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In larger cities, there is some distribution of _____ for special purposes such as elevators in high-rise buildings.
Direct Current
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What is the primary function of the distribution system?
To receive power from the transmission system and distribute it to customers at voltage levels that can be used.
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What are three characteristics that would make it easy to tell if a line is a distribution line?
- Shorter poles
- Closer together (about 300 feet)
- More equipment mounted on the poles
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A circuit in the distribution system that is composed of three phases and may have a neutral conductor. It is also referred to as a feeder main.
Main line circuit
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In a WYE system, one phase, two phases, or all three phases can be tapped off a main line. What are all three of these types of taps called respectively?
- single phase tap
- "V" phase tap
- three phase tap
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The most common system which has three phases and a neutral conductor, also known as a Star system.
WYE or grounded WYE system
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Three wire systems with no neutral conductor can be from a _____ or _____ source.
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A WYE circuit with no neutral conductor.
Ungrounded WYE
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In an ungrounded WYE or delta circuit, single-phase transformers are connected __________.
phase to phase
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What are the three main elements of a distribution line?
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The high voltage portion of a distribution line.
Primary
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The low voltage portion of a distribution line that runs pole to pole in overhead systems, or padmount to pedestal in underground systems.
Secondary
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The low voltage portion of a distribution line that runs pole to customer in overhead, or pedestal to customer in underground systems.
Services
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An underground system that is designed with a transformer on both ends to improve reliability and make it easier to work on the system.
Loop feed or Loop design
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What factors determine the number of customers on a circuit.
- The density of the area
- The type of customers
- The capability of the circuit
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What generally determines the voltage level of a distribution circuit?
Existing system voltages.
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Voltage levels in the distribution system are normally referred to by two number: a _______ voltage and a ________ voltage.
- phase-to-ground (line)
- phase-to-phase (system)
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What are the common distribution voltages?
2.4 kV / 4.16 kV 7.2 kV / 12.47 kV 7.62 kV / 13.2 kV 12 kV / 20.8 kV 14.4 kV / 24.9 kV 19.9 kV / 34.5 kV
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Utilities are obligated to provide voltage at the meter in an acceptable range to ensure equipment runs efficiently and is not damaged. If the service voltage is intended to be 120 volts, the meter would have to measure between _____ and ______.
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Construction of underground systems is approximately _______ times more expensive per mile than overhead construction.
four
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Distribuition lines are almost always installed underground in residential subdivision jointly with other ______.
utilities
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Utilities may choose to install underground distribution lines in areas where ________ is commonly encountered.
extreme weather
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Name the parts of a snatch block.
- Hook
- Safety latch
- Pivot pin
- Locking pin
- Shell
- Sheave
- Center pin
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Snatch blocks can reduce ________ in some rigging configurations.
Haul line tension
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Snatch blocks are commonly used when performing work on ________.
Transmission lines
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When inspecting the hook and safety latch of a snatch block, what are you looking for?
- Bent hook
- defective safety latch
- excessive wear at contact points
- metal fatigue
- rust
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Where is the weight rating found on snatch blocks?
Stamped or cast on the hook or shell, or in some cases a tag riveted to the shell.
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When inspecting the locking pin, pivot pin, and swivel of a snatch block, what are you looking for?
- Metal fatigue
- Rust
- Excessive wear
- Swivel operates freely
- Lubricate if recommended
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When inspecting the shell of a snatch block, what are you looking for?
- Cracks
- Breaks
- Sharp edges that could damage the rope
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When inspecting the center pin of a snatch block, what are you looking for?
Tightly seated and secure.
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When inspecting the sheave of a snatch block, what are you looking for?
- Sheave turns freely
- Excessive wear of bearing
- Cracks
- Sharp edges that could damage the rope
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If you cannot find the weight rating on a snatch block you should ___________.
remove it from service
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The tension on a snatch block is dependent on the _______ the rope is passing through.
angle
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When a rope passes through a block, there is a _____ and a ______.
-
As a rope passes through a snatch block, the end that is connected to the object being lifted is called the ___________.
line in
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What is the formula for calculating snatch block tension?
line out X angle factor
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If your snatch block becomes soiled you should ________.
Rinse it thoroughly and lubricate the sheave bearing per the manufacturers recommendations.
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What is the unique feature of a snatch block?
It can open near the swivel to trap the bight or middle of the rope.
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The tension applied to the snatch block determines the size of the _____, ______, and _______.
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Knowing the tensions involved with the snatch block will:
- Ensure a safe working environment
- Prevent damage to the equipment
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The strong points of transmission structures where snatch blocks should be placed are:
- The point where the structure meets the ground
- The top of the structure
- The point where the insulator is connected to the structure
- Where a horizontal member meets a vertical member
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Failure to place a block at a strong point when lifting heavy conductors could jeopardize the:
- Safety of the crew
- Stability of the structure
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What is the formula for calculating line out tension after passing through a snatch block?
Line in X friction (1.1)
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The distribution system is different from the transmission system because the direct delivery of power is more _________.
localized
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What five items impact the reliability of a distribution system?
- Size and type of structures
- Size and type of conductors
- Route of the power line
- Location of protective equipment
- Overhead or underground system
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What is the primary use of a snatch block?
To redirect the pulling forces applied to a haul line, rope, or a moving load.
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A tap in the middle of a line where there is no pole present is called a ______.
flying tap
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Where does the main line radiate from?
The substation
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A grounded WYE has a neutral line or __________ line.
earth potential
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What voltage range is considered "low voltage" in the distribution system?
0 - 600 volts
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Name the four types of customers in the distribution system.
- Residential
- Commercial
- Agricultural
- Industrial
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What two types of customers make up the bulk of a utilitie's customer base?
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What is the primary objective of the Distribution system?
To deliver power to the customer with a minimum amount of loss.
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The main lines and the tap lines are both part of one _________.
circuit
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What is the formula for calculating Line Voltage when given a system voltage?
System voltage divided by 1.732
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What is the formula for calculating System voltage when given a line voltage?
Lince voltage times 1.732
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