General Flashcards
(314 cards)
1
Q
Can Transformers with different kVA be parallel?
A
Yes, if the impedances are nearly the same in the load split proportionally
2
Q
Amapacity
A
 the current in amps that a conductor can carry continuously without exceeding its temperature rating
3
Q
Capacitance is measured in
A
Farads
4
Q
With out iron losses and copper losses a transformer would be
A
100% efficienct
5
Q
Inductance is measured in
A
Henerys:L
6
Q
Primary coils have..
A
More turns, smaller wire higher insulation
7
Q
Secondary coils have,
What turns and how much insulation
A
Lesser turns, larger wire, less insulation
8
Q
The amount of current to fully magnetize the iron core is sometimes known as..
A
Exciting current/charging current
9
Q
Formula for copper loss or heating loss
A
I^2xr
10
Q
Is there a 3rd harmonic voltage in a delta-delta bank?
A
No
11
Q
Eddy currents
A
When the magnetic field induces a voltage in to a transformer coil- a voltage is also induced in to the iron core-this induced voltage is eddy current, it causes heating and a waste of energy
12
Q
Copper loss
A
The losses in a transformer due to the resistance of the wires making up the turns of the primary windings
13
Q
What is the purpose of the laminate sheet insulating material coating the core steel sheets,
A
To reduce the core loss and the heating process in the core by insulating each sheet from one another
14
Q
Permeability
A
The ease which soft iron conducts magnetic lines of force; the softer the iron the greater the permeability
15
Q
Hysterises loss or excitation loss?
A
Also know as excitation loss energy consumed when the iron core is magnetized by ac power at 120times a second
16
Q
How is hysteresis loss reduced
A
The core is made of more permible iron easier to magnetize and demagnetize
17
Q
Wye system -tip to tip
A
Line voltage
18
Q
Recloser
A
Automatic switch used to open and then quickly reclose a power switch which has been opened by an over current on a distro line like phase to phase and phase to ground fault such as a tree branch going on and off line when it’s windy
19
Q
Regulator
A
A device used to control voltage of a circuit by raising and lowering voltage to maintain a constant level 16 up and 16 down 32 total
20
Q
Sectionalizer
A
Self contained circuit opening device that automatically opens the main electrical circuit after sensing and responding to a present number of successive main current impulses- doesn’t open under fault current only a fuse coordinated with a recloser
21
Q
Capacitors come in what sizes?
A
15,25,50,150,200 kva
22
Q
Red gloves class 0
A
1000 volts
23
Q
White gloves class 1?
A
7500 or less
24
Q
Yellow class 2
A
17,000 or less
25
Green class 3
26,500 or less
26
Orange class 4
36,000 or less
27
Rms voltage=?
Effective voltage
28
Peak value =
1.414xrms
29
Rms=?
.707xpeak
30
What are transformers used for metering installations called?
Instrument transformers
31
What are two basic analog ohm meters
Series and shunt
32
Gas treated poles can conduct as much as?
90% to ground
33
Do capacitors have voltage ratings?
Yes
34
What 3 physical dimensions determine like classification?
Length,circumference 6ft from the bottom and the top
35
Working load limit?
Breaking strength divided by safety factor
36
How are distribution and substations capacitors connected?
Distribution=parallel
Substation=series
37
What current are constant current transformers set at?
6.6 amps
38
The use of insulating equipment such as___ can protect line workers handling grounded equipment and conductors from hazardous touch potentials
Rubber gloves
39
Why is the wye-delta neutral floated??
To balance the load on secondary’s to prevent banking action
To protect the equipment if one phase blows
40
3 methods protect workers
Isolation,insulation,epz
41
3 main parts of a xmfr
Coils,core,can
42
What is a weak point between line and electrical apparatus
Fused cutout
43
A tendency of a circuit to store electrical when a potential difference
Capacitance in a circuit
44
Line without load can carry up too
20amps
45
Element that in apparent power that does not do any work
KVAR
46
Power of 1amp flowing under pressure of 1 volt
Watt
47
Ability to induce a magnetic field on a conductor. Measured in (henrys)
Inductance
48
2 basic analog ohm meters
Series and shunt
49
3 phase generator produces how many voltages and how far out they out of phase in degrees?
3 equals and 120 degrees apart
50
A magnetic field is created when
Current flows through a conductor
51
Determining conductor size
Line voltage/the amount of power to be transmitted/mechanical strength
52
What is a cable fault
When the insulation on the wire or cable can not sufficiently confine the voltage
53
What is a megger meter?
An ohm meter that measures high resistance
54
Most common defect in insulators are
Cracks in poreclian
55
What is a splice
Joining of two or more conductors
56
Name 3 devices that are used to protect lines
Surge arrestors - shield wire -protector tubes
57
What is phase sequence,
123) clockwise (321) counter clock wise
58
Ground to ground rule
Rubber gloves should be continually worn while working in any structure carrying energized conductors
59
Cradle to cradle
Rubber gloves should be worn from the time a bucket truck leaves the cradle position to the time it is returned
60
Extended reaching rule
Rubber gloves shall be worn anytime a worker and the length of any non insulated tool being used are able to come into contact an energized conductor *5ft rule*
61
Lock to lock
Rubber gloves shall be worn when a cabinet or vault with energized cable is opened and shall be worn continuously until closed and locked
62
Step potential
Defined as the voltage difference between two points on the ground separated by the distance of pace
63
Touch potential
The hands are at one potential while the feet on the ground are different potentials
64
Second point of contact
Where the current would leave a persons body if contact were made with a hot circuit
65
Transmission line failure
Insulator flash over
66
3 phase line balanced if the amps of the netural =
5 o
67
Vector=
Line having definite length and direction
68
Porcelain insulators can stand more
Compression
69
3 causes of accidents
Human elements
Acts of nature
Mechanical failure
70
Max oxygen level
Normal
Minimum
23.5
20.8
19.5
71
Hepatitis b
Is the greatest risk of blood borne pathogen
72
Recloser holds line for
60 cycles a second
73
One circular mill is
.001 of an inch
74
Raise the tap
Lower the secondary voltage
75
Lower the tap
Raise the secondary voltage
76
How does a tap changer work
Adding or subtracting a part of the primary coil, there for changing the ratio
77
Safety factor of new rope
5:1
78
Old rope
10:1
79
3 things to look for in a injured person
Response,bleeding,pulse
80
Voltage regulator
Electrical apparatus used to regulate voltage at 10% above or 10%below and at 32 step total, primary side is connected in parallel and secondary side is in series
81
Counter posie
It is a grounding grid for a substation or a footer on a transmission line
82
When fuzzing insulators go by the
Intensity of the sound
83
Where us Fault current greater at??
Is greater near the sub
84
Dampener is used for??
To reduce vibrations and prevent conductor from damaging
85
EMF
Force that makes electricity flow
86
Will Adding parrelled loads to a circuit will decrease total circuit resistance?
Increase total circuit current
87
Analog meter works
Magnetic principle that like poles repel each other
88
240/120
Means that the secondary coil permanently in series
89
Paralleling an additive xmfr and a sub xmfr
Grounding cans install both neutrals heat up one side of the xmfr and install secondary’s heat up the other side of the xmfr and then phase in with a volt meter
90
Can you ground a transformer in a delta power bank connection on the secondary side
Yes only one can
91
One horse power
746 watts
92
What is the purpose of transposing
To reduce interference
93
KVAR
Kilo volt amp reactive
94
Affect of electrical current through the body
Path it takes
Amount of current flow
Time that the body holds on
95
Primary booster is a
Conventional xmfr connected as a auto xmfr
96
Advantage of overhead
Lower cost to build
Easier and quicker detection for repair
Lower cost to upgrade
97
Advantage of underground
Almost no exposure to storms
Keeps the Public safer
Long runs go under a river
98
Fuse coordination
It’s all the houses loaded on one at the same time
99
OCR Recloser has
4 operations
100
Fuse link t is what
It’s slower
101
Fuse link k
Is the fast
102
There is how many indicators on a maximeter
2
103
3 types of wire tongs
Pole type, cross arm and tower
104
To balance large capacitive loads caused by parrellel conductors of a transmission line,? Are installed in a subs these reactors produce? That? At the? In the transmission line
Shunt reactors
Inductive reactance
Cancels
Capacitive reactance
105
Only moving part in a transformer is the? In the steel core
Oscillating material
106
Two different types of arestors
Explosive,valve type
107
Standard taps on a transformer
(4)2.5% and (2)+ or - 2.5%
108
Determines the amount of voltage drop with a transformer when fully loaded?
Impedance’s
109
Underground conductor shapes
Concentric round,round,compact round,annular sector,compact sector
110
Proper grounding
Low resistance path to earth
Clean connections
Tight connections
Connections made at proper points
Adequate current carrying capacity
111
Customer request 480 volts 3phase,3 wire what xmfr can be used
Rated at 277 and 240/480
112
Customer requests 277/480 3phase,4 wire?
On 277/480 can be used
113
If a customer requests 120/208 volts
120/240 can be used
114
On a wye-delta connection where will there be a third harmonic voltage measured
Where the neutral floats
115
In a wye-wye 120/208 bank if the primary neutral is disconnected from the system neutral what condition will exist?
A third harmonic voltage exists between the primary neutral and the system neutral and ground this excessive voltage could be dangerous to anyone working in the pole
116
Two angular displacements for a wye-wye or delta-delta
0-180
117
Two angular displacements for wye-delta or delta wye
30-210
118
Polarity of a transformer
The direction of current flow between the primary and secondary coils
119
Phase separation generated ether wye or delta is
120 degrees
120
A transformer with subtracting polarity is what voltage and kva
8660,200 kva
121
By changing the ratio of the turns in the winding, you change?
Voltage
122
Wye-delta bank primary nuetral floated?
Yes it’s to protect the equipment if one phase blows on a fuse
123
Why is a 4th cut out installed on a wye delta bank
Faro reseidencs
124
What must be done before climbing above a de-energized transformer
Disconnect the secondaries
125
6 different types of transformer hook ups
Open-wye delta
Open-delta-delta
Closed wye-wye
Closed wye-delta
Closed delta-delta
Closed delta-wye
126
What are taps for??
To correct primary voltage
And secondary voltage
127
Reactive power?
The element in the apparent power formula that does not do any work
128
Means of egress such as a stairways,ladder,ramp must be located in a trench excavations that are _ so as to require no more than_ of a lateral Travel with in the trench
4 foot or deeper
25 feet or longer
129
What should always be done before opening a series street light circuit?
-drop all the load
-take out constant current carrying transformer out of service
130
Which rope is considered to be an insulator
Clean and dry polypropylene rope
131
Pole strength is determined by
Strength to resist loads applied 2ft from the top of the pole
132
What is used to prevent a series street light from being completely interrupted by a burnt out lamp
Film disk cutout
133
Active power is also referred to as
Effective power-true power-real power
134
When using the open wye/open delta connection or open delta/open delta in a emergency situation when one transformer in a closed wye delta or a closed delta delta bank fails the kva rating of the bank is reduced by what factor
86.6% of the remaing two
Or 57.7% of the original 3
135
3 factors when sagging wire
Temp,span length, size of conductor
136
Where in the tap changer motor
In the oil
137
When were PCB oil banned
1979
138
What are two types of capacitors
Switched and fixed
139
How do you determine the mechanical advantage of a block and tackle
Count the number of lines in the moving block
140
Gaffs should be sharpened to a what point
Chisel
141
Fall arrest must be worn at
4 and above pole ground level
142
Main advantage of a wye secondary vs a delta secondary
Efficiency- because of balanced loads
143
What kills the under ground transformer primary coil
Bayonet fuse
144
3 types of faults
Open circuit, shorts circuit, ground fault
145
4 bushing secondary (parallel)
4-2 3-1
146
Rubber gloves test?
Sleeves?
Hot sticks?
6months
1 year
2years
147
What are constant current transformers used for?
For series street lights- where current must be kept constant
148
3types of substations
Transmission, sub transmission, distribution
149
Electrical fires are what fires?
Class c
150
What cell can’t be recharged??
Primary cell
151
3 types of air switches?
Circuit breaker,air break,disconnect
152
Describe a Capacitor??
1or2 high voltage bushings, with no secondary bushings, has no moving parts, two inner plates separated by an insulated medium
153
What are the most common kva for capacitors??
100,150,200kva
154
When connecting a wye-wye closed bank connect the neutrals together (primary)-(secondary), why do you do this??
To prevent fluctuation voltage on the secondary side
155
Current limiting properties of an inductor
Inductive reactance
156
Rubber glove cuffs are rated at what?
10,000 volts per square inch to protect from flash overs
157
Wye can carry ___ than a delta and provides for a more balanced load
73%
158
What meter is used when paralleling cans
Voltmeter
159
4 Conditions met when paralleling cans?
-voltage ratings are identical
-tap settings are identical
-frequency ratings are identical
-precents on the impedances of one is between 92 1/2- 101 1/2
160
Primary metering installation has a current xmfr with a 30:5 rotation and a potential xmfr with a 7200:120 rotation: to find kwtt consumed you must multiply the meter dial reading by 360?
7200. 30.
———=60 ——- =6 60x6=360
120. 5
161
Auto transformer has how many coils
One coil
162
Closed bank load share
Single phase
Three phase
Three phase is 1/3-1/3-1/3
Single phase is 1/3-2/3-1/3
163
Open bank load share
3 phase load x 57.7% = load on each power pot
Single phase load is shared equally 100%
164
What is the efficiency of a open bank
86.6% effective
165
When personal protective grounds are installed it is to ensure that everything a person is touching in the pole will likely be at the same potential
Equalpotential bonding (epz)
166
This does not protect the worker from accidental re-energization it protects the worker from back feed/induction
Bracket grounding
167
Controls current/voltage in a circuit
Protective grounds
168
One of the three main components of an atom- has a negative charge
Electron
169
Has a positive charge in the atom
Proton
170
No electrical charge….. in the neutral
Neutron
171
Primary//secondary coils are connected magnetic and electrically
Auto transformer
172
Fusing transformer ex. 25kva 7200 primary.
What’s the math
25000/7200=3.47x design factor
173
Does the load on a capacitor ever change??
No always draws the same amount current
174
Bucket trucks operate on what type of hydraulic system??
Open/closed
175
Work from a plat form attached to a pole and any elevation greater than 6ft from surrounding elevations requires the use of
Appropriate fall protection at all times
176
When was the Ibew organized??
1891 by Henry Miller
177
Ibew international convention meets??
Every 5yrs
178
#2 copper Mac amp rating
200amps
179
1/0 copper Mac rating
260
180
2/0 copper Mac rating?
300amps
181
3/0 copper Mac rating
350 amps
182
4/0 copper Mac rating
400amps
183
Mad distance up to 15kv
2’-1” phase to ground
2’-2” phase to phase
184
Can a csp transformer be used on a open delta/delta connection
Only if the future plans do not call for closing the bank
185
What does a ground consist of??
An artificial electrical connect to earth having a very low resistance to the flow of electrical current
186
The primary booster is a conventional transformer connected??
As an auto transformer- it is not grounded and has no fuse protection
187
Highest tap
1-i-A
188
Lowest tap
5-v-E
189
In a parallel operation with transformer which one will pack the greater impedance the with less or more
The lesser impedance
190
Properly paralleled two transformer
What are the name plate nessites
Same voltage ratios
Nearly same impedance with in 10%
Connected to the phase
The polarity on the cans must be the same (additive or subtractive)
191
The voltage is stepped down with the primary has___more than the secondary
More
192
If the secondary has___ the number of turns as the primary the secondary voltage will be twice as high
Twice
193
Turns ratio in a xmfr can
Step up
Step down
30:1 step up
1:10 step down
194
A transformer with only 1 primary bushing must be always?
Case grounded
195
A single bushing can may not be used on what?? Wye or delta??
Delta system
196
A transformer with a name plate of 240/120 has how many coils one or two??
One
197
How many cut outs are needed for a open delta delta
3 cut outs 3-la
198
277/480 has how many secondary bushings
2
199
Is system voltage and line voltage the same??
Yes
200
System voltage is ___ larger than phase voltage
1.73
201
Line voltage = what in a delta system
Phase voltage
202
Two basic functions of oil in a transformer
To cool and insulate
203
Underground transformers are fed through a??
Buss bar
204
Which coil is the tap changer located in a distribution transformer??
Primary coil
205
What is hazardous of a broken series street light in a circuit??
The constant current transformer could be a max voltage out put
206
What do rectifiers do??
Change ac to dc
207
Transformer voltage ratios and transformer turns ratios are what??
Directly proportional
208
What is a red and blue glad hand used for??
Red-emergency
Blue-service lines
209
What are two test methods to check if a line is dead??
High voltage meter
A tracer
210
What is the definition of power??
The rate at which work is done
211
What is the strongest rope??
Nylon rope
212
Power factor=??
Active power/apparent power
213
2 advantages for a 4 wire feeder vs a 3 wire feeder??
Cheaper to build and more efficient
214
Impedance is the total opposition of current flow in an a/c circuit, what is symbol letter what is it measured in?? And is made up of??
Z- ohms
Resistance
Inductive reactance
Capacitive reactance
215
Circuit breaker are named due to their?? And the gases to snuff at arc
Quenching medium: oil, air,vacuum and esle gas
216
What is a resistor in a conductor?? Like what happens when it’s a long span??
Diameter
Length
Temp
217
“ELI”
Voltage leads current
Inductive reactance
218
“ICE”
Voltage lags current with capacitive reactance with opposing current flow
219
In a AC circuit with reactance voltage can lead or lag as much as what??
90 degrees
220
What is a maximeter
Clamp on ammeter having two indicators pointers, one indicator shows the current at the time of the reading and the other indicates the maximum current sense installation
221
Max tie down for trailers is??
10 ft apart
222
An ammeter is connected__with circuit and the other is clamped on in___
Series and parallel
223
Two types of counter posie grounding
Continuous=parallel
Crows foot=radical
224
Carbon in the oil of a transformer is an indicator of??
Arching
225
Typical rule for capacitors placement
2/3 of the distance where the voltage has dropped 2/3
226
OSHA states that 5feet or more there is 4 choices of methods to be safer
Benching,sloping, shoring, shielding
227
What are substation disconnects used for?
Isolate equipment, bypass equipment, transfer loads and and as a ground device
228
Volts=
Amount of potential that will cause 1 coulomb to do 1 joule of the work
229
Two types of transformer construction?
Core shell
Shell is the most common
230
Test dates in rubber blankets
12months
231
Define average value of ac voltage
It is obtained by calculating the average of all instantaneous values in half a cycle
232
Apparent power
The total power supplied by a circuit, apparent power is a combination of active power and reactive power
233
3 types of pole tops?
Slant, gable,flat
234
Watt meter is connected___ with a circuit
Series
235
Ground rods should be long enough to reach the ____ moisture in the soil
Permanent
236
33,000 foot pounds per minute is equal to??
One horse power
237
A delta circuit uses vectors from??
Head to tails
238
Open wye-open delta primary neutrals needs to be what??
Tied down to the system Nuteral
239
Transformer check list
Primary voltage
Kva rating
Secondary voltage
Impedance
240
Rotation meter??
To see what way your phase is, A B C OR C B A
241
What purpose does the case ground serve on a transformer??
To ground the case or XMFR and it acts as a neutral on a single bushing can
242
Phase and rotation rule
Phasing insures rotation..rotation does not insure phasing
243
What is an unexplained voltage condition exists in a wye wye and a wye delta transformer connection
Third harmonics 180 hertz an unwanted voltage on a system
244
How much larger can the third harmonic voltage be than the phase voltage??
150%
245
Magnetic reluctance
Resistance to the formation of flux in a magnetic circuit
246
Can an open delta and a closed delta bank be paralleled??
Yes when properly phased
247
In a wye system tip to center=
Phase voltage or coil voltage
248
Transformer iron losses are caused by?
Eddy currents and hysteris losses
249
Wye-delta banks and delta wye banks but be with in what angular displacements??
30-210
250
Auto transformer
Has one Coil primary/secondary coils are calculated magnetic and electric
251
Corna on a conductor
Occurs around a conductor when the conductor potential is rasied above the dielectric street of the surrounding air
252
Low power factor can be reduced by??
Using a capacitor
253
Lagging current?
Inductive reactance
254
Leading current??
Capacitive reactance
255
A transformer is connected to a line and how it works?
It’s a magnetic coupled device that runs off the mutal induction
256
A power transformer is what kva a larger?
200kva
257
The use of a current transformer on an oil circuit break??
Metering purposes
Over current signals to the relay
258
Capacitor how to take off line
De-energized
Visual open
Wait 5 min
Test
Ground
259
A sectionanalizer
Doesn’t operate under fault current
Opens between 3-4th operation
Fuse coordinated with relcoser
260
The polarity mark of a instrument transformer is normally connected to what side?
The load side
261
Some switch gears can be over current protected devices and other examples could be??
Circuit breakers, Recloser,or fused cut outs or sectonializers
262
Air arrestors??
Air gap in series with resistors
263
The transformer with the lower impedance will have what??
The greater load
264
What is the white bushing on a instrument transformer?
The polarity mark
265
Aluminum bolts need what??
Need to be lubed and can’t be retorqued
266
Two main losses in a transformer core and coil, or iron and copper loss.
Iron-eddy currents and hysteresis losses
Copper-heating losses of a conductor ir2 loss
267
Is there an electrical connection between primary coil and secondary coil
No when voltage is applied to the primary coil, it induces a magnetic field in the core and induces a voltage on the secondary coil.
268
Can a csp transformer be used on a open delta/delta connection
Yes only if there is no plan on the closing the bank
269
A closed delta bank converted to an open delta bank
100%-57.7%=42.3
270
Paralleling a single phase xmfr conditions must be met
Voltage ratings are identical
Tap settings are identical
Frequency ratings are identical
The taps are with in 92-1/2%-107-1/2%
271
Auto transformer one coil?
S-L-sL
272
A compensator transformer?
Is a tapped auto transformer that is used to soft start large induction motors, soft starting large motor will prevent a voltage flicker for other customers on the circuit
273
One three phase transformer can feed about ___ times the typical length of a typical single phase transformer
8 times
274
A small <5kw generator can back feed on a primary line, the impedance is high enough to where if you have grounds on it will not short out the generator but it will still have primary current on it, if you open the wire it must me what??
Jumped out by a mac
275
Any wye delta bank of delta delta bank may blow one to two cut out and can have what feed on the line
Back feed
276
A transformer with a 240v secondary has 60 to 1 turn’s ratio what is the primary voltage feeding this transformer??
14,440
240x60=14,400
277
To conduct a turns ratio test on a transformer, why is it necessary to energize the high voltage coil with low voltage such as 120
Because transformers are reversible, if you were to put 120 on the secondary side you would get high voltage on the primary bushing which could cause death
278
Two kinds of tests can be carried out on a transformer using a 1000v merger?? What can they check for?
Damaged insulation and coil continuity tests
279
Can a single bushing transformer be installed on a delta circuit
Yes
280
A transformer coil must have a potential difference across it to operate. What two types of connections are possible to get a voltage across a transformer coil
Wye or delta
281
What would be the expected full load current 100% loaded on the 240v secondary of a 100 kva 7200/240 v transformer?
100000/240=416.6
282
When a secondary bus is fed from many transformers connected in parallel what kind of secondary system is it?
Main network
283
When two or more transformers are connected with the positive terminal of one transformer and connected to a negative terminal of another transformers what kinda if connection is it??
Delta
284
When two or more transformers are connected to a positive terminal of each transformer, and all the negative terminals are connected to one what kind of connection is it??
Wye
285
Why should the primary netural of a wye-delta transformer bank be left floating??
Because it would carry extra current that is not related to the current needed to supply the normal service load
286
Can the wye of a secondary of a wye-wye bank be connected to the same bus as the wye secondary of a delta wye bank of the same secondary voltage
Yes
287
A center tapped 120/240 secondary coil has the two parts of the coil inside the tank are arranged in parallel. What voltage would be between the x1-x3 terminals 120/208
288
Name three types of three phase services that three single phase units with a 120/-240 v can serve
Wye-wye wye-delta delta-delta
289
The lights in part of the customer’s premises are very bright and the in another part the light are very dim. What is a likely cause??
Poor netural connection
290
At the main panel the phase to phase voltage reading of a delta 240v service are lower than normal, and one phase to phase voltage reading is 0v for example the reading are 210-210-0 what is likely the cause??
One of the primary fuses on the primary cans of open and it’s only running at 57.7%
291
What advantages are there for a three phase versus a single phase circuit??
Runs a smoother with interconnected phases
292
What does it mean when the voltages of each of the three phase circuit are 120 degrees apart?
It shows the value of the current and one phase is always 1/3 distinct cycle behind
293
What can be done at a three phase three phase transformer bank if a customers three phase motor is running backward??
Switch one of the hot legs around
Not the wild leg if it’s 120/240 can
294
What is the voltage to ground on a 4160 volt delta circuit?
2400
2400x1.70=4160
295
What condition would put a very high current on the neutral and also raise the voltage between the neutral and ground??
SWER
Single wire to earth connection
It’s the system neutral for a single phase or an old DC circuit
296
Name two advantages for converting a delta circuit to a wye circuit
Single phase transformer requires one cut out, a multi ground netural, it always works because in poor ground conditions
297
Installing protective grounds on a circuit from accidental re-energization what are the 3 things to protect from??
1-from accidental re-energization,which can come from operator error,contact with neighboring circuits,
2-lightning
3-backfeed
298
Two kinds of induction coming from a circuit how does ground protection protect them and what are the two kinds of induction
1-electrostatic induction will induce a voltage on an isolated circuit
2-electromagnetic induction will Induce a current flow in the conductor and grounds of an isolated and grounded circuit
299
When using protective grounds,does the application of the grounding principle control the current or voltage??
Will control the current around the worker and adhere to the binding principle which will limit the voltage exposure to a worker
300
Grounding principle?
Protective grounds are installed to reduce any current flow through a working to an acceptable level by providing a low-resistance parallel shunt around the worker
301
Bonding principle??
Bonds must be installed so that a worker is kept in an equipotential zone
302
Does all the current in a grounded conductor take the easiest path to earth??
Bay far, most of the current will go through the low-resistances to ground
303
How does a lineman determine the correct grounds for the certain location of grounding??
Must meet the ASTM f855 standard specifications for grounding chart
304
Why is it important to test a grounding set?
Low resistance connection between the protective ground clamp and the conductor
305
What is the best ground electrode on a wye circuit??
The netural it’s the fastest trip out
306
How does bonding a grounding set to a structure provide an equipotential zone for a lineman?
Same potential as the phase being worked on
307
When removing grounds which set of grounds is more likely to create an arc? First or second set
The second
308
At what locations is an underground cable exposed enough to be able to apply grounds
Anywhere that a transformer or a switch head cabinet or a j-box is near
309
Why should doing a hot job should not be the option
Because of the risk of it
310
Why is a second point of contact considered a hazard when working hot??
Where current would leave a persons body
311
What length of clear insulating section of a live line tool would be maintained when working 115kv
3’-2”
312
An insulated jumper should carry out___ percent of the load current before cutting
1/3
313
Why is there higher risk when working on a energized secondary next to a transformer rather than a span away??
Because of the fault current that a step down transformer can carry
314
What two methods are used to inspect on insulated jumper??
Peel back and continuity test
