Back to news
Wind turbines are a critical part of the UK’s renewable energy infrastructure, but like any complex electrical installation, they can present significant electrical safety risks.
One of the most serious is Arc Flash.
Arc Flash can occur when an electrical fault creates an uncontrolled electrical arc, releasing intense heat, light, pressure and sound. The consequences can include severe burns, eye injuries, hearing damage, fire, equipment destruction and, in the most serious cases, fatal injury.
The fundamental Arc Flash hazards within a wind turbine are similar to those found in other industrial electrical installations. However, the operating environment of wind-turbine electrical systems introduces additional considerations.
Wind turbines can be located in remote areas, offshore or on elevated ground. Access and escape routes can be restricted, electrical equipment may be located within confined sections of the tower or nacelle, and a fire can create an especially challenging emergency situation.
For organisations responsible for wind farms, understanding the potential Arc Flash risk is therefore an important part of electrical safety management.
What is Arc Flash?
An Arc Flash is an electrical explosion or discharge that occurs when current travels through an unintended path between conductors, or between a conductor and earth.
The resulting arc can generate extremely high temperatures in a very short period of time.
HSE’s guidance on electrical safety recognises electrical arcing as a significant hazard. An arc can generate intense heat that can cause deep burns, while the associated ultraviolet radiation can damage the eyes. Arcing can also contribute to fire and explosion, potentially causing serious injury and significant equipment damage.
The severity of an Arc Flash depends on several factors, including the available fault current, the characteristics of the electrical system, the duration of the arc, and the protection arrangements in place.
This is why simply knowing a system’s voltage does not provide enough information to understand the Arc Flash hazard.
The electrical system needs to be assessed, usually starting with an arc-flash study.
Why can Arc Flash be particularly challenging in wind turbines?
Wind turbines have many of the same electrical hazards as other industrial installations.
However, the physical environment can make the consequences of an incident more difficult to manage.
- Remote locations
Wind turbines are often located away from population centres.
Onshore wind farms may be located in remote or elevated areas, while offshore wind turbines can be many miles from shore.
If an electrical incident occurs, emergency response and access to the turbine may be more difficult than at a conventional industrial facility.
The location itself, therefore, needs to be considered when developing emergency arrangements and safe systems of work.
- Restricted access and egress
The internal arrangement of a wind turbine can create challenges for people working on electrical equipment.
Workers may need to access equipment through the tower before reaching the nacelle or other areas containing electrical systems.
Following an Arc Flash, fire or other electrical incident, leaving the area may not be straightforward.
The risk assessment, therefore, needs to consider not just the electrical hazard itself, but also what happens if an incident occurs while someone is working inside the turbine.
- Fire
An Arc Flash can generate sufficient heat to ignite surrounding materials.
Within a wind turbine, a fire can be particularly serious because of the height, restricted access and the difficulty of getting emergency services directly to the source.
A fire within the nacelle or tower can also damage critical equipment and result in significant operational disruption.
Electrical faults should therefore be considered as part of the wider fire and emergency risk associated with wind-turbine operations.
- High fault levels
One of the important findings from ESUK’s work on wind farms is the high-voltage network connecting the turbines to the wider electrical network can have significant Arc Flash incident energy levels.
The existing ESUK technical assessment identifies HV network incident energy levels above 8 cal/cm² as being common in the wind-farm installations it has studied.
This is largely associated with the fault levels available from the wider electrical network to which the wind farm is connected.
The connection to the wider grid can therefore significantly influence the available fault current during an Arc Flash event.
What about the wind turbine itself?
It is important to understand the difference between the contribution from the wind turbine generator and the fault contribution available from the wider electrical network.
Modern wind turbines commonly use power-electronic conversion between the generator and the electrical network.
This means the turbine’s contribution to the fault level could be limited compared with that of some conventional generation systems.
However, that does not mean the Arc Flash risk is low.
The electrical network connecting the wind farm to the wider grid can still provide significant fault current, particularly on the high-voltage side.
The overall system, therefore, needs to be assessed rather than making assumptions based solely on the type of wind turbine generator.
Where could Arc Flash risks occur within a wind turbine?
A wind turbine contains a range of electrical equipment and systems that should be considered during an Arc Flash assessment.
Depending on the turbine design and electrical configuration, this can include:
- High-voltage switchgear
- Transformers
- Low-voltage distribution equipment
- Power converters
- Control panels
- Motor control equipment
- Harmonic filter equipment
- Protection equipment
- Busbars
- Cable connections
- Auxiliary electrical systems
- Generator equipment
- Substation and collector systems
- Grid connection equipment
The exact risk will vary between installations.
Different turbine models, electrical configurations, network arrangements, and grid connections can lead to distinct fault conditions and incident energy levels.
This is why a generic assessment cannot replace a study of the actual electrical system.
Arc Flash risk does not stop at the turbine.
When assessing a wind farm, it is important to look beyond the individual turbine.
A wind farm is an electrical network.
Turbines may connect into collection systems, substations and higher-voltage networks before ultimately connecting to the wider grid.
The available fault current and protection characteristics can change throughout this network.
A comprehensive Arc Flash study should therefore consider the relevant electrical system from the sources through to the equipment being assessed.
This can help identify where the highest incident energy levels occur and where additional risk reduction measures may be required.
Why protection systems matter
Protection systems play an important role in managing electrical faults.
When a fault occurs, protective devices should detect the fault and disconnect the affected part of the electrical system.
The time taken to clear the fault can significantly influence the energy released during an Arc Flash.
Protection coordination is, therefore, an important part of understanding Arc Flash risk.
An Arc Flash study should account for the relevant protection devices and their settings when calculating potential incident energy.
Where appropriate, the results from such as study may identify opportunities to improve protection performance and reduce the duration or severity of an Arc Flash event.
This is one reason why Arc Flash analysis should be considered alongside other electrical system studies, rather than treated as an isolated exercise.
Safe isolation is fundamental.
One of the most important ways to prevent Arc Flash exposure is to avoid working on or near energised equipment wherever reasonably practicable.
The Electricity at Work Regulations 1989 place duties on those responsible for electrical systems and work activities to prevent danger.
Regulation 12 addresses the provision of suitable means for cutting off the supply and isolation, while Regulation 13 requires adequate precautions to prevent equipment which has been made dead from becoming electrically charged again while work is being carried out. Regulation 14 addresses work on or near live conductors.
In practice, this means that electrical work needs to be properly planned and controlled.
The correct equipment must be identified.
All relevant sources of electrical energy need to be considered.
The equipment needs to be isolated and secured against reconnection.
The isolation needs to be verified before work begins.
This becomes particularly important in wind turbines because there can be multiple electrical sources, stored energy and complex network arrangements.
Simply operating a switch is not enough.
The person carrying out the work needs to know that the equipment they are working on is actually isolated and safe.
Competence is a key part of electrical safety.
The Electricity at Work Regulations 1989 also require those carrying out work on electrical systems to have the technical knowledge or experience necessary to prevent danger and injury, or to be appropriately supervised.
This is particularly relevant in wind-farm environments.
Technicians may be required to work on complex electrical systems, often in challenging physical conditions and sometimes far from immediate support.
They need to understand:
- The electrical systems they are working on
- The hazards associated with those systems
- Safe isolation procedures
- Arc Flash risks
- Appropriate test equipment
- Emergency arrangements
- The limitations of their own competence
- When should work stop, and additional support be obtained
Training should therefore form part of the wider electrical safety management strategy.
What does an Arc Flash study provide?
An Arc Flash study analyses an electrical system to determine the potential hazard associated with an electrical arc fault.
For a wind farm, this would involve collecting and validating information about:
- The grid connection
- Utility fault levels
- Transformers
- Generators
- Turbine electrical systems
- HV and LV switchgear
- Protection devices
- Protection settings
- Cables
- Busbars
- Network configuration
- Operating arrangements
The electrical network can then be modelled to calculate fault conditions, incident energy and Arc Flash boundaries at relevant locations.
The results provide a clearer picture of where the electrical hazards exist and where risk reduction may be required.
This information can then support decisions around:
- Engineering controls
- Protection settings
- Isolation arrangements
- Safe systems of work
- PPE requirements
- Arc Flash labelling
- Training
- Maintenance
- Emergency planning
An Arc Flash label is not the solution.
Arc Flash labels are one of the outputs of an arc flash study and can provide valuable information to people working on electrical equipment.
But a label does not remove the hazard.
The purpose of an Arc Flash assessment should be to understand the risk and then use that information to reduce it so far as reasonably practicable.
This means asking questions such as:
- Can the work be carried out with the equipment isolated?
- Can the incident energy be reduced through engineering controls?
- Are the protection settings appropriate?
- Is the equipment adequately maintained?
- Are the safe systems of work suitable for the task?
- Are the people carrying out the work competent?
- Is the Arc Flash information current?
PPE can be an important part of the control strategy where appropriate however, it should not be the first option or used as a substitute for effective risk reduction.
Engineering controls can help reduce Arc Flash risk.
Depending on the electrical system, engineering measures may provide opportunities to reduce the hazard before a worker is exposed to it.
These may include:
- Reviewing protection settings
- Improving protection coordination
- Reducing fault-clearing times
- Remote switching
- Remote operation
- Appropriate current-limiting technology
- Arc-resistant equipment where appropriate
- Improved isolation arrangements
- Remote monitoring
- Appropriate electrical system design
The appropriate controls will depend on the individual wind farm and the hazards identified by the real assessment.
There is no single solution that applies to every installation i.e. Arc Flash PPE
Wind turbine maintenance and Arc Flash
Wind turbines require regular inspection, maintenance and repair to remain operational.
That maintenance can introduce electrical risk.
The Electricity at Work Regulations 1989 require electrical systems to be maintained, so far as is reasonably practicable, in a condition that prevents danger.
HSE guidance also emphasises the importance of safe working practices for those involved in the design, operation and maintenance of electrical equipment.
Maintenance activities should therefore be considered when assessing Arc Flash risk.
Particular attention should be given to work involving:
- Switchgear
- Transformers
- Electrical panels
- Power converters
- Protection equipment
- Busbars
- Cable connections
- HV equipment
- Testing and commissioning
The objective should be to ensure that maintenance activities are planned around the actual electrical hazards present.
What UK regulations apply to wind turbine electrical safety?
For wind farms operating in Great Britain, the Electricity at Work Regulations 1989 are central to the management of electrical safety.
They apply to electrical systems and associated work activities, and include requirements for the construction and maintenance of systems; protection against excessive current; isolation; precautions when equipment is made dead; work on or near live conductors; and competence.
The Management of Health and Safety at Work Regulations 1999 are also relevant to the wider management of risk. They require employers to make suitable and sufficient assessments of risks to employees and others arising from their work activities and to put appropriate health and safety arrangements in place.
HSE’s HSR25: The Electricity at Work Regulations 1989 provides guidance for dutyholders on achieving electrical safety compliance.
HSG85: Electricity at Work: Safe Working Practices provides practical guidance on safe working practices for people carrying out work on or near electrical equipment, as well as managers and supervisors who influence electrical equipment and its operation.
These requirements do not prescribe that every wind farm must undertake a particular type of Arc Flash study at a fixed interval.
Instead, the duty is to identify and control electrical risks and prevent danger so far as reasonably practicable.
An Arc Flash study is an important engineering exercise for helping an organisation identify, understand and manage those risks.
When should a wind farm review its Arc Flash study?
An Arc Flash study followed by risk assessment should reflect the electrical system that actually exists.
A review should therefore be considered following significant changes that could affect fault levels, protection or network configuration.
Examples may include:
- Changes to the grid connection
- Transformer replacement
- Changes to protection settings
- New electrical equipment
- Major turbine modifications
- Changes to the collector system
- Substation modifications
- Changes to network configuration
- Changes to operating arrangements
- Significant maintenance or refurbishment
- Electrical incidents or near misses
A review may also be appropriate where the existing study is based on incomplete or outdated information.
The key question is whether the latest study still accurately represents the current electrical system and the risks associated with it.
Building Arc Flash into a wider electrical safety strategy
An Arc Flash study should not exist in isolation.
For wind-farm operators, electrical safety should form part of a wider management system incorporating, but not limited to – carrying out:
Electrical system studies
For understanding fault levels, protection coordination and system behaviour.
Safe systems of work
Making sure electrical work is properly planned and controlled.
Isolation
Ensuring equipment can be safely isolated and proven dead before work begins.
Competence and training
Making sure people have the knowledge, skills and experience required for the work they undertake, and knowing their limitations.
Maintenance
Keeping electrical systems and protective equipment in a condition that supports safe operation.
Engineering controls
Identifying opportunities to reduce Arc Flash energy and exposure at the source.
Emergency planning
Considering the consequences of an electrical incident, particularly where turbines are remote or difficult to access.
Electrical Safety Management
Ensuring responsibilities, procedures, competence and controls are properly managed across the organisation.
Questions for wind-farm operators
If you are responsible for electrical safety on a wind farm, ask yourself:
- Do we know the Arc Flash risk across our electrical network?
- Does our Arc Flash study and Arc Flash Risk assessments reflect the current system configuration?
- Have our grid connection and fault levels been considered?
- Are the protection settings optimised to minimise arc flash incident energy while maintaining adequate discrimination (selectivity) between protective devices?
- Do we know where the highest incident energy levels are?
- Are Arc Flash labels based on current information?
- Can maintenance activities be completed safely with equipment isolated?
- Are our isolation procedures robust and properly verified?
- Are technicians competent for the electrical work they undertake?
- Have we considered the challenges of access and escape following an electrical incident?
- Have we considered fire as part of the consequences of an Arc Flash?
- Have significant changes to the wind farm triggered a review of the electrical risk assessment?
- Does our Electrical Safety Management System reflect the way the wind farm actually operates?
If the answers to these questions are unclear, it may be time to review your electrical safety arrangements.
Understanding Arc Flash risk in renewable energy
Wind energy is an important part of the UK’s electricity infrastructure, but renewable generation does not remove conventional electrical hazards.
Wind turbines contain complex electrical systems operating within challenging physical environments.
The combination of high-voltage networks, significant available fault levels, restricted access, remote locations and maintenance activities means Arc Flash risk needs to be properly understood.
The objective is not simply to accept that arc flash is a hazard.
It is to identify where the hazard exists and reduce the associated risk wherever reasonably practicable.
That means understanding the electrical network, reviewing protection systems, maintaining equipment, controlling electrical work, ensuring competence and using appropriate engineering controls.
An Arc Flash study can provide an important part of that picture.
How ESUK can help with wind-farm Arc Flash risk
Electrical Safety UK has experience conducting Arc Flash studies for wind farms and other complex electrical installations.
Our work can help organisations understand the potential Arc Flash hazards within their electrical networks and identify practical opportunities for risk reduction.
Our services include:
- Arc Flash studies
- Arc Flash management
- Arc Flash pre-assessment
- Electrical system studies
- Protection and coordination studies
- Electrical Safety Management
- Electrical Technical Authority support
- Arc Flash training
- Electrical safety training
We can also provide an initial pre-assessment visit to discuss your requirements and determine the appropriate scope of work.
Do you understand the Arc Flash risk within your wind farm?
If your wind farm has changed since its original electrical studies were completed, or you are unsure whether your existing Arc Flash information accurately represents the current installation, speak to ESUK.
Understanding the electrical risk is the first step towards managing it.
Contact Electrical Safety UK to discuss your wind-farm Arc Flash requirements.
