Investigation on the Compatibility of Transformer Construction Materials with Natural Ester

With the development of high temperature insulation system, natural ester transformers grow rapidly at present. The international standard for the compatibility of transformer construction materials with natural ester are necessary by industry. ANBT NBR 16341, standards in Brazil, identified compatibility of natural ester transformers. However, thermal ageing temperature, 100°C, is too low to identified high temperature insulation system, such as aramid enhanced cellulose with natural ester. In this paper, a series of construction material used in natural ester transformers have been tested, including nitrile rubber, acrylic ester, inner surface varnish, varnish of silicon steel sheet and varnished wire. The natural ester adopted in this paper was FR3. The properties of FR3, rubber and vanished wire were tested before and after 164 hours, 336 hours thermal aging under 130°C. The experimental results indicate that the dielectric strength, dielectric dissipation factor, viscosity and acid value of natural ester, the mass and hardness of rubber are the necessary parameters for evaluating the compatibility of construction materials with natural ester. Meanwhile it is observed that the parameters benchmark of FR3 in ANBT NBR 16341 needed to be justified for overloading transformer. According to the initial test data in this paper, there is big concern for compatibility of the Nitrile rubber and varnished wire with FR3, while acrylic ester, inner surface varnish of transformer and varnish of silicon steel sheet are well compatible with FR3 natural ester. The results in this paper can provide some reference to the revision of the standard for the compatibility of transformer construction materials with natural ester.