Siemens Transmission and Distribution Ltd was appointed main contractor for the electrical systems on the Gwynt y Môr transmission assets. For the two offshore substations this included supplying and installing the topside mechanical and electrical equipment, notably four 132/33 kV transformers, 132 kV switchgear and 33/0.4 kV earthing and auxiliary transformers. Siemens also delivered the main electrical systems for the onshore substation at St Asaph, including 400/132/13.9 kV transformers, 400, 132 and 13.9 kV power cables, 132 kV GIS switchgear and reactive compensation and harmonic filtering equipment during the construction phase.