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Contamination caused water, soot, metal coal dust is
always conductive. However, the macro-environment should also considered.2 Overvoltage categories
Equipment divided into one the following excess voltage categories:
Overvoltage category I
Equipment intended for use devices parts plants where overvoltages
cannot occur, which are protected with suitable measures against such
overvoltages (e. protective devices, contactors, switches and outlets.
Overvoltage category IV
Equipment intended for operation plants, parts thereof, where transient
overvoltage has taken into consideration.
Here, transient overvoltages not have taken into consideration,but
because special demands placed this equipment with regard the
safety and availability and the networks that depend it, overvoltage
remains factor for consideration.
Micro-environment: Immediate surrounding the insulation, which
especially influences the creepage distance rating. Domestic
electrical appliances are included this category, for example. This includes equipment for permanent
installations, e. Equipment this overvoltage
category primarily operated low voltage.
. This includes equipment
connected overhead lines, e.Insert 161
4. This circumstance has led the specification minimum
clearance distances.
Overvoltage category II
Equipment intended for operation plants, parts thereof, where transient
overvoltages not have taken into consideration; but where
overvoltages caused operation equipment may occur.
Small clearance distances can bridged completely solid particles, dust
or water. rule, contamination becomes conductive when
mixed with water.1.
4.1.g.3 Degree pollution (based VDE 0110-1 and IEC 60664-1)
The micro-environment determines how contamination affects the
insulation. with surge arrestors).
Macro-environment:Environment room other location which the
equipment installed operated.
Overvoltage category III
Includes equipment intended for the operation plants parts thereof.6.g. control devices, meters.g.6
