Abstract: This dual voltage transformer comprises a primary winding having a tap at a location intermediate its length, a first termination for connection to line voltage, and a second termination for connection to ground. When the transformer is to be operated at a relatively high voltage, the first termination is connected through a dual voltage switch to line voltage; and when the transformer is to be operated at a relatively low voltage, the tap is connected through said switch to line voltage. First varistor means is connected across the primary winding between said first and second terminations both when the transformer is operated at high voltage and at low voltage; and second varistor means having a lower breakover voltage than the first varistor means is connected between said tap and ground when the transformer is operated at low voltage.

Abstract: A dual voltage distribution transformer is protected by an internally installed, multi-rated surge arrester which is selectively connected with plural primary windings by a dual voltage switch such as to establish a high surge voltage protection level when the primary windings are connected in series by the switch and a correspondingly lower surge voltage protection level when the primary windings are connected in parallel by the switch.