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Dimensioning of clearances and creepage
distances according to DIN EN 60664-1/
VDE 0110-1.
This part of the standard, based on IEC
60664, contains specifications for the
insulation coordination of equipment in
low-voltage systems. This part is applicable
for equipment to be used at an altitude of
up to 2000 m above sea level. This basic
safety standard is primarily aimed at
technical committees, and if suitable
product directives are not available for
equipment, it can be applied at the user's
own responsibility. International and
European product standards cited in this
catalog contain specifications for insulation
coordination according to
DIN EN 60664/VDE 0110-1.
Insulation coordination
Insulation coordination includes the
selection of electrical insulation properties
for equipment as regards intended
applications and ambient conditions.
Separate requirements must be applied for
clearances and creepage distances and for
rigid insulation. The surge voltages to be
expected, characteristics of surge
protective devices, and pollution at the
intended site must be considered when
dimensioning clearances. Clearances are
then dimensioned according to the external
or internal surge voltages to be expected.
Different surge voltages, grouped into
categories, i.e., a value that specifies a rated
impulse voltage, determine the required
clearance directly. These surge voltage
categories (I to IV) are mainly based on a
statistical study, and are used for equipment
that is directly supplied by low-voltage
networks. Definitions of the individual
categories are provided below as an extract
of DIN EN 60664/VDE 0110-1.
The clearances can be calculated
according to Table 2 (minimum clearances)
depending on the homogeneity level of the
field between the electrodes (case A – non-
homogeneous field, case B – homogeneous
field).
Clearances according to case A are
capable of withstanding the assigned
impulse voltages under all conditions.
Equipment that is dimensioned according to
case A can therefore be used without any
further testing. Clearance values according
to case B are based on ideal conditions.
Clearance values which fall between case A
and case B must be proven by means of an
impulse voltage test.
The voltages present, the properties of
insulation materials, the pollution to be
expected, and safety measures against
pollution are considered when
dimensioning creepage distances.
The effect of pollution is considered
when determining the clearances and
creepage distances according to three
intensity levels (pollution degree 1 to 3).
The creepage distance is based on the
rated voltage that is derived from the
working voltage or nominal mains voltage.
The minimum creepage distances are
assigned to the rated voltages according to
the pollution degree in Table 4.
If the respective product descriptions do
not contain any additional specifications,
the products presented in this catalog are
dimensioned for surge voltage category III
and pollution degree 3 according to this
regulation (DIN EN 60664-1/VDE 0110-1).
Surge voltage categories I to IV
– Equipment in surge voltage category
IV can be used at the terminal point of
the installation.
Note: examples of such equipment
include electricity meters and primary
devices for overcurrent protection.
– Equipment in surge voltage category
III can be used in fixed installations and is
intended for such cases where there are
special requirements for the reliability
and availability of the equipment.
Note: examples of such equipment
include switches in fixed installations and
equipment for industrial use with
permanent connection to the fixed
installation.
– Equipment in surge voltage category
II is power-consuming equipment that is
supplied by the fixed installation.
Note: examples of such equipment
include household appliances, portable
tools, other domestic appliances, and
similar devices.
– Equipment in surge voltage category
I can be connected to circuits where
measures have been taken to limit the
surge voltages to a suitable lower value.
Pollution degrees 1 to 4
The following four pollution degrees
have been defined for the micro-
environment in order to determine
clearances and creepage distances:
– Pollution degree 1
No pollution or only dry, non-
conductive pollution occurs. The pollution
has no effect.
– Pollution degree 2
Only non-conductive pollution occurs.
However, temporary conductivity due to
condensation must occasionally be taken
into consideration.
– Pollution degree 3
Conductive pollution occurs or dry,
non-conductive pollution which becomes
conductive, since condensation is to be
expected.
– Pollution degree 4
Permanent conductivity occurs, caused
by conductive dust, rain or moisture.
Insulation material
DIN EN 60664/VDE 0110-1 classifies
insulation materials into four groups
depending on their CTI values that were
obtained using solution A as per IEC 60112.
These are:
Insulation material group I: 600  CTI
Insulation material group II: 400  CTI
 600
Insulation material group IIIa: 175  CTI  400
Insulation material group IIIb: 100
 CTI  175
The comparative tracking index of the
creepage distance formation must have
been determined based on suitable samples
using test solution A as specified in
DIN IEC 60112.
The proof tracking index of the creepage
distance formation (PTI) is used as proof of
the creepage current properties of
insulation materials.
Insulation coordination for electrical equipment within
low-voltage systems
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