CH. 3 Electrical Knowledge Flashcards
Approach distances
The minimum distances that must be maintained between conductors and qualified line clearance personnel and their tools. No worker, tool, or conductive object may be within 10 feet of an energized overhead conductor rated 50kV or less. Approach distance increases by 4 inches for every 10kV of added voltage.
Ampere:
Measure of electrical current and is similar to the flow rate of gallons per minute used to measure water flow.
Back feed
Flow of electricity in an unintended direction
Capacitors
Devices that can store energy and are used either boost voltage or provide power factor correction
Conductivity
The capacity of a material to transmit electricity
Cutouts
The part of the fuse the falls open, creating a break in the line when an overload or short-circuit occurs.
Distribution lines
Carry electricity at voltages ranging from 2,400 to 34,500 volts to commercial or residential customers and to industrial customers.
Distribution transformers
Reduces the distribution voltage which is then carried along secondary lines to streetlights or long service wires to residential properties. Seldom more than 240 Volts.
Electrical current
The flow of electrons
Electrical potential
The condition that allows electricity to flow from one object to another. The difference in electrical voltage between two points is known as the potential difference. When a potential difference exists, electricity will flow from the point of higher voltage toward that of lower voltage along a conductive pathway if it exists.
Electrical resistance
Determines how much energy is required to move electricity along a conductive pathway. Materials with high electrical resistance require more energy and cause more heating of the conductor than do materials of little electrical resistance. Measured in ohms.
Name the two distinct failure modes
Mechanical and electrical. Mechanical failures involve tree-caused physical damage to conductors, electrical equipment, and or supporting structures. An electrical failure occurs when a tree or branch comes in contact with energized conductors causing a short circuit.
Feeder circuits
The distribution feeder circuits originate at the terminals of a circuit breaker or a circuit recloser in the distribution substation. The feeder circuits are often referred to as distribution main feeder or express feeder circuits in that they serve as the source to primary or branch circuits. Several distribution feeder circuits can radiate from a given substation.
Fuses
The fuse interrupts the current whenever there is a short circuit or an overload. When an overload or short-circuit occurs and exceeds the limit of the fuse, the fuse will blow or melt and the cut out falls open, creating a break in the line.
Guy wires
Supporting wires that are not intended to conduct electricity.
Lightning arrestors
Channels lightning or the excessive current it causes to the ground.
Ohm
The standard unit of resistance to the flow of electric current. It is equal to the resistance of a circuit in which a force of 1 V will maintain a current of one amp.
Phase
An energized conductor or wire in a circuit.
Fault
Interruption in the electricity supply.
Phase-to-phase
Current flow between two energized conductors
Phase-to-neutral
Current flow between an energized conductor and a neutral wire
Primary circuits
Circuits that carry the highest voltage to other parts of the distribution network. Normally one, two, or three-phase lines that connect to the main feeder distribution circuits through fused cutouts.
Qualified line – clearance arborist
Someone specifically trained and qualified to work safely at a minimum specified approach distance to electrical conductors.
Re-closers
Uses that open in response to a momentary surge in voltage and close again if the surge subsides in a short time. Function similar to a fused cut out, but they are designed to reset or reclose the circuit after a preprogrammed period of time. They are intended to prevent extended service interruptions resulting from instantaneous or otherwise temporary short-circuits.
Secondary lines
A distribution transformer reduces the voltage before the electricity is distributed via the secondary lines. Secondary and service wires are generally triplex wires, which have two insulated conductors and a neutral wrapped together.
Service wire
Extend from the secondary wires or distribution transformer to the customer’s property.
short circuit
An interruption in an electric current in which the electricity finds a different path to ground.
Step potential
Voltage between the feet of the person standing near an energized, grounded object
Distribution Substation
Reduce the voltage delivered by the sub transmission or transmission lines to distribution voltages in the range of 2.4 to 34.5 kV.
Transmission substation
Decrease the voltage from transmission to sub transmission voltages.
Transformer
Generally reduce the voltage of the primary circuit to the voltage required by the end-user. The primary voltages vary from 2.4 to 34.5 kV, while residential customers normally are provided 120/240 V.
Transmission lines
Carry the extra-high-voltage electric energy from the generating plant. Voltages generally range from 100,000 to 765,000 V.
Tree protection zone
Protection zone surrounding a tree during construction or trenching. The tree protection zone radius is typically 1 foot per inch of trunk diameter.
Volt
Unit of electrical force similar to pounds per square inch in a water pipe. Voltage=current x resistance. One volt is required to push one amp of current across one ohm of resistance.
Voltage regulator
Acts like a transformer, either increasing or decreasing the circuit voltage as needed.
Watt
A measure of power. Often expressed in kilowatts. 1 kW is approximately 1 1/3 hp.
Most electric energy is generated at the power plant at what voltage?
13,200 to 24,000 volts (13.2 to 24kV)
What are most electric wires or conductors made from? What are the benefits of each and which one is more commonly used today?
Copper or aluminum. Copper is a better conductor, but aluminum is lighter and less expensive. Today, an aluminum wire with a steel-reinforcing core is the most common type of wire used. Aluminum tends to stretch and so the steel core adds strength.
Which federal regulation covers employee safety training and certification, prejob briefings, electric lock out and tag out procedures, improper handling and storage of tools and equipment.
Federal regulation 29 CFR 1910.269 Electric power generation, transmission, and distribution
The unit of electrical force is called a __________?
Volt
Electrical resistance determines how much energy is required to move electricity along a conductor and is measured in _________?
Ohms
Hey conductor carrying more than 250,000 votes would be considered a __________ line.
Transmission
Circuit breakers and lightning arresters are types of _________ equipment.
Protective
Distribution transformers typically ___________ primary circuit voltage for the end-user.
Decrease
And energized wire or conductor in a circuit is also known as a ___________?
Phase
___________ wires are intended to help support poles but may become unintentionally energized.
Guy wires
__________ are similar to fuses or cutouts but reset after a predetermined time period.
Re-closers
Minimum working distances for qualified line clearance arborists are specified in the __________ safety standard.
ANSI Z133
When installing underground conductors, _________, rather than trenching, should be used in treatment protection zones.
Tunneling
The measure of electrical current is called: A. Volt B. Ampere C. Ohm D. Watt
B. Ampere
Service or secondary distribution lines usually carry voltage between: A. 120 and 480 B. 2,400 and 22,000 C. 22,000 and 34,500 D. 34,500 and 161,000
A. 120 and 480
When a tree contacts one electrical conductor, it may cause a: A. Phase to neutral fault B. Phase to phase fault C. Phase to ground fault D. Both a and b
C. Phase to ground fault
The minimum approach distance from energized, 50 kV conductors for nonqualified line clearance personnel is: A. 8ft B. 10 ft C. 12 ft D. 14 fr
B. 10 ft
The condition that allows electricity to flow from one object to another is called: A. Capacitance B. Conductivity C. Phasing D. Potential
D. Potential
