An apparatus for measuring the intensity of current produced in an elongated electrical conductive member by a lightning strike for determining the intensity of the lightning strike is presented. The apparatus includes an elongated strip of magnetic material that is carried within an elongated tubular housing. A predetermined electrical signal is recorded along the length of said elongated strip of magnetic material. One end of the magnetic material is positioned closely adjacent to the electrically conductive member so that the magnetic field produced by current flowing through said electrically conductive member disturbs a portion of the recorded electrical signal directly proportional to the intensity of the lightning strike

Livermore, S. F.

English

NASA Technical Reports Server

United States Patent [191 
Livermore 
[54] LIGHTING CURRENT IIETECI'OR 
[75] Inventor: Stephen F. Livermore, Satellite 
Beach, Fla. 
[73] Assignee: The United States of America as 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
[21] Appl. No.: 835,544 
[22] Filed: Sep. 22,1977 
[51] Int. c1.2 ............................................. GOlR 31/02 
[52] U.S. Cl. ...................................... 33/73 324/102; 
324/112: 324/113; 324/133 
[58] Field of Search ............... 324/102, 112, 113, 133, 
324/72; 340/253 P 
[561 References Cited 
U.S. PATENT DOCUMENTS 
2,870,407 1/1959 Baker ................................... 324/102 
[111 4,112,357 
[451 Sep. 5,1978 
Primary Examiner-M. Tokar 
Arrorney, Agenr, or Firm-James 0. Harrell; John R. 
Manning 
P I  ABSTRACT 
An apparatus for measuring the intensity of current 
produced in an elongated electrical conductive member 
by a lightning strike for determining the intensity of the 
lightning strike. The apparatus includes an elongated 
strip of magnetic material that is carried within an elon- 
gated tubular housing. A predetermined electrical sig- 
nal is recorded along the length of said elongated strip 
of magnetic material. One end of the magnetic material 
is positioned closely adjacent the electrically conduc- 
tive member so that the magnetic field produced by 
current flowing through said electrically conductive 
member disturbs a portion of the recorded electrical 
signal directly proportional to the intensity of the light- 
ning strike. 
7 Claims, 4 Drawing Figures 
https://ntrs.nasa.gov/search.jsp?R=19790006134 2020-03-20T17:53:39+00:00Z
U.S. Patent Sept 5 ,  1978 4,112,357 
3 0  
1 
LIGHTING CURRENT DETECTOR 
4,112,357 
ORIGIN OF THE INVENTION 
The invention described herein was made by an em- 
ployee of the United States Government and may be 
manufactured and used by or for the Government or for 
governmental purposes without the payment of any 
royalties thereon or therefor. 
BACKGROUND OF THE INVENTION 
The present invention relates to a device for monitor- 
ing electrical strikes and, more particularly, to a device 
which will produce a disturbed magnetic signal directly 
proportional to the maximum intensity of the lightning 
strike. 
Heretofore, magnetic links were used in monitoring 
the intensity of lightning strikes and for recording the 
maximum current amplitudes produced thereby in elec- 
trically conductive members. The magnetic links are 
relatively small links of cobalt steel having a high mag- 
netic retentivity that are magnetically polarized when 
current passes close thereto. These links are then taken 
to a laboratory and the degree of magnetization is mea- 
sured for determining the maximum current that passes 
thereby. 
One of the problems encountered in utilizing such 
magnetic links is that when two or more strokes of 
lightning of reverse polarities struck the tower, the 
residual magnetism produced in the magnetic links 
would effectively cancel out and indicate a current 
reading close to zero. 
Another problem encountered in utilizing such mag- 
netic links is that high currents from strong lightning 
strikes would often saturate the magnetic links and pro- 
vide an inaccurate measurement of the true maximum 
current. 
Another disadvantage in using the magnetic links is 
that they must be removed and taken to a laboratory for 
analysis in order to determine the maximum current 
produced by the lightning strikes. 
In U.S. Pat. No. 3,889,185 entitled “Lightning Cur- 
rent Measuring System,” there is disclosed a system for 
monitoring and analyzing electrical currents produced 
by lightning strikes. This apparatus includes an electri- 
cally conductive mass having a first circuit coupled 
thereto for generating a D.C. voltage proportion to a 
peak current generated in the mast by each lightning 
strike. A second circuit is couded to the mast for zener- 
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45 
ating a digital signal representhe of the wave shipe of 50 
the current generated in the mast by each lightning 
strike and a third circuit is provided closely adjacent the 
mast for producing a reference voltage. Signals are fed 
into a strip chart recorder making a permanent record 
of the current produced by the lightning strike. Loop 
antennae are often utilized for determining the distance 
to a lightning strike from a particular station, and an 
example of such a device is disclosed in U.S. Pat. No. 
3,715,660. 
SUMMARY OF THE INVENTION 
The invention includes an apparatus for measuring 
the intensity of the current produced in an elongated 
electically conductive member by a lightning strike. By 
measuring the current flowing through an electrically 
conductive member, the maximum intensity of the light- 
ning strike can be determined. The apparatus includes 
an elongated strip of magnetic material that is carried 
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65 
2 
within a tubular housing. The tubular housing is 
mounted perpendicular to the electrically conductive 
member. The elongated strip of magnetic material has a 
predetermined electrical signal recorded along the 
length thereof. One end of the magnetic material is 
positioned closely adjacent the electrically conductive 
member so that the magnetic field produced by the 
current flowing through the electrically conductive 
member disturbs this prerecorded electrical signal a 
distance from the mast directly proportional to the 
intensity of the lightning strike. 
By analyzing the disturbance of the predetermined, 
recorded electrical signal and comparing this distur- 
bance with known charts, the intensity of the lightning 
strike can be determined. 
Accordingly, it is an object of the present invention 
to provide a simple and inexpensive device for monitor- 
ing the maximum intensity of lightning strikes. 
Another important object of the present invention is 
to provide an apparatus for measuring the intensity of 
lightning strikes which is relatively safe in operation 
and requires inexpensive components. 
Still another important object of the present inven- 
tion is to provide an apparatus for measuring the maxi- 
mum intensity of lightning strikes which utilizes equip- 
ment which is not normally damaged by the high cur- 
rents and voltages generated by the lightning strike. 
These and other objects and advantages of the inven- 
tion will become apparent upon reference to the follow- 
ing specification, attendant claims, and drawings. 
BRIEF DESCRIPTION O F  THE DRAWING 
FIG. 1 is a perspective view illustrating a tower hav- 
ing guide wires extending downwardly from the top on 
which a lightning monitoring apparatus constructed in 
accordance with the present invention is attached. 
FIG. 2 is an enlarged elevational view illustrating a 
lightning current detector constructed in accordance 
with the present invention. 
FIG. 3 is a plane view illustrating a tube forming part 
of the lightning current detector. 
FIG. 4 is a perspective view illustrating a magnetic 
recording strip mounted on a plexiglass strip that is 
carried within the tube as illustrated in FIG. 3. 
DESCRIPTION OF THE PREFERRED 
EMBODIMENT 
The lightning current detector as shown in FIGS. 1 
and 2 and generally referred to by the reference charac- 
ter 10 is a passive device which consists of a strip of 
magnetic tape 12 with a pre-recorded signal mounted in 
a weather protective tube 14 perpendicular to a ground 
conductor 16 of a tower 18. The lightning current de- 
tector is mounted to the outer guide wire ground cable 
16 for recording the peak value of the lightning currents 
flowing through these paths. A current sensing coil 20 
which has a flashbulb 22 is also mounted on the ground 
cable 16 for producing a visual indication of a lightning 
strike to the tower. The voltage induced in the coil 20 
by a lightning strike causes the flashbulb 22 to be ener- 
gized. Upon observing the flashbulb 22 flashing or ob- 
serving that it had previously flashed by burning out, an 
indication is produced that lightning has caused a cur- 
rent to flow through the guide wire 16. 
The lightning current detector includes a tubular 
housing 14 which has a plastic cap 24 secured to an 
inner end thereof. A rubber stopper 26 is inserted in the 
other end of the tubular member 14 for providing a 
3 
4,112,357 
sealed tubular housing. A plexiglass brace 28 is used for 
connecting the tubular housing 14 to the ground cable 
16. Normally, non-conductive connectors 30 are used 
for securing the tubular member 14 to the plexiglass 
brace and for securing the plexiglass plate to the ground 
cable 16. The tubular member 14 is mounted perpendic- 
ular to the ground cable 16 with the plastic cap 24 being 
flush against the cable 16. 
Carried within the tubular member 14 is an elongated 
strip of magnetic material 12 that is in the form of an 
endless belt. An electrical signal indicated by the line 34 
is recorded along the length of the belt 12 on opposite 
sides thereof. In one particular application, an 8 khz 
reference signal was recorded on the magnetic tape 12. 
This reference signal, as illustrated in FIG. 4, is re- 
corded along the length of the magnetic tape 12. A 
plexiglass member 32 is inserted within the tubular 
housing 14 for holding the magnetic tape 12 in an ex- 
tended position. The plexiglass member with the mag- 
4 
What is claimed is: 
1. An apparatus for measuring the intensity of a cur- 
rent produced in an elongated electrical conductive 
member by a lightning strike for determining the inten- 
5 sity of said lightning strike, said apparatus comprising: 
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15 
netic beit 12 positioned thereon is positioned within the 20 
tubular member 14 with the inner end thereof flush 
against the cap 24. 
The principal of operation of the current detector is 
that when lightning current travels down a current 
carrying conductor such as the ground conductor 16, a 25 
magnetic field is produced which will erase a portion of 
(a) an elongated strip of magnetic  material, 
@) means for holding said elongated strip of magnetic 
material perpendicular to said elongated electrical 
conductive member, 
(c) a predetermined electrical signal recorded along 
the length of said elongated strip of magnetic mate- 
rial, 
(d) one end of said magnetic material being positioned 
closely adjacent said electrical conductive member 
with the magnetic material extending perpendicu- 
larly outward from said electrically conductive 
member a greater distance than the distance of a 
magnetic field that is produced by current induced 
in said conductive member caused by an antici- 
pated lightning strike, 
whereby by analyzing the distance that said re- 
corded signal is disturbed from said one end of 
said magnetic material by the magnetic field, the 
intensity of said lightning strike can be deter- 
mined. 
2. The apparatus as set forth in claim 1 further com- 
therecorded signal 34 on the magnetic tape 12 closest to 
the conductor 16. The distance away from the conduc- 
tor that the signal is erased is dependent upon the 
strength of the magnetic field around the conductor. 30 
The greater the peak value of the current flowing 
through the conductor 16 the greater the magnetic field 
produced. For an infinitely long straight conductor, the 
magnetic field strength, H, at any point away from the 
conductor is dependent solely upon the peak value of 35 
the current and the radial distance away from the con- 
ductor to the point. H = I/2nr with r being the distance 
from the conductor 16. 
The lightning current detector provides a measure- 
ment of the maximum peak current of the lightning 40 
flash. It does not have the capability of distinguishing 
between the various strokes of the flash, the number of 
strokes, or the corresponding rise time or duration of 
the individual strokes in the lightning flash. Since the 
initial stroke of the flash usually generates the highest 45 prising: 
peak current, subsequent strokes should not affect any 
more of the recorded signal still left on the tape 12 since 
the corresponding magnetic fields are of a lesser inten- 
sity than the magnetic field from the initial stroke. The 
overlapping of successively smaller magnetic fields on 50 
the tape will reinforce that portion of the tape that was 
already erased from the magnetic field produced by the 
first stroke. prising: 
By analyzing the length of the pre-recorded signal 34 
that has been erased by the magnetic field and compar- 55 
ing this distance with known test data utilizing known 
currents, the intensity of the lightning stroke and the 
current flowing through the guide wire 16 can be deter- 
mined. 
the disturbed pre-recorded signal 34 on the tape 12. In 
one particular device, a conventional tape recorder is 
utilized for reading the signal off of the tape 12. 
While a preferred embodiment of the invention has 
been described using specific terms, such description is 65 
for illustrative purposes only, and it is to be understood 
that changes and variations may be made without de- 
parting from the spirit or scope of the following claims. 
prising: 
(a) an elongated tubular housing, carried perpendicu- 
(b) said elongated strip of magnetic material being 
3. The apparatus as set forth in claim 2 further com- 
(a) a non-conductive elongated member carried in 
(b) said magnetic material extending along the length 
4. The apparatus as set forth in claim 4 wherein: 
(a) said magnetic material is in the form of an elon- 
gated endless loop, 
(b) said loop of magnetic material extending around 
said non-conductive elongated member along a 
longitudinal axis. 
5. The apparatus as set forth in claim 2 further com- 
(a) a non-conductive brace, 
(b) nieans for attaching said non-conductive brace to 
said electrical conductive member, and 
(c) means for attaching said tubular housing to said 
non-conductive brace perpendicular to said electri- 
cally conductive member. 
6. The apparatus as set forth in claim 2 further com- 
(a) removable caps carried on the ends of said tubular 
housing for sealing said housing and providing 
access to said elongated strip of magnetic material. 
7. An apparatus for measuring the intensity of a cur- 
rent produced in an elongated electrically conductive 
member by a lightning strike, comprising: 
lar to said electrical conductive member, 
carried in said tubular housing. 
prising: 
said housing, 
of said non-conductive member. 
Many suitable devices can be utilized for analyzing 60 (a) an elongated, non-conductive member, 
(b) an elongated, magnetic strip extending on oppo- 
site sides of said elongated, non-conductive mem- 
ber, 
(c) an elongated tubular housing enclosing said non- 
conductive member with said elongated strip of 
(d) means for mounting said tubular housing perpen- 
dicular to said electrically conductive member, 
. magnetic material positioned thereon, 
5 
4,112,357 
6 
(e) a predetermined electrical signal recorded along 
the length of said elongated strip of magnetic mate- 
rial, 
(f) said elongated strip of magnetic material extending 
outwardly from adjacent said electrical conductive 
member a distance greater than the distance of a 
in said conductive member caused by an antici- 
pated lightning strike, 
whereby by analyzing the distance that said re- 
corded signal is disturbed from said end of said 
magnetic strip adjacent said electrically conduc- 
tive member by the magnetic field, the intensity 
of said lightning strike can be determined. 
magnetic field that is produced by current induced I + + + .  
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UNITED STATES PATENT OFFICE 
CERTIFICATE OF CORRECTION 
PATENT NO. 4,112,357 
DATED September 5, 1978 
INVENTOK(S) Stephen F. Livemore 
are hereby corrected as shown below 
It IS  cert i f ied that error appears in the above-identified patent and that sald Let ters  Patent 
Introductory Page - I' [541 LIGHTING CURRENT DETECTOR" 
should read - - [54] LIGHTNING CURRENT DETECTOR-- 
"LIGHTING CURRENT DETECTOR" should read 
column 1, line 2 
--LIGHTNING CURRENT DETECTOR-- 
Signed and 5caled this 
Attest: 
DONALD W. BANNER 
Conurrissiour of Patears ul Tm&mw& 
RUTH C. MASON 
Attesting Oflccrr 
i 


Lightning current detector

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