6.5 Testing and fault-finding
6.5.1 General
6.5.2 Ensuring correct connections
6.5.1 General
When fault finding, testing, applying a potentially fatal test current19, or a combination of these, the common electrical hazards are likely to be present (refer to section 4.4). Consult section B.1 for information on the sources of these hazards. To control risks of this kind, a safe system of live work as outlined in section 6.3 must be in place.
Where a recognised test cannot or does not satisfactorily determine that parts are electrically safe – including proving that all connections are correct (including polarity) – or where any doubt exists, the following should apply:
- Ensure the electrical work or affected part of the electrical work is isolated, disconnected, and made safe; and
- Make sure the electrical work remains safely isolated until the matter is resolved. Resolution may take the form of further advice and assistance being received and acted on.
To ensure electrical safety, procedures for fault finding and testing should also address:
- Considering the characteristics of the tester/s to be used and any resultant effects, including technical limitations. For example, when choosing a voltage indicating device to test at a low voltage switchboard, an appropriate class of device with an appropriate internal impedance will ensure accurate and valid tests while maintaining electrical safety by not introducing hazardous currents and potentials into the earthing system;
- Proving the correct operation of testing devices, both before and after each test. If a test procedure is interrupted, the sequence of testing and confirmation should be restarted;
- Giving clear instruction on what is seen as a conclusive test eg what constitutes correct connections (including polarity); and
- Providing clear instruction on what is regarded as an inconclusive test.
If the procedure includes a requirement for inspections, the criteria for the inspections should be clearly identified.
Where more than one electrical worker is involved in the process of installing, testing, energising, disconnecting and rectifying, an employer or self-employed person should ensure that an electrical worker is assigned to ensuring electrical safety is maintained at all times.
An employer or self employed person should make sure a person is clearly responsible for the overall integrity of the electrical work and testing.
Electrical workers should be regularly trained and assessed in the underpinning knowledge and practical aspects of testing across the range of variables the worker will encounter.
Clear guidelines should be provided on which tester, or combination of test instruments and equipment, to use including accessories such as trailing earth leads.
6.5.2 Ensuring correct connections (including polarity)
6.5.2.1 Importance of testing for correct connections (including polarity)
Failure to ensure correct connections (including polarity) can cause serious incidents and may result in severe and even fatal injuries. Examples of hazardous situations resulting from incorrect connections (including polarity) include:
- Transposing an active and neutral, or an open circuit neutral connection, resulting in exposed conductive parts of an installation becoming energised. In this situation, dangerous potentials are created between metal work, such as taps and sinks, and earth; and
- On the low voltage distribution network – bonding a phase to earth instead of bonding the neutral to earth, thus causing dangerous step and touch potentials at the base of a pole.
When an active and neutral are transposed in a Multiple Earthed Neutral (MEN) system, the earthed metal work, such as taps, become live, i.e. there is a significant potential to earth. An error of this kind will usually mean the supply cannot be isolated to an installation via the main switch. In this instance, the problem arises because the main switch is in the neutral and at least one active is not switched.
Connections must be tested to confirm that they are correct. The tests must be performed when any new work is energised. The same applies to any alterations or additions, or both. Testing to prove correct connections (including polarity) greatly reduces the risk of death or severe injury associated with incorrect connections (including polarity).
Using the correct test procedures will ensure the electrical work is safe and will protect the worker, other workers and the public during and after testing.
6.5.2.2 Situations when testing correct connections (including polarity) are required
Examples of when tests of correct connections (including polarity) are required include when:
- Electrical installation or repair work is connected to supply;
- Items of electrical equipment, such as stoves and hot water systems, are connected to supply;
- Consumers’ mains or sub mains have been repaired or replaced;
- New consumers’ mains or sub mains are installed;
- Low voltage bridges are connected or reconnected on low voltage mains;
- Connections to transformers or generators are made or remade;
- Service connections to street light standards are made, remade or altered;
- A new low voltage service is installed;
- An existing service is disconnected20 or reconnected; or
- A distribution system is initially energised or when any addition or alteration to the system could affect electrical safety.
6.5.2.3 Procedure for ensuring correct connections (including polarity)
Test procedures should be properly documented and effectively communicated to the appropriate persons.
The minimum steps should include proving the correct electrical relationship exists between the:
- Active/s;
- Neutral;
- Earthing, bonding conductors or both; and
- Independent earth used for testing.
Both the source of supply and the electrical work may require testing. For example, if a three-phase generator is to supply an installation, the source – in this instance, the generator – and the installation require testing because incorrect connection/s may exist at either or both locations.
The electrical worker responsible for ensuring correct connections (including polarity) must be competent in confirming connections are correct.
6.5.2.4 Precautions when testing for correct connections (including polarity)
It is not acceptable to rely on equipment function as a means of testing connections. Examples of unacceptable test methods include:
- Relying on motor or meter rotation or both as a reliable test; or
- Assuming that because a protective device has not operated, the connections are correct.
Within the test procedure, an indication should be given as to what the test is proving. The electrical worker following the procedure should be able to clearly identify exactly what he or she is testing for. For example, is the test purely a ‘polarity’ test or does it include other measures such as proving that there is no alternative source of supply?
Installations should not be connected to de-engergised low voltage sources. The installation earthing system should not be used for tests to earth unless the insulation between the neutral and earthing system has been proven acceptable. An independent earth may be used. The installation earthing should not be used because, as the test is performed, the potential of the earthing system may rise to a level that causes an electrical hazard. In this situation, the impedance of the testing device directly affects the level of potential rise.
19 The term "potentially fatal test current" is defined in Appendix A.
20 The term "disconnected" is defined in Appendix A.
Last updated July 16, 2009
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