I.L. 40-386.4
4-12
to complete isolation of the failed breaker. If current above the settings of IM or IOM is not
present, at the end of the breaker failure time, all logic simply resets. Breaker failure timing con-
siderations are shown in the table above.l
2.
REL 301/302 Contact Programming
Each relay output contact can be programmed as a combination of internally generated signals
and an associated on delay and/or off delay timer(s). The programming is accomplished using
the Relay Communications Program (RCP) and selecting the “UPDATE PROG CONT SET-
TINGS” from the Password Commands menu. For complete details on using RCP, refer to Sec-
tions 4.6 and 4.7 and IL 40-603, RCP Remote Communication Program, USER’S GUIDE.
Programming of the contacts starts by establishing communication with the relay and selecting
contact programming choices screen. Programming each contact, and the associated timer(s),
is explained in Section 4.10. When the contact programming is complete the contact program-
ming choices screen should appear as in REL 301/302 PROGRAMMABLE CONTACT SET-
TINGS (Breaker Failure) table, at the end of this section, with time delays filled in for each of
the following:
BF1
= Breaker Failure Time (Phase)
BF2
= Breaker Failure Time (Ground)
R1,2
= Reset Time Delay
3.
Settings
(a) Overcurrent units
The phase unit, IM, must be set below the minimum expected (CT secondary) phase fault cur-
rent through the protected breaker, and the ground unit must be set less than the minimum ex-
pected 3I0 fault current.
Settings should be made to assure a multiple of pickup of at least 2, under minimum fault con-
ditions. Where the breaker contains a resistor, that is inserted on tripping, the overcurrent fault
detectors are set below the resistor current.
(b) Breaker failure timers (BF)
The breaker failure timers (BF1,2) should be set to exceed the breaker normal clearing time by
an appropriate margin. A secure margin is 2 cycles (32 ms). Refer to Breaker Failure Timing
Diagram (above). Often it is desirable to set the breaker failure times for different values for
phase and ground faults.
(c) Reset Timers (R)
A small reset time is suggested to assure the 86BF lockout device has operated. OC3 and OC4
have a low interrupting capability (see Section 1.6 for contact ratings).
4.
External Connections
See Figure 4-4 for external connections to complete the breaker failure scheme.
