CME Power Quality & Energy Efficiency Flashcards
6 cards from real CME practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 CME Power Quality & Energy Efficiency flashcards as text
What is the acceptable range of Total Harmonic Distortion (THD) for voltage at a point of common coupling per IEEE 519?
Answer: Less than 5%
IEEE 519 specifies that voltage THD at the point of common coupling should be less than 5% for systems below 69 kV.
Which device is most effective for mitigating voltage sags caused by motor starting on a distribution system?
Answer: Static VAR compensator (SVC)
A static VAR compensator rapidly injects or absorbs reactive power to stabilize voltage during transient events like motor starting.
A facility's power factor is measured at 0.72 lagging. What is the most efficient corrective action for a master electrician to recommend?
Answer: Install capacitor banks at the load
Capacitor banks supply leading reactive current that cancels the lagging reactive demand, improving power factor toward unity.
Which harmonic order is typically the most problematic in three-phase systems powered by six-pulse VFDs?
Answer: 5th and 7th
Six-pulse rectifier drives characteristically generate dominant 5th and 7th order harmonics that can overheat transformers and trip protective relays.
What is the purpose of a K-factor rating on a transformer serving nonlinear loads?
Answer: Indicates the transformer's ability to handle harmonic heating without derating
A K-factor transformer is designed with additional thermal capacity to withstand the increased eddy current losses caused by harmonic currents.
Under ASHRAE 90.1, which lighting control strategy is REQUIRED for commercial spaces greater than 5,000 sq ft?
Answer: Automatic shutoff controls
ASHRAE 90.1 mandates automatic shutoff controls (occupancy sensors or time scheduling) for commercial spaces exceeding 5,000 sq ft to reduce energy waste.