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8/17/2019 Transposition and Corrona in Transmission Line
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Transposition
in
Transmission
lines
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How
fields
fall
with
distance
from
a
source
Electric fieldsMagnetic fields
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How
fields
fall
with
distance
from
a
source
Interesting Example:
• Under high voltage power transmission lines fluorescent
light bulbs
light
up
without
having
any
electrical
source.
• Over fifty fluorescent light tubes start lighting up when
one end of the bulb gets stuck into the ground of the
farmland under
a
transmission
8/17/2019 Transposition and Corrona in Transmission Line
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How
fields
fall
with
distance
from
a
source
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How
fields
fall
with
distance
from
a
source
• EMFs from any source usually get less as the distance from
the source increases. Quite often, this can be approximated as
one of
three
basic
types
of
fall
off
with
distance
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How
fields
fall
with
distance
from
a
source
• Inverse first power of distance
– An example is the magnetic field from a net current in a distribution
circuit.
• Inverse square of distance
– An example is the magnetic field from some transmission lines (either
with a single circuit or two circuits but untransposed phasing)
• Inverse
cube
of
distance
– An example is a transmission line with transposed phasing, or a
domestic appliance
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How does the balance of the currents within each circuit affect
the
field
from
an
overhead
power
lines?
• If the currents in the phases are not exactly equal, the
cancellation is not as good, and the magnetic field is larger.
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“Untransposed”
and
“Transposed"
phasing
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Corona
Inspection
• Locating Corona generated by missing ring on insulator