Unit 3-5 Lesson 10
A circuit is said to have a ? when one or more conductors are in contact with the earth. a. ground b. known value c. low-resistance return d. universal return
A
If there is no apparent cause for a permanent line outage and the protective device trips out every time the line is reenergized, the cause may be a ? . a. faulty surge arrestor b. frequency problem c. substation overvoltage d. transit ground
A
In many cases, when power lines are down, the location is promptly reported by ? . a. a member of the public b. line fault locators c. line wave traps d. SCADA equipment at the substation
A
Testing for the presence of voltage on transmission and distribution lines is done with a potential tester; for circuits under ? , a voltmeter can be used. a. 750 V b. 1,000 V c. 1,200 V d. 1,500 V
A
A condition where two or more circuit conductors come in contact with each other is called a "cross" or ? . a. bi-fault b. isolator c. open circuit d. short circuit
D
Normally, an operator will close an oil circuit breaker to see if the fault persists or if it was a(n) ? fault. a. animal-caused b. instantaneous c. overvoltage d. transient
D
The most frequent cause of a transient fault is ? . a. a tree on the line b. an overload c. ice on the line d. lightning
D
Two methods of locating faults on overhead lines are patrolling and ? the line. a. "bumping" b. energizing c. overloading d. sectionalizing
D
Very few of the faults found on an underground system are ? . a. caused by dig-ins b. due to overloads c. permanent in nature d. transient in nature
D
A line can be grounded and continue to operate if it does not have a ? of its own. a. fused disconnect b. permanent ground c. sectionalizer d. substation circuit breaker
B
An accidental ground on two phases of a delta-connected feeder has the same effect as a(n) ? . a. open circuit b. short circuit c. transient fault d. voltage spike
B
If an outage occurs on a circuit, but the oil circuit breaker protecting the circuit has not operated, a Qualified Electrical Worker would suspect a(n) ? . a. faulty breaker b. open circuit c. phase-to-ground fault d. phase-to-phase fault
B
The three types of overhead line faults are short circuit, open circuit, and ? . a. arrester caused b. ground c. isolator d. transformer
B
When troubleshooting a no-power call from an individual customer, start with a voltmeter check at the ? . a. closest meter base to the substation b. customer's meter base c. customer's transformer d. first transformer off the main line feeder
B
A phase-to-ground fault is the cause of about ? of permanent faults. a. 25% b. 50% c. 70% d. 95%
C
A single-phase oil switch operation may indicate a short circuit or a(n) ? . a. contact time-travel failure b. open circuit c. overload d. relay voltage spike
C
During a low-voltage situation, a motor draws ? and the torque the motor produces is reduced. a. fewer amperes b. high voltage c. more amperes d. nominal amperes
C
If an outage occurs on a very hot or very cold day, suspect a(n) ? . a. faulty substation breaker b. galloping of the lines c. overload problem d. power harmonics problem
C
The effect of an accidental ground on one phase of a 3-phase, 4-wire wye-connected feeder is a(n) ? . a. current in-rush b. open circuit c. short circuit d. transient fault
C
If there is a high initial in-rush current when the switch is closed and the line trips out again, a hydraulic recloser handle can be held closed until the in-rush current drops. Select one: True False
False
One method of checking an underground system is to use a smaller fuse so the cable is not subjected to the full fault current generated by the fault. Select one: True False
False
The most common result of short circuits on overhead lines is that the conductors will fuse together. Select one: True False
False
A short circuit will cause heavy current to flow in the line. Select one: True False
True
If a circuit has been out for a while, especially during peak-load periods, a heavily loaded circuit may have to be picked up one section at a time. Select one: True False
True
If patrolling does not locate a fault on a line, disconnecting one tap at a time from the main feeder and noting whether the fault is cleared when the main line is reenergized may be the only option. Select one: True False
True
It is possible for a circuit to have more than one kind of fault at the same time. Select one: True False
True
The most common and most direct way to locate a fault on the line is to patrol the line. Select one: True False
True