Overview
The LFSQ-10 is an indoor single-phase current transformer with a reinforced, fully enclosed epoxy resin cast structure. It is rated for 10kV, 11kV, and 12kV medium-voltage systems, featuring a 12/42/75kV insulation level suitable for IEC 12kV-class switchgear.
Designed for both measurement and protection applications, it supports accuracy classes for metering and 10P-class relay protection. The transformer is intended for use in cart switchboards, handcart switchgear, and metal-clad indoor distribution equipment, complying with IEC 61869-1 and IEC 61869-2 standards.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| Voltage class | 10kV, 11kV, 12kV |
| Highest voltage for equipment | 12kV |
| Rated insulation level | 12/42/75kV |
| Rated frequency | 50Hz / 60Hz |
| Rated secondary current | 5A or 1A |
| Power factor of burden | 0.8 lagging |
| Accuracy for measurement | As per IEC 61869-2 |
| Protection class | 10P |
| Insulation material | Epoxy resin cast |
| Installation type | Indoor, switchgear-mounted |
| Phase configuration | Single-phase |
| Applicable standard | IEC 61869-1 / IEC 61869-2 |
Model Designation
- L: Current transformer
- F: Totally enclosed type
- S: Used for cart switchboard / handcart switchgear application
- Q: Reinforced design / reinforced insulation configuration
- 10: Voltage class identification; applicable to 10kV systems and IEC 12kV-class insulation coordination for 10kV, 11kV, and 12kV projects
Construction
The LFSQ-10 features a robust, fully enclosed construction where the primary winding, secondary winding, and magnetic core are completely encapsulated in reinforced epoxy resin casting insulation. This cast-resin structure provides enhanced dielectric strength, moisture resistance, and anti-pollution performance. The sealed body ensures reliable operation in typical indoor switchgear environments, offering improved thermal and dynamic stability compared to standard indoor current transformers. The compact and lightweight design facilitates flexible mounting orientations within medium-voltage distribution cabinets, supporting integration into cart-type, handcart, and metal-clad switchgear assemblies.
Technical Parameters
Service Conditions
- Installation location: indoor medium-voltage switchgear
- System voltage: 10kV, 11kV, or 12kV class
- Rated frequency: 50Hz / 60Hz
- Rated insulation level: 12/42/75kV
- Altitude: not over 1000m under standard service conditions
- Ambient temperature: -5°C to +40°C
- Relative humidity: less than 85% at 20°C under reference conditions
- Environmental condition: suitable for indoor switchgear with humidity, condensation, and pollution control according to project requirements
Technical Parameters
The LFSQ-10 is a reinforced epoxy resin cast current transformer designed for 10kV–12kV medium-voltage systems. It features epoxy resin casting insulation, operates within an ambient temperature range of -5°C to +40°C, and is rated for altitudes up to 1000m. Compliant with IEC 61869-1/2 (and IEC 60044-1 for legacy applications), it supports primary currents from 5A to 1500A with standard secondary outputs of 1A or 5A.
| Rated Primary Current (A) |
Rated Output (VA) | Rated Short-Time Thermal Current Ith/1s (r.m.s.) |
Rated Dynamic Current Idyn (Peak) |
||
|---|---|---|---|---|---|
| 0.2 | 0.5 | 10P | |||
| 5, 10 | 10 | 10 | 15 | 150 I1n | 2.5 I1n |
| 15~50 | 400 I1n | 2.5 I1n | |||
| 75 | 32 | 90 | |||
| 100~200 | 45 | 100 | |||
| 300 | 10, 15* | 15 | 20 | 63 | 130 |
| 400, 500 | 10, 20* | 20 | 30 | ||
| 600, 800 | 20, 30* | 30 | 40 | ||
| 1000~1500 | 30, 40* | 40 | 40 | ||
Installation & Wiring
Installation Diagram
The LFSQ-10 current transformer is installed on a base plate within indoor cart switchboards or medium-voltage cabinets. Mounting is achieved using four M10 bolts through the base plate, with primary terminals (P1/P2) and secondary terminals (1S1/1S2, optional 2S1/2S2) oriented as per the approved outline drawing. Adequate phase-to-phase and phase-to-ground clearances must be maintained in accordance with the switchgear design and applicable standards.
Selection & FAQs
Selection Guide
- Select the ratio from the 5A–1500A family schedule. Match operating current, expected growth and metering range, then verify that the exact structural version fits the cart or metal-clad switchgear.
- Define the two-core accuracy combination. Published choices include 0.2/0.2, 0.2/0.5, 0.2/10P and 0.5/10P. Specify each core’s purpose, class and rated output.
- Choose burden by ratio rather than from the family maximum. Low-current versions are generally referenced at 10VA measurement and 15VA protection, while 400A–1500A configurations list selected 20VA–40VA outputs.
- Complete the 10P protection calculation. Confirm the required accuracy limit factor, relay input, lead resistance and total burden; the class cannot be finalized from the “10P” label alone.
- Verify corrected fault and installation data. Obtain certified short-time current, duration and peak dynamic current, especially where the source shows a questionable 2.5 × I₁n expression; also confirm M10 mounting, terminal direction and clearances.
Frequently Asked Questions
Q1: Can this epoxy resin CT operate in high humidity?
Yes, subject to environmental controls. It requires relative humidity below 85% at 20°C. Ensure the indoor switchgear manages condensation and pollution according to project requirements.
Q2: What are the short-circuit thermal and dynamic current ratings?
The rated short-time thermal current and dynamic peak current vary by primary rating. Standard outputs support 5A to 1500A primary currents. Please provide your specific primary current for exact factory calculation.
Q3: Which accuracy class is suitable for protective relaying?
The 10P accuracy class is designed for protection applications. It ensures reliable performance during fault conditions with standard 1A or 5A secondary outputs. Confirm the exact burden VA and accuracy limit factor with our engineering team.
Q4: Can this indoor current transformer operate above 1000m altitude?
Standard service conditions limit installation to altitudes not exceeding 1000m. The 12/42/75kV insulation level requires standard atmospheric pressure for optimal performance. Contact our technical team for high-altitude project evaluation and derating details.
Q5: What international standards does this current transformer comply with?
The LFSQ-10 complies with IEC 61869-1 and IEC 61869-2 standards. It also supports IEC 60044-1 for legacy medium-voltage applications. Request the specific type test reports during the procurement phase.
Q6: How do I specify custom primary and secondary currents?
Primary currents range from 5A to 1500A, with standard secondary outputs of 1A or 5A. Rated output VA is available for 0.2, 0.5, and 10P accuracy classes. Specify your exact ratio in the inquiry; factory confirmation is required for non-standard ratios.
Q7: What type of switchgear is this current transformer designed for?
This single-phase epoxy resin CT is specifically designed for indoor medium-voltage switchgear. It suits 10kV, 11kV, and 12kV system classes with a 50Hz or 60Hz rated frequency. Verify panel dimensions and mounting details with the manufacturer before ordering.