CME CME Power Quality & Energy Efficiency

Question 1

What is the acceptable range of Total Harmonic Distortion (THD) for voltage at a point of common coupling per IEEE 519?

Accepted Answer

Less than 5%

Answer

IEEE 519 specifies that voltage THD at the point of common coupling should be less than 5% for systems below 69 kV.

Question 2

Which device is most effective for mitigating voltage sags caused by motor starting on a distribution system?

Accepted Answer

Static VAR compensator (SVC)

Answer

A static VAR compensator rapidly injects or absorbs reactive power to stabilize voltage during transient events like motor starting.

Question 3

A facility's power factor is measured at 0.72 lagging. What is the most efficient corrective action for a master electrician to recommend?

Accepted Answer

Install capacitor banks at the load

Answer

Capacitor banks supply leading reactive current that cancels the lagging reactive demand, improving power factor toward unity.

Question 4

Which harmonic order is typically the most problematic in three-phase systems powered by six-pulse VFDs?

Accepted Answer

5th and 7th

Answer

Six-pulse rectifier drives characteristically generate dominant 5th and 7th order harmonics that can overheat transformers and trip protective relays.

Question 5

What is the purpose of a K-factor rating on a transformer serving nonlinear loads?

Accepted Answer

Indicates the transformer's ability to handle harmonic heating without derating

Answer

A K-factor transformer is designed with additional thermal capacity to withstand the increased eddy current losses caused by harmonic currents.

(CME) Certified Master Electrician Practice Test

(CME) Certified Master Electrician Practice Test

CME CME Power Quality & Energy Efficiency