Schweitzer Engineering SEL-387-0, Instruction Manual

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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 50Q n 1 element logic compares the magnitude of calculated negative-
sequence current 3I2W n to pickup setting 50Q n 1P. 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, 50Q n 1TC, determines the other AND input. If 50Q n 1TC is true,
Relay Word bit 50Q n 1 asserts and the timer starts. After the time specified by
delay setting 50Q n 1D has expired, a second Relay Word bit, 50Q n 1T, asserts.
The 50Q n 1T bit asserts only if the 50Q n 1 bit remains asserted for the duration
of 50Q n 1D. When 50Q n 1 deasserts, the timer resets without delay, along with
50Q n 1T if it has asserted.
50Nn1 Residual Definite-Time Element
The 50N n 1 element logic compares the magnitude of the calculated residual
current, IRW n , to the pickup setting, 50N n 1P. 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,
50N n 1TC, determines the other AND input. If 50N n 1TC is true, Relay Word
bit 50N n 1 asserts and the timer starts. After the time specified by delay setting
50N n 1D has expired, a second Relay Word bit, 50N n 1T, asserts. The 50N n 1T
bit asserts only if the 50N n 1 bit remains asserted for the duration of 50N n 1D.
When 50N n 1 deasserts, the timer resets without delay, along with 50N n 1T if it
has asserted.
50Qn2 and 50Nn2–Sequence Instantaneous Element Logic
Figure 3.23 shows the logic for the instantaneous 50Q n 2 negative-sequence
element and the instantaneous 50N n 2 residual element.
Figure 3.23 50Qn2 and 50Nn2 Sequence Instantaneous O/C Element,
Torque Controlled
50Qn2 Negative-Sequence Instantaneous Element
The 50Q n 2 element compares the magnitude of the calculated negative-
sequence current, 3I2W n , to the pickup setting, 50Q n 2P. 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
Word
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)