Abstract: A fault is located in an insulated electrical conductor buried in earth by establishing a voltage gradient through the earth emanating from the fault, and thereafter sensing the direction of the gradient to locate the fault. The voltage gradient is established by applying a pulsed voltage initially to the conductor at a voltage level significantly less than the maximum voltage level of which the voltage source is capable. The presence or absence of a voltage gradient as a result of such initial voltage level is sensed and, if no gradient has been established, the voltage level is increased somewhat and reapplied, but at a level still significantly less than the maximum level of which the voltage source is capable. After the voltage gradient has been established, the voltage level varies within a range no higher than the initial voltage level at which the gradient was established, so as to maintain the voltage gradient.