ARC

Question 1

Is a complex, safety-related procedure, and should be done only under the direction of experienced engineers

Answer 1

The Calculation of Actual Values for Specific Field Conditions

Question 2

ANSI

Answer 2

American National Standards Institute

Question 3

IEEE

Answer 3

Institute of Electrical and Electronics Engineers

Question 4

“A discharge of electricity through a gas, normally characterized by a voltage drop in the immediate vicinity of the cathode approximately equal to the ionization potential of the gas.”

Answer 4

ARC

Question 5

The heat and light energy release that is caused by the electrical breakdown of and subsequent electrical discharge through an electrical insulator such as air.

Answer 5

ARC

Question 6

Occurs when a substantial amount of electric current flows through what previously had been air

Answer 6

ELECTRIC ARCING

Question 7

air is a poor ____

Answer 7

CONDUCTOR

Question 8

Since air is a poor conductor, most of the current flow is actually occurring through the vapor of the arc terminal material and the ionized particles of air. This mixture of super-heated, ionized materials, through which the arc current flows, is called a ____.

Answer 8

PLASMA

Question 9

Arc energy is released in at least three forms

Answer 9

 Light
 Heat
 Mechanical

Question 10

Also note that mechanical injuries are usually categorized as ___, even though the ultimate cause is the _____.

Answer 10

BLAST INJURIES, ELECTRIC ARC

Question 11

Principally eye injuries, although severe burns can also be caused if the ultra violet component is strong enough and lasts long enough

Answer 11

LIGHT

Question 12

Severe burns caused by radiation and/or impact of hot objects such as molten metal

Answer 12

HEAT

Question 13

Flying objects as well as concussion pressures

Answer 13

MECHANICAL

Question 14

Are the subject of many on-going studies

Answer 14

The quantitative effects of electric arc

Question 15

Is a function of the total arc energy, the distance of the subject from the arc, and the cross-sectional area of the individual exposed to the arc

Answer 15

An individual’s exposure to arc energy

Question 16

Several major factors determine the amount of energy created and/or delivered by an electric arc. (12)

Answer 16

DISTANCE
TEMPERATURE
ABSORPTION COEFFICIENT
TIME
ARC LENGTH
CROSS-SECTIONAL AREA OF BODY EXPOSED TO THE ARC
ANGLE INCIDENCE OF THE ARC ENERGY
ARC INPUT
ARC VOLTAGE
ARC SURFACE AREA
INCIDENT ENERGY

Question 17

Ralph Lee has predicted that the heat energy received by an object (or worker) can be calculated

Answer 17

The Lee Method

Question 18

The amount of damage done to the recipient diminishes by approximately square the distance of the arc. Twice as far means one-fourth the damage.

Answer 18

Distance

Question 19

The amount of energy received is proportional to the difference between the fourth power of the arc temperature and the body temperature.

Answer 19

Temperature

Question 20

The ratio of energy received to the energy absorbed by the body.

Answer 20

Absorption Coefficient

Question 21

Energy received is proportional to the amount of time that the arc is present.

Answer 21

Time

Question 22

The amount of energy transmitted is a function of the arc length. For example, a zero will transmit zero energy. Note that for any given system, there will be an optimum arc length for energy transfer.

Answer 22

Arc Length

Question 23

The greater the area exposed, the greater the amount of energy received.

Answer 23

Cross-Sectional Area of Body Exposed to the Arc

Question 24

Energy is proportional to the sine of the angle of incidence. Thus, energy impinging at 90-degree is maximum.

Answer 24

Angle of Incidence of the Arc Energy

Question 25

The energy supplied to an electric arc by the electrical system

Answer 25

Arc Input

Question 26

Research has shown that electric arcs are rarely perfect _____

Answer 26

Sinusoids

Question 27

is somewhat more difficult to determine. Values used in power system protection calculations vary from highs of 700 V/ft (214.4 V/m) to as low as 300 V/ft (91.4 V/m).

Answer 27

Arc Voltage

Question 28

Arc voltages start __ and tend to ___. Periodically, the arc voltage will drop if the arc lasts long enough.

Answer 28

low, rise

Question 29

Arc voltage is _____ to arc length. Therefore, arc power and energy are proportional to arc length.

Answer 29

proportional

Question 30

The single most important of all arc energy calculations is the one that determines the energy transfer from the arc to the nearby body.

Answer 30

Incident Energy

Question 31

This information can be used to determine the necessary level of protective clothing required, and can also be used in the performance of a risk analysis.

Answer 31

Incident Energy

Question 32

_____ causes painful trauma to the outer layers of the skin. Little permanent damage results from a first-degree burn because all the growth areas survive. Healing is usually prompt and leaves no scarring.

Answer 32

First Degree Burning/Burn

Question 33

_____ result in relatively severe tissue damage and blistering. If the burn is to the skin, the entire outer layer will be destroyed. Healing occurs from the sweat glands and/or hair follicles.

Answer 33

Second Degree Burning/Burn

Question 34

_____ result in complete destruction of the growth centers. If the burn is small, healing may occur from the edges of the damaged area; however, extensive third-degree burns require skin grafting.

Answer 34

Third Degree Burning/Burn

Question 35

Has yielded a slightly different result based primarily on empirical results. Using an experimental setup, the researchers measured energy received from an electric arc at various distances. The arc was created using a 600-V source, and different configurations were used to simulate a completely open-air arc versus the so-called “arc-in-a-box.” Using these experiments, they developed two equations to model the amount of energy received.

Answer 35

Research by Bingham and others

Question 36

While the actual shape of an electrical arc may vary, all classic, realistic solutions start by assuming that an arc causes an approximately cylindrical plasma cloud with length L and radius r. This cylindrical structure will have a lateral surface area equal to 2πrL.

Answer 36

Arc Surface Area