A1.. t n I .utilizing more advanced techniques de-tpp ication or rower ine v utage veloped in the interim. As an outgrowthof this work, there has been developed a

Monitor power line outage monitor described indetail in a companion paper.3 The ap-plication of this power line outage monitor

JOHN F. ATKINSON JAMES D. COOKE to rural electric power distribution sys-MEMBER AIEE NONMEMBER AIEE tems is described herein.

The Outage MonitorTHE PROBLEM of reporting outages may go unreported until daylight. In

on electric power distribution sys- many rural areas telephone service is in- The outage monitor consists essentiallytems is as old as electric distribution it- adequate or nonexistent and it is not un- of the following components arranged on aself. It has generally resolved itself by usual for outages to be reported by postal distribution system as shown in Figure 1:reliance upon the affected consumer re- card or letter. transmitter; receiver; indicator; andporting through the medium of the tele- The ideal solution to the outage re- remote modulators.phone. In urban or suburban areas little porting problem is a device which auto- The transmitter, shown in Figure 2,time is lost in receiving outage reports. matically and instantaneously reports to can be located near the substation. ItHowever, in rural areas, such is not the dispatcher the existence of an outage supplies a continuous, unmodulated car-necessarily the case. and indicates its location. The develop- rier signal which is propagated throughout

Telephone reporting of rural outages ment of such a device has been a challenge the primary distribution system.often involves long distance calls. Many to the electric industry for many years. The receiver can be located at almostaffected consumers are reluctant to report In 1941 an automatic device' 2 for re- any point on the distribution system thatoutages by long distance telephone, pre- porting outages was installed experi- is convenient to the dispatcher's office orferring to let "someone else" do it. At the mentally on rural power distribution service headquarters. Figure 3 shows aother extreme a single outage may cause systems in Ohio, Minnesota, and Virginia. receiver installed adjacent to a trans-a flood of long distance telephone calls. Work on these experimental installations mitter.

In some rural areas outages occurring was halted by World War II. After the The indicator, shown in Figure 4, can belate at night or in the early morning hours war, further work was undertaken, located in the dispatcher's office or service

headquarters. It is usually connected tothe receiver by means of a 2-wire linesuch as a telephone pair.

MOD. 2 MOD.6 The remote modulators are located onthe distribution system at points that areto be monitored for outages. Each remotemodulator sinusoidally alters the im-

MOD. 7 pedance of the distribution line at thepoint of attachment at a predetermined

\/\OCR IMOD. 9 and selected audio frequency rate. ThisSUBSTATION

MOD.I \ Aresulting dynamic impedance is reflectedSUBSTO CRN OCR back to the transmitter as the transmitterMOD.8 _ _ _ _ _ _ _ _ _ _ _ _ _ _

Paper 51-237, recommended by the AIEE CarrierCurrent Committee and approved by the AIEE

/ s \ /_ ~~~~~~~~~~TechnicalProgram Committee for presentation atTRANSMITTER OCR MOD. 3 MOD. 5 \ the AIEE Summer General Meeting, Toronto,*a_E \d ~~~~~~~~~~MOD.IOOnt., Canada, June 25-29, 1951. Manuscript

'zA/ RECEIVER \submitted March 21, 1951; made available forX \ ~~~~~~~~~~~~~~~~~~~printingMay 14, 1951.

<g/~~~~~~~~~~, \~~~~~~~JOHN F. ATKINSON is with the Rural Electrifica-.t ~~~~~~~~~~~~~~~~~~~~tion Administration, United States Department of

<5/ ~~~~~~~~~~~~~~~~~~Agriculture, Washington, D. C., and JAMES D.MOD 4 ~~~~~~~~COOKEis with the Central Virginia Electric^sy ~~~~~~~~~~~~~~~~~~~~Cooperative,Lovingston, Va.

INDICATOR 0 5 10 The authors wish to express their gratitude toIIIIII I1 I I I A. G. London, Sr. and E. Altman of Clay Electric

DISPATCHER'S OFFICE SCALE OF MILES Cooperative, and to H. W. Kelley and J. M.McCutchen of Rural Electrification Administra-tion for their work in conducting field tests of theFigure 1. Arrangement of outage monitor components on a rural distribution system outage monitor.

1292 Atkinson, Cooke-Application of Power Line Outage Mfonitor AIEE TRANSACTIO.NS

decreases with distance while percentmodulation increases with distance. Thiscondition may be used to advantage inthat the receiver can be located effec-tively at almost any point on the line.If the receiver is located near the transmittermitter, the per cent modulation level received is low but the carrier level is high.On the other hand, if the receiver islocated at, say, the 15-mile point, the mcarrier level is lower but the percentmodulation level is higher. The net resultin either case is a demodulated signal of ftrelatively constant level. The receivermay be located out beyond the modulatorto a maximum distance where the carriersignal level approaches line noise level.This is possible because of the highermodulation level available out beyond themodulator.

Test Installations

Experimental installations of the out-age monitor have been made on the linesof Central Virginia Electric Cooperative,Lovingston, Va. and on the lines of Clay Figure 3. Outage monitor receiver installedElectric Cooperative, Keystone Heights, adjacent to transmitter

Figure 2. A transmitter installation Fla. Both of these systems are typicalrural distribution systems, each encom- transmitters and their associated remote

moduatiobytherecpassing over 1,000 miles of 7.2/12.5-ky modulators.load impedance. Amplitude ddulato Distribution circuits and serving ap- Automatic sectionalizing devices onof the carrier signal is thus produced. proximately three raral consumers per rural distribution systems are normallyThe modulating frequency is determined mile of line. Each of these experimental installed from zero all the way out to 25by the controlled audio-frequency source installations consists of a transmitter, a miles from the substation. Under suchin each remote modulator. The per cent receiver, an indicator, and ten modu- conditions, with the transmitter at ormodulation varies along the line and is lators. near the substation, sufficient operatingdetermnined compositely by the impedance The amount of experimental equipment range can be obtained to monitor prac-excursions of the remote modulator, the available was limited and consequently tically all sectionalizing points energizedattenuation factor of the line connecting the entire systems could not be moni- from the substation. Separate transmit-the transmitter to the remote modulator, tored. The purpose of the tests was to ters and receivers are usually required forthe multiplicity of circuits comprising the determine operational and performance each substation, although under certainradial feeders and the impedance of the characteristics of the outage monitorwhen conditions it is possible to couple thetransmitter tank circuit. Modulation is applied to a rural distribution system. carrier energy to another substationdetected by the receiver and the resulting through a suitable filter network.audio frequencies are passed on to the Distance Capabilityindicator unit which displays the ener- Line Noisegized or nonenergized condition of the One of the factors of prime interest inmonitored lines. A remote modulator the operation of the outage monitor was Hitag dinstallation is shown in Figure 5. the distance over whic-h it would reliably characterized by a rather high ambient

Figure 6 shows how the degree of operate. It has been found that it wouldmodulation varies along a representative operate satisfactorily, without special35-mile line. The effect of taps and line treatment, over distances up tobranch circuits are not shown in this about 40 miles. On some lines where con-illustration but will be discussed later. siderable carrier energy was lost in res-The modulator at point B may be ad- onant taps, this distance was reduced tojusted to produce approximately 85 per about 20 miles. If the distribution linescent modulation at that point. Per cent are treated so as to confine the carriermodulation decreases in the direction of energy to the desired feeders, the range ofthe transmitter, but remains constant at operation can be increased considerably.85 per cent out beyond the modulator. Typical rural distribution systems are

Figure 7 shows the approximate attenua- made up of radial feeders operating out oftion of the carrier signal on the same 35- one or more substations. Such being themile line. From these two figures it can case, it has been found convenient tobe seen that in the first 20-mile section of locate a transmitter at or near each sub- Figure 4. Indicator unit installed in radioline in the illustration, the carrier level station with receivers located between dispatcher's office

1951, VOLUME 70 Atkinson, Cooke-Application of Power Line Outage Monitor 1293

The outage monitor principle of operation * TRANSMITTER 'y - LINE

S~ ~~~~~~~~~~~~~~~~~~~~~~ REOTMODULATOREbpermits locating the receiver near the j 40- _- __transmiitter where a strong carrier signal ZOis always assured. Thus the carrier signal o3035-overrides almost all types of line noise o eat h e -except power arcs occurring near the re- ioiceiver. Line noise has not proved to be a r- -an operating problem, even during violent nthunderstormns. Sht 5 n15 20 25 30 35

LINE DISTANCE IN MILES

Taps and Branch CircuitsFigure 7. Approximate attenuation of a

Distribution taps and branch circuits 100O-kc carrier signal along a 35-mile distribu-whose effective lengths are odd multiples son lineof one quarter wavelength tend to act aslow impedance bridging circuits. In Oil circuit reclosers contain seriessome cases it has been found necessary to connected solenoids which operate the re-

effectively shorten, lengthen or isolate closures when fault conditions occur.

such taps or branch circuits by the inser- The inductance of these solenoids acts as

tion of a choke coil or by installation of a an r-f choke which tends to attenuate the

Figure 5. Remok modubtor instalbtion termination unit. Such treatment is carrier signal. Fortunately, reclosers ofnecessary only when the tap approximates higher ampere rating have less inductancethe critical length. Shifting the carrier and consequently produce less attenua-

, ufrequenc of the transmitter by a few tion. Such reclosers are always locatedkilocycles may solve this problem without nearer the substation where moinimumresorting to line treatment, attenuation is more important. By-Another scheme that has been utilized passing these solenoids with small capac-

is to make use of sueh critical taps by in- itors has been resorted to in unusual cir-stalling a remote modulator at the outer cumstances, but as a general rule no

end of the tap. Since the remote modu- special treatment of oil circuit reclosers is

apli s Hlator acts to alternately short circuit and required.usually limits the distanceoverwhich open circuit the tap at a given audio fre- Line type voltage regulators offer more

carrier circuits can be made to opquency rate, such impedance alterations serious attenuation and it has usually beenare reflected to the input end of the tap. found necessary to by-pass the series coils

Figure 5. Remote modulator installation This modulates the carrier signal appear- with capacitors of about 0.05 micro-ing on the main feeder. Such installations farad.of remote modulators have proved effec- Shunt capacitors act as a direct short

noise level in the radio frequency spec- tive. circuit to carrier frequencies. Small

trum, particularly in the 50 to 150 kc series r-f chokes must be inserted in the

range. This radio frequency noise is Standing Waves shunt capacitor leads to prevent short

caused by corona, defective equip- circuiting of the carrier signal. Here

ment, static discharges on loose hard- Standing waves are generally present, again, use can be made of the one quarterware, loose connections, poor ground since it is not feasible to terminate dis- wavelength tap. By installing the capac-

bonding, induced atmospheric static, and tribution lines in their r-f characteristic itor bank on the outer end of such a tap,defective or inherently noisy consumer impedance nor to maintain impedance the input end of the tap becomes a highappliances. High ambient noise level matches on all branch circuits or taps. impedance point. Under such conditions,usually limits the distance over which Such standing waves, however, have not neither the tap nor the shunt capacitor iscarrier circuits can be made to operate. been found to be detrimental. The r-f detrimental to the operation of this type

power loss introduced is made up by in- of carrier equipment.creasing the transmitter power output as

1 TRANSMITTER LINE required. Standing wave pattems must Weather Effects* ~~~REMOTE MODULATOR be taken into account when locating the

remote modulators on the line, the best Operation of the outage monitor was

______________ results being obtained when the modu- noted particularly during mild icing of2 ~~~~~~~~~~~latorsare located at voltage antinodles.

so ~~~~~~~~~~~~~~~~~~~~~~~~~~REMOTEMODULATORS

Transformers, Oil Circuit Reclosers, A PHASE

z40 ~~~~~~~~Voltage Regulators, and Other B PHASEApparatus C PHASE

It has been found that while such pO 5 10 15 20 25 30 35 items as distribution transformiers and UTRANSMITTER

LINE DISTANCE IN MILES lightning arresters introduce slight im-

Figure 6. Per cent modulation along distribu- pedance discontinuities in the line, thetion line with remote modulator located at the attenuation of the carrier signal due to Figure S. Phase-to-ground method oF cou-

20-mile point this bridging effect is not significant. pling transmitter to line

1294 Alkinson, Cooke-Application of Power Line Outage Monitor AIEE TRANSACTIONS

REMOTE MODULATORS by mutual inductive and capacitive mine suitable installation points. ItA PHASE coupling. consists of a vacuum tube voltmeter, a

C PHASE ¶ Coupling between all three phases and battery powered modulator and a specialground as shown in Figure 9 has also been coupling capacitor4 built into a "hottried. Although this gives more even stick."

VTRANSMITTER carrier distribution, line attenuation is This coupling device is used to quicklymuch greater than in the single-phase couple the survey instrument to the linemethod. The receiver is normally coupled at any desired point. Carrier voltage

Figure 9. Alternate method of phase-to- to the line between one phase and ground. level can be read on the meter and theground coupling When the transmitter and receiver are modulated signal produced can be de-

physically located at the same spot, the tected and measured at the central re-receiver is coupled directly into the ceiving point. Figure 10 shows the

distribution lines in the winter of 1950 on transmitter thereby saving the installa- portable survey instrument.the Virginia installation. No appre- tion of a separate coupling capacitor. Location of the remote modulators isciable degradation of signal was observed. not limited to voltage antinode points, butOn the Florida installation, no change Locating the Remote Modulators insufficient modulation usually results if

in operation has been observed during the modulators are coupled to the line atextremely wet weather or during thunder- Optimum performance of remote modu- voltage nodes. Intermediate points usu-storms. lators is obtained if special attention is ally produce satisfactory results.

given to their location on the distribution

Interference with and system. Since standing waves are usually Locating Transmitter and ReceiverFrom Other Services present, it has been found best to locate

the remote modulators at or near voltage Location of the transmitter and re-

In early experimental models the re- antinodes. Such points represent high ceiver is not critical and installation canmote modulators were found to emit har- impedance points on the line and are most usually be made almost anywhere on themonics which were objectionable in the responsive to dynamic impedance varia- system. However, for practical con-broadcast band. A low-pass filter was tions produced by the modulators. siderations, it has been found desirable toincorporated in the modulator circuit A portable survey instrument has been locate the transmitter near the substa-which suppressed these harmonics to a devised which performs the function of a tion supplying the distribution system.level that was satisfactory for radio re- remote modulator, and( is used to deter- The reason for this is twofold. The trans-ceivers located immediately adjacent to mitter can distribute its carrier powerthe modulator. more evenly to all of the radial feeders of

Tests were made to determine the tle system, and it is less susceptible toeffect of interference from other carrier power outages wlen located near the sub-sources. station.

ltheoutage moitherews tuned to with-oA principal coiisideration in locating the

inthge outa monitr wasned to wt receiver is its location with respect to the

comimunication. Signal'level from this the indicator can be reasonably short.carrier was sufficiently strong for recep- l _tion of loud and clear speech on a carrier power source supplying the receiver.frequency receiver. This interfering MouainLvlcarrier signal had no noticeable effect onMouaonLvlthe operation of the outage monitor. and Signal LevelsHowever, if a resulting carrier beat fre- Modulation levels as measured at thequency were to coincide with one of the receiver input have been found to rangeutilized modulating frequencies, false I f a hoperation would probably occur during usa lv of . per cent Usingmththe outage period. prable urmveyof intrperatc it has the

Although there is no reason why the foundthatlauve2-votcrriertleeit thes re-noutage monitor would not interfere with mot t a 2 tcarrierm larlothion th ere -

other nearby carrier equipment utilizing usable modulationrMatith t itteroduse.the same channel, to date no complaints Csarierlevelsin atev ythe trans-itersiteof carrier interference have been received Caittermayerangteupcinto250 vots.trnsfrom neighboring utilities known to bemitrayaneuto20vlsusing adjacent carrier channels. Power Line Harmonics

Method of Coupling Transmitter and Power line harmonics interact with theReceiver to Line carrier signal within the remote modu-

lators to produce modulation. Modula-The most effective method of coupling tion levels produced by these power line

the transmitter to the distribution system harmonics are sometimes of the samehas been found to be phase-to-ground order of magnitude as the desired signalscoupling such as is shown in Figure 8. Figure 10. Portable survey instrument with produced by the modulators. ThisCoupling between phases is accomplished "hot stick" coupler factor must be taken into consideration

1951, VOLUME 70 Atkinson, Cooke-Application of Power Line Outage Monitor 1295

in the selection of modulating frequencies, tions. Improvements in the equipment 2. OUTAGE INDICATOR, J. F. Atkinson, D. E.Basler. United States patent number 2,337,441.

and the use of power line harmonic fre- and in techniques of application to rural3. CARRIER CURRENT SUPBRVISORY SYSTEM FOR

quencies must be avoided. power distribution systems are being DISTRIBUTION CIRCUITS, L. Podolsky, S. Lubin.

Experience gained from the two ex- made as a result of this experience. AIEE Transactions, volume 70, 1951, pages 1096-

perimental installations in Virginia and 4. PORTABLE COUPLING DEvicE, J. F. Atkinson.Florida~~~~~~~~~~~~~~~~~~~~~~4hasALEprovedNthatZtheprincipleoofFlorida has proved that the principle of References United States patent number 2,341,519.

operation of the outage monitor equip-ment is sound and practical. These in- 1. CARRIER INDICATOR REPORTS RURAL OUTAGES,

stallations are providing valuable ap- D. E. Basler, J. F. Atkinson. Electrical World

dataundra arity o codi- (New York, N. Y.), volume 115, number 8, Febru- No Discussionplication data under a variety of condi- ary 22, 1941, pages 52-54.

corded is passed directly through the mainn magnetic | ape vsci lograpn tor coil of the recording head producing mag-

netic impressions on the recording me-

Power System Anal sis dium. A high-frequency bias current

simultaneously applied to a coil of the re-

cording head makes magnetic impressions

E. C. SCHURCH F. R. SCHLEIF closely proportional to the recordingMEMBC.ESCHURCH.E R.S AIEE current over a wide range of current.1MEMBER AIEE ASSOCIATE AIEE

For applications in which an especiallywide range of frequencies is to be re-

THE inconvenience, expense, and de- long attracted interest. One of the first corded, such as sound recording, self-de-| lay of obtaining automatic records of advantages to attract interest is the fact magnetization of the recording medium

power system phenomena and of obtain- that the magnetic recording medium can becomes a limitation in the recording of

ing records during staged field tests with be erased and reused practically an un- the higher frequencies. Self-demagnetiza-

conventional oscillographs has prompted limited number of times. This permits tion is a function of the ratio of the length

the investigation of magnetic recording continuous recording of phenomena, in- to thickness of the small magnets set up

techniques for this purpose. While there cluding steady state conditions, even by the recording process in the magnetic

is an abundance of information in engi- where only transients or abnormal condi- medium.2 It is thus also a function of the

neering literature on the recording of tions are of interest. Thus, the tran- ratio of frequency to speed of the record-

sound by magnetic tape or wire, little scription or examination of a small portion ing medium. It may be regarded as a

information is available on the charac- of the recorded information is substituted magnetic short circuiting of the flux as the

teristics of applicability of magnetic re- for the fast starting feature of the present magnetic poles get closer together. How-

cording to the field of oscillography. A conventional automatic oscillograph. In ever, for available recording media and

review of current techniques and ap- this substitution two benefits may be reasonable speeds the frequency at which

paratus discloses that applicability to this gained: The mechanical difficulties at- self-demagnetization becomes appreciable

field is limited by lack of a suitable pickup tending any fast starting feature are is well above the range required for

device. The development of a unique eliminated and the steady state conditions power system oscillographic applications.

magnetic pickup device described here before the transient are recorded, whereas Thus, the recording process is readily

adapts magnetic tape recording to the in conventional equipment, the recording accomplished by well-known means with

field in which conventional oscillographs is started by the transient or abnormal suitable accuracy for the purposes de-

of both the automatic and laboratory condition itself. scribed in this paper.

types are usually employed. The ad- The economy aspect of the magnetic The usual means of reproducing the in-

vantage of reusability of the recording recording technique has not been over- formation which has been recorded in the

medium inherent in magnetic recording looked. However, while it has previously form of magnetic impressions on the tape

permits convenient incorporation of the perm-itted the continuous type of record- suffer more limitations than the recording

"anticipator" feature in an automatic ing just mentioned, subsequent trans- process. The most commonly used

oscillograph. Transcription of the mag- cription of the desired portions of the re- pickup device is similar to the recording

netic records at reduced tape speed by corded information has required some of head. In fact, a single unit often serves

pen and ink recorder considerably en- the conventional photographic recording both purposes for audio applications.hances both automatic and laboratory material and the conventional oscillo- The magnetic flux from the recording

oscillograph applications by elimination graph itself. Although complete elinmeina- medium threads along the magnetic cir-

of the usual photographic processing. tion of photographic materials and the cuit of the pickup and through the pickupBoth are made possible by the novel delay and inconvenience of photographic coil. The only voltage produced in the

pickup device which delivers an output processing is a desirable goal, it has not pickup coil is that due to the changes of

voltage independent of the speed of the generally been achieved, magnetic flux. The rate of change of the

tape. Construction and test of a model flux and hence, for a given recording cur-

oscillograph using the new pickup device Previous Limitationsfurnish a basis for design of a practical Paper 51-239, recommended by the AIEE Instru-

automatic recorder. A brief review of some of the principles proen adby theAEE Technical Program^ Commnitteeemployed in magnetic recording and re- for presentation at the AIEE Summer General

.^ Meeting, Toronto, Ont., Canada, June 25-29, 1951.

Advantages Offered production or transcription may clarify Manuscript submitted February 14, 1951; madeits previous limitations. In the most available for printing May 14, 1951.

The possible advantages of magnetic usual applications, the electric current F. C.e SCHUReS anrd F. OR. SCHlLRIP are with the

recording for oscillographic purposes have representing the phenomenon to be re- Colo.

1296 Schurch, Schleif-A Mlagnetic Tape Oscillograph for Power System Analysis AJEE TRANSACTIONS