3-38 Breaker Logic Date Code 20010731
SEL-352-1, -2 Instruction Manual
Flashover Failure (FFpu)
Range: 0–16383 cycles in 1/4-cycle steps
Use SET <ENTER> to access the FFpu setting and determine the delay before the 62FF timer
expires and asserts the timer output FFAD. Assertion of this output results in assertion of the
FOBF (breaker failure) Relay Word bit.
Set flashover failure timer setting FFpu based on the disruptive effects of breaker flashover on
load and generation equipment and system stability. A recommended setting is FFpu = 30
cycles.
Load Detector (50LD)
Range: 0.01–45.00 A in 0.01-A steps (5 A)
0.02–9.00 A in 0.01-A steps (1 A)
The flashover logic uses the load current detector 50LD setting, but you set the value for this
setting along with the load current protection logic. Use SET <ENTER> to access the 50LD
setting and establish the level of current above which the 62FP and 62FF flashover timers will
start if the breaker is open.
Set the 50LD (in settings for the load current protection logic) based on the same criteria as
outlined for the load current protection logic earlier in this section.
CURRENT UNBALANCE PROTECTION
Application Description
The relay uses current unbalance logic to detect unbalance among the three-phase current
magnitudes and to indicate failed closing of one or two breaker poles.
Operating Characteristic
Figure 3.23 shows the logic that detects unbalanced current conditions, which indicate that one
or two breaker poles failed to close.
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