II
I
,
r
I
r
.
.
~~~~~~~~~~~~factors
which
affect
design
and
economy
mp
u
Ise
a
na
60-
tyc
e
tna
racteristics
of
installation,
but
these
need
not
be
gone
into
at
this
time.
An
immediate
funda-
o
f
Driven
G
ro
un
n
s
mental need
is
for
impulse
data
on
actual
driven
grounds,
under
impulse
currents
well
approaching
lightning
conditions.
P.
L.
BELLASCHI
The
results
of
the
investigation
presented
FELLOW
AIEE
in
this
paper
should
therefore
be
timely
and
helpful
to
the
art
of
lightning
protec-
tion.
I.
Introduction
testing.
And
from
the
measured
60-
cycle
values
plus
what
experience
would
II.
Test
Axrangement
DRIVEN
grounds
are
important
in
ensue
there
have
been
established
present
electric
power
transmission
and
practices.
The
Sharon
High-Voltage
Laboratory
distribution.
In
fact,
they
comprise
one
It
is
a
fact
that
the
60-cycle
methods
is
located
in
the
open.
This
is
a
favor-
of
the
essential
elements
in
the
art
of
of
measurement
have
the
great
merit
of
able
circumstance
that
has
facilitated
lightning
protection.
Yet,
to
this
day,
simplicity56
and
it
is
conceded
that
ex-
the
investigation,
for
the
grounds
can
be
the
value
of
protection
derived
from
perience
can
often
rationalize
methods
driven
in
the
natural
soil
within
easy
grounds
under
actual
operating
conditions
of
evaluating
performance
that
are
not
reach
of
a
well-equipped
impulse
labora-
of
lightning
discharge
is
difficult
to
state
altogether
fundamental.
Yet
the
need
tory.
The
arrangement
that
was
used
is
in
full
quantitative
measure.
And
the
of
establishing
the
performance
of
grounds
shown
in
figure
1.
reason
for
this
situation
lies
partly
in
the
under
the
actual
service
conditions
of
T'he
impulse
generator
and
the
instru-
lack
of
fundamental
knowledge
of
the
im-
lightning
discharge
has
long
been
recog-
ments
are
grounded
to
the
common,
low-
pulse
characteristics
of
driven
grounds.
nized.
In
this
connection,
the
tests
by
resistance
grid
of
the
laboratory,
which
In
part,
the
difficulty
also
is
due
to
the
H.
W.
Towne7
in
1928
and
more
recently
measured
with
the
megger
0.9
ohm
to
complex
factors
that
inherently
make
up
an
investigation
by
H.
Norinder8
has
earth.
The
voltages
of
the
driven
driven
grounds
and
ground
systems.
contributed
to
point
out
the
significance
grounds
were
recorded
at
the
cathode-ray
A
comprehensive
survey
of
principles
of
the
impulse
characteristics
of
driven
oscillograph
through
a
voltage
divider.
and
methods
on
driven
grounds
was
is-
grounds-even
though
both
investiga-
Likewise
the
impulse
currents
discharged
sued
in
1918
by
the
Bureau
of
Standards.'
tions
are
somewhat
limited
in
scope
con-
through
the
driven
grounds
were
meas-
Further
contributions
have
appeared
sidering
the
extent
and
practical
impor-
ured
at
the
oscillograph,
by
means
of
a
since,
some
presenting
new
developments
tance
of
the
subject.
suitable
shunt
inserted
in
the
grounded
and
findings,2
others
dealing
on
theoreti-
Those
versed
in
the
art
know
that the
end
of
the
impulse
generator.
The
tech-
cal
aspects
of
the
problem,3
and
a
third
impulse
resistance
of
a
driven
ground
is
nique
of
testing
and
measurement
com-
group
bearing
on
related
questions.4
In
below
the
corresponding
megger
or
60-
plies
essentially
with
the
recognized
meth-
recent
years,
progress
has
been
centered
cycle
measured
values.
The
practice
ods
described
in
AIEE
Standards
No.
on
the
immediate
field
of
application.
usually
followed,
to
consider
the
megger
4
(1940)
and
in
the
literature.
Other
de-
Here
the
emphasis
has
been
to
obtain
ef-
values
as
a
basis
for
design,
is
also
a
rec-
tails
on
the
test
arrangement
will
be
ap-
fective
service
with
such
methods
of
ognition
of
this
fact.
There
are
other
parent
from
figure
1
and
the
following.
grounding
as
lend
themselves
particu-
larly
to
economical
installation.
For
in-
(PROPERTY
LIMIT)
III.
Physical
Characteristics
of
stance,
a
common
practice
with
some
(FIELD)
Driven
Grounds
utilities
nowadays
is
to
drive
rods
to
con-
siderable
depths,
even
down
to
bedrock,
8-FT
EMBANKMENT
Four
one-inch
diameter
steel
rods,
so
as
to
attain
the
lowest
measurable
re-
(FIELD)
D
c
'E
designated
as
A,
B,
C,
and
D
in
figures
1
sistance.
A
recognized
practice
for
se-
DRIVEN-;
A
LABORATORY
GROUND
and
2,
were
driven
in
the
natural
soil
out-
curing
low-resistance
grounds
is
also
to
GROUNDS
*
I/CS
ITaMside
the
laboratory
in
1933.
They
have
place
a
sufficient
number
of
electrodes
in
-
-
been
in
the
soil
ever
since.
Two
of
the
parallel
(multiple
grounds).
Still
another
L
IMPULSE
rods
were
driven
nine
feet
in
the
earth,
I
~~GENER-
expedient
is
that
of
reducing
the
resis-
V.D.
TOR
the
other
two
struck
rocks
at
seven
and
tivity
of
the
soil
immediately
surrounding
C
one-half
feet
and
could
not
be
driven
the
electrode
by
suitable
treatment
with
HIGH
deeper.
Early
in
1940,
after
this
investi-
common
salt
(NaCl)
or
other
conducting
VFED
C
VOLTAGE
gation,
two
of
the
rod
wereremoved
for
solutin.
Al
thes
develpment
have
(FIELD)
LABORATORY
oo
h
oswr
eoe
o
solution.
All
these
developments
have
F
CRQ
u
inspection.
There
was
no
evidence
of
been
based
largely
either
on
60-cycle
0
OSCILLATN
rusting
of
the
metal
at
the
surface
in
values
or
on
closely
similar
methods
of
ROOM
°
(YARD)
contact
with
the
soil.
~~~
~~The
soil
of
the
grounds
is
a
combination
Paper
41-5,
recommended
by
the
AIEE
committee
SURGE
LEAD
STATION
of
shale
and
clay
with
a
mixture
of
gravel
on
power
transmission
and
distribution
and
pre-
WOOD
POLE
30
FT
INSULATOR
sented
at
the
AIEE
winter
convention,
Phila-ansnd
Thert1Somly
ot
delphia,
Pa.,
January
27-31,
1941.
Manuscript
Figure
1.
Test
arrangement
in
this
location.
The
physical
nature
of
submitted
September
9,
1940;
made
available
for
preprinting
October
25,
1940.
CR0-Cathode-ray
osciliograph
the
soil
became
more
apparent
from
te
P.
L.
BELLASCH5
is
section
engineer,
transforner
VM-Voltage
measurement
examination
of
a
six-foot
diameter
ten-
engineering
department,
Westinghouse
Elect-ric
VD-Voltage
divider
foot
deep
hole
that
was
dug
in-May
1940
CM
-Current
measurement
near
the
laboratory
at
about
25
feet
from
1.
For
all
numbered
references,
see
list
at
end
ofCSCretsuthelcioofhegun.Frt,ev
paper.
:-C
urn
hn
felcto
ftegons
is,sv
MARICH
1941,
VOL.
60-
Bellaschi-Charazcteristics
of
Driven
Grounds
TRANSACTIONS
123
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