8-14 Option 100 Fault Location and SRL
Key Reference
Alphabetical Key Reference
Softkey in the menu.
The fault location measurement mode provides a windowing feature
that makes fault measurements more useful for isolating and
identifying individual responses. Windowing is needed because of the
abrupt transitions in a frequency domain response at the start and
stop frequencies. The band limiting of a frequency domain response
causes overshoot and ringing in the distance domain response. This
gives a non-windowed impulse stimulus a sin (ωt) /ωt shape where
ω=π/(frequency span). This has two effects that limit the usefulness
of the fault location measurement:
1. Finite impulse width (or rise time): This limits the ability to
resolve between two closely spaced responses. The effects of the
finite impulse are improved as the frequency span is increased.
2. Sidelobes: The impulse sidelobes limit the dynamic range of the
time domain measurement by hiding low-level responses within
the sidelobes of higher level responses. The effects of sidelobes
can be improved by windowing.
Windowing improves the dynamic range of a distance domain
measurement by filtering the frequency domain data prior to
converting to the distance domain, producing an impulse response
that has lower sidelobes. This makes it much easier to see distance
domain responses that are different in magnitude. This sidelobe
reduction is achieved, however, at the expense of increased impulse
width.
The following options are available under the window menu:
•
This is essentially no window. It gives the highest sidelobes and
the narrowest impulse response.
•
This is the default selection. Selecting medium provides reduced
sidelobes.
•
This selection provides minimum sidelobes but the widest
impulse response.
AVG
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