Testing insulation resistance (regulation 612.3)
In most electrical installations, insulation of live parts is used as a method of basic protection and in some protective measures insulation is also used as a method of fault protection too. During initial verification, the main aim of the insulation resistance test is to confirm that the insulation has not been damaged during installation and that incorrect termination has not caused live parts to become connected to exposed or extraneous conductive parts by mistake. In the case of periodic inspection and testing, fault finding or maybe additions and alterations, it may be appropriate to test each circuit individually. Essentially there are two quite things that one needs to consider before an insulation resistance test can be carried out. These are 'precautions' and 'preconditions'. The chapter describes factors affecting the resistance of insulation. These factors are cable length and the number of cables connected in parallel.