Our 69kV oil-immersed power transformer is designed for substations, industrial power systems, and renewable energy grid integration projects, delivering safe, efficient, and long-life voltage transformation performance. The capacity range covers 1MVA to 63MVA with fully customizable secondary voltage configurations.

Each unit is manufactured in strict compliance with IEC 60076, ANSI/IEEE C57.12.00, and CSA C88 standards. Every transformer undergoes complete factory acceptance testing (FAT) before shipment to ensure zero-defect operation from energization.

Why Choose a 69kV Oil-Immersed Transformer?

The 69kV voltage class plays a critical role in power systems, serving as a key interface between transmission and distribution networks. Compared with dry-type transformers, oil-immersed designs offer clear advantages in high-capacity applications.

Superior thermal performance: Mineral oil or natural ester provides excellent cooling for continuous overload operation
Longer service life: Designed lifespan of 30–40 years under proper maintenance
Higher short-circuit strength: Suitable for high fault-current power systems
Excellent maintainability: Supports oil processing and field repair to reduce downtime

Product Configurations

Two-Winding 69kV Step-Down Transformer

Widely used in utility substations and industrial systems for stable voltage conversion from 69kV to distribution levels.

Typical secondary voltages: 4.16kV / 6.9kV / 12.47kV / 13.8kV / 24.9kV / 34.5kV
Capacity range: 1MVA–63MVA
Tap changer: NLTC ±2×2.5% standard, OLTC optional
Vector group: YNd11 / Dyn11 / YNyn0
Cooling system: ONAN / ONAF / OFAF

Three-Winding 69kV Transformer

Designed for substations requiring dual secondary voltage outputs, reducing the need for multiple transformer units.

Configuration: 69kV / 13.8kV / 4.16kV
Capacity split: 100% / 100% / 50% (customizable)
Applications: Combined substations, cogeneration systems

69kV Autotransformer

Ideal for systems with grounded neutrals and voltage ratios not exceeding 3:1, offering lower cost and higher efficiency.

Voltage levels: 69kV / 34.5kV / 13.8kV
Capacity: up to 100MVA
Applications: Grid interconnection and transmission voltage support

Eco-Friendly Natural Ester Oil Transformer

Designed for fire-sensitive and environmentally regulated installations, using biodegradable vegetable-based insulation oil.

Flash point: >300°C (vs ~145°C mineral oil)
Biodegradability: >97% within 28 days
Compatible with standard insulation systems (paper-based insulation)
Suitable for indoor and environmentally sensitive locations

Technical Specifications

Rated voltage: 69kV
Secondary voltage: 4.16kV–34.5kV (customizable)
Frequency: 50Hz / 60Hz
Capacity range: 1MVA–63MVA
Cooling method: ONAN / ONAF / OFAF / OFWF
Insulation class: Oil-immersed Class A
Impedance voltage: 5.5%–8%
Tap range: ±8×1.25% (NLTC) / ±10% (OLTC)
Noise level: ≤58dB (ONAN)
Partial discharge: <80pC
Oil dielectric strength: >65kV
Service life: ≥30 years
Standards: IEC / ANSI / CSA / GB

Core Design Features

High-grade silicon steel core: CRGO laminated structure reduces losses and noise
Continuous disc winding: Enhances short-circuit mechanical strength and electrical stability
Fully sealed tank design: Minimizes oxidation and moisture ingress, extending insulation life
Optional OLTC system: Enables automatic voltage regulation under load

Protection & Monitoring System

Standard configuration: Buchholz relay, oil temperature indicator, winding temperature controller, oil level gauge, pressure relief valve, grounding system
Optional systems: Online DGA monitoring, fiber optic temperature sensing, seismic base frame, cooling fan control system

Applications

Power systems: Substations and distribution networks
Renewable energy: Wind farms and solar PV plants
Industrial systems: Steel, mining, cement, and petrochemical plants
Rail transit: Traction power and rectifier systems
Energy storage: Utility-scale BESS grid connection
Data centers: High-reliability redundant power systems

Testing & Quality Assurance

Each transformer undergoes full factory acceptance testing including: winding resistance, ratio test, impedance test, no-load loss test, AC withstand voltage test, partial discharge test, oil dielectric test, and moisture content analysis.

Third-party testing agencies: KEMA / CESI / CPRI / NEETRAC

Certifications

IEC 60076 series standards
ANSI/IEEE C57.12.00
CSA C88 standard
GB/T 6451 standard
ISO 9001:2015 quality system
CE certification
Third-party type test certification

Global Project References

Our 69kV transformers are operating in over 50 countries, including Canada grid interconnection systems, US data centers, Australian solar farms, South American transmission upgrades, and European distribution networks.

Frequently Asked Questions

Standard tap range: ±2×2.5% (NLTC), OLTC up to ±10% available

Supports both IEC and ANSI designs, including BIL 350kV insulation levels

Cooling options include ONAN and enhanced ONAF/OFAF systems

Shipping available with nitrogen or oil-filled transport packaging

Standard lead time: 12–22 weeks depending on configuration