Treeing

A series of tiny (less than .0254 mm/0.001-in.) hollow channels that are formed in insulation and precede insulation failure. This type of problem is of great concern for the electrical utility sector as buried power cables are subjected to conditions that over time can cause treeing. There are two types of “trees”: electrical trees, which result not from exposure to water but from high electrical stress in a short period of time and having a measurable corona discharge; and electrochemical trees, which are caused over a long period of time by exposure to water and/or cable imperfections with no measurable corona discharge.