IEC 60077-3:2019 gives the rules for circuit-breakers, the main contacts of which are connected to DC power and/or auxiliary circuits. The nominal voltage of these circuits does not exceed 3 000 V DC according to IEC 60850. This part of IEC 60077, together with IEC 60077-2, states specifically:
a) the characteristics of the circuit-breakers;
b) the service conditions with which circuit-breakers complies with reference to:
- operation and behaviour in normal service;
- operation and behaviour in the case of 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 2001. This edition includes the following main technical changes with regard to the previous edition:
- procedure of verification of temperature rise is changed;
- air-tightness test as type test, insulation resistance measurement are added.