DIN EN 62631-3-1:2017-01

Insulating materials are used in general to electrically isolate components of an electrical system from each other and from earth. Solid insulating material may also provide mechanical support. For these purposes it is generally desirable to have the insulation resistance as high as possible, consistent with acceptable mechanical, chemical and heat resistance properties. Volume resistance is a part of the insulating resistance. Volume resistivity can be used as an aid in the choice of an insulating material for a specific application. The change in resistivity with temperature and humidity may be great and has to be known when designing for operation conditions. When a direct voltage is applied between electrodes in contact with a specimen, the current through it decreases asymptotically towards a steady-state value. The decrease of current with time may be due to dielectric polarization and the sweep of mobile ions to the electrodes. For materials having volume resistivity less than about 10¹⁰ Ώm the steady state is generally reached within 1 min and the resistance is determined after this time of electrification. For materials with higher volume resistivity the current may continue decreasing for several minutes, hours, days or even weeks. For such materials, therefore, longer electrification times may be necessary. The measurement of volume resistance (and volume resistivity respectively) shall be carried out carefully and taking into account the electric properties of the measuring circuit as well as the specific electric properties of the material. This Part 3-1 of the IEC 62631 series of international standards describes a test method for determining the volume resistivity and volume resistivity of solid electrical insulating materials by applying a DC voltage. This general method describes common values for general measurements. If a method for a specific type of material is described in this standard, the specific method shall be used. The responsible committee is DKE/K 183 "Bewertung und Qualifizierung von elektronischen Isolierstoffen und Isoliersystemen" ("Evaluation and qualification of electrical insulating materials and systems ") of the DKE (German Commission for Electrical, Electronic and Information Technologies) at DIN and VDE.