Overview
The LFS-10Q / LFSB-10 / LFSZ-10 is a compact indoor epoxy cast-resin medium-voltage current transformer designed for 11kV class switchgear, with documentation supporting use in 10kV, 11kV and 12kV systems based on insulation level and project requirements. It features fully enclosed post-type construction with epoxy resin insulation, providing high dielectric strength, moisture resistance, and anti-pollution performance.
This single-secondary-winding CT supports typical accuracy classes of 0.2, 0.5 and 10P10, making it suitable for current measurement, energy metering, relay protection, and feeder monitoring in space-constrained indoor switchgear applications such as handcart panels, compact distribution cabinets, and metering units.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| Voltage class | 10kV / 11kV / 12kV |
| Insulation level | 12/42/75kV |
| Frequency | 50Hz (60Hz by confirmation) |
| Primary current | 50A to 630A |
| Secondary current | 5A or 1A |
| Accuracy classes | 0.2, 0.5, 10P10 |
| Winding configuration | Single secondary winding |
| Application | Metering, measurement, protection |
| Indoor/outdoor | Indoor only |
| Construction type | Epoxy cast-resin, post-type |
| Mounting | Cabinet base mount |
| System compatibility | AC power systems up to 12kV |
Model Designation
- L: Current transformer
- F: Enclosed type structure
- S: Handcart switchgear / switchgear application reference
- B: Protection function reference in LFSB-type designation
- Z: Cast-resin insulation / epoxy casting reference in LFSZ-type designation
- 10: 10kV catalogue voltage class; documented for 11kV and 12kV class systems by insulation confirmation
- Q: Reinforced insulation variant
Construction
The LFS-10Q / LFSB-10 / LFSZ-10 current transformer features a fully enclosed post-type structure with epoxy cast-resin insulation. The primary conductor passes through the center of the unit, while the secondary winding is embedded within the resin body. This monolithic construction ensures excellent mechanical stability, electrical insulation, and environmental protection against humidity and contamination commonly found in indoor switchgear environments. The compact design includes top-mounted primary terminals and bottom-mounted secondary terminals, facilitating straightforward installation and wiring within confined cabinet spaces. The resin material provides long-term reliability without requiring maintenance, making it well-suited for continuous operation in medium-voltage indoor power distribution systems.
Technical Parameters
Service Conditions
- Installation location: indoor medium-voltage switchgear
- System voltage: 10kV, 11kV and 12kV class systems
- Rated frequency: 50Hz
- Ambient temperature: -5°C to +55°C
- Installation environment: should be free from severe vibration, conductive dust, corrosive gas, explosive medium, heavy pollution and abnormal condensation.
- Special environments: For high altitude, coastal, humid, or heavy-pollution projects, insulation distance and creepage coordination should be confirmed before ordering.
Technical Parameters
The LFS-10Q, LFSB-10, and LFSZ6-10 are compact epoxy cast-resin current transformers designed for indoor 10kV-class systems. They feature a rated insulation level of 12/42/75kV, operate within an ambient temperature range of -5°C to +55°C, and comply with IEC 61869-2 and GB20840.2-2014 standards. Primary current ranges from 50A to 630A, with secondary options of 1A or 5A.
| Rated primary current (A) |
Accuracy classed combination |
Rated Output (VA) |
Short-time thermal current Ith (kA) |
Rated dynamic current Idyn (kA) |
||
|---|---|---|---|---|---|---|
| 0.2 | 0.5 | 10P10 | ||||
| 50 | 0.2 0.5 10P10 |
10 | 15 | 10 | 7.5 | 19 |
| 75 | 11.25 | 28 | ||||
| 100 | 15 | 37.5 | ||||
| 150 | 22.5 | 56 | ||||
| 200 | 30 | 75 | ||||
| 300 | 40 | 100 | ||||
| 400 | ||||||
| 500 | ||||||
| 600 | ||||||
| 630 | ||||||
Installation & Wiring
Installation Diagram
The LFS-10Q, LFSB-10 and LFSZ-10 current transformers are designed for compact indoor switchgear installation. Mounting is achieved through base mounting holes as shown in the approved outline drawing. Ensure primary terminal spacing, secondary wiring direction, phase-to-ground clearance, and maintenance access align with the switchgear layout before cabinet production.
Selection & FAQs
Selection Guide
- Choose LFS-10Q, LFSB-10 or the specified LFSZ model from the approved tender designation, outline and intended metering/protection role.
- Select 50A–630A primary current from load and fault study, then choose a 1A or 5A secondary compatible with the device.
- Because the page specifies one secondary winding, select one class—0.2/0.5 measurement or 10P10 protection—for each CT.
- Verify the corresponding 10VA or 15VA output and calculate the instrument/relay plus lead burden.
- Check ratio-specific withstand, 12/42/75kV insulation, Class II pollution, base holes, terminals, clearance and +55°C environment.
Frequently Asked Questions
Q1: Which indoor applications suit these epoxy cast-resin current transformers?
They are designed for indoor medium-voltage switchgear in 10kV to 12kV systems. Ensure the installation environment is free from severe vibration and corrosive gases.
Q2: Can these 10kV CTs operate in high humidity environments?
Standard models require environments free from abnormal condensation and heavy pollution. For high altitude or humid coastal projects, insulation distance and creepage coordination require factory confirmation.
Q3: What is the short-circuit withstand capacity for the 630A model?
Short-time thermal and dynamic current ratings vary by primary current rating. Specific short-circuit withstand values for the 630A model are subject to factory confirmation. Please contact us for the complete datasheet.
Q4: Are these current transformers certified to international standards?
Yes, the LFS-10Q, LFSB-10, and LFSZ6-10 models comply with IEC 61869-2 and GB20840.2-2014 standards. Factory test certificates are provided upon shipment to verify compliance.
Q5: How do I specify secondary current options during ordering?
Standard secondary options include 1A and 5A outputs. Specify your required secondary current and accuracy class combination during the inquiry process for factory verification.
Q6: Why select the 10P10 accuracy class for protection?
The 10P10 class ensures reliable performance for protection relays during fault conditions. It maintains accuracy up to 10 times the rated current. Confirm specific burden requirements with our engineering team.