Electrical Grid 1: Chapter 9 - Distribution - Possible Test Questions Flashcards
1) Distribution lines are typically not longer than __ miles, while transmission lines may be several hundred miles long.
- 50 miles
2) How would you best visualize the distribution system when delivering power directly to the customer?
- as a series of local streets
3) Distribution lines are typically separated by an average of how many feet?
- 300 feet
4) What is the primary function of the distribution system?
- To receive electrical power from the transmission system and distribute it to customers at voltage levels that can be utilized by various types of customers.
5) True or false: The distribution system is almost entirely an alternating current system.
- True
6) Why is the design of the circuit important?
- It can have a big impact on the reliability to customers.
7) An energized wire is referred to as a _____.
- phase
8) A mainline distribution circuit is composed of either three phases, or __________________________.
- three phases and a neutral
9) Circuits consist of what?
- main lines
- tap lines
10) Main lines are also referred to as:
- feeder mains
11) Main lines will have larger conductors than:
- tap lines
12) Circuits that consist of four wire, three phase with a neutral conductor are called:
- WYE or star systems
13) On WHY systems it is also common to tap two phases and the neutral to serve light three-phase loads. This is sometimes referred to as what:
- “V” Phase Construction
14) When working in Distribution, define Primary:
- Primary is the high voltage portion of a distribution line.
15) When working in Distribution, define Secondary:
- Secondary is low voltage (120-480) and runs from pole to pole on overhead systems or padmount to pedestal in underground systems.
16) When working in Distribution, define Services:
- Services are also low voltages, but run from pole to customer on overhead systems or pedestal to customer in underground systems.
17) What is commonly known as a Loop Design?
- Underground systems that serve many customers or commercial customers are normally designed so that each transformer can be served from two directions.
18) The number of customers on the circuit is determined by what?
- The density of the area, the type of customers, and the capacity of the circuit.
19) List the different types of customers:
- Residential
- Commercial
- Agriculture
- Industrial
20) Residential Customers:
- Customer dwellings
21) Commercial Customers:
- Stores, shopping centers, medical facilities, etc.
22) Agricultural Customers:
- Irrigation pumps, grain storage, dairies, etc.
23) Industrial Customers:
- Large manufacturing plants, refineries, etc.
24) Utilities are obligated to:
- provide voltage at the meter in an acceptable range (114 to 126 volts) so customer equipment will run efficiently and not be damaged.
25) How much more expensive are underground systems compared to overhead construction for every miles of line?
- Four times more expensive
26) How tall are the majority of distribution poles?
- 35 to 55 feet
27) Typical nomenclature of a distribution line?
- Poles
- Supporting Brackets/Crossarms
- Insulators
- Primary Conductor Size
- Transformers
- Protective Equipment
- Capacitors
- Gang-Operated Switches
28) Post Insulators offer more:
- contact area at the point of attachment than pin insulators and are used with larger conductors.
29) Over the years, why have conductor sizes increased?
- Due to to the need to deliver larger amounts of power and reduce line losses.
30) Why are smaller conductors almost always found on tap lines?
- Because tap lines usually serve a limited amount of customers.
31) Most faults that occur on a circuit are:
- minor and temporary
32) Distribution systems are designed so that:
- when an outage occurs, as few customers as possible are affected, and outage time to those affected customers are minimal.
33) Protective equipment mainly consist of:
- Fused Cutout Switches
- Reclosers
- Sectionalizers
- Lightning Arresters
34) Fused Cutout Switches:
- Are designed to protect equipment, and the main line from faults that occur on a tap line.
35) Reclosers:
- Are devices that “reclose” the line after a temporary fault, which minimizes outage time.
36) A recloser has the ability to reclose up to ____ times to determine if a fault is permanent or temporary.
- four
37) Sectionalizers are installed to:
- Clear faulted sections from the line, and are coordinated with a recloser.
38) What is one of the main causes of damage to distribution lines and equipment?
- Lightning
39) Lightning or Surge Arresters are installed:
- to protect lines against equipment by diverting lighting to the ground
40) Voltage Regulators:
- automatically adjust the voltage levels up or down by 10% depending on the condition
41) Capacitors
- Improve the efficiency of the circuit and reduce the flow of power that does not perform any useful function.
42) Gang-Operated Switches
- Strategically placed throughout a main line to redirect power or to sectionalize a portion of line. They break load and all three phases open at the same time. (This prevents damage to customer three-phase equipment.)
43) Underground equipment is commonly classified as:
- padmounted or subsurface
44) Padmounted Equipment
- Above ground
45) Subsurface Equipment
- Below grade
46) Nomenclature of a cable (Out to In)
- Polyethylene (PE) Jacket
- Concentric copper shield wire (or neutral)
- Ethylene propylene rubber (EPR) insulation
- Semi conduction conductor shield
- Conductor
47) Most utilities instal underground cables in:
- conduit
48) Enclosures is a term:
- used to classify various types of concrete, fiberglass, or composite-type housings, which are used to splice cables, terminate cables, or to house equipment such as switches and transformers.
49) Manholes:
- Larger concrete structures, which are typically installed in lager cities to house heavy cables and equipment.
50) Pedestals:
- above ground and are used to splice low voltage secondary and service conductors.
51) Padmount transformers are installed:
- on a pad of either concrete or some form of polyurethane.
52) Subsurface type transformers are installed:
- either in an enclosure or a manhole.
53) Radial:
- Circuits are independent and radiant into the service area.
54) Radial Tie:
- Circuits can be connected automatically or manually at one or more points.
55) Network Grid Design:
- circuits are connected together, and the step-down transformers are connected together to form a low voltage grid network.
56) The network design is:
- the most reliable but also the most expensive.
57) Almost all distribution circuits:
- are four-wire: three phase conductors and one neutral conductor.
