week 4 (chapter 9) Flashcards
distribution lines are typically not longer than ____ miles?
50
compared to transmission, distribution is different because the?
direct delivery of power is more localized
shorter poles, closer together, more equip, about 300 feet apart?
distribution line
special applications for distribution DC power is used for ?
elevators and high rise buildings
distribution starts at the _____ and goes to the ______
substation/ customers
main lines on a distribution system are also called _____?
feeder lines
main lines have larger conductors than ____ lines?
tap
four wire, (three phases and a neutral) describes what circuit type?
WYE or star
primary is the _____ side, secondary is the ______ side, services run to the __________
high voltage, low voltage, consumer
underground systems that are designed so each transformer can be served from two directions are called?
loop feed design
number of customers on a circuit is determined by?
area density
type of customer
circuit capacity
utilities are obligated to provide voltages at the meter in an acceptable range so ?
customer equip will run efficiently and not be damaged
underground lines are about ____ times more expensive than overhead per mile
4
most distribution poles are wood, and range from ____ - ____ feet tall
35-55
why have distribution conductor sizes increased over the years?
need for more power and reduced line losses
the ultimate destination of all power lines is to a ?
transformer or transformer bank
protective equipment is designed to ?
distinguish temporary from permanent faults
fused cutout switches, re-closures, sectionalizers, and lightning arresters are all what?
protection equipment
what is the only way to tell the difference between an ungrounded WYE system and a delta?
back at the substation
three phases and a neutral describes what TYPE of circuit?
WYE
what type of 3 wire circuit would have no neutral with a transformer hooked up phase to phase?
Delta
what side of distribution is lower voltage (120-240), and runs from pole to pole on overhead or underground from pad-mount transformer to pedestal?
secondary
the lines that run from pole to customer or from pedestal to customer are?
services
underground systems that are designed so that the transformer can be served from two directions are called?
loop design
the number of customers on the circuit is determined by the ?
density of area
type of customer
capacity of the circuit
7200/12470 is what kind of voltage?
distribution
utilities provide power at the meter in a acceptable range so customer equip will?
run efficiently and not get damaged
underground systems main disadvantage is that they are?
expensive
underground systems are about ____ times more costly than overhead
4
what is the most popular choice for poles?
wood
what is used to mount equip like transformers, cutouts, riser terminations, lightning arrestors, and insulators?
support brackets and crossarms
offer more contact area at the point of attachment and used with large conductors?
post insulator
______ insulators are found commonly at dead end structures?
polymer
conductor sizes for distibution lines have increased over the years as the result of ?
the need for larger amounts of power and reduced line losses
tap lines can be smaller because?
they serve a limited number of customers
installed to protect equip such as transformers, and protect the main line from faults that happen on the tap line
fused cut-out switches
how many times does a recloser have the ability to reclose after a fault is detected?
4
________ are installed to clear faulted sections from the line, and they are coordinated with ?
sectionalizers/reclosers
_______ ______ are used to control the voltage out on the line and adjust it plus or minus ____%
voltage regulators/10%
capacitors are used to improve the _____ of a circuit?
efficiency
_________ reduce inductive load put on the line by transformers and large motors by introducing ?
capacitors/capacitive reactance
what does a gang operated switch do?
opens all three phases at the same time
underground equipment is commonly classified as either?
pad-mount or subsurface.
used to house heavy cables and equipment
Manholes
above ground/used to splice low voltage secondary to services
pedestal
what is the difference between a dead front and a live front pad mount transformer?
the live front has exposed primary voltage/dead front is all sealed
when the circuits are independent of each other leaving the substation and radiate to the service area it is called?
radial
when circuits can be connected manually or automatically at one ore more points, this is called?
radial tie
when the circuits are connected together, and the step down transformers are connected together to make a low voltage network, it is called?
network grid design
