3.22
SEL-351A Relay
Instruction Manual
Date Code 20080213
Overcurrent, Voltage, Synchronism Check, and Frequency Elements
Time-Overcurrent Elements
q
From Figure 4.24. Directional Control logic input is constantly asserted to
logical 1 in SEL-351A-1.
Figure 3.17
C-Phase Time-Overcurrent Element 51CT (With Directional
Control Option in SEL-351A)
Neutral-Ground Time-
Overcurrent Element
To understand the operation of
, follow the explanation given for
in
Phase Time-Overcurrent Elements on page 3.16
, substituting
current I
N
(channel
IN
current) for maximum phase current I
P
and substituting
like settings and Relay Word bits.
and the accompanying note for a list of the directional features
available with each neutral channel (
IN
) rating.
q
From Figure 4.18. Directional Control logic input is constantly asserted to logical
1 in SEL-351A-1.
Figure 3.18
Neutral-Ground Time-Overcurrent Element 51NT (With
Directional Control Option in SEL-351A)
51CP
I
C
Setting
51CTC
Torque Control Switch
Directional Control
(asserted to logical 1
continuously if E32 = N)
q
(Level 1)
SEL
OGIC
Torque Control
51CT C-Phase
Time-Overcurrent Element
Curve Timing and Reset Timing
Settings
51CP
Pickup
51CC
Curve
Type
51CTD
Time
Dial
51CRS
Electromechanical
Reset? (Y/N)
Pickup
Curve
Timeout
Reset
51C
51CR
51CT
Torque
Control
TCC State
Switch Position
Logical 1
Closed
Logical 0
Open
Logic Point TCC Controls the Torque Control Switch
Setting
51CRS =
Reset Timing
Y
Electromechanical
N
1
Cycle
TCC
Relay
Word
Bits
SEL
OGIC
Setting
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
Summary of Contents for SEL-351A
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