The Influence of Wear and Moisture on Flashover Properties of PEEK-FSR Interface in Underwater HV Electrical Connector

Underwater high-voltage electrical connectors (UHECs) are mainly used to connect nodes for subsea projects to ensure the stability and reliability of power transmission. Repeated connections and disconnections of UHEC result in its solid-solid interface being under extreme adverse conditions of wear and moisture intrusion. In this paper a scale model is employed to get the DC flashover properties of polyetheretherketone (PEEK) and fluorosilicone rubber (FSR) interface under different interface wear induced roughness and degrees of moisture intrusion, and the effect of interface coating with silicone grease and the coating on moisture were studied. The results show that the interface DC flashover field strength (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</sub>) decreases from 6.7 kV/mm to 3.8 kV/mm as the equivalent roughness increases from 0.53 μm to 2.95 μm. Interface flashover is predominantly governed by the size of the interface cavity, and the concentration of the electric field in the cavity leads to interface flashover. The invasion of moisture at the interface will cause a decrease in the PEEK-FSR interface <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</sub>, and when the interface micro-water content reaches 0.625 μL/cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>, the interface <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</sub> significantly decreases. When the equivalent roughness of the interface is 0.53 μm, the interface <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</sub> decreases by 11.1% until the interface is exposed to a humid environment for 20 days and coating silicone grease on the interface significantly increases the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</sub> from 6.7 kV/mm to 16.3kV/mm. And even if the silicone grease layer is severely affected by moisture, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</sub> only decreases by 18.6%, which is 49.3% higher than before coating. Coating silicone grease on the interface is an effective interface treatment method for improving the insulation performance and environmental adaptability of PEEK-FSR interface. The research results provide some useful guidance for the insulation development and design of UHEC.