Schweitzer Engineering SEL-387-0 - Figure 3.22 50 Qn1 and 50 Nn1 Sequence Definite-Time O;C Element, Torque Controlled; Figure 3.23 50 Qn2 and 50 Nn2 Sequence Instantaneous O;C Element, Torque Controlled

3.52
SEL-387-0, -5, -6 Relay Instruction Manual Date Code 20170601
Differential, Restricted Earth Fault, Thermal, and Overcurrent Elements
Overcurrent Element
Figure 3.22 50Qn1 and 50Nn1 Sequence Definite-Time O/C Element,
Torque Controlled
50Qn1 Negative-Sequence Definite-Time Element
The 50Qn1 element logic compares the magnitude of calculated negative-
sequence current 3I2Wn to pickup setting 50Qn1P. If the calculated negative-
sequence current magnitude exceeds the pickup level, a logical 1 asserts at one
input to the AND gate at the center. The torque-control SEL
OGIC control
equation, 50Qn1TC, determines the other AND input. If 50Qn1TC is true,
Relay Word bit 50Qn1 asserts and the timer starts. After the time specified by
delay setting 50Qn1D has expired, a second Relay Word bit, 50Qn1T, asserts.
The 50Qn1T bit asserts only if the 50Qn1 bit remains asserted for the duration
of 50Qn1D. When 50Qn1 deasserts, the timer resets without delay, along with
50Qn1T if it has asserted.
50Nn1 Residual Definite-Time Element
The 50Nn1 element logic compares the magnitude of the calculated residual
current, IRWn, to the pickup setting, 50Nn1P. If the calculated residual current
magnitude exceeds the pickup level, a logical 1 asserts at one input to the
AND gate at the center. The torque-control SEL
OGIC control equation,
50Nn1TC, determines the other AND input. If 50Nn1TC is true, Relay Word
bit 50Nn1 asserts and the timer starts. After the time specified by delay setting
50Nn1D has expired, a second Relay Word bit, 50Nn1T, asserts. The 50Nn1T
bit asserts only if the 50Nn1 bit remains asserted for the duration of 50Nn1D.
When 50Nn1 deasserts, the timer resets without delay, along with 50Nn1T if it
has asserted.
50Qn2 and 50Nn2–Sequence Instantaneous Element Logic
Figure 3.23 shows the logic for the instantaneous 50Qn2 negative-sequence
element and the instantaneous 50Nn2 residual element.
Figure 3.23 50Qn2 and 50Nn2 Sequence Instantaneous O/C Element,
Torque Controlled
50Qn2 Negative-Sequence Instantaneous Element
The 50Qn2 element compares the magnitude of the calculated negative-
sequence current, 3I2Wn, to the pickup setting, 50Qn2P. If the calculated
negative-sequence current exceeds the pickup level, a logical 1 asserts at one
+
–
D
0
(50Nn1)
D = 50Qn1D
(n = Winding 1, 2, 3, or 4)
|3I2Wn| (|IRWn|)
50Qn1P (50Nn1P)
50Qn1
(50Nn1T)
50Qn1T
(50Nn1D)
Relay
Wo
rd
Bits
Relay
Word
Bits
51Qn1TC (50Nn1TC)
(SEL
OGIC control equation TRUE)
+
–
(n = Winding 1, 2, 3, or 4)
(50Nn2)
50Qn2
Relay
Word
Bits
51Qn2TC (50Nn2TC)
(SEL
OGIC control
equation TRUE)
|3I2Wn| (|IRWn|)
50Qn2P (50Nn2P)