Basic Procedure of Using Electrical Test Instrument and Safe Isolation Practices


Electrical Testing

It is important for professional electricians to know the proper procedure in using electrical test instruments. These includes the proper selection of test probes, voltage indicating devices and the actual measuring device. This is because it has been proven from the past that there are several instances where the electrical accidents involves misuse of electrical test instruments. For this reason, many manufacturers enhanced the safety features of the test instruments sold in the market. 

The test probes 

  1. The probes must have finger barriers or be shaped so that the hand or fingers cannot make contact with the live conductors under test. 
  2. The probe tip must not protrude more than 2 mm, and preferably only 1 mm, be spring-loaded and screened. 
  3. The lead must be adequately insulated and colored so that one lead is readily distinguished from the other. 
  4. The lead must be flexible and sufficiently robust. 
  5. The lead must be long enough to serve its purpose but not too long. 
  6. The lead must not have accessible exposed conductors even if it becomes detached from the probe or from the instrument. 
  7. Where the leads are to be used in conjunction with a voltage detector they must be protected by a fuse. 

Doing Live Testing

Safety standard recommends that testing must be done while the circuit is dead. In case of fault finding, the first thing to do is to remove the individual components in the circuit and perform individual testing. However, there are instances where an electrician needs to perform the live testing.  In case that the live testing is inevitable, the person who will carry out the test must observe the following:
  1. Be trained so that he understands the equipment and the potential hazards of working live and can, therefore, be deemed to be ‘competent’ to carry out the activity; 
  2. only use approved test equipment; 
  3. set up barriers and warning notices so that the work activity does not create a situation dangerous to others.

Electrical Supply Isolation

Safety standards are very specific in providing procedure to guide professional electricians in doing isolation of electrical supply. The isolation of electrical supply means the separation and disconnection of electrical components from all sources of electrical energy. This must be done in such a way that the separation and disconnection is secure. To isolate an individual circuit, the electrical worker needs to follow the chart below. 

Actual Test Procedure

  1. The circuits must be isolated using a ‘safe isolation procedure’, such as that described below, before beginning to test. 
  2. All test equipment must be ‘approved’ and connected to the test circuits by recommended test probes mentioned above. The test equipment used must also be ‘proved’ on a known supply or by means of a proving unit. 
  3. Isolation devices must be ‘secured’ in the ‘off’ position.
  4. Warning notices must be posted. 
  5. All relevant safety and functional tests must be completed before restoring the supply. 

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