This International Standard specifies characteristics for composite insulators of electric traction overhead contact line systems for railways, as defined in IEC 60913. Insulators specified in this standard are applied for electric traction supply voltages with a nominal voltage greater than 1 000 V for a.c. or a nominal voltage greater than 1 500 V for d.c.. Specific applications where high torsional loads can occur are outside the scope of this standard and particular tests are agreed between the supplier and customer to represent the critical loading arrangements. This International Standard applies to composite insulators as defined in 3.1 below and not to other polymeric insulators. The provisions contained in this standard are intended for the design and construction of new electric traction overhead contact line systems using insulators, or when complete refurbishment of existing overhead contact line systems takes place. This standard provides the purchaser and manufacturer with a range of tests which are used to evaluate the suitability of an insulator product for a given railway environment. Additional tests may be specified by the client to measure the compliance of the insulator under particular operating conditions. The standard establishes the product characteristics, the test methods and acceptance criteria. The object of this standard is to stipulate the provisions for the design and provision of the service indicated by the manufacturer to the customer or informed buyer for application on the railway infrastructure.