Partial discharge detection of continuous length wire

The ability to eliminate or minimize defects in high voltage wire can help in extending system reliability by eliminating or minimizing sources of partial discharge. Partial discharge testing of single conductor wire is traditionally performed on discrete lengths of wire or wires terminated to connectors. However, when excessive partial discharge is detected in completed assemblies, expensive rework is the result. Eliminating defects, prior to connector termination and testing, would be beneficial. Existing partial discharge detection methods of wire require the termination of fixed lengths to temporary test connectors. The wire must have a braided shield or similar ground conductor placed around its outer diameter and fixed to the connector. These test connector terminations must be constructed carefully, since discharges resulting from poor terminations cannot easily be differentiated from discharges produced within the wire. Additionally, discharges found within the wire cannot always be localized for removal. A method is presented for partial discharge pulse detection in continuous length wires. Detection of partial discharges may indicate the presence of electrical insulation defects which may result in overstressing by an electric field and/or the occurrence of transient gas ionization, which will erode the insulation and ultimately lead to a reduction in wire reliability and life. This test method offers the advantage of locating wire insulation defects in process, such as small voids, fractures, and separations prior to termination which then can be cut from the spool of wire or otherwise identified. Electrostatic models of the system are analyzed and testing results are discussed related to fluoropolymer insulated wires. A conductor cleaning process and optical detection apparatus, intended to minimize or identify insulation defects caused by contamination, is also presented.