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Contamination caused water, soot, metal coal dust is
always conductive.
4. protective devices, contactors, switches and outlets.6. Domestic
electrical appliances are included this category, for example. This circumstance has led the specification minimum
clearance distances.
Overvoltage category III
Includes equipment intended for the operation plants parts thereof.6.Insert 161
4. This includes equipment for permanent
installations, e.g. However, the macro-environment should also considered.g. Equipment this overvoltage
category primarily operated low voltage.
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.
Small clearance distances can bridged completely solid particles, dust
or water.
Macro-environment:Environment room other location which the
equipment installed operated. rule, contamination becomes conductive when
mixed with water.
.g.
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.
Micro-environment: Immediate surrounding the insulation, which
especially influences the creepage distance rating.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. control devices, meters.1.
Overvoltage category IV
Equipment intended for operation plants, parts thereof, where transient
overvoltage has taken into consideration.1.3 Degree pollution (based VDE 0110-1 and IEC 60664-1)
The micro-environment determines how contamination affects the
insulation. This includes equipment
connected overhead lines, e. with surge arrestors)
