*TB 8- Electrical Hazards Flashcards
Terminology: The push or pressure behind current flow through a circuit is know as?
Volts
Terminology: _______ determines how much current will flow through a component.
Ohms
Amps x volts = ?
Watts (power)
High voltage is ranges from _____ to _____. Also referred to as “primaries”
600 to 59,999v
Low voltage is usually below _____ volts also referred to as “secondaries”
600v
Extremely high voltage is considered in excess of ______ volts
60,000v
All voltages above ________ volts are referred to as transmission voltages.
69,000v
Sub-transmission lines are considered to have __________ volts
34,500v
At a distribution station, electricity is received at ______ volts and stepped down to _____ volts
- 34,500v
2. 4,800v
Lines that carry 4,800 volts and run from the distribution stations to the neighborhood it feeds are known as what “type” of power lines?
primary lines or “primaries”
A receiving station takes high voltage from transmission lines and steps the voltage down to what?
34,500 volts
A ___________ is designed to reduce the voltage in the system to a voltage usable by the consumer.
Transformer
Pole-mounted transformers are installed on 4,800v circuits and step the voltage down to _____ volts
120/240 volts
Underground electrical lines can be found in conduits or ducts and are identified by warning signs labeled ______
UG (underground)
Electrical distribution lines placed directly in the ground are designated as _________
DB (direct buried)
High voltage capacitors are dangerous because?
- They can hold a charge for weeks even if power was shutdown to the circuit
- Contain dangerous chemicals
________ are appliances which will prevent the flow of electricity and provides support to the conductor.
Insulators
Insulators are mostly made of _____ or _____
Glass or porcelain
The service connection that uses three conductors twisted around each other is know as a _______
Triplex
The 3 most effective methods of identifying high voltage on a pole are?
- High voltage sign on cross arms
- Size and shape of insulators (large = high volts)
- Distance between conductors (wires)
What are the four main types of electrical injuries?
- Electrocution
- Electrical shock
- Burns
- Falls
Firefighters responding to emergencies involving electrical equipment must wear what kind of PPE’s?
Full turnouts with hood and firefighting gloves
There are two main methods for de-energizing a building are?
- Throw the main switch or breaker switched at electrical panel
- Cut wires with LAFD equipment
Besides wearing full firefighting turnouts while shutting down power at the electrical panel, what else SHALL be worn?
Eye protection, consider scba face piece
Is the LAFD able to cut high voltage wires in the case of an emergency?
No, contact MFC to have DWP respond
Aerial ladders must be kept at least _____ feet away from all power lines and devices.
10ft
The aerial ladder shall not work in violation of the 10-foot rule from electrical wires unless?
Participating in a rescue attempt
During a rescue attempt with the aerial ladder, can any member remain at the pedestal to operate the ladder?
No, it SHALL be the apparatus operator
Even if a wire is not electrical, should it be considered charged?
Yes, additional wires may have fallen and charged them
Even overhead communication cable normally found on the lowest level of a power pole can be energized with up to _____ volts.
50v
If an apparatus becomes energized, what must be announced so other members on scene are aware of the danger?
Emergency traffic
If an apparatus becomes energized with a downed high voltage wire, can LAFD members raise or move the wire to de-energize the apparatus?
No, call for LADWP
Keep ground ladders at least ____ feet from wires
10ft
For a downed overhead wire, have responding personnel maintain at least ___ span(s) from the affected wire or pole
One
“One span” is considered the distance between how many poles?
2 poles
For optimum safety, the distance between how many undamaged poles will provide the best margin of safety?
2 undamaged poles
What should be the LAFD actions when water from a sheared hydrant is contacting overhead electrical wires?
Call and wait for DWP, unless a life hazard exists
What should be the firefighting actions for an overhead or pad mounted transformer fire?
Secure scene and protect exposures
Extinguish once DWP has de-energized
Streetlights can be fed from conductors carrying ____ to ____ volts or more.
120-6150v
Are street lights considered low or high voltage?
High voltage
What should be the firefighting actions for a street light fire?
Secure scene and protect exposures
Extinguish once de-energized by DWP
What should be the firefighting actions for a distribution/substation fire?
Secure scene and protect exposures
Extinguish once de-energized by LADWP
What are the LAFD actions in case of rescue in a distribution station?
Have victim remain stationary until LADWP gives clearance for rescue
What is the “rule” developed for using hose streams around high voltage?
What does it stand for?
30/33/100 rule
30 degree fog pattern
33 feet away from energized source
100psi minimum to nozzle
Where possible, extinguish small electrical fires with what two types of extinguishers?
Dry chemical or carbon dioxide extinguishers
The method to assure that fire personnel do not enter Life Hazard Zones includes the use of a minimum of ______ horizontal strands of barrier tape that state “Do Not Enter” or “Do Not Cross”.
3
If the driver of a vehicle in contact with downed wires is able to drive the vehicle, it should be driven clear of the wires by at least ____ feet.
35ft
Instructing victims to exit a charged vehicle should only be done when?
A life threatening emergency exists
The main fire hazard within electrical vaults lies in the _______ used in the transformers, which has a flash point below _____F.
- Cooling oil
2. 300
How much do manhole covers weigh?
300 lbs
How high can a manhole cover be blown into the air and at what distance can it end up?
- 75 ft
2. 125 ft
___ of an amp of electricity going through the body for just 2 seconds is enough to cause death
1/10th
When cutting wires at the drip loop with LAFD equipment, cut which wire (conductor) first?
Closest
Per T.B. 49:
All Water and Power capacitors, transforms, regulators, and resistors are labeled with a ___ inch x ___ inch yellow and black sign indicating that the equipment contains PCB’s
2” by 2”
Voltages on transmission lines range from ___ kv to over ___kv.
Most of the transmission lines coming into Los Angeles are ____kv
60kv to 1000kv
230kv
Pad mounted transformers 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.
48
Underground distribution lines can be found in what three configurations?
- underground
- subsurface
- direct buried.
At 600 volts, the current through the body may be as great as ___ amps
4
Voltage _______ is a decreasing current created when a energized wire is in contact with the earth.
Gradient
What are the three significant methods that can result in electrocution at an emergency involving electrical equipment?
- Voltage gradient
- Touch potential
- Step potential
What are the two methods used when instructing a patient to exit an electrically charged vehicle where a life treating emergency exists?
(Firefighters must not approach or grab victim)
Jump from the vehicle and:
- Keeping feet together and taking small hops away
- Shuffling feet together
A transformer vault has a _____ shaped manhole cover
Square
Terminology: Current flow or electron flow is known as?
AMPS
