The Morris County chronicle. [volume] (Morristown, N.J.) 1877-1915, 1905-08-29

- We attentioh u iueS' W.
reports Of committees hav-
%C2% ing been made public. The
FIRST gives the results of the lightning
research committee, which was organ
azed some years ago by. the. Royal Instia
tate .of British Architects and the Sur
veyors' Association, which deals prin-
cipaliy- with the proteetIonsof buildings.
,The second was presented at the re-
cent meeting of the National Electric
Light Association, i'll Denver by Alex
Dow. and deals with the protection
of electrical systems from lightning.
In neither report says the Electrical
Review, sis there any particularly
ssovel suggestion, nor have the fnvesti-
CATIONS brought to light any new phe-
nomena Previous recommendations
nre upheld by the new evidence secured
Ivy the members of the committees.
The report of the British research
committee is preceded by an introduce
tion prepared by Sir Oliver Lodge,
member Of this committee. In this in
PRODUCTION he considers two types Of
lightning stroke. The first, termed
~ him the A stroke. is one in which
direct discharge takes place from q
charged cloud to the earth. This dis
eliarge is not particularly dangerous.
\ Co protect buildingssfrom it, lightning
rods are useful. The points OF the rods
rnay indeed prevent a violent discharge
s'y assisting in equalizing the potentials
Of the cloud and the earth. Lightning
rods, to be effective, must, however.
be installed properly They should
offer path of least resistance for the
discharge, yet the resistance of this
path must not be too small. II the rod
does not form the path of least resist
ance, the discharge may leave it and
find its way to ground through neigh
boring materials. On the other hand, If
the resistance of the rod be too low,
the discharge takes place through it too
rapidly almost explosively- is LA
bic to set up induced or secondary dis
charges in neighboring conductors.
The rod should be carried to the ground
with as few bends as possible. Iron
is better material than copper, pro-
yided atmospheric conditions are not
such as to rust it away too quickly.
sThe other, or B type of stroke, as it
is called, occurs when an unchanged
cloud intervenes between the earth and
the charged cloud. This intervening
cloud acts with the charged cloud as an
electrical condenser, and when dis
charge takes place Between them, the
charge upon the upper surface is neu-
tralized, and that on the lower surface
suddenly set free, and consequently
throws a sudden strain in the dielec-
trio between the cloud and the earth,
with the result that if a discharge
takes place, it is apt to follow an err
ratio path. The effect Of such strokes
is more serious than that of an A
stroke. and lightning rods offer but
slight protection. The only way to
iprotect the building from such strokes
lis to surround it by cage of metal.
1T is suggested that powder magazines
lie protected by complete metallic
,sheathing; but even metallic cage
docs not guarantee building against
lightning.
Lightning will sometimes prefer to
and its way to ground through the hot
gases of tall chimney, rather than
through the rod provided for it. 1t is
suggested that this might be prevented
l,y raising a number of rods well above
the top of the chimney, connecting
them to the ground through vertical
wires. 1t is recommended that all me-
fallic parts of building be, connected
to good grounds; and although there
is no record of damage to tall steel
frame structures. it would be desirable
10 provide a better earthlng connec-
ton; than that usually obtained through
the concrete foundation. The report
suggests that the usual method of
grounding conductors by means OF
aarge plates should be abandoned in
favor of a ground obtained through a
perforated steel spike driven into moist
ground, and filed with granulated
charcoal (not cokel.
"The problem presented to electrical
engineers is in some ways even more
troublesome than the protection of
buildings from lightning, for in addi-
fion to providing a path for the dis
charge to ground, the lightning ar
roster must prevent the line current
from following along the path taken
by the lightning. In addition. light
ming arresters used on electrical sys-l
TENS are frequently depended upon to
protect the system from damage due
to an unexpected happening taking
place on its own lines. A short-circuit
on transmission Line, or sudden
throwing of of large load, may set
up electrical oscillations which will
cause an excessive rise Of voltage, with
danger of breaking down the insulation
Of the electrical machinery. If the
lightning arrester be adjusted so as
10 allow a discharge to take place If
the voltage not only from the lines to
the ground, but between the. lines
themselves, rises above a certain point,
It will act as safeguard. The engi-
neer of transmission system does not
fear a direct stroke Of lightning as
much as induced or secondary strokes,
or excessive potential due to a static
charge. A direct stroke will frequently
and its way = GROUND through the
poles, rather than pass back TO the
station over the line The pole may be
go 4fawad h,rf tha SrStpn1 ofhprxvfen