An electrical power assembly comprises a motor lead with individual metal sheathed conductors, a power cable with individual metal sheathed conductors and a splice connector for connecting each of the conductors. Each splice connector has a tubular metal fastener body with an upward facing shoulder at an upper end and a downward facing shoulder at a lower end. A metal nut assembly is fixed to one of the power cable conductors with a downward facing shoulder in metal-to-metal sealing engagement with the upward facing shoulder of the fastener body. A metal coupler fixed to one of the motor lead conductors with an upward facing shoulder in metal-to-metal sealing engagement with the downward facing shoulder of the fastener body. Contacts electrically connect one of the motor lead conductors to one of the power cable conductors within the fastener body. An elastomeric seal disposed between the nut assembly and the fastener body, has expansion relief voids operable to collapse and relieve stresses exerted by the seal when the seal undergoes thermal expansion.