Dielectric Phenomena in High Voltage Engineering (1915) — part 12 of 12

between concentric cylinders 13, 29

between large spheres 26

between parallel planes 29

between parallel wires 23, 26

equigradient surfaces 222

law of visual corona, see Visual corona 38 e( seq.

Guard rings 223

H

High frequency, effect of, in design 177, 226

effect of, on corona loss 162

effect of, on oil 184, 165

effect of, on solid insulation 177, 184, 187

effect of, on spark-over of sphere gaps 106, 106

loss in solid insulation 187

INDEX 261

Paqs

Hysteresis, dielectric 36, 37, 166, 185

I

Images 234

Impulse ratio 108

Impulse voltages, effect of, on air 108

effect of, on spark-over in oil 162, 165, 187

effect of, on solid insulations 177, 184, 187

measurement of 108

Insulation, breakdown caused by the addition of 213

Insulation, breakdown, how measured 12

Insulation, solid, area of electrode 175

barriers in oil 189

breakdown caused by addition of 213

common 166

comparison of breakdown in oil and in air 170 el seq,

comparison of strengths for impulses, oscillations,

high frequency and low frequency 184

cumulative effect of overvoltages of short duration. . 178

effect of d.c. on 191

effect of impulse voltages and high frequency

on 177, 184, 187

energy loss in 185

high frequency loss in 187

hysteresis 166

impregnation of 190

laminated 175

law of energy loss in 185, 187

law of strength vs. thickness 174, 237

law of strength vs. time 178

mechanical 190

methods of testing 170 ei aeq.

occluded air in 236

operating temperatures of 188

permittivity of 179

strength under high frequency 184

strength under impulses 177, 184

strength under oscillations 184

strength vs. thickness 174

strength vs. time 178

tables of properties of 180, 184

Insulations, air 38, 79, 117

compressed air 42

gaseous 38, 79, 117

liquid 183

oil 183

solid 166

17

262 INDEX

Paob Insulators, effect of altitude on spark-over of Ill

L

Lead, see Bushing.

Lines of force, construction of 226

equation of, between parallel wires 18

equation of, for spheres 25

equation of, three-dimension field 232

perpendicular to equipotential surface 20

Liquid insulations, see Oil.

M

Magnetic field, analogy with dielectric field 2

experimental plot of 2

N

Needle gap 87

effect of humidity on 88

spark-over in oil 164, 156

spark-over voltage in rain 105

O

Oil, barriers in 161, 189

corona in 156

corona and spark-over in 153

effect of moisture in 154

effect of temperature on , 155

formulsB for strength of 159, 161

high frequency in 165

law of spark-over and corona 159, 161

needle gap spark-over in 166

permittivity of 155

physical characteristics of transil oil 153

spark-over for different electrodes in 154

specific resistance in 155

surface leakage in 188

transient voltages in 162, 184

Oscillations, effect of, on solid insulations 177, 184

effect of, on sphere-gap voltages 105

measurements of 105, 108

P

Permittance or capacity, between concentric cylinders 13, 29

between concentric spheres 25

INDEX 263

Paob

Permittance or capacity, between eccentric spheres 29

between parallel planes 10, 29

between parallel wires 22, 29

comparison of single phase and three phase . . 235

effect of ground on for parallel wires 223

formulee for different electrodes 29

in series 12

Permittivity 11

of oil 156

of solid insulations 179

Planes, parallel, flux density 10, 11

gradient 10

permittance or capacity of 10

spark-over in oil 157

Potential at a point 14

Potential difference between two points 14

Potentials, addition of 14

Problems, breakdown caused by addition of stronger insulation 213

bushing 220

condens^r bushing 220

dielectric field construction of 226

dielectric field control 223

dielectric field experimental determination of 232

dielectric field in three dimensions 232

effect of ground on dielectric field between parallel wires 234

entrance bushings 217

general problems on the calculation of spark-over of parallel

wires, insulation loss, strength, etc 236

graded cable 218

high frequency 225

static, on generator coils 216

three-phase dielectric field for flat and triangular spacings . . 234

S

/

Spark-over, condition for spark or corona 27, 79, S4

effect of altitude on, for bushings, insulators 111,217

effect of altitude on, for spheres 95

effect of water and rain on 105

for needle gap 87

for parallel wires 79

for spheres 88

gaps used in measuring high voltage 87

influence of water and oil on 86

in oil 186

Specific resistance, of oil 155

of solid insulation 167

264 INDEX

Paqe

Spheres, air films between 68

as a means of measuring high voltage 88, 101, 103, 104

concentric permittance, dielectric field 25

corona or spark-over for 58

effect of ground on spark-over voltages 104

effect of water and rain on arc-over voltages 105

experimental determination of effect of altitude 95

law of disruption 63

law of spark-over in air 63

law of spark-over in oil 159, 161

precautions against oscillations 101

rupturing gradients for different sizes 62

spark-over at high frequency, oscillations and impulses 108

spark-over calculation of 92, 93

spark-over calculation of, correction for altitude 93

spark-over curves S9 ei seq.

spark-over curves at small spacings 60

strength of oil around 161

two large equal spheres, field between gradient, permittance, etc . 26

two small equal spheres 28

Steep wave front 105, 108, 162, 177, 184, 187

Surface leakage, air 189, 190, 221

oU , 188

Symbols, table of xill

Testing, method of testing solid insulators 170 el seq.

Three-phase dielectric fields between conductors with flat and triangu- lar spacings 238

Transformer, bushing , . . . 232

condenser bushing 220

oil-filled bushing 232

voltage rise due to high frequency testing 225

voltage rise due to spark-over 102

Transmission lines, agreement of calculates and measured corona losses . 208

corona limit of voltage on, with working tables .... 210

corona on 199

practical example of corona loss calculation 205

practical formulse and their application 203

practical method of increasing size of conductors . . . 207

safe and economical voltages 207

three-phase, comparison of permittance with single- phase 234

three-phase, with triangular and flat spacing . . 234, 235

spark-over voltage of 83| 237

voltage change along lines 208

INDEX 265

Paob U

Units, table of xi

V Visual corona, see Corona.

W

Weather, effect of, on corona loss 145, 146, 149

Wires, calculation of spark-over on, wet and dry 237

calculation of visual corona on, wet and dry 237

corona loss on 117, 199, 238

effect of ground on permittance or capacity and gradient 233

equation of equipotential surfaces 14, 16

equation of lines of force 18

experimental plot of field between 2, 232

flux density 14

gradient 23, 29

law of spark-over and corona in oil .159

lines of force 14

method of drawing dielectric field for 226

permittance or capacity 22, 29

spark-over 79

spark-over, wet 86

visual corona, see Visual corona 38 e< <eg.

X

X-rays 196