Seven considerations for transformer selection - Solutions - Huaqiang Electronic Network

inductance

(1) It is essential to use transformers from manufacturers with a proven track record of high reliability to avoid the inclusion of substandard or obsolete products in the power system. The selection of the factory should be based on its failure and repair rates. The product must be certified by a national authorized institution, and it should have passed the type test report approved by an official national authority.

(2) For oil-immersed transformers rated at 110kV and above, full sealing with metal expanders is recommended. Manufacturers should strictly monitor and manage the quality of insulating oils. High-quality oils should be selected according to national or industry standards, and the oil sources should meet the specific requirements of the ordering party. It is also important to ensure that oil injection equipment is of good quality, and to address issues such as excessive hydrogen and methane levels in current transformers after operation.

(3) Capacitive voltage transformers should include ferromagnetic resonance tests as part of their routine testing. The test voltages should be set at 0.8U and 1.2U (where U represents the rated primary phase voltage). To prevent resonant overvoltage, medium-voltage end arresters should be used. This helps ensure the transformer's stability under various operating conditions.

(4) Porcelain-insulated transformers should be selected based on the size of the umbrella skirts to ensure sufficient creepage and insulation distance. This is crucial for meeting environmental conditions, especially in areas prone to rain and flashovers.

(5) The support structure for SF6 gas-insulated transformers and the connection points of the capacitive screen should be securely fastened to prevent malfunctions during transportation. When using silicone rubber for external insulation, it is vital to ensure the quality of the casting to avoid potential accidents.

(6) For solid insulation transformers, the manufacturer must ensure that the resin fully penetrates the primary winding layers to prevent any internal faults. Indoor models should pass pollution condensation tests to meet environmental requirements, while outdoor models should undergo rigorous assessments including rain, temperature extremes, and UV exposure to ensure they can withstand harsh outdoor conditions.

(7) The dynamic thermal stability factor of the transformer should be determined based on the power grid development plan to accommodate future growth. Special attention must be given to the dynamic thermal stability of small current ratio transformers, as these are more susceptible to overheating under certain conditions.