This article develops an innovative model of shielded cable illuminated by high power electromagnetic pulse based on the tensorial analysis of network. The succinct model under study is competent in quick analysis of the radiated immunity (RI) and signal integrity (SI) considering skew, unbalanced impedance, and other nonideal factors for high-speed application. A Kron's topology graph describing coupling relation among ports of shielded cable is established. The Kron-Branin (KB) general metric of the unbalanced multiconductor cable RI and SI problem is formulated afterward. A 2 m twinax cable over a ground plane is calculated using KB model and the results agree well with the SPICE model and the simulation of CST. Skew, mixed-mode S-parameters variation, and radiation immunity with respect to various typical unbalanced factors are analyzed. The computational efficiency of KB model is compared with the SPICE model and CST. This inventive model provides system designers with a fast calculation tool in frequency domain for performance evaluation of long cable in a harsh electromagnetic environment.