Public Comment Draft

Zambian Standard

WIRING OF PREMISES – CODE OF PRACTICE

Part 4: Inspection and Testing

ZAMBIA BUREAU OF STANDARD

DZS 791-4: 2013

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DATE OF PUBLICATION

This Zambian Standard has been published under the authority of the Standards Council of theZambia Bureau of Standards on ……………...

ZAMBIA BUREAU OF STANDARDS

The Zambia Bureau of Standards is the Statutory National Standards Body for Zambiaestablished under an act of Parliament, the Standards Act, Cap 416 of 1994 of the Laws ofZambia for the preparation and promulgation of Zambian Standards.

REVISION OF ZAMBIAN STANDARDS

Zambian Standards are revised, when necessary, by the issue of either amendments or of revisededitions. It is important that users of Zambian standards should ascertain that they are inpossession of the latest amendments or editions.

CONTRACT REQUIREMENTS

A Zambian standard does not purport to include all the necessary provisions of a contract. Usersof Zambian standards are responsible for their correct application.

TECHNICAL COMMITTEE RESPONSIBLE

This Zambian standard was prepared by the Technical Committee – TC 5/3 upon which thefollowing organisations were represented:

Copperbelt Energy Corporation PlcEnergy Regulation BoardEngineering Institution of ZambiaLunsemfwa Hydroelectric Power StationThe University of Zambia, School of EngineeringZambia Bureau of StandardsZESCO Limited

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TABLE OF CONTENTS

FOREWORD................................................................................................................................ iii

1. SCOPE.................................................................................................................................... 1

2. INITIAL VERIFICATION .................................................................................................. 1

2.1 General ............................................................................................................................ 1

2.2 Inspection........................................................................................................................ 2

2.3 Testing............................................................................................................................. 3

3. PERIODIC INSPECTION AND TESTING....................................................................... 9

3.1 General ............................................................................................................................ 9

3.2 Frequency of Inspection and Testing ............................................................................ 10

4. CERTIFICATION AND REPORTING............................................................................ 10

4.1 General .......................................................................................................................... 10

4.2 Initial Verification......................................................................................................... 11

4.3 Additions and Alterations ............................................................................................. 11

4.4 Periodic Inspection and Testing.................................................................................... 12

Appendix 1 Methods for Measuring The Insulation Resistance/Impedance of Floors and

Walls To Earth or To The Protective Conductor System ....................................................... 13

Appendix 2 Measurement of Earth Fault Loop Impedance: Consideration of the

Increase of the Resistance of Conductors with Increase of Temperature ............................. 17

Appendix C Model Forms for Certification and Reporting .............................................. 18

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FOREWORD

The Zambia Bureau of Standards (ZABS) is the Statutory Organization established by an Act ofParliament. ZABS is responsible for the preparation of national standards through its variousTechnical committees composed of representation from government departments, the industry,academia, regulators, consumer associations and non- governmental organizations.

This National Standard has been prepared in accordance with the procedures of the ZABS. Allusers should ensure that they have the latest edition of this publication as standards are revisedfrom time to time.

No liability shall attach to ZABS or its Director, Employees, servants or agents includingindividual experts and members of its Technical Committees for any personal injury, propertydamage or other damages of any nature whatsoever, whether direct or indirect, or for costs(Including legal fees) and expenses arising out of the publication, use of, or reliance upon thisZABS publication or any other ZABS publication.

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COMPLIANCE WITH A ZAMBIAN STANDARD DOES NOT OF ITSELF CONFERIMMUNITY FROM LEGAL OBLIGATIONS.

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ZAMBIA BUREAU OF STANDARDS

ZAMBIAN STANDARD

WIRING OF PREMISES - CODE OF PRACTICE

Part 4: Inspection and Testing

1. SCOPE

This standard provides requirements for initial and periodic verification of an electricalinstallation.

Chapter 2 provides requirements for initial verification, by inspection and testing, of an electricalinstallation to determine, as far as reasonably practicable, whether the requirements of the otherparts of ZS 791 have been met and requirements for the reporting of the results of the initialverification. The initial verification takes place upon completion of a new installation orcompletion of additions or of alterations to existing installations.

Chapter 3 provides requirements for periodic verification of an electrical installation todetermine, as far as reasonably practicable, whether the installation and all its constituentequipment are in a satisfactory condition for use and requirements for the reporting of the resultsof the periodic verification.

2. INITIAL VERIFICATION

2.1 General

2.1.1 Every installation shall, during erection and on completion before being put into service,be inspected and tested to verify, so far as is reasonably practicable, that the requirements of theRegulations have been met.

Precautions shall be taken to avoid danger to persons and livestock, and to avoid damage toproperty and installed equipment, during inspection and testing.

2.1.2 The result of the assessment of the fundamental principles, Section 5.1 of DZS 791 Part1, the general characteristics required by Sections 6.1.1 to 6.1.3 of DZS 791 Part 1, together withthe information required by 3.5.7.1, shall be made available to the person or persons carrying outthe inspection and testing.

2.1.3 The verification shall include comparison of the results with relevant criteria to confirmthat the requirements of the Regulations have been met.

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2.1.4 For an addition or alteration to an existing installation, it shall be verified that theaddition or alteration complies with the Regulations and does not impair the safety of theexisting installation.

2.1.5 The verification shall be made by a competent person.

2.1.6 On completion of the verification, according to 2.1.1 to 2.1.5, a certificate shall beprepared.

2.2 Inspection

2.2.1 Inspection shall precede testing and shall normally be done with that part of theinstallation under inspection disconnected from the supply.

2.2.2 The inspection shall be made to verify that the installed electrical equipment is:

i). in compliance with the requirements of Section 2.2 of DZS 791 Part 3 (this may beascertained by mark or by certification furnished by the installer or the manufacturer), and

ii). correctly selected and erected in accordance with the Regulations, taking into accountmanufacturers’ instructions, and

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

21.2.3 The inspection shall include at least the checking of the following items where relevant,including as appropriate all particular requirements for special installations or locations (DZS791 Part 5):

i). Connection of conductorsii). Identification of conductorsiii). Routing of cables in safe zones, or protection against mechanical damage, in compliance

with Section 3.4 of DZS 791 Part 3.iv). Selection of conductors for current-carrying capacity and voltage drop, in accordance with

the designv). Connection of single-pole devices for protection or switching in line conductors onlyvi). Correct connection of accessories and equipmentvii). Presence of fire barriers, suitable seals and protection against thermal effectsviii). Methods of protection against electric shock

a). both basic protection and fault protection, i.e.:- SELV- PELV- Double insulation- Reinforced insulation

b). basic protection (including measurement of distances, where appropriate). i.e.:- protection by insulation of live parts- protection by a barrier or an enclosure- protection by obstacles

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- protection by placing out of reach

c). Fault protection:i). automatic disconnection of supplyconfirmed for presence and sized in accordance with the design- earthing conductor- circuit protective conductors- protective bonding conductors- supplementary bonding conductors- earthing arrangements for combined protective and functional purposes

presence of adequate arrangements for alternative source(s), where applicableFELV

- choice and setting of protective and monitoring devices (for fault and/orovercurrent protection)

ii). non-conducting location including measurement of distances, whereappropriate) absence of protective conductors

iii). earth-free local equipotential bondingpresence of earth-free protective bonding conductors

iv). electrical separation

d). additional protection

ix). Prevention of mutual detrimental influencev). Presence of appropriate devices for isolation and switching correctly locatedvi). Presence of undervoltage protective devicesvii). Labeling of protective devices, switches and terminalsviii). Selection of equipment and protective measures appropriate to external influencesix). Adequacy of access to switchgear and equipmentx). Presence of danger notices and other warning signsxi). Presence of diagrams, instructions and similar informationxii). Erection methods

2.3 Testing

2.3.1 General

The tests of 2.3.2 to 2.3.13, where relevant, shall be carried out and the results compared withrelevant criteria.

Measuring instruments and monitoring equipment and methods shall be chosen in accordancewith the relevant parts of IEC 61557. If other measuring equipment is used, it shall provide noless degree of performance and safety.

When undertaking testing in a potentially explosive atmosphere, appropriate safety precautionsin accordance with IEC 60079-17 and IEC 61241-17 are necessary.

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The tests of 2.3.2 to 2.3.6, where relevant, shall be carried out in that order before the installationis energized. Where the installation incorporates an earth electrode, the test of 2.3.7 shall also becarried out before the installation is energized.

If any test indicates a failure to comply, that test and any preceding test, the results of which mayhave been influenced by the fault indicated, shall be repeated after the fault has been rectified.Some methods of test are described in IET Guidance Note 3, Inspection & Testing, published bythe Institution of Engineering and Technology. Other methods are not precluded provided theygive valid results.

2.3.2 Continuity of conductors

2.3.2.1 Continuity of protective conductors, including main and supplementary equipotentialbonding. A continuity test shall be made. It is recommended that the test be carried out with asupply having a no-load voltage between 4 V and 24 V. d.c. or a.c., and a short-circuit current ofnot less than 200 mA.

2.3.3 Continuity of ring final circuit conductors

A test shall be made to verify the continuity of each conductor, including the protectiveconductor, of every ring final circuit.

2.3.4 Insulation resistance

2.3.4.1 The insulation resistance shall be measured between live conductors and between liveconductors and the protective conductor connected to the earthing arrangement. Whereappropriate during this measurement, line and neutral conductors may be connected together.

2.3.4.2 The insulation resistance measured with the test voltages indicated in Table 2-1 shallbe considered satisfactory if the main switchboard and each distribution circuit tested separately,with all its final circuits connected but with current-using equipment disconnected, has aninsulation resistance not less than the appropriate value given in Table 2-1.

NOTE: More stringent requirements are applicable for the wiring of fire detection and fire alarm systems inbuildings

Table 2-1: Minimum values of insulation resistance

Circuit nominal voltage(V)

Test Voltage dc(V)

Minimum insulationresistance

(MΩ)

SELV and PELV 250 > 0.5

Up to and including 500V with the exceptionof the above systems 500 > 1.0

Above 500V 100 > 1.0

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Table 2-1 shall be applied when verifying insulation resistance between non-earthed protectiveconductors and Earth.

Where surge protective devices (SPDs) or other equipment are likely to influence the verificationtest, or be damaged, such equipment shall be disconnected before carrying out the insulationresistance test. Where it is not reasonably practicable to disconnect such equipment (e.g. fixedsocket-outlet incorporating an SPD), the test voltage for the particular circuit may be reduced to250 V d.c., but the insulation resistance shall have a value of at least 1MΩ

NOTE 1: In locations exposed to fire hazard, a measurement of the insulation resistance between the liveconductors should be applied. In practice, it may be necessary to carry out this measurement duringerection of the installation and before connection of the equipment.

NOTE 2: Insulation resistance values are usually much higher than those of Table 2-1.

2.3.4.3 Where the circuit includes electronic devices which are likely to influence the resultsor be damaged, only a measurement between the live conductors connected together and theearthing arrangement shall be made.NOTE: Additional precautions, such as disconnection, may be necessary to avoid damage toelectronic devices.

2.3.4 Protection by SELV, PELV or by electrical separation

It shall be verified that the separation of circuits is in accordance with 2.3.4.1 in the case ofprotection by SELV, 2.3.4.2 in the case of protection by PELV and 2.3.4.3 in the case ofprotection by electrical separation. The resistance values obtained in the tests of 2.3.4.1 to 3 shallbe at least that of the circuit with the highest voltage present in accordance with Table 2-1.

2.3.4.1 Protection by SELV

The separation of the live parts from those of other circuits and from earth, according to section3.6 of DZS 791 Part 2, shall be confirmed by a measurement of the insulation resistance. Theresistance values obtained shall be in accordance with Table 2-1.

2.3.4.2 Protection by PELV

The separation of the live parts from other circuits, according to section 3.6 of DZS 791 Part 2,shall be confirmed by a measurement of the insulation resistance. The resistance values obtainedshall be in accordance with Table 1-1.

2.3.4.3 Protection by Electrical Separation

The separation of the live parts from those of other circuits and from earth, according to section3.5 of DZS 791 Part 2, shall be confirmed by a measurement of the insulation resistance. Theresistance values obtained shall be in accordance with Table 2-1.

In the case of electrical separation with more than one item of current-using equipment, either bymeasurement or by calculation, it shall be verified that in case of two coincidental faults with

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negligible impedance between different line conductors and either protective bonding conductoror exposed-conductive-parts connected to it, at least one of the faulty circuits shall bedisconnected. The disconnection time shall be in accordance with that for the protective measure,automatic disconnection of supply in a TN system

2.3.4.4 Functional extra-low voltage circuits

Functional extra-low voltage circuits shall meet all the test requirements for low voltage circuits.

2.3.4.5 Basic Protection by a Barrier or an Enclosure Provided During Erection

Where basic protection is intended to be afforded by a barrier or an enclosure provided during anerection in accordance with 3.8.2 of DZS 791 Part 2, it shall be verified by test that each barrieror enclosure affords a degree of protection not less than IPXXB or IP2X or IPXXD or IP4X asappropriate, where that rule so requires.

2.3.5 Insulation Resistance/Impedance of Floors and Walls

2.3.5.1 Where it is necessary to comply with the requirements of 3.10.1 of DZS 791 Part 2, atleast three measurements shall be made in the same location, one of its measurements beingapproximately 1m from any accessible extraneous-conductive-part in the location. The other twomeasurements shall be made at greater distances. The measurement of resistance/impedance ofinsulating floors and walls is carried with a system voltage to earth at nominal frequency. Theabove series of measurements shall be repeated for each relevant surface of the location

NOTE: Further information on measurements of insulation resistance/impedance of the floors and walls can foundin Appendix 1

2.3.5.2 Any insulation or insulating arrangement of extraneous-conductive-parts intended tosatisfy 3.10.1.4 (iii) of DZS 791 Part 2:

i). when tested at 500V d.c. shall not be less than 1MΩii). shall be able to withstand a test voltage of at least 2kV a.c r.m.s, andiii). shall not pass a leakage current exceeding 1mA in normal condition of use

2.3.6 Polarity

A test of polarity shall be made and it shall be verified that:i). every fuse and single-pole control and protective device is connected in the line conductor

only, andii). except for E14 and E27 lamp holders to IEC 60238 in circuits having an earthed neutral

conductor, centre contact bayonet and Edison screw lamp holders have the outer orscrewed contacts connected to the neutral conductor, and

iii). Wiring has been correctly connected to socket-outlets and similar accessories

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2.3.7 Earth Electrode Resistance

Where the earthing system incorporates an earth electrode as part of the installation, theelectrode resistance shall be measuredNOTE: Where a measurement of RA is not practicable, the measured value of external earth faultloop impedance may be used.

2.3.8 Protection by automatic disconnection of the supply

Where RCDs are applied also for protection against fire, the verification of the conditions forprotection by automatic disconnection of the supply may be considered as satisfying the relevantrequirements of Chapter 4 of DZS 791 Part 2.

2.3.8.1 General

The verification of the effectiveness of the measures for fault protection by automaticdisconnection of supply is effected as follows:

a) TN system

Compliance with 3.3.4 of DZS 791 Part 2 shall be verified by:

i). measurement of the earth fault loop impedance (see 2.3.9)ii). verification of the characteristics and/or the effectiveness of the associated protective

device.

This verification shall be made:- for overcurrent protective devices, by visual inspection (i.e. short-time or

instantaneous tripping setting for circuit-breakers, current rating and type for fuses)- For RCDs, by visual inspection and test.

The effectiveness of automatic disconnection of supply by RCDs shall be verified usingsuitable test equipment according to IEC61557-6 (see 2.3.1) to confirm that the relevantrequirements in Chapter 4 of DZS 791 Part 2 are met.

The disconnection times required by Chapter 4 of DZS 791 Part 2 shall be verified.

b) TT systemCompliance with 3.3.5 of DZS 791 Part 2 shall be verified by:i). measurement of the resistance of the earth electrode for exposed-conductive-parts of

the installation (see 2.3.7)

NOTE: Where a measurement of RA is not practicable the measured value of external earth fault loopimpedance may be used.

ii). verification of the characteristics and/or effectiveness of the associated protectivedevice. This verification shall be made:

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- for overcurrent protective devices, by visual inspection (i.e. short-time orinstantaneous tripping setting for circuit-breakers, current rating and type for fuses)

- for RCDs, by visual inspection and test.

The effectiveness of disconnection of supply by RCDs shall be verified using suitable testequipment according to IEC 61557-6 (see 1.3.1) to confirm that the relevant requirementsin Chapter 4 of DZS 791 Part 2 are met.

The disconnection times required by Chapter 4 of DZS 791 Part 2 shall be verified.

c) IT system

Compliance with 3.3.6 shall be verified by calculation or measurement of the current Id in case ofa first fault at the line conductor or at the neutral.

NOTE 1: The measurement is made only if calculation is not possible because all the parameters are not known.Precautions are to be taken while making the measurement in order to avoid the danger due to a doublefault.

Where conditions that are similar to conditions of a TT system occur, in the event of a secondfault in another circuit (see 3.3.6.4(ii)), verification is made as for a TT system (see point b) ofthis regulation).

Where conditions that are similar to conditions of a TN system occur, in the event of a secondfault in another circuit (see 4.3.1.6.4(i)), verification is made as for a TN system (see point a) ofthis regulation).

NOTE 2: During measurement of the fault loop impedance, it is necessary to establish a connection of negligibleimpedance between the neutral point of the system and the protective conductor preferably at the origin ofthe installation or, where this is not acceptable, at the point of measurement.

2.3.9 Earth fault loop impedance

Where protective measures are used which require knowledge of earth fault loop impedance, therelevant impedances shall be measured, or determined by an alternative method.

NOTE: Further information on measurement of earth fault loop impedance can be found in Appendix 2.

2.3.10 Additional protection

The verification of the effectiveness of the measures applied for additional protection is fulfilledby visual inspection and test. Where RCDs are required for additional protection, theeffectiveness of automatic disconnection of supply by RCDs shall be verified using suitable testequipment according to IEC 61557-6 (see 2.3.1) to confirm that the relevant requirements inChapter 4 of DZS 791 Part 2 are met.

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2.3.11 Prospective fault current

The prospective short-circuit current and prospective earth fault current shall be measured,calculated or determined by another method, at the origin and at other relevant points in theinstallation.

2.3.12 Check of phase sequence

For multiphase circuits, it shall be verified that the phase sequence is maintained.

2.3.13 Functional testing

2.3.13.1 Where fault protection and/or additional protection is to be provided by an RCD, theeffectiveness of any test facility incorporated in the device shall be verified.

2.3.13.2 Equipment, such as switchgear and controlgear assemblies, drives, controls andinterlocks, shall be subjected to a functional test to show that it is properly mounted, adjusted andinstalled in accordance with the relevant requirements of these Rules.

2.3.14 Verification of voltage drop

Where required to verify compliance with Section 3.7 of DZS 791 Part 2, the Following optionsmay be used:

i). The voltage drop may be evaluated by measuring the circuit impedanceii). The voltage drop may be evaluated by using calculations, for example, by diagrams or

graphs showing maximum cable length versus load current for different conductor cross-sectional areas with different percentage voltage drops for specific nominal voltages,conductor temperatures and wiring systems.

NOTE: Verification of voltage drop is not normally required during initial verification.

3. PERIODIC INSPECTION AND TESTING

3.1 General

3.1.1 Where required, periodic inspection and testing of every electrical installation shall becarried out in accordance with 2.3.2 to 5 in order to determine, so far as is reasonablypracticable, whether the installation is in a satisfactory condition for continued service. Whereverpossible, the documentation arising from the initial certification and any previous periodicinspection and testing shall be taken into account. Where no previous documentation is available,investigation of the electrical installation shall be undertaken prior to carrying out the periodicinspection and testing.

3.1.2 Periodic inspection comprising a detailed examination of the installation shall be carriedout without dismantling, or with partial dismantling as required, supplemented by appropriate

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tests from Chapter 2 to show that the requirements for disconnection times, as set out in Chapter4 of DZS 791 Part 2 for protective devices, are complied with, to provide for:i). safety of persons and livestock against the effects of electric shock and burnsii). protection against damage to property by fire and heat arising from an installation defectiii). confirmation that the installation is not damaged or deteriorated so as to impair safetyiv). the identification of installation defects and departures from the requirements of these

Regulations that may give rise to danger.

NOTE: A generic list of examples of items requiring inspection is given in Appendix 3.

3.1.3 Precautions shall be taken to ensure that the periodic inspection and testing shall notcause danger to persons or livestock and shall not cause damage to property and equipment evenif the circuit is defective.

Measuring instruments and monitoring equipment and methods shall be chosen in accordancewith relevant parts of IEC 61557. If other measuring equipment is used, it shall provide no lessdegree of performance and safety.

3.1.4 The extent and results of the periodic inspection and testing of an installation, or any partof an installation, shall be recorded.

3.1.5 Periodic inspection and testing shall be undertaken by a competent person.

3.2 Frequency of Inspection and Testing

3.2.1 The frequency of periodic inspection and testing of an installation shall be determinedhaving regard to the type of installation and equipment., its use and operation, the frequency andquality of maintenance and the external influences to which it is subjected. The results andrecommendations of the previous report, if any, shall be taken into account.

3.2.1 In the case of an installation under an effective management system for preventivemaintenance in normal use, periodic inspection and testing may be replaced by an adequateregime of continuous monitoring and maintenance of the installation and all its constituentequipment by skilled persons, competent in such work. Appropriate records shall be kept.

4. CERTIFICATION AND REPORTING

4.1 General

4.1.1 Upon completion of the verification of a new installation or changes to an existinginstallation, an Electrical Installation Certificate, based on the model given in Appendix 3, shallbe provided. Such documentation shall include details of the extent of the installation covered bythe Certificate, together with a record of the inspection, the results of testing and arecommendation for the interval until the first periodic inspection.

4.1.2 Upon completion of the periodic inspection and testing of an existing installation, anElectrical Installation Condition Report, based on the model given in Appendix 3, shall be

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provided. Such documentation shall include details of the extent of the installation andlimitations of the inspection and testing covered by the Report, together with records ofinspection, the results of testing and a recommendation for the interval until the next periodicinspection.

4.1.3 Where minor electrical installation work does not include the provision of a new circuit, aMinor Electrical Installation Works Certificate, based on the model given in Appendix 3, maybe provided for each circuit altered or extended as an alternative to an Electrical InstallationCertificate.

4.1.4 Electrical Installation Certificates, Electrical Installation Condition Reports and MinorElectrical Installation Works Certificates shall be compiled and signed or otherwiseauthenticated by a competent person or persons.

4.1.5 Electrical Installation Certificates, Electrical Installation Condition Reports and MinorElectrical lnstallation Works Certificates may be produced in any durable medium, includingwritten and electronic media. Regardless of the media used for original certificates, reports ortheir copies, their authenticity and integrity shall be verified by a reliable process or method. Theprocess or method shall also verify that any copy is a true copy of the original.

4.2 Initial Verification

4.2.1 Following the initial verification required by Chapter 2, an Electrical InstallationCertificate, together with schedules of inspection and schedules of test results, shall be given tothe person ordering the work. These schedules shall be based on the models given in Appendix 3.

4.2.2 The schedule of test results shall identify every circuit, including its related protectivedevice(s), and shall record the results of the appropriate tests and measurements detailed inChapter 2.

4.2.3 The person or persons responsible for the design, construction, inspection and testing of theinstallation shall, as appropriate, give to the person ordering the work a Certificate which takesaccount of their respective responsibilities for the safety of that installation, together with theschedules described in 4.2.1.

4.2.4 Defects or omissions revealed during inspection and testing of the installation workcovered by the Certificate shall be made good before the Certificate is issued.

4.3 Additions and Alterations

4.3.1 The requirements of Sections 4.1 and 4.2 for the issue of an Electrical InstallationCertificate or a Minor Electrical Installation Works Certificate shall apply to all the work of theadditions or alterations.

4.3.2 The contractor or other person responsible for the new work, or a person authorized to acton their behalf, shall record on the Electrical Installation Certificate or the Minor ElectricalInstallation Works Certificate, any defects found, so far as is reasonably practicable, in theexisting installation.

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4.4 Periodic Inspection and Testing

4.4.1 Following the periodic inspection and testing described in Chapter 3, an ElectricalInstallation Condition Report, together with schedules of inspection and schedules of test results,shall he given by the person carrying out the inspection, or a person authorized to act on theirbehalf, to the person ordering the inspection. These schedules shall be based on the models givenin Appendix 3. The schedule of test results shall record the results of the appropriate testsrequired of Chapter 2.

4.4.2 Any damage, deterioration, defects, dangerous conditions and non-compliance with therequirements of the Regulations, which may give rise to danger, together with any significantlimitations of the inspection and testing, including their reasons, shall be recorded.

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Appendix 1 Methods for Measuring the Insulation Resistance/Impedance of Floors andWalls to Earth or to the Protective Conductor System

(Informative)

1. GENERAL

Measurement of impedance or resistance of insulating floors and walls should be carried out withthe system voltage to Earth and nominal frequency, or with a lower voltage of the same nominalfrequency combined with measurement of insulation resistance. This may be done, for example,in accordance with the following methods of measurement:

i). a.c. system

- by measurement with the nominal a.c. voltage, or

- by measurement with lower a.c. voltages (minimum 25 V) and, additionally, by aninsulation resistance test using a minimum test voltage of 500 V d.c. for nominalsystem voltages not exceeding 500 V and a minimum test voltage of 1000 V d.c. fornominal system voltages above 500 V.

The following optional voltage sources may be used:

a). The earthed system voltage (voltage to Earth) that exists at the measuring pointb). The secondary voltage or a double-wound transformerc). An independent voltage source at the nominal frequency of the system.

In options b) and c), the measuring voltage source is to be earthed for the measurement.

For safety reasons, when measuring voltages above 50 V, the maximum output current should belimited to 3.5 mA.

ii). d.c. system- insulation resistance test by using a minimum test voltage of 500 V d.c. for nominal

system voltages not exceeding 500 V- insulation resistance test by using a minimum test voltage of 1000 V d.c. for nominal

above 500 V.

The insulation resistance test should be made using measuring equipment in accordance with EN61557-2.

2. TEST METHOD FOR MEASURING THE IMPEDANCE OF FLOORS ANDWALLS WITH A.C. VOLTAGE

Current, I, is led through an ammeter to the test electrode from the output of the voltage sourceor from the line conductor L.The voltage (Ux) at the electrode to Earth or to the protective conductor is measured byvoltmeter with an internal resistance of at least 1 MΩ.

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The impedance of the floor insulation will then be: Zx= Ux

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The measurement for ascertaining the impedance is to be carried out at as many points asdeemed necessary selected at random, with a minimum of three. The test electrodes may beeither of the following types. In case of dispute, the use of test electrode 1 is the referencemethod.

3. TEST ELECTRODE 1

The electrode comprises a metallic tripod of which the parts resting on the floor form the pointsof an equilateral triangle. Each supporting point is provided with a flexible base ensuring, whenloaded, close contact with the surface being tested over an area of approximately 900 rnm2 andpresenting a resistance of less than 5000 Ω.

Before measurements are made, the surface being tested is cleaned with a cleaning fluid. Whilemeasurements are being made, a force of' approximately 750 N for floors or 250 N for walls isapplied to the tripod.

Figure A1-1 Test Electrode 1

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4. TEST ELECTRODE 2

The electrode comprises a square metallic plate with sides that measure 250 mm, and a square ofdamped, water-absorbent paper, or cloth, from which surplus water has been removed, with sidesthat measure approximately 270 mm. the paper is placed between the metal plate and the surfacebeing tested.

During measurement, a force of approximately 750 N for floors or 250 N for walls is applied onthe plate.

Figure A1-2 Test Electrode 2

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Appendix 2 Measurement of Earth Fault Loop Impedance: Consideration of the Increaseof the Resistance of Conductors with Increase of Temperature

(informative)

When impedance measurements arc made at ambient temperature the procedure hereinafterdescribed may be followed to take into account the increase or resistance or the conductors withthe increase or temperature due to load current, to verify, for TN and TT systems in whichprotection by automatic disconnection is provided by overcurrent devices, compliance of themeasured values or earth fault loop impedance with the appropriate requirements of rule 3.3.3 or3.3.5 of ZS 791 Part 2.

The requirements of 3.3.3 or 3.3.5 of ZS 791 Part 2 as appropriate are considered to be met whenthe measured value or earth fault loop impedance satisfies the following equation:

Zs(m) ≤ 0.8×U0

Iawhere:

Zs (m) is the measured impedance or the earth fault current loop up to the most distant point orthe relevant circuit from the origin or the installation (Ω)

U0 is the nominal a.c. r.m.s line voltage to earth (V)

Ia is the is the current causing the automatic operation or the protective device within the timestaled in Table 3-1 of ZS 791 Part 2 or within 5 s according to the conditions stated in 3.3.3.2.3of ZS 791 Part 2).

Where the measured value or the earth fault loop impedance exceeds 0.8 U0/Ia, a more preciseassessment of compliance with 3.3.4.5 or 3.3.5.4 of ZS 791 Part 2 as appropriate may be made,evaluating the value of the earth fault loop impedance according to the following procedure:

i). The line conductor to protective conductor loop impedance or the supply is first measuredat the origin of the installation

ii). The resistances of the line conductor and protective conductor of the distribution circuit(s)are then measured

iii). The resistances of the line conductor and protective conductor of the final circuit are thenmeasured

iv). The values of resistance measured in accordance with (ii) and (iii) are increased on thebasis of the increase of conductor temperature, taking into consideration the design current,Ib.

v). The values of resistance increased in accordance with (iv) are finally added to the valuemeasured at (i) to obtain a realistic value of Zs under earth fault conditions.

NOTE: Other methods are not precluded.

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Appendix 3 Model Forms for Certification and Reporting(Informative)

Introduction

i). The Electrical Installation Certificate required by Part 6 should be made out and signed orotherwise authenticated by a competent person or persons in respect of the design,construction, inspection and testing of the work.

ii). The Minor Works Certificate required by Part 6 should he made out and signed orotherwise authenticated by a competent person In respect of the design, construction,inspection and testing of the minor work.

iii). The Electrical Installation Condition Report required by Part 6, should he made out andsigned or otherwise authenticated by a competent person in respect of the inspection andtesting of an installation.

iv). Competent persons will. as appropriate to their function under ( i) (ii) and (iii) above havea sound knowledge and experience relevant to the nature of the work undertaken and to thetechnical standards set down in these Regulations be fully versed in the inspection andtesting procedures contained in these Regulations and employ adequate testing equipment.

Where design, construction, inspection and testing are the responsibility of one person aCertificate with a single-signature declaration in the form shown below may replace the multiplesignatures section of the model form.

Electrical Installation Certificates will indicate the responsibility for design, construction,inspection and testing, whether in relation to new work or further work on an existinginstallation.

FOR DESIGN, CONSTRUCTION, INSPECTION & TESTINGI, being the person responsible for the Design, Construction, Inspection & Testing of theelectrical installation (as indicated by my signature below), particulars of which aredescribed above, having exercised reasonable skill and care when carrying out the Design,Construction, Inspection & Testing, hereby CERTI FY that the said work for which I havebeen responsible is to the best of my knowledge and belief in accordance with ZS 791,amended to ………… (date) except for the departures, if any, detailed as follows.

v). A Minor Works Certificate will indicate the responsibility for design, construction.inspection and testing of the work described on the certificate,

vi). An Electrical Installation Condition Report will indicate the responsibility for theinspection and testing of an existing installation within the extent and limitations specifiedon the report.

vii). Schedules of inspection and schedules of test results as required by Part 6 should he issuedwith the associated Electrical Installation Certificate or Electrical Installation ConditionReport.

viii). When making out and signing a form on behalf of a company or other business entity,individuals should state for whom they are acting.

ix). Additional forms may be required as clarification if needed by ordinary persons or inexpansion, for larger or more complex installations.

x). The IET Guidance Note 3 provides further information on inspection and testing and forperiodic inspection, testing and reporting.

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ELECTRICAL INSTALLATION CERTIFICATE(REQUIREMENTS FOR ELECTRICAL INSPECTIONS – ZS 791)

DETAILS OF THE CLIENT:…………………………………………………………………………………

INSTALLATION ADDRESS:…………………………………………………………………………………

DESCRIPTION OF THE INSTALLATION Tick boxes as appropriate

Description of installation:

Extent of installation covered by this Certificate:

(Use continuation sheet if necessary) see continuation sheet No:….

New installation

Addition to an existinginstallation

Alteration to an existinginstallation

FOR DESIGNI/We being the person(s) responsible for the design of the electrical installation (as indicated by my/our signatures below),particular of which are described above, having exercised reasonable skill and care when carrying out the design hereby Certifythat the design work for which I/ we have been responsible is to the best of my/ our knowledge and belief in accordance with ZS791 amended to …………….. (date), exceptt for departures, if any, detailed as follows:Details of departures from ZS 791:

The extent of liability of the signatory (ies) is limited to the work described above as the subject of this Certifcate.For the DESIGN of the installation: ** (Where there is mutual responsibility for the design)

Signature: ………………….. Date: ……… Name (IN BLOCK LETTERS): ………………Designer No.1

Signature: ………………….. Date: ……… Name (IN BLOCK LETTERS): ………………Designer No.2**FOR CONSTRUCTIONI/We being the person(s) responsible for the construction of the electrical installation (as indicated by my/our signatures below),particular of which are described above, having exercised reasonable skill and care when carrying out the construction herebyCertify that the construction work for which I/ we have been responsible is to the best of my/ our knowledge and belief inaccordance with ZS 791 amended to …………….. (date), except for departures, if any, detailed as follows:Details of departures from ZS 791:

The extent of liability of the signatory (ies) is limited to the work described above as the subject of this Certifcate.For the CONSTRUCTION of the installation:

Signature: ………………….. Date: ……… Name (IN BLOCK LETTERS): ………………ConstructorFOR INSPECTION & TESTINGI/We being the person(s) responsible for the inspection and testing of the electrical installation (as indicated by my/our signaturesbelow), particular of which are described above, having exercised reasonable skill and care when carrying out the inspection andtesting hereby Certify that the work for which I/ we have been responsible is to the best of my/ our knowledge and belief inaccordance with ZS 791 amended to …………….. (date), except for departures, if any, detailed as follows:Details of departures from ZS 791:

The extent of liability of the signatory is limited to the work described above as the subject of this Certificate.For the INSPECTION & TESTING of the installation:

Signature: ………………….. Date: ……… Name (IN BLOCK LETTERS): ………………ConstructorNEXT INSPECTIONI/We the designer(s) recommend that this installation is further inspected aand tested afetr an inetrval of not more than …… years/months.

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PARTICULARS OF SIGNATORIES TO THE ELECTRICAL INSTALLATION CERTIFICATEDesigner (No.1)Name: ……………………………………………. Company: …………………………………Address: …………………………………………………………………………………………..Postcode: ……………………………………….... Tel No.: .…………………………………..Designer (No.2)Name: ……………………………………………. Company: …………………………………Address: …………………………………………………………………………………………..Postcode: ……………………………………….... Tel No.: .…………………………………..SUPPLY CHARACTERISTICS AND EARTHING ARRANGEMENTS Tick boxes and enter details as appropriate

Earthingarrangements

Number and Type of LiveConductors

Nature of Supply Parameters

Nominal voltage, U/U0 ……….V

Nominal frequency, f ………...Hz

Prospective fault current, Ipf ..kA

External loop impedance, Ze …Ω

Supply ProtectiveDevice

Characteristics

Type: ……………

Rated current …A

TN-C a.c d.cTN-S

1-phase, 2-wire 2-wireTN-C-STT

2-phase, 3-wire 3-wireITOther sourcesof supply (tobe detailed onattached schedule)

3-phase, 3-wire 3-wire

3-phase, 4-wire other

PARTICULARS OF INSTALLATION REFERRED TO IN THE CERTIFICATEMeans of Earthing

Distributor’sFacility

InstallationEarth Electrode

Maximum DemandMaximum demand (load) ……………… kVA/ Amps Delete as appropriate

Details of Installation Earth Electrode (where applicable)Type Location Electrode resistance to Earth

(e.g. rod(s), tape etc)………………………… ………………….. ………………………………

Main Protective Conductors

Earthing conductor: material ……………… csa …………..mm2 Continuity and connection verified

Main protectivebonding conductor

material ……………… csa …………..mm2 Continuity and connection verified

To incoming water and/or gas service To other elements: ……………………………………Main switch or circuit breaker

Type and No. of poles ………………….. Current rating ……… A Voltage rating …… V

Location ………………………………... Fuse rating or setting ……. A

Rated residual operating current I∆n = …..mA, and operating time of …..ms (at I∆n)

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ELECTRICAL INSTALLATION CERTIFICATE NOTES:

1. The Electrical Installation Certificate is to be used only for the initial certification of a newinstallation for an addition or alteration to an existing installation where new circuits havebeen introduced.

It is not to be used to fix a Periodic Inspection for which an Electrical InstallationCondition Report form should be used. For an addition or alteration which does not extendto the introduction of new circuits, Minor Electrical Installation Works Certificate may beused.

The "original" Certificate is to be given to the person ordering the work. A duplicateshould be retained by the contractor.

2. This Certificate is only valid if accompanied by the Schedule of Inspections and theSchedules of Test Results

3. The signatures appended arc those of the persons authorized by the companies executingthe work design, construction, inspection and testing respectively. A signatory authorizedto certify one category of work should sign in each of the appropriate places.

4. The time interval recommended before the first periodic inspection must be inserted (seeIET Guidance Note 3 for guidance).

5. The page numbers for each of the Schedules of Test Results should be indicated togetherwith the total number of sheets involved.

6. The maximum prospective value of fault current (Ipf) recorded should be the greater ofeither the prospective value of short-circuit current or the prospective value of earth faultcurrent.

7. The proposed date for the next inspection should take into consideration the frequency andquality maintenance that the installation can reasonably be expected to receive during itsintended life, and period should be agreed between the designer, installer and otherrelevant parties.

ELECTRICAL INSTALLATION CERTIFICATEGUIDANCE FOR RECIPIENTS (to be appended to the Certificate)

This safety Certificate has been issued to confirm that the electrical installation work to which itrelates has been designed, constructed, inspected and tested in accordance with ZS 791.

You should have received an "original" Certificate and the contractor should have retained aduplicate. If you were the person ordering the work, but not the owner of the installation, youshould pass this Certificate or a full copy it including the schedules immediately to the owner.

The "original" Certificate should be retained in a safe place and be shown to any personinspecting or undertaking further work on the electrical installation in the future. If you later

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vacate the property, this Certificate will demonstrate to the new owner that the electricalinstallation complied with the requirements of ZS 791 at the time the Certificate was issued.

For safety reasons, the electrical installation will need to be inspected at appropriate intervals bya competent person. The maximum time interval recommended before the next inspection isstated on Page 1 under INSPECTION".

This Certificate is intended to be issued only for a new electrical installation or for new workassociated with addition or alteration to an existing installation. It should not have been issuedfor the inspection of an existing electrical installation. An "Electrical Installation ConditionReport" should be issued for such an inspection.

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MINOR ELECTRICAL INSTALLATION WORKS CERTIFICATE(REQUIREMENTS FOR ELECTRICAL INSTALLATIONSTo be used only for minor electrical work which does not include the provision of a new circuit

PART 1: Description of minor works1. Description of the minor works2. Location/ Address3. Date minor works completed4. Details of departure if any from ZS 791

PART 2: Installation Details1. System earthing arrangement TN-C-S TN-S TT2. Method of fault protection3. Protective device for the modified circuit Type …………… Rating …………. AComments on existing installation, including adequacy of earthing and bonding arrangements

PART 3: Essential TestsEarth continuity satisfactory

Insulation resistance:Line/ neutral ………………MΩLine/ earth ………………MΩNeutral/ earth ……………..MΩ

Earth fault loop impedance ………………………ΩPolarity satisfactoryRCD operation (if applicable). Rated residual operating current I∆n …….mA and operating timeof …………. ms (at I∆n)PART 4: DeclarationI/We CERTIFY that the said works do not impair the safety of the existing installation, that thesaid works have been designed, constructed, inspected and tested in accordance with ZS 791amended to …………….. (date) and that the said works, to the best of my/ our knwoledge andbelief, at the time of the inspection, complied with ZS 791 except as detailed in Part 1 above.Name: ……………………………..For and behalf of: …………………………Address: ……………………………………..…………………………………………………

Signature: …………………………………Position: …………………………………

Date: ………………………………………

MINOR ELECTRICAL INSTALLATION WORKS CERTIFICATE NOTES:The Minor Works Certificate is intended to be used for additions and alterations to an installationthat do not extend to the provision of a new circuit. Examples include the addition or socket-outlets or lighting points to an existing circuit, the relocation of a light switch etc. ThisCertificate may also be used for the replacement of equipment such as accessories or luminaires,but not for the replacement or distribution boards or similar items. Appropriate inspection andtesting, however, should always be carried out irrespective of the extent of the work undertaken.

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MINOR ELECTRICAL INSTALLATION WORKS CERTIFICATE GUIDANCE FORRECIPIENTS (to be appended to the Certificate)This Certificate has been issued to confirm that the electrical installation work to which it relateshas been designed, constructed, inspected and tested in accordance with ZS 791.You should have received an "original" Certificate and the contractor should have retained aduplicate. If you were the person ordering the work, but not the owner of the installation, youshould pass this Certificate or a copy of it to the owner. A separate Certificate should have beenreceived for each existing circuit on which minor works have been carried out. This Certificate isnot appropriate if you requested the contractor to undertake more extensive installation work forwhich you should have received an Electrical Installation Certificate.

The Certificate should he retained in a safe place and he shown to any person inspecting orundertaking further work on the electrical installation in the future. if you later vacate theproperty, this Certificate will demonstrate to the new owner that the minor electrical installationwork carried out complied with the requirements of ZS 791 at the time the Certificate wasissued.

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CONDITION REPORTNotes for the person producing the Report:

This Report should only be used for reporting on the condition of an existing electricalinstallation, installation which was designed to an earlier edition of the Regulations and whichdocs not fully comply with the current edition is not necessarily unsafe for continued use, orrequires upgrading. Only damage deterioration, defects, dangerous conditions and non-compliance with the requirements of the Regulations which may give rise to danger, should berecorded.

The Report, normally comprising at least six pages, should include schedules of both theinspection and the test results, Additional pages may be necessary for other than a simpleinstallation. The number of each page should be indicated, together with the total number ofpages involved.

The reason for producing this Report, such as change of occupancy or landlord's periodicmaintenance should be identified in Section B.

Those elements of the installation that arc covered b) the Report and those that are not should beidentified in Section D (Extent and limitations). These aspects should have been agreed with theperson ordering the report and other interested parties before the inspection and testingcommenced. Any operation limitations, such as inability to gain access to parts or the installationor an item or equipment should also be recorded in Section D.

The maximum prospective value of fault current (Ipf) recorded should be the greater of either theprospective value of short-circuit current or the prospective value of earth fault current.

Where an installation has an alternative source or supply a further schedule of supply earthingarrangements based upon Section I of this Report should be provided.

A summary of the condition of the installation in terms of safety should be clearly stated inSection E. Observations, if any, should be categorised in Section K using the coding C I to C3 asappropriate. An observation given a code C I or C2 c1assilicatilln should result in the overallcondition of the installation being reported as unsatisfactory.

Wherever practicable, items classified as 'Danger present' (C I) should be made safe ondiscovery. If this is not practical the owner or user should be given written notification as amatter of urgency.

Where an observation requires further investigation because the inspection has revealed anapparent; deficiency which could not owing to the extent or limitations of the inspection be fullyidentified. This should be indicated in the column headed "Further investigation required" withinSection K.

If the space available fix observations in Section K is insufficient, additional pages should beprovided as necessary.

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The date by which the next electrical Installation Condition Report is recommended should begiven in Section I:. The interval between inspections should take into account the type and usageor the installation and its overall condition.

CONDITION REPORT GUIDANCE FOR RECIPIENTS (to be appended to the Report)This Report is an important and valuable document which should be retained for futurereference.

The purpose of this Condition Report is to confirm so far as reasonably practicable, whether ornot the electrical installation is in a satisfactory condition for continued service (see Section E).The Report should identify any damage deterioration- defects and/or conditions which may giverise to danger (sec Section K).

The person ordering the Report should have received the "original" Report and the inspectorshould have retained a duplicate.

The "original" Report should be retained in a safe place and be made available to any personinspecting or undertaking work on the electrical installation in the future. I f the property isvacated. this Report will provide the new owner /occupier with details of the condition of theelectrical installation at the time the Report was issued.

Where the installation incorporates a residual current device (RCD) there should be a notice at ornear the device stating that it should be tested quarterly. For safety reasons it is important thatthis instruction is followed.

Section D (Extent and Limitations) should identify fully the extent of the installation covered bythis Report and any limitations on the inspection and testing. The inspector should have agreedthese aspects with the person ordering the Report and with other interested parties (licensingauthority, insurance company, mortgage provider and the like) before the inspection was carriedout.

Some operational limitations such as inability to gain access to parts of the installation or an itemof equipment may have been encountered during the inspection. The inspector should have notedthese in Section D.

For items classified in Section K as C I ("Danger present") the safety of those using theinstallation is at risk, and it is recommended that a competent person undertakes the necessaryremedial work immediately.

For items classified in Section K as C2 ("Potentially dangerous") the safety of those using theinstallation may be at risk and it is recommended that a competent person undertakes thenecessary remedial work as a matter of urgency.

Where it has been stated in Section K that an observation requires further investigation theinspection has revealed an apparent deficiency which could not due to the extent or limitations ofthe inspection be fully identified. Such observations should be investigated as soon as possible.Further examination of the installation will be necessary. To determine the nature and extent ofthe apparent deficiency (see Section F).

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For safety reasons, the electrical installation should be re-inspected at appropriate intervals by acompetent person. The recommended date by which the next inspection is due is stated inSection F or the Report under 'Recommendations' and on a label at or near to the consumer unit!distribution board.

CONDITION REPORT INSPECTION SCHEDULEGUIDANCE FOR THE INSPECTOR

Where inadequacies in the distributor's equipment arc encountered the inspector should advisethe person ordering the work to inform the appropriate authority.

Older installations designed prior to ZS 791 may not have been provided with RCDs foradditional protection. The absence of such protection should as a minimum be given a code C3classification (item 5.12).The schedule is not exhaustive.

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