Publications

Development of a radioimaging diagnostic for high-voltage component reliability testing and electrical breakdown computational model validation is described. Radioimaging has its roots in radio astronomy, where aperture synthesis (also known as synthesis imaging) has been utilized for decades to image radio sources far from Earth. Radioimaging as described herein, in contrast, seeks to image radio sources in close proximity to its receivers (i.e., in a laboratory environment). Here it is shown that corona discharge, a non-destructive precursor to catastrophic (thermal) arc discharge, electromagnetically radiates strongly within a 250 kHz – 2.5 GHz bandwidth, and is readily detected and located by postprocessing the received radio signals. The ability of radioimaging to detect both corona and arc discharge (grouped together herein as high voltage breakdown or HVB) makes it a valuable tool for 100% HVB detection in materials, components, and devices, and has the ability to indicate electrical weakness (via corona detection) prior to a destructive arc discharge event. Radioimaging enables HVB to be located both internal and external to dielectric components under test in near-real-time, with multiple and/or extended HVB events located simultaneously. In contrast, existing non-destructive diagnostics (at the time of this writing) either indicate electrical breakdown without resolving failure locations (e.g., current, voltage, and chemical measurements), locate external HVB (e.g., high-speed optical and ultraviolet (UV) measurements or photography), or locate both external and internal HVB but with low fidelity (e.g., a single HVB source can be located by existing time-of-arrival (TOA) UHF or acoustic emissions). Radioimaging instead creates a sequence of high-fidelity images similar to an optical high-speed camera but at radiofrequencies (RF), and is not limited to two-dimensions. Moreover, radioimaging has already served one internal and two external industry customers, the results of which are detailed in this report. The radioimaging results described herein were part of a three-year effort funded by the Sandia Lab Directed Research and Development (LDRD) program within the Radiation, Electromagnetic, High Energy Density Science (REHEDS) investment area.

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Surface flashover is a significant issue impacting the reliability of high voltage, high current gas switches. The goal of this work is to determine if poly(dicyclopentadiene) (pDCPD) coatings can be used to mitigate surface flashover on insulators compared to crosslinked polystyrene (Rexolite), cast poly-methylmethacrylate) (PMMA), and extruded PMMA. The pDCPD coating is expected to have a higher flashover voltage threshold to an initial flashover due to the oxidation of the polymer, creating trap sites for any free electrons that would otherwise serve as primary electrons in a surface electron avalanche. This is tested by measuring the flashover threshold for different extents of oxidation caused by thermally treating the samples for different durations. For subsequent flashover events the pDCPD coating is also expected to have a higher flashover threshold due to its high oxygen/hydrogen to carbon ratio, which is expected to preferentially create gaseous products, such as CO2 after a flashover event, rather than conductive carbon deposits. The control and pDCPD-coated test coupons are repeatedly subjected to increasing voltage stresses until flashover occurs to determine both the initial and subsequent flashover thresholds.

Abstract not provided.