Plug-In Arresters For Surge Protection Of Underground Distribution Transformers

Protection of underground systems has been difficult for various reasons. Riser pole arresters afford a too low margin of protection to prevent excess insulation stress by surge doubling at the system open point, and also too low to allow for reduced equipment BIL due to aging. Arresters could not formerly be economically installed at the end point of a distribution loop or radial feed. Various protective schemes are evaluated using the results of recent studies and considering recent product developments. Recommendations are made for future system protection.