Conductor ensures safe separation distance

High voltage insulated down conductor ensures safe separation distances in lightning protection systems.

A novel type of coaxial insulated down conductor forms the heart of the latest generation of lightning protection systems from Dehn UK.

Known as HVI, the new conductor has specifically been designed to ensure the safe separation distance called for in new British and European standards for lightning and surge protection.

The new system is ideally suited to use for protecting buildings carrying mobile phone antennas or roof-mounted structures such as heating and ventilating systems.

The separation distance is a significant parameter in the planning and installation of lightning protection systems.

Maintaining the separation distance, which is determined by calculations specified in BS EN62305, is essential to prevent dangerous flashovers between external lightning protection systems and internal conductive elements such as electrical wiring, conduits and equipment.

The HVI down conductor is based on a new type of coaxial single-conductor cable which provides control of the electric field by incorporating a semi-conductive external shield whose electrical conductivity ensures that the lightning current is guided into the cable and conducted safely while maintaining the separation distance.

The semi-conductive shield of the coaxial single-conductor cable insulates the electrical field without affecting the magnetic field surrounding the current-carrying inner conductor.

As a result, the HVI down conductor prevents the occurrence of creepage discharges and allows lightning currents to be conducted safely to earth.

The optimisation of the field control provided by the semiconductive sheath of the HVI conductor is further enhanced by the development of a specially adapted cable sealing end with a length of 1.5m, allowing the realisation of an equivalent separation distance of 0.7m in air or 1.5m in solid construction materials.

This cable sealing end allows connection to the feed point of the air-termination system and to the building's equipotential bonding system, with the two connections separated by a predefined distance.

When compared with a coaxial cable with a metal shield, the complete semi-conductive cable sheath has a much higher resistance.

As a result, no noticeable partial lightning currents can be displaced into the building, even if the cable sheath is connected to the equipotential bonding system in several places.

The HVI conductor can be installed along the facade or integrated into the facade of a building, opening up a number of design possibilities for the building designer or architect without compromising the need for the required separation distance.

Functionality and design can sit side by side, making this innovative technology an important aspect of modern architecture.

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