3000 KVA IEC 60076 Power Transformers-88/11 KV | South Africa 2025

Earthing Transformer by SCOTECH: Built for Global Power Grid Reliability.

01 General

1.1 Project Description

3000 kVA earthing transformer was delivered to South Africa in 2025. The rated power of the transformer is 3000 kVA with ONAN cooling. The primary voltage is 88 kV with ±2*2.5% tapping range (NLTC), the secondary voltage is 11 kV, they formed a vector group of Dyn11.

Designed to operate in harsh environments with an altitude range of 0-1800M, a temperature range of -5℃ to +45℃, and heavy pollution (saline or industrial smoke), this transformer integrates robust performance and specialized configurations to meet the demands of traction substation power supply systems.

With a rated capacity of 3MVA and a voltage ratio of 88/11kV (frequency 50±2.5HZ), the transformer adopts copper windings for superior conductivity and mechanical strength, paired with ONAN cooling mode and Dyn11 connection. Key electrical parameters include a minimum impedance of 8%, NLTC on-load tap-changer (±2*2.5%, padlockable), and no-load/load losses of 3.9kW/20kW, ensuring efficient and stable operation. It is equipped with a comprehensive protection system, including single-float gas relay (with alarm and trip contacts), overload thermal relay (environmentally compensated, set at 115℃), pressure relief valve, and adjustable contact oil surface thermometer (triggering at 90℃), providing multi-layered safety guarantees.

Structurally, the transformer features a welded tank made of ≥6mm steel plate (16mm base plate) and detachable hot-dip galvanized radiators, with a gray tank and white conservator (125μm coating for heavy pollution areas). It is designed without rollers but with a sturdy base compatible with 1000mm-spaced steel slides, and meets IP55 protection for the terminal box. The live parts maintain a 3500mm ground clearance, and all bushings, rods, and terminals (≥19mm for primary/secondary connections) ensure sufficient mechanical strength. Additionally, the transformer is engineered to withstand up to 27% total voltage harmonic distortion on the low-voltage winding, making it ideal for 11kV and 6.6kV transmission line systems in traction substations.

1.2 Technical Specification

3000kVA IEC 60076 power transformers specifications type and data sheet

1.3 Drawings

3000 kVA traction transformer diagram drawing and size.

02 Manufacturing

2.1 Tank

The tank of the 3MVA-88/11kV IEC 60076 power transformers features a welded design compatible with detachable hot-dip galvanized radiators, constructed from ≥6mm steel plate (16mm-thick base plate). It is equipped with bolted inspection covers/manholes with gasket seals and robust handles, and comes without rollers but with a sturdy base for mounting on 1000mm-spaced steel slides embedded in concrete. Painted gray with a 125μm coating for heavy pollution areas, the tank also includes an external earthing terminal for connecting 95mm² cables, ensuring reliability and adaptability to harsh operating conditions.

2.2 Thermometers

The 3MVA-88/11kV IEC 60076 power transformers is equipped with two thermometers: a dial-type oil surface thermometer with adjustable contacts (usually set to operate at 90℃) and trip contacts rated for 110V DC, 6A (auxiliary relay optional if needed), and an overload thermal relay (serving as a winding thermometer) featuring ambient temperature compensation, a load-temperature correlation, and trip contacts preset at 115℃ with the same 110V DC, 6A rating.

2.3 Control Box

This earthing transformer’s control box is a robust stainless steel enclosure with an openable, latched door. Inside, it houses terminal blocks, small control components (e.g., relays/instruments), and labeled wiring; externally, an “Exe-G2” marking is displayed on a connected conduit, while corrugated cable glands at the bottom enable tidy wiring entry, supporting the unit’s operational control and signal transmission.

2.4 Detachable Hot-Dip Galvanized Radiator

The 3MVA-88/11kV IEC 60076 power transformers is equipped with detachable hot-dip galvanized radiators: these corrosion-resistant, zinc-coated components connect to the unit’s welded tank, pair with the ONAN cooling system to efficiently dissipate operational heat, and can be removed easily for maintenance-making them well-suited to the transformer’s harsh, heavy-pollution operating conditions.

2.5 LV Bushing

The low-voltage porcelain bushing for the earthing transformer features a sturdy, glazed porcelain insulator. It is typically flange-mounted on the transformer tank, with its lower terminal stud directly extending into or cast within an attached, fully encapsulated cable termination box. This integrated design provides a robust, sealed, and protected transition from the transformer winding to the external power cables, ensuring a reliable and maintenance-friendly connection point.

2.6 Oil Sampling Valve

Crafted from brass, it offers good corrosion resistance and sealing reliability, which aligns with the transformer oil’s operating medium. As a key part of routine maintenance and condition monitoring, this valve allows operators to conveniently extract insulation oil samples: these samples are then tested for indicators like insulation performance, water content, and impurity levels, helping to timely assess the oil’s quality and the internal operational health of the transformer. Its compact, sealed design not only maintains the tightness of the oil system but also enables quick, straightforward operation.

03 Testing

The Auxiliary Wiring Insulation Test verifies the integrity of all secondary control and monitoring circuits (e.g., for temperature indicators, alarms, or fan controls) by applying a DC voltage, typically 500V or 1000V, between the bundled wiring and earth. The measured insulation resistance, which must exceed a specified minimum threshold (often 1-5 MΩ), ensures there are no harmful ground faults or moisture-induced leakage paths that could compromise the reliability of the protection and monitoring systems, thereby safeguarding the transformer’s ancillary functions.

04 Packing and Shipping

05 Site And Summary

In summary, the earthing transformer serves as a critical component in modern power systems, ensuring safety, stability, and reliability. By providing a defined neutral point for grounding, it effectively manages fault currents, limits overvoltages, and enhances the protection of both equipment and personnel. Its role is indispensable in maintaining system balance and preventing damage during unbalanced or fault conditions. As power networks continue to evolve, the importance of robust and well-designed earthing solutions remains paramount for sustainable and secure electrical infrastructure.