Partial discharge Partial discharge In electrical engineering, partial discharge (PD) is a localized dielectric breakdown (DB) of a small portion of a solid or fluid electrical insulation (EI) system under high voltage (HV) stress, which does not bridge the space between two conductors. While a corona discharge (CD) is usually revealed by a relatively steady glow or brush discharge (BD) in air, partial discharges within solid insulation system are not visible. PD can occur in a gaseous, liquid or solid insulating medium. It often starts within gas voids, such as voids in solid epoxy insulation or bubbles in transformer oil. Protracted partial
Vallis (planetary geology) Vallis (planetary geology) Vallis (plural "valles") is the Latin word for "valley". It is used in planetary geology to name landform features on other planets. Scientists used "'vallis" for old river valleys they discovered when they sent the first probes to Mars. The Viking Orbiters caused a revolution in our ideas about water on Mars; finding huge river valleys in many areas. Space craft cameras showed that floods of water broke through dams, carved deep valleys, eroded grooves into bedrock, and traveled thousands of kilometers. Some valles on Mars (Mangala Vallis, Athabasca Vallis, Granicus Vallis, and Tinjar Valles) clearly begin