transposition and corrona in transmission line

8/17/2019 Transposition and Corrona in Transmission Line

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2/12

Transposition

in

Transmission

lines


3/12


4/12

How

fields

fall

with

distance

from

a

source

Electric fieldsMagnetic fields


5/12

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


6/12

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

transposition and corrona in transmission line

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