Schweitzer Engineering Laboratories SEL-387-0, Instruction Manual

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3.55
Date Code 20050919
Instruction Manual SEL-387-0, -5, -6 Relay
Differential, Restricted Earth Fault, Thermal, and Overcurrent Elements
Overcurrent Element
50Pn1–Phase Definite-Time Element
Figure 3.20 shows the logic for the 50P n 1 element. The logic compares the
magnitudes of phase input currents IAW n , IBW n , and ICW n to pickup setting
50P n 1P. If one or more current magnitudes exceed the pickup level, a logic 1
asserts at one input to the AND gate at the center. The torque-control
SEL
OGIC
control equation 50P n 1TC determines the other AND input. If
50P n 1TC is true, Relay Word bit 50P n 1 asserts and starts the timer. After the
time specified by delay setting 50P n 1D expires, a second Relay Word bit,
50P n 1T, asserts. This bit asserts only if the 50P n 1 bit remains asserted for the
duration of 50P n 1D. When 50P n 1 deasserts, the timer resets without delay,
along with 50P n 1T if it has asserted.
Figure 3.20 50Pn1 Phase Definite-Time O/C Element, Torque Controlled
50Pn2–Phase Instantaneous Element
Figure 3.21 shows the logic for the 50P n 2 element. The 50P n 2 element logic
compares magnitudes of phase input currents IAW n , IBW n , and ICW n to
pickup setting 50P n 2P. If one or more current magnitudes exceed the pickup
level, a logic 1 asserts at one input to the AND gate. The torque-control
SEL
OGIC
control equation 50P n 2TC determines the other AND input. If
50P n 2TC is true, Relay Word bit 50P n 2 asserts.
Figure 3.21 50Pn2 Phase Instantaneous O/C Element, Torque Controlled
50Pn3 and 50Pn4–Phase Instantaneous Element
Figure 3.22 shows the logic for the two nontorque-controlled phase
instantaneous elements. The two elements find application primarily in level
detection or phase identification. The logic compares magnitudes of phase
input currents IAWn, IBWn, and ICWn to pickup setting 50P
n 3P(4P). Any
phase current exceeding the pickup level will assert the appropriate phase-
specific Relay Word bit, 50A
n 3(4), 50B n 3(4), or 50C n 3(4). These bits enter
an OR gate to assert Relay Word bit 50P n 3(4), indicating “any phase” pickup.
+
–
D
0
50Pn1T
–
+
+
–
50Pn1
D = 50Pn1D
(n = Winding 1, 2, 3, or 4)
|IAWn|
|IBWn|
|ICWn|
50Pn1P
Relay
Word
Bit
Relay
Word
Bit
50Pn1TC (SEL
OGIC
control equation TRUE)
+
–
–
+
+
–
50Pn2
(n = Winding 1, 2, 3, or 4)
|
IAWn
|
|
IBWn
|
|
ICWn
|
50Pn2P
Relay
Word
Bit
50Pn2TC (SEL
OGIC
control equation TRUE)