GE MFAC 14, User Manual

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The minimum knee point voltage must be
V
K
≥
2V
R
The operating current of the relay is 38mA, irrespective of tap selected, excluding
the current drawn by the external metrosil. When a standard metrosil is included
with the relay, the relay operating current including the metrosil is given in the table
below.
It must be appreciated that metrosils have large tolerances and these figures
are given for guidance only.
a) Low range relay (5V steps)
Setting voltage V
R
15 50 75 100 125 150 175 185
Relay current
I
R
(mA) 38 38 39 42 46 55 72 81
(including metrosil, C = 450)
b) Low range relay
Setting voltage V
R
25 50 75 100 125 150 175
Relay current
I R
(mA) 19 19 20 23 27 36 53
(including metrosil, C = 450)
c) High range relay
Setting voltage V
R
25 75 125 175 225 275 325
Relay current
I R
(mA) 19 19 20 22 24 31 44
(including metrosil, C = 900)
d) 100–400V version
Setting voltage V
R
100 150 200 250 300 350 400
Setting voltage I
R
(mA) 19 19 20 20 23 27 36
(including metrosil, C = 1100)
The primary current for operation is given by
I
P
= N (
I
R
+ n
I
E
)
If the resultant value of I
P
is too low it may be increased by the addition of a
shunt resistor R
SH
to give a current of
I SH
= V
R
R
SH
The new increased value of primary current
I
P
= N (
I
R
+ n
I
E
+
I
SH
)
External metrosils.
Each FAC relay is applied with an external metrosil which must be wired across
the relay circuit. This provides a shunt circuit for high internal fault currents and
prevents a high voltage being developed across the CT and relay circuits.
2.1.4 Commissioning preliminaries.
Inspection.
Carefully examine the module and case to see that no damage has occurred
during transit. Check that the relay serial number on the module, case and cover
are identical, and that the model number and rating information are correct.
Carefully remove any elastic bands/packing fitted for transportation purposes.
Carefully actuate the armature of each unit in turn with a small screwdriver/probe.
Note that immediately after the point where any normally open contacts just make
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