NABCEP Electrical & Mechanical Concepts 4

Question 1

What is the purpose of anti-islanding protection in a grid-tied PV inverter?

Accepted Answer

Shut down the inverter if the grid de-energizes

Answer

Anti-islanding protection disconnects the inverter from an energized output if the utility grid fails, protecting line workers.

Question 2

What is the formula for calculating voltage drop across a conductor?

Accepted Answer

Vd = I × R

Answer

Voltage drop equals current (I) multiplied by the conductor resistance (R) per Ohm's Law.

Question 3

Which wire gauge has a larger cross-sectional area: 10 AWG or 6 AWG?

Accepted Answer

6 AWG

Answer

In the AWG system, lower numbers indicate larger wire diameters and greater cross-sectional area.

Question 4

What happens to PV module Voc as cell temperature increases?

Accepted Answer

Voc decreases

Answer

Voc has a negative temperature coefficient, so it decreases as module temperature rises.

Question 5

A residential PV system uses USE-2 cable on the roof. What does USE-2 indicate?

Accepted Answer

Underground Service Entrance, dual-rated for sunlight resistance

Answer

USE-2 is a dual-rated cable suitable for underground service entrances and also rated for direct sunlight exposure, common in PV source circuits.

(NABCEP) North American Board of Certified Energy Practitioners Solar Practice Test