Woodward
Manual MRI3 GB
40
DOK-TD-MRI3 Rev.A
Relay function
Output relays
Display-
indication
Lighted
LED
1 2 3 4
I> (V)
alarm
X
_ 2 _ _
I>;
→←
green
tI> (V)
tripping
X
1 _ _ _
t
I>
;
→←
grün
I> (R)
alarm
X
_ 2 _ _
I>;
→←
red
tI> (R)
tripping
X
1 _ _ _
t
I>
;
→←
red
I>> (V)
alarm
X
_ _ 3 _
I>>;
→←
green
tI>> (V)
tripping
X
1 _ _ _
t
I>>
;
→←
green
I>> (R)
alarm
X
_ _ 3 _
I
>>
;
→←
red
tI>> (R)
tripping
X
1 _ _ _
t
I>>
;
→←
red
IE> (V)
alarm
X
_ _ _ 4
I
E>
;
→←
green
tIE> (V)
tripping
X
1 _ _ _
t
IE>
;
→←
green
IE> (R)
alarm
X
_ _ _ 4
I
E>
;
→←
red
tIE> (R)
tripping
X
1 _ _ _
t
IE>
;
→←
red
IE>> (V)
alarm
X
_ _ _ 4
I
E>>
;
→←
green
tIE>> (V)
tripping
X
1 _ _ _
t
IE>>
;
→←
green
IE>> (R)
alarm
X
_ _ _ 4
I
E>>
;
→←
red
tIE>> (R)
tripping
X
1 _ _ _
t
IE>>
;
→←
red
tCBFP
tripping
_ _ _ _
C.B.; red
(V) = forward direction;
(R) = backward direction
This way, a tripping relay can be set for each activation and tripping direction.
Table 5.3: Example of assignment matrix of the output relays (default settings).
5.8 Setting value calculation
5.8.1 Definite time overcurrent element
Low set element (I>)
The pickup current setting is determined by the load capacity of the protected object and by the
smallest fault current within the operating range. The pickup current is usually selected about 20%
for power lines, about 50% for transformers and motors above the maximum expected load cur-
rents.
The delay of the trip signal is selected with consideration to the demand on the selectivity accord-
ing to system time grading and overload capacity of the protected object.
High set element (I>>)
The high set element is normally set to act for near-by faults. A very good protective reach can be
achieved if the impedance of the protected object results in a well-defined fault current. In case of a
line-transformer combination the setting values of the high set element can even be set for the fault
inside the transformer.
The time delay for high set element is always independent to the fault current.
