EETC Power Distribution 3

Question 1

What is the standard color code for the high-voltage 'B' phase conductor in a North American overhead distribution system?

Accepted Answer

Blue

Answer

In the standard A-B-C phase color convention, A=black, B=red, and C=blue for medium-voltage overhead distribution, though utility practices may vary.

Question 2

Which protection scheme is most appropriate for detecting a single-line-to-ground fault on an ungrounded distribution system?

Accepted Answer

Zero-sequence voltage (59N) or ground fault detectors

Answer

On an ungrounded system, fault current is very small and does not flow back through neutral, so zero-sequence voltage detection or capacitively coupled ground fault detectors are used.

Question 3

The 'demand factor' of an electrical installation is defined as:

Accepted Answer

The ratio of the maximum demand to the total connected load

Answer

Demand factor equals maximum demand divided by total connected load, indicating that not all connected loads operate simultaneously at full rated capacity.

Question 4

Which NEC article primarily governs the installation of service-entrance conductors for a residential customer?

Accepted Answer

Article 230

Answer

NEC Article 230 covers services, including service conductors, service entrance equipment, and service disconnects.

Question 5

A power distribution transformer is rated 500 kVA, 13,200/480V. What is the rated full-load secondary current?

Accepted Answer

601 A

Answer

Full-load secondary current = kVA × 1000 / (√3 × V) = 500,000 / (1.732 × 480) ≈ 601 A.

(EETC) Electrical Technician Certification Practice Test

(EETC) Electrical Technician Certification Practice Test

EETC Power Distribution 3