Overview
The LZZB1-24W is an outdoor dry-type current transformer designed for 24kV medium-voltage distribution systems. It features a fully enclosed epoxy cast-resin insulation structure, providing high dielectric strength and mechanical robustness for exposed outdoor installations without the use of transformer oil.
This CT supports standard secondary currents of 5A or 1A and offers metering accuracy classes such as 0.2S, 0.5S and protection classes like 5P, making it suitable for energy metering, current measurement, and relay protection in AC systems operating at 50Hz or 60Hz. It complies with IEC standards for 24/65/125kV insulation levels and is commonly deployed on pole-mounted equipment, outdoor feeders, compact substations, and renewable energy interconnection points.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| Voltage Class | 24kV |
| Insulation Level | 24/65/125kV |
| Rated Frequency | 50Hz or 60Hz |
| Primary Current | As per order (standard ratios) |
| Secondary Current | 5A or 1A |
| Metering Accuracy | 0.2S, 0.2, 0.5S, 0.5 |
| Protection Accuracy | 5P, 10P |
| Installation Type | Outdoor |
| Insulation Material | Epoxy cast-resin |
| Construction Type | Dry-type, oil-free |
| Application | Measurement, metering, protection |
| Approximate Weight | 39kg |
Model Designation
- L: Current transformer.
- Z: Pillar-type / post-type structure.
- Z: Epoxy resin cast insulation.
- B: Metering and protection series.
- 1: Design sequence or platform code.
- 24: 24kV rated voltage class.
- W: Outdoor type.
Construction
The LZZB1-24W employs a monolithic outdoor epoxy cast-resin body, forming a fully sealed dry-type structure that eliminates internal air gaps and moisture ingress. The primary conductor is integrated into the cast housing, while the secondary windings are embedded within the epoxy matrix for optimal thermal and electrical performance. A front-mounted terminal box provides easy access to secondary terminals for wiring, testing, and maintenance. This oil-free design ensures long-term reliability in harsh outdoor environments, withstanding UV exposure, temperature cycling, and pollution without degradation of insulation properties.
Technical Parameters
Service Conditions
- Installation place: Outdoor
- Maximum ambient temperature: +40°C reference
- Minimum ambient temperature: -5°C reference from catalogue data; lower temperature available by agreement
- Rated frequency: 50Hz or 60Hz
- Altitude: ≤ 1000m under standard service conditions; higher altitude by agreement
- Atmospheric condition: No severe pollution, corrosive gas or explosive atmosphere beyond design limits
Technical Parameters
The LZZB1-24W is an outdoor epoxy resin cast current transformer rated for 24kV systems, featuring a cast-resin insulation system suitable for harsh environmental conditions. It operates within an ambient temperature range of -5°C to +40°C at altitudes up to 1000m and complies with IEC 61869-1, IEC 61869-2, GB/T 20840.1, and GB/T 20840.2 standards. The device supports primary current ratings from 20A to 2500A, with secondary outputs of 1A or 5A.
Ambient Temperature: -5°C ～ +40°C
| Rated Primary Current (A) |
Accuracy Classes Combination |
Rated Output (VA) | Rated Short-Time Thermal Current (kA/1s) |
Rated Dynamic Current (kA) |
|||
|---|---|---|---|---|---|---|---|
| 0.2S | 0.2 / 0.5S | 0.5 | 5P | ||||
| 20–40 | 0.2S/0.5 0.2/0.5 0.2/5P10 0.5/5P10 0.2/5P10 0.5/5P10 |
10 | 15 | 15 | 15 | 250 I1n | 625 I1n |
| 50–100 | 300 I1n | 750 I1n | |||||
| 150–250 | 40 | 100 | |||||
| 300–2500 | 15 | 20 | 63 | 160 | |||
| 10–200 | 0.2S/5P20 0.2/5P20 0.5S/5P20 0.5/5P20 0.2S/0.5/5P10 |
10 | 15 | 15 | 15 | 150 I1n | 375 I1n |
| 300–500 | 40 | 100 | |||||
| 600–1000 | 15 | 20 | 20 | 80 | 200 | ||
Installation & Wiring
Installation Diagram
The LZZB1-24W outdoor epoxy-resin cast current transformer is designed for secure mounting on support structures using the provided flange base. Ensure proper alignment with primary conductors and maintain required clearances as per local electrical codes. Connect secondary wiring to terminal blocks using appropriate gauge cables, and verify polarity before energizing.
Windings & Terminal Marking
| Terminal | Function | Application Note |
|---|---|---|
| P1 / P2 | Primary terminals | Used for primary current direction and polarity reference. |
| S1 / S2 | Single secondary winding | Used when one secondary output is specified. |
| 1S1 / 1S2 | First secondary winding | Usually assigned to metering or current measurement. |
| 2S1 / 2S2 | Second secondary winding | Usually assigned to relay protection. |
| 3S1 / 3S2 | Additional secondary winding when specified | Used for backup protection or independent monitoring circuit. |
| Grounding point | Secondary / base grounding reference | One point of the secondary circuit and the CT base should be grounded according to project practice. |
Selection & FAQs
Selection Guide
- Select based on system voltage (24kV) and outdoor application requirements.
- Choose between 5A or 1A secondary current depending on connected devices and total burden.
- Specify accuracy class: 0.2S, 0.2, 0.5S, or 0.5 for metering; 5P10 or 5P20 for protection.
- Confirm creepage distance and electrical clearance meet local outdoor insulation standards.
- Verify mounting dimensions and weight (approx. 39kg) suit the installation structure.
- Ensure terminal box location and P1/P2 orientation align with site wiring layout.
Frequently Asked Questions
Q1: What accuracy class should I select for revenue billing?
Choose the 0.2S class for precise billing applications. It guarantees high accuracy across varying load currents per IEC 61869-2. Contact us for specific calibration certificates.
Q2: Can this 24kV CT be installed at high altitudes?
Standard models are rated for altitudes up to 1000m. For installations exceeding this limit, special design adjustments are required. Please provide your exact site altitude for factory evaluation.
Q3: How is the short-circuit withstand capacity specified?
Rated short-time thermal and dynamic currents are defined in the technical parameter table based on your primary current rating. These parameters ensure safe equipment operation during severe system faults.
Q4: Are lower ambient temperature ratings available for extreme climates?
The standard minimum ambient temperature is -5°C. Lower temperature ratings are available by special agreement for extreme cold environments. This ensures reliable insulation performance in severe weather conditions.
Q5: Which international standards does this outdoor current transformer comply with?
This outdoor current transformer fully complies with IEC 61869-1, IEC 61869-2, GB/T 20840.1, and GB/T 20840.2 standards. Standard factory test reports are provided with each shipment. Request type test reports during the inquiry stage if required.
Q6: Why choose epoxy cast-resin insulation for this outdoor transformer?
Epoxy resin insulation provides reliable protection against harsh outdoor environmental conditions. It is specifically designed for 24kV power systems and switchgear installations. The cast-resin design prevents moisture ingress and ensures long-term dielectric strength.