GE D90 Plus Instruction Manual page 242

GROUPED PROTECTION ELEMENTS
Breaker failure initiation stage
234
Two schemes are provided: one for three-pole tripping only and one for three pole plus
single-pole operation. The philosophy used in these schemes is identical. The operation of
a breaker failure element includes three stages: initiation, determination of a breaker
failure condition, and output.
Figure 188: Breaker failure main path sequence
The current supervision elements reset in less than 0.7 of a power cycle up to a multiple of
pickup of 100 (threshold set at 0.01 of the actual fault current) as shown below.
Figure 189: Breaker failure current supervision reset time
A FlexLogic™ operand representing the protection trip signal initially sent to the breaker
must be selected to initiate the scheme, except if this is already programmed as a trip
output (the protection trip signal does not include other breaker commands that are not
indicative of a fault in the protected zone). The initiating signal should be sealed-in if
primary fault detection can reset before the breaker failure timers have finished timing.
The seal-in is supervised by current level, so it is reset when the fault is cleared. If desired,
an incomplete sequence seal-in reset can be implemented by using the initiating operand
to also initiate a FlexLogic™ timer, set longer than any breaker failure timer, whose output
operand is selected to block the breaker failure scheme.
PLUS
D90 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 7: PROTECTION