1. PART 1 MATERIALS 1.1 Source of Approvals All materials and work shall comply with all the current relevant British Standards (BS), specifications and regulations issued by the Electricity Distribution Directorate (EDD). The contractor shall confirm the characteristics of the power supply before ordering equipment dependant on these factors. 1.1.1 Utility Power Distribution 1.1.1.1 Electrical Supply The characteristics of the power supply as provided by the Electricity Directorate are as follows: • • • 400 V ± 6% 3 phase, 4 wire, 50 Hz ± 2% System 230 V ± 6% 1 phase, 2 wire, 50 Hz ± 2% System Fault level: 31 MVA at 400 V for 0.5 sec duration The contractor shall, however, confirm these before ordering equipment depending on these factors. 1.1.1.2 Transformers Transformers shall be provided in accordance with the Electricity Distribution Directorate’s Regulations for Electrical Installations as currently amended. The transformers shall be constructed to BS EN 60076 or BS 6436 as applicable. The transformers shall be 11,000 V primary to a 400 V secondary, DYN 11 type transformer, either cast resin or oil filled as required. The power supply system shall be 400 V, 3-phase, 50 Hz, arranged in a TN-S configuration, with separate neutral and protective conductors throughout the system. Cast resin or dry type shall comply with the following standards: • • IEC 60076 BS EN 60076 Power Transformers Power Transformers Three phase, double wound windings shall be provided, connected and marked to vector group reference Dyn 11 BS EN 60076 unless otherwise indicated on the drawings. Off-load tappings shall be provided on higher voltage winding for a variation of ± 2.5% and ± 5% of the primary voltage. Fire behaviour class shall be to BS 7844; Class F1 or Class F2 Oil or synthetic liquid immersed shall comply with the following standards: • • BS EN 60076 and IEC 60076 – Power Transformers BS 7821 – Oil-immersed distribution transformers Three phase, double wound windings should be provided, connected and marked to vector group reference Dyn 11 BS EN 60076 or as otherwise indicated on the drawings. Page 5