TOS8870A
Overvoltage category VII
Overvoltage category
For the safe use of equipment, IEC60664 (Insulation coordination for equipment
within low-voltage systems) classifies circuits into four categories by an occurrence
level of transient voltage. When you connect equipment to a power line or connect a
measuring instrument to these places, make sure of the applied overvoltage cate-
gory. This instrument is designed to operate from the overvoltage category II.
Overvoltage category I
Equipment of overvoltage category I is equipment for connection to circuits in
which measures are taken to limit transient overvoltages to an appropriately low
level.
Examples are protected electronic circuits.
Overvoltage category II
Equipment of overvoltage category II is energy-consuming equipment to be sup-
plied from the fixed installation.
Examples of such equipment are appliances, portable tools and other household and
similar loads.
If such equipment is subjected to special requirements with regard to reliability and
availability, overvoltage category III applies.
Overvoltage category III
Equipment of overvoltage category III is equipment in fixed installations and for
cases where the reliability and the availability of the equipment is subject to special
requirements.
Examples of such equipment are switches in the fixed installation and equipment for
industrial use with permanent connection to the fixed installation.
Overvoltage category IV
Equipment of overvoltage IV is for use at the origin of the installation.
Example of such equipment are electricity meters and primary overcurrent protec-
tion equipment.
Switchboard
Overvoltage category
IV
Overvoltage category
III
Overvoltage category
II
Overvoltage category
I
Transformer
Equipment
Drop wire
Indoor wiring
AC line
Receptacle
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