High Voltage

Question 1

Creepage

Answer 1

Conduction of HV across the surface of an insulator, made worse by wet & dirty conditions.

Question 2

Skirting

Answer 2

This design feature of an insulator keeps ‘tracking’ low, making it harder to reach ground.

Question 3

High Voltage

Answer 3

A voltage of 235 kV would be classified as this type of voltage.

Question 4

Extra High Voltage

Answer 4

The highest transmission voltage we have is 500 kV in this province. We call this _____ voltage.

Question 5

Corona

Answer 5

Ionized air or current flows between conductors and grounded equipment. violet coloured arc hissing sound and smell of ozone

Question 6

Medium voltage

Answer 6

This is any voltage found between 2.4 kV and 69 kV on our city streets.

Question 7

Voltage Gradient

Answer 7

Electrical stress will be greater the closer you get to the HV conductor. Move away and this stress becomes less. What do we call this?

Question 8

BIL Basic impulse level

Answer 8

This rating on HV equipment indicates the level of lightning strike (surge) that equipment can withstand safely. transient voltage

Question 9

Flashover

Answer 9

When HV ionizes enough air, we know it has this ability. which is basically unintended electrical discharge

Question 10

Electric Stress

Answer 10

stress on valence electrons in the insulation, this force can weaken the bonds in the atom which can cause current flow in the insulation

Question 11

Ionization

Answer 11

as the air breaks down and becomes the conductor/ air is relatively a weak conductor

Question 12

Strike distance

Answer 12

minimum distance between energized components, other energized components, or grounded components

Question 13

HV service equipment includes

Answer 13

CB, swtiches, fuses, disconencting means, isolation swtich

Question 14

Radial supply system

Answer 14

cheapest, simplest, least reliable, only one overhead cable/line common in rural areas

Question 15

Ring/loop system

Answer 15

locality is supplied from 2 directions, offers greater degree of protection 2 feeders comes with risk of back feeds

Question 16

Network/grid system

Answer 16

-ring/loop system with with extra interconnecting ties
-power can be delivered by several differnt loops
-most expensive and requires more complex protective relaying

Question 17

Substation

Answer 17

outdoor containing electrical service equipment

Question 18

Unit substation

Answer 18

inside if only less then 13.8KV for HV service equipment for large industrial/commercial customers

Question 19

Electric Vault

Answer 19

made to house electrical service equipment
-made typically of concrete with one outside wall
-lockable steel doors, complete with steps or a door sill
-floor drainage

Question 20

Lightening Arrestors

Answer 20

Divert over voltage on the HV lines and take it to the ground very quickly

Question 21

Current limiting reactor/series reactor

Answer 21

Limits current spike/ coil of wire connected in series on HV systems to choke fault current

Question 22

Pre switching and post switching procedures

Answer 22

-disconnect
-lockout
-testout
-ground and short circuit
-screen off neighboring live parts

Question 23

What is the minimum distance to work around HV lines?

Answer 23

10 FT

Question 24

Define Dielectric Strength

Answer 24

the ability of a material to withstand electrical breakdown caused by voltage

Question 25

What are some considerations for types of dielectrics?

Answer 25

Cost, Mechanical Strength, Thermal conductivity, Moisture resistance, Flexibility, Mass

Question 26

What are some types of dielectrics?

Answer 26

Plastic, PVC, PE, PILC, Synthetic Rubber

Question 27

Examples of plastic Dielectrics?

Answer 27

Thermoplastic(T), Thermoset(R),XLPE- cross-linked polyethelene

Question 28

Identify 2 types of shielding?

Answer 28

Strand(conductor) shield, Insulation shield(semicon)

Question 29

Define Damper in terms of HV lines

Answer 29

its a mechanical counterweight in an effort to prevent line galloping

Question 30

Generation voltages

Answer 30

10-20KV

Question 31

Define lightning protector

Answer 31

Feature on overhead HV towers that attracts lightning strike nd prevents it from hitting the steel conductors

Question 32

Define swtichyard

Answer 32

Fenced area with no power transformer, but ties HV busbars together

Question 33

HV insulators are often made of this material

Answer 33

Glass

Question 34

How is a lightning arrestor to be installed in relation the equipment it protects

Answer 34

Parallel

Question 35

Safety feature on HV unit subs to protect workers

Answer 35

Key interlock