A flat electrical cable extends longitudinally along a length of the cable. The flat electrical cable includes a plurality of conductor sets extending along the length of the cable. Each conductor set includes one or more insulated electrical conductors. Each insulated conductor includes a central conductor surrounded by a first dielectric material. The plurality of conductor sets includes a middle conductor set disposed between two other conductor sets and an edge conductor set disposed proximal to a longitudinal edge of the cable. The first dielectric material of each insulated conductor of the edge, but not the middle, conductor set includes an intumescent flame retardant material.