IEC TR 62039 pdf free download

IEC TR 62039 pdf free download.Selection guidelines for polymeric materials for outdoor use under HV stress.
4.5 Tear strength
The standard for testing the tear strength of elastomeric housing materials is ISO 34-1 (method B, procedure (a) — without nick).
The minimum requirements are given in Table 1.
4.6 Volume resistivity
Volume resistivity measurements can show the presence of conductive contaminants in insulation materials. This property can have some importance in the assessment of additives that are often used (e.g. fillers containing different levels of ionic impurities). The volume resistivity parameter is also sensitive to incorrect curing processes of some resin systems.
The test method is in accordance with IEC 62631-3-1. The test method is applicable to core, housing and structural materials.
The minimum requirements are given in Table 1.
NOTE The applicability for coating materials is also under consideration by CIGRE.
4.7 Breakdown field strength
The electrical breakdown strength is an important property of insulation materials and should be verified for housing and structural materials. The breakdown strength of the core material does not need to be measured separately because it is evaluated during the test that measures the resistance to chemical and physical degradation by water (see 3.4).
Sheet test samples are given in IEC 60243-1 for alternating current and IEC 60243-2 for direct current.
Insulating materials usually have high intrinsic electrical strength. In order to evaluate that, a different test arrangement is necessary. Such an arrangement is presented in IEC 60455-2 for rigid insulation materials (e.g. epoxy resin) and flexible insulation materials (e.g. silicone rubber). The different test arrangements in IEC 60243-1, lEG 60243-2 and IEC 60455-2 result in different levels of the breakdown strength.
The minimum requirements are given in Table 1.
NOTE The applicability for coating materials is also under consideration by CIGRE.
4.8 Stress corrosion test (resistance to chemical attack)
4.8.1 General
Core materials can be susceptible to acid attack that can be associated with water penetration. When significant tensile mechanical loads are applied to the core simultaneously, stress corrosion can occur. As a result, brittle fracture can occur.
If a core material is to be evaluated regarding its acid resistance, for example a core material used for outdoor insulators that are predominantly subjected to tensile stress, an acid resistance test can apply.
The test is performed under ambient temperature to confirm the mechanical resistance of the core material to stress corrosion.
4.8.2 Test specimens
Three specimens prepared in accordance with the normal production process are selected. The specimens have a length of insulation between end fittings of at least 10 times the core diameter, and not less than 800 mm. Suitable end fittings are used. To avoid any latent damage to the core by the difficult removal of the housing it is permissible to prepare bare rod samples for this test.
4.8.3 Procedure
The visible core surface should be smoothed by means of a fine abrasive cloth (grain size 180). A non-transparent acid container should be placed to surround the visible core surface and be sealed at the base to prevent any leaking acid. The size of the acid container should ensure that the core material is surrounded by the liquid radius of not less than 1 cm and along a length of not less than 4 cm. Following the filling of the container with the acid, it should be covered and/or sealed to prevent evaporation of the acid by more than 5 % of its volume during the test period.
The specimen is subjected to a tensile load applied between the metal fittings. The tensile load is increased rapidly but smoothly from zero to the full load. The full load for unidirectional glass fibre composites should be 340 MPa (for other materials different mechanical loads can be used) and maintained for 96 h. Immediately after applying the load, nitric acid of a concentration of 1 N (N = normal) is poured into the acid container (1 N = 63 g HNO3 plus 937 g H20). Both horizontal and vertical set-up positions of the specimen are acceptable.IEC TR 62039 pdf download.