[b]I. Temperature Control System for Dry-Type Transformers[/b] The safe operation and service life of dry-type transformers largely depend on the safety and reliability of the transformer winding insulation. Winding temperature exceeding the insulation withstand temperature, leading to insulation failure, is one of the main reasons why transformers cannot operate normally. Therefore, monitoring the operating temperature of the transformer and its alarm control are very important. (1) Automatic Fan Control: Temperature signals are measured by a Pt100 thermistor embedded in the hottest part of the low-voltage winding. As the transformer load increases and the operating temperature rises, the system automatically starts the fan for cooling when the winding temperature reaches 110℃; when the winding temperature drops to 90℃, the system automatically stops the fan. (2) Over-temperature Alarm and Trip: Winding or core temperature signals are collected by a PTC nonlinear thermistor embedded in the low-voltage winding. When the transformer winding temperature continues to rise, if it reaches 155℃, the system outputs an over-temperature alarm signal; if the temperature continues to rise to 170℃, the transformer can no longer operate and an over-temperature trip signal must be sent to the secondary protection circuit to make the transformer trip quickly. (3) Temperature display system: The temperature change value is measured by the Pt100 thermistor embedded in the low voltage winding, and the temperature of each phase winding is directly displayed (three-phase inspection and maximum value display, and the historical highest temperature can be recorded). The highest temperature can be output as a 4-20mA analog signal. If it is necessary to transmit to a computer at a distance (up to 1200m), a computer interface can be added. One transmitter can monitor up to 31 transformers at the same time. The system's over-temperature alarm and trip can also be activated by the Pt100 thermistor signal, further improving the reliability of the temperature control protection system. [b]II. Protection methods for dry-type transformers[/b] According to the characteristics of the usage environment and protection requirements, different shells can be selected for dry-type transformers. Usually, an IP20 protective shell is selected to prevent solid foreign objects with a diameter greater than 12mm and small animals such as rats, snakes, cats, and sparrows from entering and causing serious faults such as short circuits and power outages, providing a safety barrier for live parts. If the transformer must be installed outdoors, an IP23 protective enclosure can be selected. In addition to the IP20 protection function mentioned above, it can also prevent water droplets from entering at an angle of up to 60° to the vertical. However, an IP23 enclosure will reduce the transformer's cooling capacity; therefore, attention should be paid to the reduction in its operating capacity when selecting one. [b]III. Cooling Methods of Dry-Type Transformers[/b] Dry-type transformers are cooled by natural air cooling (AN) and forced air cooling (AF). With natural air cooling, the transformer can operate continuously at its rated capacity for extended periods. With forced air cooling, the transformer's output capacity can be increased by 50%. This is suitable for intermittent overload operation or emergency overload operation. Because the load loss and impedance voltage increase significantly during overload, it is in an uneconomical operating state and should not be subjected to prolonged continuous overload operation. [b]IV. Overload Capacity of Dry-Type Transformers[/b] The overload capacity of a dry-type transformer is related to the ambient temperature, the load conditions before overload (initial load), the transformer's insulation and heat dissipation, and the heating time constant. If necessary, the overload curve of the dry-type transformer can be obtained from the manufacturer. How can its overload capacity be utilized? The author offers two points for reference: (1) When selecting and calculating the transformer capacity, it can be appropriately reduced: fully consider the possibility of short-term impact overload of certain equipment such as steel rolling and welding - make the best use of the strong overload capacity of dry-type transformers to reduce the transformer capacity; for some uneven load places, such as residential areas mainly for nighttime lighting, cultural and entertainment facilities, and shopping malls mainly for air conditioning and daytime lighting, their overload capacity can be fully utilized to appropriately reduce the transformer capacity so that its main operating time is at full load or short-term overload. (2) The standby capacity or number of units can be reduced: in some places, the standby coefficient of transformers is required to be high, which makes the transformer capacity and number of units selected for the project large. However, by utilizing the overload capacity of dry-type transformers, their standby capacity can be compressed when considering them; the number of standby units can also be reduced. When the transformer is running under overload, it is necessary to pay attention to monitoring its operating temperature: if the temperature rises to 155℃ (an alarm is issued), load reduction measures should be taken (reducing some secondary loads) to ensure the safe power supply to the main load. [b]V. Low-Voltage Outgoing Line Methods and Interface Coordination of Dry-Type Transformers[/b] Because dry-type transformers do not contain oil, they eliminate the risks of fire, explosion, and pollution. Therefore, electrical codes and regulations do not require dry-type transformers to be placed in separate rooms. Losses and noise levels have been reduced to new levels, creating conditions for placing transformers and low-voltage switchboards in the same distribution room. Currently, my country's annual production of resin-insulated dry-type transformers has reached 10,000 MVA, making it one of the world's largest producers and sellers of dry-type transformers. With the widespread application of the low-noise (noise of distribution transformers below 2500kVA is controlled below 50dB) and energy-saving (no-load loss reduced by up to 25%) SC(B)9 series, the performance indicators and manufacturing technology of my country's dry-type transformers have reached world-class levels. The National Building Standard Design Atlas "Dry-Type Transformer Installation" - "99D268" provides layout and installation methods for dry-type transformers suitable for various locations, and lists multiple schemes for the interface coordination between transformers and low-voltage switchboards for design and construction selection. With the widespread application of dry-type transformers, their manufacturing technology has also made great strides. Dry-type transformers will be further developed in the following aspects: (1) Energy saving and low noise: With the introduction of new low-consumption silicon steel sheets, foil winding structures, stepped core joints, environmental protection requirements, noise research, and computer optimization design, the future dry-type transformers will be more energy-efficient and quieter. (2) High reliability: Improving product quality and reliability will be the unremitting pursuit of people. A large amount of basic research will be carried out in electromagnetic field calculation, wave process, casting process, hot spot temperature rise, partial discharge mechanism, quality assurance system and reliability engineering, and reliability certification will be actively carried out to further improve the reliability and service life of dry-type transformers. (3) Environmental protection characteristic certification: Based on the European standard HD464, research and certification of the weather resistance (C0, C1, C2), environmental resistance (E0, E1, E2) and fire resistance (F0, F1, F2) characteristics of dry-type transformers will be carried out. (4) Large capacity: From dry-type transformers mainly consisting of 50-2500kVA distribution transformers to 10000-20000kVA/35kV power transformers. With the continuous increase in urban electricity load, urban power grid substations are increasingly penetrating into urban centers, residential areas, large factories and mines, and other load centers. 35kV large-capacity community center power supply transformers will be widely used. (5) Multifunctional combination: From single transformers to multifunctional combined transformers with air cooling, protective shells, temperature computer interfaces, zero-sequence transformers, power metering, enclosed busbars and side-outgoing lines. (6) Multi-field development: From distribution transformers as the main focus to special transformers and multi-purpose fields such as power plant auxiliary transformers, excitation transformers, subway traction rectifier transformers, high-current electric furnace transformers, nuclear power plants, marine and oil platform transformers. Distribution transformers will be high-performance, low-noise and energy-saving resin-insulated dry-type transformers.