Ch. 20 Electrical Fires and Emergencies

Question 1

Water had pressure, friction loss and flow rate:

Answer 1

Pressure = volts (electromotive force OR electrical potential difference)
Friction loss = ohms (resistance)
Flow rate = amperes (amps)

Question 2

Resistance occurs due to ___________.

Answer 2

The material of the conductor

Question 3

_______ does not permit electricity to flow because there is a break in the circuit wire.

Answer 3

Open circuit

Question 4

When an electrical circuit’s normal path has been INTERRUPTED, it becomes _________ , permitting current to flow through a path it was not intended to travel.

Answer 4

A short circuit

Question 5

Wiring installed by _________ that permits electricity to flow back into THEIR system and then into the earth is called:

Answer 5

Utility companies, Utility ground

Question 6

Many rubber and plastic compounds are

Answer 6

Poor conductors

Question 7

Firefighting boots, either rubber or leather, are ___________ however, because of many other compounds they contain.

Answer 7

Not good insulators

Question 8

Most electricity is produced by ______, in facilities that use fuel as sources of energy (____, ______, _____, or ______). Electricity is generally produced at ___________.

Answer 8

Generators
Coal, oil, gas or nuclear
13,000 volts

Question 9

Upon leaving generating stations, electricity travels through transformers that:

Answer 9

Increase it’s voltage to 138,000-345,000 volts

Question 10

(Voltage) Stepping down done in several stages, in different locations: (4)

Answer 10

Substations
Underground transformers
Pole-mounted transformers
Transformers inside buildings

Question 11

Most IMPORTANT thing for firefighters to be aware of in regard to the TRANSMISSION system is:

Answer 11

High-voltage wires on poles ARE NOT insulated.

** also true of buss bars (bus bars) in OUTDOOR SUBSTATIONS***

Question 12

Once at the point of distribution, other transformers reduce the voltage to:

Answer 12

4,000-33,000 volts

Question 13

Electricity is then fed through a grid of cables/transformers that take it right to the customers door. On the way, the voltage is:

Answer 13

Further stepped down to 120 or 240 volts normally used in the home or the office

Question 14

_____ is moving force that travels through solid, liquid, and gaseous materials in the form of electron transfer from one molecule to another.

Answer 14

Electricity

Question 15

Economy of high-voltage transmission uses ________ between lines instead of _______. Distance is _______.

Answer 15

An air gap
Insulation
Protection

Question 16

It would be _______ to state that the larger the line, the higher the voltage.
In some cases, a larger transmission line carries _____ voltage than a small one
- depending on ______ and its ____________.

Answer 16

Inaccurate
Less
-the type of metal
-conductive capability

Question 17

Two main hazards with electricity:

Answer 17

Electrocution

Burns

Question 18

_______ flows through the body, either due to high-voltage or low resistance, cause ______.

Answer 18

High voltage

Rapid death

Question 19

Amount of ________ through the body to produce injury or death is __________.

Answer 19

Current flow

Very, very small

Question 20

_____ and _______ are important factors that help determine whether a person survives a contact with electricity.

Answer 20

Size of contact point

Path electricity takes through the body to ground

Question 21

Electrocution is affected by several variables: (5)

Answer 21

• amount of current
• size on contact point
• path to enter/exit the body
• duration of current flow
• condition of skin (wet, dry, broken)

Question 22

It is usually the presence of _____ or ________ that triggers the response of firefighters.

Answer 22

An arc

The result of it

Question 23

________ is one very common occurrence of such static arcing

Answer 23

Lightning

Question 24

______ is the result of current being dissipated to ground as it travels from a source, such as downed high voltage wire.

Answer 24

Voltage gradient

Question 25

Carries vary in voltage potential, depending on the stage of transmission:

Answer 25

Transmission line = exceed 8,000 volts Distribution line = potentials of 601-8,000 volts Low-voltage potentials = up to and include 600 volts

Question 26

System for distribution of electricity includes a combination of transformers with ___________, arranged in __________

Answer 26

High and low-power carriers | Series and parallel grid systems

Question 27

In most power generation plants, the ______________ has access to emergency operations cabinet (station diagrams, system/relay drawings, log books, current list of all equipment containing PCB's)

Answer 27

Watch general supervisor

Question 28

Charts that show emergency posts and jobs for all staff can in large plants number more that ______.

Answer 28

100 people

Question 29

Transformer is atop a pole, make no attempt to extinguish fire unless:

Answer 29

- exposes cross-members | - could result in wire breakage

Question 30

``` Transformer atop a pole: If necessary to extinguish, use a fog or foam stream, or dry chem extinguisher. It is essentially a confined class B-type fire, use reach of hose stream, outside safety zone and: ```

Answer 30

- at least 25 ft from energized equipment | - 40 ft if using SOLID streams or foam nozzles on OTHER THAN SPRAY PATTERN

Question 31

In many urban areas, the most frequent response to electrical emergencies is to:

Answer 31

Manhole fires

Question 32

Explosive range of CO

Answer 32

12-75%

Question 33

Manhole fire: Checking adjacent bldgs for extension of fire through conduits, what indicates possible fire extension?

Answer 33

Heat in the fuse service panel

Question 34

Current flowing through these unintentional conductors (metal objects with no house ground) can be as large as what the building service carries:

Answer 34

Hundreds of AMPS

Question 35

Exposed wires at the base of a lamp post contain upward of:

Answer 35

277 volts *notify utility last after taping wires and taping off area*

Question 36

DANGER AREA for downed wires is defined as area in ALL directions that is at least:

Answer 36

As large as the length of the wire in question

Question 37

First tactical consideration is to define the perimeter of the operation by establishing a safety zone that is:

Answer 37

One full span greater than the affected span.

Question 38

Although ______, ______, and ______ are all useful tools for lifesaving purposes, you SHOULDN'T rely on them.

Answer 38

- Lineman's gloves - Sleeves - Mats

Question 39

Visual hints-overheated ballasts *intact bulbs*

Answer 39

``` Bulbs glowing faintly Look at fixtures for defects -dark colored oil on outside of fixture/light diffuser Dark smudge around vents Last resort, feel each fixture -defective unit will be hot ```

Question 40

Life-threatening condition - lines on a car and no hot stick *cannot be used during rainy/damp weather*

Answer 40

``` Dry rope 1st throw under 2nd over Far side retrieves and walks backward *presence of spilled gasoline may remove this option* ```

Question 41

Although it is true that the level of _______ does the damage, current passing through a body requires adequate _______ to cause the amps to flow.

Answer 41

Amperage | Voltage

Question 42

The presence of _______ is usually, if not always, accompanied by _______.

Answer 42

High voltage High amperage *high voltage doesn't do the damage, but what accompanies it does*

Question 43

Many utilities refer to anything ________ as low voltage.

Answer 43

LESS than 600V

Question 44

When electricity has performed its function at the appliance or light bulb, it returns to its source via __________.

Answer 44

A return wire

Question 45

The larger the ______, the higher the _____ is a valid indicator.

Answer 45

Insulators | Voltage

Question 46

In high voltage conductors, the current can jump _______, depending on _____, _____ and _________.

Answer 46

3 ft or more Moisture content of the air Electrical potential Type of conductor

Question 47

Fire departments are most often concerned with areas of the distribution system where changes in ______ are made, such as _____, _____ or in __________ that are found in manholes or overhead structures like utility poles.

Answer 47

Voltages Substations Transformers Junctions of cables

Question 48

Electricity-related fires and emergencies- Safety is paramount. The tactical position is ________ until ________. The need for ______ is rare and only justified if human life is at stake. Our concern is the protection of ______.

Answer 48

Generally a Defensive one Power is shut down Offensive tactic Exposures

Question 49

In a generating station, water heated, turning it to steam at over _______. Accompanied by _________ and a ___________.

Answer 49

400 psi Tremendous shrieking Cloud of condensing water vapor

Question 50

Generators are cooled with _________, a lighter than air gas __________ that it often ignites immediately in the event of a leak. When it burns, it is with a __________.

Answer 50

Hydrogen Highly flammable Very pale flame, nearly invisible

Question 51

Actions to be taken- | Inside generating station:

Answer 51

Do not enter until rep arrives unless human life in jeopardy Stretch a line to standpipe/sprinkler but do not enter No metal tools No ladders, even wood, supported by metal superstructure Fog tips

Question 52

Transformer fire:

Answer 52

Class B-oil fire Up to 20,000 gallons All oil presumed to have PCBs (breaks down to dioxin/dibenzofurans) Do not begin overhaul until advised by utility of nature of oil

Question 53

Manhole fires | Rumbling noise we hear at manhole fires is ________.

Answer 53

Ongoing electrical arc Variety of high/low voltage but relatively few transformers Large amounts of CO/HCL when gases contact mucous membranes Less lethal dose of CO with HCL *Transformers found in vaults with square/rectangular covers*

Question 54

Signs of open ground: | What to do:

Answer 54

Dimming of lights/presence of sparks at contact point of metal objects/overheating of building's electrical wires Open individual breakers/circuits, reducing load Handlines Notify utility

Question 55

Downed line can be ____, ____ or ______.

Answer 55

Dancing, arcing or just lying still

Question 56

Trained FF may use a properly tested ______ to remove wires from direct contact with a ______ or ______. Secure the hot stick around the wire by placing the clamp ______ the wire and twisting the body of the stick __________.

Answer 56

Hotstick Victim or vehicle Under Clockwise

Question 57

If necessary to cut the line, secure the wire with a _____ or a __________ objects such as __________. Tingling sensation is an indication of ________ and imperative _______ before any further action.

Answer 57

Hot stick Heavy, nonconductive Long, dry, wooden boards Voltage gradient Power be shut down

Question 58

Wire over car with people in it (3 scenarios)

Answer 58

Driver can move vehicle, drive it out from under wire Vehicle can't move, no life-threat, do not remove occupants Fire threatens occupants, jump clear of vehicle *stretch 1 3/4 in. with fog*

Question 59

Ballasts Older types, often ______. Should wear _____. Thermal imaging cameras or other types of ____________ devices can be used. Without a _________, must physically inspect each fixture.

Answer 59

PCB's, SCBA. Heat scanners Heat scanner

Question 60

Electrical fire are common occurrence. To locate source, consider __________________. It often pays to ___________.

Answer 60

Where SMELL was first detected | Leave power on until source is located