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Use of HVI Conductors for installations with a risk of ¨ Heating of discharge paths
explosion ¨ Uncontrolled flashover if the separation distance is not
Lightning strikes to or near structures and incoming supply maintained
lines can damage the structure itself or persons and equipment
therein and can also affect and influence the immediate vicin- ¨ Induced voltages in cables and lines
ity. There is a particularly high risk when processing flamma- ¨ Lightning strikes to lines entering potentially explosive at-
ble substances such as gas, vapour, mist or dust which, when mospheres
mixed with air, can form an ignitable atmosphere and cause
an explosion in combination with an ignition source. From a If lightning protection systems are installed on or in a structure
lightning protection point of view, more detailed information for which potentially explosive atmospheres (zones) are de-
is required on this topic to ensure proper installation of protec- fined, they must meet the requirements of the relevant zones.
tion systems. The division into zones which is required for this purpose is in-
According to the German Ordinance on Industrial Safety and cluded in the explosion protection document according to the
Health (BetrSichV), the operator must create an explosion pro- German Ordinance on Industrial Safety and Health. In Ex sys-
tection document where the potential risks resulting from the tems with Ex zone 2 and 22, explosive atmospheres are only
persistence and expansion of explosive atmospheres are as- to be expected in rare and unpredictable cases. “Persistence of
sessed and defined in an Ex zone plan. The following Ex zones an ignitable explosive atmosphere” in these zones and a light-
are distinguished: ning strike rarely occur at the same time. Therefore, intercep-
Zone 0 Place in which an explosive atmosphere consisting tion of lightning strikes (lightning strikes to the air-termination
of a mixture of air and flammable substances in the system) is permitted in these zones. Nevertheless, uncontrolled
form of gas, vapour or mist is present continuously, flashover resulting from the fact that the separation distance
for long periods or frequently is not maintained and heating of the discharge paths are not
Zone 1 Place in which an explosive atmosphere consisting acceptable / allowed in all Ex zones.
of a mixture of air and flammable substances in the Electrical isolation of the lightning protection system from con-
form of gas, vapour or mist is likely to occur occa- ductive parts of the building structure and insulation with re-
sionally in normal operation spect to the electrical lines in the building prevents flashover and
Zone 2 Place in which an explosive atmosphere consisting thus dangerous sparking in potentially explosive atmospheres.
of a mixture of air and flammable substances in the The HVI Conductor allows to maintain the separation distance
form of gas, vapour or mist is not likely to occur in and prevents impermissible heating of the discharge paths.
normal operation but, if it does occur, will persist for In the high-voltage-resistant, insulated down conductor, the
a short period only lightning current is directly conducted to the earth-termination
Zone 20 Place in which an explosive atmosphere, in the form system without causing flashover. The HVI Conductor can be
of a cloud of combustible dust in air, is present con- directly installed next to metal parts of the building structure
tinuously, for long periods or frequently or electrotechnical systems (Figure 5.2.4.15).
Zone21 Place in which an explosive atmosphere, in the form
of a cloud of combustible dust in air, is likely to occur
in normal operation occasionally
Zone 22 Place in which an explosive atmosphere, in the form
of a cloud of combustible dust in air, is not likely to
occur in normal operation but, if it does occur, will
persist for a short period only

The division of the relevant structure into Ex zones allows to
identify possible ignition sources. In EN 1127-1 or the Ger-
man TRBS 2152-3, lightning is defined as ignition source in
an explosive atmosphere. If lightning strikes an explosive at-
mosphere, it is ignited. High currents flow away from the point
of strike and may generate sparks along the discharge path.
Lightning-related ignition sources are, for example:
Figure 5.2.4.15 HVI Conductor installed on a gas pressure control
¨ Melting at the point of strike and measurement system

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