Schweitzer Engineering Laboratories SEL-387E - 50 Pn2 - Phase Instantaneous Element; 50 Pn3 and 50 Pn4 - Phase Instantaneous Element

3-36 Protection Functions Date Code 20080110
SEL-387E Instruction Manual
Figure 3.15: 50Pn1 Phase Definite-Time O/C Element, Torque Controlled
50Pn2 – Phase Instantaneous Element
Figure 3.16 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 3.16: 50Pn2 Phase Instantaneous O/C Element, Torque Controlled
50Pn3 and 50Pn4 – Phase Instantaneous Element
Figure 3.17 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 IAW
n , IBW n , and ICW n 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.