Power Quality Test Review Flashcards
While IT devices can be made more efficient, business’s ever-growing reliance on IT still results in a net ? in the use of electrical power.
Increase
Kirchhoff’s Current Law, Kirchhoff’s Voltage law, Ohms law are the main laws/formulas used to solve PQ problems.
Not Thevenins
Harmonic currents are induced by loads that draw current in a(n) ? Waveform.
Distorted
Voltage Phasors, or Vectors are separated by ? degrees in a normal 3-phase power distribution system
120
A ? is a decrease from the nominal voltage supply level
Sag
A ? is an increase in the voltage level.
Swell
? are frequently the result of a sudden decrease in load current.
Swells
A ? is one who is familiar with the construction and operation of the equipment and the hazards involved.
Qualified Person
NIOSH identified five scenarios that describe the incidents resulting in 244 fatalities. Of the five scenarios, direct worker contact with energized equipment accounted for ? percent.
21
The use of proper personal protective equipment is intended to ? injury
Prevent and Reduce
? accounts for 24% of electrical activities being performed at the time of an accident that resulted in injuries.
Troubleshooting
According to NFPA 70B, “As a general rule, no electrical apparatus should be worked on while it is ?.
Energized
A 3% voltage imbalance between phases may result in the need to de-rate electric motors by ? percent?
10
Both Voltage unbalance and harmonics are generally considered as ? power quality problems
Steady-State
Permanently-installed power quality monitoring systems are typically ? and provide the advantage of showing trends.
Web-Based
The ? is one of the most popular tools for the PQ monitoring because it does not require contact with energized circuits
Infrared Imager
A power quality instrument should be rated for the ? range of voltage and current levels.
Anticipated
When accurate measurements are needed on sinusoidal waveforms to detect distortions, only ? meters should be used.
TRUE RMS
If PW measurements require potential transformers (PT’s) to step down voltages, make sure that the ? that the PT’s will pass through will not affect the reading.
bandwidth signals and frequency response
Make sure you have the right equipment for the right thing
Volt-amperes=reactives(VARS), should only be computed on the ? in a distorted or unbalanced system
fundamental frequency components
Sub-quarter-cycle changes in the waveshape that usually do not trigger abn RMS variation define ?.
Transients
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
What is the likely direction or source of the fault condition if the current increases significantly when the voltage decreases?
Downstream toward the load
When measuring equipment efficiency, monitoring should be conducted over the ?, because the efficiency varies as a function of load.
full range of loading
The potential difference in two improperly-made ground connections causes current to flow in a ground loop path, with possible noise and/or component failures.
TRUE
Telecommunications circuits are susceptible to harmonic currents being coupled or induced into the telecom siring.
TRUE
n order to prevent premature failure, a motor should be de-rated due to which findings?
Harmonic losses, Negative sequence values, Voltage unbalance levels
If electrical disturbances are recorded over an extended period and the monitoring equipment indicates they are on the utility side of the PCC, what should be done to remedy the disturbances
The Utility should be informed of the monitored events
Lightning is a ?.
high frequency transient
Improperly grounded communication cables between peripherals and the mainframe computer may become a problem when exposed to strong level RF signals though
EMF coupling, inductance, inductive coupling
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 protection
(WYSIWYG) is NOT one of the tested and verifiable “Rules of Thumb”
(What you see is what you get)
On a single-phase circuit, the origin of a voltage sag is usually ? significantly during the sag
downstream if the neutral-to-ground voltage increased
Sag is the sum of the ? in both the line (hot) and neutral (grounded) wires.
Voltage drops
What type power apply 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 offline.
A single-phase, rectified-input, switching power supply.
A load or circuit with significant loads with rectified inputs will most likely have a true power factor less than the displacement power factor.
TRUE
A common source of incorrect data comes from not using current probes within their ratings
TRUE
Negative transients add to energy from the voltage sine wave
FALSE
Learning which mitigation solutions will work for which power quality (PQ) phenomena can be studied from the phenomena side or the solution side.
TRUE
-Which of the following is NOT a classification for PQ phenomena?
Induction
