As 10 kV high-voltage modules become more commercialized, the issue of the high electric field becomes urgent. There are many novel ways to reduce the electric field where the multi-layer stacked substrate configuration is a promising solution. However, the voltage of the middle metal layer is easily affected by the layout and operating condition of the top metal layers, especially for half-bridge modules. In this paper, a generalized multiport electric network with individual parallel RC parameters and voltage excitation is proposed to reflect arbitrary layout patterns and voltage waveforms. The corresponding analytical time-dependent model of the middle layer voltage is investigated. Based on it, the multiport network considering oscilloscope probes is further developed. Finally, two stacked-substrate prototypes with different layouts and materials are fabricated to validate the effectiveness and accuracy of the modeling. The experimental results demonstrate that the proposed analytical model can calculate the middle layer voltage with a maximum error of less than 3.0% under sinusoidal, square voltage waveforms, and different module topologies.