Reference NBS

Publications

NBSIR 81-2334

NAT'L INST. OF STAND & TECH

AlllDb 03 & 71 &

Development of Power System

Measurements -- Quarterly Report

April 1/ 1981 to June 30, 1981

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Center for Electronics and Eiectricai Engineering

Electrosystems Division

Washington, DC 20234

June 1981

Preoared for: Department of Energy

Office of Electric Energy Systems

Street & Pennsylvania Ave., SM.W. — QC Stop 3344

ington, DC 20481

,U56

81-2334

1981

NATIONAL BDWAl

OF 8TANDABD8

LIBEABT

NBSIR 81-2334

<1 1 DEVELOPMENT OF POWER SYSTEM

MEASUREMENTS - QUARTERLY REPORT

APRIL 1, 1981 TO JUNE 30, 1981

SEP i 6 1981

iLu

Quod

no, 2iR. E. Hebner, Editor

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Center for Electronics and Electrical Engineering

Electrosystems Division

Washington, DC 20234

June 1 981

Prepared for: Department of Energy

Office of Electric Energy Systems

12th Street & Pennsylvania Ave., N.W.

Mail Stop 3344

Washington, DC 20461

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

Foreword

This report is intended to summarize the progress on four technical

investigations during the third quarter of FY 1981. Although reasonable

efforts have been made to ensure the reliability of the data presented,

it must be emphasized that this is an interim report so that further

experimentation and analysis may be performed before the conclusions

from any of these investigations are formally published. It is

therefore possible that some of the observations presented in this

report will be modified, expanded, or clarified by our subsequent

research.

i i i
TABLE OF CONTENTS

Page

Foreword iii

Abstract 1

1. INTRODUCTION 1

2. DC FIELDS AND ION MEASUREMENTS Project Mo:' A018-EES 1

3. INCIPIENT FAULT DETECTION/LOCATION Project No: A063-EES ... 3

4. TECHNICAL ASSISTANCE FOR FUTURE INSULATION SYSTEMS RESEARCH

Project No: A053-EES 7

5. OPTICAL MEASUREMENTS FOR INTERFACIAL CONDUCTION AND BREAKDOWN

Project Mo: A057-EES 10

6. REFERENCES 14

iv
DEVELOPMENT OF POWER SYSTEM MEASUREMENTS — QUARTERLY REPORT

April 1, 1981 to June 30, 1981

R. E. Hebner, Editor

This report documents the progress on four technical

investigations sponsored by the Department of Energy and

performed by the Electrosystems Division, the National

8ureau of Standards. The work described covers the period

April 1, 1981 to June 30, 1 981. The report emphasizes

measurements of ion density in air, the use of signals

above 1 GHz to detect incipient faults in cables, the

measurement of the by-products which develop during

partial discharge activity in SFg, and the determination

of the breakdown behavior of an oil-paper interface.

Key words: cables; composite insulation; dc fields; high

voltage; incipient fault; insulation; liquid breakdown;

SFg; space charge; transformer oil.

1 . INTRODUCTION

Under an interagency agreement between the U.S. Department of

Energy and the National Bureau of Standards, the Electrosystems

Division, MBS, has been providing technical support for Dot's research

on electric energy systems. This support has been concentrated in

four areas — the measurement of electric fields, the measurement of

the el ectromagnetic properties of solid insulating materials and

cables, the measurement of partial discharge ohenomena in gaseous

dielectrics, and the measurement of interfacial electrostatic field

distributions and of space charge density. The technical progress

made during the quarter April 1 to June 30, 1981, is summarized in

this report.

2. DC FIELDS AND ION MEASUREMENTS

P roject No . A01 3-EES

The objectives of this effort are to investigate devices and

measurement techniques which may be used to characterize the electrical

environment near high voltage dc ( HV DC ) transmission lines, to evaluate

methods being used for calibrating such devices, and to develop and

establish calibration facilities at MBS which will permit independent

verification of the accuracy of user calibrations.

By develooing appropriate methods of instrument calibration, it

will be possible to compare measurements taken in the vicinity of a high voltage transmission line with measurements taken in biological

exposure facilities. Such a comoarison will be necessary in any

formal or informal risk assessment.

1
Most of the effort during the reporting period has been concerned

with measuring the efficiency of filtration methods for removing ions

from an air stream. Previous measurements [1,2] indicated that the

transmission of ions through a high efficiency particulate air (HEPA)

or "absolute" filter was no greater than one percent. These measurements were made by measuring the conductivity of air before and

after it passed through the filter. By virtue of this high efficiency

for removing charge from an air stream, a HEPA filter can be used to

determine space charge density by measuring the volumetric flow rate

through the filter and the current resulting from the charge collected

by the filter.

A somewhat different approach was followed in the present work.

A parall el -pi ate ion counter [3] was used to measure the. space charge

remaining in the air after it passed through the filter. An air

stream containing ions was drawn from a low-speed air flow facility

developed to provide a volume space charge [3] and passed through

the fi 1 ter-counter connected in series as shown in figure 1. By

comparing the space charge density measured by the two systems, a value for the transmission of ions through the filter was obtained.

In this report, the transmission of the absolute filter is defined

as the space charge density measured by the counter divided by the sum of the densities measured by the counter and by the filter.

The measurements were made for different electrical conditions

and flow rates. Positive and negative ion densities ranged from

5 x 10 4 to 5 x 10^/cm^ when the air flow facility was used. In a related measurement, an alpha particle source located near the filter

inlet produced a nearly neutral net space charge in which there were

equal positive and negative ion densities of 9 x 10^/cm^.. Flow

rates were adjusted so that air velocities at the face of the filter

varied from 2 to 5 m/s.

For all of the experimental conditions examined, the transmission

of the filter was less than A x 10-3. There was large variability

observed in the transmission for data runs taken on different days.

The largest uncontrollable variable in the present measurements is

the air that enters the air flow facility. Both the ion counter and

the filter have measurement capabilities which depend on ion

mobilities, so that some variability would be expected in the filter

transmission if the ion mobility spectra were not kept constant.

The measurements obtained using the filter-ion counter combination

are summarized in figure 2. Here a typical spread in observed values fo

transmission is indicated by an "error" bar. Also shown are the

earlier results of Paltridge and of Moore et al .

One way to alter the mobility spectrum of the ions is to insert

an absolute filter in the inlet of the air flow facility. With this

operating condition, the air passing through the source region is

free of particulates and charge. When operated in this way, the air

flow through the system is substantially reduced due to a lack of
flow capacity in the fan. As a result, signal levels drop to the

point where only estimates of the transmission can be made. For

these measurements, the transmission was always less than for the

unfiltered measurements. These results are not shown on figure 2.

A very low transmission was observed for the situation with low

net space charge but high positive and negative ion densities as produced by the alpha particle source. Here only a few values as large as 10"^ were observed, as indicated on figure 2. All other

data points were less than 10“6 and are not shown.

Measurements of the transmission of other filter materials were

made under similar conditions. For these filters, transmissions

ranged from 5 to 20 percent. A report describing the experimental

procedure and all the measurements summarized above is in preparation.

From these measurements, it is clear that the absolute filter can be a useful device for measuring space charge densities with uncertainties

of less than 1 percent (ignoring errors due to losses in inlet ducts

and fl ow rate)

.

Other research activities during the quarter included initial

measurements of the effects of operating ion counters above ground

in an environment with dc fields and space charge. These measurements

were made by using a monopolar line assembled in a high voltage lab.

The line was operated to produce vertical current densities comparable

to those found under present HVDC transmission lines.

During the next quarter, the ion counter measurements will be

continued. Reports describing the filter work and the low SDeed air

flow facility will be completed.

For further information, contact Dr. R. H. Mcknight, (301 ) 921 -31 21.

3. INCIPIENT FAULT DETECTION /LOCATION

Project No: A063-EES

The objective of this program is to identify and, insofar as practical, remove technical barriers to the develoDment of a successful

incipient fault detector/1 ocator for underground power transmission

use. NBS responsibility includes conducting an experimental program

that will aid the development of an incipient fault detection/location

system by measuring the rf characteristics of power cables, and evaluating

the frequency content of partial discharge pulses emanating from

incipient fault sites in a cable dielectric.

Previous measurements at NBS had indicated that the attenuation

of the high-frequency components in the applied voltage pulse limits

the resolution. In particular, laboratory investigation of the

attenuation as a function of frequency suggested that the loss occurs primarily in the semiconducting screening layers adjacent to the

inner and outer conductors.

3
—

2.44 m——

1.22 m—

1-22 m

Test

Section

Transition

Inlet

<£> o i

Figure

1.

Schematic

of

low

speed

air

flow

facility

with

filter

and

ion

counter

in

position

for

filter

transmission

measurements.
Transmission

Through

Filter

Air Speeed At Filter, m/s

Figure 2. Transmission of ions through a high efficiency particulate

air filter. Data points represent average values obtained in

several measurements. "Error" bars show SDread in observed data

values. Earlier results from ref. 1 and ref. 2 are also shown

as is the measured transmission of the filter for 0.3 micrometer

diameter particles. <» - positive ions; o - neaative ions;

A - positive ion transmission for zero net space charce high

ion density input (see text).

b
Because most of the losses occurred in the cables' screening layers,

it was recognized that another possibility exists. Higher frequency

(several GHz) waveguide modes, excited and confined within the polyethylene

in a frequency range of minimal attenuation, should be extremely

sensitive to the presence of small defects such as "trees" in the

dielectric

.

Pursuant to this concept, initial measurements were made using

time domain refl ectometry methods and a special microwave "launcher"

array . The method was"unsuccessful because the high-frequency content

in the transmitted pulse and the reflected signal were too small for

meaningful detection. A frequency domain method was then tried

with some success. Using a microwave sweep generator (2 to 18 GHz

range) and a sensitive spectrum analyzer, RF transmission tests were conducted on several power cables. These measurements, though

simple, did verify the transmission of microwave energy in a waveguide

mode within the cable's dielectric. There were also indications that

several modes may have existed and that the launcher and pickup

arrays were poorly matched to the dielectric. In order to better

understand the coupling mode patterns and the transmission, measurements

were performed using simple polyethylene rods to simulate the dielectric

(without the center conductor or screening layers) of a power cable.

The rods were high-density polyethylene of 4- .5 cm (1 .75 in.) and

5.0 cm (2 in.) diameters and lengths that ranged from about 0.6 to

2 .4 meters

.

Attenuation measurements as a function of frequency were made

on the 4.5 cm rods using a length substitution method. Preliminary

results showed good transmission qualities at frequencies from about

7 to 1 3 GHz. There were, however, near field effects in the ends of

the rods which made data i nterpretati on difficult. Employing longer

rod lengths, the attenuation appeared small using what is believed

to be TEq-| mode and possibly higher modes. These modes are confined

to the dielectric such that the electric field vector does not penetrate

the outer rod boundary, nor does any field exist near the center of

the rod. This being true, the presence of semiconducting screening

layers near the center and outside of cables should have little

effect on the propagation and hence should cause a minimum of attenuation.

Measurements are planned to improve the launcher and oickup arrays

which couple microwave energy into and out of the cable while also

providing good high voltage isolation. Attenuation measurements will

continue on the dielectric rods. As the measurement techniques are perfected, the rods will be changed, one step at a time, to simulate

power cables by adding a center conductor, screening layers, and, finally,

outer skid wires. The next and immediate goal is to design and test

several microwave couplers.

Our paper entitled "The Detection of Incipient Faults in Transmission

Cables Using Time Domain Refl ectometry Techniques," has been accepted for

publication and will be presented at the 3th IEEE/PES Conference and

o
Exposition on Overhead and Underground Transmission and Distribution to

be held in Minneapolis, September 1981.

For further information, contact Dr. W. E. Anderson, (301 ) 921 -21 31.

4. TECHNICAL ASSISTANCE FOR FUTURE INSULATION SYSTEMS RESEARCH

Project No: A053-EES

The objective of -this project is to develop diagnostic techniques

to monitor, identify, and predict degradation in future compressed

gas electrical insulating systems under normal operating conditions.

Focus is on the fundamental information and data needed to improve

test design and performance evaluation criteria. The investigation

of partial discharges (corona) in gaseous dielectrics is emphasized.

This phenomenon gives rise to degradation of the gas under high

electrical stress and may lead to breakdown. Measurement of partial

discharge inception in highly nonuniform fields may also prove to be

a preferred method to determine dielectric strength of electronegative

gases.

Planned activities for FY -81 include: (1) estimate the sensitivity

of low-frequency dielectric constant measurements as a monitor of

polar molecules in SFg; (2) determine effects of trace amounts of H2

O

and other polar gas molecules on partial discharge behavior in SF5 ; (3) prepare an archival publication on pulse characteristjcs of

positive and negative dc corona in SF 5 ; (4) examine the effect of

radiation on electron avalanche development and measure the radiation

emitted by corona; (5) identify gaseous decomposition products

resulting from corona .in mixtures of SFg, and determine the rate of

buildup of oxyfluorides as a function of discharge power; (5) model

discharge inception and test these models in a control 1 ed-ionizationzone test cell (in collaboration with MIT); and (7) initiate a program

to evaluate electrical breakdown data for gases (in collaboration

with N 8 S-UILA). In addition, there was an incomplete investigation

in FY-80, namely, the measurement of laser-induced optogalvanic

signals in electric discharges of rare gas-SFg mixtures to determine

the effectiveness of SFg in quenching metastable species.

Progress was made during the reporting quarter on all activities

except (1) and (3) which are comoleted and (2) which is nearly complete.

The major effort, however, has been focused on activity (5). Also

advances were made both at NBS and MIT toward the accompl ishment

of activity ( 6 ). New technical information acquired as a result of

these two activities is highlighted in this report.

The rates of production of the by-oroducts generated in a corona discharge were measured for SFg at an absolute pressure of 2Q0 kPa

(~2 atm) for average discharge power levels in the range of 50

to 670 mW with polished point-plane electrodes. The volume of the

test cell was 4.0 liters and the corona was operated at constant

7
current for a positive dc-voltage applied to the plane electrode.

The currents used were within the range of 1 .5 to 16 .0 yA. A gas

chromatograph-mass spectrometer (GC/MS), details of which have

previously been discussed [A], was used to monitor the concentrations

of H2 O, SOF2 (thionyl fluoride) and SO 2F2 (sul fury! fluoride) as

a function of time. The concentrations of the latter two compounds

could be determined quantitatively with a sensitivity of about 1 ppm.

To assure reliability in the quantitative analysis, the GC/MS was calibrated before and after each corona degradation experiment using

several individually prepared standard samples of SOF2 and SO 2F2

in SF 5

.

Only relative concentrations, however, of H2O could be

determined with the present system. It is believed that H 2O is

produced by discharge- induced desorption from the electrode surface.

Its concentration builds up rapidly with time at first and then

levels off, reaching roughly a constant value independent of discharge

power. It has been hypothesized [4-7] that SOF 2 results primarily

from hydrolysis of the primary decomposition product SF4 , whereas,

SO 2F 2 is generated within the discharge via reactions of sul furfluorides

with free oxygen and H2 O. The species SO 2 F2 has been observed [7]

to be absent after arc discharges have occurred in SFg.

The results of our measurements of SCF 2 and SO2F 2 concentrations

as a function of the net energy dissipated for three different power

levels are shown in figure 3. The significant conclusions from

these results are: a) the production rates of SOF 2 and SO 2F 2 are constant, at least up to concentrations of 200 ppm, and directly

proportional to the power dissipated, and b) SOF 2 and SO 2

F

2 aopear

with nearly equal concentrations. The fact that SO 2F 2 is produced

with much more relative abundance in a corona discharge than in an arc is interesting, and possible reasons for this important observation

need to be explored.

In the area of theoretical modeling of corona discharge phenomena,

computer codes were written that allow calculation of average electron

avalanche size, negative corona inception voltages based on the

streamer criterion, and the active electron initiation volumes for

positive corona in SF 5

. The calculated negative corona inceptions

agree favorably with our previously reported measurements [4,8],

although the basis for this agreement needs further examination. An

example of results obtained from calculation of electron initiation

volumes is shown in figure 4. Shown in the figure are the hyperbolidal

point electrode (shaded area) and the boundaries of the volumes at

the indicated voltages from which electrons, once released, can produce avalanches in excess of 1 x 10^ electrons sufficient to satisfy

the streamer criterion. Assuming uniformity of initiating electron

production, the probability of occurrence of avalanches greater than

10 ^ electrons is directly proportional to this volume. The calculation

of these volumes can be used to help exolain the previously observed [ 8 ] polarity effect in SF5 corona inceptions and is an imoortant first step

8
S0F2

CONCENTRATION

(ppm)

1 I 1 | 1 1 1 1 I I 1 4.0 8.0 12.0 16.0 20.0 24.0

ENERGY DISSIPATED jkJj

10 3

10 2

10

1.0

figure 3. Measured concentrations of SCF? and SOpF? as a function of net

energy dissipated in corona discharges ooenated at the indicated

oower levels.

Q

S0

2F

2

CONCENTRATION

(ppin)
in the calculation of the electron avalanche size distributions for

positive corona. A direct comparison of these distributions with

results of our previous measurements [ 6 ] should be possible. The

results of our modeling effort together with our results of corona inception measurements are being prepared for publication in the

IEEE Transactions on Electrical Insulation and for presentation at

the 1981 Conference on Electrical Insulation and Dielectric Phenomena.

During the next quarter we intend to complete the archival paper

mentioned above, and also prepare a paper on our corona degradation

measurements for presentation at the 3rd International Symposium on Gaseous Dielectrics. Further work will be carried out on the

measurement of by-product production rates in corona (activity (5))

and extension of these measurements to gas mixtures. Measurements

will be performed using a tunable laser to determine the wavelength

dependence of photon enhanced avalanche initiation for positive

discharges in SFg (activity (4)). The purpose of these measurements

is to understand the basic mechanisms of discharge initiation.

Improvements will also be made in the sensitivity of our pulse height

analysis technique so that our measurements of avalanche size

distributions can be extended to the region of greatest theoretical

interest. Investigations will continue on methods for improving the

quantitative analysis of H 2O in compressed SF 5 .

For further information, contact Dr. R. J. Van Brunt (301) 921 -3121.

5. OPTICAL MEASUREMENTS FOR INTERFACIAL CONDUCTION AND BREAKDOWN

Project No: A057-EES

The objective of this project is to develop techniques to measure

the interfacial phenomena which influence the electrical breakdown

character!’ sties of composite insulation systems. In particular, the

role of space charge in electrical breakdown is being investigated.

In transformer oils, the electro-optic Kerr effect is being used to

observe electric fields as a means of detecting space charge. This

study concentrates on oil-paper (pressboard) systems in which the solid

insulator is either parallel or perpendicul ar to the electric field.

It is recognized that impurities and possibly space charge have

an influence on the failure of composite insulating systems. Possible

formation of space charge is monitored as the concentrati on and

composition of impurities is varied. In addition, the breakdown

strength is measured and the locations of breakdowns are observed in

the composite insulation system with impurities.

Investigations described in the previous quarterly report provided

evidence of significant space charge distortion in contaminated transformer oil at elevated temperatures . The contaminated oil was obtained

10
from a transformer which had failed. During this quarter, a system

was designed and constructed to extend this investigation to 100°C

and above. The nylon and polyethylene parts used with the laminated

phenolic cell were found to be unsuitable for use at these elevated

temperatures . The cell's plumbing system had to be refurbished using

brass fittings and screws, fluorocarbon tubing, and some acetal

plastic parts. At the end of the quarter, the changes were completed

and the cell was tested to withstand 100°C for several hours. It is

anticipated that the results of the study at higher temperatures will

be available in the next quarterly report.

While the system to measure space charge in oil at elevated

temoeratures was constructed, experiments were conducted to

investigate the location of breakdowns in an oil-paper system containing

contaminated oil . Previous MBS studies have shown that for a clean,

well characterized system, breakdown does not necessarily occur at

an oil-paper interface and that the presence of an interface does

not necessarily reduce the breakdown strength of a system [10]. The

previous investigation raised practical as well as fundamental questions.

Field experience and some previous experiments by MBS and others had

demonstrated that interfacial breakdowns at relatively low voltages were a problem. Since interfacial breakdown was unlikely in clean,

carefully prepared systems, a possibility that impurities contribute

to the lowered breakdown voltage was investigated. The type of

experiments documented in reference 10 were repeated in expanded form

by investigating both clean, wel 1 -control 1 ed systems and contaminated

systems. The breakdown strength was measured and the location of

breakdowns observed in a "clean" system, in a system in which the oil was contaminated, and, indirectly, in a system in which the paper

was contaminated.

Obtaining statistically significant data is a very time consuming

process as the breakdown typically destroys the interface. The

apoaratus, therefore, must be disassembled and reassembled between

"shots." To minimize the amount of time expended, it was felt

preferable to survey the breakdowns at a number of selected conditions

with relatively few "shots" rather than applying numerous "shots" at

any one condition. In spite of that, more than 150 breakdowns had to

be performed to observe any preliminary trend. The results of the

preliminary survey are reported here.

To determine the influence of oil purity on breakdown location,

measurments were performed using clean (mechanically filtered and

degassed) oil and oil which was removed from a transformer which had

failed. The electrodes were two discs with rounded edges which

provided a uniform field. The discs were split along a diameter to

clamp the paper sample parallel to the electric field. The applied

voltage was 60-Hz ac, ramped at a rate of about 3 kV/s. The data

obtained for measurements in clean oil are summarized in table 1 .

11
Table 1. Data taken using clean oil.

Condition

Number of

Breakdowns Recorded

Breakdown Voltage

(2.5 mm gap)

No Interface 15 76 ± 10 kV

Interface Present 10 68 ± 11 kV

Interface Present

but Breakdown not

at Interface

7 74 ± 7 kV

Interface Present

and Breakdown at

I nterface

3 56 ± 9 kV

The results for the contaminated oil are shown in figure 5. It was determined that the contaminated oil contained small particles

which could be precipitated by gravity and which presumably

influenced breakdown. The first five shots were taken with no interface in the system. The system had, however, been shaken to suspend

the fine particles which had drifted to the bottom of the reservoir.

In this case, the breakdown voltage was 53 ± 7 kV--significantly

below the 76 ± 10 kV recorded for clean oil.

The second five measurements which were taken with an interface

in place had a higher breakdown voltage, 65 ± 12 kV. Suspecting

that the suspended particles were dominating the breakdown behavior,

the system was permitted to sit undisturbed overnight. Following

this extended settling time, five breakdowns were recorded without

an interface. The average breakdown voltage was 74 ± 7 kV— about

the same as clean oil. A series of ten shots was then taken, five

with an interface and five without, with the system shaken to distribute

the particles throughout the interel ectrode region. Without an interface, the average breakdown voltage was 34 ± 5 kV and with an interface 39 t 3 kV. From this set of data, it was postulated that

although the oil contamination (especially particulate contamination)

influences the breakdown voltage of the system, it has little effect

on the interfacial phenomena because again the breakdown does

not necessarily occur at the interface even with dirty oil.

The effect on breakdown arising from the condition of the paper

was obtained indirectly. Approximately 100 breakdowns are not reported

in table 1 or in figure 5. These occurred at relatively low voltages,

whenever an interface was included, and their cause was traced to the

condition of the paper. The impregnating procedure similar to the one used in manufacture of electrical equipment was unsatisfactory

for this application. A new procedure, whereby the paoer was impregnated with oil before installation in the breakdown cell and

12
(A>0 96b;|oa UMop^eejg

• <D

0)

13

Breakdown

Number

(Contaminated

Oil)
the cell was filled wittr oil in the presence of dry nitrogen rather

than vacuum, was found to be satisfactory.

The results obtained during this quarter point to the paper as the

critical element in the interfacial breakdowns. Efforts are continuing

to quantify the effects of air and water on the interfacial breakdown.

For further information, contact E. F. Kelley (301 ) 921 -3121 .

6 . REFERENCES

[1] G. W. Paltridge, J. Geophys. Res. Vol. 72, p. 1 269 (1 966).

[2] C. 3. Moore, 3. Vonnegut, and F. J. Mallahan, J. Geophys.

Res. Vol . 66 , p. 321 9 (1 961 ).

[3] R. H. Mcknight, F. R. Kotter, M. Misakian, and ?. Ortiz, "1980

Annual Report: Electric and Magnetic Field Measurements,"

Nat. Bur. Stand. (U.S.) NBSIR 81-2267 (1981).

[4] R. J. Van Brunt, M. Misakian, D. A. Leeo, K. J. Moy, and E. C. Beaty,

"1980 Annual Report: Technical Assistance for Future Insulation

Systems Research," Nat. Bur. Stand. (U.S.) NBSIR 81 -2242 (1 981 ).

[5] R. J. Van Brunt and 0. A. Leep, "Partial Discharge Induced

Degradation of Compressed SF 5 ," Proc. Workshop on Arc By-Products

in Gas-Insulated Equipment, EPRI Final- Report EL-80-8-LD, pp. 13-14

(1980).

[ 6 ] A. Baker, R. Dethlefsen, J. Dodds, N. Oswalt, and P. Vouros, "Study

of Arc By-Products in Gas-Insulated Equipment," EPRI Final Report,

EL -1646 (1980).

[7] C. C. Boudene, J. Cluet, G. Keib, and G. Wind, "Identification and

Study of Some Properties of Compounds Resulting From the Decomposition

of SF 5 Under the Effect of Electrical Arcing in Circuit-Breakers ,

Revue Generale De L' Electricite (RGE) - Numero Special, pp. 45-78

(1 974).

[ 8 ] R. J. Van Brunt and M. Misakian, "Comoarison of DC and 60 Hz AC

Positive and Negative Partial Discharge Inceotions in SF 5 ," Proc.

Conf. on Electrical Insulation and Dielectric °henomena, National

Academy Press, Washington, D.C., pp. 461-469 (1980).

[9] R. J. Van Brunt and D. A. Leep, "Characterization of Point -Plane

Corona Pulses in SFg," J. Appl . Phys. (to be published, 1981).

[10]

E. F. Kelley and R. E. Hebner, "Breakdown Between 3are Electrodes

With an Oil-Paper Interface," Nat. 3ur. Stand. (U.S.) NBSIR 80-2071

(1 980)

.

14
cm

igure 4 . Calculated boundaries of discharge initiation volumes at

the indicated voltages for positive corona in SF 5 at

100 kPa. Only electrons produced within these boundaries

can give rise to electron avalanches in excess of 1 x 1 0^ electrons.

15

N BS-114A (REV. 2-80

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET (See, nstruct/ons)

1. PUBLICATION OR

REPORT NO.

NBSIR 81-2334

2. Performing Organ. Report No. 3. Publication Date August 1981

4. TITLE AND SUBTITLE

Development of Power System Measurements -- Quarterly Report April 1, 1981 to June 30, 1981

5. AUTHOR(S)

R. E. Hebner, Editor

S. PERFORMING ORGANIZATION (If joint or other than N BS. see in struction s)

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

7. Contract/Grant No. Interagency Agreement

EA-77-A-01 -60T0

8. Type of Report & Period Covered

Quarterly

4/1/81 to 6/30/81

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City. State. ZIP)

Department of Energy

Office of Electric Energy Systems

12th Street & Pennsylvania Ave., N.W,

Washington, D.C. 20461

Mail Stop 3344

10. SUPPLEMENTARY NOTES

~l Document describes a computer program; SF-185, FlPS Software Summary, is attached.

11. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bi bl iography or literature survey, mention it here)

This report documents the progress on four technical investigations sponsored by

the Department of Energy and performed by the El ectrosystems Division, the

National Bureau of Standards. The work described covers the period April 1, 1981

to June 30, 1981. The report emphasizes measurements of ion density in air, the use of signals above 1 GHz to detect incipient faults in cables, the measurement

of the by-products which develop during partial discharge activity in SF^, and the

determination of the breakdown behavior of an oil-paper interface.

12. KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolons)

cables; composite insulation; dc fields; high voltage; incipient fault; insulation;

liquid breakdown; SF^; space charge; transformer oil*

13. AVAILABILITY

i X| Unlimited

! j For Official Distribution. Do Not Release to NT1S

j

' Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402.

j Order From National Technical Information Service (NTIS), Springfield, VA. 22161

14. NO. OF

PRINTED PAGES

15. Price

USCOMM-QC SCU3-P90