Track resistant coatings

Summary form only given. Surface carbon tracking of insulating members in electrical equipment is a problem which is receiving increased attention from both suppliers and users of electrical components. The principle emphasis towards the solution of this problem has been placed on the development of track resistant insulating materials which are capable of being formed by various techniques into solid track resistant insulating members. Considerable progress has been made along these lines, particularly in the field of polyester-glass laminates and polyester premix type materials. Some progress has been made in the development of track resistant materials utilizing resins other than polyester. There is, however, another facet to the problem of developing track resistant insulating members which has received relatively little attention to date. This approach involves the development of a track resistant coating material which can be applied to the surface of relatively poor track resistant insulators to protect these parts from carbon tracking. Track resistant coatings offer some advantages from both economic and utility standpoints. Cost savings may be realized by using less expensive substrate materials which may have relatively poor track resistance and protecting these materials from carbon tracking with a coating of a track resistant material. A track resistant coating can also permit rehabilitation of existing insulation which in many cases would have had to have been replaced. Track resistant coatings must also have those other desirable properties usually associated with all good coating materials including good adhesion, high resistance to impact, abrasion and indentation. Such properties as good resistance to chemical and solvent attack and good electrical properties are also required for coatings in this application. This paper presents some of the materials which have been prepared and the methods used to evaluate these materials. Specific data are presented on the best track resistant coating developed to date. Details on six arc and track resistance test methods are presented. These tests include the Dust and Fog Test, the High Power Arc Test, the Circular Tracking Test, the Linear Tracking Test, the Alabama Power Test, and ASTM Method Dß+95.