CHAPTER 7: PROTECTION
GROUPED PROTECTION ELEMENTS
D90
PLUS
LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
273
Events
Range: Enabled, Disabled
Default: Disabled
This setting enables and disables the logging of auxiliary overvoltage events in the
sequence of events recorder.
The logic for the auxiliary overvoltage element is shown below. The logic is identical for all
auxiliary overvoltage elements.
Figure 235: Auxiliary overvoltage scheme logic
Breaker failure
In general, a breaker failure scheme determines that a breaker signaled to trip has not
cleared a fault within a definite time, so further tripping action must be performed. Tripping
from the breaker failure scheme should trip all breakers, both local and remote, that can
supply current to the faulted zone. Usually operation of a breaker failure element will cause
clearing of a larger section of the power system than the initial trip. Because breaker
failure can result in tripping a large number of breakers and this affects system safety and
stability, a very high level of security is required.
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 236: 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.
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