Tube-insulated shell-core current transformer

A shell core current transformer comprising a tubular main insulator, a magnetic tubular measuring core having inner yokes and a magnetic tubular return core having outer yokes, said main insulator being arranged substantially coaxially between said measuring and return cores, a primary winding within said return core between said outer yokes, a secondary measuring winding within said measuring core between said inner yokes, a protecting core within said measuring core between said inner yokes and disposed coaxially with said main insulator, a protecting secondary winding within said measuring core between said inner yokes and between said protecting core and said main insulator, said secondary measuring winding being between said protecting core and said measuring core, said return core comprising a magnetic return circuit, whereby said primary winding serves both as a primary winding for said measuring core and as a primary winding for said protecting core.