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Help CenterThree-Phase 11kV 22kV 33kV Zigzag Grounding Transformer With Neutral Grounding Resistor NGR NER System for Substation Grounding Protection
Product Spotlights
-Fault Current Limitation: High-grade stainless steel/NiCr resistor banks limit line-to-ground fault current effectively.
-High Short-Circuit & Thermal Capacity: Engineered for 10s/30s/continuous thermal withstand without overheating.
-Turnkey Integrated Solution: Complete package with grounding transformer, NGR cubicle, disconnect switch, and CTs.
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Three-Phase Zigzag Grounding Transformer (Earthing Transformer) for System Neutral Grounding & Fault Protection
Specially engineered for ungrounded or delta-connected power networks, our Zigzag Grounding Transformer provides an artificial, stable neutral point for system grounding. Designed for medium-voltage substations, wind and solar renewable power plants, and industrial utility grids, it enables secure fault-current return paths, eliminates transient overvoltages, and integrates seamlessly with Neutral Grounding Resistors (NGR/NER) and secondary station auxiliary power supplies.
1. Product Overview
The Three-Phase Zigzag (ZN / ZNyn) Earthing Transformer is specifically engineered to establish an accessible neutral point in 3-wire ungrounded distribution systems (6kV, 10kV, 11kV, 22kV, 33kV, 35kV). During line-to-ground faults, the unique zigzag winding geometry offers extremely low zero-sequence impedance, allowing sufficient ground fault current to flow for reliable relay protection trip and neutral voltage stabilization.
Available in both Dry-Type (Cast Resin) and Oil-Immersed (Hermetically Sealed) constructions, each unit can be customized with an auxiliary low-voltage secondary winding (ZNyn11) to supply continuous station service auxiliary loads (such as substation lighting, heaters, and control systems).
2. Main Characteristics & Engineering Advantages
Optimized Low Zero-Sequence Impedance: The cross-connected zigzag windings ensure balanced ampere-turns and provide low zero-sequence impedance to facilitate precise earth-fault detection and protective relay coordination.
High Thermal & Mechanical Withstand Capacity: Designed to withstand full ground fault current under rated short-time duration ($10\text{s}$, $30\text{s}$, or $60\text{s}$) without mechanical distortion or insulation thermal degradation.
Integrated Secondary Auxiliary Power (Optional ZNyn): Enables dual functionality by integrating a continuous LV winding (e.g., 400V/230V, 50kVA–500kVA) to power substation auxiliary equipment directly from the primary bus.
Seamless NGR Integration: Engineered for turnkey integration with Neutral Grounding Resistor (NGR/NER) cubicles, current transformers (CTs), neutral disconnectors, and lightning surge arresters.
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Flexible Enclosure & Cooling Configurations: Available as open-type IP00, ventilated indoor IP20/IP23, or outdoor weatherproof heavy-duty IP54/IP55 corrosion-resistant enclosures.
3. Technical Features & Performance Highlights
Standards Compliance: Fully compliant with IEC 60076-6 (Reactors & Earthing Transformers), IEEE C57.32 (Grounding Devices), GB/T 1094.6, and ANSI/IEEE standards.
Vector Group: ZN (Pure Grounding), ZNyn11, ZNd11, or customized phase configurations.
Duty Cycle & Thermal Rating: Short-time fault withstand rating, or continuous) matched precisely with system protective relay settings.
Magnetic Core Technology: Low-loss, cold-rolled grain-oriented (CRGO) silicon steel stacked with precision step-lap mitered joints for low excitation current and quiet operation.
Insulation System: Class F 155 degree / Class H 180 degree for dry-type, or high-grade uninhibited mineral oil / ester dielectric fluid for oil-immersed units.
4. Key Technical Specifications Table
| Parameter / Technical Item | Standard Specification & Custom Range |
| System Voltage Rating (HV) | 3.3kV, 6.6kV, 10kV, 11kV, 13.8kV, 20kV, 22kV, 33kV, 35kV |
| Connection / Vector Group | ZN, ZNyn11, ZNd11, YNsyn, or Custom |
| Neutral Fault Current ($I_n$) | 50A, 100A, 200A, 400A, 600A, 1000A up to 2000A |
| Rated Fault Duration | 10 seconds, 30 seconds, 60 seconds, or Continuous |
| Auxiliary LV Capacity (if required) | 30 kVA – 1000 kVA (Continuous secondary power: 400V / 230V) |
| Cooling Method | AN (Air Natural) / ONAN (Oil Natural Air Natural) |
| Insulation Type | Epoxy Cast Resin Dry Type or Mineral Oil Immersed |
| Zero-Sequence Impedance ($Z_0$) | Custom engineered per network protection calculation |
| Protection Degree | IP00, IP20, IP23, IP31, IP54, IP55 Outdoor Enclosure |
| Applicable Standards | IEC 60076-6, IEEE C57.32, GB/T 1094.6 |
5. Quality Control & Factory Routine Testing
Every single transformer undergoes rigorous routine testing before leaving our factory to ensure 100% operational reliability:
Winding Resistance Measurement
Voltage Ratio Inspection & Vector Group Verification
Impedance Voltage & Load Loss Measurement
No-Load Loss & No-Load Current Measurement
Separate-Source AC Voltage Withstand Test
Induced Overvoltage Withstand Test (DVDF)
Transformer Oil Dielectric Strength & Breakdown Voltage Test
6. Applications
Power Grids & Substations – Step up from generation voltage to transmission level, or step down to distribution voltage at substations. Especially suitable for distribution nodes with long‑term no‑load standby status for remarkable energy‑saving benefits.
Renewable Energy Substations: Solar PV collector substations and wind farm medium-voltage grids to stabilize the 33kV/35kV bus neutral.
Industrial Utility Distribution: Chemical complexes, steel manufacturing, data centers, and mining plants operating on Delta-connected power networks.
Grid Step-Down Substations: Providing zero-sequence ground fault reference and enabling selective directional ground fault tripping.
8. Get a Custom Quote & Technical Drawing
Need a custom transformer design, technical datasheet, or CAD dimension layout for your project?
Contact our engineering sales team today to get a detailed technical proposal and a competitive quotation within 12 hours!
Please provide:
Rated power (kVA / MVA)
Rated System Voltage (kV): (e.g., 11kV, 22kV, 33kV)
Rated Neutral Fault Current ($I_n$ in Amperes): (e.g., 100A, 200A, 400A)
Fault Duration Time: (e.g., 10s, 30s, or continuous)
Auxiliary Secondary Capacity & Voltage (if required): (e.g., 100kVA, 400V/230V)
Insulation Type: (Dry-Type Cast Resin / Oil-Immersed)
Installation Environment & Enclosure Rating: (Indoor IP23 / Outdoor IP54)
Complete NGR Package Required: (Grounding transformer only / Integrated with NGR cubicle & disconnector switch)
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