Overview
The LZZBW-15 and LZZBW-24 are outdoor epoxy resin cast current transformers designed for 15kV, 17.5kV, and 24kV medium-voltage AC systems operating at 50Hz or 60Hz. These pillar-type dry CTs feature a fully enclosed insulation body made of outdoor-grade epoxy resin, providing robust protection against humidity, UV radiation, and pollution in exposed environments.
They support standard secondary currents of 1A or 5A with accuracy combinations such as 0.2/10P10, 0.5/10P15, and 0.2S/5P10, enabling use in revenue metering, current measurement, and relay protection applications. The design complies with IEC 61869 standards for instrument transformers and is suitable for utility distribution networks, industrial outdoor installations, and renewable energy interconnection points.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| Rated voltage class | 15kV / 17.5kV (LZZBW-15), 24kV (LZZBW-24) |
| Rated insulation level | 17.5/38/75kV or 17.5/55/105kV (LZZBW-15); 24/65/125kV (LZZBW-24) |
| Rated frequency | 50Hz or 60Hz |
| Rated secondary current | 1A or 5A |
| Insulation medium | Outdoor-grade epoxy resin |
| Installation type | Outdoor |
| Structure | Pillar-type, fully enclosed |
| Typical accuracy classes | 0.2, 0.2S, 0.5 (metering); 5P, 10P (protection) |
| Application | Metering, measurement, relay protection |
| Short-time thermal withstand | As per IEC 61869 (project-specific) |
| Secondary terminals | Front terminal box with cable outlet |
| Mounting | Bottom plate with four holes and grounding bolts |
Model Designation
- L: Current transformer.
- Z: Pillar-type structure.
- Z: Epoxy resin cast insulation.
- B: Includes protection winding (metering and protection combination).
- W: Outdoor type.
- 15: Rated for 15kV / 17.5kV class systems.
- 24: Rated for 24kV class systems.
Construction
The LZZBW-15 and LZZBW-24 are constructed using vacuum-cast outdoor-grade epoxy resin, forming a monolithic, fully enclosed insulation body that eliminates the need for oil or gas filling. This dry-type design ensures long-term dielectric stability and mechanical strength under outdoor environmental stress, including rain, dust, and solar exposure. The primary conductor is integrated into the cast structure, while the secondary windings are embedded within the resin matrix for optimal protection.
A front-mounted terminal box provides a sealed wiring outlet for secondary cables, enhancing safety and moisture resistance during field connections. The base includes four mounting holes and dedicated grounding bolts, allowing secure attachment to poles, platforms, or substation structures. All external surfaces are UV-stabilized to prevent degradation, ensuring reliable performance over decades of outdoor service.
Technical Parameters
Service Conditions
- Installation place: Outdoor
- Maximum ambient temperature: +40°C reference
- Minimum ambient temperature: -25°C reference
- Daily average temperature: ≤ +30°C reference
- Altitude: ≤ 1000m under standard service conditions; higher altitude by agreement
- Atmospheric condition: No severe pollution, corrosive gas or explosive atmosphere beyond design limits
- Outdoor exposure: Suitable for UV, humidity and tracking-resistant outdoor insulation applications
Technical Parameters
The LZZBW-15 and LZZBW-24 are outdoor epoxy resin cast current transformers designed for 15kV/17.5kV and 24kV voltage classes respectively. They feature fully enclosed pillar-type construction with UV-resistant and tracking-resistant epoxy resin housing, operating within -25°C to +40°C ambient temperature and up to 1000m altitude. Compliant with IEC 61869-1/-2 and GB/T 20840.1/.2 standards, they support primary currents from 5A–600A (LZZBW-15) and 10A–2000A (LZZBW-24), with secondary outputs of 1A or 5A.
| Rated Primary Current (A) |
Accuracy Classes Combination |
Rated Output (VA) |
Rated Short-Time Thermal Current (kA/1s) |
Rated Dynamic Current (kA) |
|---|---|---|---|---|
| 10–40 |
0.2S/0.5/5P10 0.2S/0.5/5P15 0.2S/0.5/5P20 0.2S/0.5/5P30 0.2S/0.5/5P10/5P10 0.2S/0.5/5P15/5P15 0.2S/0.5/5P20/5P20 0.2S/0.5/5P30/5P30 |
20/20/100 20/20/60 20/20/40 20/20/25 20/20/40/40 20/20/30/30 20/20/20/20 20/20/10/10 |
150 × I1n (A) | 375 × I1n (A) |
| 50–100 | 200 × I1n (A) | 500 × I1n (A) | ||
| 150–250 | 32 | 80 | ||
| 300–400 | 50 | 125 | ||
| 500–600 | 63 | 160 |
| Rated Primary Current (A) |
Accuracy Classes Combination |
Rated Output (VA) |
Rated Short-Time Thermal Current (kA/1s) |
Rated Dynamic Current (kA) |
|---|---|---|---|---|
| 750–800 |
0.2S/0.5/5P10 0.2S/0.5/5P15 0.2S/0.5/5P20 0.2S/0.5/5P30 0.2S/0.5/5P10/5P10 0.2S/0.5/5P15/5P15 0.2S/0.5/5P20/5P20 0.2S/0.5/5P30/5P30 |
30/30/120 30/30/80 30/30/50 30/30/30 30/30/50/50 30/30/30/30 30/30/25/25 30/30/15/15 |
80 | 200 |
| 1000–2000 | 100 | 250 |
If user’s data go beyond the above-mentioned scopes, they may be subject to an agreement between manufacturer and purchaser.
Installation & Wiring
Installation Diagram
The LZZBW-15 and LZZBW-24 outdoor epoxy-resin cast current transformers are designed for pole or structure mounting in high-voltage applications. Installation should be performed by qualified personnel following local electrical codes and manufacturer guidelines. Ensure proper alignment, secure fastening, and correct primary conductor routing through the transformer window as shown in the diagram.
Selection & FAQs
Selection Guide
- Select LZZBW-15 for 15kV/17.5kV systems or LZZBW-24 for 24kV outdoor medium-voltage applications.
- Choose between 5A (standard) or 1A secondary current based on metering device compatibility and cable burden requirements.
- Specify accuracy classes: use 0.2S, 0.2, 0.5S, or 0.5 for metering; select 5P10, 5P20, 10P10, or 10P15 for protection functions.
- Confirm rated burden and system protection needs to ensure proper performance under load and fault conditions.
- Verify outdoor environmental requirements including pollution level, creepage distance, and mounting configuration.
Frequently Asked Questions
Q1: What is the maximum system voltage for the LZZBW-24 model?
The LZZBW-24 is designed for 24kV voltage classes. It features a fully enclosed pillar-type construction with UV-resistant epoxy resin housing. Please confirm exact system requirements with our engineering team.
Q2: Can these outdoor current transformers operate in high-altitude environments?
Standard service conditions support altitudes up to 1000m. For installations exceeding this limit, customized designs are available subject to factory confirmation. Contact us with your specific site altitude.
Q3: How do I determine the required short-time thermal current rating?
The rated short-time thermal current depends on your specific primary current selection and system fault levels. Refer to the technical parameter table for exact kA/1s values. Factory calculation support is available upon request.
Q4: Which international standards do these epoxy resin cast transformers comply with?
Both models are fully compliant with IEC 61869-1/-2 and GB/T 20840.1/.2 standards. They undergo rigorous routine testing before dispatch to ensure measurement precision and operational safety.
Q5: Are non-standard primary current ratings available for specific projects?
Yes, standard ranges are 5A–600A for LZZBW-15 and 10A–2000A for LZZBW-24. Non-standard primary currents or specific accuracy class combinations are available subject to manufacturing confirmation. Please provide your exact specifications.
Q6: Where should these outdoor epoxy resin transformers be installed?
They are ideal for outdoor power distribution and substations requiring 15kV or 24kV metering and protection. The UV and tracking-resistant epoxy housing ensures reliable performance in harsh atmospheric conditions. Contact sales for application-specific recommendations.
Q7: Why choose a 1A secondary output over a 5A option?
A 1A secondary output is preferred for long cable runs to reduce burden, while 5A suits shorter distances. Both models support 1A or 5A outputs with selectable accuracy classes. Confirm your required burden with our technical team.