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 Question Submitted By :: Electrical-Engineering
I also faced this Question!!     Answer Posted By  
# 1
Earth fault relay is a relay which is sense the faults
between the phase and Earth (not b/w neutral to earth)
Is This Answer Correct ?    69 Yes 14 No
Ravi Kumar
# 2
Actually earth fault relay's function is,it calculates the
vector sum of all the three currents flowing in R Y B
lines. If the vector sum is not zero then there is a fault
current flowing in particular line. since these lines are
connected to load say generator then, more than the rated
value of current flowing through windings ,hence windings
will damage so to prevent these type of damages EFR is
if any comments pls send to
Is This Answer Correct ?    62 Yes 8 No
Micro Power System, Bangalore.
# 3
The function of earth fault relay is to to protect the
device from earth fault. there are 2 types of earth fault
fault relays

1.neutral ct conneted earth fault relay. it will sense the
current flowing through neutral while earth lerakage.

2.three phase ct's connected earth fault normal
condition the sum of three phase ct's current in zero.

when earth fault the sum of the 3 phase ct's curret are un
balanced that time relay acts.
Is This Answer Correct ?    20 Yes 0 No
# 4
Function of the earth fault relay is to operate for the
leakage currents to earth. There are two types of earth
fault relays depending up on the configuration
1. Residual current earth fault relay
2. Sensitive earth fault relay
Is This Answer Correct ?    21 Yes 2 No
T Eswara Rao
# 5
I agree with Mr.Ravikumar except in one point.
If the load distribution of a 3 phase 4 wire system is not
balanced in all three phases, there will be some potential
in neutral wire and thus a current flow also.
In this condition, if the neutral wire touches to earth
after the earth fault relay CT, definitely this E/F relay
will sense this current flow from neutral to earth and thus
trip the circuit.
If any other disagreement, please mail me at

Thank you.
Is This Answer Correct ?    20 Yes 3 No
# 6
earth fault relay is a device used protection.
when an unbalance current flows through the line this relay
operates and trips the circuit breaker.
earth fault relay is used between phase and earth faults..
Is This Answer Correct ?    11 Yes 2 No
Madhu Kiran.g
# 7
1.the earth fault relay funtion is to senses and derived
the current from phase to earth fault

depands upon the ct connections used in the scheme
the earth fault relays are classified
1.residual earth fault
2.stand by earth fault
3.restricted earth fault
4.senstive earth fault
all will be derived the input currents from different ct
Is This Answer Correct ?    8 Yes 1 No
# 8
Earth fault relay is sensing the fault between phase to earth and also neutral to earth. When current flowing through earth that time it will be tripped. 
Is This Answer Correct ?    6 Yes 1 No
# 9
earth fault relay operated between two phases for unbalcing
Is This Answer Correct ?    7 Yes 3 No
# 10
The E/F relay will operate under unbalanced condition
i.e 1) during earth fault
2)During any phase open (when unbalanced current
exceeds the relay settings)

Is This Answer Correct ?    5 Yes 2 No

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