IEC 60255-5 defines the insulation coordination requirements for measuring relays and protection equipment and the tests by which compliance is demonstrated. It establishes the relationship between the rated insulation voltage or rated impulse voltage of a circuit and the minimum clearances, creepage distances and solid insulation thickness that the design must provide, taking account of the overvoltage category of the installation, the pollution degree of the environment and the comparative tracking index of the insulating material. Dielectric tests at power frequency and impulse tests with the standard 1.2/50 microsecond waveform are specified for each circuit classified by its function, so that auxiliary supply circuits, input circuits and output contact circuits are verified separately and against each other. The standard also describes the preparation of the test specimen, the conditioning before test and the criteria by which a breakdown is judged to have occurred. It is applied by relay manufacturers during type testing and by testing laboratories that verify protection equipment for utility and industrial customers.