Electricity + Control October 2016

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EARTHING + LIGHTNING PROTECTION
• Type 2 (Class II) – Medium protection. These devices are used
for protection against Other Surges i.e. switching transients.
Normally situated in the secondary DBs supplied from a main DB
which would consist Type 1 devices. Should there be only one DB
servicing a facility with no secondary DBs, a combination Type 1
and 2 device should be installed in the DB
• Type 3 (Class III) – Fine protection. These devices are used for
protection against Low Energy Surges which can damage sensi-
tive equipment. These devices are normally situated as close as
possible to the equipment to be protected. Type 3 devices may be
used in all areas of electrical / electronic applications including:
• Mains power supply ac and dc
• MCR (Measurement, Control and Regulation)
• Information technology and Telecommunications
• Transceiver systems.
Type 3 devices should also be used in conjunction with Type 2 devices.
When do we use protection devices?
Around the world all electrical and electronic equipment will be
exposed to some form of damaging transient activity. The
cost of protection is almost always less than the cost
caused by the consequences of surges.
It is therefore obvious that the use of SPDs (Surge
Protection Devices) is an imperative and should
always be considered in any facility.
What else?
It is also important to note that an effective structural
earth system is not an option and must be part of a com-
plete Lightning and Surge protection solution.
• Most protection devices rely on an effective earth system to divert
excess energy away from protected equipment
• No earth systemmeans no protection. A poor earth systemmeans
poor or no protection
• Beware of potential differences. A potential difference in an earth
system is when you have two or more separate earth points con-
nected to the same electrical system. At the time of a lightning
strike the voltage rise in the earth will differ at each earth point
depending on their location in relation to the point of the lightning
strike, thereby creating potential differences in voltage between
earth points. This will cause voltage to find any path from the
highest voltage earth point to equalise the other earth points via
any cable it finds e.g. data lines, communication lines etc. To stop
this phenomenon, make sure that all earth points are bonded
together and in turn bonded back to the mains earth
• There are reputable companies in South Africa that specialise in
the checking and installation of earth systems
Important to know!
Lightning and surge protection cannot be used for protection against
extended over or under voltage conditions. These devices are used
to protect against short duration interferences in the pico to micro
second range which may be induced into and / or carried by electri-
cal circuits.
Conclusion
Much time and money has been spent to understand the dynamics
of lightning and switching transients. With this in mind, repu-
table manufacturers of lightning and surge protection de-
vices are effectively able to protect equipment against
damaging transients when the correct installation
and earth procedures are adhered to.
Use a reputable manufacturer or supplier of
lightning and surge protection to advise on what
type of products should be used for required ap-
plications.
Tony Rayner joined Phoenix Contact South Africa in 2006 as the
national product manager for surge and lightning protection
products. He continues to support the industry with seminars,
technical support and training.
Enquiries: Email
take note
• Lightning is a natural phenomenon…occurring around
the world.
• Surges are manmade, mostly generated by electrical
switching operations.
• A reputable manufacturer should be consulted for advice
on lightning and surge protection.
OPINION
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