Characteristics and application of high-voltage generator set
The high-voltage unit is used in emergency standby power supply systems such as metallurgical enterprises, airports, and data centers. Because the output voltage of the unit is 10KV and the original power supply system voltage is the same, it can be directly connected to the power supply system, eliminating the large investment in equipment for the power supply and distribution system.
At the same time, due to the high output voltage and small output current of the unit, the power loss during power transmission is small, which is suitable for long-distance transmission. The high-voltage generator sets produced by our company are used in emergency standby power supply systems such as metallurgical enterprises, airports, and data centers.Because the output voltage of the unit is 10KV and the original power supply system voltage is the same, it can be directly connected to the power supply system, eliminating the need for a large amount of supply and distribution Equipment investment for electrical systems.
At the same time, because the output voltage of the unit is high, the output current is small, and the power loss during power transmission is small, which is suitable for long-distance transmission. The main voltage levels of 50HZ high-pressure diesel generating sets are: 6KV, 6.3KV, 6.6KV, 10KV, 10.5KV, 11KV, etc., single unit
If the power is above 2000KW, multiple units can be used in parallel.
The high-voltage unit control system is mainly composed of two parts: high-voltage switchgear and centralized control console. The high-voltage switchgear can be set up in a special power distribution room for centralized management, and the centralized console can be installed in the central control room. Both the integrated protector installed on the high-voltage switchgear and the 8808 control screen on the centralized console have universal RRS232 and MODBUS communication protocol interfaces. Users can collect real-time data of the entire control system as required, and perform centralized monitoring and archive management.
The high-voltage 8808 intelligent control system is mainly composed of generator inlet cabinet (parallel cabinet), PT cabinet and outlet cabinet. The 8808 intelligent main controller itself has integrated a comprehensive generator set protection function, which has met the basic protection needs of the unit itself and its auxiliary equipment.
Conditions of high voltage generating units in parallel
The whole process of putting a high-voltage generator set into parallel is called paralleling. One generator set is first taken and the voltage is sent to the busbar. After the other generator set is started, it is tied with hundreds of billions of generator sets. At the moment of closing, The generator set should not have harmful impact current, and the rotating shaft should not be subject to sudden impact. After closing, Zigzag should be able to be pulled into synchronization very quickly, so parallel generators need to meet the following conditions:
1. The effective value of the generator set voltage is the same as the waveform.
2. The phases of the two generator voltages are the same.
3. The two generators have the same frequency.
4. The phase sequence of the two generator sets is the same.
Main technical differences between high-voltage generating sets and low-voltage generating sets
The generator set is generally composed of the 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 high-pressure units and low-pressure units;
The configuration of the oil circuit system and the amount of fuel 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 for the air intake and exhaust system of the unit that provides cooling for the unit. The difference in parameters and performance between the high-voltage generator set and the low-voltage generator set is mainly reflected in the generator part and the power distribution system part.
1. Difference in volume and weight
High-voltage generator sets use high-voltage generators. The increase in voltage level makes their insulation requirements higher. Correspondingly, the volume and weight of the generator part are larger than those of low-voltage generator sets. Therefore, the volume and weight of the whole body of the 10KV generator set is slightly larger than that of the low-voltage unit.
There is no big difference in appearance except for a slight difference in the generator part.
2. Differences in grounding methods
The two types of generators have different neutral grounding methods. The windings of the 380V unit are star-connected, and the general low-voltage system is a neutral point direct grounding system. Therefore, the star-point neutral point of the generator is set to be withdrawable and can be directly grounded when it is needed.
The 10KV system is a low current grounding system, and the neutral point is generally not grounded or grounded through a grounding resistance. Therefore, compared with low-voltage units, 10KV units need to add neutral point distribution equipment such as resistance cabinets and contactor cabinets.
3. Differences in protection methods
High-voltage generator sets generally require the installation of 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 a ground fault occurs in the operation of the high-voltage generator set, it will cause great safety hazards to people and equipment, so it is necessary to set up ground fault protection.
The neutral point of the generator is grounded through resistance. When a single-phase ground fault occurs, the fault current flowing through the neutral point can be detected, and the trip protection or shutdown protection can be achieved through the relay protection. The neutral point of the generator is grounded through resistance, which can limit the fault current to the generator
Within the allowed damage curve, the generator can run with faults. The grounding resistance can effectively detect the ground fault and drive the relay protection action. Compared with low-voltage units, high-voltage generator sets need to add neutral point distribution equipment such as resistance cabinets and contactor cabinets.
The high-voltage generator set shall be provided with differential protection when necessary.
Provide three-phase current differential protection on the stator winding of the generator. Through the current transformer installed at the two output ends of each coil of the generator, the current difference between the input and output ends of the coil is measured to judge the insulation of the coil. When any two phases or
When short circuit or grounding occurs in three phases, fault current can be detected in the two transformers to drive protection.
4. Differences in output cables
At the same capacity level, the diameter of the outlet cable of the high-voltage unit is much thinner than that of the low-voltage unit, so the space occupation requirements of the outlet channel are lower.
5. Unit control system differences
The unit control system of the low-voltage unit can generally be integrated on the side of the generator part on the fuselage, and the high-voltage unit generally requires an independent unit control box, which is arranged separately from the unit, considering signal interference.
6. Differences in maintenance requirements
The maintenance requirements of the high-voltage generator set in the oil circuit system and the intake and exhaust system are the same as those of the low-voltage unit, but the power distribution of the unit is a high-voltage system, and the maintenance personnel need to be equipped with a high-voltage induction certificate.
Economic comparison between high-voltage generating set and low-voltage generating set
If only the cost of the unit itself is considered, the cost of the high-voltage generator set is about 10% higher than that of the low-voltage generator set. If it is considered that there are few distribution cables for high-voltage units, and there are few switching points with the mains, and therefore saving on civil engineering costs, then high-voltage generating units
The overall cost of construction is lower than that of low-voltage generating units.