Transformer Protection Flashcards
Features of HRC fuse
Used in MV TR
Oil and Gas
Load current flows through it
Fault clearing mechanism of HRC fuse
Fault current blows the fuse releasing the striker pin which hits the fuse switch tripping mechanism
Components of Transformer protection (TLF)
CT on each phase
2 OC coiks
1 EF coil
TLF parallel w/ O/C coils
Fault process in TLF transformer
In O/C:
Fuses will blow, fault pass through O/C coil
In E/F:
Ln will not be 0, fault current pass through E/F coil
About Restricted Earth Fault
Transformer internal fault protection
Differential relay
CTs connected to all phases and neutral of TR
About Stand By E/F
TR instantaneous protection
CT connected to TR neutral
Current over a set threshold will trip it
About Pressure Relief Valve
Protection against overpressure caused by internal fault
About Buchholz Relay
Gas relay
Connected b/w main tank and conservator of TR
Has two limit switches that move based on amount of air in oik
Types and limits of TR temperature relays
Oil temperature: triggers at 85C, trips at 90C
Winding temperature: triggers at 100C, trips at 110C (cooling system triggers at 65C)
About TR differential relay
HV TR relay, detects internal fault on both sides of TR
