Wireless Power Transfer (WPT) technology has gained substantial research interest owing to its remarkable advantages in operational safety, reduced maintenance requirements, and design flexibility. Nevertheless, the inherently open nature of WPT systems renders the operating magnetic field vulnerable to interference from metallic foreign objects, which introduces critical challenges including degradation of transmission efficiency and potential thermal hazards. This paper presents the design and implementation of a blind-spot-free, highly sensitive, and structurally straightforward detection system specifically tailored for identifying metallic foreign objects in high-power electric vehicle WPT systems utilizing distributed rectangular transmission coils. The research commences with a thorough theoretical analysis, deriving the transmission characteristics of an LCC/S-compensated WPT system and establishing a comprehensive circuit model that quantitatively demonstrates how metallic object intrusion alters coil parameters and consequently impairs power transfer performance. An initial detection approach employing interconnected paired inductor cells was implemented but found to exhibit significant blind zones, leading to an in-depth magnetic field analysis and the subsequent development of an optimized detector featuring an innovative inner-outer loop interconnected architecture. Critical issues such as harmonic responses inherent to the interconnected array are meticulously analyzed and effectively mitigated. Finally, prototype detection coils were fabricated and integrated onto the transmission coil surface, with extensive experimental results validating the system's detection sensitivity, harmonic performance, central region coverage effectiveness, and demonstrating superior performance through a comparative study of interconnected versus independent detection modalities, thereby confirming the system's robustness and practical applicability.