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3 Degree pollution (based VDE 0110-1 and IEC 60664-1)
The micro-environment determines how contamination affects the
insulation. rule, contamination becomes conductive when
mixed with water. protective devices, contactors, switches and outlets.
. This includes equipment
connected overhead lines, e.1.2 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.
4.
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. Domestic
electrical appliances are included this category, for example.g. with surge arrestors).
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. Equipment this overvoltage
category primarily operated low voltage.
Micro-environment: Immediate surrounding the insulation, which
especially influences the creepage distance rating.
Macro-environment:Environment room other location which the
equipment installed operated. Contamination caused water, soot, metal coal dust is
always conductive.Insert 161
4.g. However, the macro-environment should also considered.
Overvoltage category III
Includes equipment intended for the operation plants parts thereof.
Overvoltage category IV
Equipment intended for operation plants, parts thereof, where transient
overvoltage has taken into consideration. This circumstance has led the specification minimum
clearance distances.
Small clearance distances can bridged completely solid particles, dust
or water.6.g. This includes equipment for permanent
installations, e. control devices, meters.6.1
