Training Bulletin 8: Electrical Hazards Flashcards
According to the National Institute for Occupational Safety and Health (NIOSH), electrical accidents in the United States account for over ___ deaths a year and OSHA statistics indicate that electrocution accounts for __% of worker deaths annually. NIOSH statistics also document that over the last 20 years, electrocutions to first responders have resulted in more than ___ deaths in the fire service.
700
12%
25
The Los Angeles Fire Department (LAFD) resources respond to over ____ electrocutions, wires down, and other electrical emergencies annually.
3000
Electric charges can be _______, as in static electricity, or _____, as in an electric current.
Stationary
moving
a movement of charge is an ___
electric current
Current flow, or electron flow, is what flows on a wire or conductor like water flowing down a river. Current flows from points of high voltage to points of low voltage on the surface of a conductor. The flow of electricity maybe compared with the flow of water through a fire hose. GPM
amps
Is the difference in electrical potential between two points in a circuit. It is the push or pressure behind current flow through a circuit. (psi)
Volts
The measure of 1000 volts. A measure commonly used by Los Angeles Department of Water and Power (LADWP) and in the electricity provider industry.
Kilovolts
Resistance determines how much current will flow through a component. Resistors are used to control voltage and current levels. A very high resistance allows a small amount of current flow. A very low resistance allows a large amount of current to flow. (Friction loss)
OHMS
defines the relationships between power (watts), voltage (volts), current (Amps), and resistance (ohms). One ohm is the resistance value through which one volt will maintain a current of one ampere.
OHM’S LAW
Power is the amount of current times the voltage level at a given point measured in
WATTS
amps x volts=
Watts
watts x volts=
Amps
watts x amps=
Volts
Extremely high voltage: voltages in excess of ____ volts. Usually transmission voltage.
60,000
High voltage: voltage from ___volts up to _____ volts. Usually found in customer distribution system. Referred to as _____ circuit voltage or “______”. In the LADWP system the primary distribution lines are usually ___kv.
600 to 59,999
primary or (“primaries’’)
4.8
Low Voltage: Usually below ___ volts. These are called secondary circuit voltage and commonly referred to as “______”.
600
secondary
ELECTRICITY FIRE HYDRAULICS
Conductor = ____
Current = ____
Voltage = _____
Amperes = _________
Ohms = _________
Hose
Water
Pressure
Gpm
Friction Loss
Getting electricity to the consumer can be broken down into three systems
generation, transmission, and distribution system
The LADWP system is comprised of over _____ transformers, over _____ poles and _____ of substructures and switches installed over the last 70 years.
50,000
250,000
1000s
where the electrical energy transformation process originates and where a complete circuit starts.
power generation plant
Generation facilities generate electricity between ____ and _____ volts
4000 and 20,000 volts
Though generation plants produce a substantial amount of volts, it is not nearly enough to deliver power the long distances necessary to connect different parts of the city together. In order to raise the voltage for this task generation stations use ______ facilities that rely on transformers
switching facilities
There are two main components of the transmission system
grids and transmission lines
are the layout of the electrical distribution system which is a system of wires, substations, and switchyards throughout the transmission system
Grids
are used to carry the electricity from generation stations in a system of wires that carry electricity to the grid
transmission lines
Transmission lines are used to carry high voltage electricity the long distances from ______ ______ to ______ ______
generating plants to distribution stations
Most common transmission lines in Los Angeles are _____ ______ lines which are also called high-voltage or high-tension wires. consists of wires mounted on steel or wood poles
overhead transmission lines
Voltages on transmission lines range from ___kv to over _____kv
69kv to 1000kv
Most of the transmission lines coming into Los Angeles are _____kv
230kv
All voltages above 69kv are referred to as
transmission voltages
The structures that support transmission lines are usually
steel towers
Strings of insulators on transmission towers can range from __- to ___-feet long depending on the voltage they are trying to hold back from contacting the towers that support them.
3-20
The LADWP also has a number of transmission lines with voltages of _____kv or ______kv
138kv or 230kv
located mainly in the most congested areas and are used for routing bulk power around the City. lines inserted in conduits or ducts and buried in ground
underground transmission lines
The component of the electric system that delivers electrical energy to the consumer or residence consists of distribution stations and distribution lines. This system works by stepping down the voltage while proportionately stepping up the amps with transformers the same way the voltage was stepped up in the generation system at the beginning of the circuit.
distribution system
Substations that utilize transformers to change high-voltage electricity into lower voltage. This process begins at the receiving station.
LADWP Distribution Stations
the voltage is stepped down ___ times in the distribution system before it is delivered to most consumers.
three
_______ _______ carry electricity from the distribution system to homes, offices and factories which require low-voltage electricity
Distribution Lines
The LADWP has ___ receiving stations which receive the electricity at transmission voltages (138kv to 500kv) and step the voltage down to ____kv, which is referred to as ______
21
34.5
sub-transmission
There are over ____ distribution stations where the electricity is received at 34.5kv and stepped down to ___ kv
150
4.8
The 4.8kv primary lines run from a distribution station to the ____ that it feeds.
neighborhood
Each primary has an average of ___ consumers
750
The LADWP has over _____ primary circuits in the city
1500
The LADWP has many consumers that are connected to the grid at high-voltage(any voltage 600 volts and over). The most common are large _____or ____consumers
commercial or industrial
are appliances used to increase or decrease the voltage of the electrical current.. designed to reduce the voltage in the system to a voltage usable by the consumer.
distribution transformer
The electricity produced by generator travels along cables to a transformer, which changes electricity from _____ voltage to _____ voltage
low voltage to high voltage
type of electronic component which passively acts as a form of conductor. When a charge of opposing currents is run through the device then a field is generated in which energy is stored
capacitor
High-voltage capacitors have been known to retain a deadly electrical charge even ___after power has been removed from the circuit
weeks
_____-Pole-mounted transformers are the most common distribution transformer. They are installed on the 4.8kv circuits to step the voltage down to ___/___volts for most residential consumers
overhead transformers
120/240
Transformers for subsurface electrical are mounted above ground on concrete bases called ___These large boxes are connected to 4.8kv circuits and are located in parking lots of small and medium size businesses or in the front yard of some residences.
pad-mounted transformers
appliances which will prevent the flow of electricity and provides support to the conductor. They are most commonly made of glass or porcelain.
Insulator
The wires that connect the customer or home to the secondary transformer and may be high or low voltage.
Service Connection
The most effective methods of identifying different voltages are
- High voltage signs on the cross arms.
- The size and shape of insulators; remember, the insulators at the top of poles will appear smaller than they really are.
- The distance between conductors; the higher the voltage, the greater the distance between conductors.
here are four main types of electrical injuries:
electrocution (death due to electrical shock), electrical shock, burns, and falls.
___ of an amp of electricity going through the body for just two seconds is enough to cause death.
1/10th
The amount of internal current a person can withstand and still be able to control the muscles of the arm and hand can be less than ____ milliamps
10 milliamps (mA)
Currents above 10 mA can ______ or _____ muscles
paralyze or “freeze” muscles.
If you cannot let go of the tool, current continues through your body for a longer time, which can lead to
respiratory paralysis
People have stopped breathing when shocked with currents from voltages as low as _____ volts
49 volts.
Usually, it takes about ____ milliamps of current to cause respiratory paralysis.
30 mA
Currents greater than ____milliamps may cause ventricular fibrillation (very rapid, ineffective heartbeat). This condition will cause death within a few minutes unless a defibrillator or Automatic External Defibrillator (AED) is used to save the victim.
75 mA
For every minute that defibrillation is delayed, the patient sustains a ____ reduction in their chances for survival.
10%
Heart paralysis occurs at _____amps .Tissue is burned with currents greater than _____ amps
4 amps,
5 amps.
LOW VOLTAGE DOES NOT MEAN ______ _____
LOW HAZARD!
At _____ volts, the current through the body may be as great as ___ amps, causing damage to internal organs such as the heart. High voltages also produce burns and in addition, internal blood vessels may clot.
600 volts
4 amps
Effects of electrical current on the body:
1 milliamp
just a faint tingle
Effects of electrical current on the body:
slight shock felt. Disturbing, But not painful. most people can “let go”.
5 milliamps
Painful shock. Muscular control is lost. This is the range where “freezing currents” start
6-25 milliamps (women)
it may not be possible to “let go”
9-30 milliamps (men)
extremely painful shock, respiratory arrest (breathing stops), sever muscle contractions. Flexor muscles may cause holding on; extensor muscles may cause intense pushing away. death is possible
50-150 milliamps
ventricular fibrilation (heart pumping action not rhythmic) (1-4.3 amps) occurs. muscles contract nerve damage occurs. death is likely
1,000 - 4,300 milliamps
cardiac arrest and sever burns occur.
death is probable
10,000 milliamps (10 amps)
lowest overcurrent at which a typical fuse or circuit breaker opens a circuit ______ milliamps
15,000 milliamps (15 amps)
what two things affect the severity of shock
differences in muscle and fat content
Dry skin may have a resistance of
100,000 ohms or more
Wet skin may have a resistance of only
1,000 ohms.
The most common shock-related, nonfatal injury is a____. Typically, such burns occur on the___
burn.
hands
Ultimately, the danger from electrical shock depends on the:
• ______ of the shocking current through the body
• ______ of the shocking current through the body
• _____ of the shocking current through the body
amount
duration
path
Personal Protective Equipment (PPEs) what conducts electricity?
The metal insoles of turnout boots
Turnout coats and pants have metal clasps and buttons
There are two main methods for de-energizing a building. they are?
- Opening the main switch or breaker switches at electrical panel.
- Cutting Wires Utilizing LAFD Equipment
Wires on poles shall not be cut by firefighters unless there is an immediate life hazard, and then cutting must be confined
low voltage wires.
When cutting wires attached to a building, use the following safeguards:
When possible, cut at the loops attached to the
service head
Many service connections are ____ ____, which is three wires wound around each other and should not be cut.
triplex cables
the mechanical axe and gauntlet gloves, must be tested and inspected at frequent intervals. _____, _______, or ____, can reduce the insulating properties of these tools. These tools should be used for ____ _____ applications only. Pike poles, rubbish hooks, or other tools should not be used to contact energized equipment.
damage
moisture
dirt
low voltage
a decreasing current created when a energized wire is in contact with the earth. The ground soil becomes a conductor and will allow current to travel a distance from an energized source, such as a fallen wire. The current spreads out from point of the energized source like ripples in a pond. A person stepping into this ground gradient will receive an electrical shock.
Voltage Gradient
commonly occurs when a vehicle, fence, or other conductor is in contact with a live conductor such as a downed wire.
Touch Potential
Occurs when responders or victims create a circuit with their feet as they walk over or across a voltage gradient created by an electrical source, such as a downed wire.
Step potential
The apparatus is ____ _______ from the ground by its rubber tires and may be energized by live wires in the following ways:
- By ______ an object that is in contact with a live conductor
- By ______ contact with a live conductor
- By way of an extended ____ ______ touching a live conductor If there is any chance that the apparatus is in contact with a live conductor, and it is necessary to get off the apparatus, do not step off, get above the running board cable and jump off. If you are on the ground, make no attempt to get on an electrically charged apparatus.
not insulated
touching
direct contact
aerial ladder
For voltages of ___or more, Cal/OSHA and NFPA standards require that aerial ladders be operated at a minimum clearance of __feet of power lines and electrical devices. This distance is not only for personnel, but also for equipment, nozzle tips and other tools.
600
10
Department members shall not work in violation of the 10-foot rule unless participating in an actual ____ _____, and in those instances the Apparatus Operator shall remain at the _____ to provide for personnel safety and ensure safe operation of the aerial if required.
rescue attempt
pedestal
Aerial ladder placement must allow for ____ ____, ____and ____around electrical wires.
ladder sway, rock and sag
The most common electrical problem firefighters respond to is
downed wires.
Spot apparatus and have responding personnel maintain at least ___ ____ (the distance between two poles) from the affected wire or pole.
one span
FIREFIGHTING CONSIDERATIONS
A. Overhead Transformers
Usually best to protect _____, clear the area from pedestrians and vehicles and notify _____. Applying water should be avoided as it is not effective and it can cause adjacent wires to fall.
exposures
LADWP
FIREFIGHTING CONSIDERATIONS
____ _____ fires should be treated the same as overhead transformers by letting them burn, protect exposures and keep people away from the area.
pad mounted
Streetlights can be fed from conductors carrying ___-___ volts or more. Los Angeles LADWP considers them energized with ______ ______ at all times.
120-6150
high voltage
When hose streams must be used, the following should be adhered to:
A. Where possible, extinguish small electrical fires with ___ ______ or ______ ______ extinguishers.
B. Utilize a ____ stream. The air spaces between the drops of water in the stream limit electrical conductance.
C. Utilize the ___/___/__ Rule for using hose streams around high voltage:
- The fog spray should be set at a ___degree fog pattern. Straight streams or foam should not be used on high voltage sources.
- Firefighters applying water should maintain a distance of at least ___ feet from the energized source.
- Ensure a minimum of ___ psi. is pumped to the nozzle. A strong stream will reduce conductivity.
dry chemical or carbon dioxide
fog
30/33/100
30
33
100
Maintain a safe distance from the energized equipment. The LADWP also recommends not approaching a high-voltage source closer than one’s ____ _____, so that a fall forward would not cause direct body contact.
body length
The clearly identified method to assure that fire personnel and other responders do not enter Life Hazard Zones includes the use of a minimum of __horizontal strands of barrier tape that state “_______” or “_________”.
3
do not enter
do not cross
Occupants trapped in a vehicle by energized wires should remain in their vehicle until the power is de-energized. However, they may be able to drive the vehicle clear of the wires. The vehicle should be driven clear of the wires by at least ___feet.
35
If the vehicle is on fire or is in a position where an exigent-life threatening situation exists such as dangling off a freeway overpass, the people inside should attempt to
self extricate
There are two methods that can be used from removing oneself from an energized vehicle:
• Jump or leap from the vehicle without touching it, keeping both feet together and taking ___ ____from the car.
• Jump from the vehicle without touching it and _______ the feet together.
small hops
shuffling
DO NOT CLIMB THE TOWER UNTIL ASSURED BY ______ THAT IT IS SAFE.
Under certain conditions, electricity at this voltage could easily become a conductor to ground. A charge of static electricity capable of jumping __ or ____ inches may build up in a person’s body when climbing a tower. This charge probably would not injure a person; however, the shock or surprise of this charge going to ground could cause a person to lose their balance.
LADWP
2 or 3 inches
Operations Near Transmission Lines
• Maintain a safe distance from transmission towers: a minimum of ___ feet should be adhered to.
• Maintain clearance a minimum of ___ feet beyond the outermost wire of electrical transmission lines.
• Never direct hose streams at ___ ____ wires.
• Keep hose streams below the ____ of individual operating it.
• Never direct hose streams into heavy plumes of smoke within _____ feet of high-voltage wires
35
100
high voltage
height
100
Downed Wires
• Assign a ____ to serve as a spotter to ensure that the location of the downed line is communicated to all fireground personnel.
lookout
Heavy____, ____ and ____ from wildfires can create an electrical path between an energized source and ground causing electrical transmission lines to short circuit.
smoke flames and heat
Make no attempt to extinguish fires involving above ground or underground electrical equipment until notified by the _______ that the electrical current is turned off.
LADWP
The ____ from an electrical vault or manhole fire is both toxic and potentially explosive because the fire burning inside is most likely conduit and the fact that the fire is burning underground results in the fire being oxygen-starved. Any ______ from power tools can cause serious or even deadly hazards to rescuers.
smoke
spark
The explosive range for carbon monoxide (co) is __ to ___ percent. Those levels can be reached within a electrical vault or manhole area and as a result, explosions may occur at any time in the immediate fire area or even in nearby buildings.
12.5 to 74
• Never put water into a vault or down a manhole. Use only ____-___ ________ and only when requested to do so by a qualified LADWP representative.
non-conducting extinguishers
Always locate the nearest manhole covers in all four directions from the involved vault or manhole cover because there is a strong possibility of any of the nearby manhole covers “_____” if they are connected to the same shaft.
blowing
Ensure that emergency workers and bystanders are not within close proximity to large _____or ____ openings because any explosion can cause glass in the area to shatter.
windows or glass
Manhole covers often weigh ____ pounds and have been blown ___ feet into the air and a distance of ____ feet. In some locations, there is a second inner, watertight cover under the top manhole cover.
300
75
125
If a manhole cover is in place and smoke is issuing from the holes in the cover, do not attempt to___ ___ ____. Flammable atmospheres may be present and may be formed in the manhole as a result of burning insulation or oil, which may be toxic or explosive.
remove the cover
SAGGING OR DOWN OVERHEAD WIRES
Circuit breakers in these systems are designed to ____ ____ and then ___ ____ ____ automatically. The circuits will be energized again unless there is a ground or short circuit.
kick out and then kick back in
In an emergency when there is a need to cut high-voltage lines, call ___and request the ___ and ____line patrolman who is equipped and trained to handle high voltage. Their apparatus operates ____ hours a day, is radio equipped, and can usually reach any area of the City within ____ minutes.
MFC
WATER AND POWER
24
10
Use the mechanical axe with rubber gloves. The LADWP tests gloves to _____ volts every ___ days.
10,000
60
Be sure to cut close to the service bracket in order to make all loose ends dead. Do not reach over charged wires. Cut the _____ ______ first.
CLOSEST CONDUCTOR
Look for, and note, if there is a _____manhole, which indicates a transformer vault.
SQUARE
Take note of “___ ____ _____” (similar to a switch panel). This is the fuse between the ___ ____ and _____. If the transformer catches fire and “shorts out,” this fuse should cut off the electrical current.
OIL FUSE CUTOUTS
MAIN LINE
TRANSFORMER
Remember that the main fire hazard within electrical vaults lies in the cooling oil used in the transformers, which has a flash point below
300F
Location of the cables in vault is no longer an indication of voltage. High-voltage cables, up to _____ volts, may be located close to the floor inside a conduit containing ____-psi oil pressure.
230,000
200
