Management of Risk During Fault Finding in Electrical Systems

In today’s fast-paced industrial environment, ensuring the safety of personnel during fault-finding activities on electrical systems is paramount. This article continues the series of articles I have written on what could be included in your electrical safety management system. It looks at some of the guidelines that could be included to mitigate risks associated with these activities. This article summarises key points and highlights good practice.

Purpose and Scope

Your instruction’s primary goal is to establish safe working practices when fault-finding on low-voltage electrical equipment or systems. It applies to all personnel involved in the operation, maintenance, design, planning, and implementation of electrical distribution systems.

Responsibilities

Responsibilities extend beyond those directly involved with electrical systems to include anyone who may come into contact with or be in proximity to electrical services. This includes project managers, designers, maintenance personnel and planners. Compliance with your instruction should be mandatory to ensure safety.

General Requirements

When encountering unfamiliar or poorly maintained equipment or when unforeseen problems arise, consulting Competent Electrical personnel is crucial. Work should only be carried out on de-energised equipment unless it is absolutely necessary to work live. If live working or working in proximity to live conductive parts is required, a thorough risk assessment must be conducted.

Competency and Access

Fault-finding requires specialised knowledge and competency. Only trained and experienced personnel should perform these tasks. Always treat conductors as energised until proven otherwise and maintain detailed records of observations and actions taken during fault-finding.

Specific Procedures

Electrical Test Instruments

Tools and test equipment selection should adhere to your established electrical safety rules. Creating and maintaining an approved list of tools and test equipment should be part of your electrical safety rules. Proper tools and instruments are essential for safe fault-finding. You may need to conduct random inspections of tools to verify that the rules are being followed.

Non-starting and Non-stopping Motors

Identify the cause of motor issues, such as overload trips or control circuit failures, with the starter de-energised. Avoid using isolators to stop motors, as they are not designed for switching load or fault current and could fail disruptively if used incorrectly.

Isolators and Fused Switches

If the function of an isolator or fused switch is in doubt, work should stop, and the compartment door should be closed and locked. A notice should be affixed to the operating handle warning of the danger until the fault can be repaired.

Changing fuses

If a fuse needs to be replaced, it should be done under no load conditions, and it should be checked to ensure that it is of the correct type and size before the change is made. In a three-phase circuit, if one fuse fails, all three fuses must be changed. Whenever a fuse fails, the cause of its operation should be investigated and remedied.

Fused distribution boards

If it is necessary to replace a fuse, inserting a fuse carrier into a faulty circuit can produce an arc flash; similarly, an arc can be drawn when withdrawing a fuse in a highly loaded circuit. If the fuse rating is >= 100 amps, an assessment of the likelihood of an arc flash being produced must be made, and the need to wear arc flash PPE must be considered.

Neutral Conductor

When an outgoing circuit from a distribution board needs to be isolated by withdrawing a fuse and disconnecting its associated neutral conductor, care must be taken to identify the correct neutral, particularly if there is more than one in the same terminal. Disconnecting the wrong neutral may lead to overvoltage on single-phase circuits.

Plug-in/Withdrawable Equipment

Handle plug-in equipment according to the manufacturer’s instructions, ensuring proper alignment and secure placement when putting back in the service position.

Circuits Retaining Charge

Ensure all charges are dissipated before working on the equipment you suspect may be charged. Follow manufacturer instructions for safe discharge methods.

Capacitor Banks and DC Bus Systems

Extreme caution is required when fault finding occurs on capacitor banks and DC bus systems. High-energy capacitor banks pose several hazards to personnel, for example:

• Electric shock

The following precautions should be considered when risk assessing any activity being carried out on capacitor banks:

• Isolate, lock, tag and test electrical supplies.

Working on or Near Energised Electrical Systems

De-energised work should be the default for electrical work, but if energised work is absolutely necessary and can be done safely, a risk assessment should be completed. The risk assessment should consider:

• competency of the person/s carrying out the work.
• examination of the equipment, identify exposed energised parts.
• availability and accuracy of installation documentation.
• condition of the equipment.
• the rating of supply fuse(s)/protective devices to the circuit.
• the voltage(s) of the exposed parts.
• the prospective fault current at that part of the system, the breaking capacity of the protective device, and its operating characteristics.
• the arc flash incident energy value at the point of work.
• the work to be undertaken.
• the likelihood of making contact with hazardous parts.
• the effect/consequence of making contact with hazardous parts.
• reduce the risk by the addition of insulation, shielding of terminals or manufacture of temporary barriers, which can be removed on completion of the work.
• The suitability and necessity of personal protective equipment (PPE) such as appropriately rated arc flash PPE and/or appropriately rated PPE to protect from electric shock, e.g. gloves.
• the tools and instruments required to complete the work safely, such as GS38 (HSE Guidance Document) compliant test leads and the use of insulated tools;
• the necessity for a Standby Person to be in attendance.
• the provision of equipment and the need for persons to be trained in the use of that equipment to assist in the event of an incident, such as firefighting Apparatus, rescue hooks, automated external defibrillators, advanced first aid equipment such as burns and blast dressings.
• any additional precautions should be taken before, during or after work commences.

Conclusion

Effective risk management during fault-finding activities is essential to prevent accidents and ensure the safety of personnel. By creating and following the guidelines outlined in your instructions; organisations can create a safer working environment and minimise the risks associated with electrical systems.