A substation construction crew was installing two feeder breakers at a worksite. The job consisted of adding one 25kV feeder bay with isolation switches on the south end of the existing bus and one 1200A self-contained breaker. The job also included the installation of new 25kV Bus PT (Potential Transformer) module framing on the south end of the bus (framing) and connecting voltage inputs from the PTs to the new feeder breaker. Part of the existing bus was removed to install the new bus. Employee 1 climbed on the top of the substation to take measurements for the bus framing parts. Employee 3 was operating a manlift to lift Employee 1 onto the top of the substation framing. Employee 2 was fabricating the bus framing parts to be installed on the top of the substation framing. A few minutes after climbing onto the substation framing, Employee 1 sustained second and third-degree burns to the arms, hands, and upper torso from an arc flash. Employee 1 was hospitalized.