High Voltage Self Test 2

Question 1

Most common insulation material used in medium voltage cables?

Answer 1

XLPE

Question 2

4 common types of HV cables?

Answer 2

Teck, Concentric Neutral, Shielded Power Cable, PILC

Question 3

A dielectric is more commonly known as an?

Answer 3

insulator

Question 4

What is dielectric strength and what units is it typically stated?

Answer 4

ability of a material to withstand electric stress, volts/mil, KV/in, KV/mm

Question 5

2 types of shielding used on cable?

Answer 5

Strand Shield and Insulation Shield

Question 6

Primary purpose of lead sheathing on a cable?

Answer 6

to keep moisture out

Question 7

Secondary purpose of lead sheath on cable?

Answer 7

provide mechanical protection serving as the mettalic part of the insulation shield, and provide corrosion resistance

Question 8

2 classes of insulation found on medium voltage cable?

Answer 8

100% and 133% on medium voltage cable

Question 9

Function of cable armour?

Answer 9

to protect the cable from mechanical protection

Question 10

What medium voltage cable is the most widely used for heavy industrial applications?

Answer 10

Teck

Question 11

2 functions of the outer concentric conductor on a URD cable?

Answer 11

current carrying neutral and shielding

Question 12

Can a shielded cables insulation-shield metallic tape be used as a return neutral?

Answer 12

NO

Question 13

Where to find ampacities for shielded cables?

Answer 13

IEEE, ICEA tables

Question 14

What factor determines the minimum available AWG size of a HV cable?

Answer 14

The voltage rating of the cable

Question 15

Ampacity of a non shielded cable is based on an ambient temperature of?

Answer 15

30 celsius

Question 16

Ampacity of a shielded cable is based on an ambient temperature of?

Answer 16

40 celsius

Question 17

2 Most common voltage ratings of medium -voltage cables used for power applications?

Answer 17

15KV and 25 KV

Question 18

All cables rated over what require an insulation shield?

Answer 18

5KV

Question 19

2 Types of stress relief used in medium voltage cables?

Answer 19

Geometric and Capacitive

Question 20

Class 1 termination according to the IEEE must have what features?

Answer 20

Stress relief, Anti tracking, seal to the environment or from the environment

Question 21

Cable used indoors or attached to buildings outdoors must be enclosed in what?

Answer 21

metal conduit in enclosed busways

Question 22

Why must shielding be removed an adequate distance when terminating a cable?

Answer 22

to minimize leakage currents

Question 23

Is it permissable to run HV and LV cables in the same cable tray?

Answer 23

Yes as long as sheet steel barrier separates them

Question 24

All associated non- current carrying metal parts that house HV cables must be?

Answer 24

Grounded

Question 25

All cables above what voltage require shielding?

Answer 25

5000 Volts

Question 26

Why must cables be adequately secured at frequent intervals?

Answer 26

to prevent movements due to magnetic fields caused by excessive currents

Question 27

What type of medium voltage cable requires a pothead termination?

Answer 27

PILC, Paper insulated lead covered cable

Question 28

Why is it neccessary to lubricate the stress cone before installation?

Answer 28

It is friction fit will not go on otherwise

Question 29

What kind of tape is anti tracking?

Answer 29

Silicone

Question 30

Why are outdoor terminations of the skirting type?

Answer 30

to increase creepage distance

Question 31

Why must insulation be pencilled if the end is to be sealed with tape?

Answer 31

to avoid trapping air that can become ionized

Question 32

Some reasons of why a HV splice may fail prematurely?

Answer 32

-poor workmaship -ingress of moisture -tracking due to contaminents on insulation -temperature fluctuations due to poor electrical contact