T&I Periodic

7/29/2019 T&I Periodic

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Electrical Inspection and Testing

C & G 2391

MODULE 6

Periodic Inspection & Testing


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Purpose

To determine that the installation is in a satisfactory

condition for continued service i.e. it meets thegeneral objective of the LAW, this is verified by

assuring the requirements of BS7671 are complied

with.

Legislation requires that certain installations are

maintained in a safe condition and therefore must be

periodically inspected and tested


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Public bodies

Insurance companies

Mortgagors

Additionally

Periodic Inspection and Testing should be considered:-

Changes of ownership or tenancy Changes of use of the premises

After alterations or additions Significant changes in loading

Possible Damage e.g Fire, Flood etc

Inspection and testing may be required by:-

Licensing Authorities


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731-01-03

Careful Scrutiny backed up by Testing

711-01-02 and 712-01-03(xvii) requires information in

the form of diagrams, charts etc to be made available

to the person carrying out the tests

Inspection is the Vital initial operation,

Testing supports the inspection.

The work must be carried out safely.

Where information is not available some exploratory

work will be required.


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Periodic Test Sequence

Continuity of protective conductors

PolarityEarth fault loop impedance

Insulation Resistance

Operation of devices for Isolation and SwitchingOperation of Residual Current Devices

In addition where appropriate: Continuity of Ring final circuits,Earth electrode resistance, Manual operation of circuit breakers etc,

Electrical separation of circuits, Protection by non-conducting locations


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How Much Testing ?

All socket outlets should be checked for polarity

To check bonding conductor continuity the bonds must be

disconnected

The mains must be off for this test

All heavy current equipment e.g. bus-bars, main

switches etc should be tested.

Random selection of points equal to 10% of the installation, if

faults are found this is expanded to 25% and then 100% iffurther faults are found.

As agreed with the client under extent and limitation


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Extent and Limitations

Agree with the client (before starting a detailed inspection and

test) the Extent of the installation to be inspected and anylimitation put on the process by the client

Record the details of this agreement on the Report form

Parts of the installation,

certain floors, sampling

a number of distribution boards

limited to certain types of equipment e.g lighting

Failure to identify these items may result in contractual

liabilities


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Periodic Inspection and Testing Report

744-01-01 On completion of the inspection and testing, a

Report form together with a schedule of test results and a

schedule of inspection should be given to the person ordering

the work.

744-01-02 Any damage, deterioration, defects, dangerousconditions and non-compliance with the requirements which

may give rise to danger, together with any limitations of the

inspection and testing must be recorded.

Guidance on the action to be taken is given by numbering each

non-compliance to1 4


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1)a) What types of inspection and tests need to be carried out

Initial Verification for the new work and Periodic Inspectionand test for the existing installation

Section B. A small office block in Stourbridge

b) State the documentation that should be completed and why

An Electrical Installation Certificate for the new work

(additional circuits have been installed) and a Periodic

Inspection Report for the existing installation

Both of these documents must be accompanied with a

schedule of inspection and a schedule of test results


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The Health and Safety at Work Act and the Electricity at Work

Regulations

d) List the test equipment required for this installation

i) Low reading ohm meter (continuity tester)

ii) Insulation resistance meter

iii) Earth loop impedance tester

iv) Prospective fault current tester

e) If no documentation is available for the installation what

action is required

Some exploratory work, to establish the criteria

c) State the Statutory Regulations that need to be adhered to


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i) Wear and Tear, the installation is 20yrs old, theaccessories,switches etc may show signs of deterioration

ii) Excessive loading e.g. connection of conductors (effects of

heat etc over 20 years)

iii) Damage, the installation equipment may be damaged to the

extent it has become dangerous e.g. exposure of live parts

iv) Corrosion, the conduit is being used as a c.p.c, if this iscorroded the shock protection may be affected

v) Compliance with BS7671, there have been considerable

changes in the standard over the installation life

2)a) List five areas of inspection to be considered on the

existing installation. Give one reason for each


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b) Before commencing testing on the existing installation,

what should be agreed with the client

The extent and limitations that are to be imposed by the client

c) List the correct sequence of tests required for the existing

installation

i) Continuity of protective conductors (including bonds)

ii) Polarity

iii) Earth fault loop impedance

iv) Insulation resistance

v) Operation of devices for isolation and switching

If there are ring final circuits in the existing installation these

should also be tested (as item (ii) )


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Note:- There is no indication that the installation contains

RCDs or Circuit Breakers, these tests therefore would not be

required. Also alternative methods may be used provided theresults are no less effective.

d) List five of the inspection check list items for the new work

i) Connection of conductors

ii) Identification of conductors

iii) Conductor current carrying capacity

iv) Correct connection of accessories

v) Erection methods


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e) List the correct sequence of tests required for the new

installation

i) Continuity of protective conductors including bondsii) Continuity of ring final circuits

iii) Insulation resistance

iv) Polarity

v) Earth loop impedance

vi) Prospective fault currentvii)Functional testing


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Test open ends of the ring, phase to phase, neutral to neutral, cpc to cpc

RECORD results

Cross connect phase to neutral, test phase to neutral at each socket

Reading should be of the phase to phase reading of the open ring

Cross connect phase to cpc, test phase to cpc at each socket

Reading should be approximately

of the phase to phase + of the cpc to cpc

Testsequence

3) Describe how to carry out the ring final circuit continuity

test on the new installation


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4) Describe how to carry out the insulation resistance test on

the existing installation

Test preparation:- All current using equipment should be

disconnected or turned off, the supply to the main

distribution board should be isolated, all protective devices

should be in position or on, all local switches on, anyequipment which may be damaged by the test should be

disconnected or by-passed. The test is then conducted

between:-

i) All live conductors and

ii) All live conductors to Earth


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5) Draw a fully labelled diagram of the complete earth fault

path of the new lighting circuit.

a) Supply phase, b) supply phase conductor, c) circuit phase

conductor, d) exposed-conductive-part of the light, e) c.p.c of

the lighting circuit, f) return path (PEN i.e the earthed neutral)

of the supply cable

a

b c

e

d

f


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6) Because the existing wiring system does not contain

separate c.p.cs describe the three stages of verification that

need to be confirmed.

i) Visual inspection along the length of all conduits to check

their condition regarding corrosion etc

ii) If the conduit appears in good condition measure its

resistance with a low reading ohm meter

iii) If there is any doubt as to its suitability e.g. where itsphysical condition cannot be checked, a high current

injection test is required (not exceeding 25A)

f h i fi l i i i l l h


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7)a) If the ring final circuit R1 + R2 is 0.72, calculate the

approximate reading of Zs

Zs = Ze + (R1 + R2) = 0.2 + 0.72 = 0.92

b) If the maximum tabulated Zs for this circuit is 1.2,

calculate if the reading in (a) is acceptable

There are no correction factors stated, use the rule of thumb

1.2 x 0.75 = 0.9 < 0.92 measured (circuit fails)

c) State what factors need to be considered before measured

earth loop impedance values are compared againstmaximum tabulated Zs values

i) Ambient temperature factors (when not measured at 200C)

ii) Cable temperature factors (not at its operating temperature)

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