Flashcards in Ch. 20 Electrical Fires and Emergencies Deck (60):
Water had pressure, friction loss and flow rate:
Pressure = volts (electromotive force OR electrical potential difference)
Friction loss = ohms (resistance)
Flow rate = amperes (amps)
Resistance occurs due to ___________.
The material of the conductor
_______ does not permit electricity to flow because there is a break in the circuit wire.
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.
A short circuit
Wiring installed by _________ that permits electricity to flow back into THEIR system and then into the earth is called:
Utility companies, Utility ground
Many rubber and plastic compounds are
Firefighting boots, either rubber or leather, are ___________ however, because of many other compounds they contain.
Not good insulators
Most electricity is produced by ______, in facilities that use fuel as sources of energy (____, ______, _____, or ______). Electricity is generally produced at ___________.
Coal, oil, gas or nuclear
Upon leaving generating stations, electricity travels through transformers that:
Increase it's voltage to 138,000-345,000 volts
(Voltage) Stepping down done in several stages, in different locations: (4)
Transformers inside buildings
Most IMPORTANT thing for firefighters to be aware of in regard to the TRANSMISSION system is:
High-voltage wires on poles ARE NOT insulated.
** also true of buss bars (bus bars) in OUTDOOR SUBSTATIONS***
Once at the point of distribution, other transformers reduce the voltage to:
Electricity is then fed through a grid of cables/transformers that take it right to the customers door. On the way, the voltage is:
Further stepped down to 120 or 240 volts normally used in the home or the office
_____ is moving force that travels through solid, liquid, and gaseous materials in the form of electron transfer from one molecule to another.
Economy of high-voltage transmission uses ________ between lines instead of _______. Distance is _______.
An air gap
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 ____________.
-the type of metal
Two main hazards with electricity:
_______ flows through the body, either due to high-voltage or low resistance, cause ______.
Amount of ________ through the body to produce injury or death is __________.
Very, very small
_____ and _______ are important factors that help determine whether a person survives a contact with electricity.
Size of contact point
Path electricity takes through the body to ground
Electrocution is affected by several variables: (5)
-amount of current
-size on contact point
-path to enter/exit the body
-duration of current flow
-condition of skin (wet, dry, broken)
It is usually the presence of _____ or ________ that triggers the response of firefighters.
The result of it
________ is one very common occurrence of such static arcing
______ is the result of current being dissipated to ground as it travels from a source, such as downed high voltage wire.
Carries vary in voltage potential, depending on the stage of transmission:
Transmission line = exceed 8,000 volts
Distribution line = potentials of 601-8,000 volts
Low-voltage potentials = up to and include 600 volts
System for distribution of electricity includes a combination of transformers with ___________, arranged in __________
High and low-power carriers
Series and parallel grid systems
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)
Watch general supervisor
Charts that show emergency posts and jobs for all staff can in large plants number more that ______.
Transformer is atop a pole, make no attempt to extinguish fire unless:
-could result in wire breakage
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:
-at least 25 ft from energized equipment
-40 ft if using SOLID streams or foam nozzles on OTHER THAN SPRAY PATTERN
In many urban areas, the most frequent response to electrical emergencies is to:
Explosive range of CO
Manhole fire: Checking adjacent bldgs for extension of fire through conduits, what indicates possible fire extension?
Heat in the fuse service panel
Current flowing through these unintentional conductors (metal objects with no house ground) can be as large as what the building service carries:
Hundreds of AMPS
Exposed wires at the base of a lamp post contain upward of:
*notify utility last after taping wires and taping off area*
DANGER AREA for downed wires is defined as area in ALL directions that is at least:
As large as the length of the wire in question
First tactical consideration is to define the perimeter of the operation by establishing a safety zone that is:
One full span greater than the affected span.
Although ______, ______, and ______ are all useful tools for lifesaving purposes, you SHOULDN'T rely on them.
Visual hints-overheated ballasts *intact bulbs*
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
Life-threatening condition - lines on a car and no hot stick
*cannot be used during rainy/damp weather*
1st throw under
Far side retrieves and walks backward
*presence of spilled gasoline may remove this option*
Although it is true that the level of _______ does the damage, current passing through a body requires adequate _______ to cause the amps to flow.
The presence of _______ is usually, if not always, accompanied by _______.
*high voltage doesn't do the damage, but what accompanies it does*
Many utilities refer to anything ________ as low voltage.
LESS than 600V
When electricity has performed its function at the appliance or light bulb, it returns to its source via __________.
A return wire
The larger the ______, the higher the _____ is a valid indicator.
In high voltage conductors, the current can jump _______, depending on _____, _____ and _________.
3 ft or more
Moisture content of the air
Type of conductor
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.
Junctions of cables
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 ______.
Generally a Defensive one
Power is shut down
In a generating station, water heated, turning it to steam at over _______. Accompanied by _________ and a ___________.
Cloud of condensing water vapor
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 __________.
Very pale flame, nearly invisible
Actions to be taken-
Inside generating station:
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
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
Rumbling noise we hear at manhole fires is ________.
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*
Signs of open ground:
What to do:
Dimming of lights/presence of sparks at contact point of metal objects/overheating of building's electrical wires
Open individual breakers/circuits, reducing load
Downed line can be ____, ____ or ______.
Dancing, arcing or just lying still
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 __________.
Victim or vehicle
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.
Long, dry, wooden boards
Power be shut down
Wire over car with people in it (3 scenarios)
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*
Older types, often ______. Should wear _____. Thermal imaging cameras or other types of ____________ devices can be used. Without a _________, must physically inspect each fixture.