THREE DOLLARS A YEAR THIRTY CENTS A COPY - 

GENERAL ELECTRIC 

e 

VOL. 34, NO. 4 APRIL, 1931 

ELECTRIC HEAT 

in its program of modernlzatlon, Industry IS avalllng ltself not only of the latest advances in electric power and light but also 

in that newer branch of electr~c service--electric heat. The rapid growth in the utilization of electric heat 1s indicated 

by a consumption of 6,000,000,000 kw-hr. for this purpose in 1929, which is more than double that of 1925. In the 

above photograph are shown two 50-ton 1100-kw. pit-type furnaces for annealing bar stock 25 ft. long 

In This Issue: @ghtni% Measuring Instruments Thyrite Arrester Field Tests 

Aircraft Compasses Coal Handling Xodernization Rectifier Auxiliaries ~ 

High-speed Oscillograph Timing Vector Diagrams Medium Voltage Networks 
1 = r 

- instruments for Lightning Measurements C7 u 

Latest Developments and Applications of Surge-voltage Recorders-Cathode-ray OscillographsLightning-stroke Recorders-Surge Indicators-Lightning-severity Meter 

By C. M. FOUST 

General Engineering Laboratory, General Electric Company 

C ONSTANTLY increasing demands for uninterrupted service on transmission lines has 

focussed attention upon the most disturbing 

factor-lightning. The problem simply stated is : 

"How may transmission lines and protective equipment be arranged to avoid tripouts and loss of power 

due to lightning flashover of the line insulation?" 

Progress toward the solution of this problem has until 

recent years been greatly hindered through lack of 

sultable measuring instruments. For a iong time, 

sphere gaps and needle gaps were the only measuring 

devices of practical importance for such purposes and 

these devices have obvious limitations which narrowed 

their usefulness on actual power lines. Within the past 

few years, however, intensified effort has resulted in 

the design and application of various surge-measuring instruments, through the use of which a great 

amount of engineering information concerning lightning surges has been gathered. Present progress justifies the belief that the continued use of these devices 

will result in a solution to the lightning problem. 

Classification of Instruments 

Surge-measuring instruments suitable for lightning 

surges must record within microseconds (millionths 

of a second) and must be of such nature that automatic registration is obtained. The uncertainty of the 

time of occurrence of electrical storms and lightning 

strokes necessitates instruments that are ever in 

readiness for operation. The short time elements 

involved militate against the use of movable parts in 

the instruments; and the devices described in this 

article will therefore depend for their operation upon 

rather unusual electrical principles. 

For the purpose of presenting a summary of the 

present available instrur~ie~iis, Table I has been 

arranged. 

Surge-voltage Recorder 

The surge-voltage recorder is built in both the 

moving-film and stationary-film type of instrument. 

Both types utilize the Lichtenberg figure method of 

registration of crest surge voltage and their voltagefigure size calibrations are the same. The instruments 

are single phase and are equipped with direct and 

reversed-polarity electrodes connected in parallel. 

This arrangement permits the registration of each 

surge voltage regardless of polarity with both a positive and negative Lichtenberg figure. 

The measuring range of the instrument is 3 to 30 

kv., giving a ten-to-one ratio between the highest point 

on the calibration scale and the initial registration 

TABLE I 

Name of 

Instrument 

Surge-voltage recorder 

(moving-film type) 

Surge-voltage recorder 

(stationary-film type) 

Cathode-ray 

. oscillograph 

Lightning-stroke 

recorder 

Surge indicator 

Lightning-severity 

meter 

Quantity 

Measured 

Crest voltage 

Crest voltage 

Wave shape and 

amplitude 

Indicates direct 

stroke to tower 

Indicates insulator 

flashover 

Integrates field 

intensities at time 

of lightning strokes 

Method of 

Connection 

Capacitance 

coupling 

Capacitance 

coupling 

Capacitance 

coupling 

S'nunted across tower or ground 

wire 

Shunted across to.wer or ground 

wlre 

Small antenna 

Method of 

Registration 

Lichtenberg figures on photographic 

film 

Lichtenberg figures on photographic 

film 

Cathode-ray on photographic film 

on photographic 

film 

Disruptive link 

trips target 

Glow tube 

illumination on photographic film 

Direct 1 

Instrument 

Range Time Scale 

(Kilovolts) 

3-30' I % in. per hr. 

None 

2 and above I 

0-l* 

None 

None 

Microseconds 

(millionths of a set- 

* By the use of a suitable voltage divider, the measurement range of these instruments can oi course be extended upward ior a transmission line of 

any voltage. Three million volts have been measured. 

, 0"" ?I:" n 3-Y.3 ol I hT^,, 

I 
236 April, 1931 GENERAL ELECTRIC REVIEW VO!. 34, Nc. 4 

voltage. The use of the double-registration feature has 

great advantages for the following reasons: 

(1). Because negative surge voltages up to 

approximately 2.5 times normal give negative 

Lichtenberg figures upon a directly connected 

recorder and on such a recorder are entirely obscured by the norma1,line voltage band. 

Surge-voltage Recorder (Moving-film Type) 

The moving-film type. of surge-voltage recorder is 

shown in Figs. 1 and 2. An earlier design has been 

previously described. (I) The present instrument has 

been improved in two respects, first in the design of 

the enclosing box and second in the method of time 

registration. The insulating box has been rearranged 

to provide a fixed compartment for the clock mechanism and a hinged cover for the photographic-film 

compartment. The advantages obtained are protection to the clock and definite alignment of the hinged 

cover. 

The voltage-figure size calibration is shown in 

Fig. 3. This calibration holds for both the movingFig. 1. Surge-voltage Recorder of the Moving-film Type, 

Shown with the Film and Clock Compartments Open 

(2). Because negative Lichtenberg figure sizes 

are dependent upon the rate of voltage rise to a 

much greater degree than the positive'figures.. 

(3). Because the availability of both figures for 

all high-voltage surges permits more accurate 

determination of the nature of the surge producing 

the figures. 

Fig. 3. Voltage Calibration of Surge-voltage Recorder. 

Showing Relation of Positive Lichtenberg Figure 

Size to Crest Value of Surge Voltage 

Fig. 2. Moving-film Type of Surge-voltage Recorder, 

Shown with the Clock Compartment Open and 

the Film Compartment Closed 

film and stationary-film types of surge-voltage 

recorder. 

A specimen field record from the moving-film type 

of instrument is shown in Fig. 4. It will be noted that 

the time markings are very clearly printed on the 

center of the film and that the serial number of the 

instrument appears above the hour of 12 midnight. 

-, I nls . time marking is accompiished through engraved 

numbers filled with radioactive r~iaieriai on the driving dmm and has been fmsd ta be very satisfactory. 

Edge-light fog which frequently occws due tc! lc!c!se!y 

rolled films will not cover the time scale. Fig. 4 shows 

about ten inches of the seven-foot record obtained for 

each weekly exposure. The clock drives the film j.i in. 

per hour or 1 ft. per day and will drive it satisfactorily 

for eight days. 

(1)"Measurement of Surge Voltages on Transmission Lines Due to Lightning, by E. S. Lee and C. M. Foust. GENERAL ELECTRIC REVIEW. 

March. 1927. pp. 135-145. 
iNSTRUMENTS FOR LIGHTNING iviEASUREiv1Eiu'TS 237 

-. rleid insraiiarions and Records 

n-t-~-- 4- +hA +.~.,:~~l e,.vmo-T,n ltnw0 ,.opn,-a ntxcrrulg agaul IAJ ulrj by ylral OWL 5"- vrvu6v A v,vrv 

in Fig. 4, the black parallel lines below and above the 

timing marks are normal voltage lines on the directly 

connected and reversed recorder respectively and are 

obtained from the normal excitation of the circuit. 

The Lichtenberg figures at about 2:15 a.m. indicate a 

surge voltage of negative and unidirectional polarity, 

,A ,L,..+ +,, +;,,,. nnrmnl Trnlflc,p ThP cmallpr allu auwuc 1.~11 ulruro uvr~r~ul LAUU v vSYYbV. ---- 

figure tc! the right indicates a surge voltage of two 

times normal voltage. Fig. 5 shows a typical installation of the moving-film type of surge-voltage 

recorder with the instrument sheltered in the standard 

metal housing and mounted in the tower structure; 

and Fig. 6 shows an installation with the instrument 

on a ground pole.. 

Fig. 4. Transmission-line Lightning-surge Record Made by a Surge-voltage Recorder of the Moving-film Type 

Fig. 5. Typical Installation of Moving-film Type of Surge-voltage 

Recorder on a Transmission-line Tower 

The connection of the surge-voltage recorder to the 

transmission line is made through a very low capacitance by means of an insulator-string voltage divider 

with grading shields as shown in Fig. 7. If all the 

dimensions are adhered to within reasonable limits, the 

arrangement can be used on lines of various voltage 

ratings by selecting a suitable number of insulator 

units. Table I1 gives values for various line voltages. 

TABLE I1 

I 

Rating of Line Sumber of Voltage 

(Kilovolts. Insulator Units Divider Phase Voltage) Ratlo 

This type of voltage divider has been given a 

thorough trial over several years' operation and has 

been productive of satisfactory results. 
238 April! 1931 GENERAL. ELECTRIC REVIEW IT-1 Y "I. 34, NO. 4 

A thorough study of surge voltages on a transmission line necessitates the installation of a number 

of recorders spaced along the line at intervals of 

a few miles between each. Such an installation will 

furnish a voltage profile such as that shown in 

Fig. 8. From this profile may be calculated an 

in which 

e =voltage in kilovolts at distance s from 01 

Eo = crest voltage at origin of surge 

K =a factor depending on the particular line 

ranging from 0.0004 to 0.00006 

s = distance in miles from origin of surge. 

To Lme 

t 

Fig. 6. Typical Installation of a Surge-voltage Recorder of the Fig. 7. Installation Arrangement of a Moving-film Type of 

Moving-film Type on a Ground Pole Beside a Surge-voltage Recorder and Insulator-string Voltage Divider, 

Transmission-line Tower and the Connections to a Transmission Line and Ground 

2520 

2 540 

2160 T 

I380 + laao n 

$ 1620 .- 5 I440 0 ,O 1260 

loeo 

3 900 

# 720 

--U 540 3 160 

180 

'0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 

Miles 

Fig. 8. Profile of the Crest Surge Voltage as a Lightning Surge Travels Along a Transmission-line Conductor. 

' This profile is plotted from the records =C surge-vdt=ge recorders inj:a::+d aioiip ih= iine 

attenuation curve for the surge as it travels from the 

point of disturbance. 

A great amount of vaiuabie information has been 

gathered with this technique on various systems. The 

analysis of these data has resulted in the development 

of an empirical formula c2) as follows: 

e= 

Eo 

KsEo+ 1 

(?)"Lightning Investigations on Transmission Lines " by W. W. Lewis 

and C. M. Foust. GENERAL ELECTRIC REVIEW. ~arch.'l930, pp. 185-108. 

rigin 

and 

This formula has been checked by applying surges 

from an artificial-lightning generator and the agreement is within the limits of accuracy of the testing 

equipment. 

In addition to attenuation data, valuable information on amplitude of surge voltages and frequency of 

occurrence of surges has also been obtained. (2) Surge 

voltages of 14 times normal crest voltage to ground 

(2400 kv. on 220-kv. line) have been measured but 

these are few in number. At the lower voltage 
INSTRUMENTS FOR LIGHTNING MEASUREMENTS 239 

amplitudes, the mirnbsr of surges inciaeases rapidly. 

At two or three times normal voltage, surges are 

usually as frequent as 100 per lightning season. It 

must be kept in mind, however, that at low amplitudes it is difficult to differentiate between switching 

and lightning surges. 

Surge-voltage Recorder (Stationary-film Type) 

Progress in lightning measurements soon demonstrated that a smaller and lower-cost instrument 

Fig. 9. Surge-voltage Recorder of the 

Stationary-film Type 

entirely eiidosed i~i a porcelain housing which makes a 

thoroughly weatherproof instrument. The supporting 

brackets may be readily bolted to the cross arm of a 

tower and the lower portion of the porcelain housing 

when unlatched swings downward to permit withdrawal of the film box containing the exposed film 

and the insertion of another film box containing an 

unexposed film. 

Each film box has a serial number engraved and 

filled with radio-active material so that the number is 

marked on every film exposed in that recorder. Specimen records of films from this surge-voltage recorder 

are shown in Fig. 11. 

Fig. 10. Stationary-film Type of Surge-voltage Recorder 

with the Porcelain Housing and Film Container Open 

Fig. 11. Highly Damped Oscillatory Surge as Recorded by the Stationary-film 

Type of Surge-voltage Recorder 

designed for use in the same field as the moving-film 

type surge voltage recorder was very desirable. Such 

an instrument is particularly applicable on distribution systems where it is necessary to obtain a 

number of measurements on the same pole or tower 

2nd wherz the available space is 1i11lited. Figs. 9 and 

?G shCnr a stat;Lsfiary-film tjrGe of -,t;rg~--;~ltage recorder designed for use in this field. 

This instrument has the same calibration characteristics as the moving-film type previously described. 

Two circular films four inches in diameter are placed 

one in each side of the insulating film box shown. The 

top film is in contact with the directly connected electrode and the bottom in contact with the reversed 

polarity electrode. As in the moving-film-type recorder, 

positive and negative Lichtenberg figures are obtained 

with each surge voltage applied. The film box is 

For surge-voltage measurements above the range of 

the instrument, a capacitance voltage divider is 

desirable. Fig. 12 shows an arrangement of voltage 

divider and surge-voltage recorder which has a measuring range up to 200 kv. The voltage divider 

consists of two standard he-insuiator units mounted 

on the surge-voltage recorder, tile entire equipment 

beisg supprted sr, the recorder bracket arm. A porcelain protecting cap Is provided for the top insdatm 

unit. This cap insulates the hardware connected to 

the line and therefore makes the entire outfit proof 

against injury to the attendant. 

A number of these instruments have been used 

during the past lightning season on distribution 

systems, and while a great amount of data has not 

as yet been collected the performance of the instrument has been satisfactory. 
240 April, 1931 GENERAL ELECTRIC REVIEW Vol. 34, No. 4 

Cathode-ray Oecillograph The fact that the electrons in the cathode-ray 

Laboratory experience with lightning generators stream can be deflected by voltage applied to small 

early demonstrated that the time element or wave deflection plates simplified the application of the 

shape of the surge had an important bearing on cathode-ray oscillograph to a marked degree. A coninsulation failure. Therefore, in addition to the nection to the transmission conductor through a low 

Fig. 12. Stationary-film Type of Surge-voltage 

Recorder with Capacitance Voltage Divider 

for Measurements up to 200 kv. 

Fig. 13. The 1928 Cathode-ray Oscillograph 

Transmission-line Lightning Laboratory 

Fig. 14. The 1929 Cathode-ray Oscillograph Transmission-line Lightning Laboratory 

measurement of the surge-voltage amplitudes of capacitance obtains ample energy for full-scale 

lightning surges on transmission lines, the determina- deflections; and by using insulators, similar to those 

tion of wave shapes became necessary. The cathode- of the normal line insulation, to serve as this capaciray oscillograph offered the only solution because the tance a thoroughly safe arrangement was obtained 

time elements involved are of the order of micro- without adding hazard to the line service. 

seconds and recording instruments with mechanically Figs. 13, 14, and 15 show cathode-ray oscillograph 

moving parts are too slow to trace such wave shapes. field laboratories for 1928, 1929, and 1930. In 1928 
one Instrr~ment ~2s rrced as sham in Fig. 16, and i= of this arrzngement which ~,rnefit attmtion. Thxmgh 

1929 (Fig. 17) and 1930 (Fig. 18) two instruments the sensitive tripping gaps and circuits provided, the 

were used. The 1930 arrangement includes all progress first oscillograph begins to trace the wave shape 

in equipment and technique resulting from the previ- automatically within to 3/2 microsecond after the 

ous years' experience. For this reason, space will not incoming wave arrives on the transmission line conFig. 15. The 1930 Cathode-ray Oscillograph Transmission-line Lightning Laboratory 

Fig. 16. The Sinale Cathode-ray Oscillograph in the 

Lightning Laboratory of 1928. (See Fig. IS) 

be taken here to describe the 1928 or 1929 arrangements. 

The two oscillographs used in a 1930 lightning 

laboratory, and arranged as in Fig. 18, were connected in accordance with the diagram shown in Fig. 

19. There are several particular operational features 

ductor. This oscillograph 

then proceeds to record the 

lightning surge on a very 

fast time axis (50 microseconds full film width). The 

second oscillograph begins 

to trace the surge within 1 to 

2 microseconds after the first 

instrument is in operation 

and records the remaining 

portion of the lightning surge 

and iater the reflections as 

the surge returns from the 

various points of transition 

along the conductor. Figs. 20 

and 21 are typical examples 

of lightning surges obtained 

by the two-oscillograph 

method. 

Continuous records of all 

lightning surges throughout 

a storm period are of course 

desirable. To make available sufficient films for a 

great number of surges coming in rapid succession, a special film ho!der was 

designed. This holder is shown in Fig. 22. The film 

holding compartment has been enlarged to permit the 

insertion of five 12-exposure roll films thus making 

possible 60 independent exposures. 

Several hundred oscillograms have been obtained 

throughout the period of operation of the equipment. 

Specimens of oscillograms which have added materially to the knowledge of wave shapes of lightning 

surges on transmission lines are shown in Figs. 23(a) 

to 23 (e), inclusive. 

Lightning-stroke Recorder 

Soon after the first measurements of voltage amplitude and wave shape of lightning surges were made, 

it became apparent that an instrument which would 

differentiate beb~ieer, the direct strokes to a transmission tower, ground wire, or conductnr, Br?d the induced surges on a conductor would be of marked 

value. 

This realization resulted in the design of the 

lightning-stroke recorder, which is an adaptation of 

the Lichtenberg figures for this purpose. This instrument is shown in Fig. 24. It consists of a porcelain 

base which is securely fastened to a tower leg by a 

steel clamp, a weatherproof metallic cover, and a 

light-proof film packet. The porcelain base carries 

an electrode which is connected electrically to the 
242 April, 1931 GENERAL ELECTRIC REVIEW Vol. 34, No. 4 

13 TT supporting ciamp and the metallic cover holds an my flashed over. u11certai11 grvu~~d pairvls and cvstiy 

electrode which is connected at a point on the tower climbing examinations have not resulted in accutower leg some 15 to 30 ft. above the instrument rate information concerning the location and number 

location. The film packet is placed between the of insulator assemblies that have been flashed over. 

electrodes. In Fig. 6 a 

lightning-stroke recorder is 

shown mounted on and connected to the near leg of the 

tower. 

A high-current surge 

(50,000 amp. or above), such 

as is associated with a direct 

stroke, gives ample voltage 

across the 15 to 30-ft. sections of tower leg bridged 

by the instrument lead to 

result in a Lichtenberg figure on the photographic 

films in the packet. The 

currents associated with induced surge voltages are 

not of sufficient magnitude 

to result in registrations 

on the instrument. In this 

way the lightning-stroke 

recorder when installed on 

each tower will indicate 

the locations of direct 

strokes and will give an 

approximate value of surge 

current associated with 

each. 

The Lichtenberg figures 

obtained on the films in 

the sealed light-proof packet 

do not have the same 

characteristics as those 

obtained by surge-voltage 

recorders where the electrodes are in direct contact 

with the photographic emulsion. However, laboratory 

tests have shown that close 

study of the lightning-stroke 

recorder films will permit 

the polarity of the recorded 4.- I.- A,.+,...-:-nA 5Ull;t;b LU UG UGlrGlllllllGU. 

The cllf.rent-fir~re size calibration for this instrument 

is shown in Fig. 25, and a 

typical transmission-line 

direct-stroke record is shown 

in Fig. 26. 

Surge Indicator 

Fig. 17. The Two Cathode-ray Oscillographs in the Lightning Laboratory of 1929. (See Fig. 14) 

Fig. 18. The Two Cathode-ray Oscillographs in the Lightning Laboratory of 1930. (See Fig. 16) 

To remedy this situation, a program of study and 

Transmission lightning studies have emphasized the test of several types of suggested devices was camed 

need for a device which would give an immediate indi- out. As a result of this work, a surge indicator 

cation visible from thegroundwhen aninsulator assem- suitable for use as an indicator of flashovers on a 
INSTRUMENTS FOR LIGHTNING MEASURE_M_ENTS VA~ 

'd L" 

Fig. 23(a). First Cathode-ray Oscillogram of Lightning Surge on a Transmission Line. Taken at Wallenpaupack July 27 1928 on phase Y. The superimposed oscillations are due io flasho;er on' an adja- cent phase 

Fig. 19. Connection Diagram for the Automatic Operation 

of the Two Cathode-ray Oscillographs in the 

Transmission-line Lightning Laboratory 

Fig. 23(b). Cathode-ray Oscillogram Obtained on May 29.1929. Deadend protective gaps at this point flashed over on all three phases. This 

flashover caused a sharp change in voltage from 1260 kv. negative to 310 kv. positive in one microsecond. Flashover took place on the 

front of the wave 

Fig. .20. Cathode-ray Oscillogram of the Voltage Variations 

During the First 50 Microseconds of a Lightning 

Surge on a High-voltage Transmission Line 

Fig. 23(c). Cathode-ray Oscillogram Taken on June 19. 1929. Record 

obtained while line was not enernized. Voltane was still rising at the 

end of 36 microseconds and was then sudaenly reduced co zero. Subsequent examination of line insulation indicated a flashover 23 

miles away, whlch appeared to correlate with this osc~llogram 

Fig. 21. Oscillogram of the Voltage Variations During a 

'2200-Microsecond Period of a Lightning Surge on a 

High-voltage Transmission Line 

Fig. 22. Special 60-exposure Film Holder for 

Cathode-ray Oscillograph 

Fig. 23(d). Cathode-ray Oscillogram Taken on July 19, 1929. This is a wave which has a sl~ghtly oscillatory nature and is typical of a large 

group of waves. A cloud-to-ground stroke was seen at the instant 

this oscillogram was obtained. This stroke was at least 10 miles distant 

from the laboratory and some distance from the line 

Fig. 23(e). Cathode-ray Oscillogram Taken on July 24. 1930. The 

lightning stroke was within one tower span from the lightning laboratory 

Fig. 23. Notable Cathode-ray Oscillograms 
transmission-line insulator assembly was conceived and 

designed. This instrument is shown in Figs. 27 and 28. 

It consists of a weatherproof metal housing 8 in. in 

diameter and 295 in. thick, an indicating target, a 

frangible trip link, and a lead-in insulator. Fig. 27 

(usually the tower arm) which carries the flashover 

current from a particular insulator assembly. Fig. 29 

shows the location of the instrument and connecting 

lead for a transmission line of horizontal configuration 

and Fig. 30 for one of vertical configuration of conFig. 24. Lightning-stroke Recorder Open to 

Show the Film Packet 

Rad~Lx a/ Par,f;rc F,pm - M#Ntmeftrs 

Fig. 25. Calibration Curve of the Lichtenberg 

FigureSize and Tower Surge Current for the 

Lightaiag-stroke Xecorder 

Fig. 27. Surge Indicator with Frangible Link in Place 

and the Instrument Set in Readiness for Service 

shows the instrument with link installed and the 

indicating target concealed. Fig. 28 shows the target 

indicating that a surge has passed (line-insulator units 

flashed over). 

The surge indicator will operate satisfactorily when 

connected across a or ti on of the tower structure 

Fig. 28. Surge Indicator with Target Showing. Thus 

Indicating That a Surge has Taken Place 

ductors. It will be noted that in each case the location 

of the instrument is such that it is readily accessible 

to the attendant near the main or upright structure of 

the tower. The tap lead extends along the tower arm 

and is connected to the iron of the tower at a point 

near the sumort for the insulator assemblv. This 
INSTRUMENTS FOR LIGHTNING MEASUREMENTS 245 

co~ir~eciing lead is securely fastened to the tower at 

each end and supported with sufficient insulators 

along its length to prevent the lead from falling on a 

live conductor and causing a line interruption. 

Briefly, the instrument operates according to the 

following procedure: When the insulator assembly 

flashes over the rush of discharge current through the 

Fig. 29. Schematic Diagram for Mounting Surge 

Indicators and Connecting Them to a Tower 

Having Horizontally Arranged Conductors 

instrument operation. The insertion of a new trip link, 

which is accomplished very readily, resets the instrument in readiness for another surge indication. 

Fig. 31. Surge Indicator for Multiple-surge Indication, 

in Position That Indicates Two Surges 

tower arm gives sufficient voltage across the instrument and the necessary follow-up current to disrupt 

the frangible link and allow the spring pressure to 

force the indicating target into the visible position. 

Fig. 30. Schematic Diagram for Mounting Surge 

Indicators and Connecting Them to a Tower 

Having Vertically Arranged Conductors 

Fig. 32. Interior of the Surge Indicator Shown in Fig. 31 

Some 1500 of these instruments have already been 

installed on transmission lines and very gratifying 

results have been obtained. A positive record of flashover is obtained and the cost of tower climbing patrols - - Power current from the line is not necessary for is materially reduced. 
246 April, 1931 GENERAL ELECTRIC REVIEW Vol. 34, No. 4 

rnr~ I ne - suige iIidicator ilas lot.eI, in aI,ot~ier 

form for multiple-surge operation as shown in Figs. 31 

and 32. This arrangement permits the insertion of five 

trip links and the indication of five surges without 

reloading. 

Lightning-severity Meter 

The instruments already described have all been 

designed for connection to the transmission line or 

tower and serve to obtain measurements or indicaFig. 33. Lightning-severity Meter 

tions of surge conditions on the structure only. It is 

very desirable that some device be available which 

will serve to record the intensity of storm conditions 

to which the transmission line is subjected. 

is a rneasure ui tiie i~liegrated fieid intensity over 

the period of exposure. The depth of exposure can 

be readily measured by photometric methods and 

an arbitrary but definite rating for storm severity 

obtained. 

Several field installations of this device have been 

operated through the 1930 lightning season and the 

Fig. 34. Instailation of Lightning-severity Meter and 

Antenna for Field Measurements 

Fig. 35. Type of Record Made by the Lightning-severity Meter 

To serve this purpose, the lightning-severity meter 

was produced. This instrument consists of a camera 

containing a photographic film, a glow lamp, and an 

antenna. Fig. 33 shows the instrument and Fig. 34 

shows a field installation. Fig. 35 shows the type of 

record obtained. TTTl . vv nen the anierma is withi~i tiie cloud field, it 

obtains a charge proportional to thz strc~gth of that 

field. When the stroke t&es place, the field around 

the wire collapses and the antenna charge passes 

through the glow tube thereby producing a porportional illumination which is recorded on the photographic film. The depth of light exposure on the film 

results obtained suggest that valuable information 

will be obtained through the future operation of this 

instrument. 

Conclusion 

The number of instruments recently designed and iiow '--- l:-l-'.-:.-- .-- availau~e lux- ~ig~~~~~ix~g-surge IIieasure- rnOrr+" hhn" nl*Onrlr7 *n".l..l+orl . Illblllra rraa aurauj rbauLubu 1:: marked improvement in the engineering understanding nf lightning 

phenomena. Through the continued use of these 

instruments, additional valuable data can be obtained and a final solution of the lightning problem 

reached. 
Conclusion 

The number of instruments recently designed 

and now available for lightning-surge measurements has already resulted in a marked improvement in the engineering understanding of lightning 

phenomena. Through the continued use of these 

instruments, additional valuable data can be obtained and a final solution of the lightning problem 

reached.