3.21
Date Code 20070117
Instruction Manual
SEL-351-5, -6, -7 Relay
Overcurrent, Voltage, Synchronism Check, Frequency, and Power Elements
Time-Overcurrent Elements
Neutral Ground Time-
Overcurrent Element
q
.
Figure 3.18
Neutral Ground Time-Overcurrent Element 51NT (With
Directional Control Option)
To understand the operation of
, follow the explanation given for
Phase Time-Overcurrent Elements on page 3.15
, substituting
current I
N
(channel IN current) for maximum phase current I
P
and substituting
like settings and Relay Word bits.
See
and the accompanying note for a list of the directional features
available with each neutral channel (IN) rating.
Settings Ranges
See
for additional time-overcurrent element
setting information.
51NP
I
N
Setting
51NTC
Torque Control Switch
Directional Control
(asserted to logical 1
continuously if E32 = N)
q
(Level 1)
SEL
OGIC
Torque Control
51NT Neutral Ground
Time-Overcurrent Element
Curve Timing and Reset Timing
Settings
51NP
Pickup
51NC
Curve
Type
51NTD
Time
Dial
51NRS
Electromechanical
Reset? (Y/N)
Pickup
Curve
Timeout
Reset
51N
51NR
51NT
Torque
Control
TCN State
Switch Position
Logical 1
Closed
Logical 0
Open
Logic Point TCN Controls the Torque Control Switch
Setting
51NRS =
Reset Timing
Y
Electromechanical
N
1
Cycle
TCN
Relay
Word
Bits
SEL
OGIC
Setting
Table 3.4
Neutral Ground Time-Overcurrent Element Settings
Setting
Definition
Range
51NP
pickup
0.500–16.000 A secondary
(5 A nominal channel
IN
current input)
0.100–3.200 A secondary
(1 A nominal channel
IN
current input)
0.005–0.640 A secondary
(0.2 A nominal channel
IN
current input)
0.005–0.160 A secondary
(0.05 A nominal channel
IN
current input)
51NC
curve type
U1–U5 (US curves) see
C1–C5 (IEC curves)
51NTD
time dial
0.50–15.00 (US curves) see
0.05–1.00 (IEC curves)
51NRS
electromechanical
reset timing
Y, N
51NTC
SEL
OGIC
control
equation torque
control setting
Relay Word bits referenced in
or set
directly to logical 1 (= 1)—see note
NOTE:
SEL
OGIC
control equation
torque control setting (e.g., 51NTC)
cannot be set directly to logical 0.
Summary of Contents for SEL-351-5
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