AIS CT Cost Optimization Design Scheme: A Cost-Effective Solution for Small and Medium-Sized Substations

In the construction of small and medium-sized substations, particularly in scenarios highly sensitive to cost such as rural grid upgrades and distributed photovoltaic step-up stations, controlling equipment procurement costs is critical. The Current Transformer (CT), as a key measurement and protection component within Air Insulated Switchgear (AIS), offers significant economic benefits through cost-optimized design. This solution achieves a substantial reduction in CT manufacturing costs through systematic innovation, while guaranteeing core performance standards (Class 0.5 accuracy, Protection (P) class).

​Core Optimization Strategies​

1. ​Material Cost Reduction Engineering: Stepped Lamination Core Technology​
• ​Innovation:​​ Breaks away from the traditional single-material core design by employing a stepped lamination technique. High-performance silicon steel sheet DQ151-30 (low loss, high permeability) is used in the core's central region, where magnetic flux density is high and measurement accuracy is critical. Cost-effective conventional silicon steel sheet DR510-50 is substituted in the peripheral regions where magnetic flux density is relatively lower.
• ​Benefit:​​ Maximizes material utilization. Maintains high measurement accuracy in the critical core area while significantly reducing costs in the peripheral regions. Achieves a direct 22% reduction in core material cost, with overall accuracy consistently meeting Class 0.5 requirements. This process breakthrough resolves the conflict between cost reduction and accuracy maintenance.
2. ​Topology Innovation: Single-Core Multi-Tap CT​
• ​Innovation:​​ Revolutionizes the conventional practice of one core corresponding to one accuracy/protection winding by developing an integrated "single-core multi-tap" design. Through precision magnetic circuit partitioning within a single core, multiple independent winding functions can be simultaneously achieved (e.g., 0.2S class (high-precision measurement) / 0.5S class (metering) / 5P20 class (protection)).
• ​Benefit:​​ This structure drastically reduces the number of cores required in traditional designs. Testing verifies a reduction of approximately 40% in total core volume for equivalent functional configurations. This not only lowers raw material costs but also reduces the overall product size, making it better suited to the compact space requirements of AIS cabinets in small and medium-sized substations.
3. ​Automated Production Process: Robotic Precision Winding​
• ​Innovation:​​ Fully implements high-precision six-axis industrial robots to replace manual operation in the critical coil winding stage.
• ​Benefit:​​ Robot winding positional accuracy is controlled within a tolerance of ±0.05mm. The exceptional consistency and stability result in production defect rates plummeting from 3% (in traditional processes) to below 0.2%. This significant improvement in yield directly reduces quality loss and rework costs, ensuring efficient and stable mass production.

​Comprehensive Benefits and Application Scenarios​

• ​Significant Cost-Effectiveness:​​ Through the synergistic effect of material, structural, and process innovations, this solution achieves an overall manufacturing cost reduction of 35% for AIS CTs compared to traditional schemes. This substantial reduction provides strong support for optimizing the project's total equipment cost (Balance of Plant - BOP).
• ​Performance Guaranteed:​​ All optimizations are rigorously implemented while strictly guaranteeing core performance indicators (Class 0.5 accuracy, P-class protection characteristics), complying with relevant IEC/GB standards.
• ​Core Application Scenarios:​​
• ​Rural Grid Upgrade Projects:​​ Highly cost-sensitive, where this solution can effectively reduce investment in distribution automation construction.
• ​Distributed Photovoltaic (PV) Step-Up Stations:​​ Small and medium-capacity PV projects are typically small-scale with long payback periods, creating an urgent demand for cost-effective equipment.
• ​Compact User Substations / Prefabricated Substations:​​ Require high standards for both equipment footprint and cost.
• ​Other Small/Medium-Sized AIS Substations with Strict Cost Control Requirements.​