110 kV Oil-Immersed Transformer 2025 Procurement Guide: Parameters, Standards, and Technology Trends

With the rapid upgrading of transmission and distribution networks, the 110 kV oil-immersed transformer will continue to serve as a key piece of equipment in industrial power systems, urban expansion projects, renewable energy integration, and utility substations in 2025. For purchasers, understanding how to balance budget, performance, and long-term operating cost is critical when choosing among different brands, standards, and technical configurations. This guide analyzes core parameters, global standards, and upcoming technology trends to help buyers make accurate procurement decisions.

110 kV Oil-Immersed Transformer Core Parameters

When selecting a 110 kV oil-immersed transformer, purchasers must consider several essential parameters. These indicators directly affect the transformer’s lifespan, efficiency, loss levels, cooling capability, and operational stability.

1. Rated Capacity (MVA)

Typical capacity options include 20 MVA, 31.5 MVA, 40 MVA, and 50 MVA. Capacity selection should be based on load characteristics, expansion plans, and the overall grid layout.

2. Voltage Level and Tap Range

Common input and output voltage configurations include:

High-voltage side: 110 ± 8 × 1.25% kV
Low-voltage side: 10 kV, 11 kV, or 35 kV (depending on regional grid standards)

Most 110 kV oil-immersed transformers use an on-load tap changer (OLTC) to ensure voltage stability under varying load conditions.

3. Loss Indicators

Buyers should require certified test reports covering no-load loss, load loss, and no-load current. In 2025, demand continues to rise for low-loss, high-efficiency transformer cores, such as amorphous alloy cores and high-grade silicon steel.

4. Cooling Method

Common cooling configurations include ONAN (natural air cooling) and ONAF (forced air cooling). High-capacity transformers typically use a combined ONAN/ONAF mode to maintain safe temperature rise.

5. Insulation Materials and Insulation Oil

Insulation materials include epoxy pre-impregnated paperboard and DMD insulating composites. Oil-immersed transformers usually use mineral insulating oil meeting IEC 60296 standards. In 2025, natural ester insulating oil is expected to gain wider adoption due to its environmental benefits and higher flash point.

110 kV Oil-Immersed Transformer Standards

To ensure reliability, operational safety, and testing consistency, 110 kV oil-immersed transformers must comply with both international and national standards:

International Standards

IEC 60076 series: Global baseline standards covering technical requirements, testing procedures, and operational conditions for power transformers.

Chinese National Standards (GB/T)

GB/T 6451: Technical specifications for 110 kV transformers.
GB 20052: Energy efficiency grading—critical for 2025 procurement, requiring Level 1 high-efficiency transformer performance.
GB/T 1094 series: National standards equivalent to IEC 60076.

Procurement Tip: Prioritize manufacturers whose oil-immersed transformers comply with both IEC and GB standards for higher compatibility and export readiness.

2025 Technology Development Trends

Traditional transformer designs are losing competitiveness. In 2025, purchasers should focus on the following emerging trends when selecting oil-immersed transformers:

1. Ultra-High Energy Efficiency & Low Carbonization

Amorphous alloy core transformers can reduce no-load loss by 60–70% compared to traditional silicon steel models—significantly lowering lifecycle energy consumption.

2. Intelligent Monitoring & Digitalization

Modern oil-immersed transformers increasingly feature built-in online monitoring systems for real-time analysis of dissolved gas in oil (DGA), winding temperature, partial discharge, and bushing dielectric losses.

3. Enhanced Environmental Protection & Safety

Natural ester insulating oil (vegetable oil) is gaining popularity due to its high ignition point (>300°C), biodegradability, and non-toxicity—ideal for indoor substations, renewable energy facilities, and offshore power platforms.

4. Digital Twin & Lifecycle Management

Manufacturers now offer digital twin models containing design, manufacturing, testing, and operational data. These models support fault prediction, performance optimization, and full lifecycle management.

The 110 kV oil-immersed transformer remains an essential component of modern power systems. In 2025, procurement will shift toward high-efficiency, intelligent, and environmentally friendly equipment. Purchasers should fully evaluate load demand, technical standards, supplier capability, and lifecycle operating cost to select reliable and long-lasting oil-immersed transformers.