Protection Level refers to physical shielding from debris, environmental contaminants, and mechanical damage. How Do You Choose the Right. association representing the major electrical equipment manufac-turers in the U. The Cable Tray ng standards, performance standards, test standards and application in this document have been tested extens ompetent professional en completely installed, without damage either to conductors or. cable trays are equivalent. Our focus has always been on solutions from the field of cable support systems. Unlike conduit systems, cable trays allow cables to be laid in bundles, improving accessibility, heat.