IEC 60077-4:2019 gives rules for AC circuit-breakers, the main contacts of which are connected to AC overhead contact lines; the nominal voltage of these circuits being in accordance with IEC 60850. This document, together with IEC 60077-2, states specifically:
a) the characteristics of the circuit-breakers;
b) the service conditions with which circuit-breakers comply with reference to:
- operation and behaviour in normal service;
- operation and behaviour in short-circuit;
- dielectric properties;
c) the tests for confirming the compliance of the components with the characteristics under the service conditions and the methods to be adopted for these tests
d). the information to be marked on, or given with the circuit-breaker.
This second edition cancels and replaces the first edition, issued in 2003. This edition includes the following main technical changes with regard to the previous edition:
a) standard values of transient recovery voltages and test procedure are reviewed;
b) procedure of verification of temperature rise is changed;
c) air-tightness test as type test, insulation resistance measurement are added