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.
