Abstract: A three-phase transformer including a transformer housing, a shell-form five-limb transformer core wherein main limbs include two outer main limbs and a middle main limb, three coil arrangements including two outer coil arrangements each arranged around a respective one of the outer main limbs, and a middle coil arrangement arranged around the middle main limb. The outer coil arrangements have an inter-coil insulation configured to electrically insulate the coil arrangements from the transformer housing and from the respective other ones of the coil arrangements, and wherein no inter-coil insulation is provided to the middle coil arrangement.

Abstract: A transformer arrangement includes a transformer having a winding and a surge arrester arrangement connected thereto. The SAA includes a surge arrester (SA) connected across at least a section of the winding and a switch operable between a closed and open state. In the closed state, SA is electrically connected across at least the section, and in the open state, the SA electrically disconnected from at least the section. The SAA includes at least one further SA arranged to be connected across at least one further section and at least one further switch, operable between a closed and open state, wherein in the closed state the further SA is electrically connected across the at least one further section, and in the open state, the at least one further SA is electrically disconnected from the further section. A method for electrically connecting/disconnecting the transformer to/from the SAA—is also described.

Abstract: A three-phase transformer including a transformer housing, a shell-form five-limb transformer core wherein main limbs include two outer main limbs and a middle main limb, three coil arrangements including two outer coil arrangements each arranged around a respective one of the outer main limbs, and a middle coil arrangement arranged around the middle main limb. The outer coil arrangements have an inter-coil insulation configured to electrically insulate the coil arrangements from the transformer housing and from the respective other ones of the coil arrangements, and wherein no inter-coil insulation is provided to the middle coil arrangement.

Abstract: A transformer core frame is provided with a reinforcement structure to form a reinforced transformer core frame. The reinforcement structure comprises one or several reinforcement panels comprising a honeycomb structure and affixed to the transformer core frame. A method of producing a reinforced transformer core frame is also described.