Oil-Immersed Traction Transformer for Electrified Railway & Rail Transit Networks

Pearl Electric’s high-performance oil-immersed traction transformers are specifically designed for railway electrification systems, metro networks, high-speed railways, and urban rail transit substations. Engineered to provide stable, continuous power to traction loads, these transformers maintain exceptional reliability even under conditions of frequent load fluctuations, overloads, and high harmonic content. Utilizing advanced ONAN/ONAF cooling technology (with vegetable or mineral oil) and high-purity oxygen-free copper windings, the products comply with international standards for railway and power transformers; they feature superior short-circuit withstand capability and extremely low operating losses, ensuring a continuous and safe power supply for vital rail transit networks.

This series of traction transformers offers customizable voltage and capacity specifications to meet project requirements and is suitable for both single-phase and three-phase traction substations. Constructed with high-quality grain-oriented silicon steel cores, high-conductivity copper windings, and advanced oil cooling technologies (ONAN/ONAF/OFAF), the transformers are characterized by low losses, excellent short-circuit withstand capability, and a long service life.

Product Parameters

Features of Oil-Immersed Traction Transformer

Optimized for Railway Traction Systems: Specifically designed for railway electrification projects, providing stable voltage transformation for metro, intercity, freight, and high-speed rail networks.

High Short-Circuit Withstand Capability: The windings feature an integrated radial and axial clamping structure, supported by high-density pressboard and laminated wood, ensuring exceptional mechanical stability to withstand the frequent, sudden short-circuit events common in railway operations.

High Overload Capacity: Engineered to handle the fluctuating load characteristics of traction systems (such as train startup and hill climbing), the design meets IEC standards for frequent overload capabilities (e.g., 1.5x overload for 15–30 minutes, 2x overload for 2 minutes) without compromising the transformer's expected service life.

Low Loss and High Energy Efficiency: Utilizes high-quality, high-permeability silicon steel sheets and a stepped, fully mitered core stacking structure to significantly reduce no-load losses and no-load current, while also lowering operating noise.

Harmonic Tolerance and Optimization: Windings and insulation structures are specifically reinforced to withstand high-order harmonics (such as the 3rd, 5th, and 7th harmonics) generated by power-electronic traction locomotives, preventing localized overheating and insulation aging caused by harmonic interference. 

Fully Sealed, Long-Life Design: Features either a diaphragm-type oil conservator or a fully sealed corrugated tank, completely isolating the transformer oil from the atmosphere; this effectively prevents moisture and oxygen ingress, slows oil aging, and extends maintenance intervals. 

Eco-friendly and Safety Options: Available in models filled with eco-friendly vegetable oil (FR3). Vegetable oil offers a high fire point (>360°C) and self-extinguishing properties, significantly enhancing fire safety for substations in underground railways and densely populated areas.

Advantages of Oil-Immersed Traction Transformer

Ensuring Uninterrupted Railway Operations: Designed for exceptional industrial reliability, the unit minimizes the risk of train service disruptions caused by sudden grid failures, thereby ensuring efficient and punctual railway transport capacity.

Ultra-Low Life-Cycle Cost (LCC): Thanks to designs that reduce losses and extend maintenance intervals, the equipment’s total operating and maintenance costs are significantly lower than those of standard transformers.

All-Environment Adaptability: The enclosure features a heavy-duty anti-corrosion coating (such as high-solids epoxy zinc-rich paint) or is constructed from stainless steel, effectively resisting corrosion from coastal salt spray, heavy industrial pollution, and the specific dust-laden environments found along railway lines.

Smart Scalability: The unit supports the integration of modern smart sensors—including fiber-optic temperature monitoring, online dissolved gas analysis (DGA), and vibration and partial discharge monitoring systems—facilitating digital operations and predictive maintenance for smart railway networks.

Applications of Oil-Immersed Traction Transformer

High-Speed ßRailway (HSR) Traction Substations: Provide highly stable, high-capacity power support for high-speed trains operating at speeds of 250 km/h and 350 km/h+.

Conventional Electrified Railways: Suitable for substations serving mainline freight and passenger railways, capable of withstanding the high-load surges associated with heavy-haul trains.

Urban Rail Transit: Suitable for surface or underground main substations in metro and light rail systems, providing core step-down voltage conversion for AC power supply networks.

Industrial and Mining Private Railways: Offer customized traction power network solutions for electric locomotive transport lines within large steel plants and mining operations.

This transformer is an ideal choice for railway authorities, metro operators, EPC contractors, utility companies, and transport infrastructure developers seeking reliable, high-performance traction power supply solutions.

FAQs of Oil-Immersed Traction Transformer

Q1: What are the key differences between traction transformers and standard power transformers?

A: Traction transformers are subjected to highly dynamic loads (frequent starting, braking, and cycling between no-load and full-load conditions) and frequent external short-circuit stresses. Consequently, their design standards regarding winding mechanical strength, short-circuit withstand capability, harmonic tolerance, and overload performance are significantly higher than those of traditional power transformers designed for steady-state operation.

Q2: Can the transformer be customized?

A:Yes. Pearl Electric can customize voltage ratings, capacity, vector groups, impedance, tap changers, protection devices, insulating oil types, cooling systems, and enclosure designs according to customer specifications.

Q3: What tests are performed before the product leaves the factory to ensure reliability?

A: Every transformer undergoes a full suite of routine tests in strict accordance with IEC 60076 standards before leaving the factory. In addition, given the specific characteristics of traction transformers, we conduct lightning impulse tests, partial discharge (PD) tests, and temperature rise tests, as well as rigorous inspections for mechanical strength and airtightness.

Q4: What advantages does vegetable insulating oil (FR3) offer compared to traditional mineral oil?

A: Vegetable oil has a high fire point of 360°C (compared to only about 160°C for traditional mineral oil), offering exceptional fire and explosion safety; it is classified as a less-flammable liquid. Furthermore, vegetable oil is 100% biodegradable and environmentally friendly, and it effectively extends the service life of the winding insulation paper.