Overview
The LZZBJ9-24/220b/2S is an indoor, single-phase, epoxy cast-resin current transformer designed for 20kV, 22kV and 24kV class medium-voltage switchgear. It features a fully enclosed epoxy resin body with ribbed external insulation, providing robust dielectric performance and mechanical stability in indoor AC power systems operating at 50Hz or 60Hz.
This dual-secondary (2S) CT supports standard secondary currents of 5A or 1A and offers accuracy combinations such as 0.2S/0.5, 0.2/0.5, and 0.2S/5(10)P10. It is engineered for applications requiring one metering/measurement winding and one protection winding—ideal for standard feeder panels, metering cabinets, and relay protection circuits in utility substations and industrial distribution systems compliant with IEC standards.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| Voltage Class | 20kV / 22kV / 24kV |
| Rated Insulation Level | 24/65/125kV |
| Frequency | 50Hz or 60Hz |
| Secondary Current | 5A or 1A |
| Secondary Configuration | 2S (dual-secondary) |
| Metering Accuracy Classes | 0.2S, 0.2, 0.5 |
| Protection Accuracy Classes | 5P10, 10P10, 5(10)P20 |
| Phase | Single-phase |
| Installation Environment | Indoor |
| Insulation Material | Epoxy cast-resin |
| Application | Metering, measurement, relay protection |
| Structure | Fully enclosed with ribbed insulation |
Construction
The LZZBJ9-24/220b/2S features a monolithic, fully enclosed epoxy cast-resin body that encapsulates the primary conductor, magnetic core, and secondary windings. This construction provides excellent moisture resistance, high dielectric strength, and long-term mechanical stability under indoor operating conditions. The external surface incorporates a ribbed insulation design to extend the creepage distance and enhance pollution performance in typical indoor switchgear environments. All live parts are completely sealed within the resin matrix, eliminating exposure to ambient air and contaminants. The terminal box is integrated into the cast body, offering secure and accessible connections for the two independent secondary circuits—one typically dedicated to metering or measurement and the other to relay protection functions.
Technical Parameters
Service Conditions
- Installation site: indoor medium-voltage switchgear
- Rated voltage: 20kV, 22kV and 24kV class systems
- Rated frequency: 50Hz or 60Hz
- Ambient temperature: maximum +40°C, minimum -5°C, daily average not exceeding +30°C
- Atmospheric conditions: no severe pollution, conductive dust, corrosive gas or abnormal condensation
- Altitude, humidity, pollution level and seismic requirements: should be confirmed according to project specification.
Technical Parameters
The LZZBJ9-24/220b/2S is an indoor epoxy cast-resin current transformer designed for 20kV, 22kV, and 24kV class systems. It operates within an ambient temperature range of -5°C to +40°C, complies with IEC 61869-1/-2 and GB/T 20840.1/.2 standards, and supports primary current ratings from 20A to 3150A.
| Rated Primary Current (A) |
Accuracy Classes Combination |
Rated Output (VA) | Rated Short-Time Thermal Current (kA/1s) |
Rated Dynamic Current (kA) |
|||
|---|---|---|---|---|---|---|---|
| 0.2(S) | 0.5(S) | 5(10)P10 | 5(10)P20 | ||||
| 20–200 | 0.2S/0.5 0.2/0.5 0.2(S)/5(10)P10 0.5(S)/5(10)P10 0.2(S)/5(10)P10 0.5(S)/5(10)P10 |
15 | 15 | 20 | 20 | 150 I1n | 375 I1n |
| 300 | 31.5 | 80 | |||||
| 400–500 | 45 | 110 | |||||
| 600–800 | 63 | 130 | |||||
| 1000–3150 | 15 | 20 | 30 | 20 | 100 | 160 | |
Installation & Wiring
Installation Diagram
The LZZBJ9-24/220b/2S indoor epoxy cast-resin current transformer is designed for installation within 24kV switchgear using the approved base mounting holes. Ensure proper alignment of primary terminals, busbar connections, and secondary terminal access during assembly. Confirm all dimensional clearances—including insulation clearance and maintenance space—before finalizing the switchgear layout.
Selection & FAQs
Selection Guide
- Select the LZZBJ9-24/220b/2S for indoor 20kV–24kV switchgear applications requiring dual-secondary current transformers.
- Choose the 2S version when your design needs one winding for metering (e.g., 0.2S or 0.5 class) and another for protection (e.g., 5P10 or 10P10).
- Confirm that your system operates indoors—this cast-resin CT is not rated for outdoor use without special confirmation.
- Verify voltage compatibility: the unit is rated for 24/65/125kV insulation levels and supports 20kV, 22kV, and 24kV systems.
- Specify required accuracy classes, secondary output (1A or 5A), burden, and short-circuit withstand ratings (Ith/Idyn) during ordering.
- Review mechanical details before production, including primary terminal layout, mounting dimensions, and secondary terminal box orientation.
Frequently Asked Questions
Q1: Can this 24kV current transformer be installed in 22kV switchgear?
Yes, it is designed for 20kV, 22kV, and 24kV class indoor systems. Ensure the installation site meets the -5°C to +40°C ambient temperature requirements. Contact us for specific project verification.
Q2: Which accuracy class combination is best for metering and protection?
Select 0.2S/5(10)P10 or 0.5(S)/5(10)P10 for combined metering and protection. The 0.2S class ensures high precision for revenue metering, while 5P10 handles protection tasks. Confirm exact rated outputs with our engineering team.
Q3: What are the short-circuit thermal and dynamic current ratings?
Rated short-time thermal and dynamic currents vary by primary current rating, ranging from 20A up to 3150A. Refer to the detailed technical parameter table for specific kA/1s values. Provide your exact primary current for precise calculations.
Q4: Does this epoxy cast-resin CT comply with international IEC standards?
Yes, the LZZBJ9-24/220b/2S fully complies with IEC 61869-1/-2 and GB/T 20840.1/.2 standards. We provide standard type test and routine test reports upon request. Request specific certification documents during the inquiry stage.
Q5: How can we customize the primary current rating for our project?
Custom primary current ratings between 20A and 3150A are available subject to factory confirmation. Standard and customized units undergo strict routine testing before shipment. Share your single-line diagram for a tailored technical proposal.
Q6: Where can this indoor current transformer be safely installed?
The installation site must be free from severe pollution, conductive dust, corrosive gases, and abnormal condensation. Altitude and humidity limits should be confirmed according to your specific project specifications. Contact our sales team for harsh environment solutions.
Q7: Are you the direct manufacturer of this 24kV indoor current transformer?
Yes, we are the direct manufacturer of the LZZBJ9 series epoxy cast-resin current transformers. Direct manufacturing ensures competitive pricing and strict quality control for 20kV to 24kV applications. Inquire today for factory-direct pricing and lead times.