Spectral Analysis Algorithm; Load Event Detector Algorithm; Load Analysis Algorithm; Load Extraction Algorithm - GE F60 Instruction Manual

CHAPTER 9: THEORY OF OPERATION

9.1.5 Spectral Analysis algorithm

The Spectral Analysis algorithm is the third and final confirmation algorithm performed only when a high impedance
condition is suspected.
The Spectral Analysis algorithm receives five seconds of averaged non-harmonic residual current spectrum data and
compares it to an ideal 1 / f curve. Depending on the result, three percent can be added to the arcing confidence level
generated by the Expert Arc Detector algorithm.

9.1.6 Load Event Detector algorithm

The Load Event Detector algorithm examines, on a per-phase basis, one reading of RMS values per two-cycle interval for
each phase current and the neutral. It then sets flags for each phase current and for the neutral based on the following
events:
• An overcurrent condition
• A precipitous loss of load
• A high rate-of-change
• A significant three-phase event
• A breaker open condition
These flags are examined by the Load Analysis algorithm. Their states contribute to that algorithm's differentiation
between arcing downed conductors and arcing intact conductors, and inhibit the Expert Arc Detector algorithm from
indicating the need for an arcing alarm for a limited time following an overcurrent or breaker open condition.
Any of these five flags zero the Expert Arc Detector buffer, since the power system is in a state of change and the values
being calculated for use by the Energy and Randomness algorithms are probably not valid.
An extremely high rate of change is not characteristic of most high impedance faults and is more indicative of a breaker
closing, causing associated inrush. Since this type of inrush current causes substantial variations in the harmonics used by
the high impedance algorithms, these algorithms ignore all data for several seconds following a high rate-of-change event
that exceeds the associated rate-of-change threshold, in order to give the power system a chance to stabilize.

9.1.7 Load Analysis algorithm

The Load Analysis algorithm differentiates between arcing downed conductors and arcing intact conductors by looking for
a precipitous loss of load and/or an overcurrent disturbance at the beginning of an arcing episode. The presence of arcing
on the system is determined based on the output of the Expert Arc Detector algorithm. If the Hi-Z element finds persistent
arcing on the power system, the Load Analysis algorithm then considers the type of incident that initiated the arcing and
classifies the arcing conductor as either downed or intact. Another function of the algorithm is to provide coordination
between the Hi-Z element and the power system's conventional overcurrent protection by observing a timeout, via the
Z OC PROTECTION COORD TIMEOUT
If the Load Analysis algorithm determines that a downed conductor or arcing exists, it attempts to determine the phase on
which the high impedance fault condition exists. It does this in a hierarchical manner. First, if a significant loss of load
triggered the Load Analysis algorithm, and if there was a significant loss on only one phase, that phase is identified. If there
was not a single phase loss of load, and if an overcurrent condition on only one phase triggered the algorithm, that phase
is identified. If both of these tests fail to identify the phase, the phase with a significantly higher confidence level (for
example higher than the other two phases by at least 25%) is identified. Finally, if none of these tests provides phase
identification, the result of the Arc Burst Pattern Analysis algorithm is checked. If that test fails, the phase is not identified.

9.1.8 Load Extraction algorithm

The Load Extraction algorithm attempts to find a quiescent period during an arcing fault so that it can determine the
background load current level in the neutral current. If it is successful in doing so, it then removes the load component
from the total measured current, resulting in a signal that consists only of the fault component of the neutral current. This
information is then provided as input to the Arc Burst Pattern Analysis algorithm.
F60 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
setting from the beginning of the arcing before giving an indication of arcing.
HIGH-IMPEDANCE (HI-Z) FAULT DETECTION
HI-
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