Overview
The LAZBJ-10 / LFZBJ-10 is an indoor, fully enclosed, wall-through current transformer with epoxy resin cast insulation, designed for 10kV, 11kV, and 12kV class medium-voltage AC systems. It features a compact structure where the primary conductor passes through a central aperture, and the laminated core with secondary winding is encapsulated in a solid cast-resin body.
It supports metering accuracy classes such as 0.2S, 0.5S, and protection class 10P10, making it suitable for energy metering, relay protection, feeder monitoring, and switchgear instrumentation. The design complies with standard requirements for indoor switchgear applications and offers reliable performance under rated burden and fault conditions.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| Voltage class | 10kV, 11kV, 12kV |
| Rated insulation level | 12/42/75kV |
| Rated frequency | 50Hz / 60Hz |
| Rated secondary current | 5A or 1A |
| Metering accuracy classes | 0.2S, 0.2, 0.5S, 0.5 |
| Protection accuracy class | 10P10 |
| Installation location | Indoor |
| Insulation material | Epoxy resin cast |
| Primary configuration | Wall-through (single-turn) |
| Secondary terminals | Screw-type, accessible from front |
| Short-time thermal current | As per ratio and system fault level |
| Dynamic withstand current | As per ratio and system fault level |
Model Designation
- L: Current transformer
- A: Wall-through / constructed multi-turn through type
- Z: Epoxy resin casting insulation
- B: Protection class available
- J: Epoxy resin casting insulation / reinforced cast-resin design
- 10: Rated voltage class: 10kV class
- LFZBJ-10: Corresponding wall-through indoor cast-resin CT designation shown in parentheses in the catalogue
Construction
The LAZBJ-10 / LFZBJ-10 features a fully enclosed, wall-through structure with epoxy resin casting insulation. The primary conductor passes through the central aperture without electrical contact to the transformer body, while the laminated silicon steel core and secondary winding are completely encapsulated within the solid cast-resin housing. This construction provides excellent dielectric strength, mechanical robustness, and resistance to indoor environmental factors such as humidity and dust. The resin material ensures stable insulation performance over time and eliminates the need for maintenance. Secondary terminals are located on the front face for easy access during wiring, and the overall compact form factor facilitates integration into standard medium-voltage switchgear panels.
Technical Parameters
Service Conditions
- Installation location: indoor medium-voltage switchgear
- System voltage: 10kV, 11kV and 12kV class networks
- Rated frequency: 50Hz / 60Hz
- Ambient temperature: normally -5°C to +40°C unless otherwise specified
- Installation environment: should be free from severe vibration, corrosive gas, explosive medium, conductive dust, heavy pollution and abnormal condensation.
- Special conditions: For high altitude, coastal, humid, high-pollution or retrofit conditions, technical confirmation is recommended before ordering.
Technical Parameters
The LAZBJ-10 and LFZBJ-10 are indoor wall-through cast-resin current transformers designed for 10kV–12kV class systems. They operate within a standard ambient temperature range of -5°C to +40°C and are suitable for installations up to 1000m altitude unless otherwise specified. Compliant with IEC 60044-1, GB1208-1997, and optionally IEC 61869, these units support primary currents from 20A to 400A and secondary outputs of 1A or 5A.
| Rated Primary Current (A) |
Accuracy Classes Combination |
Rated Output (VA) | Rated Short-Time Thermal Current (kA) |
Rated Dynamic Current (kA) |
||||
|---|---|---|---|---|---|---|---|---|
| 0.2S | 0.2 | 0.5S | 0.5 | 10P10 | ||||
| 20 | 0.2S/10P10 0.2/10P10 0.5S/10P10 0.5/10P10 0.2/0.5/10P10 0.2/10P10/10P10 0.5/10P10/10P10 |
10 | 10 | 10 | 15 | 15 | 2 | 5 |
| 30 | 3 | 7.5 | ||||||
| 40 | 4 | 10 | ||||||
| 50 | 6 | 15 | ||||||
| 75 | 8 | 15 | ||||||
| 100 | 12 | 20 | ||||||
| 150 | 15 | 30 | ||||||
| 200 | 20 | 37.5 | ||||||
| 300 | 32 | 50 | ||||||
| 400 | 36 | 80 | ||||||
Installation & Wiring
Installation Diagram
The LAZBJ-10 and LFZBJ-10 current transformers are installed through the wall of the switchgear cabinet. The primary conductor passes through the central aperture, while the secondary terminals are accessible from the front or side, depending on the selected structure (A-type, B-type, or LFC-10 replacement reference). Mounting is secured using bolts through the designated mounting holes aligned with the cabinet wall opening.
Selection & FAQs
Selection Guide
- Start with the system and insulation requirements. This family is intended for indoor 10kV, 11kV and 12kV-class installations with a published 12/42/75kV insulation level; confirm the project standard, altitude and pollution conditions.
- Select the primary ratio from actual feeder loading. Standard ratings run from 20A to 400A. Allow for continuous load growth without choosing a ratio so high that normal operating current falls outside the useful metering range.
- Choose 1A or 5A secondary current before calculating burden. A 1A circuit can reduce lead losses over longer cable runs, while 5A suits established meters and relays; every connected device must share the selected rating.
- Define the number and duty of the cores. Available combinations pair 0.2S, 0.2, 0.5S or 0.5 measurement with 10P10 protection, including selected three-core arrangements. State each core’s accuracy and rated output separately.
- Verify fault duty and mechanical fit by exact ratio. Short-time thermal and dynamic current ratings change across the 20–400A range; also confirm aperture, cabinet opening, mounting pattern, terminal orientation and the current approved drawing.
Frequently Asked Questions
Q1: What is the maximum system voltage for this wall-through current transformer?
It supports 10kV, 11kV, and 12kV class networks. The epoxy resin casting ensures reliable insulation for indoor medium-voltage switchgear. Confirm your exact system voltage during ordering.
Q2: How should the installation environment be prepared for these cast-resin CTs?
The environment must be clean and stable. Install in indoor switchgear free from severe vibration, corrosive gas, and conductive dust, with ambient temperatures between -5°C and +40°C. Request technical confirmation for high-pollution areas.
Q3: Which primary current ranges are available for the LAZBJ-10 and LFZBJ-10 models?
These models support primary currents ranging from 20A to 400A. Secondary outputs are available in standard 1A or 5A configurations. Specify your exact ratio requirements before procurement.
Q4: What international standards do these indoor current transformers comply with?
They are fully compliant with IEC 60044-1 and GB1208-1997. Units can also be manufactured to optionally meet IEC 61869 standards. Request specific certification documents for your tender.
Q5: Can these transformers be customized for high altitude or coastal installations?
Standard installations are rated up to 1000m altitude. Special environments like coastal or high-pollution areas require technical confirmation. Contact our engineering team to discuss custom design adjustments.
Q6: When is technical confirmation required before ordering these current transformers?
Technical confirmation is required for high altitude, coastal, humid, or high-pollution environments. It is also necessary for specific retrofit conditions. Contact our sales team to verify your project requirements.
Q7: Are these 10kV wall-through CTs compatible with 60Hz power systems?
Yes, they are designed for both 50Hz and 60Hz rated frequencies. The cast-resin insulation maintains performance across both standard grid frequencies. Specify your network frequency when ordering.