Apparatus and method for detecting current leakage through insulating structure

摘要

Apparatus for separating the amount of resistive leakage current passing through an insulating portion (14) of an aerial boom (12) which is in contact with an electrical line includes a first current collector band (24) and a second current collector band (22). A first current path extends from the first current collector band to ground. A second current path extends from the second current collector band to ground. A first current flows through the first current path due to current that leaks through the insulating portion of the boom as well as capacitance effects. A second current flows through said second current path due to capacitance effects caused by nearby sources of extraneous ambient electrical energy. A converter box (44) converts the first and second currents into representative first and second voltage signals. The first and second voltage signals are transmitted to an electronics and readout box (70) by a pair of shielded cables (50 and 52) or other conventional means such as optical fibers. In the electronics and readout box (70) an adjustable gain circuit (92) adjusts the magnitude of the second voltage signal and the first and adjusted second voltage are passed through a conventional differential amplifier circuit (82) which serves to perform vector subtraction of the voltage signals representative of I1 and I2 and output a resultant difference voltage signal to a display circuit (86). When the gain of the adjustable gain circuit is set to minimize the resultant difference voltage, the difference voltage is the resistive leakage current flowing down the insulating portion (143) of the boom without the ambient capacitively coupled currents.