Definitions

Question 1

Define a continuity test

Answer 1

A continuity test checks that there are no breaks in the circuit, and that they have a low enough resistance to function safely and correctly

Question 2

Define an insultation resistance test

Answer 2

An insultation resistance test ensures that the insulating properties of the circuit(s) wiring and its accessories is sufficient to prevent current ‘leaking’ from the conductors.

Question 3

Define a polarity test

Answer 3

A polarity test is used to verify that all the conductors in a circuit are in their correct terminals, and that protective and swtiching devices are on the line conductor only

Question 4

Define a voltage test

Answer 4

A voltage test is used to determine whether or not a circuit is energized (live) or de-energized (dead).

Question 5

When performing a voltage test, what is being measured?
Which terminals should be used to get this measurement?
Which pair of terminals will not provide a reading?

Answer 5

A voltage test gives an indication of the potential difference of an energized circuit.
Between the Live & Neutral terminals and Live and Earth terminals will give a reading of this potential difference.
Neutral and Earth will not give a difference reading as they are at the same potential.

Question 6

Which documents provide more information regarding inspection & testing?

Answer 6

Part 6 of BS7671& Guidance Note 3

Question 7

Which document provides information regarding testing equipment?

Answer 7

Guidance Note GS38

Question 8

What is R1?

Answer 8

R1 is the value of the resistance of the Line Conductor in any given circuit.

Question 9

What is R2?

Answer 9

R2 is the value of the resistance of the CPC in any given circuit.

Question 10

What is Rn?

Answer 10

Rn is the value of the resistance of the Neutral conductor in any given circuit.

Question 11

When does initial verification take place?

Answer 11

Before an installation is put into service

Question 12

According to the BS7671 what must any additional components of an installation do?

Answer 12

It must be confirmed that any new additions or alterations should not invalidate the rating of the installation, for example, that the maximum current draw cannot exceed 32A if that is the rating of the circuit that is being added to.

Question 13

Before adding additional components to an installation, what should take place?

Answer 13

A pre-work survey

Question 14

What kind of work requires initial verification?

Answer 14

For new work or additions/ alterations

Question 15

What kind of installation requires Periodic Inspection?

Answer 15

An existing installation

Question 16

According to the BS7671 section 416, what must all electrical equipment have in terms of protection?

Answer 16

One of the provisions for basic protection.

Question 17

What is the function of insulation?

Answer 17

Insulation is intended to prevent contact with live parts.

Question 18

What are the three main safety features associated with performing an insulation resistance test?

Answer 18

1. Protection against direct contact shocks
2. Preventing short-circuit and earth faults
3. Prevention of leakage currents

Question 19

What does IP stand for?

Answer 19

IP stands for ingress protection

Question 20

True or false:
IP18 means that the object is watertight but not finger tight.

Answer 20

True.
The first number denotes protection from solids and the second denotes protection from liquids.

Question 21

True or false:
IP61 means that the object is watertight but not finger tight.

Answer 21

False.

Question 22

What is prospective fault current (Ipf)?
What is this measured in?

Answer 22

Prospective Fault Current (Ipf) is the maximum amount of current that could flow between the line conductor and the earth conductor in an installation.
This is measured in kA.

Question 23

What is prospective short circuit current (PSCC)?
What is this measured in?

Answer 23

Prospective short circuit current (PSCC) is the highest possible amount of current that could flow between line conductors and neutral conductors.
This is measured in kA.

Question 24

Define power factor (PF).
Why is power Factor important to know?

Answer 24

Power Factor is the ratio to which the supplied power (apparent power) is actually used by the sytem, circuit, installation, piece of equipment etc.
It is displayed as a number, usually something like 0.78.

This is useful for determining the amount of power used by a circuit.

Question 25

What two factors may contribute to a poor power factor in AC circuits?

Answer 25

• High inductance
• High capacitance

Question 26

Define an extraneous conductive part

Answer 26

This is a metallic part within a building that do not form part of the electrical system, but can become live in the event of a fault.

Question 27

Define overcurrent

Answer 27

Overcurrent is an excessive amount of current, which is above the design current of the circuit.

Question 28

What are the three main types of eletrical faults which generate excessive current?

Answer 28

• Overload faults
• Earth faults
• Short circuit faults

Question 29

What is the fundamental effect of an excessive amount of current flowing through a conductor?

Answer 29

An increase in temperature, which destroys the insulating properties of cabling insulation.