structure, convenient maintenance, reliable operation, long service life, good economic performance, etc.
Application scenarios of high-voltage generator sets
In general communication hubs, low-voltage generator sets can solve the problem of standby power supply.In large communication hubs, especially large IDC, high-voltage generator sets are more suitable.That is to say, the high-voltage generator set is suitable for use in scenarios where the load required to be guaranteed by the oil engine is large, and the diesel engine room is far away from the load, so large capacity units are required.The single unit capacity of high-voltage generator units is relatively large, mainly over 1000kW.Taking Caterpillar 10kV generator set as an example, its single unit capacity is 1000kVA-3100kVA in 1500r/min series and 2688kVA-7150kVA in 1000r/min series.
The application of high-voltage generator sets leads to the problem of conversion point between generator sets and mains power.In the 380V low-voltage system, the conversion point between the generator set and the mains is naturally at the low-voltage side.As for the high-voltage generator set, if it is still switched with the power supply on the low-voltage side, multiple switching points will be generated due to the decentralized low-voltage load, which will increase the complexity of the system.Therefore, when using high-voltage generator sets, the scheme of switching between the high-voltage side and the mains is usually adopted.
Parallel operation conditions
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High voltage generator set inputParallel operationThe whole process ofGenerator SetRun to get it first and send the voltage toa bus or bus barAfter the other generator set is started, it is parallel with 100 billion generator sets. At the moment of closing, the generator set should not appear harmfulImpulse currentThe rotating shaft is not subject to sudden impact.After closing, the rotor should be pulled into synchronization quickly, so the generator paralleling must meet the following conditions:
1. The effective value and waveform of generator set voltage must be the same.
2. The voltage phase of two generators is the same.
3. The frequency of two generator sets must be the same.
4. The phase sequence of two generator sets is consistent.
Main technical differences between high-voltage generator set and low-voltage generator set
The generator set is generally composed of engine, generator, unit integrated control system, oil circuit system and power distribution system.The power part of the generator set in the communication system - diesel engine or gas turbine engine is basically the same for the high pressure unit and the low pressure unit;The configuration of the oil system and the fuel quantity are mainly related to the power, so there is no obvious difference between the high and low pressure units, so there is no difference in the requirements of the air inlet and exhaust system of the unit that provides cooling for the unit.The difference in parameters and performance between high-voltage generator set and low-voltage generator set is mainly reflected in the generator part and distribution system part.
1. Difference in volume and weight
The high-voltage generator sets use high-voltage generators, and the improvement of voltage level makes its insulation requirements higher. Accordingly, the volume and weight of the generator part are larger than those of low-voltage units.Therefore, the volume and weight of the overall body of the 10kV generator unit is slightly larger than that of the low-voltage unit.There is no big difference in appearance except for the generator part.
2. Difference of grounding methods
The neutral grounding modes of the two generator sets are different.The 380V unit winding is star connected. Generally, the low-voltage system is a neutral point directly grounded system, so the star connected neutral point of the generator is set to be withdrawable and can be directly grounded when needed.10kV system is a small current grounding system, and the neutral point is generally not grounded or grounded through grounding resistance.Therefore, 10kV units need to add resistance cabinet, contactor cabinet and other neutral point distribution equipment compared with low-voltage units.
3. Differences in protection methods
High voltage generator sets are generally required to be equipped with current quick break protection, overload protection, grounding protection, etc.When the sensitivity of current quick break protection does not meet the requirements, longitudinal differential protection can be installed.
When the grounding fault occurs in the operation of high-voltage generator set, it will cause great potential safety hazards to personnel and equipment, so it is necessary to set up grounding fault protection.
The neutral point of the generator is grounded through resistance. When a single-phase grounding fault occurs, the fault current flowing through the neutral point can be detected, and tripping or shutdown protection can be realized through relay protection.The generator neutral point is grounded through resistance, which can limit the fault current within the allowable damage curve of the generator, and the generator can operate with fault.Through the grounding resistance, the grounding fault can be effectively detected and the relay protection action can be driven.Compared with low-voltage units, high-voltage generator units need to add resistance cabinets, contactor cabinets and other neutral point distribution equipment.
Differential protection shall be set for high-voltage generator set when necessary.
Three phase current differential protection is provided on the stator winding of the generator.The current transformer installed at the two outgoing terminals of each coil of the generator is used to measure the current difference between the incoming and outgoing terminals of the coil, so as to judge the coil insulation.When any two or three phases are short circuited or grounded, fault current can be detected in both transformers to drive protection.
4. Difference of output cable
Under the same capacity level, the outlet cable diameter of HV unit is much thinner than that of LV unit, so the space occupation requirement for outlet channel is lower.
5. Difference of unit control system
The unit control system of low-voltage units can generally be integrated on one side of the generator on the airframe, while the high-voltage units generally need an independent unit control box, which is arranged separately from the unit, in consideration of signal interference.
6. Differences in maintenance requirements
The maintenance requirements of the high-pressure generator set in the oil system, air inlet and exhaust system and other aspects are equivalent to those of the low-pressure generator set, but the power distribution of the unit is a high-voltage system, and the maintenance personnel need to be equipped with high-voltage work permits.
Table 1 is the technical comparison table of high and low voltage generator sets, in which the capacity of generator sets is 2000kW.
Table 1 Technical Comparison of 2000kW High and Low Voltage Generator Sets
S/N
Compare items
380V generator set
10kV generator set
one
engine
identical
identical
two
alternator
380V
10kV, reinforced insulation, increased weight and size
three
area covered
Quite
Quite
four
Installation mode
identical
identical
five
Rated current
3800A
144A
six
Unit cost
low
Slightly higher than low pressure, about 10%
seven
Power distribution equipment
low
Increase PT cabinet and protection, high
eight
Neutral equipment
nothing
A set of contactor cabinet and resistance cabinet
nine
Power transmission distance
Short, line loss and voltage drop shall be considered
long
ten
Power supply cable or bus
Large current, thick wire diameter, difficult layout, high civil engineering cost
Economic comparison between high voltage generator set and low voltage generator set
If only the cost of the unit itself is considered, the cost of the high-voltage generator unit is about 10% higher than that of the low-voltage generator unit.If considering that there are fewer distribution cables and switching points with the city power for the high-voltage generator set, and therefore the civil engineering cost is saved, the comprehensive cost of the high-voltage generator set is lower than that of the low-voltage generator set.Table 2 takes the 1800 kW unit as an example to make a rough comparison of the economy of high and low voltage units.
Table 2 Economic Comparison of High and Low Voltage Generator Sets
Increased equipment costs for high and low voltage systems
120000 yuan/set × 2 sets=240000 yuan
300000 yuan/set × 2 sets=600000 yuan
four
Subtotal of equipment cost
4.75 million yuan
3.75 million yuan
five
Cable cost from unit to incoming cabinet
34881 yuan/meter × 30 meters=10500 yuan
(Cable specification: YJV10kV3 × 95)
223.03 yuan/m × (25 × 30) m=167300 yuan
(Cable specification: RVV1kV1 × 240)
six
Cable cost from unit feeder cabinet to commercial oil engine conversion cabinet
790.07 yuan/m × (2 × 100) m=158000 yuan
(Cable specification: YJV10kV3 × 300)
223.03 yuan/m × (25 × 100 × 2) m=1115200 yuan
(Cable specification: RVV1kV1 × 240)
seven
Subtotal of cable cost
168500 yuan
1282500 yuan
eight
total
4918500 yuan
5.0325 million yuan
Winter startup skills
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Preheating in severe cold season
Diesel enginestaycold bootThe failure to reach the compression ignition temperature of diesel fuel is an important reason affecting the starting performance.In this regard, hot water can be added to the engine cooling system for preheating, which is an effective way to improve the starting performance.The specific method is: continuously heat the water (let the water flow out of the cylinder block), and gradually increase the water temperature for preheating.Turn off the water drain switch when the outflow water temperature is high.In addition, availableBlowtorchHeat the oil pan with open flame to improve the flow performance of oil and reduce the movement resistance of parts.
Improve the sealing performance of cylinder
One of the differences between diesel engine and gasoline engine is compression ignition type, so cylinders are required to have high sealing performance.When the engine is started cold in winterPiston ringThere is little oil on the cylinder wall, and the sealing effect is poor, which may lead to repeated starting without ignition.Sometimes the sealing performance of the cylinder is seriously affected due to the heavy wear of the cylinder, which makes starting more difficult.In this regard, the fuel injector can be removed and 30~40ml engine oil can be added into each cylinder to enhance the sealing performance of the cylinder and increase the pressure during compression.Exhaust the air in the oil circuit
Unscrew the bleed screw on the high-pressure oil pump and pump oil by hand to drain the air in the low-pressure oil circuit;Then, exhaust the air in the high-pressure oil circuit.The specific method is as follows: unscrew the oil pipe connector on each injector, make the throttle at the maximum oil supply position, and rotate the crankshaft until the oil pipe connector of each cylinder injector has a rapid oil delivery.
Antifreeze work
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1. Add cooling water after starting.After starting the diesel engine, the temperature inside the engine rises immediately. If cooling water is added at this timeThe cylinder coverSharp cooling will cause cracks due to cold shrinkage.
2. After shutdown, no cooling water was discharged.The water in the machine freezes into ice, and the volume increases, causing the cylinder block and cylinder head to crack.
3. When the diesel engine is running, the cooling water is insufficient or the temperature of the boiler in the water tank is too high, so the cooling water is suddenly added.Shrinkage of the cylinder block and cylinder head due to supercooling can also cause cracking.
4. The diesel engine has been running for a long time, and the temperature inside the engine is high, so the high-temperature water shall be discharged immediately after shutdown.It may cause sudden encounter of high temperature partscold airAnd cracking.
5. Use the pressure reducer to shut down and make the high-temperatureThe cylinder coverCracking caused by sudden cold air.
Prevent all kinds ofCylinder blockThe following methods are available for cracking of cylinder head:
1. Before starting the diesel engine, warm hot water should be added to the water tank first. In severe winter, hot water should be filled for 2-3 times. It is better to start when the water from the drain valve is about 30~50 ℃.
2. If the diesel engine has been running for a long time, wait about half an hour after shutdown, and drain cooling water when the engine temperature drops to 40~50 ℃.After draining, it is better to poke the drain valve switch with a fine wire to prevent sediment from blocking the drain valve.
3. When the diesel engine runs overheated and is seriously short of water, let the diesel engine idle at low speed for 10-15 minutes, and then slowly add cooling water.
