All-electric aircraft (AEA) emergence is considered a promising initiative toward achieving net-zero aviation. Future wide-body AEA will require electric power systems (EPS) with high power density and minimal system mass. Power cables, a crucial element of the aircraft EPS, need to be designed to enhance the EPS's overall power density. At the cruising altitudes of wide-body AEA, the limited heat transfer by convection poses significant thermal challenges for the design of power cables. The challenges are further intensified when employing bipolar medium voltage direct current (MVDC) EPSs, typically consisting of two power cables, negative and positive poles, positioned adjacent. The cable's surface area influences both radiative and convective heat transfers. This book chapter deals with the design, fabrication, and testing of aircraft MVDC power cables. Multilayer multifunctional electrical insulation (MMEI) systems were recently introduced instead of single-layer insulation in the aforementioned cables, which are discussed. In addition to delineating coupled electrical, thermal, and computational fluid dynamic models to obtain thermal distribution and electric stress within the cable and using the model for optimal design of cable and duct geometries, all modeling details in COMSOL Multiphysics are also explained, resulting in this chapter book as a textbook and valuable reference.