Reference

NBS

PUBLICATIONS

NAT'L INST. OF STAND & TECH

AlllDb 3 4 7 4 A

NBSIR 85-3111

Development of Power System

Measurements -- Quarterly Report

July 1 , 1 984 to

September 30, 1984

R. E. Hebner, Editor

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Center for Electronics and Electrical Engineering

E’ectrosystems Division

Gt ithersburg, MD 20899

November 1 984

Issued Marcn 1985

Prepared for: Department of Energy

"'’vision of Electric Energy Systems

QC 100 independence Avenue, SW

]_QQ ashington, DC 20585

, U56

85-3111

1984

NBSIR 85-3111

DEVELOPMENT OF POWER SYSTEM

MEASUREMENTS - QUARTERLY REPORT

JULY 1, 1984 TO

SEPTEMBER 30, 1984

R. E. Hebner, Editor

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Center for Electronics and Electrical Engineering

Electrosystems Division

Gaithersburg, MD 20899

November 1984

Issued March 1 985

Prepared for: Department of Energy

Division of Electric Energy Systems

1000 Independence Avenue, SW

Washington, DC 20585

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

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

Foreword

This report summarizes the progress on four technical investigations

during the fourth quarter of FY 84. 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.

iii
TABLE OF CONTENTS

Page

Foreword ill

LIST OF FIGURES v

LIST OF TABLES vli

Abstract 1

1. INTRODUCTION 1

2. ELECTRIC AND MAGNETIC FIELD MEASUREMENTS

Subtasks No. 01 and 02 1

3. TECHNICAL ASSISTANCE FOR FUTURE INSULATION SYSTEMS RESEARCH

Subtask No. 03 5

3.1 Oxyfluoride Production in SF 6 /02 Mixtures 8

3.2 Oxyfluoride and Nitrogen Oxide Production in SFg/N2 Mixtures. . . 13

4. INTERFACIAL PHENOMENA IN LIQUIDS

Subtask No. 04... 21

4.1 Interfacial Breakdown Studies 23

4.2 Electro-Optical Electric-Field Measurements 26

5. NANOSECOND BREAKDOWN IN POWER SYSTEM DIELECTRICS

Subtask No. 05. . 26

6. REFERENCES 31

iv
LIST OF FIGURES

Page

Figure 1 . Schematic view of monopolar line and ion counter

with inlet located in the ground plane. ............. 3

Figure 2 . Measured space charge density for different line

operating conditions as a function of volumetric

air flow M through the ion counter. ............... 4

Figure 3 . Estimates of duct losses based on eq ( 1 ) of the

text. Data are the same as figure 2 . The

values of P 0 are based on measurements of J

and E and an assumed ion mobility of

1.4 x 10

-4

m /Vs (positive ions) ............ 6

Figure 4 . Comparisons of measured air speeds near the ion

counter inlet (1 cm above the ground plane) and

the speed of the ion due to the electric field at

the surface of the ground plane. Volumetric flow

rates (M) were as shown

Figure 5 . Measured absolute SOF4 concentrations versus net

charge transported for 40 pA negative corona in

SF0/O2 mixtures containing the indicated

percent-by-volume concentrations of O2 . The

"pure" SFg, contained trace levels of O2 which

could not be accurately determined. 9

Figure 6. Measured absolute SOF2 concentrations versus net

charge transported for 40 uA negative corona in

SFg/02 mixtures containing the indicated

percent-by-volume concentrations of O2. The

"pure" SFg contained trace levels of O2 which

could not be accurately determined 10

Figure 7 . Measured absolute SO2F2 concentrations versus net

charge transported for 40 pA negative corona in

SF5/O2 mixtures containing the indicated

percent-by-volume concentrations of O2 . The

"pure" SFg contained trace levels of O2 which

could not be accurately determined 11

Figure 8. Calculated production rate constants k for electron

collision induced dissociation processes in SF0/O2

mixtures at E/N = 1 x lO

-13 Vm2 from Masek.,

et al. [6],

Figure 9 . Measured absolute CO2 concentrations versus net charge

transported for 40 pA negative corona in SF^/ 0 2 mixtures containing the indicated percent-by-volurae

concentrations of O2 . The "pure" SFg, contained trace

levels of O2 which could not be accurately determined

v
LIST OF FIGURES (continued)

Page

Figure 10. Measured absolute SOF4. concentrations versus net charge

transported for 40 pA negative corona in SFg/N2 mixtures

containing trace amounts of H2O and O2 and the indicated

percent-by-volume concentrations of N2. . . . . . 16

Figure 11. Measured absolute SOF2 concentrations versus net charge

transported for 40 pA negative corona in SF^/^

mixtures containing trace amounts of H2O and O2 and the

indicated percent-by-volume concentrations of % 17

Figure 12. Measured absolute SO2F2 concentrations versus net charge

transported for 40 pA negative corona in SF5/N2 mixtures

containing trace amounts of H2O and O2 and the indicated

percent-by-volume concentrations of N2 18

Figure 13. Measured absolute NO and N2O concentrations versus net charge

transported for 40 pA negative corona in an SF & /30%N2

mixture. The vertical arrows indicate times when the

discharge was turned off for more than 12 hours 20

Figure 14. Preliminary test data investigating data-taking methods.

The first column (1) is the run number; the second column

(2) shows when an interface was used (N = no interface

present, Y = interface in place); the third column (3) is

the number of breakdowns which were observed for the

specified conditions or procedure; the fourth column (4)

tells the status of the oil, normal oil from the barrel,

or degassed; the fifth column (5) tells the procedure used

in separating the electrode halves: S means the electrode

halves were split for a short time, L means for a long

time, NO means that the electrodes were not opened, T=0

,

1, 2, 5 refers to the number of minutes waited before

ramping up the voltage again after the previous breakdown

experiment, N*S means that the electrode halves were split

many times which produced many bubbles (BUBS), NI means a new interface was installed before each breakdown; and NNI means that a new interface was not installed; the sixth

column (6) refers to the condition of the pump circulating

the liquid through the cell, C0NT means the pump ran continuously, OFF-RMP means the pump was turned off during

the application of voltage, OFF-ALL means the pump was off

during the entire experiment, and the number in

parentheses refers to the speed of the pump; the last

column (7) is the mean and standard deviation (in

parentheses) of the breakdown voltage for that

experiment. All these data were taken at room temperature

and with 60-Hz ac voltage 24
LIST OF FIGURES (continued)

Page

Figure 15. Breakdown voltage as a function of temperature for ac and

dc voltages, with and without paper interfaces bridging

the gap. The first column (1) tells when an interface

was present (Y = yes, N = no); the second column (2)

shows the number of breakdowns produced under the present

conditions; the third column (3) is the temperature; the

fourth column (4) describes the type of voltage applied;

the fifth column (5) describes the location of the

breakdown ( ——means no interface was present, ALL refers

to the breakdown voltage with the interface present

making no distinction whether or not the breakdown

occurred at the interface, BAI, or not at the interface,

NAI) ; the sixth column (6) shows the percentage of

breakdowns which occurred at the interface when an interface was present; the next two columns (7) and (8) are the mean breakdown voltages with the standard

deviations in parentheses, both the ac peak values and

rms values are shown, the rms values are plotted with the

dc values in the horizontal graph 25

Figure 16. Pulse forming components to provide nanosecond rise time

pulses: (a) actual circuit, (b) simplified

pulse-shaping configuration, after the first gap has

shorted, neglecting the cell 28

LIST OF TABLES

Table 1. Limiting constant production rates, Rc , and

deviations from linearity e 22

Table 2. Limit constant production rates, Rc , and deviation

from linearity £ 22

Table 3. Pulse shapes based on RLC component values 29

vii

DEVELOPMENT OF POWER SYSTEM MEASUREMENTS — QUARTERLY REPORT

July 1, 1984 to September 30, 1984

R. E. Hebner, Editor

This report documents the progress on four technical

investigations sponsored by the Department of Energy and performed by

or under a grant from the Electrosystems Division, the National Bureau

of Standards. The work described covers the period from July 1, 1984

to September 30, 1984. The report emphasizes the errors associated

with measurements of electric and magnetic fields, the properties of

corona in compressed SFg gas, the measurement of interfacial phenomena

in transformer oil, and the measurement of dielectric properties on nanosecond time scales.

Key words: electric fields; gaseous insulation; interfaces: liquid

insulation; magnetic fields; partial discharges: SF 6 ; solid insulation:

transformer oil.

1 . INTRODUCTION

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

the National Bureau of Standards, the Electrosystems Division, NBS, has been

providing technical support for D0E ? s research on electric energy systems. This

support has been concentrated on the measurement of electric and magnetic

fields, the measurement of interfacial phenomena and of partial discharge

phenomena, and the measurement of dielectric properties on nanosecond time

scales. The technical progress made during the quarter July 1, 1984 to

September 30, 1984 is summarized in this report.

2. ELECTRIC FIELD MEASUREMENTS

Subtasks Nos. 01 and 02

The objectives of this investigation are to develop methods to evaluate and

calibrate instruments which are used, or are being developed, to measure the

electric field, the space charge density, and current density in the vicinity of

high-voltage dc transmission lines and in apparatus designed to simulate the

transmission line environment; to provide electrical measurement support for

DOE-funded efforts to determine the effects of ac fields on biological systems,

and to provide similar support for biological studies which will be funded by

the State of New York.

During the present quarter, measurements of ion density were made with an aspirator type ion counter operating in the ground plane, in the presence of an external dc electric field. The influence of the external electric field on density measurements was examined by varying the field strength and air flow

rate through the ion counter.

The operation of aspiration devices such as ion counters, conductivity

tubes and filtration devices can be affected by the presence of large external

fields such as those found near HVDC transmission lines or some bioligical

exposure systems. Laboratory studies are being done at NBS to understand the

1
magnitude of errors introduced by these external fields and to determine optimum

conditions for operating these instruments. In a study reported earlier [1], an ion counter was operated above the ground plane under a monopolar line which was

in corona. The experiment was configured such that the air flow through the ion

counter could be varied. This feature and the use of inlets of different sizes

allowed a wide variation in the air speeds near the inlet to the counter. The

ion counter and associated electronics were isolated from ground so that the

potential of the assembly, relative to space potential, could be varied.

Measurements were taken in which the dependence of the measured ion density on

(1) ion counter potential and (2) air speed at the inlet were determined. It was found that the indicated ion density depended strongly on ion counter

potential as the potential approached the average space potential, and that for

a grounded counter, the ion density fell off as the air speed at the inlet

decreased. This latter result is generally consistent with a picture in which

the ions are lost to the inlet walls of the ion counter as a result of the

electric field, the influence of which increases as the air speed decreases.

Although operation of an ion counter above the ground plane offers a number

of advantages in an outdoor setting, the enhancement of the external field near

the inlet tends to augment any loss mechanisms that may be operating. Electric

field effects can be minimized by locating the ion counter such that its inlet

is in the ground plane. An experimental configuration similar to that used in

the work described above was set up in the laboratory and is illustrated in

figure 1. The ground plane was a table covered with aluminum as shown. The

electric field was measured using a field mill, and current sensing plates were located on either side of the opening to the ion counter. The duct to the ion

counter was made of metallic tubing and had a length of 0.4 m.

Measurements were made for three line operating conditions such that the

electric field at the surface of the ground plane was 14.8, 20.8, or 29.8 kV/m.

For each of these conditions, the flow rate through the ion counter was varied

and the space charge density p was determined using the relation p = I/M, where

I is the current measured by the ion counter and the volumetric flow rate

through the counter is M. At the same time the electric field E and vertical

current density J were also measured. The space charge density can be

determined from the relation p Q

=* J/kE, where k is an average mobility for the

ions making up the ion current. Calculations for p Q were made for each of the

three operating conditions studied. The results of these calculations and the

measurements are shown in figure 2. These are for positive corona and similar

results were seen for negative corona.

Because of the length of the duct and the large ion densities, estimates were made of the losses in the connecting the ion counter to the inlet in the

ground plane. These losses were estimated using the theory outlined by Kaune

et al. in [2]. In reference [2], an equation relating the spatial dependence of

space charge density at locations away from the source is given and a number of

applications cited. This equation was applied to the motion of ions in a duct

p/pQ » [1 + po (ku/ie

o

)]

-1 (1)

where p Q

is the initial space charge density, u is the average ion speed in

the duct, l is the length of the duct, e0

is the permittivity of space, and k

is the average ion mobility. Using p 0 calculated from the measurements of E

and J, estimates were made of the expected duct losses using average speeds in

2
DC line

Figure 1 Schematic view of monopolar line and ion counter with inlet located

in the ground plane.

3
,-(H x(C

uj/Q)d

10.0 -

9.0

8.0

7.0

6.0

5.0

4.0

3.0

i

1 r i 1 1—i r Po

i r

/

• •r E = 29.8 kV/m

7• E = 20.8 kV/m

• •

. PV • # • E = 14.8 kV/m

I I I

I 1 l_J 1 1 1 L 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28

M(m3/s) x 10-3

Figure 2. Measured space charge density for different line operating conditions

as a function of volumetric air flow M through the ion counter.

4
the ducts, calculated by assuming uniform velocities and the measured volumetric

air flow. The solid lines shown in figure 3 indicate the estimates of the space

charge density transmitted through the duct, starting with the initial ion

density pQ

. An additional set of measurements was made using a longer duct

and similar results were observed. It is clear that most of the losses appear

to be associated with duct losses. This is a puzzling result, since the

electric fields near the inlet are such that ion motion should be dominated by

the electric field forces. This is indicated in figure 4, which summarizes air

speed measurements made 1 cm above the ion counter inlet using a hot film

anemometer. Indicated for comparison are the drift speeds due to the ion moving

in the electric field.

In order to gain a better understanding of the motion of ions in the

electrohydrodynamic field near the inlet, modeling should be done. While the

full three-dimensional solution to the problem appears prohibitive, simpler two

dimensional models should yield significant information. Simpler modeling can

be done by using finite element calculations of the electric field near the

inlet and reasonable estimates of the air flow field. Additional experiments

are also planned using the parallel plate system at NBS in which the electrical

environment is better known than in the monopolar line configuration. Questions

of the perturbation of the operation of the parallel plate system will have to

be answered first and some effort in this area has been described

previously [3]

.

During the next quarter, testing and calibration of a magnetic fieldmeter

for measuring ambient ac magnetic fields will be completed. A space potential

probe will be fabricated for measurements of potential in dc electric fields

with space charge.

For further information contact Dr. M. Misakian at (301) 921-3121.

3. TECHNICAL ASSISTANCE FOR FUTURE INSULATION SYSTEMS RESEARCH

Subtask No. 03

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. The focus is on the

fundamental information and data needed to improve test design and performance

evaluation criteria. The scope of the project encompasses the following

investigations: 1) measurement and calculation of electric discharge inception

in compressed electronegative gases; 2) measurement, calculation, and

compilation of fundamental data on electron transport and electrical breakdown

in gases; 3) measurement of absolute electric discharge-induced decomposition

rates in gaseous dielectrics; and 4) examination of the influence of

contaminants like water vapor on the performance of compressed gas-insulated

systems. Emphasis is given in these investigations to the development and

evaluation of new measurement techniques.

The planned activities for FY84 included:

1) Preparation of conference and archival papers presenting results of our measurements on the production rates for the oxyfluorides SOFn , SO'.- ir : SOFu, and SO 2 and H 2O generated by corona discharges in SF^ or Sr. H mixtures

;

5
p(C/m 3

)x10

-8

M(m3/s) x 10"3

Figure 3. Estimates of duct losses based on eq (1) of the text. Data are the same as figure 2. The values of p Q are based on measurements of J

and E and an assumed ion mobility of 1.4 x 10” 4 m

2 /Vs (positive

ions )

.

6
AIR

SPEED,

m/s

Figure 4. Comparisons of measured air speeds near the ion counter inlet C n above the ground plane) and the speed of the ion due to the elect r:' f -‘-eld 3-t the surface of the ground plane. Volumetric flow rit -s

'• were as shown.

7
2) Extension of the measurements on by-product production rates in gas

discharges to the mixtures, SFg + O 2 , SFg + N 2 , SFg + CO 2 , and

SFg + c-C 4 F 8 + CHF 3 ;

3) Compilation of a computerized bibliography of electrical breakdown data

in insulating gases and publication of this bibliography in an NBS report;

4) Investigation of the effects of trace quantities of water vapor on the

enhancement of electron avalanche growth and corona discharge development

in SFg.

Activity 1) has been completed. A paper entitled "Production Rates for

discharge Generated SOF 2 , S0 2F 2 , and S0 2 in SFg and SFg/H20 Mixtures" by

R. J. Van Brunt, T. C. Lazo, and W. E. Anderson has appeared in the Proceedings

of the Fourth International Symposium on Gaseous Dielectrics, Knoxville,

1984 [4], and an archival paper entitled "Production Rates for Oxyfluorides

SOF 2 , S0 2F 2 , and SOF 4 in SFg Corona Discharges," by R. J. Van Brunt has recently

been submitted for publication [ 5 ].

Considerable progress was made on activity 2) in the past year. It was decided, however, to focus on the first two mixtures, namely SFg/N2 and SFg/02 > because of the significance of air as a common contaminant in SFg used as an insulant, and because of the possible Importance of SFg/N2 and SFg/air mixtures

as substitutes for pure SFg in insulation applications. Preliminary results for

SF g /0 2 mixtures were presented in a previous quarterly report [ 6 ] . A paper

discussing results obtained to date on both SFg /02 and SFg/N2 mixtures has been

submitted for presentation at the 37th Annual Gaseous Electronics Conference to

be held in Boulder, Colorado, October 1984 [7]. The results of additional

measurements performed on SFg/0 2 and SFg/N 2 mixtures during the past quarter are highlighted in this report.

Concerning activity 3), a bibliography of data on electrical breakdown in

gases has been completed and is available as an NBS Technical Note [ 8 ] . The

bibliography contains: 1 ) a list of archival papers and books that present data

on electrical breakdown in gases and which have been published since 1950; 2) a computer generated index indicating the references that give particular types of

data for each gas; 3) an author index; and 4) a list of relevant technical

conferences. The bibliography, which is intended to serve as a guide in

locating data on breakdown for a wide range of applications, can be obtained

either from the U. S. Government Printing Office, Washington, DC 20402, or from

the National Bureau of Standards, Electrosystems Division, Gaithersburg, MD

20899.

Although some progress was made on activity 4), this investigation remains

incomplete. It is intended that the work on this activity will be completed in

early FY 85.

3.1 Oxyfluoride Production in SFg/02 Mixtures

Figures 5-7 show data for S0F 2 , S0 2F2> an<* S0F4 production respectively in

mixtures containing 1 to 10 percent 0 2 in SFg compared with "pure” SFg

containing only trace amounts of 02 « Plotted are absolute concentrations in

pmoles versus net charge transported in the discharge, i.e., discharge

current x time. The measurements for all these mixtures were performed at the same indicated total gas pressure and discharge current of 200 kPa and 40 pA

8
NET CHARGE TRANSPORTED (C)

Figure 5. Measured absolute SOF^ concentrations versus net charge tr i

- - for 40 uA negative corona in SFg /02 fixtures contain: ng tine n

L

percent- by-volume concentrations of 02* The 'pure SF^ t'-nt.i trace levels of O

2 which could not be accurately ietem.n* •.

9
NET CHARGE TRANSPORTED (C)

Figure 6. Measured absolute SOF 2 concentrations versus net charge transported

for 40 pA negative corona in SFg/0 2 mixtures containing the indicated

percent- by—volume concentrations of 0 2

. The "pure" SF g contained

trace levels of 0

2 which could not be accurately determined.

10
Figure 7. Measured absolute SO 2F

2 concentrations versus net charge :r.m

for 40 pA negative corona in SFg /02 mixtures containing th- percent-by-volume concentrations of 0 9

. The "pure” SF ;

- nta : : trace levels of 0

2 which could not be accurately det 1 i.

11
respectively. In table 1 the corresponding limiting constant charge

rates-of-product ion Rc are listed for the different SF5 /O 2 mixtures

considered

.

The charge rate-of-production Rc is related to the usual time rate-ofproduction dc/dt by

Rc » dc/dQ - (dc/dt)i-1

, (2)

where i is the discharge current which was held constant in these experiments, Q

is the charge transported by the current i, c is the concentration of the

species under consideration, and t is time. The values of Rj. in table 1 are obtained from the slopes of straight lines fit to the upper portions of the curves shown in figures 5-7 for Q < Q^-f n , where is the minimum value of

the charge for which the assumption of linearity holds.

In general the production curves exhibit deviations from linearity that are most evident at the lowest values of Q, and are best described over the entire

range by the form

c(Q) - cQ + RQ 1+e

, (3)

where Cq, R, and e are constants. The values of e, which are a measure of

deviations from linearity, are also given in table 1 for fits of the form given

by eq (3).

The Rc results for the 3% 02 mixture are more uncertain than those for

the other mixtures because of the lower range of Q covered. Within the

uncertainties indicated, the results demonstrate that the addition of 1 percent

O 2 has virtually no influence on the production of the oxyf luorides . However,

at higher O 2 content, changes occur in the relative production of SOF 2 , SO 2 F 2 , and SOF^ which show possible influence of gas-phase 0 2 on not only the dominant

gas-phase reactions leading to oxyfluoride production, but also on the electron

energy distribution in the discharge [ 6 ] as will be discussed below. The fact

that the oxyfluoride yields are not significantly influenced by the introduction

of 1 percent 0 2 indicates that the production rates are principally controlled

by the dissociation rate of SFg in the discharge, i.e. by the process

e + SF 6 SFX + ( 6-x)F + e . (4)

This is consistent with the suggested [5] mechanisms for SFg decomposition and

oxyfluoride formation in corona.

When 0 2 is added at concentrations above 1 percent, the total oxyfluoride

yield drops with the most dramatic effect on the SOF 2 production. The

production of the other species drops slightly but does not significantly change

for increases in 0 2 concentration up to 10 percent. The drop in S0F 2 can be

attributed to two possible effects: 1) a drop in the SF & dissociation rate when

O 2 is added, and 2) a greater rate of SF 4. removal in the discharge due to the

reaction

SF 4 + 0 SOF 4. . (5)

It will be recalled [4,5] that the most important mechanism for S0F 2 production

is postulated to be hydrolysis of SF 4 in the bulk of the gas, i.e.,

12
SF ( 6 ) 4 + H 20 - SF 3 OH + HF

followed by

SF 3 OH - SOF 2 + HF . (7)

The effect of increasing the 0 2 content in SFg on the electron energy

distribution and thus on the dissociation rate of SFg in the gas has recently

been considered in theoretical calculations of Masek, et al. [9] using numerical

solutions of the Boltzmann Equation. Their calculations show that for a given

electric field-to-gas density ratio (E/N), the mean electron energy in the gas

shifts to lower energies as O 2 concentration increases. This gives rise to a lowering of the various ionization and dissociation rate constants with

increasing 0 2 content as shown in figure 8 .

When 0 2 is added, one can expect a higher relative concentration of 0

radicals in the discharge volume thereby enhancing the rate for reaction (5).

However, the failure of the S0F 4 production to increase with increasing 0 2 may

again be indicative of a suppression in the SFg dissociation rate. The same consideration also applies to the interpretation of the S0 2F 2 data, since this

species is expected to require 0 2 for its formation through the reactions

SF 2 + 0 2

-* S0 2F 2 ( 8 )

and

SF 3 + 0 2 S0 2F 2 + F . (9)

The production of SOF 2 is likely to be more sensitive to changes in the

discharge characteristics resulting from addition of 0 2 , because its primary

mechanism for production does not require the presence of this gas

.

There is, of course, reason to doubt that the drop in SFg dissociation rate

predicted by Masek, et al. is sufficient to entirely account for the observed

decrease in S0F 2 production. Certainly some of this decrease could be due to a relative enhancement in the competitive removal of SF 4 by reaction (5).

Measurements at higher 0 2 concentrations are needed to help resolve this issue.

In addition to the oxyfluoride production rates, measurements were also

made on C0 2 production in SFg/0 2 mixtures as shown in figure 9. It is clear

that C0 2 production goes up with increasing 0 2 content, and shows some tendency

to saturate at higher 0 2 levels. Undoubtedly, production of this species is iue

to reactions of 0 2 with carbon released from the stainless steel electrode.

3.2 Oxyfluoride and Nitrogen Oxide Production in SFg/N 2 Mixtures

Measurements similar to those just described for SFg/0 2 mixtures were also

performed in SFg/N 2 mixtures in which oxygen and water vapor were present at trace levels. Examples of results obtained for 50F 2 , S0 2 F 2 , and SOF 4 production

are shown in figures 10-12. Corresponding limiting constant charge rates-ofproduction are given in table 2. The most obvious effect of adding 'J 2 to S ? _ is a dramatic drop in the 30F 4 production. A statistically significant increase in

S0F 2 production is also noted at the highest N 2 concentration. The product:

rate of S0 2F 2 appears to be relatively unaffected by N2 content, at least

concentrations up 30 percent.

13
PRODUCTION

RATES,

k(cm3/s)

Figure 8. Calculated production rate constants k for electron collision

dissociation processes in SFg/C>2 mixtures at E/N = 1 x 10“ 15

from Masek, et al. [6].

induced

Vm2

14
NET CHARGE TRANSPORTED (C)

Figure 9. Measured absolute C0 2 concentrations versus net charge transported

for 40 pA negative corona in SF 6 /0 2 mixtures containing the indicated

percent-by-volume concentrations of 0 2

. The "pure" SF 6 contained

trace levels of 0 2 which could not be accurately determined.

15
f or

S

40

e yAa^g^^

e ^cor0

^

n^

n

gp

a^

0nS

. versus net charge transported

of_H2 0 and 02 and the

16
SOF

2

CONCENTRATION

(m

Moles)

210

180 -

150 -

120

1.0 2.0 3.0 4.0 5.0

NET CHARGE TRANSPORTED (C)

6.0

Figure 11. Measured absolute SOF

2 concentrations versus net charge transoor*. --c for 40 uA negative corona in SF-/^ mixtures containing trace incur,

of H2 O and O

2 and the indicated percent-by-volur.e concentr ic: ir.s .

:

N 2.

17
Figure 12. Measured absolute S0 2F 2 concentrations versus net charge transported

for 40 pA negative corona in SFg/N2 mixtures containing trace amounts

of H20 and 0 2 and the indicated percent-by-volume concentrations of

N 2

.

18
In the SF 6 /30%N 2 mixture, production of the nitrogen oxides, especially NO,

begins to become significant as seen in figure 13. For this mixture the NO

yield is roughly comparable in magnitude to that for S0F 4 , and the NO production

curve showed only slight deviation from linearity. The production of NO 2 could

not be observed by the method used. The yield for N2 0, as evident from

figure 9, was observed to be an order of magnitude below that for NO. Moreover,

the production curve for N20 appeared to be highly nonlinear, suggesting that

Its production mechanism involves relatively weak secondary reactions in the gas

phase

.

At present one can only speculate about the processes that would be

responsible for a selective decrease In the S0F 4 production relative to the

production of the other oxyfluorides with increasing N2 content. The effect is

too large to be accounted for entirely by the decrease in relative SFg

concentration. It is apparent that N2 is effective in inhibiting those

reactions that lead to SOF 4 formation. Since S0F4 most likely requires the

presence of 0 and OH free radicals in the discharge for its formation [5]

,

reactions such as 0+N2 ^N0+N , (10)

which can compete, for example, with reaction (5) in consuming oxygen containing

free radicals could play a role in reducing S0F 4 production. However,

reaction (10) is known to be quite slow [10], and the observed buildup of NO

does not appear rapid enough to account for the decline in S0F 4 yield. Other

mechanisms obviously deserve consideration in attempting to understand this

effect. Of possible importance, for example, is the relative effectiveness of

N 2 compared to SFg as a third body in stabilizing bimolecular formation of S0F 4 through processes like reaction (5).

A reduction in S0F 4 production, independent of the mechanism, should be

accompanied by an increase in S0F 2 production as observed. This is expected on

the basis of the expected predominant reactions involved in oxyfluoride

formation [5] . If process (5) is inhibited for any reason, then more of the SF4 produced by SF$ dissociation and subsequent recombination processes can be

expected to escape the active discharge volume and react with H 2O in the main

bulk of the gas to give SOF 2 according to reactions ( 6 ) and (7). The increase

in S0F 2 production, however, will necessarily be somewhat lower than the

decrease in S0F 4 production because of the competitive influence of relatively

fast recombination reactions such as [ 11 ]

SF 4 + F2'>’SFg. (11’

This is also consistent with the present observations.

The failure of S0 2F 2 production to be significantly affected by N 2 at

relative concentrations up to 30 percent is a reasonable expectation. The

reactions

NO + 0 ( 12 )

- n 20 , (13)

which could compete with reactions ( 8 ) and (9) in removing 0 2 from the

discharge volume are expected on the basis of available reaction rate ii: ? f 1

19
CHARGE m COULOMBS

Figure 13. Measured absolute NO and N20 concentrations versus net charge

transported for 40 pA negative corona in an SFg/30%N2 mixture. The

vertical arrows indicate times when the discharge was turned off for

more than 12 hours.

20

N

2

0

CONCENTRATION

(10* 7

Moles)
to be of minor importance. It is perhaps also worth noting that the production

curves for SO 2 F 2 appear to become more linear as N2 content increases, i.e., e o. On the other hand the corresponding SOF 1+ production appears to become more nonlinear. This effect, if significant, could be indicative of the role played

by the relatively slow reaction

SOF 4 + H20 -* S0 2F 2 + 2HF , (14)

which can occur in the bulk gas or on the walls of the discharge vessel [5]

.

At

present, the uncertainties in the data are too great to enable one to draw firm

conclusions about the relative importance of various reactions using observed

deviations from linearity in the production curves.

During the next quarter, it is expected that more measurements will be made

on oxyfluoride and nitrogen oxide production in SFg/C>2 and SF 5 /N2 mixtures.

Emphasis will be given to mixtures containing O 2 and N2 concentrations which are higher than those considered in this report. Preliminary measurements may also

be made on discharge by-product production rates using mixtures which contain

isotopically pure

i8 02 and H 2 180 in order to determine that the mechanisms for

oxyfluoride formation in SFg discharges are indeed those that have been

postulated [2]. Further measurements will be performed to determine the

influence of trace levels of water vapor on the statistical size distribution of

electron avalanches in point-to-plane SFg discharges.

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

4. INTERFACIAL PHENOMENA IN LIOUIDS

Subtask No. 04

The objective of this research is to develop techniques to measure the

electrical behavior of liquid-solid composite insulation for use in high-voltage

systems. Model systems of practical interest will be investigated, such as the

interface between transformer oil and pressboard. The effects of contamination

and temperature up to 150 °C will be documented in these model systems in two

ways: 1 ) breakdown measurements using high-speed photography, and 2 ) electrooptical measurements of the electric field in the vicinity of the interface.

Such field measurements will provide understanding of the role of soace charze

and surface charge in high-voltage apparatus.

Up to this time, prebreakdown streamer propagation characteristics in many

liquids and under a variety of circumstances have been documented and

published. Additionally, streamer initiation studies have been started

employing high optical magnification of the initiation point on the electrode.

Studies into the effects of interfacial breakdown have revealed that the

breakdown does not necessarily occur along a paper interface bridging the

electrodes, nor is the interfacial breakdown voltage necessarily lower than in

the liquid. An electro—optical, electric-field measurement system based on the

Kerr effect has been successfully tested on transformer oil between parallel

plates, with and without pressboard interfaces. With the oil used, significant

space charge has been observed at elevated temperatures.

The research this quarter focused in two areas. First, interfacial

breakdown probabilities were investigated using paper and oil which were - • specially treated as in previous studies. Second, electro-optical riel i

21
Table 1. Limiting constant production rates, R

c , and deviations from

linearity e.

sof4 sof2 SO,'h

Gas Rc R c

R c

Mi xture (umol es/C) e (umoles/C) e (umoles/C) e

SF6 /trace 02 30.2 0. 077 24.7 0.077 15.9 0.,805

SF6 /1%02 29.8 -0. 010 23.4 0.131 13.7 0.,433

SF6 3%02 21.0 -0. 055 14.8 0.011 6.6 0..000

SF6 /10%02 23.4 -0. 169 9.9 0.064 13.4 0..125

Table 2. Limit constant production rates, R

c , and deviation from linearity e.

SOF, SOF, SOoFc

Gas R

c

Mi xture (umol es/C) £

sf6 30.2 0.077

SF6 /5%N2 20.5 0.037

SF6 /15%N2 18.4 -0.010

SF6 /30%N2 4.0 -0.580

Rc

(umol es/C) e Rc(umol es/C) £

24.7 0.077 15.9 0.805

30.4 0.077 15.7 0.840

34.4 0.016 15.4 0.742

45.6 0.075 14.7 0.024

22
measurements were made in the gap between a quasi-hyperbola electrode and a plane electrode. This latter work was performed in conjunction with a guest

graduate student, Satish M. Mahajan, from the University of South Carolina.

Both of these activities are summarized in this report.

4.1 Interfacial Breakdown Studies

In the quarterly report for the first quarter 1984, a cell design is

presented which provides for changing a paper interface inside the cell without

opening the cell [12]. A parallel-plate electrode geometry is provided by two

cylinders with their ends facing each other. The edges of the cylinders are rounded so that the breakdowns occur randomly over the flat portion of the

electrode faces. The cylinders are split in half along their axes. The halves

of each cylinder can be separated so that a paper interface can be installed.

When the cylinder halves are clamped together again one is left with a parallelplate electrode system with paper bridging the gap between the electrodes. The

outer diameter of the cylinders is 2.54 cm with the flat, parallel-plate region

having a diameter of about 1.9cm. The gap between the electrodes is 0.246 cm.

In previous interfacial studies performed at NBS, much attention had been

paid to the treatment of the oil and paper. The oxygen and water in the oil was removed by bubbling nitrogen through the oil for 48 hours or more, and then the

oil was completely degassed under vacuum. The paper was vacuum baked at 125°C

for at least 24 hours and then covered with the degassed oil, all under vacuum. Anticipating that water in the paper could be a source of stimulation for

interfacial breakdown, no attempt was made to remove the water from the paper in

the present experiment. The oil was degassed somewhat to increase its ability

to dissolve post-breakdown bubbles to facilitate the taking of data.

To check the methods used to obtain the data, a series of trial experiments

was made using different procedures to take the data. The results are shown in

figure 14. The important lesson learned from this collection of data is that care must be exercised or the experiment will be biased by the experimental

method used. One significant cause of the variation is that separating the

electrodes generates bubbles in the transformer oil. If the voltage is turned

on too soon, the bubbles in the split do not have sufficient time to dissolve

the oil and they cause breakdown. To minimize the effect of this potential

problem yet keep the time to take the data down to a tolerable length, a :r.e- minute interval was used as a minimum between each ramping of the vc.tage and

any change which was made in the cell. Another important feature to note is

that although the speed of the pump was not a factor, it was necessary that trpump remain on during the course of an experiment, apparently to remove tr

dilute the post-breakdown by-products.

The data on the probability of breakdown at the interface as a fur.ot.tr.

temperature are shown in figure 15. Both 60-Hz ac and dc were applied. or..- ac voltage is shown in figure 15. After each breakdown with an interface

present a new interface was installed. Four temperatures were selecte: :r study, but only when the temperature reached 150°C was there observe: --.y obvious decrease in breakdown voltage. However, throughout these - x

r

when an interface was present the breakdown did not necessarilv _ . .r interface, and when the breakdown occurred at the interface the volt-..-

23
EXPERIMENTAL CONDITIONS

RN 1 #P OIL PROC PUMP VB (SD)

PA N 10 NOM SLS CONT 75(16)

1 1 1 1 1 1

I PB N 10 NOM SSSLSSS CONT 84(11)

PC N 10 NOM SSSLSSS OFF-RMP 76(15) h • 1 PD N 10 DEG SSSLSSS OFF-RMP 77 (4) < PE N 10 DEG NO T = 1 CONT 95 (6) y— h

PF N 10 DEG NO T = 1 OFF-ALL 79 (6) i i PG N 10 DEG NO T =0 OFF-ALL 80 (6) t—•- i PH N 10 DEG SSS T = 0 OFF-ALL 74 (5) f PI N 5 DEG N*S BUBS OFF-ALL 71 (5) i- i PJ N 10 DEG NO T = 0 CONT 83 (7) -H PK N 10 DEG NO T = 1 CONT 95 (5) 1“*“H

PL N 5 DEG NO T = 0 CONT 88(15) |_ »' » PL N 5 DEG NO T = 1 CONT 98(13) H - i PL N 5 DEG NO T = 2 CONT 96(12) H— 1 PL N 5 DEG NO T = 5 CONT 100(11) 1 H

PM N 7 DEG NO T= 1 CONT(6) 96 (9) H —

H

PM N 7 DEG NO T = 1 CONT(2) 99 (6) I » | PM N 7 DEG NO T = 1 CONT{8) 96(10) t- - 1 PN Y 5 DEG NNI T = 1 CONT(5) 98 (9) 1 •— 1 PN Y 5 DEG NNI:5 *ST = 1 CONT(5) 99 (3) !—•—

1

PN Y 5 DEG NI T= 1 CONT(5) 94 (7)

_l1 1I 1I JL_ LI 1

I 50 60 70 80 90 100 110 120

BREAKDOWN VOLTAGE, kV (AC PEAK)

Figure 14. Preliminary test data investigating data-taking methods. The first

column (1) is the run number; the second column (2) shows when an interface was used (N = no interface present, Y = interface in

place); the third column (3) is the number of breakdowns which were

observed for the specified conditions or procedure; the fourth column

(4) tells the status of the oil, normal oil from the barrel, or degassed; the fifth column (5) tells the procedure used in separating

the electrode halves: S means the electrode halves were split for a short time, L means for a long time, NO means that the electrodes were not opened, T=0, 1, 2, 5 refers to the number of minutes waited

before ramping up the voltage again after the previous breakdown

experiment, N*S means that the electrode halves were split many times

which produced many bubbles (BUBS), NI means a new interface was installed before each breakdown; and NNI means that a new interface

was not installed; the sixth column (6) refers to the condition of

the pump circulating the liquid through the cell, C0NT means the pump

ran continuously, 0FF-RMP means the pump was turned off during the

application of voltage, OFF-ALL means the pump was off during the

entire experiment, and the number in parentheses refers to the speed

of the pump; the last column (7) is the mean and standard deviation

(in parentheses) of the breakdown voltage for that experiment. All

these data were taken at room temperature and with 60-Hz ac voltage.

24
EXPERIMENTAL CONDITIONS

1 #P TEMP V BLOC % Bi VBs PK RMS (SD)

N 21 29 AC — 102(10) 72(7)

Y 20 29 AC ALL 15% 101(10) 71(7)

Y 17 29 AC NAI 100(10) 70(7)

Y 3 29 AC BAI 107(5) 75(4)

N 15 27 DC — 74(6)

Y 14 28 DC ALL 43% 76(8)

Y 8 28 DC NAI 79(7)

Y 6 28 DC BAI 72(8)

i ?

N 19 101 AC —

Y 20 101 AC ALL

Y 15 101 AC NAI

Y 5 101 AC BAI

98(11) 69(8)

101(12) 72(8)

102(13) 72(9)

97(10) 69(7)

N 15 101 DC — 79(9)

Y 11 101 DC ALL 27% 77(7)

Y 8 101 DC NAI 78(8)

Y 3 101 DC BAI 74(4)

N 20 151 AC — 87(9) 61(6)

Y 20 150 AC ALL 25% 88(8) 62(6)

Y 15 150 AC NAI 87(8) 61(6)

Y 5 150 AC BAI 91(8) 64(5)

N 23 151 DC —

»

50(9)

Y 5 151 DC NAI §9(4)

_l J L 0 10 20 30 40 50 60 70 80 90 100

BREAKDOWN VOLTAGE (kV)

Figure 15. Breakdown voltage as a function of temperature for ac and dc

voltages, with and without paper interfaces bridging the gaD. The

first column (1) tells when an interface was present (Y = yes,

N = no); the second column (2) shows the number of breakdowns

produced under the present conditions; the third column (3) is the

temperature; the fourth column (4) describes the type of voltage

applied; the fifth column (5) describes the location of the breakdown

( ——means no interface was present, ALL refers to the breakdown

voltage with the interface present making no distinction whether >r not the breakdown occurred at the interface, 3AI, or not at the

interface, NAI); the sixth column (6) shows the percentage of

breakdowns which occurred at the interface when an interface was present; the next two columns (7) and (8) are the mean breakdown

voltages with the standard deviations in parentheses, both the ic

peak values and rms values are shown, the rms values are plotted .•if:

the dc values in the horizontal graph.

25
necessarily lower than when the breakdown did not occur at the interface. These

data confirm earlier results for this type of experiment.

It is important to note that at 100°C it was necessary to wait until the

paper on the spools stopped releasing bubbles which were assumed to be water

vapor coming from the water in the unprepared paper. It is not practical to

take data while the bubbling continues because the application of voltage

quickly brings all nearby bubbles into the region between the electrodes. The

phenomenon of bubbles coming from the paper begins again at around 185°C. Under

the assumption that some component of the paper material is vaporizing, no data

were taken. Thus, with the paper used, data were taken only up to 150°C.

However, the cell system endured higher temperatures successfully.

4.2 Electro-Optical Electric-Field Measurements

The second area researched this quarter is the electro-optical measurement

of field between the tip of a hyperbola-like electrode over a plane — a two

dimensional field geometry. This work was performed in conjunction with Satish

M. Mahajan of the University of South Carolina. These data are being analyzed.

It is anticipated that the results of a comparison of a computer prediction of

the field with the electro-optical measurements will be available in the near future

.

An archival paper will be produced documenting the field enhancement due to

space charge in various transformer oils between parallel- plate electrodes. The

study will provide information for a range of temperatures and electrode

materials

.

An archival paper will be written documenting the results obtained above

concerning the breakdown probability near a paper interface bridging the

electrodes, as a function of temperature.

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

5. NANOSECOND BREAKDOWN IN POWER SYSTEM DIELECTRICS

Subtask No. 05

The objectives of this effort are to develop measurement capabilities and

provide data in support of the DOE program concerned with the effects of fastrising electrical signals on electric power systems. Whereas the effects of

microsecond rise-time pulses are reasonably well understood, the effects of

nanosecond rise-time pulses on power system dielectrics are not well known.

Appropriate model test systems will be developed along with the necessary

measurement techniques.

The first step in understanding nanosecond breakdown in power system

apparatus is to develop model systems to investigate nanosecond breakdown. To

do this, it is necessary to design a circuit which will provide selectable rise

times and fall times at voltages sufficiently high to cause streamer initiation.

Additionally, measurement systems must also be developed to monitor the voltage

waveform present at the electrodes. To meet these objectives, the following

research has been accomplished:

26
1. Nanosecond Divider Tests: A 10 kQ noninductive resistor divider was designed having a low-side resistance of 50 n. Using step response

testing methods, it was shown to have a rise time of 3 ns or faster.

Such speeds are sufficient to monitor the initial experiments which

will be concerned with minimum voltage rise times of 5 ns. The divider

is small enough to fit inside a breakdown cell and attach to the

electrode to which voltage is applied.

2. Modeling of the Proposed Test Circuit: Figure 16 shows the proposed

test circuit which will permit the selection of the rise time and fall

time of the pulses applied to the test cell. The analysis of this

simple system is straight forward using the equivalent circuit shown in

figure 1 6 b . The first gap in figure 1 6a is represented by a switch.

The gap in the test cell is not shown for purposes of calculation, but,

if present, it would appear as a switch shorting the resistor.

Assuming an increasing current I in the counter-clockwise direction,

the total voltage must sum to zero:

Ldl/dt + RI + Q/C = 0. (15)

Here Q is the charge on the capacitor. The solution to the homogeneous

equation is a linear superposition of two exponentials which is written:

Q = Ae + Be (16)

where

a = (R/2L) [ 1 + v/(1 - 4L/R

2

C)

l/2

],

(17)

‘b = (R/2L) [ 1 - v/(1 - 4L/R

2

C)

1/2

].

Examining this solution, it is clear that oscillations are avoided if

4L/R“C < 1, which turns out not to be too restrictive.

To obtain the constants A and 3, one invokes the initial conditions on Q(t) : Q(0) = -CV

Q

, and dQ(0)/dt = 0. From these initial conditions the

constants are found to be

A = bCV /(a-b), 3 = -aCV /(a-b).

o o The voltage across the lead resistor R will then be given by V = RdQ/dt. “or

analysis, it is convenient to normalize to the applied voltage;

U = V/V = (1-4L/R 2 )~ 1/2

r e ' Dt -e_at

]. o If we assume that

4L/R

2

C << 1 ,

then the constants simplify to

a = R/L, and o = 1/RC;

27
GAP 1

t (a)

Figure 16. Pulse forming components to provide nanosecond rise time pulses:

(a) actual circuit, (b) simplified pulse-shaping configuration, after

the first gap has shorted, neglecting the cell.

28
(22)

further, the normalized voltage across the load, U, reduces to

.. - (R/L ) t -t/RC

U » e ~ e

Within this approximation we see that L/R is the rise time constant of the

pulse and RC is the fall time constant.

Returning to the exact expressions for the moment, another quantity of

interest is the position of the peak of the applied pulse. Assuming the pulse

starts at t » 0, the time the peak is reached is obtained by taking the

derivative of eq (18) and setting it to zero. Solving for the time gives the

time to reach the peak

T = [ 1 / (a— b ) ] ln(a/b). (23)

The size of the pulse relative to the capacitor charging voltage is then

obtained by evaluating eq (18) at time t = T. In table 3, we show a comparison

of the types of pulse shapes which should be attainable based on these

calculations

.

Table 3. Pulse Shapes Based on RLC Component Values

R

(Q)

C

(nF)

L

(uH) 4L/(R

2

)C

TIME

RISE

(ns)

CONSTANTS

FALL

(ns)

T

(ns)

U

PEAK

20 0.5 0.01 0.20 0.5 10 1 .6 0.890

3-5k 2 1000 0.16 286 7000 972 0.904

1 Ok 2 1000 0.02 1 00 20000 534 0.978

Ik 1 100 0.4 100 1000 266 0.835

Ik 1 1 0.004 1 1000 6.9 0.994

00 1 1 0.4 10 1 00 26.6 0.835

The first two lines of table 3 represent the anticipated extremes attainable

in our laboratory. The results of these calculations indicate that it will be

possible to attain sufficient regulation of the sub-microsecond pulse to allow

exploration of nanosecond breakdown phenomena.

To test the feasibility of the above circuit design, a prototype was bull!

to operate in air. Some measurements were performed on the air system, but

because the stray inductances were small, the rise times as calculated above

were faster than the measuring circuit. However, the fall times were as predicted from the above model. Additionally, it was shown that for the pointsphere electrode geometry used in gap 2 (see fig. 16a) it was easy to achieve

breakdown within 200 ns of the time of application of the nanosecond "ise time

pulse

.

Based on the results described above, the construction of a cell f:r

studying liquid nanosecond breakdown was initiated this quarter. The ele

configuration which will first be tested will be the point-sphere geom-try

.

?Q
Small gaps will be required initially since the applied voltage will not exceed

100 kV. The circuit capacitor will be charged by either direct or pulsed

voltage.

Next quarter will see the completion of the nanosecond breakdown cell and

associated inductors to provide a wide selection of pul3e shapes. Attempts will

be made to photograph the temporal development of streamers using an image

converter camera. The liquid used will be transformer oil. Some of our efforts

will concentrate on the initial development of the streamer under high optical

magnification.

For further information contact Dr. R. H. McKnight at (301) 921-3121.

30
6 . REFERENCES

[1] R. H. McKnight and P. M. Fulcomer, "Operation of Ion Counters near High

Voltage DC Transmission Lines, to be published in proceedings, 4th

International Symposium on High Voltage Engineering, Athens, 1983.

[2] W. T. Kaune, M. F. Gillis, and R. J. Weigel, "Techniques for Estimating

Space Charge Densities in Systems Containing Air Ions," J. App. Phys., 54,

p. 6267, 1983.

[3] NBS Report NBSIR 83-2761, Development of Power System Measurements

Quarterly Report, January 1 - March 31, 1983.

[4] R. J. Van Brunt, T. C. Lazo, and W. E. Anderson, "Production Rates for

Discharge Generated SOF2 , SO2F2, and SO2 in SFg and SFg/^O Mixtures,"

Gaseous Dielectrics IV (L. G. Christophorou, ed.) Pergamon Press, New York

(1984) pp. 276-285.

[5] R. J. Van Brunt, "Production Rates for Oxyfluorides SOF2, SO2F2, and S0F 4 in SFfc Corona Discharges," NBS J. Res. (submitted, 1984).

[6] "Development of Power System Measurements—Quarterly Report, January 1 1984

to March 31, 1984," R. Hebner, ed., Nat. Bur. Stand. (U.S.) NBSIR 84-2898

(1984).

[7] R. J. Van Brunt and M. C. Siddagangappa, "Production Rates of Oxygenated

Species in SF5/O2 and SF5 /N2 Corona Discharges," Proc. 37th Gaseous

Electronics Conf., Bull. Am. Phys. Soc. (to be published).

[8] R. J. Van Brunt and W. E. Anderson, "Bibliography of Data on Electrical

Breakdown in Gases," NBS Tech Note 1185 (1984).

[9] K. Masek, L. Laska, V. Perina, and J. Krasa, "Some Peculiarities of the SF b and the SFg + O2 Discharge Plasma," Acta. Phys. Slov., Vol. 33, pp. 145-150

(1983).

[10] R. F. Hampson, "Chemical Kinetic and Photochemical Data Sheets for

Atmospheric Reactions," U. S. Department of Transportation, Federal

Aviation Administration Report No. FAA-EE-80-17 (1980). .

[11] A. C. Cristina and H. J. Schumacher, "The Kinetics and the Mechanism of the

Thermal Reaction between Sulfurtetraf luoride and Fluorine,"

Z. Naturf orsch. , B: Anorg. Chem. , Org. Chem. , Vol. 36B, pp. 1381-1385

(1981).

[12] "Development of Power System Measurements — Quarterly Report,

October 1, 1983 to December 31, 1983," R. Hebner, ed. , Nat. Bur. Stand.

(U.S.) NBSIR 84-2861 (1984).
N8S-U4A (REV. 2 -ao) U.3. OEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR

REPORT NO.

NBbIR 85-311

2. Performing Organ. Report No. 3. Publication Date February ly85

4. TITLE AND SUBTITLE

Development of Power System Measurements

July 1, 1984 to September 30, 1984

Quarterly Report

5. AUTHOR(S)

R. E. Hebner, Editor

6. PERFORMING ORGANIZATION (If joint or other than NBS. see instructions

)

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

7. Contract/ Grant No.

S. Type of Report & Period Covered

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

Department of Energy

Division of Electric Energy Systems

1000 Independence Avenue, SW

Washington, DC 20585

10. SUPPLEMENTARY NOTES

1 1 Document describes a computer program: SF-185, FIPS Software Summary, is attached.

11. ABSTRACT (A 200-word or /ess factual summary of most significant in formation. If document includes a significant

bi bliography or literature survey, mention it here)

This report documents the progress on four technical

investigations sponsored by the Department of Energy and performed by

or under a grant from the Electrosystems Division, the National Bureau

of Standards. The work described covers the period from July 1, 1984

to September 30, 1984. The report emphasizes the errors associated

with measurements of electric and magnetic fields, the properties of

corona in compressed SF gas, the measurement of interfacial phenomena

in transformer oil, and the measurement of dielectric properties on nanosecond time scales

.

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

electric fields; gaseous insulation; interfaces; liquid insulation; magnetic fields;

partial discharges; SF^; solid insulation; transformer oil

13. AVAILABILITY

a Uni imited

1 ' For Official Distribution. Do Not Release to NTIS

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

20402.

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

14. NO. OF

PRINTED PAGES

39

15. Price

38 . 50

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