Surface Potential Behavior of Direct-Fluorinated PPLP Under Quench Condition

With the emergence of superconductor technology, high-temperature superconducting (HTS) cable is receiving considerable attention for application in power systems. Polypropylene laminated paper (PPLP) and liquid nitrogen (LN
₂
) have been widely used as insulation and coolant, respectively, in HTS cable systems, where the insulation is threatened by surface charge and quench. Direct fluorination is an effective method to improve the electrical properties on the material surface. To restrain the surface charge accumulation and prolong the insulation life, the surface potential behaviors of fluorinated PPLP under the quench condition has been studied to clarify the effects of fluorination time and low temperature. PPLP specimens were fluorinated in a reaction kettle using a F
₂
/N
₂
blend with an 80% volume fraction of nitrogen and pressure of 0.1 MPa for respectively 5, 10, and 15 min. Corona charging was performed with dc voltage at a relative humidity of ~15% in atmospheric air on room temperature specimens and after the specimens had been cooled by LN
₂
for 20 s before the corona charging. Then, the surface potential was measured with an electrostatic voltmeter. The results indicate that the accumulation and decay behaviors of the surface potential for PPLP are affected by the charge polarity, specimen temperature, and fluorination time.