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Introduction
The LAJ-10Q, 11kV current transformer represents advanced instrument transformer technology for precision current measurement and system protection in medium-voltage power distribution networks. Engineered with oil-immersed insulation technology, this current transformer delivers exceptional accuracy and long-term reliability for outdoor installations operating at 11 kV nominal system voltage (IEC highest system voltage Um = 12 kV).
Designed for demanding applications in utility substations, industrial facilities, and commercial power systems, the LAJ-10Q, incorporates state-of-the-art magnetic core materials, vacuum-cast insulation technology, and precision manufacturing techniques to ensure compliance with the most stringent international standards including IEC 61869, GB/T 20840, and IEEE C57.13.
Technical Specifications
The following table summarizes key technical parameters for the LAJ-10Q,. Custom configurations available upon request to meet specific application requirements.
| Parameter | Specification |
|---|---|
| Model Number | LAJ-10Q, |
| Product Type | Current Transformer |
| Rated System Voltage | 11 kV (IEC Um = 12 kV) |
| Rated Frequency | 50 Hz (60 Hz available on request) |
| Rated Insulation Level | 12/42/75 kV (Um/AC/LI) for 11kV class |
| Installation Type | Outdoor |
| Insulation Material | Oil-immersed |
| Rated Primary Current | Multiple ratios available (2026/01/5A or /1A) |
| Rated Secondary Current | 5A or 1A (selectable) |
| Accuracy Classes (Metering) | 2S, 1s, 1S, 0.2S, 10P per IEC 61869-2 |
| Accuracy Classes (Protection) | 5P, 10P per IEC 61869-2 |
| Rated Burden | 5-30 VA (selectable based on application) |
| Short-Time Thermal Current (Ith) | 25 kA for 3 seconds (standard) |
| Dynamic Current (Idyn) | 63 kA peak (standard) |
| Partial Discharge | <10 pC at 1.2 × Um/√3 |
| Temperature Rise | <50K at rated current (Class F insulation) |
| Thermal Class | Class F (155°C maximum) |
| Creepage Distance | ≥25 mm/kV (per IEC 60815) |
| Clearance | ≥125 mm for 12 kV (per IEC 61869) |
| IP Protection | IP54 (indoor), IP65 (outdoor version) |
| Pollution Class | Class II (indoor), Class III (outdoor) |
| Service Life | >25 years under normal operating conditions |
Design Features and Construction
Core and Winding Design
The LAJ-10Q, utilizes high-permeability magnetic core material to minimize excitation current and ensure accurate current/voltage transformation across the entire operating range. The core is manufactured from cold-rolled grain-oriented silicon steel with step-lap joint construction to reduce core losses and magnetic noise.
Primary and secondary windings are precision-wound using high-conductivity electrolytic copper conductor with appropriate insulation class. The winding arrangement is optimized to minimize leakage reactance and ensure accurate ratio and phase angle characteristics.
Insulation System
The Oil-immersed insulation system provides superior dielectric strength and thermal performance. Manufacturing utilizes vacuum pressure impregnation (VPI) or vacuum casting technology to eliminate voids and ensure complete impregnation, resulting in:
- Excellent partial discharge performance (<10 pC)
- Superior moisture resistance
- High mechanical strength
- Long-term thermal stability
Key Features
- Fully-enclosed design: Complete protection against environmental contaminants, dust, and moisture ingress. IP54 or higher protection class ensures reliable operation in harsh industrial environments.
- Low partial discharge performance: Partial discharge level <10 pC ensures long insulation life and prevents premature insulation degradation. Critical for high-reliability applications.
- Compact design: Space-efficient footprint reduces switchgear dimensions. Ideal for retrofit applications and installations with space constraints.
Applications
The LAJ-10Q, is suitable for a wide range of 11kV power system applications:
- Switchgear systems: Integration with medium-voltage switchgear panels. Compact design enables space-efficient switchgear construction.
- Utility distribution networks: Electric utility distribution systems for power delivery to commercial and residential customers. Meets strict utility accuracy requirements.
- Chemical plants: Petrochemical and chemical processing facilities. Anti-corrosion features protect against chemical atmospheres.
- Steel mills: Steel production facilities with arc furnaces and rolling mills. Handles high harmonic content and load fluctuations.
Installation Guidelines
Mounting Requirements
- Location Selection: Install in location with adequate ventilation, free from excessive vibration, and protected from direct weather exposure (for indoor version).
- Mounting Surface: Ensure mounting surface is level, structurally sound, and capable of supporting the unit weight with appropriate safety margin.
- Clearances: Maintain minimum electrical clearances per IEC 61869 and local regulations:
- Phase-to-phase: ≥125 mm for 12 kV
- Phase-to-ground: ≥125 mm for 12 kV
- Maintenance access: ≥800 mm minimum
- Orientation: Mount in designated orientation with polarity markings visible and accessible.
Secondary Wiring
- Conductor Size: Use minimum 2.5 mm² copper for 5A secondary circuits, 1.5 mm² for 1A circuits. Verify voltage drop is within limits for your application burden.
- Grounding: Ground secondary circuit at ONE point only to prevent dangerous voltages while avoiding ground loops.
- Polarity: Observe polarity markings when connecting to meters and relays. Incorrect polarity will cause measurement errors and potential protection misoperation.
- CT Secondary Safety: CRITICAL: Never open-circuit CT secondary while primary is energized. This can produce lethal voltages (several kV). Always short-circuit CT secondary before disconnecting any device.
Operating Conditions
| Parameter | Standard Range | Extended Range (on request) |
|---|---|---|
| Ambient Temperature | -25°C to +55°C | -40°C to +70°C |
| Altitude | ≤1000 m above sea level | Up to 4000 m (with derating) |
| Relative Humidity | ≤95% (24h average) | Tropical version available |
| System Frequency | 50 Hz ±2% | 50/60 Hz dual frequency |
| Harmonic Distortion | ≤10% THD | Extended range for VFD applications |
Altitude Correction: For installations above 1000m, insulation strength decreases approximately 1% per 100m. Consult factory for altitude correction factors.
Standards Compliance and Certifications
The LAJ-10Q, complies with the following international and national standards:
- IEC 61869
- GB/T 20840
- IEEE C57.13
Type Tests Performed
Each product design undergoes comprehensive type testing including:
- Temperature Rise Test: Verification of thermal performance at rated current
- Impulse Voltage Test: Lightning impulse withstand capability (75 kV peak for 11kV class)
- Power Frequency Withstand Test: 42 kV rms for 60 seconds
- Partial Discharge Measurement: Verification of <10 pC at 1.2 × Um/√3
- Accuracy Test: Ratio and phase angle error verification at multiple current/voltage points
- Short-Circuit Withstand Test: Thermal and dynamic current withstand verification
Type test certificates available upon request.
Safety Precautions
⚠️ DANGER: Working with 11kV equipment involves lethal voltages. Only qualified personnel should perform installation, operation, and maintenance.
- Qualified Personnel: All work must be performed by personnel trained in medium-voltage equipment safety procedures.
- PPE Requirements: Use appropriate personal protective equipment including insulated gloves (Class 00 or higher), arc-flash suit, face shield, and insulated tools.
- Lockout/Tagout: Follow established lockout/tagout procedures before working on equipment.
- CT Secondary Safety: Never open-circuit CT secondary while energized. Always short-circuit before disconnecting.
- Grounding: Ensure proper grounding of equipment and secondary circuits.
- Approach Distances: Maintain safe approach distances per OSHA or local regulations.
Ordering Information
When ordering the LAJ-10Q,, please specify:
- Model number and product type
- Primary/secondary ratio
- Accuracy class (metering and/or protection)
- Rated burden (VA)
- Installation type (indoor/outdoor)
- Special requirements (altitude, temperature, etc.)
Technical Note: Specifications subject to change without notice. Consult factory for application-specific requirements and latest technical data. All dimensions and weights are approximate.