Requirements
Electrical Safety UK Ltd (ESUK) were initially approached by a Senior Authorised Person (SAP) at National Grid in regard to seeking further consultancy and advice regarding the risk of Arc Flash.
ESUK were commissioned to carry out arc flash pilot studies at 4 sites in the Sheffield area. The results of these studies showed a need to take action to mitigate the risk of arc flashes on site.
The subject of arc flash risk was escalated within National Grid and led to the company asking ESUK to carry out a comprehensive study of the arc flash risk at 15 selected National Grid sites around the UK.
Scope of work
ESUK suggested that arc flash studies should be carried out at the 15 National Grid sites. The scope of the assessment was restricted to switchgear rated between 1kV and 33kV, representing the limit of the assessment methodology. National Grid also wanted to understand the arc flash risk on their Low Voltage (LV) switchgear. ESUK suggested that arc flash studies should be carried out on a representative sample of the LV switchgear that could be found on the 15 sites identified by NG. ESUK also suggested that task‐based arc flash risk assessments should be carried out on all the switchgear that the arc flash studies were to be carried out on.
Approach
A detailed project plan was produced for all the 15 National Grid sites. For each site, the process was very similar:
- Visit each site to collect data for the arc flash study for that site
- During the site visit carry out a task‐based arc flash risk assessment for each switchboard that was included in the scope of the study
- Develop the software model for the sites
- Carry out Arc Flash studies for the sites
- Produce a report for each site including recommendations and arc flash labels
The site visits presented some challenges as all the sites were operational and engineers needed to be accompanied during our visits. The project ran through the period of UK‐wide COVID restrictions. We had to work closely with the project lead and the site staff to arrange site visits, which involved good communication and patience.
Once the site visits had been carried out, we had the data we needed to build the software models. The challenges we faced with model building centred around the age of some of the switchgear/protective devices and the availability of older switchgear/protective devices in the software device library. In some cases, we had to add obsolete devices to our device library, which involved using data sheets to allow the devices to be correctly modelled.
During the site visits we also completed the task‐based arc flash risk assessments. These risk assessments considered the following:
- The design of the switchgear
- The age and condition of the switchgear
- The maintenance and failure history of the switchgear
- The incident energy levels and the arc flash boundary distances
- The activities being carried out by NG personnel on the switchgear i.e. how were they interacting with the switchgear
- The risk of an arc flash event whilst carrying out their activities
- Factors that could increase the risk of an arc flash
- Control measures that could be used to lower the risk
- Whether PPE should be worn whilst carrying out a particular activity and if PPE was required, what the rating of the PPE should be
- The operation of the switchgear
- Recommendations coming out of the risk assessment
When we produced our arc flash study reports and risk assessments there were some common themes that came out in our recommendations:
- Switchgear incident energy levels were generally very high (> 40 cal/cm2)
- Improvements to Task Based Risk Assessments to reduce personnel being exposed to Arc Flash Risk
- Switching operations are normally carried out remotely
- Improvements to maintenance of switchgear
- Recommendations for improvements to training including arc flash awareness training
- Recommendations for suitable arc flash PPE
In response to the assessment, National Grid has implemented our recommendations, utilising arc flash PPE where appropriate and seeking to restrict access or implement other mitigation when operating switchgear with higher incident energies.
What did our client say?
“I would like to thank you and your team for their efforts and dedication in seeing this project through to completion, especially given the challenges we faced with Covid and finding problematic information.”
Matthew Iles, BEng CEng MIET Lead Transmission Engineer Electricity Transmission – nationalgrid
