Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

JL Exam > study guide, notes > Flashcards

study guide, notes Flashcards

1
Q

why is a closed Y closed delta bank primary neutral floated?

A

to prevent balance or bank action - to prevent burning out the two remaining transformers when on fuse blows and creates an open, the bank continues to provide 3 phase power using two transformers instead of 3. Also to prevent back-feeding the line when a line becomes de-energized, or to prevent backfeeding the hi side of the transformer if the fuse becomes blown.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

why is a forth cutout installed on the primary neutral of a closed wye closed delta bank?

A

to prevent ferroresonance - when you lose your 3rd potential, your reactance and capacitance in the bank can build up to 10X the normal voltage, closing the 4th cutout (connecting the primary neutral bus to the system neutral or ground) will balance the voltage on the neutral bus preventing ferroresonance.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

on an open bank what KVA capacity do you have of the two transformers being used?

A

86.6%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what must be done before climbing above a de-energized transformer?

A

isolate the secondary leads or ground with approved equipment.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what do you need to do on a closed wye closd wye transformer bank?

A

tie the primary and secondary neutral bus to prevent high secondary voltages.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what purpose does the case ground serve on a transformer?

A

to ground the case of the transformer and acts as your neutral on a single bushing transformer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

how do you find full load current?

A

KVA divided by primary or secondary voltage used. On primary use the voltage the transformer is using. On secondary use larger voltage supplied, if paralleled use paralleled voltage.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

how do you size two transformers to carry 3 phase balanced load?

A

multiply the 3 phase load by 57%. This would be the load on each transformer. The single phase load is added only to the “lighter transformer”

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

how to fuse wye connected primary

A

KVA divided by primary voltage used, multiplied by design factor of 2 (utility spec will vary) round to nearest fuse size

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

how to fuse closed delta connected primary

A

KVA divided by primary voltage used multiplied by 1.73, multiplied by design factor of 2 (utility spec will vary) round to nearest fuse size.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

how to fuse open delta primary

A

cutout with 2 bushings attached: KVA divided by primary voltage used multiplied by 1.73, multiplied by designed factor of 2 (utility spec will vary) round to nearest fuse size.
cutout with 1 bushing attached: KVA divided by primary voltage used, multiplied by designed factor of 2 (utility spec will vary) round to nearest fuse size

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

transformer core; how does it work, what is made of

A

the core is the part of the transformer in which the magnetic field oscillates. it consists of laminated steel, insulated, and wound to a desired shape for the coils. the purpose of this thin sheet is to reduce the core loss and the heating produced in the core by insulating each sheet from the other.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

coils; what do they consist of, size

A

the coils consist of an insulated wire or bus bar wound around a wooden block to fit the core; the fewer the turns, the larger the wire. the insulation on the wire depends upon the voltage to be supplied to the coils. the two coils are referred to as an input and output coil. There is no electrical connection between the primary and secondary coil in a distribution transformer.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

how to get turns ratio of a transformer

A

primary voltage used divided by highest secondary voltage used. if paralleled use paralleled voltage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

describe transformer tank

A

the tank is used as a means for enclosing the assembled core and coils. it acts as a protective barrier for the high voltage and current carrying parts, and holds the coolant or transformer oil.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

transformer bushings; what are they used for, what are they made of?

A

used to bring the high and low voltage leads from the coils to the outer edge of the tank. the bushings are made of a strong wet-process porcelain which insulates the line leads form the tank.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what are the 3 main parts of a CSP transformer?

A

circuit breaker on secondary side; external tank mounted lightning arrestor; internal high voltage fuse mounted in the primary bushing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what are the two basic types of lightning arresters?

A

expulsion and valve

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what are the two main enemies of transformers?

A

high voltage surges and heating caused by overloading

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

on a CSP transformer what coil is the circuit breaker on?

A

secondary

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

transformer taps are used for what two purposes

A

to correct low primary voltage and to control voltage to a customer ( raise and lower voltage)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

standard taps for transformers are what?

A

5 taps total, middle tap 100%, then 4 - 2.5% taps, 2 - above 100%, 2 - below 100%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

when changing taps on a transformer, which coil are you affecting? primary or secondary?

A

primary

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what happens to the primary coil when changing the taps?

A

increasing the tap adds to the number of turns of the primary coil; therefore, lowering the secondary voltage and lowering the taps reduces the number of turns of the primary coil raising the secondary voltage.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

when determining what tap to select on a transformer tap changer, what formula can be used?

A

actual voltage divided by desired voltage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

what determines the amount of voltage drop when a transformer is fully loaded?

A

impedance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

impedance must be how close when paralleling or banking transformers?

A

plus or minus 10%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

how much capacity would you gain from using a closed delta bank instead of an open delta bank?

A

42.3%; 100% minus 57.7%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

open wye - open delta or open delta - open delta bank KVA ratings Rules of thumb.

A
  1. 6% of the two transformers

57. 7% of the initial three (if going form closed to open)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

how to size the transformers on a open wye - open delta or open delta - open delta bank

A

multiply the 3 phase load by 57%, this is the load on each transformer. the single phase load is added only to the lighter transformer.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

in closed wye - closed delta or closed delta - closed delta banks how is the load split between the transformers

A

the lighter pot carries two-thirds of the single phase load and each power pot carries one-third of the single phase load the 3 phase load splits one-third on each transformer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

conditions exist on a wye-delta closed bank if the primary neutral bus is tie to the system neutral and one or two primary fuses are blown?

A

if a primary fuse is blown:

  • the bank capacity is reduced to 57% of bank rating, possibly causing overloaded and transformer failure.
  • also, the voltage measured on the neutral bus is on half the phase to ground voltage or when two primary fuses are blown, voltage on the neutral bus is at full phase to ground voltage (these two conditions also exits every time a closed wye-delta bank is energized or de-energized)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

in open banks can CSP transformers be used

A

yes if future plans do not call for the closing of the delta

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

in wye-delta and delta-delta closed banks can CSP transformers be used

A

yes; only on 240 volt and 480 volt 3 phase 3 wire only. if used on for wire systems and the secondary breaker of the CSP opens it would act as an open neutral causing high secondary voltages.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

in wye-wye closed banks can CSP and single bushing transformers be used?

A

yes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

in delta-wye closed banks can CSP and single bushing transformers be used?

A

only two bushing transformers can be used, 2 bushing CSP transformers can be used

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

what are the five types of stranded conductor shapes?

A

concentric round, round, compact round, compact sector, annular, segmental

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

how are rubber gloves rated; phase to phase or phase to ground?

A

phase to phase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

what type of hard hat is worn by electrical workers? how many volts are they tested to?

A

class E, 20,000 volts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

what is the minimum size of protective grounds?

A

equipment must be capable of conducting the maximum fault current that could flow, for the time necessary to clear the fault, grounds must have ampacity greater than or equal to that of no. 2 awg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

what 5 steps are taken for proper grounding?

A

need a low-resistance path to earth, clean connections, tight connections, connections made at proper points, adequate current carrying capacity or grounding equipment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

what sizes do capacitors come in?

A

15, 25, 50, 150 and 200 KVA with the 100, 150 and 200 sizes most common

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

what is the proper procedure for pole top rescue?

A 
call loudly to the injured employee
call for help
evaluate the situation
plan the rescue
climb to the proper rescue position
asses the casualties condition
rig the rescue rope or handline 
lower victim to the ground
administer first aid/cpr
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

formula for peak value

A

1.414 x RMS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

formula for RMS value

A

.707 x peak

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

RMS is also known as what?

A

effective voltage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

what are the six types of substations?

A 
step-up transmission
step-down transmission
distribution
industrial
customer owned
converter
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

what is a permanent fault?

A

where the circuit cannot be automatically reclosed, a line crew is needed to repair and re-energize the circuit

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

what is line loss? and formula

A

the amount of voltage lost by pushing current through resistance. I2XR

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

what are harmonics?

A

AC and voltage disturbances that can be represented by sine waves, but are at different frequencies of the fundamental 60 hertz sine wave: 30, 120 - 2nd harmonic, 180 - 3rd harmonics

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

how much more load can a wye system handle over a delta system?

A

73% more

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

a fire extinguisher used in an electrical environment must have what rating?

A

must be a C rated in combination with another rating

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

what is the purpose of transpositions?

A

to cancel out induced voltages and reduce electromagnetic fields that interfere with open wire telephone circuits

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

what type of transformer is used on series street lighting? why?

A

a constant current transformer, it is used to raise and lower the voltage automatically, depending on the number or street lights in the circuit. a constant current has to be maintained because if one lamp burns out the total resistance of the circuit becomes smaller and current would tend to increase.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

what are the two basic distribution voltage regulators

A

induction and step

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

an induction voltage regulator is connected how with the load?

A

series

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

induction regulators as a rule have two series coils, by operating the coils in series how will they be rated? when the coils are paralleled?

A

+-10%, when in series, +- 5% when in parallel but carry twice the amperage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

the step voltage regulator is basically what?

A

an auto transformer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

the step voltage regulator is connected how with the line?

A

series

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

can the step voltage regulator coils be paralleled?

A

no

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
61
Q

what do the load bonus settings do on a voltage regulator?

A

they are mechanical stops on the position indicator dial. allows the regulator to handle larger amounts of current, used when the voltage regulator becomes overloaded.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
62
Q

is external fuse protection required for voltage regulation

A

no, a regulator can be connected and disconnected form the power lines using a regulator by-pass switch

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
63
Q

what must be done before the by-pass switch is operated on a regulator?

A

the voltage regulator indicator must be in the neutral position

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
64
Q

should surge arrestors be installed on voltage regulators?

A

yes on the source and load side

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
65
Q

T/F, two cutouts and arresters are needed on a wye connected transformer

A

false

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
66
Q

T/F, series can happen when you contact two current carrying sources at the same time

A

false - second point of contact

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
67
Q

T/F, if you have high primary voltage on a transformer your secondary voltage will be low

A

false

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
68
Q

T/F, name plates are only needed if you don’t know your phase to phase voltage

A

false

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
69
Q

T/F, low voltage rubber gloves are needed if you are checking voltage on a new transformer

A

false

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
70
Q

T/F, a 250 KVA transformer would have a additive polarity

A

false, below 200 KVA or 8660 volts is additive all others are subtractive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
71
Q

T/F you can connect the H2 bushing on a single bushing transformer only to the neutral

A

false, case ground and secondary neutral tie strap is considered the neutral and should be tied down.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
72
Q

T/F, a transformer can usually only be connected to one circuit voltage on the primary side

A

true

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
73
Q

T/F, a delta connection will allow you to balance the system voltage better than a wye connection

A

false

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
74
Q

T/F, the unlike bushings are connected together to make a wye connection

A

false

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
75
Q

T/F, you must always use the same phase and bushing when paralleling transformers

A

false, same phase not same bushing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
76
Q

T/F, a transformer whose primary voltage rating is 4160/7200 volts can be used on a 7200/12470 system

A

false

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
77
Q

T/F, a transformer whose secondary voltage rating is 277/480 has two secondary bushings

A

true

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
78
Q

T/F, a 250 KVA transformer whose secondary voltage rating is 120/240 volt has three secondary bushings

A

false, transformers 100KVA and over have 4 secondary bushings

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
79
Q

what are the two basic function of oil in a transformer?

A

cooling and insulation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
80
Q

underground loop fed transformers are connected through

A

a buss bar

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
81
Q

how many phases of a feeder must be present to connect the open delta-delta bank?

A

must have 3 phases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
82
Q

what are the three most important things that should be considered from the nameplate of a transformer before installing it in a transformer bank

A

impedance, polarity, voltage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
83
Q

how are the internal secondary leads connected in parallel on a conventional transformer?

A

AC-BD, alley cat-bad dog, head to head-tail to tail

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
84
Q

in common distribution transformers the tap changer is located in which coil?

A

primary coil

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
85
Q

what is the main advantage of a wye secondary over a delta secondary?

A

efficiency - because the load is balanced

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
86
Q

two 50 KVA transformers are connected open-delta/open-delta. what is the capacity of the bank?

A

50 KVA x 2= 100 KVA, X 86.6%, 100 x .866=

86.6 KVA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
87
Q

what types of transformers are used for primary metering?

A

current and potential

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
88
Q

transformers are additive polarity if their KVA rating is less than?

A

200 KVA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
89
Q

transformer tap changers are located where?

A

located in the oil on the primary coil and the control handle is located above the oil

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
90
Q

how are lightning arrestors connected?

A

in series with a resistor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
91
Q

what 3 advantages does bundling conductors have?

A

cuts down on corona loss, lower line loss, 50% of the reactance of a single conductor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
92
Q

define corona

A

an electrical discharge at the surface of a conductor accompanied by the ionization of the surrounding atmosphere. it can be accompanied by light and audible noise.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
93
Q

when banking transformers, what’s a rule of thumb for the max safe rating for the bank?

A

three times the KVA of the smallest can

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
94
Q

what is the element in apparant power that does not do any work?

A

KVAR

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
95
Q

1 watt equals?

A

one amp flowing under pressure of 1 volt

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
96
Q

how many watts equal on horsepower?

A

746 watts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
97
Q

define impedance

A

total opposition to flow of current in AC circuit, measured on ohms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
98
Q

define inductance

A

ability to induce a magnetic field on a conductor measured in Henery’s

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
99
Q

what type of transformer is used for series street lighting?

A

constant current transformer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
100
Q

3 types of faults?

A

open circuit, short circuit, grounded fault

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
101
Q

what’s the most common reason transmission line failure?

A

insulation flashover

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
102
Q

vector is what?

A

line having definite length and direction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
103
Q

how is a current transformer connected?

A

series

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
104
Q

how is a potential transformer connected?

A

parallel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
105
Q

define circular mil

A

a circle with a diameter of one one-thousandth of an inch

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
106
Q

volts and amps are ________ proportional

A

inversly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
107
Q

what percent of electrical contractors worked in the electrical field beforehand?

A

83%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
108
Q

3 main causes of accidents

A

human element, acts of nature, mechanical failure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
109
Q

natural enemy of rubber gloves

A

oil and grease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
110
Q

how often are hot sticks tested?

A

every 2 years

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
111
Q

what would you use to cover a primary insulator?

A

rubber hood

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
112
Q

max exposure for rubber goods is?

A

36KV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
113
Q

an enclosed space at 5 feet requires what?

A

mechanical retrieval device, (tripod)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
114
Q

oxygen level in an enclosed space: max, normal, minimum

A
  1. 5 max
  2. 8 normal
  3. 5 minimum
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
115
Q

what’s the greatest risk of bloodbourne pathogen?

A

hepatitis B

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
116
Q

minimum overlap distance of an extension ladder is

A

3 feet

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
117
Q

what’s the safe distance from machinery for swing radius

A

6 feet

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
118
Q

what is found in PVC that can cause cancer

A

carcinogens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
119
Q

how many IBEW vice presidential districts

A

11

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
120
Q

order that union meeting is conducted

A

Roberts Rules of order

121
Q

type of light is used in fiber optic

A

infrared

122
Q

extra high voltage is considered what range

A

34KV and up

123
Q

how long (in cycles) does a recloser hold the line open for?

A

60 cycles, a second

124
Q

a 3 phase line can use wire __% smaller and hold the same load as 1 phase 2 wire system

A

75%

125
Q

defibrillation can occur from how much current for how long?

A

1 amp for .01 of a second

126
Q

how often to test ground cables?

A

every 2 years

127
Q

how many feet to keep away from lines in a sub

A

15 feet

128
Q

turns ratio and voltage ratio are _______ proportional

A

directly

129
Q

power factor =

A

true power divided by apparent power

130
Q

when do you test rubber blankets and sleeves

A

every 12 months

131
Q

what type of device is a transformer?

A

an electromagnetic device

132
Q

what size hole for a 5/8” bolt

A

11/16”

133
Q

why do we put aluminium over copper?

A

salts in the copper will corrode the aluminium

134
Q

percent efficient of knots, hitches and splices?

A

knots 50%
hitches 75%
splices 85%

135
Q

how many lumens = one candle power?

A

12.57

136
Q

where should capacitors be installed

A

near the customer

137
Q

which way does a capacitor improve power factor in line, towards the sub or away

A

from the point installed back to the sub or source

138
Q

in capacitors what gives them more capacitance?

A

the size of the plate, larger the plate the more capacitance, the closer the plates the more capacitance

139
Q

what does a capacitor consist of?

A

two thin pieces of metal or foil separated by a dielectric or insulator, and is generally rolled or folded. it is then inserted in a metal case along with a discharge liquid. at the top are one or two high voltage bushings

140
Q

transformers work on the principal of

A

mutual induction

141
Q

what does KVAR stand for?

A

kilo volt amps reactive

142
Q

what is polarity in a transformer?

A

direction of current flow between the primary and secondary

143
Q

what do you use when raising conductor to prevent conductor from falling to other side

A

holding tong

144
Q

what determines the strength of magnetic field when current flows through a conductor

A

amount of current

145
Q

OSHA Transmission and Distribution is covered under what article

A

1910.269

146
Q

OSHA new construction is covered by

A

1926 of standard 29 CFR and 1926.957 (a)(1)

147
Q

formula for fall line load

A

weight of object + (10% weight of object X # of sheaves
rope passes over )
___________________________________________
mechanical advantage

148
Q

T/F, horizontal axis is a group that modern wind turbines fall into

A

true

149
Q

T/F in an inductive circuit, the voltage leads the current by 90 degrees

A

true, ELI the ICE man

150
Q

T/F the external air gap of a distribution class surge arrester is designed to prevent sparkover by normal system voltage if the lightning arrestor fails

A

true

151
Q

T/F if lightning arrestor connections are too long, too much resistance might force high voltage surges into the transformer.

A

true

152
Q

T/F, in wiring the arrestor connections, the wire must be smaller than the primary drop

A

false

153
Q

what is the safety factor of new rope compared to old rope

A

new rope is 5 to one, old rope is 10 to one (6 months is considered old)

154
Q

what three things do you look for in and injured person?

A

response, bleeding, pulse

155
Q

how is pole strength determined?

A

the classification from 1 to 10 determines the strength to resist loads applied 2 ft from the top of the pole.

156
Q

what 3 things determine pole depth?

A

soil conditions, height of pole, and location

157
Q

can porcelain withstand more compression or tension

A

compression

158
Q

what is the main advantage of pin type insulators?

A

cheaper and requires a shorter pole for the same overhead clearance

159
Q

what is a voltage regulator and how does it work?

A

it is an electrical apparatus used to regulate voltage at 10% above or 10% below line voltage at 32 steps of 5/8%. (the high side is connected in parallel and the secondary is connected in series)

160
Q

what is a constant current transformer used for and what things must you remember about them?

A

it is used for street lighting. you must connect the secondary side first, it has movable secondary coil

161
Q

what are the parts of a rope?

A

the fibers, the yarns, and the strands

162
Q

can a line without a load still carry a current?

A

yes it can carry a charging current of as much as 20 amps

163
Q

why do reclosers hold the line open longer on the third and fourth operations?

A

to give the secionalizer time to operate.

164
Q

a recloser must always be backed up by what?

A

a sectionalizer.

165
Q

a sectionalizer only operates under what

A

no current conditions

166
Q

what ratio makes up power factor?

A

true power to apparent power

167
Q

what is a counterpoise?

A

grounding grid for a sub station or a footer on a transmission line

168
Q

how does capacitor time switching work?

A

it adds capacitors to the line when the load is heavy, and takes them off when the load is light.

169
Q

when fuzzing insulators do you go by length of arc or by intensity of sound?

A

intensity of sound

170
Q

what device breaks the arc on air break switches?

A

arcing horns

171
Q

what is line loss?

A

the amount of voltage lost by pushing a current through a resistance.

172
Q

in general, the maximum bending radius of cable is how many times the diameter of the cable?

A

8 times and should not be bent when temperature is below 14 degrees F

173
Q

which windings of the induction regulator is mounted so it can rotate on its’ axis?

A

shunt windings

174
Q

what is the maximum ground resistance that a structure can have?

A

25 ohms

175
Q

heavy loaded lines are protected by the use of

A

OCB (OCR), sectionalizers, and fuse cutouts

176
Q

sagging charts are used to show what 2 things for spans to a line where tension is used?

A

distance and temperature

177
Q

what is a snatch block?

A

a closed sheave

178
Q

what 2 things should be checked before final sag is started?

A

anchors and guys

179
Q

what is bus work in a substation?

A

aluminum or copper bars that connect equipment together

180
Q

in a standard distribution transformer, are the primary and secondary coils physically connected together?

A

no. they are magnetically coupled together

181
Q

how are straight line pole generally set?

A

gain to gain or back to back

182
Q

is a series street line connected in line

A

yes

183
Q

what is the force which makes electricity flow?

A

EMF electromotive force

184
Q

in a series street lighting circuit, what type of transformer is used? what happens when one bulb goes out?

A

constant current transformers. the transformers secondary windings is movable, so when one light burns out, it moves, adjusting the voltage. (amps stay the same)

185
Q

how far must unqualified employees stay away from apparatus energized up to 5,000 volts

A

10 feet

186
Q

a shock victim received several burns, but was not killed. what would you suspect, considering the amount of current drawn by his body?

A

under .2 amps

187
Q

adding parallel loads to a circuit will ________ total circuit resistance and ________ the total circuit current.

A

decrease, increase

188
Q

what is the polarity of electrons when they enter a load? when they leave?

A

negative, positive

189
Q

how does an analog meter operate?

A

on the magnetic principal that like poles repel each other

190
Q

list the 3 steps that should be followed when reading a multimeter.

A

determine what the meter indicates, determine the full scale value of the mater, read the meter.

191
Q

what are 2 basic types of analog ohmmeters?

A

the series and the shunt

192
Q

name 2 advantages for 4 wire feeders over 3 wire feeders

A

cheaper to build, more efficient

193
Q

what is created whenever current flows through a conductor?

A

a magnetic field is created

194
Q

list the three factors which determine the amount of voltage that will be induced in a transformer.

A

the number of turns of the wire, the strength of the magnetic field, the speed of the cutting action.

195
Q

how many primary phases are used to connect a single phase distribution transformer on a 3 phase 3 wire circuit?

A

two

196
Q

what is the current in a transformer winding when connected in delta?

A

windings current = line current/1.73

197
Q

name 3 important factors in determining the size of line conductors

A

line voltage; the amount of power to be transmitted; mechanical strength.

198
Q

what are the best ways to locate a fault in the shortest amount of time?

A

with the use of faulted circuit indicators, patrolling the line, customer calls in .

199
Q

what is a cable fault?

A

when the insulation on the wire or cable does not sufficiently confine the voltage.

200
Q

what rule must be observed when hauling dynamite and the caps in the same truck?

A

in separate containers, in separate compartments.

201
Q

what is a megger?

A

an ohm meter that measures high resistance.

202
Q

the most common defect in insulators are

A

cracks in the porcelain.

203
Q

what is the national electrical code definition of medium voltage ranges?

A

from 2001 volts to 3500 volts

204
Q

define a splice

A

the joining of two or more conductors

205
Q

list the 3 major components of an implosive compression splice for an ACSR conductor.

A

steel sleeve inner. aluminum sleeve outer, aluminum sleeve.

206
Q

what is a reflector?

A

it is a surface that stops light ray and redirects it in a desired direction.

207
Q

what are reflectors made of

A

porcelain, metal, silvered glass

208
Q

gaseous conduction lamps have circuit limiting devices called

A

ballasts (choke coil)

209
Q

name 3 devices that are used to protect lines from abnormal voltages

A

surge arresters, shield wire (static wire), protector tubes.

210
Q

a transformer is usually loaded to what percent of the name plate voltage rating?

A

125 to 150%, for 1 to 2 hours at a time

211
Q

how is a phase sequence designated?

A

clockwise or counterclockwise: (123 or 321)

212
Q

what is the maximum resistance that a ground should have?

A

25 ohms

213
Q

when using a test instrument to measure resistance, what 3 factors effect the amount of resistance?

A

resistance of the electrode, the contacts of resistance between electrode-earth, resistance of the surrounding earth.

214
Q

how many indicating pointers does a maximeter have?

A

two

215
Q

can a maximeter be removed from a conductor, reset to zero, and immediately be placed on another conductor/

A

No, it must be allowed to cool

216
Q

what is the RMS value of AC equal to?

A

.707 times the peak value

217
Q

what is the peak value of AC equal to?

A

1.414 times the RMS value

218
Q

alternating circuit loads are generally described as being?

A

resistive, inductive or capacitive loads

219
Q

list the 3 factors which determine the amount of voltage that will be induced in a conductor.

A

the size, type and length of the conductor

220
Q

what 3 factors determine the capacitance of a capacitor?

A

the area of plates, the distance between the plates, the type of dielectric used.

221
Q

list 4 type of controls that are used with capacitors

A

time switched, time-temp, voltage, current

222
Q

list 5 factors which effect the amount and type of capacitor banks installed on distribution circuits

A

length of the circuit, residential lines, rural lines, commercial lines, industrial lines

223
Q

what do you do when you size up a distribution job?

A

identify all the hazards on the pole.

224
Q

name 3 types of wire tong saddles

A

pole type saddles, cross arm saddles, tower saddles

225
Q

when does a recloser usually lock out?

A

after 4 operations

226
Q

name the 3 basic safety practices that you can follow to avoid many safety hazards

A

planning jobs, inspecting job sites, and wearing PPE

227
Q

electrical fires are classified as what type of fires?

A

class C fires

228
Q

can a primary cell be recharged?

A

NO

229
Q

list 4 factors that determines a cell’s circuit capacity.

A

the type of cell, rate of current flow, voltage, and lingth of time involved.

230
Q

list 3 types of air switches

A

circuit breaker, air break, disconnect

231
Q

name 3 types of overhead line faults

A

short circuit, open circuit, and ground

232
Q

why are capacitors less flexible in controlling voltage than other voltage regulating equipment?

A

they are switched on and off in the circuit

233
Q

describe the appearance of a capacitor which would be installed on a distribution circuit

A

a long rectangle box with 1 or 2 high voltage bushings, containing no secondary connections and has no moving parts.

234
Q

list the 3 most common sizes of capacitors

A

100, 150, and 200 KVA

235
Q

why do most underground distribution circuits use looped cable routes?

A

to permit the lineman to isolate the faulted cable between 2 transformers and restore electrical service to the customer

236
Q

which type of control is usually provided at a sub-station?

A

local control

237
Q

define harmonic

A

a vibration whose frequency is an integer multiple of fundamental frequency

238
Q

how are harmonics created?

A

by non-linear loads of the power system

239
Q

in new 3 phase installation, what will help eliminate harmonic problems?

A

balancing loads or providing oversized neutral conductors

240
Q

a typical crystalline silicon cell produces how much power?

A

approximately 1 watt of power

241
Q

what is the laminated core of a transformer made of?

A

steel

242
Q

what do you test blasting caps with before using them?

A

a galvanometer

243
Q

what do you do if a blasting cap misfires?

A

wait 1/2 hour before investigating, then dig next to the cap, set another charge to set it off.

244
Q

what is the current limiting properties of an inductor called?

A

inductive reactance.

245
Q

rubber glove cuffs are rate at what KVA?

A

10,000 volts per one inch

246
Q

what is the purpose of rubber gloves sticking out of the protectors?

A

to protect against flash over.

247
Q

what is the advantage of a wye over a delta system?

A

a wye can carry 73% more load current than a delta and provides a balanced load.

248
Q

how do you determine the mechanical advantage using block and tackle

A

count the number of lines not to include the fall line to determine the mechanical advantage.

249
Q

what is a semicon for?

A

dispenses eddy currents

250
Q

what are the 4 ways of sagging?

A

dynamometer, transit with targets, sagging with a stop watch, unsagwatch

251
Q

why is it dangerous to a lineman to open a primary neutral?

A

it may cause a fire because the neutral carries the unbalanced load of all single or 3 phase circuits

252
Q

what is used when paralleling 2 secondary circuits?

A

voltmeter

253
Q

what is the procedure for tagging

A

identify, test, isolate, ground

254
Q

single phasing occurs when one fuse blows on a wye-delta bank with the primary neutral bus grounded.

A

false, when one fuse blows and the primary neutral bus is grounded, the bank continues to operate as before except at 57% capacity. that is one reason we float the primary neutral on a wye delta bank.

255
Q

explain the procedure of paralleling an additive and subtractive transformer

A

ground the cans, install both neutrals, heat up top side of one can, install the secondary , heat up the other can and phase the secondary with a meter

256
Q

define transformer

A

an electrical apparatus that changes electrical energy from one potential to another potential

257
Q

can you ground a transformer in a delta power bank?

A

yes only one can

258
Q

what are four ways to cool transformers?

A

air oil fans fins

259
Q

what function does oil have in an transformer?

A

to cool and insulate

260
Q

explain the procedure for paralleling 2 transformers

A

select can with proper voltage impedance and check polarity, hang can connect all grounds and the neutral, connect primary to same phase, phase secondary legs with volt meter and make proper connection

261
Q

when working in an unknown area on a distribution line, low do you verify for yourself what the primary voltage of the line is?

A

check the name plate on the transformer or with phasing sticks

262
Q

what are the dangers of using electronic blasting caps under a circuit?

A

the caps could be set off by induction or by communication interference or the blast could blow lead wires into primary

263
Q

primary metering requires what kind of transformers?

A

potential transformer and current transformer

264
Q

mechanical jumpers should be checked for what 3 things?

A

good insulation, proper wire size (adequate current carrying capacity and tight (clean) connection

265
Q

when ground framing H structures, what must be done before putting on knee braces and X braces

A

make sure the structure is square

266
Q

what precaution should be taken when de-energizing pole top termination coming from underground?

A

to eliminate capacitance form the underground feed

267
Q

why does underground cable rated above 5 KVA require a grounded sheild?

A

to bleed off capacitance

268
Q

when 3 transformers are banked together closed wye closed wye why is the midpoint on the primary side grounded?

A

to prevent excessive and fluctuating voltage on the secondary side

269
Q

what is the advantage of a 3 phase wye secondary?

A

more efficient, you can supply single phase and 3 phases, more balanced load

270
Q

on an open wye open delta, what will occur if the primary neutral becomes disconnected from the system neutral?

A

one half of the phase to ground primary voltage will be present

271
Q

name 3 devices that are used to protect lines from abnormal voltage?

A

surge arresters, shield wire, protector tubes

272
Q

a transformer is usually loaded to what percent of the name plate voltage rating?

A

150% to 150% for 1 to 2 hours

273
Q

how is phase sequence designated?

A

clockwise or counter - clock wise (ABC CBA)

274
Q

how to find right tap when using tap changers?

A

find turns ratio, primary rating divided by secondary rating divide actual primary voltage by the turn ratio, gives you 100% voltage then divide by that by all percentages, or actual voltage divided by desired voltage

275
Q

what does the term frequency mean in relation to AC current and voltage?

A

the number of complete cycles that occurs in a given time measured in hertz

276
Q

what is the maximum resistance that a ground should have?

A

25 ohms

277
Q

what is the purpose of the internal discharge resistor installed in a capacitor unit?

A

will reduce voltage 50 volts or less within 5 minutes

278
Q

list for reasons why capacitors may be installed on a distribution circuit with a lagging power factor?

A

reduces lagging components of circuit current
increase voltage level at the load
increase power factor of the source generator
reduce investments in the system facilities

279
Q

alternating circuit loads are generally described as being

A

resistive, inductive or capacitive loads

280
Q

list 3 factors which determine the amount of voltage that will be induced in a conductor

A

the size, type and length of conductor

281
Q

what 2 things must be checked when selecting a pulling grip for use?

A

correct size (diameter) and correct type of wire

282
Q

on a 25 KVA transformer nameplate rating 7620/120/240 volt what would the amperage values on the secondary side be?

A

KVA/voltage on secondary side 25000/120= 208.33, 25000/240= 104.16 (if question doesn’t specify if the secondary coils are series or paralleled give both)

283
Q

what is the difference between 3 wire single phase and 3 phase secondary?

A

2 phases and a neutral, 3 phases and a neutral

284
Q

how do you field test a phase set?

A

test by battery or or on an energized line phase to ground voltage and phase to phase voltage.

285
Q

what is the purpose of a stress cone?

A

to dissipate eddy currents

286
Q

what is as autotransformer?

A

it is a one-winding transformer the same winding is used for both the primary and secondary small-efficient transformer

287
Q

what is the range of most transformer tap changers?

A

95% to 105% to increase voltage lower the taps to decrease the voltage raise the taps

288
Q

if a line is balanced with 10 amps on A phase, and on B phase, and on C phase, how many amps are on neutral?

A

Zero (0) amps, well balanced

289
Q

what does getting in series mean?

A

it is getting between the line and load or between the line and ground or between the line and the line in essence becoming a human mack

290
Q

how would you check rubber gloves in the field?

A

check the voltage rating the last inspection date give rubber gloves visual and air test give a visual check for cuts and embedded materials on protectors

291
Q

what is a 3 phase transformer?

A

3 single phase transformers in one can using one core

292
Q

if one circuit is regulated (with a voltage regulator) and the other unregulated can they be tied together without other immediate action?

A

no the circuit that is regulated must be set to zero before they can be tied in with a phasing set

293
Q

explain the procedure for removing grounds on a distribution or transmission line

A

furthest to nearest then ground

294
Q

in a wye underground system shielded cable requires the installation of a neutral where concentric cable does not

A

cable that does not come with a built in concentric cable requires a neutral be laid next to it

295
Q

how do you determine the rotation of motors from the given phase sequence?

A

write the sequence out 3 times if ABC shows up then its CW if not then CCW

296
Q

resistance to the flow of current in a conductor is governed by what?

A

the size of the conductor, length of the conductor, type of material, and the temperature

297
Q

formula for power factor

A

kW(true power)
_______________________________________
kVA(apparent,available power) X Pf(power factor)

298
Q

why must transformers that are being banked have almost the same impedance?

A

the transformer with the least impedance will carry most of the load

299
Q

what are Eddy currents?

A

low voltage, short circuited currents which are caused to flow in various areas of the core by the magnetic lines of force cutting across the core in varying intensities.

JL Exam (2 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions