Dry-Type vs Oil-Filled 35kV New Energy Transformers: Cost and Performance Comparison

For users, when purchasing a 35kV new energy transformer, choosing between dry-type, mineral oil-filled, or vegetable oil-filled types involves multiple considerations. These include user habits, maintenance-free performance, safety and fire resistance, volume and weight, among others. However, cost differences are undoubtedly one of the most crucial factors.

To illustrate the issue intuitively, this paper selects a three-level energy efficiency dual-winding new energy transformer with a rated capacity of 3150kVA and a rated voltage of 37kV as an example for quantitative calculation and qualitative analysis.

Basic Parameters of the Product

• Rated Capacity: 3150 / 3150kVA

• Voltage Ratio: 37±2×2.5%/0.8kV

• Connection Group: Dyn1

• Short-Circuit Impedance: 7%

• Energy Efficiency Class: Class 3

Differences in Material Costs

Based on the same basic technical parameters and energy efficiency class mentioned above, and combined with current market prices of raw materials (copper at 80,000 yuan/ton), the differences in tax-included material costs of 3150 kVA / 37kV dual-winding new energy transformers—for dry-type, mineral oil-filled, and vegetable oil-filled types—are calculated as follows.

It should be specially noted that for dry-type and oil-immersed transformers with the same capacity, voltage class, and energy efficiency class, their respective limits for no-load loss and load loss are different.

Cost Comparison Conclusion：For the 3150 kVA / 37 kV dual-winding new energy transformer, under the same level 3 energy efficiency, the dry-type transformer has the highest cost—about 45% higher than the mineral oil-filled transformer. In contrast, the vegetable oil-filled transformer offers better cost - effectiveness, with a cost only about 7.5% higher than that of the mineral oil-filled transformer.

Comprehensive Performance Comparison

To help users reasonably select the product type of 35kV - class new energy transformers based on the budgets and technical requirements of actual engineering projects, the qualitative comparison conclusions are presented in the following table.

That is, dry-type transformers have significant advantages in terms of floor space, maintenance-free property, safety and fire resistance, short-circuit withstand capability, etc., while oil-immersed transformers have obvious advantages in aspects such as actual operation energy consumption, one-time purchase cost, and whole-life-cycle operation cost.