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