Insulation resistance

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In­su­la­tion re­sis­tance is the des­ig­na­tion for the elec­tri­cal re­sis­tance of lines, ca­bles and elec­tri­cal sys­tems mea­sured in ohms. The in­su­la­tion re­sis­tance is rel­e­vant for the pro­tec­tion of per­sons against elec­tric shock and the ex­clu­sion of ma­te­r­i­al and prop­er­ty dam­age due to flow­ing leak­age currents.

The qual­i­ty of an in­su­la­tion is test­ed by mea­sur­ing the in­su­la­tion re­sis­tance. The lim­it val­ues for the in­su­la­tion re­sis­tance and the con­di­tions for its mea­sure­ment are laid down in the sec­tions of DIN VDE 0100ff, DIN VDE 0701–0702:2008 and DIN EN 60204, among others. 

What is understood by the insulation of cables, etc.?

In gen­er­al, in­su­lat­ing ma­te­ri­als are ma­te­ri­als that are in­tend­ed to pre­vent or min­i­mize fun­da­men­tal trans­mis­sion. Ex­am­ples of in­su­lat­ing ma­te­ri­als are in­su­la­tion ma­te­r­i­al to min­i­mize the es­cape of heat from a build­ing, sound in­su­la­tion to pre­vent noise pol­lu­tion or wa­ter­proof­ing to pre­vent the cel­lar vault from fill­ing up with wa­ter. In­su­la­tion ma­te­ri­als can al­so be used to pre­vent the trans­mis­sion of elec­tri­cal cur­rent. The de­mand for these in­su­lat­ing ma­te­ri­als is very high, be­cause un­in­ten­tion­al­ly flow­ing elec­tric­i­ty is a dan­ger to life and limb. In­su­lat­ing ma­te­ri­als for elec­tric cur­rent must have the fol­low­ing properties:

  • low ab­sorben­cy (so that no air humidity/water is absorbed)
  • high elec­tri­cal break­down strength
  • high elec­tri­cal resistance
  • high track­ing resistance
  • ther­mal resilience

Due to these prop­er­ties, they are con­sid­ered “non-con­duc­tors”.

Which insulating materials are used for electric current?

  • var­i­ous plas­tics (pri­ma­ry)
  • tech­ni­cal ceramics
  • spe­cial papers
  • glass

What is electric shock?

If an elec­tric cur­rent en­ters a per­son­’s body, re­sult­ing in in­jury or im­pair­ment, the term elec­tric shock is used. Oth­er terms for such a sit­u­a­tion is al­so an elec­tric or elec­tri­cal ac­ci­dent. Some­thing like this can oc­cur, for ex­am­ple, due to faulty insulation.

Flowing leakage current

Leak­age cur­rent is elec­tric cur­rent flow­ing in an un­de­sir­able cur­rent path un­der nor­mal op­er­at­ing con­di­tions (In­ter­na­tion­al Elec­trotech­ni­cal Dic­tio­nary — IEV 195–05-15). This cur­rent should not be con­fused with fault cur­rent caused by in­su­la­tion faults or equip­ment fail­ures. The most com­mon cause is due to fil­ter ca­pac­i­tors in con­nec­tion with the pro­tec­tive conductor.

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