In-service safety inspection and testing of electrical equipment
In-service safety inspection and testing of electrical equipment
In-service safety inspection and testing of electrical equipment
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APPENDIX CINSULATION RESISTANCE TESTING OF PORTABLE ISOLATING TRANSFORMERS(Normative)C1 GENERAL<strong>In</strong>sulation resistance shall be measured on portable <strong>safety</strong> isolating transformers to 2.3.3.3.C2 INSTRUMENTATIONEither an insulation resistance meter or a PAT is required with the following characteristics:(a)(b)(a)A measuring circuit isolated from earth;Nominal measuring voltage 500 V d.c;Accuracy Class 5 or better.NOTE —(1) Class 5 denotes an accuracy <strong>of</strong> 5 %, full scale deflection.(2) For guidance on the requirements <strong>of</strong> insulation measuring <strong>equipment</strong> refer to AS/NZS 3000.That is, maintain terminal voltage within + 20% <strong>and</strong> – 10% when measuring a resistance <strong>of</strong> 1M.C3 TEST CONDITIONS<strong>In</strong>sulation resistance shall be not less than 1 M <strong>and</strong> shall be measured between:(a)Live supply conductors <strong>and</strong> accessible earthed parts <strong>of</strong> a Class I transformer or enclosingcase;NOTE — A method is shown in Figure C1.(b)(c)(d)Live supply conductors <strong>and</strong> accessible unearthed metal parts <strong>of</strong> Class II transformers orenclosing case;NOTE — A method is shown in Figure C1.Live supply conductors <strong>and</strong> the connections from the transformer output (secondary) winding;NOTE — A method is shown in Figure C2.The connections from the transformer output (secondary) winding <strong>and</strong> accessible earthedparts.NOTE — A method is shown in Figure C3.Page 24
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