Estimation of the limiting penetration of low carbon connections through an assessment of LV harmonics

Delivery of the UK Government's Carbon Plan to achieve the reduction in emissions required for compliance with the fourth carbon budget will drive an increasing number of non-linear connections onto electrical distribution networks. More photo voltaic generators, heat source pumps and electric vehicle charging points are expected to increase harmonic distortion levels on the LV system. Commissioned by Electricity North West Limited, a simple assessment has been undertaken to determine the likely amount of these harmonicproducing connections to low voltage distribution networks that could be made whilst maintaining harmonic voltage distortion values below the planning levels of Engineering Recommendation G5/4-1 [3]. Using typical system parameters, harmonic voltage distortion values were estimated based on assumed current injections from the new connections and average network background harmonics, calculated from measurements at 50 random LV sites. It was found that the limiting penetration level of low carbon connections was 40% of the distribution substation rating and it is postulated that this could be extrapolated to apply to the entire UK distribution network.