High-Precision and Stability Solutions for Low-Voltage Current Transformers (LV CT)

I. Solution Background
In high-precision applications such as smart grids, renewable energy metering, and industrial power monitoring, conventional low-voltage current transformers (LV CTs) often face challenges including insufficient accuracy, significant temperature drift, and poor long-term stability. To meet the 0.2S/0.5S-class high-precision metering requirements, this solution proposes a comprehensive improved design for electromagnetic LV CTs through core material innovation and structural optimization.

II. Core Technical Solutions

1. Upgraded High-Permeability Core Materials
   Nanocrystalline/Amorphous Alloy Ultra-Thin Strips:
   Cores are wound using 0.02–0.025mm thick nanocrystalline or amorphous alloy strips, achieving an initial permeability (μi) of over 1.5x10⁵ H/m. This significantly reduces excitation current and minimizes ratio/phase errors.
   Magnetic Domain Optimization:
   Directional magnetic field annealing eliminates core stress, enhances flux uniformity, and reduces hysteresis losses under high-frequency harmonics.

2. Magnetic Shielding and Anti-Interference Structures
   Multi-Layer Composite Magnetic Shielding:
   Dual Permalloy + copper mesh shielding layers are added around the core to suppress external AC magnetic field interference and mitigate DC bias effects.
   Orthogonal Winding Process:
   Segmented orthogonal winding technology for secondary windings reduces distributed capacitance and leakage inductance, improving frequency response (accuracy deviation < ±0.1% within 1–5kHz bandwidth).

3. Temperature Compensation and Signal Processing
   Dynamic Temperature Compensation Circuit:
   Integrated high-linearity NTC/PTC sensors real-time compensate for temperature drift in core permeability and winding resistance (temp. drift coefficient ≤ ±10 ppm/°C).
   High-Stability Sampling Resistor:
   Low-drift metal foil resistors (ΔR/R < ±5 ppm/°C) with four-terminal Kelvin connections ensure current-to-voltage conversion accuracy.

4. Encapsulation and Insulation Reinforcement
   Vacuum Potting Process:
   High-purity epoxy resin potting at 10⁻³ Pa eliminates bubbles and internal stress, enhancing mechanical strength and thermal stability.
   Multi-Layer Insulation Architecture:
   Polyimide film + silicone composite interlayer insulation achieves dielectric strength >15 kV/mm and partial discharge <5 pC (@1.5Ur).

III. Performance Advantages

IV. Application Scenarios
This solution is particularly suited for:
&bull; Power Metering: Smart meters, distribution network automation systems (compliant with IEC 61869-2 standard)
&bull; Renewable Energy Monitoring: High-precision current sampling in PV inverters and energy storage systems
&bull; Industrial Control: Fault current detection in VFDs and motor protection devices
&bull; Lab Standards: Serving as 0.2S-class standard transformers for value transfer