CME Power Quality & Energy Efficiency Flashcards

What does a displacement power factor of 0.95 lagging indicate about a facility's electrical load?

Answer: The load is predominantly inductive, drawing reactive power from the utility

A lagging displacement power factor indicates inductive loads (motors, transformers) consuming reactive power, which increases apparent power demand.

Which energy measurement metric represents the actual work-producing power consumed by a load?

Answer: Real power (kW)

Real power (kilowatts) is the component of electrical power that performs actual work, such as driving motors or producing light and heat.

A building energy audit identifies that replacing T12 fluorescent fixtures with LED equivalents will reduce lighting load by 40%. What additional NEC requirement applies to the new LED drivers?

Answer: LED drivers must be listed for the specific luminaire per NEC 410.6

NEC 410.6 requires that luminaires, lampholders, and associated drivers be listed for their intended use to ensure safety and compatibility.

What is the primary cause of neutral conductor overheating in a three-phase wye system serving computer loads?

Answer: Third-order (triplen) harmonic currents add in the neutral rather than cancel

Triplen harmonics (3rd, 9th, 15th) are zero-sequence and are additive in the neutral conductor instead of canceling as fundamental currents do.

Which power quality phenomenon is best described as a momentary increase in RMS voltage between 110% and 180% of nominal lasting 0.5 cycles to 1 minute?

Answer: Voltage swell

IEEE 1159 defines a voltage swell as an RMS increase to 110%–180% of nominal lasting 0.5 cycles to 1 minute, often caused by sudden load removal.

Per NEC 210.19(A)(1), branch circuit conductors serving continuous loads must be sized to what percentage of the continuous load current?

Answer: 125%

NEC 210.19(A)(1) requires branch circuit conductors to have an ampacity not less than 125% of the continuous load to prevent thermal degradation.