Modelling and Optimization of Four-Segment Shielding Coils of Current Transformers

Area of Science:

• Electrical Engineering
• Electromagnetics
• Power Systems

Background:

• Large-capacity generators require protection for current transformers (CTs) against magnetic interference from adjacent bus-bars.
• Shielding coils offer a practical solution for mitigating this electromagnetic interference.

Purpose of the Study:

• To develop a simplified analytical model for shielding coils to enable effective optimization.
• To analyze the performance of different shielding coil configurations for current transformers.

Main Methods:

• Development of a new analytical model for partial coil leakage flux, building upon existing stray flux models.
• Utilization of finite element method (FEM) simulations to derive empirical equations for core-pickup factors.
• Theoretical analysis of four-segment shielding coils in a six-bus-bar system.

Main Results:

• The "all parallel" shielding coil configuration with a 45° starting position demonstrated superior shielding performance.
• The "separated loop" configuration with a 0° starting position exhibited the lowest heating value.
• Experimental validation confirmed the accuracy of the developed analytical models and derived conclusions.

Conclusions:

• The proposed analytical model provides an effective tool for optimizing shielding coil designs for current transformers.
• Optimal shielding coil configurations can be determined to balance performance and thermal characteristics.
• The analytical approach is adaptable for evaluating various shielding coil configurations beyond the four-segment design.