Modular Housings - Kube Engineering

Electrical IsolationIsolation AmplifiersTransmittersIndicatorsProcess AnalyticsPortable MetersLaboratory MetersSensorsFittingsOvervoltage CategoriesOvervoltage Category INo occurance of overvoltageor protection by surge arrestersor filters.Overvoltage Category IISystems with switching processes,but without lightning strikes,for example, in private households.Overvoltage Category IIISystems without lightning strikes,connection of the device nearerto the power supply connectionthan the loads and/or specialrequirements for safety andavailability of the device.Overvoltage Category IVPlants with lightening strikes.5.2 Test VoltageThe dielectric strength of theinsulation material used for theisolating components is manytimes greater than the workingvoltage permitted for the device.Therefore the test voltage withwhich each device is tested isspecified additionally for isolatingdevices. This ensures that thespecified limit values for theworking voltage apply to eachdevice.The test voltage is also used occasionallyas a parameter for thedielectric strength instead of theworking voltage. This then needsto be a certain factor higher thanthe maximum possible potentialdifference between the circuits tobe isolated according to the directivefor the specific application.The test voltage for Knick isolationamplifiers is up to 15 kV AC.5.3 Safe IsolationThe term “Safe Isolation“ isdefined in EN 61140. This basicsafety standard describes protectivemeasures against electricshocks and thus defines therequirements to be met by electricalisolation between electriccircuits. “Safe Isolation“ refers toan isolation system which is characterizedby basic protection andadditional precautions (additionalinsulation or protective shielding)or by equivalent insulation (reinforcedinsulation according toEN 61010-1). It has the aim toprotect persons against electricshock. This particularly high levelof safety must be ensured byconstructive measures such asappropriate clearance and creepagedistances as well as by theinsulation properties of the internalisolating components. Thatmeans that the requirements ofthe basic safety standard have adirect effect on the isolatordesign.25