What impact does altitude have on the operation of transformers?

In areas where the altitude does not exceed 1000 meters, transformers can operate without considering the altitude factor. However, in regions with altitudes above 1000 meters, transformers must take into account the impact of thin air on heat dissipation and the stability of external insulation materials.

As a result, transformers used in areas with altitudes above 1000 meters must specify the actual altitude of the operating location in the contract. This is to enable the manufacturing plant to consider the temperature rise limits and the minimum air clearances for external insulation. Typically, manufacturers address the requirements of high-altitude areas by reinforcing the external insulation of bushings, increasing the leakage distance along surfaces and clearance to ground, and enlarging the air clearances between bushings and grounding components. If the manufacturing plant is located at a normal altitude, adjustments to the temperature rise limits for high-altitude transformers can be made by lowering the specified temperature rise limits.

Regarding the average temperature rise limits for windings, when the altitude exceeds 1000 meters, the temperature rise decreases by 1K for oil-immersed self-cooled transformers every 400 meters, by 1K for oil-immersed forced-air-cooled transformers every 250 meters, by 2.5% for dry-type self-cooled transformers every 500 meters, and by 5% for dry-type forced-air-cooled transformers.

If the environmental temperature at the high-altitude operating location provided by the user department is lower than the normally specified environmental temperature and decreases by 5°C or more for every 1000 meters of altitude, it is considered that the increase in temperature rise due to reduced heat dissipation conditions at high altitudes is compensated by the lower environmental temperature. For transformers intended for high-altitude areas, there is no need to adjust the temperature rise limits during the factory tests conducted at normal altitudes. This can be explicitly stated in the contract, making the transformers more economical and cost-effective.

For oil-immersed transformers, the external insulation distance increases by 1% for every additional 100 meters beyond 1000 meters, while dry-type transformers increase the rated short-time withstand voltage value by 6.25% for every additional 500 meters beyond 1000 meters.

LuShan, est. 1975, is a Chinese professional manufacturer specializing in power transformers and reactors for 49 years. Leading products are single-phase transformer, three-phase transformers, DC inductors, AC reactors, filtering reactor, expoxy resin high-voltage transformer and intermediate, high-frequency products. Our transformers and reactors are widely used in 10 application areas: rapid transit, construction machinery, renewable energy, intelligent manufacturing, medical equipment, coal mine explosion prevention , excitation system, vacuum sintering, central air conditioning.

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