| Brand | ROCKWILL |
| Model NO. | 15kV 20kV 22kV 30kV 33kV 35kV oil-immersed neutral grounding resistance to transformer (earthing transfoemer) |
| Rated voltage | 33kV |
| Rated frequency | 50/60Hz |
| Rated capacity | 800kVA |
| Series | JDS |
With decades of focused expertise in the field of grounding transformers, we have built end-to-end independent capabilities—from core R&D to scaled mass production—through sustained technological depth. Leveraging industry-leading product performance and long-term reliability, we have established the technical benchmark in this field domestically, becoming a core force driving the advancement of grid safety.
Our 6-35kV (including 33kV) oil-immersed neutral grounding resistance transformers, also known as earthing transformers, are designed for medium-voltage grids. Using oil cooling technology, they safely dissipate heat. By creating a neutral point connection with a grounding resistance, these transformers quickly detect and limit ground faults. Ideal for enhancing grid reliability, they offer robust protection against electrical failures, ensuring stable power supply for industrial and commercial applications.
Energy-Efficient & Eco-Friendly: Low-loss, low-noise, and high-efficiency design reduces energy consumption and environmental impact.
Fully Sealed & Maintenance-Free: No oil storage tank required. Corrugated tank design automatically adjusts for oil volume changes, eliminating leakage risks.
Extended Lifespan: Sealed structure isolates oil from air, slowing degradation and insulation aging. Reduces maintenance costs and extends operational life.
Main technical specifications
The following table details the key technical specifications of the product, comprehensively covering electrical performance, mechanical characteristics, and dimensional parameters to provide a clear reference for technical selection and application scenarios.
Some of these earthing transformers cover voltage levels including：3.3kV / 6kV / 11kV / 15kV / 20kV / 22kV / 30kV / 33kV / 34.5kV / 36kV / 44kV / 66kV / 88kV / 110kV / 132kV / 145kV / 150kV / 220kV / 275kV / 330kV / 400kV, etc. The current withstand time ranges from 1s, 2s, 3s, 5s, 6s, 8s, 9s, 10s, 30s, 60s, 1hour to 2hours, and customization is available.
Parameter |
Specification |
Use |
Power |
Number of phases |
Three |
Coil structure |
Toroidal transformers |
Number of coils |
Autotransformers |
Model |
SJD - 800/33 |
Authentication |
ISO9001 |
Material |
Copper/aluminum/customized |
Frequency |
50Hz/60Hz |
Application |
Industrial power supplies |
Standard |
IEC60076 |
Rated capacity |
30-3000kva/customized |
Warranty |
1 year |
Input voltage |
400v/6kv/11kv/35kv |
Output voltage |
200v/220/240/380v/400v/415v/440v |
Operating Conditions
Altitude:≤1,000 meters
Ambient Temperature:
Maximum ambient temperature: +40°C
Maximum daily average temperature: +30°C
Maximum annual average temperature: +20°C
Minimum outdoor temperature: -25°C
Six core parameters must be checked one by one during replacement to avoid compatibility issues: ① System line voltage: Must be consistent with the original (for example, 110kV grade must be replaced for the original 110kV); ② Zero-sequence impedance: The deviation from the original value must be ≤ ±10% to ensure that the protection setting value does not need to be adjusted; ③ Short-time capacity and fault withstand time: Must not be lower than the original grade (for example, the original 30 seconds/5MVA, the new product must meet or be better than this index); ④ Winding structure: Must be consistent with the original type (for example, the original zigzag type cannot be replaced with the wye-delta type) to avoid changes in grounding performance; ⑤ Insulation and cooling method: Must adapt to the original installation scenario (for example, the original outdoor oil-immersed type cannot be replaced with the indoor dry-type); ⑥ Auxiliary winding specifications (if any): The voltage level and capacity must match the original (for example, the original 400V/200kVA, the new product must be consistent) to ensure the normal power supply of the auxiliary load of the substation.
The characteristics of the marine environment such as salt spray, humidity, vibration, and limited space require earthing/grounding transformers to meet special design requirements: ① Insulation protection: Use salt spray and mold resistant insulation materials (such as salt spray resistant cast resin), and coat the winding surface with anti-corrosion coating; ② Structural design: Adopt a compact modular structure to adapt to the narrow space of ships/platforms; dry-type (oil-free) is preferred to avoid oil leakage polluting the marine environment; ③ Vibration resistance: Enhance the winding fixing and core clamping structure to meet the mechanical requirements of ship sway and vibration (vibration grade ≥ IEC 60076-5 Class 3); ④ Voltage and frequency: Need to adapt to ship-specific voltage (such as 6.6kV) and frequency (such as 60Hz), and the auxiliary winding needs to meet the power demand of the ship's power station (such as 440V/220V); ⑤ Cooling method: Adopt natural air cooling (KNAN) to avoid fan failure affecting operation and adapt to the closed cabin environment.
