Overview
The LZZB8-35W / LZZBW8-35 / LZZBJ71-35W GY is a 35kV-class outdoor current transformer designed for high-voltage distribution systems. It features a fully enclosed post-type structure with outdoor-grade epoxy resin cast insulation, providing dry-type, oil-free operation suitable for harsh environmental conditions.
This series supports metering accuracy classes such as 0.2, 0.2S, 0.5 and 0.5S, along with protection classes like 5P and 10P, making it ideal for energy metering, relay protection, and current measurement in 35kV/40.5kV outdoor substations. It complies with IEC standards and is rated for insulation levels of 40.5/95/185kV or higher per project requirements.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| Voltage class | 35kV / 40.5kV |
| Insulation level | 40.5/95/185kV (or 40.5/95/190kV) |
| Secondary current | 5A or 1A |
| Metering accuracy | 0.2, 0.2S, 0.5, 0.5S |
| Protection accuracy | 5P, 10P |
| Installation | Outdoor |
| Insulation type | Epoxy resin cast, dry-type |
| Creepage distance | >1200mm (high-pollution versions) |
| Application | Measurement, metering, relay protection |
| Structure | Post-type, fully enclosed |
| Thermal withstand | Rated short-time thermal current per IEC |
| Dynamic withstand | Rated dynamic current per IEC |
Model Designation
- L: Current transformer.
- Z: Post-type / pillar-type structure.
- Z: Cast-resin insulation.
- B: With protection winding / metering and protection current transformer series.
- 8 / 71: Design sequence or manufacturer structure code.
- 35: 35kV rated voltage class, normally matched with 40.5kV highest system voltage.
- W: Outdoor installation.
- GY: Outdoor high-voltage / high-pollution-resistant structure code used by some manufacturers.
Construction
The LZZB8-35W / LZZBW8-35 / LZZBJ71-35W GY features a fully enclosed post-type construction made from outdoor-grade epoxy resin. This dry-type, cast-resin insulation eliminates the need for transformer oil, enhancing safety and reducing maintenance. The design incorporates increased creepage distance—exceeding 1200mm in high-pollution variants—to ensure reliable performance in humid, coastal, or industrial environments. The robust mechanical structure provides high resistance to UV exposure, temperature cycling, and pollution, while maintaining stable electrical characteristics under fault-current conditions.
Technical Parameters
Service Conditions
- Installation place: Outdoor
- Ambient temperature: -40°C to +40°C reference
- Altitude: ≤ 3000m reference; altitude correction by project requirement
- Pollution level: Class 3 / Class 4 or Class IV reference depending on project requirement
- Atmospheric condition: Suitable for outdoor moisture, dirt and tracking-resistant insulation applications
- Installation condition: No severe shock, abnormal vibration or mechanical load beyond approved design limits
Technical Parameters
The LZZB8, LZZBW8-35, and LZZBJ71-35W GY are outdoor epoxy resin cast current transformers rated for 35kV/40.5kV systems, designed for operation in ambient temperatures from -40°C to +40°C and altitudes up to 3000m. They comply with IEC 61869-1, IEC 61869-2, GB/T 20840.1, and GB/T 20840.2 standards, supporting primary currents from 15A to 2000A with multiple accuracy classes and secondary configurations.
| Rated primary current (A) |
Accuracy classed combination |
Rated Output (VA) |
Short-time thermal current (kA/s) |
Rated dynamic current (kA) |
||
|---|---|---|---|---|---|---|
| 0.2 | 0.5 | 10P10 | ||||
| 15 | 0.2/10P10 0.5/10P10 |
10 | 20 | 50 | 2.25/2 | 5.6 |
| 20 | 3.0/2 | 7.5 | ||||
| 30 | 4.5/2 | 11.25 | ||||
| 40 | 6.0/2 | 15 | ||||
| 50 | 7.5/2 | 18.75 | ||||
| 75 | 11.25/2 | 28 | ||||
| 100 | 15/2 | 37.5 | ||||
| 150 | 31.5/1 | 80 | ||||
| 200 | 31.5/2 | 80 | ||||
| 300 | 31.5/3 | 80 | ||||
| 400 | 31.5/3 | 80 | ||||
| 500 | 31.5/3 | 80 | ||||
| 600 | 15 | 30 | 50 | 31.5/4 | 80 | |
| 800 | 31.5/4 | 80 | ||||
| 1000 | 50 | 50 | 50 | 40/4 | 100 | |
| 1200 | 40/4 | 100 | ||||
| 1250 | 40/4 | 100 | ||||
| 1500 | 40/4 | 100 | ||||
| 1600 | 40/4 | 100 | ||||
| 2000 | 40/4 | 100 | ||||
Installation & Wiring
Installation Diagram
The LZZB8, LZZBW8-35, and LZZBJ71-35W GY outdoor current transformers are designed for pole or structure mounting using the provided flange base. Ensure proper alignment with primary conductors and secure all mounting hardware to manufacturer torque specifications. Maintain required clearances for safe operation and compliance with local electrical codes.
Selection & FAQs
Selection Guide
- Select the exact model, not only the family. Detailed ratio/fault data is identified for LZZB8-35W; LZZBW8-35 and LZZBJ71-35W require their own approved schedules.
- Specify cold, altitude and pollution requirements together. Confirm −40°C materials, 3000m correction, Class IV basis, minimum >1200mm creepage, UV, salt fog, icing and condensation.
- Choose 15A–2000A ratio and core count. State every one-to-five secondary function, accuracy, VA, terminal and 1A or 5A rating.
- Compare fault duty using both current and duration. LZZB8 thermal ratings vary from 1s to 4s; use the exact duration required by protection clearing time.
- Approve mechanical and insulation interfaces. Confirm outline, 45° terminal direction, Ø13 mounting holes, conductor plate by current group, wind loads and whether 185kV or special 190kV impulse applies.
Frequently Asked Questions
Q1: Are these 35kV current transformers suitable for 40.5kV systems?
Yes, they are rated for 35kV and 40.5kV systems. The epoxy resin cast design ensures reliable insulation for both voltage levels. Please confirm your exact system voltage during ordering.
Q2: What are the altitude and temperature limits for outdoor installation?
Yes, standard models operate up to 3000m altitude and -40°C to +40°C. For sites exceeding 3000m, altitude correction factors apply. Contact engineering for high-altitude specifications.
Q3: How do I verify the short-circuit withstand capacity for my substation?
Ratings are determined by your specific application needs. Short-time thermal and dynamic capacities vary across the 15A to 2000A primary current range. Provide fault data for exact kA verification.
Q4: Which accuracy class combinations are available for protection and metering?
Standard configurations include 0.2/10P10 and 0.5/10P10 classes. Custom core combinations can be manufactured to meet your specific rated output requirements. Contact sales for custom specifications.
Q5: Do these outdoor current transformers comply with international IEC standards?
Yes, they comply with IEC 61869-1, IEC 61869-2, and GB/T 20840 standards. Official factory test reports and compliance certificates are provided upon request.
Q6: Where are LZZB8 and LZZBW8 current transformers typically applied?
They are primarily applied in 35kV and 40.5kV outdoor substations. These epoxy resin cast units provide reliable performance in heavy pollution areas requiring Class 3 or 4 insulation.
Q7: Can this transformer be installed in areas with high mechanical vibration?
No, installation conditions strictly prohibit severe shock or abnormal vibration. Ensure your mounting structure is highly stable to prevent mechanical damage to the epoxy resin body.