Schweitzer Engineering Laboratories SEL-421-4 - Table 5.23 Open-Phase Detection Relay Word Bits; Table 5.24 Pole-Open Logic Settings; Table 5.25 EPO Setting Selections; Table 5.26 Pole-Open Logic Relay Word Bits

5.25
Date Code 20171021 Instruction Manual SEL-421 Relay
Protection Functions
Pole-Open Logic
Pole-Open Logic
The SEL-421 pole-open logic detects single-, double-, and three-pole open con-
ditions. The relay uses the same processing for single- and double-pole open con-
ditions. Pole-open logic supervises various protection elements and functions that
use analog inputs from the power system (e.g., distance elements, directional ele-
ments, LOP logic).
Setting EPO (Enable Pole Open) offers two options for deciding the conditions
that signify an open pole. These options are listed in Table 5.25.
NOTE: The 3PO, SPOA, SPOB, SPOC,
and SPO Relay Word bits shown in
Figure 5.17 are used in some
protective elements of the SEL-421.
Separate Relay Word bits SPOBK
n ,
3POBK
n , 2POBK n ( n = 1 or 2), and
3POLINE are not affected by the EPO
setting and are used in the
autoreclose logic only (see Figure 6.5
on page 6.26 and Figure 6.7 on page 6.27
in the SEL-400 Series Relays Instruction
Manual).
Set EPO to V only if you use line-side potential transformers for relaying pur-
poses. 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
can incorrectly declare LOP during a pole-open condition if there is charging cur-
rent that exceeds the open-pole current threshold.
Table 5.23 Open-Phase Detection Relay Word Bits
Name Description
B1OPHA Breaker 1 A-Phase open
B1OPHB Breaker 1 B-Phase open
B1OPHC Breaker 1 C-Phase open
B2OPHA Breaker 2 A-Phase open
B2OPHB Breaker 2 B-Phase open
B2OPHC Breaker 2 C-Phase open
LOPHA Line A-Phase open
LOPHB Line B-Phase open
LOPHC Line C-Phase open
Table 5.24 Pole-Open Logic Settings
Setting Prompt Range Default
EPO Pole Open Detection 52, V 52
27PO Undervoltage Pole Open Threshold (V)
a
a
1 V steps.
1–200 40
SPOD Single-Pole Open Dropout Delay (cycles) 0.000–60 0.500
3POD Three-Pole Open Dropout Delay (cycles) 0.000–60 0.500
Table 5.25 EPO Setting Selections
Selection Description
52 Phase undercurrent and circuit breaker auxiliary contact input status
V Phase undercurrent and phase undervoltage
Table 5.26 Pole-Open Logic Relay Word Bits (Sheet 1 of 2)
Name Description
SPOA A-Phase open
SPOB B-Phase open