
3.24
SEL-351A Relay
Instruction Manual
Date Code 20080213
Overcurrent, Voltage, Synchronism Check, and Frequency Elements
Time-Overcurrent Elements
To understand the operation of
and
, follow the
explanation given for
Phase Time-Overcurrent Elements on
, substituting residual-ground current I
G
(I
G
= 3I
0
= I
A
+ I
B
+ I
C
) for
maximum phase current I
P
and substituting like settings and Relay Word bits.
q
From Figure 4.17. Directional Control logic input is constantly asserted to logical
1 in SEL-351A-1.
Figure 3.19
Residual-Ground Time-Overcurrent Element 51GT (With
Directional Control Option in SEL-351A)
Settings Ranges
Table 3.5
Available Residual-Ground Time-Overcurrent Elements
Time-Overcurrent
Element
Enabled With
Setting
Operating Current
See Figure
SEL-351A
51GT
E51G = 1 or 2
I
G
= 3I
0
= calculated residual
ground current
51G2T
E51G = 2
I
G
= 3I
0
= calculated residual
ground current
SEL-351A-1
51GT
E51G = Y
I
G
= 3I
0
= calculated residual
ground current
51GP
(residual)
I
G
Setting
51GTC
Torque Control Switch
Directional Control
(asserted to logical 1
continuously if E32 = N)
q
(Level 1)
SEL
OGIC
Torque Control
51GT Residual Ground
Time-Overcurrent Element
Curve Timing and Reset Timing
Settings
51GP
Pickup
51GC
Curve
Type
51GTD
Time
Dial
51GRS
Electromechanical
Reset? (Y/N)
Pickup
Curve
Timeout
Reset
51G
51GR
51GT
Torque
Control
TCG1 State
Switch Position
Logical 1
Closed
Logical 0
Open
Logic Point TCG Controls the Torque Control Switch
Setting
51GRS =
Reset Timing
Y
Electromechanical
N
1
Cycle
TCG1
Relay
Word
Bits
SEL
OGIC
Setting
Table 3.6
Residual-Ground Time-Overcurrent Element 51GT Settings
(Sheet 1 of 2)
Setting
Definition
Range
51GP
pickup
0.10–16.00 A secondary
(5 A nominal phase current inputs,
IA
,
IB
,
IC
)
0.02–3.20 A secondary
(1 A nominal phase current inputs,
IA
,
IB
,
IC
)
51GC
curve type
U1–U5 (US curves) see
–
C1–C5 (IEC curves)
51GTD
time dial
–
0.05–1.00 (IEC curves)
Содержание SEL-351A
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