About Northern Power Grid
Northern Power Grid is a Distribution Network Operator owning Yorkshire Electricity Distribution Ltd and Northern Electrical Distribution Ltd covering an area of 25000km2 and 3.8 million customers.
Management were undertaking a review of their PPE requirements for staff and contractors and decided that a more sophisticated approach to the arc flash hazard was needed.
Electrical Safety UK Ltd, who had the capability of undertaking complex arc flash hazard analysis and had good knowledge of US standards (NFPA 70E) for electrical safety, were contracted to undertake risk assessments.
ESUK alongside staff examined various high risk work streams including low voltage underground operations, LV overhead lines and secondary high voltage operations. Due to the criticality of working space, stance and distance, extensive measurements of operator body parts to prospective arc fault sources were undertaken and complimented with photography.
System models were constructed within complex modelling software which allowed for a plethora of scenarios to be run. This meant that data could be converted into tables and graphs created to indicate worst and average case situations; then conclusions could be drawn in respect of incident energy to various parts of an operator’s body. Those involved in the study were surprised by some of the conclusions; such as the paradox that the highest incident energy values were not at the highest fault levels. For instance, the highest predicted severity ratings for a jointer working on an LV main were not next to the secondary substation but over 360 metres away.