LJ-2,4,7,LJ1 Zero-sequence current transformer for Grounding Protection
Overview: The LJ-2, 4, 7 series zero-sequence current transformers are indoor devices , this LJ types of zero-sequence current transformer is specifically designed for grounding protection in power systems. They are widely applied to protect generators, synchronous condensers, or motors in small grounding current systems. These zero-sequence transformers are paired with the DD-11/60 relay for […]
Overview:
The LJ-2, 4, 7 series zero-sequence current transformers are indoor devices , this LJ types of zero-sequence current transformer is specifically designed for grounding protection in power systems. They are widely applied to protect generators, synchronous condensers, or motors in small grounding current systems. These zero-sequence transformers are paired with the DD-11/60 relay for effective fault detection and system safety.
When a ground fault occurs within the protection zone, the fault current generates a zero-sequence current in the transformer’s secondary circuit, triggering the relay to act promptly. LJ1 Zero-sequence current transformer ensures reliable protection and minimizes risks in critical electrical equipment and systems.
Type Designation of LJ1 Zero-sequence current transformer
The model designation of the LJ-2, 4, 7 Zero-Sequence Current Transformer follows this structure:
- L: Current transformer
- J: For zero-sequence earthen protection
- □: Design number or Version of the transformer
- 2, 4, 7: Indicates the number of cables compatible with the transformer
Construction of LJ1 Zero-sequence current transformer
The LJ-2, 4, 7 zero-sequence current transformers are constructed with an annular iron core, ensuring efficient magnetic flux and compact design. The secondary winding is evenly wound around the core, providing uniform current distribution and optimal performance.
For enhanced stability and ease of installation, the core is securely clamped using clips, and mounting holes are provided on the clamps to facilitate quick and reliable attachment in various setups. This design ensures robust performance while simplifying the installation process.
Technical Data
- The series of zero-sequence current transformers are designed with primary insulation protected by cables. Only the insulation characteristics of the secondary winding are considered. The secondary winding can withstand a power frequency test voltage of 3kV to ground.
- The sensitivity of the product meets the requirements listed below:
| Model Type | Number of Cables |
Secondary Output (Ω) |
Adjustment Current (A) |
Sensitivity (A) | Rated Current Ratio (A) |
|---|---|---|---|---|---|
| LJ-2 | 1~2 | 10 | 0.03 | 1~3 | 20/1 |
| LJ-4 | 3~4 | 10 | 0.03 | 1~3 | 20/1 |
| LJ-7 | 5~7 | 10 | 0.03 | 1~3 | 40/1 |
The outside diameter of the cable must be bellow of the 50mm. If the outside diameter is than 50mm, please choose the bigger zero sequence current transformers.
Overall Dimension
| Model Type | A (mm) | B (mm) | H (mm) | ΦD (mm) | Φd (mm) |
|---|---|---|---|---|---|
| LJ-2 | 150 | 200 | 295 | 230 | 110 |
| LJ-4 | 220 | 280 | 335 | 285 | 140 |
| LJ-7 | 220 | 300 | 375 | 300 | 180 |
| LJ1 | 80 | 125 | 170 | 135 | 80 |
When ordering, please specify the following:
- Rated voltage and frequency;
- Current ratio;
- Installation environment;
- For special requirements, please contact our technical team.
FAQs of LJ-2,4,7,LJ1 Zero sequence current transformer
- What are the main applications of the LJ series zero-sequence current transformers?
The LJ series transformers are used for grounding protection in power systems, particularly for generators, synchronous condensers, and motors in small grounding current systems. - What is the function of the LJ series zero-sequence current transformers?
These transformers detect zero-sequence currents during ground faults, generating a secondary current that triggers the relay (e.g., DD-11/60) to act and protect the system. - What sizes of cables are compatible with the LJ series transformers?
The LJ-2, 4, and 7 transformers are compatible with cables having an outside diameter of up to 50mm. For larger cable diameters, choose a larger transformer model. - What is the rated insulation performance of the LJ series transformers?
The secondary winding insulation can withstand a power frequency test voltage of 3kV to ground, ensuring reliable performance under typical operating conditions. - How are the LJ series transformers installed?
The transformers feature an annular iron core with clamps for secure mounting. Mounting holes are provided on the clamps, simplifying installation and ensuring stability in various setups.
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