Evaluation on flashover voltage property of snow accreted insulators for overhead transmission lines, part I - field observations and laboratory tests to evaluate snow accretion properties

This paper presents evaluation of snow accretion properties of long-rod and cap & pin insulators focusing on the phenomena found in the snowstorm in 2005, which related to wet snow accretion packed with sea-salt. Field observations at severe natural environment and laboratory tests under defined conditions were parallelly carried out in order to clarify wet snow accretion process under various conditions. In field observations, it was confirmed that snow easily accreted on insulators at temperature range especially between 0 and +1.0°C. The long-rod insulator's sheds were bridged more easily than that of cap & pin type because of its narrower shed spacing. In laboratory tests, cylindrical snow accretion, which was found in the snowstorm in 2005, was achieved. The mechanisms on explaining snow accretion on long-rod insulators were found to be similar to those confirmed for wires. The laboratory simulations agree well with the field observations. In order to estimate the amount of snow flux on insulators caused by a snow event for given climatic conditions, an index called the snow accretion potential ability (SAP) was proposed. SAP is defined by using the snow flux and associated with the weight term in the index for the snow stress product (SSP). SAP was adopted to evaluate snow accretion characteristics by field observations and laboratory tests, and the snow accretion phenomenon during a snowstorm in 2005 was discussed.