EETC Power Distribution 5

Question 1

What is the function of a 'keep-away' fuse used in power distribution?

Accepted Answer

A fuse designed to interrupt fault current without expelling gases toward adjacent conductors

Answer

Keep-away (or non-venting) fuses are designed to interrupt fault current while directing expulsion gases safely, preventing flashover to adjacent phases or equipment.

Question 2

When sizing a distribution transformer for a commercial load, which factor accounts for the non-simultaneous operation of all connected equipment?

Accepted Answer

Demand factor

Answer

Demand factor accounts for the fact that not all connected loads operate simultaneously, allowing the transformer to be sized smaller than the total connected load.

Question 3

Which grounding method connects the system neutral directly to earth without any impedance?

Accepted Answer

Solid (effective) grounding

Answer

Solid grounding, also called effective grounding, connects the neutral directly to earth, resulting in high ground fault currents that can be easily detected and interrupted.

Question 4

A distribution system operates at 12,470Y/7,200 V. What does '7,200 V' represent?

Accepted Answer

The voltage from phase conductor to neutral (phase-to-neutral voltage)

Answer

In the designation 12,470Y/7,200 V, 12,470 V is the phase-to-phase voltage and 7,200 V is the phase-to-neutral voltage (12,470 / √3 ≈ 7,200).

Question 5

What is the purpose of installing a line voltage regulator on a distribution feeder?

Accepted Answer

To maintain constant voltage at a set point as load and source voltage vary

Answer

A voltage regulator uses a tap-changing autotransformer to hold the output voltage within ±10% of set point regardless of load current and source voltage fluctuations.

(EETC) Electrical Technician Certification Practice Test

(EETC) Electrical Technician Certification Practice Test

EETC Power Distribution 5