The Failure Rate Of Polyethylene Insulated Cable

The failure rate of polyethylene cable in utility underground distribution systems is a matter of concern throughout the industry. A major failure mechanism is electrochemical treeing which results in insulation breakdown. Electrochemical treeing in polyethylene cable is known to be a function of voltage stress, moisture, insulation defects and time in service. This paper deals with the formulation of failure rates due to electrochemical treeing, for both high molecular weight and crosslinked polyethylene cables. It is shown, using data from several sources, that the failure rates are a function of the time that the cable is in service. Expressions are derived for determining the failure rate from field data.