Schweitzer Engineering Laboratories SEL-351-5, Инструкция по эксплуатации, Страница: 99 / 706

3.19
Date Code 20070117
Instruction Manual SEL-351-5, -6, -7 Relay
Overcurrent, Voltage, Synchronism Check, Frequency, and Power Elements
Time-Overcurrent Elements
Any time current I
P
goes above pickup setting 51PP and the phase time-
overcurrent element starts timing, Relay Word bit 51PR (reset indication) =
logical 0. If the phase time-overcurrent element times out on its curve, Relay
Word bit 51PT (curve time-out indication) = logical 1.
Setting 51PRS = Y
If electromechanical reset timing setting 51PRS = Y, the phase time-
overcurrent element reset timing emulates electromechanical reset timing. If
maximum phase current, I
P
, goes above pickup setting 51PP (element is
timing or already timed out) and then current I
P
goes below 51PP, the element
starts to time to reset, emulating electromechanical reset timing. Relay Word
bit 51PR (resetting indication) = logical 1 when the element is fully reset.
Setting 51PRS = N
If reset timing setting 51PRS = N, element 51PT reset timing is a one-cycle
dropout. If current I
P
goes above pickup setting 51PP (element is timing or
already timed out) and then current I
P
goes below pickup setting 51PP, there is
a one-cycle delay before the element fully resets. Relay Word bit 51PR (reset
indication) = logical 1 when the element is fully reset.
Operation of Single-Phase Time-Overcurrent Elements (51AT, 51BT, 51CT)
To understand the operation of Figure 3.15 , Figure 3.16 , and Figure 3.17
follow the explanation given for Figure 3.14 in Phase Time-Overcurrent
Elements on page 3.15 , substituting phase current I
A
(or I
B
or I
C
) for
maximum phase current I
P
and substituting like settings and Relay Word bits.
The settings ranges and accuracies for the single-phase time-overcurrent
elements settings are the same as the corresponding settings in
Table 3.2 .
q From Figure 4.24 .
Figure 3.15 A-Phase Time-Overcurrent Element 51AT (With Directional
Control Option)
51AP
I
A
Setting
51ATC
Torque Control Switch
Directional Control
(asserted to logical 1
continuously if E32 = N)
q
(Level 1)
SEL
OGIC
Torque Control
51AT A-Phase
Time-Overcurrent Element
Curve Timing and Reset Timing
Settings
51AP Pickup
51AC Curve Type
51ATD Time Dial
51ARS Electromechanical
Reset? (Y/N)
Pickup
Curve
Timeout
Reset
51A
51AR
51AT
Torque Control
TCA State Switch Position
Logical 1 Closed
Logical 0 Open
Logic Point TCA Controls the Torque Control Switch
Setting
51ARS =
Reset Timing
Y Electromechanical
N 1 Cycle
TCA
Relay
Word
Bits
SEL
OGIC
Setting