Miscellaneous Flashcards
Name the two types of Underground Distribution Systems.
Duct and Vault
Direct Bury
Duct banks are usually made with?
Polyvinyl Chloride/PVC plastic or fiberglass, existing could be tile, concrete or steel.
What are the various paint markings and their corresponding meanings?
Red - Electrical
Yellow - Gas, oil, steam
Blue - Water
Orange - Communications
White - Proposed Structure
Green - Sewer
Purple - Irrigation
Pink - Temporary Survey Tape
At what depth is red caution tape laid out?
1 foot and above the underground cable
A bare ground wire/tracer wire can be laid along with cable for what purpose?
To locate the cable in the future. Or gather stray ground current.
The maximum tension for pulling cable is dependent upon what two factors?
Conductor size and how a pulling eye is attached.
What are the two methods of pulling wire
A crimp on or mechanical connected pulling eye will allow a higher pulling tension. Or a kellum or wire mesh grip around the jacket of cable. Kellum rated at less than 1000 lbs typically.
Define ampacity.
Is the current in amperes that a conductor can carry continuously without exceeding it’s temperature rating.
What is a thermal barrier? And name some.common examples.
Anything that is in direct contact with underground wire and impedes its ability to cool.
Conductor insulation, soil surrounding cable, poor air circulation in duct.
On high voltage transmission lines a minimum diameter conductor is required to avoid ______.
Corona Loss
With underground cable the voltage rating is based on what?
The property of the insulating material.
An electrical field around a conductor can be strong enough to break down or ionize the molecules in the air. This is referred to as what?
Corona
It takes energy to make corona, and corona loss results in power loss. Also radio and television interference. What are ways to minimize these issues?
Increase spacing between conductors and or ground
Increase surface area of conductors (bundle, or corona rings/grading rings)
Keep rough edges to a minimum to reduce voltage stress points
Aeolian Vibration is also known as what?
Wind vibrations
What is galloping by conductors?
The rise and violent drop of conductors caused by ice loading or moderate winds.
What is the conductivity of aluminum compared to copper?
62%
Properties to consider in conductor design include.
Weight per unit length, thermal expansion, elasticity, surface shape drag, fatigue resistance, dampening ability/resist galloping.
What is ACSR, AAC, AAAC, ACAR, AACSR
Aluminum Conductor Steel Reinforced
All Aluminum Conductor
All Aluminum alloy conductor
Aluminum Conductor Aluminum Alloy Reinforced
Aluminum Alloy Conductor Steel Reinforced
What size wire tongs should you use on conductors up to 1/0 and what size for conductors 1/0 and larger?
2” and 2 1/2”
Identify some MAD distances for various voltages.
5.1 to 15
2’2 phase to ground and 2’3” phase to phase
15 - 36
2’7” p to g and 3’ p to p
46.1 - 72.5
3’3” p to g and 4’ p to p
Where is a pole most likely to decay? And what is the typical life expectancy?
1 foot below ground level.
Typically 35 yrs.
What is the unit of measurement for capacitance?
Farads, however farads are an extremely small unit so line workers use kilovolt amperes reactive. kVAR
Voltage to the customer should be within this percentage plus or minus?
6%
Fault currents are highest near what?
The source, either substation or transformer.
Induced voltage is always in a direction that _______ the direction of the current.
Opposes
What does SCADA stand for? And what is its function?
Supervisory Control And Data Acquisition.
It is the communication system used to operate a distribution system.
Trenches or vaults deeper than ___ feet are considered confined spaces.
4
Define Capacitance
The ability of an electrical apparatus to hold a charge.
Can a line without a load carry current? And if so how much?
Yes it can carry a charging current of as much as 20 amps.
Name the colors for these various Guy Performs.
5/16”
3/8”
7/16”
1/2”
Black, Orange, Green, Blue
What are the 4 types of switches?
Air - circuit breakers, air break, disconnect
Oil - oil switches, OCB, OCR, and sectionalizer
Vacuum - vacuum circuit breakers, vacuum recloser
SF6 - circuit breaker, circuit switch, recloser
What are the two types of distribution voltage regulators?
Induction and step
What color are your truck/trailer connections?
Red Emergency
Blue Service
Green Electrical
At what depth is sloping, shoring or benching needed?
5 Feet
What are three types of loads fed by an AC circuit?
Resistive, Inductive, Capacitive
A step voltage regulator is basically a what?
Auto Transformer
Which way does electrical current flow?
Negative to positive
What must be done to the secondary side of a CT before heating up the primary side?
Short, shunt or hookup up to prevent high circulating current
When should a fuse interrupt the fault current?
Within the first 1/4 cycle
Can a sectionalizer open under load?
No!
When properly sharpened a gaff should not have a spike point but should function as a ?
Chisel
What is the definition of power?
The rate at which work is done.
What does a sectionalizer do?
It senses the operation of a back up device (recloser) and locks out when it is open.
Name two types of faults?
Temporary and permanent
Why does the recloser hold the line open for 60 or more cycles before it recloses?
To allow the sectionalizer to open while no current is flowing.
The ______ or equivalent span, is an assumed uniform span that most closely represents the various lengths of spans that are in the section of line being sagged.
Ruling
Two things to consider when sagging a conductor?
Temperature and span length
What is the minimum depth a pole should be set?
5 feet
Name some various factors that determine pole strength.
Diameter, weight, type (concrete, laminate, wood)
Poles are divided into how many classes depending on top circumference and circumference 6 feet from the butt.
Class 1 - 10 for normal strengths and
H1 - H6 for higher strengths
At what current does a recloser normally open?
Two times normal line current.
