What are the significant advantages of Oil-immersed transformers compared to Dry-type transformers?

Compared to Dry-type transformers, Oil-immersed transformers offer significant advantages primarily in capacity and voltage rating, heat dissipation and overload protection, operating efficiency, procurement costs, and environmental adaptability.

• Larger capacities and voltage levels are possible.

Oil-immersed transformers rely on oil circulation for insulation and heat dissipation, eliminating the resin/air bottleneck of dry-type transformers. Therefore:

Single unit capacity: Dry-type transformers typically reach 2500-3150 kVA as the mainstream upper limit, while Oil-immersed transformers can easily reach tens or even hundreds of MVA.

Voltage levels: Dry-type transformers commonly reach 35 kV, while Oil-immersed transformers can reach 110 kV, 220 kV, and even higher, making them the mainstay of power transmission and distribution networks.

In short: For large-capacity, high-voltage applications, Oil-immersed transformers are almost the only option.

• Strong heat dissipation and overload capacity

Transformer oil has a much higher specific heat capacity and thermal conductivity than air. Combined with oil convection/forced oil circulation, it can quickly dissipate heat from the windings.

Short-term overload capacity is significantly stronger than dry-type transformers (higher thermal inertia, more easily withstands impact loads).

During long-term high load rate operation (≥75%), winding temperature rise control is more stable, and it is less likely to be forced to shut down or derating by temperature management strategies.

• Superior operating efficiency (especially under high load conditions)

Lower Pk (load loss) at actual operating temperatures: oil cooling ensures uniform temperature distribution, and winding resistance doesn't spike with localized hot spots like in dry-type systems.

In scenarios with prolonged high loads and long operating times, oil-cooled transformers typically offer lower overall losses (electricity costs) than dry-type systems.

Furthermore, the amorphous alloy oil-cooled transformer route allows for extremely low Po (no-load loss), making it a crucial option for achieving "ultimate efficiency," while dry-type amorphous transformers are limited by heat dissipation constraints, resulting in a much narrower application range.

• Lower Procurement Costs for the Same Capacity

For the same capacity, the price of hydraulic substations is generally significantly lower than that of dry-type substations. The larger the capacity, the more substantial the absolute price difference.

For large-capacity substations (e.g., ≥1600 kVA), there are fewer dry-type models to choose from, while hydraulic substations offer a wider selection, mature competition, and superior cost-effectiveness.

• Lower operating noise

Oil dampens vibrations in the core and windings, and combined with the inherent buffering effect of outdoor/panel-mounted substations, oil-cooled substations typically operate 5-10 dB quieter than dry-type substations.

In noise-sensitive environments, oil-cooled substations are actually more suitable.

• Enhanced environmental adaptability (outdoor-oriented)

Good weather resistance: Unaffected by low temperatures (oil won't freeze and crack), and can withstand high temperatures thanks to its heat dissipation design; wider temperature range than dry-type systems.

For outdoor platforms, transformer substations, mountainous areas, and rural power grids—scenarios where there is "no one to manage the environment and the conditions are harsh"—oil-type systems are more robust.