6.7 Approval of Electrical Test Equipment & Tools
There needs to be control via a formal approvals process for all electrical test equipment, insulated tools, locks, labels, insulating tools, matting, shrouding and electrical PPE. This will require control over all such equipment on site and also equipment used by contractors. Incorrect test equipment is frequently used by the incorrect individuals and/or incorrect circumstances. For instance, there are often concerns as to the suitability of instruments to verify that circuits are dead. Engineers (including multi-skilled engineers who may or may not have electrical qualifications) use the voltage setting of digital multi-meters for testing for dead. The leads are often unfused, and this does not comply with the expectations of the enforcing authorities or guidance. Many times, multi-meters and leads that I inspect are not rated correctly for over voltage protection and had excessive visible tips on the probes. A very good reference on the subject is available as a free download from https://www.hse.gov.uk/ called Guidance Note GS38 (Fourth edition) on electrical test equipment for use on low voltage electrical systems. A suggested structure for the approval of tools and equipment is as follows.
Generic List. Create a generic approval list which will give standards to which all equipment shall be built. A generic list provides a specification for equipment where external contractors will be able to check their own equipment to ensure compliance with company standards.
Specific List. The next stage is to formulate a data base of specific list for equipment which is purchased by the company. Specific lists will describe the equipment, model number, manufacturer/supplier and other relevant information.
New Equipment. Next, create a process for the approval of new equipment so that items not listed on the specific list can be properly considered and control of equipment coming onto site is assured.
Specialised and Hired in Equipment. Finally, a process for specialised or hired in equipment, for example highly specialised for a particular task, such as harmonics monitoring equipment can be given a temporary approval by the site duty holder.
Maintenance and Calibration. Users must ensure that all specialist equipment is in good condition and correctly maintained and where necessary calibrated in accordance with the manufacturer’s requirements.
PPE, Safety signs and Labels. Specialist electrical personal protective equipment such as shock and arc flash protection, approved safety signs and labels such as danger & caution notices and field marking labels should have a record kept in the specific list. The labels should include an image and approximate dimensions.
Audits. All equipment covered under the approval of tools and equipment should be audited on a regular basis, to ensure that it complies with the approved list of equipment. Any equipment that does not comply should be removed and destroyed.
6.8 Thermography and Partial Discharge Testing
Thermal imaging and partial discharge testing are classed as condition monitoring to detect impending failure in components and connections. This necessitates that the equipment is monitored in service and energised. Both techniques require some specialism particularly in the interpretation of results. Insurance companies sometimes provide discounts for companies that undertake thermal imaging mainly to reduce the risk of losses through electrical fires. Other insurance companies will insist on measures such as thermography. In addition, discovery of faulty joints or contacts could prevent overheating/arcing that could lead to a dangerous arc flash.
Can the procedures be carried out safely? The answer is yes, providing that a risk assessment which explores the alternatives has been properly implemented. As far as arc flash risk is concerned, this necessitates the predictive techniques always with a goal of prevention as first choice.
Thermal imaging requires that panel doors need to be opened in order to get accurate measurements. Sometimes internal shrouding may interfere with the thermographic images and I have come across situations where individuals may resort to the removal of shrouding. This obviously gives an extra order of risk to the operation and needs very careful consideration by the electrical duty holder. Among the alternatives to the opening of panel doors onto energised equipment there are:
- Viewing windows which are mounted in the panel doors. These allow thermal imaging to occur without opening doors onto energised conductors.
- Ductor testing which uses a high current digital micro-ohmmeter to measure very low resistances in circuit breakers contact resistance and joints in switchgear and busbar systems.
- Joint inspection and tightening regimes as part of routine maintenance.
6.9 Risk Assessments – Practical Approach
Risk Assessments were spoken about in general terms in Chapter 3: Risk Assessments and the Four P Guide. What follows is some practical guidance on how risk assessments may be carried out on low voltage equipment which is where the majority of interactions with energised equipment occur.
Risk Assessments need to document the hazard severity and the risk control measures. Wherever possible, these should be dynamically produced, and task based. In other words, be available to the person carrying out the work who will reassess such things as environmental conditions and equipment state.