The iron core of the dry-type power transformer is made of high-quality grain-oriented cold-rolled silicon steel sheet with high magnetic permeability, with 45° fully inclined stepping joints.
The iron core of the dry-type power transformer is made of high-quality grain-oriented cold-rolled silicon steel sheet with high magnetic permeability, with 45° fully inclined stepping joints. The iron core adopts a special square tube drawing plate structure, and the core columns are bound with insulating tape. It is coated with special resin to prevent moisture and rust, effectively reducing no-load loss, no-load current and iron core noise. Dry-type transformers are widely used in urban power grid transformation, residential quarters, high-rise buildings, industrial and mining, hotels, shopping malls, airports, railways, oil fields, docks, expressways, commercial centers, light stations, factories and mines, enterprises, hospitals, schools, etc. and temporary In places such as electrical equipment, dry-type transformers simply refer to transformers whose iron core and windings are not immersed in insulating oil.
Cooling methods are divided into natural air cooling (AN) and forced air cooling (AF). It should not be placed in continuous overload operation for a long time.
Form: open closed pouring column
Usage frequency: 50 / 60HZ
Structure type: It is mainly composed of an iron core composed of silicon steel sheets and a coil casted by epoxy resin. An insulating cylinder is placed between the high and low voltage coils to increase electrical insulation, and the coil is supported and restrained by pads. loose performance.
Structural features
Due to the advantages of strong short-circuit resistance, small maintenance workload, high operating efficiency, small size, and low noise, dry-type transformers are often used in places with high performance requirements such as fire prevention and explosion protection. the
1. Safety, fire prevention, no pollution, can run directly in the load center;
2. Adopt domestic advanced technology, high mechanical strength, strong short-circuit resistance, small partial discharge, good thermal stability, high reliability and long service life;
3. Low loss, low noise, obvious energy saving effect, maintenance-free;
4. Good heat dissipation performance, strong overload capacity, and can increase capacity operation when forced air cooling;
5. Dry-type transformers can be equipped with a complete temperature detection and protection system. The intelligent signal temperature control system is adopted, which can automatically detect and display the working temperature of the three-phase windings, and can automatically start and stop the fan, and has functions such as alarm and trip;
7. Small size, light weight, less space occupation, low installation cost.
Temperature control system
The safe operation and service life of dry-type transformers depend largely on the safety and reliability of transformer winding insulation. The winding temperature exceeds the insulation withstand temperature and the insulation is damaged, which is one of the main reasons for the transformer not to work normally. Therefore, it is very important to monitor the operating temperature of the transformer and its alarm control.
(1) Fan automatic control: The temperature signal is measured by the Pt100 thermistor temperature measuring resistor embedded in the hottest part of the low-voltage winding. The transformer load increases and the operating temperature rises. When the winding temperature reaches 110°C, the system will automatically start the fan for cooling; when the winding temperature is as low as 90°C, the system will automatically stop the fan.
⑵Over-temperature alarm and trip: collect winding or core temperature signals through the PTC nonlinear thermistor temperature measuring resistor embedded in the low-voltage winding. When the temperature of the transformer winding continues to rise, if it reaches 155°C, the system will output an over-temperature alarm signal; if the temperature continues to rise to 170°C, the transformer cannot continue to operate, and an over-temperature trip signal must be sent to the secondary protection circuit, and the transformer should be activated. Quick trip.
Temperature display system: Measure the temperature change value through the Pt100 thermistor embedded in the low-voltage winding, and directly display the winding temperature of each phase (three-phase inspection and maximum value display, and record the highest temperature in history). The temperature is output by 4 ~ 20mA analog quantity, if it needs to be transmitted to a remote (up to 1200m) computer
Protection method
Usually, IP20 protective shell is used to prevent the entry of solid foreign objects and small animals such as rats, snakes, cats, birds, etc., which may cause vicious faults such as short circuit and power failure, and provide a safety barrier for live parts. If the transformer must be installed outdoors, an IP23 protective enclosure can be selected. In addition to the above-mentioned IP20 protection function, it can also prevent water dripping within 60° from the vertical line. However, the IP23 enclosure will reduce the cooling capacity of the transformer, so attention should be paid to the reduction of its operating capacity when selecting it.
Application status
Since there is no oil in the dry-type transformer, there are no problems such as fire, explosion, and pollution. Therefore, electrical codes and regulations do not require dry-type transformers to be placed in separate rooms. Loss and noise have been reduced to a new level, creating conditions for transformers and low-voltage screens to be placed in the same power distribution room.
Examination
1. Whether there is abnormal sound and vibration.
2. Whether there is any discoloration caused by local overheating, harmful gas corrosion, etc., which cause creepage traces and carbonization on the insulating surface.
⒊Whether the air-cooling device of the transformer is operating normally.
⒋The high and low voltage joints should not be overheated. The cable head should have no leakage or creepage.
5. The temperature rise of the winding should be based on the grade of insulating material used by the transformer, and the temperature rise of the monitoring should not exceed the specified value.
6. There should be no cracks or discharge traces in the supporting porcelain bottle.
7. Check whether the winding pressing parts are loose.
⒏Indoor ventilation, iron core air duct should be free from dust and sundries, and iron core should not be rusted or corroded.