a) To facilitate interchange.
b) To have momentary parallel during changeover. Protections
a) Door interlock to trip HT and LT breakers.
b) LT breaker can on only after HT breaker is in on position.
c) Instantaneous O/C and inverse O/C (50 + 51).
d) Instantaneous E/F (50N).
e) IDMT E/F and restricted E/F (51N + 64).
f) Winding temp high trip (140°C trip and 130°C alarm)
