Standards Development

Scope

The aim of the test is to evaluate the retention of hydrophobicity with the Dynamic Drop Test of solid polymeric insulating materials under accelerated and calibrated test conditions so that different insulating materials can be compared with respect to th is property. The time to loss of hydrophobicity is chosen as evaluation criterion.

Purpose

Hydrophobicity of polymeric insulating materials is a surface property by repelling water and aqueous electrolyte solutions. This hydrophobic behaviour suppresses critical leakage currents that may occur when an electrolytic pollution layer is stressed by high voltage as given e.g. for polymeric insulators in outdoor application. With an efficient leakage current suppression, pollution -initiated flashovers and deterioration of insulating materials like tracking or digging erosion can be avoided. The hydrophobicity of hydrophobic polymeric insulating materials is a dynamic property and may be reduced by certain stresses (retention of hydrophobicity), recovered and transferred onto polluted surfaces.

This standard describes a test procedure for polymeric insulating materials to evaluate their retention of hydrophobicity against water drop corona with the so -called Dynamic Drop Test.

The retention of hydrophobicity evaluated in the Dynamic Drop Test depends significantly on the insulating material (type and specific composition of the polymer), the surface structure (e.g. topography and roughness), the electrical stress and the type of pollution. The CIGRE WG D1.58 evaluated and improved the test procedure and setup for AC and also investigated preliminary for DC. In the first addition the test under AC is described, however in the future with the ongoing work in CIGRE also the test under DC will be considered if it is necessary