Fault Current Calculations :
Impedance diagram; per unit and percentage
impedance; sequence components; impedance to be considered for different network elements
like generator, transformer, transmission line, motor, cable, etc; default figures where
data not available; fault calculation procedures; step by step fault level calculation
exercise for phase fault and ground faults; input to relay co-ordination exercise.
Relay Setting & Relay Co -ordination :
Primary & back up protection; need for
co-ordination; functional characteristics of protection scheme, including sensitivity,
selectivity (discrimination by time, current and both time and current), and speed;
Discrimination time (co-ordination interval); Criteria for setting pick ups and time dial
for DMT and IDMT relays.
Tools available to reduce fault clearance time like instantaneous
over-current; Instantaneous earth fault, Pilot wire protection, and Bus bar protection;
overload vs overcurrent protection. Step by step relay setting and co-ordination exercise
for phase fault and ground fault relays, application checks with conventional and
numerical relays.
