Impedance of Pipe-Type Cable

Pipe-type cable involving magnetic enclosures has created new problems for the engineer, in determining the magnitude of fault currents on a system partially composed of circuits of this cable construction. Usually, system analysis follows 1) the determination of the various impedance values for the several parts, and 2) solving for the magnitude of fault current under various conditions. When pipe-type cable installed in steel pipe is involved, the values of impedance turn out to be a function of the current. Thus, their use in a solution becomes complicated since they are a variable of the function being solved. Because of the general lack of information, it was believed that a few curves giving limiting values of impedance functions of pipe-type cable would be of use to engineers for developing circuit analysis.