Schweitzer Engineering Laboratories SEL-421-4 - Page 186

5.26
SEL-421 Relay Instruction Manual Date Code 20171021
Protection Functions
Pole-Open Logic
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
Table 5.26 Pole-Open Logic Relay Word Bits (Sheet 2 of 2)
Name Description