变电所中英文对照外文翻译文献

2021年1月26日发(作者：symmetry)
中英文对照外文翻译文献







中英文对照外文翻译






Reliability of Lightning Resistant
Overhead Distribution Lines










Lighting continues to be the major cause of outages on
overhead power distribution lines. Through laboratory testing and
field observations and measurements, the properties of a lightning
stroke and its effects on electrical


distribution system
components are well- understood phenomena. This paper presents a
compilation of 32 years of historical records for outage causes,
duration, and locations for eight distribution feeders at the Oak
Ridge National Laboratory (ORNL) .
Distribution type lightning arresters are placed at dead-end and
angle
structures
at
pole
mounted
wormer
locations
and
at
high
points
on
the
overhead
line.
Station
class
lightning
arresters
are
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中英文对照外文翻译文献

used
to
protect
underground
cable
runs,
pad
mounted
switchgear
and unit substation


transformers. Resistance to earth of each pole
ground
is
typically
15
ohms


or
less.
At
higher
elevations
in
the
system,
resistance
to
earth

is
substantially
greater
than
15
ohms,
especially
during
the
dry
summer
months.
At
these
high
points,
ground
rods
were
riven
and
bonded
to
the
pole
grounding
systems

in
the
1960's
in
an
attempt
to
decrease
lightning
outages.
These
attempts were only partially successful in lowering the outage rate.
From
a
surge
protection

standpoint
the
variety
of
pole
structures
used
(in-line,
corner,
angle,
dead
end,
etc.)
and
the
variety
of
insulators
and
hardware
used
does
not
allow
each


13.8
kV
overhead
line
to
be
categorized
with
a
uniform
impulse
flashover
rating (170 kV, etc.) or a numerical BIL voltage

class (95 kV BIL;
etc.).

For simplicity purposes in

the analysis, each overhead line
was
categorized
with
a
nominal
voltage
construction
class
(15
kV,
34 kV, or 69 KV). Six of the eight overhead lines (feeders 1 through
6) were built with typical REA Standard horizontal wood cross arm

construction
utilizing
single
ANSI
Class
55-5
porcelain
pin

insulators
(nominal
15
kV
insulation).
The
shield
angle
of


the
overhead
ground
wire
to
the
phase
conductors
is
typically

45
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中英文对照外文翻译文献

degrees.


One
overhead
line
(feeder
7)
was
built
with
transmission type wood pole construction because the line extended
to a research facility which was to have generated electrical power
to feed back into the grid. Pole structure of this line are of durable
wood
cross
a
construction
which
utilize
double

ANSI
52-3

porcelain
suspension
insulators
to
support

the
conductors
(nominal
34
kV
insulation).
The
shield
angle
of
the
overhead
ground
wire
to
the
phase
conductors
for
feeder
7
is
typically
30
degrees. In 1969, an overhead line (feeder 8) was intentionally built
with

resistant
construction
in
an
attempt
to
reduce
lightning
caused
outages.
Pole
structures
of
the
line
have


phase
over phase 24-inch long fiberglass suspension brackets with double


ANSI
52-3
porcelain
suspension
insulators
to
support
the
conductors
(nominal


69
kV
insulation).
The
shield
angle
of
the
overhead
ground
wire
to
the

phase
conductors
for
feeder
8
is
typically 30 degrees.

The failure data was


compiled for each of
the
eight
13.8
kV
feeders
and
is
presented
in
Table,

along
with
pertinent
information
regarding
feeder
construction,
elevation,
length, and age.
A
key
finding
of
the
failure
analysis
is
that
weather-related
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中英文对照外文翻译文献

events

account for over half (56%) of the feeder outages recorded.
Fifty-seven
of
the
76
weather-related
outages
were
attributed
to
lightning.
Insulation
breakdown
damage
due
to
lightning
is
also
suspected in at least a dozen of the


equipment failures observed.
The data indicates overhead

lines which pass over high terrain are
less
reliable
because
of
the
greater
exposure
to
lightning.

For
example,
feeder
3
had
the
most
recorded
outages
(48),
of
which
two-thirds were due to weather- related events; this feeder is also the
highest line

on the plant site, rising to an elevation of 450

above
the reference valley elevation.

Overhead lines that are longer and
to
which
more
substations
and
equipment
are
attached
were
also
observed to be less reliable (more exposure to

lightning and more
equipment
to
fail).
The
age
of
the
line
does
not
appear
to

significantly lessen its reliability as long as adequate maintenance is
performed;

none
of
the
lines
have
had
a
notable
increase
in
the
frequency of outages as the lines have aged. As would be expected,
the
empirical
data
presented
in
Table


I
confirms
the
two
overhead
lines
which
have
been
insulated
to
a
higher

level

(34
or 69 KV) have

significantly better reliability records than

those

utilizing
15
kV
class
construction.
Feeder
7
(insulated
to
34
KV)
4

中英文对照外文翻译文献

and feeder 8


(insulated to 69 kV) have bad only 3 outages each
over
their
32
and
23

year
life
spans,
respectively.
These
lines
follow similar terrain and are comparable in length and age to the 15
kV class lines, yet they have a combined failure rate of 0.22 failures
per year versus 4.32 failures per year for the remaining feeders.
On
typical
15
kV
insulated
line
construction,
lightning
flashovers often cause 60 cycle power follow and feeder trip. With
the
higher
insulation

construction,
outage
rates
are
reduced
by
limiting
the
number
of
flashovers

and
the
resultant
power
follow
which causes an over current device to trip.

This allows lightning
arresters
to
perform
their
duty
of
dissipating
lightning
energy
to
earth.
The
number
of
re
closer
actions
and
their
resultant

momentary
outages
are
also
reduced.
This
is
beneficial
for
critical
facilities
and
processes
which
cannot
tolerate
even
momentary
outages.
An


additional
benefit

is
that
outages
due
to
animal
contact
are
also
reduced

because
of
the
greater
distance
from
phase
conductor
to
ground
on
pole
structures.

Distribution
line
equipment to increase line insulation values are
and
proven
technology.
New
lightning
resistant

construction
typical by utilizes horizontal line posts, fiberglass standoff brackets
5

中英文对照外文翻译文献

or
any
other
method

which
world
increase
the
insulation
value.

The replacement of standard pin insulators with line post insulators
of
greater


flashover
value
is
an
effective
means
to
retrofit
existing wood cross arm construction. The doubling and tripling of
dead end and suspension

insulators

is also a means of increasing
flashover
values
on
existing
angle
and
dead-end

structures.
Current
fiberglass,
polymer,
and
epoxy
technologies
provide
an
affordable means to increase line insulation.
While the use of increased insulation levels to reduce lightning
flashovers

and the resultant outages on overhead distribution lines
has
been

thoroughly
tested
and
demonstrated
in
laboratory
and
experimental
tests
[5],
long
term
history
field
data
has
positively
demonstrated
that
the
use
of

resistant
construction
can
greatly reduce outages. Field use at ORNL has shown that in areas
which
are
vulnerable
to
lightning,
the
use
of
increased
insulation
and
a
smaller
shielding
angle
is
an
impressive
and
cost
effective

means
to
appreciably
increase
the
reliability
of
overhead
distribution lines.


This reliability study clearly illustrates that the
insulation
requirements
for

high-reliability
distribution
feeders
should be determined not by the 60 Hz operating voltage but rather
6