Overview
The LFZBJ7-11kV is an indoor wall-through epoxy cast-resin current transformer designed for 11kV and 12kV class medium-voltage switchgear systems. It features a solid epoxy resin insulation system that ensures high dielectric strength, mechanical robustness, and moisture resistance suitable for indoor environments.
This transformer supports combined metering and protection functions with accuracy classes such as 0.2/10P10, 0.5/10P10, 0.2/10P15, and 0.5/10P15. It is used in AC power systems at 50Hz for current measurement, energy metering, relay protection, and busbar feeder monitoring. The design complies with standard insulation levels of 12/42/75kV and accommodates secondary outputs of 5A, 1A, or 2A.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| Voltage class | 11kV and 12kV |
| Rated insulation level | 12/42/75kV |
| Rated frequency | 50Hz |
| Primary current range | 5A to 1200A |
| Secondary current | 5A, 1A or 2A |
| Metering accuracy | 0.2 or 0.5 |
| Protection class | 10P10 or 10P15 |
| Insulation material | Epoxy cast-resin |
| Mounting type | Wall-through |
| Application | Indoor switchgear |
Model Designation
- L: Current transformer
- F: Wall-through / through-type structure
- Z: Epoxy resin casting insulation
- B: Protection-class configuration available
- J: Enhanced / reinforced cast-resin design reference
- 7: Design sequence code
- 11kV: International voltage-class positioning for 11kV / 12kV switchgear
- 10 / 10L: Catalogue variant references with different outline dimensions
Construction
The LFZBJ7-11kV features a compact wall-through body made of epoxy cast-resin, providing excellent electrical insulation and mechanical stability. The primary conductor passes directly through the center of the transformer, with extended primary terminals on both sides for secure busbar connection. A square mounting flange allows for panel or partition installation, while the secondary windings are terminated at a clearly separated front-mounted terminal block. The resin-cast construction ensures resistance to humidity, dust, and thermal cycling typical in indoor switchgear environments. Two variants—standard (LFZBJ7-10) and extended-length (LFZBJ7-10L)—share identical electrical characteristics but differ in physical depth to accommodate varying cabinet layouts.
Technical Parameters
Service Conditions
- Installation location: indoor medium-voltage switchgear
- System voltage: 10kV, 11kV and 12kV class networks
- Rated frequency: 50Hz
- Ambient temperature: -5°C to +40°C
- Installation environment: should be free from severe vibration, conductive dust, corrosive gas, explosive medium, heavy pollution and abnormal condensation.
Technical Parameters
The LFZB7-10 and LFZBJ7-10L are indoor epoxy cast-resin current transformers designed for 10kV/11kV class systems. They feature epoxy resin insulation and comply with IEC and GB standards. Primary current ranges from 5A to 400A.
LFZB7-10
| Rated primary current (A) |
Accuracy classed combination |
Rated Output (VA) |
1s thermal current (kA) |
Dynamic current (kA peak) |
||
|---|---|---|---|---|---|---|
| 0.2 | 0.5 | 10P | ||||
| 5 | 0.2/10P10 0.5/10P10 |
10 | 10 | 15 | 0.45 | 1.1 |
| 10 | 0.9 | 2.2 | ||||
| 15 | 1.35 | 3.3 | ||||
| 20 | 1.8 | 4.5 | ||||
| 30 | 2.7 | 6.75 | ||||
| 40 | 3.6 | 9 | ||||
| 50 | 5 | 12.5 | ||||
| 75 | 7.5 | 18.8 | ||||
| 100 | 10 | 25 | ||||
| 150 | 15 | 37.5 | ||||
| 200 | 20 | 50 | ||||
| 300 | 30 | 75 | ||||
| 400 | 40 | 100 | ||||
LFZBJ7-10L
| Rated primary current (A) |
Accuracy classed combination |
Rated Output (VA) |
1s thermal current (kA) |
Dynamic current (kA peak) |
||
|---|---|---|---|---|---|---|
| 0.2 | 0.5 | 10P | ||||
| 5 | 0.2/10P15 0.5/10P15 0.2/10P10/10P10 0.5/10P10/10P10 |
10 | 20 | 25 | 0.7 | 1.75 |
| 10 | 1.5 | 3.75 | ||||
| 15 | 1.8 | 4.7 | ||||
| 20 | 2.8 | 7 | ||||
| 30 | 4.4 | 11 | ||||
| 40 | 5.5 | 13.8 | ||||
| 50 | 6.3 | 15.8 | ||||
| 75 | 9.5 | 23 | ||||
| 100 | 15 | 37.5 | ||||
| 150 | 20 | 50 | ||||
| 200 | 30 | 75 | ||||
| 300 | 36 | 90 | ||||
| 400 | 40 | 100 | ||||
Installation & Wiring
Installation Diagram
The LFZBJ7-11kV current transformer is designed for indoor wall-through installation with direct busbar connection. The unit is mounted on a switchgear panel wall via a mounting plate, with the primary conductor passing through the central aperture. Secondary terminals are accessible from the front or side as specified in the approved outline drawing.
Selection & FAQs
Selection Guide
- Choose the 420mm standard body or 450mm long-body variant from partition depth, busbar geometry, winding count and required burden.
- Select a listed 5A–400A ratio from load and fault studies; treat 600A–1200A as project-specific until fully documented.
- Choose 1A, 2A or 5A and specify two or three independent 0.2/0.5 metering and 10P10/10P15 protection cores.
- Verify per-core outputs: standard versions list 10VA measurement/15VA protection, while long-body versions list up to 20VA/25VA.
- Confirm exact thermal/dynamic duty, 12/42/75kV insulation, flange cutout, busbar terminals, 22kg support and +55°C environment.
Frequently Asked Questions
Q1: Can this indoor current transformer be applied in 11kV networks?
Yes, subject to system verification. The LFZBJ7-11kV is designed for 10kV, 11kV, and 12kV class systems at 50Hz. Please confirm exact system voltage with our engineering team.
Q2: Where should this epoxy cast-resin CT be installed?
Indoor installation is required, free from severe vibration, corrosive gas, and conductive dust. Ambient temperature must remain between -5°C and +40°C. Contact us for site-specific environmental assessments.
Q3: How is the short-circuit thermal current rated for a 40A primary?
The rated short-time thermal current for a 40A primary is 3.6kA, with an 11kA peak dynamic current. These parameters comply with IEC and GB specifications. Confirm specific short-circuit durations with our engineers.
Q4: Which accuracy class combination is available for this 10kV current transformer?
Standard accuracy class combinations include 0.2/10P10 and 0.5/10P10. Rated outputs are 10VA for 0.2 and 0.5 classes, and 15VA for 10P. Specify your metering and protection requirements during ordering.
Q5: Is the primary current customizable beyond 400A?
Standard primary currents range from 5A to 400A. Custom ratings above 400A are subject to factory confirmation and engineering review. Please contact our sales team with your specific project requirements.
Q6: Are there specific IEC standards for this indoor transformer?
The LFZB7 series complies with both IEC and GB standards for indoor epoxy cast-resin current transformers. Factory test certificates are provided upon request. Contact us for specific certification documentation.
Q7: When is the LFZBJ7-11kV suitable for medium-voltage switchgear?
It is specifically designed for indoor medium-voltage switchgear in 10kV to 12kV networks. Applied for metering and protection in industrial power distribution. Check with our manufacturer for project-specific application guides.