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How do we achieve surge protection?
How do we achieve surge protection?
We have to consider surge protection from two points
of view:
• General protective measures during the planning and
construction of buildings and electrical installations.
• Special protective measures realised by the installation of
additional surge protection components.
Planning buildings and electrical installations
Some primary measures to prevent or limit surge voltage
damages can be incorporated into buildings and electrical/
electronic facilities right from the start. Although such
measures can achieve only basic protection, they can save
some of the costs involved when it comes to planning an
effective, complete protection concept. Beginning with the
rst phase of construction, it is very important to set up an
earthing or equipotential bonding facility of sufcient size.
Only this will ensure full equipotential bonding in the event
of a malfunction.
Thus when speaking of lightning protection, we only refer
to lightning protection equipotential bonding. All cables are
connected to the lightning protection equipotential bonding:
including the power supply, measurement and control
signals, telephone lines, and even the water and gas lines.
When planning the electrical installation, care must be
taken to ensure that electrical systems with dissimilar rated
voltages are kept separate. Corresponding protection zones
can then be set up and this leads to cost-savings in the
surge protection.
Furthermore, the physical separation or shielding of lines
that can inuence each other is a good way to achieve
maximum electrical isolation. Another good option is
to split up the individual phases of three-phase systems
corresponding to their functions, e.g. one phase only for the
supply to instrumentation and control systems.
Of course, all these primary measures do not achieve
complete protection. To do this, you must install additional
protective components.
Surge protection components
Surge voltages are kept away from at-risk electrical
components by rst reducing them to a harmless dimension
before they reach the components.
The quick reaction times of surge arresters are used to
provide this protection. They must respond during the
high-frequency rising phase of the overvoltage, i.e. before
a dangerous value has been reached, and quench the
overvoltage. The response time lies in the nanoseconds
range.
Naturally the surge protection components must be able
to withstand very high currents, since a surge can, under
certain circumstances, deliver several thousand amperes.
At the same time, no excessive (i.e., dangerous) residual
voltages should remain, even if the operating current is very
high. So surge protection components must exhibit a very
low resistance discharge behaviour.
In addition, it is absolutely essential that the surge protection
component is very quickly available again in electrical
terms after the surge has been quenched by earthing it.
This is necessary to ensure that the function of the circuit is
guaranteed.
Good surge protection is characterised by:
• Fast response behaviour
• High current-carrying capacity
• Low residual voltage
• Good reactivation time
Weidmüller can supply protective components that full
these criteria. Depending on the application, these usually
consist of a combination of individual components, as
described in the chapter on surge components.
Which combination of protective components is available for
the respective application is described in the chapters B, C
and D.
It will become clearer, from the set-up of the protective
elements, how and where a product is used.
The rst protection mechanism is always installed at the
building entrance, so that the initial coupling interference
can be directly “intercepted” before the sensitive end
devices.
SURGE PR
OTECTION
W
The basics of lightning and surge protection
W.8 2028840000