scope:

PURPOSE AND SCOPE

The guidance in this document is for the installation of Line Isolation Units (LIU's) on copper provided telecommunications services originating from an off site telephone exchange. LIU's are required to provide electrical safety to National Grid and the telecommunications provider staff under rise of earth potential conditions at hot sites.

To ensure that all relevant safety standards are met and there is consistent installation and equipment practice between sites guidance is provided for the infrastructure requirements for an installation. The guidance does not provide detailed designs for an installation, as this will vary from site to site.

Requirements in this document are applicable to installations at new substation sites only; they apply during the whole life cycle of the substation from the start of the construction and until decommissioning. This includes site construction Portacabins if they are on site when the power system becomes live.