2391- inspection & testing (advanced)

8/10/2019 2391- Inspection & Testing (Advanced)

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www.ElectaCourse.com

Inspection Testingnspection Testing

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ElectaCourse.com

2005 Last Updated August 2006


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This presentation is suitable for those studying for the

City & Guilds 2391 and 2400 courses


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The presentation includes guidance and

continuous self-assessment


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In order to work through this presentation you will need copies

Of the following publications

BS 7671:2001 (16th Edition IEE Wiring Regulations)

Guidance Note 3 (Inspection and Testing


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To ensure the safety of any electrical installation it should be

inspected, tested and the necessary certification completed:

Before being put into service (initial verification)

At regular intervals thereafter (Periodic Inspection Report)

On completion of any alteration or addition


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For an initial verification

BS 7671:2002 states:

Installed equipment to an appropriate standard, i.e. BS, BS EN

Correctly selected and erected

Not visibly damaged or defective as to impair safety


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The Periodic Installation Report (PIR)

BS 7671:2001 states:

Periodic inspection and testing of an electrical installation

shall be carried out to determine, so far as is reasonably

practicable, whether the installation is in a satisfactory condition

for continued service


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Generally, the main reason for undertaking an inspection and

test is to ensure that the installation is safe to use


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What Are the likely reasons for an installation failing to be safe?

Age

Wear and tear

Damage, i.e. fire, flooding etc

Electrical overload

DIY enthusiasts

Unscrupulous contractors


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What factors would influence the need for a PIR

Expiry of current certificate

Change of ownership or use of the installation

As a result of damage or electrical overloading

Mortgage/insurance purposes

Compliance with current regulations

Local bylaw requirements


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What factors would influence the safety of an installation?

Poorly installed equipment/accessories

Loose connections giving rise to shock and or fire

Inadequate overcurrent protection of equipment and circuits

Underrated/overloaded circuit conductors

Inadequate/non-existent earthing or bonding arrangements


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Inspection always proceeds testing

Prior to visual inspection the supply to the installation or part

of the installation undergoing inspection should be

disconnected from the supply


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Electrical installations which comply with BS 7671:2001 areregarded by the Health & Safety Executive as likely to achieve

conformity with which statutory regulations?


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The Electricity at Work Regulations 1989


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Page 8BS 7671:2001 Note by the Health and Safety Executive


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Identify THREE areas which should be given consideration prior toundertaking alterations or additions to an existing electrical

installation


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The ability of existing equipment including that of the supplier isadequate for the additional load

The earthing arrangements are adequate

The bonding arrangements are adequate


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Page 14130-07 Additions and alterations to an installation

Regulation 130-07-01


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Identify SIX characteristics of the incoming electrical supply thatwould need to be ascertained by the person undertaking an

inspection and test of an electrical installation


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(i) the nominal voltage(s)

(ii) the nature of the current and frequency

(iii) the prospective short circuit current at the origin

(iv) the external earth fault loop impedance (Ze)

(v) the suitability for the requirements of the installation

including the maximum demand

(vi) the type and rating of the overcurrent protective device


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Page 33313 Nature of Supply



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Identify two precautions that should be observed duringinspection and testing of an electrical installation


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avoid danger to persons

avoid damage to property and installed equipment


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Page 170Chapter 71 - Initial Verification



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State the THREE requirements of BS 7671 with regard to installedelectrical equipment


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(i) in compliance with Section 511

(ii) correctly selected and erected in accordance with the

Regulations

(iii) not visibly damaged or defective so as to impair safety


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Page 170 - Inspection

Regulation 712 - 01 - 02

Note: Section 511 deals with compliance with standards. All

equipment should comply with the appropriate British Standard or

Harmonized Standard - See page 84 - Selection and Erection of

Equipment


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Identify TWO statutory, and FIVE non-statutory documents that aninspecting engineer may need to refer when undertaking an

inspection and test on an electrical installation


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Statutory:

Health and Safety at Work Act etc 1974

Electricity at Work Regulation 1989

Non-statutory:

BS 7671:2001

IEE Guidance Note 3 (Inspection and Testing

IEE On-Site Guide

GS 38 Equipment used by electricians (HSE Guidance) Memorandum of Guidance to The Electricity at Work Regulations


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Visual inspection always precedes testing


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From the inspection check list within BS 7671 Identify THREE

methods of protection against direct electric shock (contact)


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Insulation of live parts

Barriers

Enclosures


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Risk of direct contact. Barrier removed and not replaced


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Risk of direct contact. Barrier removed and not replaced


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Risk of direct contact.


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Page 170


Two additional methods of protection against direct shock of a

special nature are:

Placing out of reach

ObstaclesNote: this method of protection is intended to prevent

inadvertent contact with live parts and therefore areas

incorporating this type of protection should only be accessible to

skilled persons only


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From the inspection check list within BS 7671 Identify THREE

methods of protection against indirect contact


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EEBAD

Class II

Electrical Separation

Non-conducting location

Earth-free local equipotential bonding


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Page 170/171


Note: Protection by non-conducting location and earth-free local

equipotential bonding are both of a special nature and very rarely

encountered


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From the inspection check list within BS 7671 Identify TWO methods

of protection against both direct and indirect contact


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Separated extra-low voltage (SELV)

Limitation of discharge energy

El C


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Page 170/171


El t C


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From the inspection check list within BS 7671 Identify FOUR types of

protective conductor

El t C


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earthing conductor

circuit protective conductor (CPC)

main equipotential bonding conductor

supplementary equipotential bonding conductor

www ElectaCourse com


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Page 170/171




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Presence of main equipotential bonding conductors



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One requirement from Regulation 712-01-03 is the selection of

equipment and protective measures appropriate to external

influences. List the external influences likely to be encountered by

an electrical installation located within a commercial greenhouse

accessible to the general public.



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Ultra-violet radiation

Extremes of temperature

Mechanical damage

Water/moisture/humidity

Rodent attack

Chemicals

Corrosion

Vandalism



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Page 170/171




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Regulation 712 - 01 - 03 requires visual inspection to ensure

cables are routed in safe zones and also considers erection

methods.

Here are some examples of non-compliance


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Regu

lations

5

22-08

Routing of cables



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Regu

lation

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2-08

Routing of cables



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Regu

lations

5

22-08

Routing of cables



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Regu

lations

522-08

Routing of cables



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Regu

lations

522-08

Routing of cables



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Selection of conductors for current carrying capacity

Identification of conductors

Selection of conductors for voltage drop

Requirements for circuit conductors



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Regulation 712 - 01 - 03 requires visual inspection to ensure

cables are correctly and adequately identified

Here are some examples of non-compliance



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Regu

lation

514-01-01/0

2




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Regu

lation

514-01-01/0

2



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Regu

lation

514-01-01/0

2




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Regulation

514-01-01/0

2



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Regulation

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6-01-01

Connection between conductors



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Regulation

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6-01-01

Taped joint between PVC and VRI cables



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Regulation

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6-01-01

Taped joint between PVC and VRI cables



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Regulation

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6-01-01

Faulty conductor termination



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Result of insecure/loose connection



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Result of insecure/loose connection



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The Regulations require that connections and joint be accessible

for inspection, testing and maintenance. There are however FOUR

situations where this regulation does not apply. Identify these

FOUR situations.



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Page 100


(i) A compound-filled or encapsulated joint

(ii) A connection between a cold tail and a heating element

(iii) A joint made by welding, soldering, brazing or compression

tool

(iv) A joint forming part of the equipment complying with the

appropriate product standard



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Page 100Regulation 526-04-01



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Erection of wiring systems



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Lid/covers not fitted


R


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Regulation

522

08




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Enclosure door not secured



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Equipment door forced open to defeat interlock



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Enclosure not secured to wall


I


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Intern

ationalP

rotection


I


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Enclosure not secured to wall

Intern

ationalP

rotection



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A visual inspection is to be carried out on a domestic installation.

Detail FIVE specific areas of visual inspection at the origin of thisinstallation.

For the purpose of this exercise the PES supply has been isolated

by the removal of the service head fuse.



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Presence and size of earthing conductor

Presence and size of main equipotential bonding conductors

Type and rating of overcurrent protective devices

Prospective breaking capacity of overcurrent devices

Circuit and conductor identification

Type of earthing arrangement

IP rating of distribution board



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A miniature circuit breaker within the distribution board is marked

as a Type 2, M6 device.

Describe the characteristics of this device and state to which

Standard it complies.



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As the device carries an M rating its has been manufactured to

BS 3871 (now replaced by BS EN 60898 device)

M indicates its maximum prospective fault current value M6 = 6kA

6000A.

Type 2 indicates the instantaneous tripping characteristic4.07.0In.



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Page 60 Guidance Note 3

Table 4.2 Rated short-circuit capacities



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State TWO functional tests that may be applied at the distribution

board



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Operation of circuit breakers

Operation of the main switch



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State the hand lighting would you use if working in a confined

damp location?



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Hand lighting provided from an SELV (Separated Extra-Low Voltage)

supply



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Separated Extra-Low Voltage (SELV)

Supplied from a recognised safety source - Regulation

ELV conductors NOT referenced to earth - Regulation

Within voltage constraints - Regulation



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The following information relates to a circuit breaker complying

with BS EN 60898.

Type B

Icn 10

Ics 7.5

State the meaning of each of the above terms



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Type B relates to the instantaneous tripping characteristic of

the device. In this case 3 - 5 In (where In is the rating of thedevice in amperes

Icn - the rated short-circuit capacity (indicted on the device)

Ics the service short-circuit capacity.



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Page 60 Guidance Note 3

Table 4.2 Rated short-circuit capacities



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State TWO characteristics of the incoming supply that may be

determined by enquiry or measurement



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Prospective fault current

External earth fault loop impedance



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Page 33

313 Nature of supply


Any of the following characteristics may be obtained bymeasurement or enquiry:

Nominal voltage, nature of current and frequency. Generally

however the two most common characteristics determined by

enquiry and calculation are Ze (external earth fault loop

impedance) and prospective fault current Ip.



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Regulation 313-01-01 requires that the supply characteristics from

whatever source be verified. Give TWO examples of sources otherthan that of the PES supply that may supply an installation



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Those of:

standby generators (alternators

Uninterruptible Power Supplies (UPS)



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An RCD protected A2 radial circuit feeds five 13A socket outlets to

BS 1363. The circuit has been added to an existing installationwithin domestic premises.

identify the relevant document that should be completed for this

installation

The sequence of tests, in the correct order that should beapplied to this circuit

If the supply to the installation is TN-S state the main purpose of

the RCD

In the correct sequence identify the tests that should be applied

to the RCD



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Minor Works Certificate

Continuity of CPCs

Provide supplementary protection against direct contact

x In

1 x I n

5 x In



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Page29GN3

2.7.4 The sequence of tests

Page 171

Regulation 713-01-01 (sequence of tests)



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State the action you would take if ONE of the tests undertaken in

question 22 indicated a defect



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Determine whether fault would have any adverse effect on any

previous tests result

When rectified repeat any tests that may have been adversely

affected



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Explain why applying a functional test only, to a residual current

device is unacceptable during a periodic inspection (PIR)

How often should an RCD undergo functional testing



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Functional testing relies upon an imbalance between phase and

neutral within the toroidal winding of the device. It does not verify:

the presence of earthing conductor

the presence of any CPCs

the presence of any earthing arrangements

does not verify operating time or current

Functional testing applied at three month intervals



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Page 61 GN

32.7.16 Operation of residual current devices

Page 173

Regulation 713-13-01 Functional testing



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Explain why an insulation resistance test instrument is required to

produce a current of 1 mA when loaded at the minimum acceptablevalue of insulation as permitted by BS 7671?



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Effect of instrument loading on output (terminal) voltage

0.5M 1.0M 10M

Terminal voltage

500V d.c.

Insulation resistance M

Minimum acceptable value for 230/400V circuits



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Page 86 GN

4.4 Insulation resistance testers

Page 172


An effective test for insulation can only be made if the outputvoltage is maintained by the instrument



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Explain the possible danger of removing test probes from a circuit

under test before releasing the test button of an insulationresistance tester


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Page 86 GN

4.4 Insulation resistance testers



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Explain the term standing voltage and the electrical test that may

give rise to this situation

Describe TWO methods of reducing the risk of shock from these

standing voltages



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Restrict duration of instrument test currents

Place warning notices in location of test area



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Page 86 GN

4.6 Earth fault loop impedance testers

Restrict test currents to 40mS


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Page 86 GN

4.6 Earth fault loop impedance testers

Instruments to BS EN 61557-3 will comply with the requirements of

BS 7671 with regard to impedance testers



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State the requirements of the Electricity @ Work Regulations 1989

with regard to access and lighting whilst undertaking a visualinspection of the distribution board.



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Working space

Adequate to allow to pull back away from live conductors

without hazard

Adequate to allow persons to pass one another safely

Lighting

Natural light preferred. Where this is impractical permanent

lighting arrangements of an acceptable design should be

provided. At times, lighting may need to be temporary, i.e.

torches or hand lamps. Whichever method is employed the level

of lighting must be adequate to avoid injury



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Page 38

Regulation 15 Working space, access and lighting



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Means of escape in the event of an emergency



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Means of escape blocked in the event of an emergency



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Safe access and exit from workplace?



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A safe and tidy workplace!

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