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Training Bulletins > TB 8 - Electrical hazards > Flashcards

TB 8 - Electrical hazards Flashcards

1
Q

LAFD resources respond to over 3000 electrocutions, wires down, and other electrical emergencies annually.

NIOSH stats document that over the last 20 years, electrocutions to first responders have resulted in more than _____ deaths in the fire service.

A

25 deaths

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2
Q

CURRENT flows from points of HIGH voltage to points of LOW voltage on the surface of a conductor and is measured in _______.

A

Amperes.

flow of electricity is comparative to flow of water through a fire hose.
QUANTITY of electricity is expressed in Amperes (amps); conversely, water is measured in gallon per minute(gpm).

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3
Q

______ is the difference in electrical potential between two points in a circuit. It is the push or pressure behind current flow through a circuit.

The comparable term in water hydraulics would be pounds per square inch (psi).

A

Voltage

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4
Q

What term is a measure of 1000 volts and commonly used by Los Angeles Department of Water and Power (LADWP) and in the electricity provider industry.

A

Kilovolts

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5
Q

Resistance determines how much current will flow through a component. Electrical resistance is measured in _______.

Resistors are used to control voltage and current levels.

A

Ohms

Comparable to friction loss in hose

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6
Q

OHM’S LAW- Ohm’s Law defines the relationships between power (watts), voltage (volts), current (Amps), and resistance (ohms).

One ____ is the resistance value through which one _____ will maintain a current of one _____

A

One OHM is the resistance value through which one VOLT will maintain a current of one AMPERE.

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7
Q

Ohm’s Law:

Watts =

Amps =

Volts =

A

Watts = amps x volts

Amps = watts x volts

Volts = watts x amps

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8
Q

Power is the amount of current times the voltage level at a given point measured in ______.

A

watts

Power = watts

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9
Q

EXTREMELY high voltage are voltages in excess of ______ volts. Usually transmission line voltage.

A

60,000v

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10
Q

High voltage is considered voltage from _____ to _____ volts.

It’s Usually found in CUSTOMER distribution system. Referred to as primary circuit voltage or “PRIMARIES”.

A

600v to 59,000v

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11
Q

In the LADWP system the PRIMARY distribution lines are usually carry how many volts?.

A

4.8kv (4,800 volts)

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12
Q

Low Voltage is usually below ____ volts.

These are called secondary circuit voltage and commonly referred to as “secondary”.

A

600v.

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13
Q

A comparison of electricity and the equivalent in fireground hydraulics terms:

ELECTRICITY FIRE HYDRAULICS

Conductor =
Current =
Voltage =
Amperes =
Ohms =

A

Conductor = Hose
Current = Water
Voltage = Pressure
Amperes = Gallons per minute
Ohms = Friction Loss

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14
Q

All voltages above _____kv are referred to as transmission voltages.

Most of the transmission lines coming into Los Angeles are _____ kv, but many lines are higher than that.

A

69kv

230 kilovolts

(Voltages on transmission lines range from 69kv to over 1000kv.)

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15
Q

_______ are used to carry the electricity from GENERATION STATIONS in a system of wires that carry electricity to the grid.

A

Transmission lines

(Grids are the layout of the electrical distribution system which is a system of wires, substations, and switchyards throughout the transmission system.)

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16
Q

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 SUB-TRANSMISSION.

A

34.5 kilovolts

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17
Q

There are distribution stations where the electricity is received at 34.5kv and stepped down to _____kv. This is the voltage known as PRIMARY circuit voltage.

A

4.8 kilovolts

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18
Q

Large commercial or industrial consumers such as hospitals, malls, high-rise buildings, metro rail stations and large complexes are an example of some consumers that are connected at a high voltage of _______.

A

34.5 kilovolts

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19
Q

High-voltage _______ have been known to retain a deadly electrical charge even weeks after power has been removed from the circuit.

A

capacitors

A capacitor is a 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

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20
Q

POLE-MOUNTED transformers are the most common distribution transformer.

They are installed on the _____kv circuits to step the voltage down to _____ volts for most residential consumers.

A

4.8 kilovolt

120/240 volts

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21
Q

Transformers for subsurface electrical are mounted above ground on concrete bases called pad-mounted transformers.

These large boxes are connected to ____kv circuits and are located in parking lots of small and medium size businesses or in the front yard of some residences.

A

4.8 kilovolt

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22
Q

Subsurface distribution lines are becoming more prevalent.

Underground lines can be found in several configurations: ________, _________, and ______.

A

-Underground
-subsurface
-direct buried

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23
Q

Underground electrical lines can be found in conduits or ducts and are identified by warning signs labeled ________.

Electrical DISTRIBUTION LINES placed directly in the ground are designated _______.

A

UG (underground).

direct buried (DB).

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24
Q

True or False?

The voltage of a conductor cannot be determined by the conductor’s size.

A

True

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25
Q

_______ are appliances which will prevent the flow of electricity and provides support to the conductor.

They are most commonly made of glass or porcelain.

A

Insulators

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26
Q

Service connections are wires that connect the customer to the secondary transformer and may be HIGH or LOW voltage.

What are the different configurations of service connections?

A

Single wire

Double wire

Triple wire (Most common, aka triplex)

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27
Q

What is the most effective methods of identifying different voltages of overhead conductors?

A
  1. High voltage signs on the cross arms.
  2. The size and shape of insulators; remember, the insulators at the top of poles will appear smaller than they really are.
  3. The distance between conductors; the higher the voltage, the greater the distance between conductors. (Size of conductor DOES NOT give good indication]
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28
Q

Electrical shock occurs when current passes through the body.

The degree of shock and resulting injuries depends on?

A

-Amount of CURRENT

-Length of TIME the current passes through the body

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29
Q

What are the 4 main types of electrical injuries?

A

-Electrocution
-Electrical shock
-Burns
-Falls

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30
Q

1/10 of an amp of electricity going through the body for just ____ seconds is enough to cause death.

A

2 seconds

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31
Q

Currents above _____ milliamps (mA) can paralyze or “freeze” muscles. This leads to respiratory paralysis.

Usually, it takes about 30 mA of current to cause respiratory paralysis.

A

10 milliamps (mA)

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32
Q

Currents greater than ____ mA may cause ventricular fibrillation (very rapid, ineffective heartbeat).

This condition will cause death within a few minutes unless a what is used to save the victim?

A

-75mA

-defibrillator or Automatic External Defibrillator (AED)

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33
Q

EARLY DEFIBRILLATION has consistently been shown to be the single most important factor in the resuscitation of patients in cardiac arrest.

For every minute that defibrillation is delayed, the patient sustains a ____% reduction in their chances for survival.

A

10%

34
Q

At 600 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.

A

4 amps

(People with less muscle tissue are typically affected at lower current levels. Low voltage does not mean low hazard)

35
Q

Electrical shock chart:

A
36
Q

Currents that pass through the _____ or ______ are most dangerous.

A

Heart

Nervous system

(If you contact a live wire with your head, your nervous system will be damaged.)

37
Q

Ultimately, the danger from electrical shock depends on the:

A

• Amount of the shocking current through the body

• Duration of the shocking current through the body

• Path of the shocking current through the body

38
Q

What are the two main methods for de-energizing a building?

A
  1. Opening the main switch or breaker switches at electrical panel
  2. Cutting wires utilizing LAFD equipment
39
Q

The following guidelines should be adhered to when shutting down power from the electrical panel or main switch:

A
  • Wear full PPEs.
  • Protective goggles must be worn. Consider donning SCBA facepiece.
  • Size up the electrical panel for signs of damage from fire or water.
  • Avoid standing in a wet area.
  • Stand to the side of electrical panel.
  • Do not reach across body to disconnect power.
  • Turn away from panel when disconnecting power to protect upper extremities.
  • Do not de-energize a structure by pulling electrical meters as this practice can result in arcing and possibly explode.
40
Q

The cutting of wires by firefighters must be confined to low-voltage wires. In an emergency when there is a need to cut high-voltage lines, call MFC and request _____ personnel trained to handle high voltage.

A

LADWP

41
Q

Wires on poles shall not be cut by firefighters unless there is an immediate life hazard, and then cutting must be confined to ____ voltage wires.

A

Low voltage

42
Q

When cutting wires attached to a building, use the following safeguards:

A
  • Wear full PPEs. Protective goggles MUST be worn. Consider donning SCBA facepiece.
  • Use mechanical axe with rubber gauntlet gloves.
  • Stand on a dry object. Lock in when working on a ladder.
  • When possible, cut at the loops attached to the service head. 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 CLOSEST conductor first. When cutting, do not touch another conductor or a ground. After cutters are in place, turn head to protect eyes from flash and sparks.
  • Be sure all insulated wires leading to the service head are cut.

-Do not cut the bare wire in triplex UNLESS there is a danger of it falling, or if there is a possibility that it has become energized.

43
Q

Equipment used for de-energizing electricity, such as the mechanical axe and gauntlet gloves, must be TESTED and INSPECTED at ______ intervals.

Pike poles, rubbish hooks, or other tools SHOULD NOT be used to contact energized equipment.

A

frequent

44
Q

What are the significant methods that can result in electrocution at an emergency involving electrical equipment?

A
  1. Voltage GRADIENT
  2. TOUCH potential
  3. STEP potential
45
Q

Methods of electrocution:

_________ is 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.

A

Voltage gradient

A person stepping into this ground gradient will receive an electrical shock.

46
Q

Methods of Electrocution:

_______ occurs by contacting a live or energized source.

This commonly occurs when a vehicle, fence, or other conductor is in contact with a live conductor such as a downed wire.

A

Touch potential

47
Q

Methods of electrocution:

________ 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

A

Step potential

48
Q

The apparatus is NOT insulated from the ground by its rubber tires and may be energized by live wires in the following ways:

A
  • By touching an object that is in contact with a live conductor
  • By direct contact with a live conductor
  • By way of an extended aerial ladder touching a live conductor
49
Q

For voltages of 600 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.

A

10 ft

50
Q

Department members shall not work in violation of the 10-foot rule for electrical wires unless?

A

participating in an actual rescue attempt

51
Q

If apparatus does become energized:

A
  • Utilize emergency traffic procedures to notify all personnel of the hazard.
  • Request MFC to contact LADWP for immediate dispatch.
  • Do not attempt under any circumstances to raise or move high-voltage lines.
52
Q

Downed Overhead Wires:

Apparatus and responding personnel should maintain how far a distance from an affected wire or pole?

A

at least one span (the distance between two poles) from the affected wire or pole.

If the pole is damaged don’t count the damaged pole.

For OPTIMUM safety,the distance between TWO UNDAMAGED poles will provide the best margin of safety.

53
Q

Sheared hydrants impacting High-Voltage lines:

Although water is NOT a good conductor, incidents such as sheared hydrants where large volumes of water are contacting high-voltage lines should be approached with care.

Unless a life hazard exists, notify and await arrival of _____ personnel.

A

LADWP

54
Q

What is the best way to handle fires in Streetlights, Overhead and Pad-Mounted transformers? (Same considerations for all)

A

-notify LADWP
-let it burn
-Protect exposures
-keep people away
-extinguish only after LADWP has de-energized

55
Q

Street lights can be fed from conductors carrying ______ volts or more. Although some street lights are low voltage, LADWP considers them high voltage at all times.

A

120-6150 volts

56
Q

In the event of a fire or emergency in a distribution station, consider these steps:

A
  • Notify MFC of the location and conditions.
  • In case of rescue, have victim remain stationary until LADWP gives clearance for rescue.
  • In case of fire, protect exposures until assured by Water & Power representative that the power is cut off. Do not put water on electrical equipment unless directed by LADWP personnel.
57
Q

Water by nature IS NOT a good electrical conductor but there are factors that increase the conductivity of water:

A

-dissolved minerals

-impurities in water.

58
Q

Applying water to an overhead transformer fire SHOULD BE avoided as it is not effective and it can cause?

A

Adjacent wires to fall

59
Q

Although injuries to firefighters from applying water directly on electrical fires are rare, water streams applied in the vicinity of high voltage should be avoided. When hose streams must be used, the following should be adhered to:

A

A. Where possible, extinguish SMALL electrical fires with DRY CHEMICAL or CARBON DIOXIDE extinguishers.

B. Utilize a fog stream. The air spaces between the drops of water in the stream limit electrical conductance.

C. Utilize the 30/33/100 Rule for using hose streams around high voltage

60
Q

The 30/33/100 rule is used for?

-Explain each number

A

Using hose streams around HIGH VOLTAGE

  1. 30-degree fog pattern. Straight streams or foam SHOULD NOT be used on high voltage sources.
  2. Firefighters applying water should maintain a distance of at least 33 feet from the energized source.
  3. Ensure a minimum of 100 psi. is pumped to the nozzle. A strong stream will reduce conductivity.
61
Q

Always maintain a safe distance from energized equipment.

The LADWP recommends not approaching a high-voltage source closer than ______, so that a fall forward would not cause direct body contact.

A

one’s body length

62
Q

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 (fireline tape) that state “Do Not Enter” or “Do Not Cross”

A

3 horizontal strands

63
Q

Firefighters responding to incidents in which individuals are trapped by downed wires must be extremely aware of ______ potential.

A

Touch potential

64
Q

Occupants trapped in a vehicle by energized wires may be able to drive the vehicle clear of the wires.
The vehicle should be driven clear of the wires by at least ____ feet.

A

35 ft

65
Q

If an electrical energized vehicle is in a position where an exigent-life threatening situation exists the people inside should attempt to self extricate.

What are two methods that can be used from removing oneself from an energized vehicle?

A

-Jump from the vehicle without touching it, keeping both feet together and taking small hops from the car.

-Jump from the vehicle without touching it and shuffling the feet together.

66
Q

Electrical Hazards at wildland fires include:

A

• Contact with downed power lines

• Downed power lines that energize conductive equipment or vehicles on the fireground

• Exposure to voltage ground gradients.

• Smoke that becomes charged and conducts electrical current

• Solid-steam water applications on or around energized, downed power lines or equipment

67
Q

Operations near transmission lines at wildland fires:

• Maintain a minimum distance of ____ feet from TOWERS.

• Maintain clearance a minimum of ____ feet beyond the outermost wire of electrical TRANSMISSION LINES.

• Never direct hose streams at high voltage wires.

• Keep hose streams below the height of ________.

• Never direct hose streams into HEAVY plumes of smoke within _____ feet of high-voltage wires. (Smoke can be conductive)

A

• Maintain a minimum distance of 35 ft from towers.

• Maintain clearance a minimum of 100 ft beyond the outermost wire of electrical transmission lines.

• Never direct hose streams at high voltage wires.

• Keep hose streams below the height of THE INDIVIDUAL OPERATING IT.

• Never direct hose streams into heavy plumes of smoke within 100 FEET of high-voltage wires

68
Q

Vault/Manhole Fires:

The explosive range for carbon monoxide (CO) is 12.5 to 74 percent.

Those levels can be reached within a electrical vault or manhole area and as a result, ______ may occur at any time in the immediate fire area or even in nearby buildings.

A

Explosions

69
Q

Vault/Manhole Fires:

NEVER put water into a vault or down a manhole.

Use only _______ extinguishers and only when requested to do so by a qualified LADWP representative.

A

non-conducting

70
Q

Vault/Manhole Fires:

If smoke is issuing from the manhole cover, DO NOT attempt to remove the cover.

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 “blowing” if they are ___________.

A

connected to the same shaft.

71
Q

Vault/Manhole Fires:

Set up a safety perimeter, and keep bystanders a safe distance from the manhole opening (all four sides).

Manhole covers often weigh ____ pounds and have been blown _____ feet into the air and a distance of _____ feet.

A

300 pounds

75ft into air

125ft distance

72
Q

Any entry made into a vault or manhole to rescue a downed worker or patient must be considered a _______ rescue emergency

A

confined space

Need USAR

73
Q

When overhead electrical conductors are down or sagging dangerously, the first-in company should:

A
  1. Notify MFC and give the correct address/report.
  2. Clear the area. Keep people at least ONE SPAN AWAY from the broken or sagging conductors.
  3. Protect exposures.
  4. Considered all conductors energized even if they appear deenergized. The circuits will be cycled on again unless there is a ground or short circuit.
  5. Make certain that the conductors are cleared and safe or that you are properly relieved of your responsibility before you leave the scene.
74
Q

Dept of Water and Power line patrolman are equipped and trained to handle high voltage. Their apparatus operates 24 hours a day, is radio equipped, and can usually reach any area of the City within _____ minutes.

A

10 mins

(Yeah right….)

75
Q

The LADWP tests rubber gauntlet gloves to ______ volts every 60 days.

A

10,000 volts

76
Q

Make no attempt to extinguish fires involving underground electrical equipment until notified by the LADWP or ______ that the electrical current is turned off.

A

MFC

77
Q

What does a square manhole cover indicate?

A

Indicates a transformer vault

78
Q

The main fire hazard within ELECTRICAL VAULTS lies in the _______ used in the transformers, which has a flash point below _____F.

A

cooling oil

300 degrees F

79
Q

Underground Vaults:
Location of the cables in vaults is no longer an indication of voltage.

High-voltage cables, up to ______ volts, may be located close to the floor inside a conduit containing 200-psi oil pressure.

A

230,000

80
Q

The SAFEST TACTIC regarding the use of hose streams around a high voltage source is to _________.

A

Take a DEFENSIVE stance

Let the equipment burn and PROTECT EXPOSURES

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