... laying indoors, in trenches, in ducts, and for fixed installation, the cable should be flame retardantZR-KVVP2Copper conductor PVC ... laying indoors, in trenches, in ducts, and for fixed installation, the cable should be flame retardantZR-KVV2Copper conductor PVC ... indoors, in trenches, in ducts, and underground, the cable should be flame retardant and able to bear beavier extermal mechanical force ...