Sel 751A - Time-Overcurrent Curves; Figure 4.7 Residual Time-Overcurrent Elements 51 G1 T and 51 G2 T

4.15
Date Code 20100129 Instruction Manual SEL-751A Relay
Protection and Logic Functions
Basic Protection
The residual time-overcurrent elements, 51G1T and 51G2T, respond to
residual current IG as shown in Figure 4.7.
Figure 4.7 Residual Time-Overcurrent Elements 51G1T and 51G2T
Time-Overcurrent
Curves
The following information describes the curve timing for the curve and time
dial settings made for the time-overcurrent elements (see Figure 4.3 through
Figure 4.7). The U.S. and IEC time-overcurrent relay curves are shown in
Figure 4.8 through Figure 4.17. Curves U1, U2, and U3 (Figure 4.8 through
Figure 4.10) conform to IEEE C37.112-1996 IEEE Standard Inverse-Time
Characteristic Equations for Overcurrent Relays.
TOC CURVE SEL U1, U2, U3, U4, U5, C1, C2,
C3, C4, C5
51G2C := U3
TOC TIME DIAL 0.50–15.00
c
,
0.05–1.00
d
51G2TD := 1.50
EM RESET DELAY Y, N 51G2RS := N
CONST TIME ADDER 0.00–1.00 sec 51G2CT := 0.00
MIN RESPONSE TIM 0.00–1.00 51G2MR := 0.00
TOC TRQ CONTROL SELOGIC 51G2TC := 1
a
For I
NOM
= 5 A.
b
For I
NOM
= 1 A.
c
For 51_C := U_ .
d
For 51_C := C_.
Table 4.12 Residual Time-Overcurrent Settings (Sheet 2 of 2)
Setting Prompt Setting Range
Setting Name :=
Factory Defau lt
51G1P
|IG|
Setting
51G1TC
Torque Control Switch
SELOGIC
Torque Control
Pickup
Curve
Timeout
Reset
51G1P
51G1R
51G1T
51G1TC Torque Control
State Switch Position
Logical 1 Closed
Logical 0 Open
Setting
51G1RS = Reset Timing
Y Electromechanical
N 1 Cycle
Relay
Word
Bits
SELOGIC
Setting
51G1T Residual
Time-Overcurrent Element
Curve Timing and Reset Timing
Settings
51G1P Pickup
51G1C Curve Type
51G1TD Time Dial
51G1RS Electromechanical
Reset? (Y/N)
51G1CT Const. Time Add.
51G1MR Min. Response
(From Figure 4.1)
Controls the Torque Control Switch
Note: 51G1T element shown above; 51G2T is similar.
where:
t
p
= operating time in seconds
t
r
= electromechanical induction-disk emulation reset time in
seconds (if you select electromechanical reset setting)
TD = time-dial setting
M = applied multiples of pickup current [for operating time
(t
p
), M>1; for reset time (t
r
), M≤1]