6300kVA Three Phase Substation Power Transformer 66kV to 11kV OLTC for Utility

Engineered for reliable medium-voltage distribution, the 6300kVA 66kV/11kV three-phase oil-immersed power transformer is designed to handle demanding load cycles across utility substations, industrial facilities, mining operations, and major infrastructure. Manufactured in strict compliance with IEC 60076, it features high-grade copper windings and a Dyn11 vector group, delivering stable performance, efficient energy transfer, and long-term operational durability.

To counteract incoming grid fluctuations and variable site demand, an integrated On-Load Tap Changer (OLTC) allows real-time ratio adjustments without interrupting downstream power supply, maintaining a continuous, regulated 11kV output. This stability is complemented by an adaptive ONAN/ONAF cooling design—utilizing natural oil circulation for efficient standard operation, while enabling forced-air cooling to handle peak loads and enhance thermal capacity under heavy-duty conditions.

• 6300kVA Capacity for Power-Intensive Facilities

The 6.3 MVA rating supports centralized medium-voltage distribution for large industrial loads, mining facilities, infrastructure projects, and utility substations.

• Direct 66kV to 11kV Voltage Conversion

The transformer connects a 66kV transmission or sub-transmission supply directly to an 11kV distribution network, reducing the need for additional intermediate transformation stages.

• On-Load Voltage Regulation

The on-load tap changer supports voltage-ratio adjustment while the transformer remains energized, helping maintain stable downstream voltage during grid and load fluctuations.

• ONAN/ONAF Dual Cooling Capability

Natural oil and air cooling supports normal continuous operation, while forced-air cooling provides additional thermal capability when system loading increases.

• On-Load Tap Changer with Motor Drive — Live Voltage Adjustment
  Allows the transformer ratio to be adjusted under load, helping maintain a stable 11kV output as the incoming voltage or system demand changes.
• Oil Temperature Indicator — Top-Oil Temperature Monitoring
  Provides a direct reading of transformer oil temperature and can be configured with alarm and trip contacts for overheating protection.
• Winding Temperature Indicator — Load-Related Thermal Protection
  Monitors the simulated winding hot-spot temperature and supports fan control, high-temperature alarm, and trip functions.
• Magnetic Oil Level Gauge — Visible Oil Level Monitoring
  Displays the insulating oil level inside the conservator and provides early indication of abnormal oil loss or leakage.
• Buchholz Relay — Internal Fault Detection
  Detects gas accumulation and rapid oil movement caused by developing internal faults, providing alarm and trip protection.
• Pressure Relief Device — Tank Overpressure Protection
  Releases excessive internal pressure during a severe fault to help protect the transformer tank and connected components.
• Silica Gel Breather — Moisture Control for Conservator Air
  Removes moisture from incoming air as the oil volume expands and contracts, helping preserve insulating oil quality.
• Radiator Banks with Cooling Fans — ONAN/ONAF Heat Dissipation
  Provides natural oil and air cooling during normal operation, with fan-assisted cooling available for higher loading conditions.
• Marshalling and Control Cabinet — Centralized Auxiliary Connections
  Houses terminal blocks, temperature controls, fan circuits, alarms, and monitoring connections for easier commissioning and maintenance.
• Oil Drain, Filling and Sampling Valves — Convenient Oil Maintenance
  Supports oil filling, draining, filtration, and sample collection during factory testing, commissioning, and scheduled maintenance.
• Grounding Terminals — Secure Equipment Earthing
  Provides dedicated grounding points for the transformer tank, neutral circuit, and associated metallic components.
• Lifting, Jacking and Towing Provisions — Easier Site Handling
  Integrated lifting lugs, jacking pads, and towing points support transportation, positioning, installation, and maintenance.

1. With extensive experience in North American projects, Winley Electric designs substation transformers to meet applicable ANSI/IEEE, CSA, NEMA and related standard requirements.
2. With a stable supply chain, mature production processes, Winley Electric provides clear capacity-based lead times after technical approval: 8-10 weeks for transformers below 10 MVA, 10-12 weeks for 10-40 MVA transformers, and 18-20 weeks for 40-100 MVA transformers.
3. Winley Electric provides complete English technical documentation, 24/7 technical response, spare parts support, and a 2-year warranty to support project installation and long-term operation.

A: Winley provides clear capacity-based lead times after technical approval: 8-10 weeks for transformers below 10 MVA, 10-12 weeks for 10-40 MVA transformers, and 18-20 weeks for 40-100 MVA transformers. We also provide a detailed production schedule and real-time manufacturing photos to help track progress.We provide a detailed production schedule and real-time manufacturing photos to help track progress.

A: We offer a flexible MOQ of just 1 unit. Complete inquiries are quoted within 1-3 days with 24/7 support. Leveraging our extensive North American experience in renewable energy, data centers and large industrial projects, we ensure highly cost-effective and reliable solutions.

A: Yes, We accept OEM and ODM. Winley provides services for substation power transformers up to 100MVA, with HV systems up to 145kV. We can customize electrical parameters, structure, fluid, protection, switches, gauges, tank and paint according to customer drawings, with the capability to integrate components from brands like Qualitrol, Eaton Cooper, and MR.

A: Yes. Winley substation transformers are engineered and manufactured in strict accordance with ANSI/IEEE, CSA, NEMA, relevant ASTM standards and IEC 60076.We bring a proven track record across the United States and Canada, supporting critical applications in industrial manufacturing, renewable energy, and power distribution across a range of capacity and voltage requirements.

A: We deliver a complete compliance package: approval drawings, datasheets, nameplate drawings, routine test reports, installation manuals and accessory manuals. We also back your project with lifetime documentation support.

A: Winley ensures quality through strict ISO 9001 process management with dedicated QC oversight. Prior to delivery, every unit undergoes comprehensive routine testing, including Winding Resistance, Turns Ratio, Polarity and Phase Relation, and No-Load Loss and Excitation Current tests. We also fully support Factory Acceptance Testing (FAT) and third-party inspections (SGS).

A: Yes. Winley Electric provides tailored, fully controllable transportation solutions for large-scale transformer projects to ensure compliant customs clearance and zero-damage delivery. We actively assist in verifying critical logistics factors, including shipping dimensions, total weight, offloading conditions, site accessibility, and lifting/rigging requirements.

A: 24 months from B/L. During the warranty period, If there are any accessory problems, just provide photos of damaged accessory, then we will provide free service. According to the number of products, we will provide easily damaged accessories for free. We can also provide technical support if you need.