Three Phase Oil-Immersed Neutral Earthing Transformer Custom Factory-33kV

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Key attributes

Brand	ROCKWILL
Series	JDS
Rated voltage	33kV
Rated neutral current	Up to 3000 A
Rated frequency	50 / 60 Hz

Description

Rockwill three-phase oil-immersed Z-type earthing transformers provide a reliable artificial neutral point for medium-voltage power systems. Featuring a fully sealed oil-immersed structure with optimized zigzag (ZN) winding, these transformers deliver stable neutral grounding for ungrounded or low-current grounded systems.

They effectively suppress arc grounding overvoltage, limit ground fault currents, and enhance grid stability. Manufactured in compliance with IEC standards, these units support a wide range of capacities and are suitable for distribution substations, industrial facilities, and power utilities.

Key Features

Medium-Voltage Neutral Grounding ：Provides an artificial neutral point for ungrounded or delta-connected systems, enabling connection of arc suppression coils or neutral grounding resistors.
Optimized Z-Type Winding ：Zigzag (ZN) winding configuration delivers low zero-sequence impedance, ensuring efficient fault current path and sensitive relay protection.
Oil-Immersed Fully Sealed Construction ：Durable sealed tank design with mineral oil insulation ensures long service life, strong overload capacity, and maintenance-free outdoor operation.
Flexible Cooling Options ：Available with ONAN or ONAF cooling systems to match application load profiles and ambient conditions.
Customizable Secondary Winding ：Optional auxiliary winding enables dual use as station service transformer, supplying local LV loads.

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Technical Parameters

Parameter	Value
Highest voltage for equipment (Um)	36 kV
Rated frequency	50 / 60 Hz
Number of phases	Three
Connection group	ZN (zigzag) / ZNyn11
Rated capacity	Customizable (per project specification)
Rated neutral current	Up to 3000 A
Rated short-time duration	10 s / 30 s / 60 s (customizable)
Zero-sequence impedance (Zo)	Per project specification (tolerance ≤ ±10 %)
Cooling method	ONAN / ONAF
Insulation medium	Mineral oil
Auxiliary winding	Optional (0.4 kV)
Ambient temperature	–25 °C to +40 °C
Installation	Indoor or outdoor
Enclosure options	IP-rated cabinet; optional CT, VT, or isolation switch

Insulation Level

System Voltage	Um (kV)	PF (kV)	LI (kV)
33 kV	36	70	170

Environmental Conditions

Item	Value
Max ambient air temperature	+40°C
Max 24h average ambient air temperature	+35°C
Min ambient air temperature	-25°C
Altitude	≤ 1000 m
Max relative humidity（24h average）	≤ 95%
Max relative humidity（1 month average）	≤ 90%
Max water vapor pressure（24h average）	2.2 kPa
Max water vapor pressure（1 month average）	1.8 kPa
Solar radiation	≤ 1000 W/m²
Pollution level	II

Applications

Medium-voltage distribution network neutral grounding
Wind farm and photovoltaic power station grid connection
Railway traction power supply systems
Industrial and mining enterprise power distribution
Regional substation grounding protection projects
Urban power grid upgrading and renovation

Standards

IEC 60076-6 — Power transformers – Part 6: Reactors (grounding transformer requirements)
IEC 60076-1 — Power transformers (general)
IEC 60071-1 — Insulation coordination
ISO 9001 — Quality management system

Solutions for Earthing Transformer

Intelligent Maintenance Services and Sustainable Solutions for Z-Type Grounding Transformers

Intelligent Maintenance Services and Sustainable Solutions for Z-Type Grounding TransformersZ-type grounding transformers are critical for stabilizing ungrounded or delta-connected power systems by providing a low-impedance path for zero-sequence currents during faults. Integrating intelligent maintenance and sustainability practices enhances their reliability while minimizing environmental impact. Below is a structured analysis of advanced solutions:I. Intelligent Maintenance Services Real-Time

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Documentation Resource Library Earthing Transformer

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FAQ for Earthing Transformer

Q: What are the core international standards governing the design, production and testing of earthing/grounding transformers, and what are their respective focuses?

Global standards for grounding transformers fall into IEEE and IEC systems. IEEE 32 (North America) emphasizes fault withstand capability and zero-sequence impedance, while IEC 60076 series covers winding design, insulation, cooling, and short-circuit tests. Chinese standards follow IEC with additional grid-specific requirements on efficiency, temperature rise, and harmonics.

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