BE1-951
Application
8-49
Table 8-25. Miscellaneous Logic Expressions
Command
Reference
SA-RESET
Section 6,
Reporting and Alarm Functions, Alarms Function
SB-DUTY
Section 6,
Reporting and Alarm Functions, Breaker
Monitoring
SB-LOGIC
Section 6,
Reporting and Alarm Functions, Breaker
Monitoring
SG-TARG
Section 6,
Reporting and Alarm Functions, Fault Reporting
SG-TRIGGER
Section 6,
Reporting and Alarm Functions, Fault Reporting
SP-79ZONE
Section 4,
Protection and Control
APPLICATION TIPS
Trip Circuit and Voltage Monitor
This application tip is intended for feeder applications using FDR-W-IL logic along with BUS and BACKUP
schemes for protection.
OUT1 has a built-in trip circuit voltage and continuity monitor that drives logic variable OUT1MON. This
variable can be used to improve breaker failure logic or to automatically enhance security during testing.
If the relay detects a loss of voltage or continuity in the breaker trip circuit, it’s possible to reduce fault
clearing time by bypassing the breaker failure timer. Since feeder relay “Out of Service” and breaker failure
are covered by different backup actions, it is desirable to reduce common mode failure mechanisms. It is
recommended that the feeder breaker and feeder protection circuits be supplied by separate control power
fuses or breakers. The equation for the breaker failure trip logic (VO5) can be modified by ORing the breaker
failure initiate with the expression VO10*OUT1MON. VO10 is designated in the FDR-W-IL preprogrammed
logic schemes as the breaker failure initiate expression. Example 1 shows how the BFT logic expression
is modified. It’s important that the breaker failure timer bypass logic also be disabled in test mode. Example
2 shows the expression for blocking the upstream instantaneous element. Figure 8-14 illustrates how the
trip circuit continuity monitor can be used in breaker failure logic.
Example 1.
Breaker Failure Trip Expression: SL-VO5=BFT+VO10*OUT1MON*/VO15
Example 2.
Block Upstream Instantaneous Expression: SL-VO4=VO12*/VO5*/OUT1MON*/VO15
