ITU-T - K.108
Joint use of poles by telecommunication and solidly earthed power lines
|Publication Date:||1 November 2015|
This Recommendation provides technical procedures in order to protect the telecommunication lines installed in poles that are also used by solidly earthed power distribution lines, with special reference to the accidental contact between these lines (power-cross). For the protection regarding the interference produced by electric power lines on telecommunication lines, the user shall refer to [b-ITU-T K.26].
The telecommunication lines considered are those made of cables containing one or more twisted metallic pairs with and without a metallic sheath and covered by an outer plastic sheath. These cables are supported by a steel or composite strand that may be incorporated in the same cable or may be independent. In the latter case, the steel strand may be bare or insulated by a plastic outer sheath, and the telecommunication cable is attached to the steel strand usually by a lashing wire.
The power distribution lines considered are those operating in alternating currents with nominal voltages up to 25 kV (phase-to-phase). The lines may have one, two, or three phases, with and without a neutral conductor. It is considered that the power transformer at the distribution substation has its windings in the secondary side connected in Y configuration and that the neutral of the transformer (central point of the Y) is connected directly to earth (solidly earthed). Substation power transformers which are secondary side-earthed through a resistor, non-earthed, or earthed by resonant systems (e.g., Petersen coil) are out of the scope of this Recommendation.
NOTE - The distribution substation referred above is the origin of the distribution medium voltage feeders that provide power to the medium voltage / low voltage transformers.