IEC 60112-2003 pdf – Method for the determination of the proof and the comparative tracking indices of solid insulating materials

IEC 60112-2003 pdf – Method for the determination of the proof and the comparative tracking indices of solid insulating materials.
1 Scope This International standard specifies the method of test for the determination of the proof and comparative tracking indices of solid insulating materials on pieces taken from parts of equipment and on plaques of material using alternating voltages. The standard provides for the determination of erosion when required. NOTE 1 The proof tracking index is used as an acceptance criterion as well as a means for the quality control of materials and fabricated parts. The comparative tracking index is mainly used for the basic characterization and comparison of the properties of materials. Test results cannot be used directly for the evaluation of safe creepage distances when designing electrical apparatus. NOTE 2 This test discriminates between materials with relatively poor resistance to tracking, and those with moderate or good resistance, for use in equipment which can be used under moist conditions. More severe tests, of longer duration are required for the assessment of performance of materials for outdoor use, utilizing higher voltages and larger test specimens (see the inclined plane test of IEC 60587). Other test methods such as the inclined method may rank materials in a different order from the drop test given in this standard. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 60589:1 977, Methods of test for the determination of ionic impurities in electrical insulating materials by extraction with liquids IEC Guide 1 04:1 997, The preparation of safety publications and the use of basic safety publications and group safety publications ISO 293:1 986, Plastics – Compression moulding test specimens of thermoplastic materials
4 Principle The upper surface of the test specimen is supported in an approximately horizontal plane and subjected to an electrical stress via two electrodes. The surface between the electrodes is subjected to a succession of drops of electrolyte either until the over-current device operates, or until a persistent flame occurs, or until the test period has elapsed. The individual tests are of short duration (less than 1 h) with up to 50 or 1 00 drops of about 20 mg of electrolyte falling at 30 s intervals between platinum electrodes, 4 mm apart on the test specimen surface. An a.c. voltage between 1 00 V and 600 V is applied to the electrodes during the test. During the test, specimens may also erode or soften, thereby allowing the electrodes to penetrate them. The formation of a hole through the test specimen during a test is to be reported together with the hole depth (test specimen thickness). Retests may be made using thicker test specimens, up to a maximum of 1 0 mm. NOTE The number of drops needed to cause failure by tracking usually increases with decreasing applied voltage and, below a critical value, tracking ceases to occur. 5 Test specimen Any approximately flat surface may be used, provided that the area is sufficient to ensure that during the test no liquid flows over the edges of the test specimen. NOTE 1 Flat surfaces of not less than 20 mm × 20 mm are recommended to reduce the probability of electrolyte loss over the specimen edge although smaller sizes may be used, subject to no electrolyte loss, e.g. ISO 31 67, 1 5 mm × 1 5 mm multi-purpose test specimens. NOTE 2 It is preferable to use separate test specimens for each test. If several tests are to be made on the same test piece, care should be taken to ensure that the testing points are sufficiently far from each other so that splashes or fumes from the testing point will not contaminate the other areas to be tested. The thickness of the test specimen shall be 3 mm or more.