EARTHING GUIDE FOR SURGE PROTECTION

EARTHING FOR SURGE PROTECTION OF ELECTRONIC EQUIPMENT

Practical aspects of surge protection earthing summary.This section briefly summarises what needs to be done to earth surge protection devices effectively while the rest of the publication explains why.

Structural protection
Make sure the building housing the equipment is
provided with structural lightning protection in
accordance with national standards (in the UK, these
are established by BS6651).

Cable routeing
If possible, bring all services (i.e. electricity, telephone,
LAN cables, antenna cables, metallic water and gas
pipes) into the building at one point.

Bonding and earthing
Bond the following services to an earth terminal at one
point (preferably the main distribution board for the
mains electrical supply where applicable) using as short
a bond cable length as possible, to keep them as close as
possible to the same potential:
Metallic water and gas pipes
Antenna cable

Bond this earth terminal to the building structural
lightning protection as close to the ground as possible.

Surge protection
Fit, as close to the earth terminal as possible, appropriate
surge protection devices (SPDs) on ALL incoming cables,
where applicable, for the following services:
Electricity
Telephone
Local Area Network
Antenna
Video (security) camera
Bond the SPDs to the earth terminal with the shortest
possible length of cable with a minimum cross section of
2.5mm2. Better still, use several cables, spaced apart and
connected electrically in parallel.

Best of all, use sheet metalwork rather than cables.
If you own the entire cable link, fit another SPD at the
remote end.

Diverse cables which cannot be rerouted
Fit appropriate SPDs close to the most strategically
important equipment (e.g. fax machines, modems, etc.)
Bond the SPDs to the equipment earth (e.g. chassis or mains
protective earth) with the shortest possible length of cable
with a minimum cross section of 2.5mm2. Better still, use
several cables, spaced apart and connected electrically in
parallel. Best of all, use sheet metalwork rather than cables.