Overview
The LAJ-10Q and LFZBJ-10 are 10 kV class through-wall current transformers with cast-resin (epoxy) insulation, designed for medium-voltage AC systems. These electromagnetic instruments provide galvanically isolated secondary current signals proportional to primary current, supporting accurate measurement and protection functions.
Available with accuracy classes including 0.2S, 0.5, and 10P10/10P15, they are suitable for revenue metering, relay protection, and SCADA integration in indoor and outdoor distribution applications. The LAJ-10Q variant is optimized for harsh environments, while all models comply with IEC 61869-1/2, GB/T 20840, and GB 1208-1997 standards.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| System voltage class | 10 kV |
| Rated frequency | 50 Hz or 60 Hz |
| Rated secondary current | 5 A |
| Accuracy classes | 0.2S, 0.2, 0.5, 10P10, 10P15 |
| Rated burden | 10–15 VA (typical) |
| Burden power factor | cosφ = 0.8 (lagging) |
| Short-circuit withstand | Ith: 40 kA (1 s); Idyn: 90 kA (peak) |
| Primary current range | 5 A to 3000 A |
| Applicable standards | IEC 61869-1/2, GB/T 20840.1/2, GB 1208-1997, IEC 60044-1 |
Model Designation
- L: Current Transformer (CT)
- A: Through-wall (bulkhead) mounting
- J: Enhanced mechanical and insulation design
- Q: All-condition variant for harsh environments (LAJ-10Q only)
- F: Cast-resin insulated (epoxy resin casting)
- Z: Busbar-separated structure
- B: Protection function option available
- 10: 10 kV voltage class
Construction
These transformers feature a through-wall (bushing) mounting structure with epoxy resin cast insulation, available in semi-enclosed (≤300 A) or fully sealed (400–800 A) configurations. The core uses high-quality silicon steel laminations in a toroidal arrangement. Primary conductors pass through the central aperture as single-turn, multi-turn, or busbar types, while precision-wound secondary coils are mounted on the core. Secondary terminals (S1/S2, or 1S1/1S2 and 2S1/2S2 for dual-core units) are located at the bottom for easy access and use exposed screw-type connections. The LAJ-10Q employs an enhanced resin formulation for superior resistance to moisture, contamination, and thermal stress in demanding environments.
Technical Parameters
Service Conditions
- Installation environment: Indoor or outdoor installation (LAJ-10Q rated for harsh conditions)
- Altitude: Not exceeding 1000 m above sea level (higher altitude applications require engineering confirmation)
- Ambient temperature: −5 °C to +40 °C
- Relative humidity: ≤ 90% at +20 °C reference temperature
- Environmental conditions: Free from corrosive gases, chemical contamination, or substances affecting insulation performance; no severe vibration, mechanical shock, or impact
- Harsh environment capability: Specifically designed for complex and demanding operational conditions
- Enhanced protection: Superior resistance to moisture, contamination, and thermal cycling
Technical Parameters
The LAJ-10Q and LFZBJ-10 series are cast-resin through-wall current transformers designed for 10 kV class AC systems (50 Hz / 60 Hz). They feature a primary current range of 5 A to 3000 A, operate within an ambient temperature range of −5 °C to +40 °C, and are suitable for installations up to 1000 m altitude. The units comply with standard accuracy classes for metering and protection applications and offer robust short-circuit withstand capabilities.
Current Transformer Data
| Rated Primary Current (A) |
Accuracy Class Combination |
Rated Output (VA) |
Short-Time Thermal Current (kA/1s) |
Dynamic Current (kA) |
||||
|---|---|---|---|---|---|---|---|---|
| 0.2S | 0.2 | 0.5 | 10P10 | 10P15 | ||||
| 5~100 | 0.2S/0.2S 0.2/0.2 0.2S/10P10 0.2/10P10 0.5/10P10 0.2/10P15 0.5/10P15 |
10 | 10 | 10 | 15 | 15 | 100|1n | 250|1n |
| 150 | 13.5 | 34 | ||||||
| 200 | 18 | 45 | ||||||
| 300 | 27 | 67 | ||||||
| 400 | 30 | 75 | ||||||
| 500 | 36 | 90 | ||||||
| 600 | 36 | |||||||
| 750 | 40 | 90 | ||||||
| 800 | ||||||||
| 1000 | – | – | ||||||
| 2000~3000 | ||||||||
Installation & Wiring
Outline Dimensions
Outline dimensions and mounting details vary depending on current rating and structural type (single-turn, multi-turn, or busbar). Through-wall models such as the LAJ-10Q require precise panel cutout dimensions to ensure proper fit and electrical clearance. Always refer to factory-provided dimensional drawings specific to your current rating and variant before installation.
Selection & FAQs
Selection Guide
- Select by both current ratio and physical construction. The page describes semi-enclosed versions up to 300A and fully enclosed versions at 400A–800A, with single-turn, multi-turn or busbar primaries depending on the ratio.
- Treat 1000A–3000A as confirmation ranges. These ratios are listed, but the table omits complete short-circuit values and some 10P15 output data; request a dedicated technical sheet before specification.
- Define the dual-core accuracy combination. Choose 0.2S/0.2S or 0.2/0.2 for two measuring circuits, or pair 0.2S, 0.2 or 0.5 with 10P10 or a confirmed 10P15 protection core.
- Qualify LAJ-10Q for the actual environment. “Harsh environment” or “all-condition” wording does not by itself establish outdoor suitability; verify enclosure, UV, condensation, pollution, creepage and temperature requirements.
- Approve ratio-specific insulation, fault and mounting data. Confirm the full insulation level, thermal-current duration, peak dynamic current, panel cutout, aperture, conductor interface, terminal layout and current standard edition.
Frequently Asked Questions
Q1: Can the LAJ-10Q be installed outdoors in harsh environments?
Yes, the LAJ-10Q is specifically rated for outdoor and harsh operational conditions. It offers superior resistance to moisture and contamination. Contact us for specific environmental verification.
Q2: What primary current ratings are available for these through-wall CTs?
The series supports a primary current range from 5 A to 3000 A. Select the appropriate rating based on your maximum load requirements. Factory customization is subject to confirmation.
Q3: Are these current transformers rated for high short-circuit currents?
Yes, both models feature robust short-circuit withstand capabilities for 10 kV class systems. They ensure reliable protection performance during fault events. Confirm specific thermal and dynamic ratings with our engineers.
Q4: Can these 10kV CTs be installed at high altitudes?
Standard installation is approved for altitudes not exceeding 1000 meters above sea level. For higher altitude applications, derating or special design is required. Please contact us for engineering confirmation.
Q5: What routine factory tests are performed before shipment?
Routine factory testing protocols are applied to ensure baseline performance for 10 kV systems. Specific test certificates and detailed reports are subject to confirmation. Contact our sales team for details.
Q6: How can we request custom accuracy classes for metering?
The units comply with standard accuracy classes for both metering and protection applications. Custom accuracy requirements must be specified during the inquiry stage. Contact us to verify factory capabilities.
Q7: Which applications are suitable for cast-resin through-wall transformers?
These 10 kV class current transformers are ideal for indoor and outdoor AC switchgear systems. They are designed for complex operational conditions requiring enhanced insulation. Review our catalog for manufacturer specifications.
Q8: Are the LFZBJ-10kv models compatible with 60 Hz power systems?
Yes, the LFZBJ-10kv series is designed for both 50 Hz and 60 Hz AC systems. They operate reliably within the -5 °C to +40 °C ambient temperature range. Specify your grid frequency when ordering.