Sel SEL-421 - EPO Setting Selections; Pole Open Logic Relay Word Bits

R.1.21
Date Code 20111215 Reference Manual SEL-421 Relay
Protection Functions
Pole Open Logic
NOTE: The 3PO, SPOA, SPOB, SPOC,
and SPO Relay Word bits shown in
Figure 1.15 are used in some protective
elements of the SEL-421. Separate
Relay Word bits SPOBKn, 3POBKn,
2POBKn (n = 1 or 2), and 3POLINE are
not affected by the EPO setting and
are used in the auto-reclose logic
only—see Figure 2.5 and Figure 2.6.
Set EPO to V only if you use line-side potential transformers for relaying
purposes. Do not select option V if shunt reactors are applied because the
voltage decays slowly after the circuit breaker(s) opens. If you select
EPO := V, the relay cannot declare an open pole when LOP is asserted.
Table 1.21 EPO Setting Selections
Selection Description
52 Phase undercurrent and circuit breaker auxiliary contact input status
V Phase undercurrent and phase undervoltage
Table 1.22 Pole Open Logic Relay Word Bits
Name Description
SPOA A-phase open
SPOB B- phase open
SPOC C- phase open
SPO One or two poles open
3PO All three poles open
27APO A-phase undervoltage
—pole open
27BPO B-phase undervoltage
—pole open
27CPO C-phase undervoltage
—pole open