Grounding transformer
The 6kV, 10kV, and 35kV power grids in the power system generally adopt a neutral point ungrounded operation mode. The low-voltage side of the main transformer in the power grid is generally connected in a delta configuration, and there is no neutral point that can be grounded. With the continuous expansion of urban power grids and the increasing number of cable outlets, the system's capacitance current to ground increases sharply, and the capacitance current flowing through the fault point after single-phase grounding is relatively large (exceeding 10A). In order to reduce the ground capacitance current during single-phase grounding faults, compensation devices such as arc suppression coils need to be installed at the neutral point of the transformer. Therefore, a neutral point needs to be artificially established to connect the arc suppression coil at the neutral point, reduce the ground short-circuit breaking current, and improve the reliability of the system power supply.
In addition, single-phase grounding is a common fault during the operation of the generator, and the occurrence of arc grounding at the fault point will further expand the insulation damage of the stator winding. The high resistance grounding of the neutral point of the generator can effectively suppress the grounding fault current of the generator, thereby preventing the stator winding of the generator from burning out and reducing the transient overvoltage of arc grounding. For this purpose, our company has developed a motor neutral point grounding resistor cabinet for single-phase grounding faults in motors. It mainly consists of a single-phase grounding transformer and a resistor, which can effectively avoid damage to the generator stator winding and insulation caused by grounding current.
Product Features
Our company manufactures professional 6kV-35kV grounding transformers (epoxy cast dry-type, oil-immersed) and motor-specific single-phase grounding transformers.
A. Iron core
High-quality cold-rolled oriented silicon steel with 45° full diagonal joints is used. The iron yoke is clamped by a through screw, the core column by fiberglass tape, and the core surface is coated with silicone resin adhesive for moisture protection, tightness, and noise reduction.
B. Protective device
Oil-immersed grounding transformers have pressure relief valves, gas relays, and oil level gauges for monitoring oil levels, while dry-type ones feature temperature control with remote transmission for temperature checks.
C.dry-type and oil immersed grounding transformers
Epoxy resin dry-type grounding transformers, unfilled in vacuum casting, offer superior smoke and water resistance over non-encapsulated types. Oil-immersed grounding transformers feature a fully sealed design with corrugated fins for heat dissipation, eliminating the oil tank. Oil-resistant rubber strips seal the tank, preventing air contact and preserving oil insulation and lifespan. Benefits include a compact size, aesthetic appeal, and maintenance-free operation.
D.Winding
Both the inner and outer windings are made of high-quality copper wires, with a segmented cylindrical structure to enhance interlayer insulation. Vacuum drying technology is used, and the formed windings have good electrical performance, high mechanical strength, and low local discharge capacity.
| Types |
SJD Dry or Oil-immersed |
| Connection group |
(ZN (Zigzag), ZNyn, YNd(open), Ii0) |
| Voltage |
Up to 36kV |
| Current |
Up to 3000A |
| Duty (Seconds) |
10/30/60 or others |
| Cooling Method |
ONAN, ONAF, AN, AF |
| Frequency |
50Hz / 60Hz |
| Installation |
Indoor / Outdoor |
| Ambient Temperature |
-40 ºC to 40 ºC |
| Standards |
IEC 60076-6, IEC60076-1,IEEE |
| Enclosure Options |
Transformer cabinet for any IP degrees with:CT,VT,Isolation switch |
Note: Neutral Short time Current I0=IG, Neural Zero Sequence Impedance Z0=Zphase /3
±5% off load tap change switch
Declare Z0 before producing if not a self-limiter
Z0 tolerance ≤10%
If a resistor will be connected between the brought out Neutral and ground, choose Z0 as small as possible, and better make Z0+R= VLN/IG
| SJD-Dry or Oil-immersed Earthing transformer(Popular products) |
| Item&Specs. |
Ground-fault Current I0 |
Time |
Impedance Z0 |
| SJD-4.16KV/200A-10S |
200A |
10s |
2.4~12.0Ω |
| SJD-4.16KV/400A-10S |
400A |
10s |
1.2~6.0Ω |
| SJD-4.16KV/600A-10S |
600A |
10s |
0.8~4.0Ω |
| SJD-12.47KV/200A-10S |
200A |
10s |
7.2-36.0Ω |
| SJD-12.47KV/400A-10S |
400A |
10s |
3.6-18.0Ω |
| SJD-12.47KV/600A-10S |
600A |
10s |
2.4~12.0Ω |
| SJD-13.2KV/200A-10S |
200A |
10s |
7.6~38.1Ω |
| SJD-13.2KV/400A-10S |
400A |
10s |
3.8~19.1Ω |
| SJD-13.2KV/600A-10S |
600A |
10s |
2.5~12.7Ω |
| SJD-13.8KV/200A-10S |
200A |
10s |
8.0~39.8Ω |
| SJD-13.8KV/400A-10S |
400A |
10s |
4.0~19.9Ω |
| SJD-13.8KV/600A-10S |
600A |
10s |
2.6~13.3Ω |
| SJD-13.8KV/800A-10S |
800A |
10s |
2.0~10.0Ω |
| SJD-24.94KV/200A-10S |
200A |
10s |
14.4~72.0Ω |
| SJD-24.94KV/400A-10S |
400A |
10s |
7.2~36.0Ω |
| SJD-24.94KV/600A-10S |
600A |
10s |
4.8~24.0Ω |
| SJD-24.94V/800A-10S |
800A |
10s |
3.6~18.0Ω |
| SJD-24.94V/1000A-10S |
1000A |
10s |
2.8~14.4Ω |
| SJD-34.5KV/200A-10S |
200A |
10s |
14.1~70.7Ω |
| SJD-34.5KV/400A-10S |
400A |
10s |
7.0~35.4Ω |
| SJD-34.5KV/600A-10S |
600A |
10s |
4.7~23.6Ω |
| SJD-34.5V/800A-10S |
800A |
10s |
34~17.7Ω |
| SJD-34.5V/1000A-10S |
1000A |
10s |
2.8~14.2 |
Shanghai Changji Electric Co., Ltd. is a professional enterprise specializing in the production of various reactors, power transformers, dry-type transformers, amorphous alloy transformers, special transformers, and box-type substations.
For years, the company has adhered to a customer-first philosophy, earning trust and support through a strong commitment to product quality. By continuously improving quality management and pursuing excellence, Zhejiang Changji Electric Co., Ltd. Strives to secure its market position. With full enthusiasm, sincere cooperation, and a win-win business approach, we warmly welcome domestic and international customers to visit, inquire, and discuss potential collaborations!
Equipped with modern production facilities, advanced manufacturing processes, and comprehensive testing equipment, the company ensures the production of high-performance products featuring innovative designs, low losses, low temperature rise, low noise, high impact resistance, and strong short-circuit withstand capability.
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