What are the different protection systems used to protect
the transformer internally and externally?
Answer Posted / vinod g
Transformer protection
1) protection provided in the transformer are
A) buchholz relay for both main and oltc (ansi no 63)(alarm and trip)
B) winding temperature (wti) 49(alarm and trip)
C) oil temperature (oti) 49 (alarm and trip)
D) explosion vent or prv
e) Magnetic oil level gauge for alarm
f) Fire protection (Mulsifire system)
g) Lightning Arrester provided in both HV and LV
2) High Voltage side Protection
a) differential protection 87 (operate when fault occurs between HT CT and LV CT)
b) REF restricted earth fault 64 for winding protection
c) over flux for higher rating transformer
d) directional over current towards the source side, operate when fault feeding from LV during coupled with other transformer
NOTE: Master trip 86 relay is provided as the above relays are having less current rating output contacts, can not provide sufficient current huge trip coil circuit breaker. also 86 is provided with manual reset
3) Low voltage side Protection
Instantaneous and time delay over current 50
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