問題一覧
1
Sag is the sum of the ? in both the line (hot) and neautral (grounded) wires
voltage drops
2
The PQ phenomena classification that encompasses harmonics, inter harmonics, voltage fluctuations, notching, and DC offsets is wave form ?
distortion
3
What is a likely source of data that seems to contradict logic and/or physical properties?
the connection of power-monitoring equipment has not been performed correctly
4
Well grounded, properly-sized UL listed ? should be installed on any metallic interface that extends outside a structure, including the incoming electric service, phone lines, and any exterior branch circuits
surge protector
5
DC offsets more than a percent or two of the ? Voltage can have adverse effects on transformers
nominal
6
It is usually wise to have the ? Tool doing the monitoring until the source of the problem can be narrowed down
most versatile
7
Learning which mitigation solutions will work for which power quality (PQ) phenomena can be studied from the phenomena side or the solution side
true
8
Harmonic currents are induced by loads that draw current in a(n) ? Wave form
Distorted
9
A common source of incorrect data comes from not using current probes withing their ratings
true
10
Portable PQ monitors can provide graphical displays of wave forms and trending information for ? Parameters
hundreds of
11
While IT devices can be made more efficient, business’s ever-growing reliance on IT still results in a net decrease in the use of electrical power
False
12
When measuring equipment efficiency, monitoring should be conducted over the ? Because the efficiency varies as a function of load
full range of loading
13
Which of the following are likely reasons that an electrical worker may work unsafely
cost and pressure by the customer and builder to work live, failure to asses the risk and/or recognize the consequences, inability to isolate because the boards or circuits are not labeled properly , laziness with safety ( taking shortcuts), unrealistic time schedules, which lead to pressure
14
On a single phase circuit, the origin of a voltage sag is usually ? significantly during the sag
downstream of the neutral-to-ground voltage increased
15
Which of the following are among the top responses from electrical workers when asked what kinds of unsafe things electrical workers do?
fail to implement and follow safe work practices, take short cuts, take the attitude of “production first” rather than “safety first”, work long hours and become tired and fatigued, work on live circuits when they do not need to
16
The use of proper personal protective equipment is intended to ? Injury.
prevent , reduce
17
A(n) ? Is one who is familiar with the construction and operation of the equipment and the hazards involved
qualified person
18
When accurate measurements are needed on sinusodial waveforms to detect distortions only ? Should be used
True RMS meter
19
A power quality PQ instrument should be rated for the ? Range of voltage and current levels
anticipated
20
RMS(effective) voltage variations due to PQ phenomena are often referred to as ?
interruptions , sags, swells
21
A(n) ? Is a decrease from the nominal voltage supply level.
sag
22
What is the likely direction or source of the fault condition if the current increases significantly when the voltage decreases?
downstream towards the load
23
Improperly grounded communication cables between peripherals and the main frame computer may become a problem when exposed to strong level RF signals through ? .
any of the above
24
Data collection and analysis will vary depending upon whether one is conducting a(n) ? Exercise
audit, troubleshooting
25
The combination of a computer and a copier on the same circuit could in and of itself be a problem, even if each were performing correctly, what is a possible solution to potential interference m?
A UPS could be installed to enable the computer to “ride through” the event
26
If the cumulative probability (CP) value obtained from an analysis study continues to increase. , what results can be expected?
mis-operating equipment , overheating motors, overheating transformers
27
Although ? Faults do not have enough current flow for the fuse or the distribution breaker to operate, they can result in the lights blinking
high impedance
28
Which of the following electrical theory law is NOT used to trace the source of most PQ-related problems?
Thevenin’s theorem
29
The ? Is one of the most popular tools for PQ monitoring because it does not require contact with energized circuits
infrared imager
30
Many tools designed to improve a power supply’s quality are not only among the first to suffer from a lack of quality, but are sometime ? To the problems they are intended to resolve.
contributors
31
A 3% voltage imbalance between phases may result in the need to derate electric motors by ?
10%
32
What type of power supply will have a sharp reduction in current at the beginning of a sag, followed by an increase in current to a value greater than the original current level, until the sag has ended or the equipment trips off line?
a single phase, rectified-input, switching power supply
33
A(n) ? is an increase in the voltage level
swell
34
To what can the underlying cause of most power quality problems be traced?
A few simple rules of electrical circuits
35
Which of the following is NOT a classification for PQ phenomena
inductance
36
? Accounts for 24% of electrical activities being performed at the time of an accident that resulted in injuries
troubleshooting
37
The ability to set a monitoring device to ? Automatically when a power quality event occurs allows one to analyze the courses of the problem
trigger
38
What step(s) may be needed to ensure that the (PQ) instrument does not have any significant impact on the measurements themselves?
employ current transformers CT, Employ high impedance voltage connections
39
Permanently-installed power quality monitoring systems are typically ? And provide the advantage of showing trends
web-based
40
If harmonic distortion was noticeably larger on a single phase when compared to all phases, what would an intuitive be for the increase in total harmonic distortion (THD)
single phase, non linear loads associated with most information technology and consumer electronics
41
Both the voltage imbalance and harmonics are generally considered as ? Power quality problems
steady state
42
Companies invest in additional back-up equipment that adds to the demand on the power supply and is sensitive to ? In the system
Fluctuations
43
When trouble shooting a (PQ) problem, one discovers that the neutral-to-ground voltage is >1% of nominal V at the distribution panel. What is the possible cause of the problems?
loss of the neutral conductor, excessive ground current caused by high impedance connection
44
Monitoring to establish a benchmark should be conducted for at least ? To get a more complete picture of the electrical supply
one week
45
Recent surveys have shown that sags are the most likely type of power quality disturbanc
true