Answer / manoj kumar sankaralingam

i)Differential protection
ii)Restricted earth fault protection
iii)Buchholz relay
iv)Oil temperature indicator
v)Winding temperature indicator

Answer / karthikeyan

Bucholz relay
under voltage relay
over current relay
inverse time current over relay
pressure relay

Answer / viren89desai@yahoo.co.in

https://library.e.abb.com/public/4381d7d675f760cdc12575550081d599/AG03-5005E_en_Power_transformer_protection.pdf

Answer / 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

Answer / avinash

Over current and earth fault Protection relay
Differential Protection relay
Restricted earth fault relay
oil temperature alarm & trip
Winding Temperature & trip
oil Level trip
buchhloz relay
oil surge relay
pressure relief device
HT breaker

Answer / imdad husen

IN TRANSFORMER PROTECTION IF HIGH INTERNAL FAULT OCCUR BETWEEN L.V.C.T.AND H.V.C.T. THEN DIFFERENTIAL RELAY SHOULD BE ORATED AND EXTERNAL FAULT OCCUR DIFFERENTIAL RELAY SHOULD NOT ORATED BECAUSE OF ZERO SEQUENCES CURRENT IS ABSENT
IN TRANSFORMER PROTECTION IF EXTERNAL FAULT OCCUR RESTRICTED EARTH FAULT RELAY SHOULD BE OPARTED

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