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The objective of periodic examination, inspection and testing is to ensure that work places and equipment are safe, in efficient working order and in a good state of repair.  Not all defects can be identified by inspection, it is necessary to carry out tests on parts of the installation, particularly on earth fault paths and electrical protection systems, to ensure that equipment will be safe.  


Maintenance of electrical equipment is necessary to ensure safety and for the prevention of loss. The degree of maintenance will depend on many factors such as condition, age, safety, duty of equipment, potential loss etc. It is necessary to have a comprehensive preventative maintenance system that includes periodic examination, inspection and where appropriate testing to ensure safety and productivity are maintained.


Low voltage systems.

The written scheme of examination, maintenance, inspection and testing required by the Quarries Regulations 1999 should be in line with the requirements of the current version of BS7671, Requirements for Electrical Installations. With a proviso that operators should select the frequencies following an assessment of the risks at the site. For guidance purposes the table shown in section 7.1.1 shows the recommended frequencies to be used. Where Specialist testing and inspection companies or electrical contractors carry out the work it is important that the operator states what will be done rather than let others decide on what will ultimately be the operator’s responsibility. When inspection and testing has been completed an electrical inspection report must be issued to the site that is in line with the requirements of the current version of BS7671.

Frequencies of Inspection and Test.

The following table gives guidance on the frequency of inspections and tests of an electrical installation (including mobile equipment and machinery).


Note: - When R2 tests are carried out at least one earth loop impedance must be measured per distribution transformer or incoming mains supply to verify the results.


Defect rectification. 

Operators should have, as part of the inspection and test system, a means of ensuring defects are remedied in an appropriate time scale.  The defect action report should be included in the health and safety document.


The operator should agree a specification for the inspection and tests setting out what must be done, the reporting procedures and action necessary if equipment is found to be a source of immediate danger.


As defined in the current version of BS7671, Requirements for Electrical Installations, defects reported from an inspection are split into 3 categories as follows.




Code 1 Which are defined in the current version of BS7671 as.


  •      Danger present. Risk of injury. Immediate remedial action required
  •      This code is attributed to defects that cannot be left and is suggested that they are rectified immediately or possibly isolated. Examples of this would be bare exposed live parts or badly damaged equipment.
  •      Where it is not possible to rectify the defects immediately they shall be rectified as soon as possible in line with an assessment of the risks and after consultation with the responsible electrical person. Additional controls may be required to permit short term use


Code 2 Which are defined in the current version of BS7671 as.


  •      Potentially dangerous – urgent remedial action required
  •      This code is attributed to defects that whilst urgent do not require immediate action. Examples of this include undersized cables, high earth loop impedance that prevents the protective device tripping in accordance with this standard or the current version of BS7671, low insulation readings 
  •      They shall be considered as requiring urgent action to rectify the defects. The defects should be rectified within one month. Where it is not possible to complete matters within one month, they shall be completed as soon as possible in line with the assessment of risks.


Code 3 Which are defined in the current version of BS7671 as.


  •     Improvement required. 
  •     This code is attributed to defects that are not directly safety related but which are non-compliance with the requirements of this guidance or the current version of BS767. Examples of this are absence of diagrams, Absence of an RCD where one is required
  •     These defects can be used to identify areas or equipment where improvements can be made both to the installation.


F1 Which are defined in the current version of BS7671 as.

  •      Further investigation required without delay
  •     This code is attributed where the inspection has revealed an apparent deficiency that could not, due to the limitations or extent of the inspection, be fully identified.
  •     Further investigation might reveal a C1 or C2 defect for example unable to verify the supply characteristics, unable to verify the protective device will effectively protect the circuit due to the age of the device or no information on it.


Portable appliances

With regard to portable appliance testing there are no set frequencies of inspection and test, but guidance can be found in HSE publication HSG107 Maintaining portable electrical equipment and IET COP for in- service inspection and testing of electrical equipment current edition.


High voltage systems

The purpose of inspection, maintenance and testing of a high voltage electrical installation is to assess its actual condition at the time of the inspection and to assess whether for a period up to the next inspection it will not be a source of danger if it is properly used and maintained during that period. The types of inspection include.


  •     Routine visual inspection and
  •     Thorough visual inspection and test including maintenance and
  •     Noninvasive maintenance such as partial discharge testing.


All inspections, maintenance and tests should be carried out by a competent person.


For guidance purposes the table shown in section 7.2.3 shows the recommended frequencies to be used. 


Routine visual inspection

This comprises of an inspection of the external parts of the installation to determine its general condition and is carried out at intervals between the thorough inspection and maintenance.     


Thorough inspection and maintenance including testing

This comprises of the inspection, maintenance and testing of the external and internal parts of the installation and equipment to determine its condition and whether or not the equipment is safe for continuous use.


Due the many different types of high voltage equipment in service it would not be feasible to list all of the checks required in this guidance document, therefore the inspections, maintenance and testing of high voltage systems should be carried out in accordance with the following guidance.

  •       Manufacturer’s guidelines where available
  •       HSE publication HSG230 Keeping Electrical Switchgear Safe. 
  •       The current version of British standard BS 6626: mmaintenance of electrical switchgear and control gear for voltages above 1 kV and up to and including 36 kV – Code of Practice.
  •       Maintenance of high voltage equipment shall also include any work required as a result of a notification by the Energy Networks Association fault reporting system.


Frequencies of Inspection maintenance and test

The following table gives guidance on the frequency of inspections and tests of an electrical installation (including mobile equipment and machinery).



Defect Rectification

As with the low voltage defects there is no set guidance on defect coding and rectification on high voltage systems. Where defects are found on high voltage equipment these should be rectified in accordance with guidance from the competent person carrying out the inspections and maintenance or where possible Energy Network Association may also be used for information on high voltage equipment faults as further guidance on rectifying defects.


Record, plans and information.

The following information should be kept on site as part of the management of electrical installations and systems. 


  •     Underground and overhead site service plans
  •     Installation test certificates high and low voltage
  •     High voltage inspection and maintenance records
  •     Low voltage inspection and test records (electrical installation condition report)
  •     Portable appliance test records
  •     RCD test records
  •     Emergency stop / safety interlock test records
  •     Defect rectification records for all inspections and tests
  •     Distribution line diagrams low and high voltage
  •       Motor control circuit diagrams
  •       Operating and instruction manuals for equipment
  •       Arc Flash assessments
  •       Earth spike/nest test results