Schweitzer Engineering Laboratories SEL-351-5, Instruction Manual

Page: 102 / 706

3.22
SEL-351-5, -6, -7 Relay Instruction Manual
Date Code 20070117
Overcurrent, Voltage, Synchronism Check, Frequency, and Power Elements
Time-Overcurrent Elements
Accuracy
Pickup:
±0.05 A secondary and ±3% of setting
(5 A nominal channel
IN
current input)
±0.01 A secondary and ±3% of setting
(1 A nominal channel
IN
current input)
±5 mA secondary and ±3% of setting
(0.2 A nominal channel
IN current input)
±1 mA secondary and ±5% of setting
(0.05 A nominal channel
IN
current input)
Curve Timing:
±1.50 cycles and ±4% of curve time for currents between (and including)
2 and 30 multiples of pickup.
±3.50 cycles and ±4% of curve time for currents between (and including)
2 and 30 multiples of pickup for 0.05 A nominal channel
IN
current input.
Residual Ground
Time-Overcurrent
Element
To understand the operation of Figure 3.19 , follow the explanation given for
Figure 3.14 in Phase Time-Overcurrent Elements on page 3.15 , 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 .
Figure 3.19 Residual Ground Time-Overcurrent Element 51GT (With
Directional Control Option)
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