Schweitzer Engineering SEL-351P - Pickup Operation

Date Code 990430 Overcurrent, Voltage, Synchronism Check, and Frequency Elements 3-3
SEL-351P Manual Técnico
Figure SECTION 3: .2: Levels 5 through 6 Phase Instantaneous Overcurrent
Elements
Pickup Operation
The phase instantaneous/definite-time overcurrent element logic begins with
Figure SECTION 3:
.1 and
Figure SECTION 3: .2. The pickup settings for each level (50P1P through 50P6P) are
compared to the magnitudes of the individual phase currents I
A
, I
B
, and I
C
. The logic outputs in
Figure SECTION 3: .1 and Figure SECTION 3: .2 are Relay Word bits and operate as follows
(Level 1 example shown):
50A1 = 1 (logical 1), if I
A
> pickup setting 50P1P
= 0 (logical 0), if I
A
≤ pickup setting 50P1P
50B1 = 1 (logical 1), if I
B
> pickup setting 50P1P
= 0 (logical 0), if I
B
≤ pickup setting 50P1P
50C1 = 1 (logical 1), if I
C
> pickup setting 50P1P
= 0 (logical 0), if I
C
≤ pickup setting 50P1P
50P1 = 1 (logical 1), if at least one of the Relay Word bits 50A1, 50B1, or 50C1 is
asserted (e.g., 50B1 = 1)
= 0 (logical 0), if all three Relay Word bits 50A1, 50B1, and 50C1 are deasserted
(50A1 = 0, 50B1 = 0, and 50C1 = 0)
Note that single-phase overcurrent elements are not available in Levels 5 and 6 (see
Figure SECTION 3: .2).
Ideally, set 50P1P > 50P2P > 50P3P > 50P4P so that instantaneous overcurrent elements 67P1
through 67P4 will display in an organized fashion in event reports (see
Figure SECTION 3: .3
and Table 12.3).