Portable apparatus for in situ field stator bar insulation capacitance mapping

Abstract

A capacitance mapping tool consisting of an improved capacitance probe head assembly having an inflatable electrode bladder mounted at the end of a telescoping support pole is provided for enabling a service technician to accurately position the probe head assembly between stator bars of a large electric motor or power generator from a remote location. Using the tool, capacitance measurements of insulation on stator bars can be obtained without removing the field. The tool is constructed such that it can be inserted between the field generating component (e.g., the rotor) and the stator windings of a large motor or power generator, thus, precluding the need for field removal. A bendable articulated tip section, which remains in a particular bend arrangement until manually reconfigured, is provided at one end of the tool where the capacitance measuring probe head is attached. This allows the probe head to be, preconfigured at a particular angle with respect to the support pole and the stator bars prior to inserting. The probe head includes a bladder support plate which acts as a spacer and is adapted to accept one or more additional spacer plates for changing the overall width of the probe head to adjust for different spacings between stator bars. The pole supports an electric cable from the probe electrode to a remote electric meter and an air hose to a remote fluid source for inflating/deflating the probe bladder.