High Voltage

Front 1

two things HV transmission is based on

Back 1

load and distance

Front 2

primary distribution systems use what voltage

Back 2

medium voltage

Front 3

utilization voltages

Back 3

120 208 347 600

Front 4

generator voltages

Back 4

10 to 20kv

Front 5

transmission voltages

Back 5

60 to 765 kv

Front 6

transmission voltages cable

Back 6

steel cored aluminium

Front 7

electro static field

Back 7

invisible field of force that surrounds energized conductors

Front 8

electro static field causes 5 things

Back 8

electric stress

voltage gradient

ionization and corona

strike distance and flashovers

creepage distance and tracking

Front 9

electric stress

Back 9

stress on insulation ability to block current reduced

Front 10

voltage gradient

Back 10

concentric lines of force that diminish as they get farther from conductor

Front 11

ionization and corona

Back 11

ionization turns air into conductor

corona is a voltage that causes air insulation to break down

Front 12

strike distance and flashovers

Back 12

minimum required separation of lines before flashovers

flashover arc between lines

Front 13

creepage distance and tracking

Back 13

tracking current that moves along a surface

creepage distance : distance over surface sufficiently long

Front 14

what are impulse voltages

Back 14

sudden high voltages die to lightening arcing and faults

Front 15

BIL

Back 15

basic insulation level, ability of insulation to withstand short high voltages

Front 16

HV ANSI breaker designation

Back 16

52

Front 17

radial distribution system

Back 17

simple cheap poor maintenance

Front 18

ring or loop system

Back 18

more reliable than radial more expensive

Front 19

network system

Back 19

most reliable most expensive

Front 20

substation

Back 20

outdoor compound for HV one small building for weather sensitive stuff

Front 21

Unit substation

Back 21

indoor factory made in customers building for large industrial consumers

Front 22

window in unit substation

Back 22

to be able to see isolation switch

Front 23

vault

Back 23

room in building specially constructed for electrical service equipment

must be made of concrete

doors made of steel

floors provide drainage if oil TX present

not located where gas or water or sewer enter building

Front 24

lightening arresters

Back 24

normal voltage high R high transient voltage low R fault goes to ground.connected in parallel one required for each phase

Front 25

series reactor

Back 25

series connected used to limit fault current uses CEMF

Front 26

instrument TX

Back 26

reduces current and voltage for metering

Front 27

voltage TX current TX

Back 27

usually 120v

and 5a connected in series ratio 115 to 125 percent of primary flag

Front 28

key interlocking

Back 28

system that prevents energized work on equipment

Front 29

Lbs

Back 29

load break system can be opened under load

Front 30

non lbs

Back 30

switch can't be opened under load

Front 31

safe switching procedure

Back 31

disconnect

test

ground and short wires

screen off neighboring live parts

Front 32

limit of approach

small

medium

large

Back 32

minimum safe distances can approach HV

751 to 75m 3m

75k to 250k 4.5m

over 250k 6m

Front 33

step voltage

Back 33

difference in voltage between one foot and the other during step

Front 34

touch voltage

Back 34

difference in voltage between touch point and feet most deadly

Front 35

ground mat

Back 35

mat made from conductors keeps feet at same potential

Front 36

medium voltage cables

Back 36

paper insulated lead sheathed

xlpe

concentric neutral

pvc

Front 37

dielectric strength

Back 37

ability of dielectric to withstand electrical breakdown under voltage

Front 38

temp effect on dielectric

moisture effect on dielectric

Back 38

more temp less strength

moisture will decrease strength

Front 39

types of insulations

Back 39

xlpe: widely used high moisture resistance

plastic: thermoplastic susceptible to heat thermoset less susceptible

Front 40

strand shield ?

needed on cables over?

Back 40

semiconductor shield around condoctor cables over 1000v need it allows even escape of electrostatic field

Front 41

insulation shield

Back 41

makes flux lines uniform

suppresses radio and tv interference

protects life in event of mechanical damage. evenly distributes flux to ground

Front 42

sheath grounding

Back 42

mist be grpunded or Wil carry a charge

grounded at only one end will leave dangerous voltage at other

grounded at both ends Wil make it act as current carrying conductor

Front 43

insulation levels percentage

Back 43

most HV 100 percent grounded 133 percent ungrounded

Front 44

concentric neutral cable

Back 44

alsp called URD (underground residential distribution) metallic shield Carey's as much current as conductor .very common

Front 45

sheilded cable

Back 45

metallic parts have no ampere rating used in power application. conductor is covered in semiconductiong shield

Front 46

teck cable shielded above ?

common?

Back 46

widely used

above 5k all shielded

Front 47

cable current rating based on

Back 47

current and voltage

Front 48

two common types of cable stress relief

Back 48

geometric and capacitive

Front 49

describe geometric termination

Back 49

stress cone uses to build up insulation in area of high electric stress

Front 50

describe capacitive

Back 50

two dielectrics (of hi k ) in series to redistribute electric stress

Front 51

termination classes 1 2 3

Back 51

class 1 outdoor stress relief anti tracking

class 2 anti tracking and stress relief

class 3 stress relief

Front 52

most common failure of HV cable at?

Back 52

termination

Front 53

pothead termination usually on cable ?

Back 53

paper insulated lead sheathed

Front 54

splice failure likely if

Back 54

shields not back in place

not water tight

air gets trapped

Front 55

outdoor switch gets available upto

Back 55

800kv

Front 56

metal clad switch gear

Back 56

removable CB

Front 57

metal enclosed

Back 57

non removable CB

Front 58

types of switch ratings switches are rated on

Back 58

design voltage higher than rated

rated voltage usually be seeing

BIL several times nominal

Front 59

types of switches

Back 59

LBS

non LBS

isolating

horn gap

disconnect

Front 60

isolating switch

Back 60

non lbs designed to isolate system see through window

Front 61

horn gap switch

Back 61

LBS common for residential areas. for small load currents 15a

Front 62

disconnect switch

ampunt of current allowed to break switch

Back 62

non LBS can open with negligible current less than .5 amps provides visible isolating device

Front 63

HV fuse voltage ratings

Back 63

up to 161kv

indoor 34.5

medium voltage 2.4 to 69

Front 64

two categories of fuses

Back 64

distribution cut out most common

power fuses

Front 65

HV fuses also classified as

Back 65

expulsion

non expulsion

Front 66

4 types of fuses

Back 66

current limiting

solid material

liquid filled

distribution cut out

Front 67

current limiting fuse

for what voltage

Back 67

non expulsion type. very fast contains silica sand for medium voltage

Front 68

solid materials fuse

features

Back 68

expulsion uses boric acid needs muffler indoors has spring drop out type for distribution

Front 69

liquid filled fuse

Back 69

oil filed use spring and oil to extinguish

Front 70

distribution cut out

Back 70

expulsion most common on OH lines. visible low chance of restrike

Front 71

CBs categorized by

Back 71

method of quenching arc

Front 72

CB rating based on

two ratings CBs have

Back 72

voltage current frequency

continuous and interrupting rating

Front 73

5 types of CBs

Back 73

air magnetic

vacuum

oil type

air blast

sulphur hexaflouride

Front 74

air magnetic cb

Back 74

up to 15kv

blow put coils

cooling baffles

puffer device blows air to extinguish arc

medium voltage

Front 75

vacuum cb

Back 75

medium voltage uses vacuum chamber quickly extinguish arc takes up less space very effective 6-25mm

Front 76

oil cb

Back 76

bulk oil:old leakage flammable

minimum oil:less oil forced at high pressure across arc

medium voltage

Front 77

air blast CB

Back 77

uses compressed air blows into arc

Front 78

sulphur hexaflouride

Back 78

chemical with dielectric strength high cost

medium voltage

Front 79

common types of relay action

Back 79

fulcrum

electromagnet

solenoid

Front 80

types of relays timings

Back 80

instantaneous

time delay

combination

Front 81

numbered protective designations

Back 81

50 instantaneous oc relay

51 time trip voltage oc relay

52 ac circuit breaker

Front 82

differential relay

Back 82

protects against ground faults and line to line relays

Front 83

voltage relays

Back 83

if voltage fluctuates it trips

Front 84

what is dielectric absorption loss

Back 84

occurs in insulation of cable when disconnected electrons leak from dielectric back into conductor

Front 85

fuses rated on

Back 85

voltage current and interrupting current

Front 86

CB 3 poles mounted on common support for

Back 86

medium and low voltage

Front 87

CB mounting for high voltages

Back 87

each without own pole

Front 88

power supply for CB

Back 88

PT or a.c. or dc standby source

Front 89

air magnetic voltage rating

Back 89

medium up to 15kv

Front 90

vacuum CB voltage rating

Back 90

medium voltage

Front 91

air blast CB voltage rating

disadvantages

Back 91

high and extra high

loud lots of maintenance

Front 92

describe recloser

what kind of CB

how many times does it reclose

Back 92

autmatically recloses after imteruppting current

uses sf6 or oil type

usually 3 attempts

Front 93

most common reasons for termination failure

Back 93

mechanical damage

poor handling of termination

Front 94

what effect does ozone have on insulation

Back 94

breaks it down

Front 95

high voltage portable cables made of what type of material

Back 95

Pe pvc

Front 96

what happens of Electric stress able to flow through air spaces

Back 96

ozone accumulation