TB 8 - Electrical hazards Flashcards
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.
25 deaths
CURRENT flows from points of HIGH voltage to points of LOW voltage on the surface of a conductor and is measured in _______.
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).
______ 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).
Voltage
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.
Kilovolts
Resistance determines how much current will flow through a component. Electrical resistance is measured in _______.
Resistors are used to control voltage and current levels.
Ohms
Comparable to friction loss in hose
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 _____
One OHM is the resistance value through which one VOLT will maintain a current of one AMPERE.
Ohm’s Law:
Watts =
Amps =
Volts =
Watts = amps x volts
Amps = watts x volts
Volts = watts x amps
Power is the amount of current times the voltage level at a given point measured in ______.
watts
Power = watts
EXTREMELY high voltage are voltages in excess of ______ volts. Usually transmission line voltage.
60,000v
High voltage is considered voltage from _____ to _____ volts.
It’s Usually found in CUSTOMER distribution system. Referred to as primary circuit voltage or “PRIMARIES”.
600v to 59,000v
In the LADWP system the PRIMARY distribution lines are usually carry how many volts?.
4.8kv (4,800 volts)
Low Voltage is usually below ____ volts.
These are called secondary circuit voltage and commonly referred to as “secondary”.
600v.
A comparison of electricity and the equivalent in fireground hydraulics terms:
ELECTRICITY FIRE HYDRAULICS
Conductor =
Current =
Voltage =
Amperes =
Ohms =
Conductor = Hose
Current = Water
Voltage = Pressure
Amperes = Gallons per minute
Ohms = Friction Loss
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.
69kv
230 kilovolts
(Voltages on transmission lines range from 69kv to over 1000kv.)
_______ are used to carry the electricity from GENERATION STATIONS in a system of wires that carry electricity to the grid.
Transmission lines
(Grids are the layout of the electrical distribution system which is a system of wires, substations, and switchyards throughout the transmission system.)
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.
34.5 kilovolts
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.
4.8 kilovolts
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 _______.
34.5 kilovolts
High-voltage _______ have been known to retain a deadly electrical charge even weeks after power has been removed from the circuit.
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
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.
4.8 kilovolt
120/240 volts
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.
4.8 kilovolt
Subsurface distribution lines are becoming more prevalent.
Underground lines can be found in several configurations: ________, _________, and ______.
-Underground
-subsurface
-direct buried
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 _______.
UG (underground).
direct buried (DB).
True or False?
The voltage of a conductor cannot be determined by the conductor’s size.
True
_______ are appliances which will prevent the flow of electricity and provides support to the conductor.
They are most commonly made of glass or porcelain.
Insulators
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?
Single wire
Double wire
Triple wire (Most common, aka triplex)
What is the most effective methods of identifying different voltages of overhead conductors?
- 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. (Size of conductor DOES NOT give good indication]
Electrical shock occurs when current passes through the body.
The degree of shock and resulting injuries depends on?
-Amount of CURRENT
-Length of TIME the current passes through the body
What are the 4 main types of electrical injuries?
-Electrocution
-Electrical shock
-Burns
-Falls
1/10 of an amp of electricity going through the body for just ____ seconds is enough to cause death.
2 seconds
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.
10 milliamps (mA)
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?
-75mA
-defibrillator or Automatic External Defibrillator (AED)