ECS Electrical Supply Systems and Distribution 2

Question 1

What is the standard frequency of the electrical supply in the United States?

Accepted Answer

60 Hz

Answer

50 Hz

Answer

25 Hz

Answer

400 Hz

Question 2

In a three-phase 208V/120V Wye system, what voltage would you measure between any two line conductors?

Accepted Answer

208V

Answer

120V

Answer

240V

Answer

480V

Question 3

What is the purpose of a sub-distribution board (SDB) in a large commercial electrical installation?

Accepted Answer

To distribute power locally within a zone, fed from the main distribution board

Answer

To increase the supply voltage for high-power equipment

Answer

To convert three-phase power to single-phase for office equipment

Answer

To store power during off-peak periods for later use

Question 4

Which type of electrical supply system uses a separate protective earth (PE) conductor and a neutral (N) conductor throughout the installation?

Accepted Answer

TN-S system

Answer

TN-C system

Answer

TT system

Answer

IT system

Question 5

What is the primary advantage of a ring main circuit over a radial circuit for socket outlet distribution?

Accepted Answer

It provides two paths for current, allowing smaller cable sizes for the same total load

Answer

It can carry higher voltages

Answer

It eliminates the need for overcurrent protection devices

Answer

It automatically balances three-phase loads

Question 6

What does 'diversity' mean in the context of electrical load calculations for a distribution system?

Accepted Answer

The assumption that not all connected loads will operate simultaneously at full load

Answer

Using multiple different types of cable in one installation

Answer

Installing circuits in multiple separate distribution boards

Answer

Using a mix of single-phase and three-phase circuits

Question 7

What is the purpose of a busbar in an electrical distribution panel?

Accepted Answer

To provide a common connection point for multiple circuit conductors within the panel

Answer

To provide insulation between live conductors

Answer

To regulate the voltage output to connected circuits

Answer

To measure current drawn by individual circuits