Guidelines for Cables between Buildings

Guidelines for Cables between Buildings

Problems that can arise with outside cables If signal cables are laid outside of buildings the following points should be noted:  A potential difference can exist between buildings that can created an error during transfer.  Cables between buildings can carry a higher current in the event of a sudden increase in the potential of a building due to a lightning strike.

Guidelines for outside cables For cables that are laid outside of buildings, the following guidelines should be observed:  Shielded cables must be used.  The shield must be capable of carrying the current and must be grounded at both ends. If the shield cannot carry the current, a relieving line can be installed directly next to the signal cable for current dissipation. The relieving line should have a cross-section of approximately 35 mm2 .  Analog signal lines must have double shielded cables, the inside shield must be grounded at one end and the outside shield at both ends.  Signal lines must be wired with an over-voltage protection element, that is connected at the cable entrance to the building when possible or at the cabinet as a minimum. Observe the following: Guidelines for Grounding and Earthing for Systems between Buildings, page111 .

Recommended for data transfer between buildings Fiber optic cables are recommended for data transfer between buildings. This creates no problems with loops between exposed conductive parts in the event of a lightning strike.