IEC Oil-Immersed Zigzag Earthing Transformer Manufacturer-11kV to 35kV

Summary: Repurposed ordinary three-phase transformers are NOT recommended for MV distribution neutral earthing. Rockwill Zig-zag earthing transformer is purpose-built for short-time single-phase earth faults with stable zero-sequence characteristics, offering reliable artificial neutral point for distribution networks.

Yes. Rockwill support full OEM / ODM cooperation. We select partners rigorously, prioritizing system integrators with power engineering capability, local delivery and after-sales service. Ideal partners are not only distributors, but also capable of local technical support to jointly deploy neutral earthing packages.

Rockwill provides industry-leading warranty for earthing transformers:

10-year+ full-unit warranty covering core, ZN windings, tank/enclosure and sealing components.

We offer free repair or replacement of defective parts for failures caused by material or manufacturing defects within warranty period. Damage caused by human error, system overvoltage or operation exceeding the nameplate short-time fault duty is excluded. Terms are clear with no hidden clauses.

This guarantee is backed by years of design and field operation experience for neutral earthing packages. Most competitors only offer standard 1–2 year warranty. Earthing transformers operate under short-time fault duty. Rockwill’s extended warranty demonstrates confidence in winding insulation and structural reliability.

Rockwill’s economical earthing transformer variant. It retains the core Zig-zag ZN winding structure to create artificial neutral point, with basic temperature monitoring as standard.
Cost optimization can be achieved via the following downgrade options:

• Downgrade insulation class from Class H to Class F
• Remove remote temperature sensors, keep local temperature measurement only
• Simplify enclosure IP rating according to site environment
• Remove integrated PT/CT; customers may use external instrument transformers

The solution cuts unnecessary features while guaranteeing required neutral earthing function and compliance to reduce capital expenditure.

Rockwill Zig-zag (ZN connection) earthing transformers compete with global leading brands including Hitachi Energy, Schneider Electric and GE Vernova in technology, configuration and package delivery.

• Core: Cold-rolled oriented silicon steel, low loss & low noise
• Winding: Dedicated Zig-zag (ZN) winding with controllable zero-sequence impedance, tolerance ≤ ±10%
• Insulation class: Class F / Class H optional (oil-immersed / dry type)
• Package options: Integrated packages with arc suppression coil, neutral earthing resistor cabinet, built-in PT/CT available; many competitors supply only transformer unit separately
• Grades: Economy / Standard / Heavy-duty short-time withstand version
• Certifications: IEC 60076-6, IEC 60076-1, IEEE C57.32 and other national standards on request, full type test reports supplied

Key difference: Rockwill customizes zero-sequence impedance and short-time fault current precisely according to system capacitive current, supporting standalone unit or complete neutral earthing package. Customers select configurations only for actual requirements without overpaying for redundant performance.

Fault withstand time is the maximum duration an earthing transformer can endure fault-current thermal and mechanical stresses under rated short-time capacity, with standard durations of 10s, 30s, 60s, or 1 hour per IEEE 32/IEC 60076‑5. Selection must ensure withstand time ≥ protection clearing time plus redundancy—e.g., a 15‑second relay trip requires a 30‑second withstand rating to prevent damage.