Characteristics and application of high voltage generator
The high-voltage diesel generator is applied to the emergency standby power supply system of metallurgical enterprises, airports, data centers, etc. because the output voltage of the genset is 10kV and the voltage of the original power supply system is the same, it can be directly connected to the power supply system, which saves a lot of equipment investment in the power supply and distribution system.
At the same time, due to the high output voltage, low output current and small power loss in the process of power transmission, it is suitable for long-distance transmission.
The high-voltage generator produced by our company is applied to emergency standby power supply systems such as metallurgical enterprises, airports, data centers, etc. because the output voltage of the unit is 10kV and the voltage of the original power supply system is the same, it can be directly connected to the power supply system, which saves a lot of equipment investment in the power supply and distribution system.
At the same time, due to the high output voltage, low output current and small power loss in the process of power transmission, it is suitable for long-distance transmission. The main voltage levels of 50Hz high-voltage diesel generator set are: 6kV, 6.3kV, 6.6kV, 10kV, 10.5kv, 11kv, etc., one set
The power is generally above 1000kW, and several sets gensets are used in parallel.
The control system of high voltage unit is mainly composed of high voltage switch cabinet and centralized control console. The high-voltage switch cabinet can be set in the special distribution room for centralized management, and the centralized console can be installed in the central control room. It is installed on the integrated protector and centralized control panel of high-voltage switch cabinet
The 8808 control panel is equipped with the general RS232 and Modbus communication protocol interface. Users can collect the real-time data of the whole control system according to their needs, conduct centralized monitoring and archive management.
The high voltage 8808 intelligent control system is mainly composed of generator incoming cabinet (parallel cabinet), Pt cabinet and outgoing cabinet. The 8808 intelligent main controller has integrated the comprehensive protection function of the generator set, and has met the basic protection requirements of the unit itself and its auxiliary equipment.
Conditions for operation of several sets high voltage generators
The whole process of parallel operation of high-voltage generator set is called paralleling. One generator set is taken from operation first, and the voltage is sent to the bus. After the other generator set is started, it is paralleled with hundreds of billions of generator sets. At the moment of closing, the generator set shall not have harmful impulse current
The shaft is not subject to sudden impact. After closing, the rotor shall 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 phases of the two generators are the same.
3. The frequency of two generator sets must be the same.
4. The phase sequence of the two generator sets is the same.
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 diesel engine or gas turbine engine, the power part of the generator set in the communication system, is basically the same to the high-pressure unit and the low-pressure unit;
The configuration of the oil system is 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 providing cooling for the unit. Main differences in parameters and performance between high voltage generator set and low voltage generator set
Now the generator part and the distribution system part.
1. Difference in volume and weight
The high-voltage generator is used in the high-voltage generator set. The improvement of the voltage level makes its insulation requirements higher. Accordingly, the volume and weight of the generator part is larger than that of the low-voltage generator set. Therefore, the volume and weight of the whole body of 10kV generator set is slightly larger than that of low-voltage generator set.
There is no big difference in appearance except for the generator.
2. Difference of grounding method
The neutral grounding mode of the two generator sets is different. The winding of 380V unit is star connection, and the general low-voltage system is neutral point direct grounding system, so the star connection neutral point of generator is set as withdrawable type, which can be directly grounded when needed.
10kV system is a small current grounding system, and the neutral point is generally ungrounded or grounded through grounding resistance. Therefore, compared with low-voltage units, 10kV units need to add neutral distribution equipment such as resistance cabinet and contactor cabinet.
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 ground fault occurs in the operation of high-voltage generator set, there is a great potential safety hazard to people and equipment, so it is necessary to set up the ground fault protection.
When a single-phase ground fault occurs, the fault current flowing through the neutral point can be detected, and the tripping or shutdown protection can be realized by relay protection. The generator neutral point is grounded through resistance, which can limit the fault current to the generator
Within the allowable damage curve, the generator can operate with fault. Through the grounding resistance, the ground fault can be detected effectively and the relay protection can be driven. Compared with the low-voltage unit, the high-voltage generator unit needs to add neutral distribution equipment such as resistance cabinet and contactor cabinet.
If necessary, differential protection shall be set for high-voltage generator set.
Three phase current differential protection is provided on the stator winding of the generator. Through the current transformer installed at two outgoing ends of each coil of the generator, the current difference between the incoming and outgoing ends of the coil is measured to judge the insulation condition of the coil. When any two phases or When three phases are short circuited or grounded, fault current can be detected in both transformers, so as to drive protection.
4. Difference of output cable
Under the same capacity level, the diameter of outgoing cable of high voltage unit is much smaller than that of low voltage unit, so the requirement for space occupation of outgoing channel is lower.
5. Differences of unit control system
Generally, the unit control system of low-voltage unit can be integrated on one side of the generator on the main body, while the high-voltage unit needs 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 high-voltage generator set in oil system, air inlet and exhaust system are equivalent to that of low-voltage generator set, but the power distribution of the unit is high-voltage system, which requires maintenance personnel to be equipped with high-voltage work license.
The following table is the technical comparison table of high and low voltage generator sets, in which the capacity of generator sets is 2000kW.
Economic comparison between high voltage generator and low voltage generator
If only considering the cost of the genset itself, the cost of high-voltage generator unit is about 10% higher than that of low-voltage generator. If it is considered that there are few distribution cables, few switching points with the municipal power supply, and therefore the cost of civil engineering is saved, the comprehensive cost of the high-voltage generator is lower than that of the low-voltage generator.
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