scope:

Telephone lines are constantly being repurposed for digital use. This Supplement looks at the lightning threats that repurposing digital G.fast (fast access to subscriber terminals) may bring.

Since the publication of [ITU-T K.118], Requirements for lightning protection of fibre to the distribution point equipment, the system, often called G.fast (fast access to subscriber terminals) with reverse power feed (RPF), has had extensive deployment. This Supplement provides the subsequent informative references and materials that have appeared since the publication of [ITU-T K.118].

The conventional telephone twisted pair connecting wire, termed the link (transmission path between two cabling system interfaces, including the connections at each end), between the distribution point unit (DPU) and the customer premises equipment (CPE) usually has a maximum length of up to 300 m.

Electrical lightning stresses on the connected equipment at the link ends are considered to arise from the lightning disturbances on the CPE powering source, differential earth potential rise (EPR) of the link ends and possibly magnetic induction to the link cable. This Supplement mainly concerns itself with the differential EPR values between the link ends.