33kV substation earthing is provided around the transformer bund and new building structure using copper earthing tapes, electrode rods and exothermic welding (CADWELDing) of the earth rods to tape – 50mm x 4mm earth tapes are installed as a ring and cross earthing design with 40mm x 4mm copper tape braised for additional stairs and walkway earthing.
The 33kV switchgear housing within the high voltage substation is earthed and bonded to a new transformer ring and Neutral Earth Resistors (NER). The copper tapes and earthing cables are shown connected to the 10 way earth bar. To achieve the required earth resistivity reading 3 x 1.2 metre length coupled copper earth rods were driven into the ground.
Driven earth rods are used to exploit lower resistivity ground conditions where present to reduce the earth potential rise (EPR) on substation earthing and lightning protection projects from 11kV/33kV up to 400kV.
Earthing of low, medium and high voltage electrical networks is critical to ensure safe and correct operation preventing and minimising against the consequences of a direct lightning strike to equipment and buswork within substations. UK DNO’s publish primary and secondary substation earthing designs for the application of earthing systems to HV and LV underground cables and overhead line networks, typically operating at 33kV, 20kV, 11kV, 6.6kV, 3kV and 2kV.
Similarly, the National Grid publish an Earthing Technical Specification for the lightning protection of transmission and distribution systems located in the busbar protection zone of the electricity grid operating at nominal voltages of 400kV, 275kV 132kV and 66kV. The general requirements of the substation earthing systems are compliance with technical standard EA TS 41-24 and British Standards BS EN 50522 and BS7430.
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Copper Earth Tape – the earthing tape 40mm x 4mm shown bonding to the existing medium/high voltage substation earth bar
Copper Earth Tape Dropper – 50mm x 4mm earth tape is shown earthing switch 1 of 3 on the 33kV distribution board
Earth Tapes – the 50mm x 4mm copper tapes are routed back to the rebar earths on the earth bar
Transformer Earthing – using 40mm x 4mm copper earthing tape on the 33kV high voltage transformer
Power Jointing Services Ltd established in 2007 specialising in 33kV-400V electrical network construction, establishing industrial and commercial supplies, installing residential service connections and street lighting connections. Also: High voltage service alterations, cable fault finding and replacement of assets including transformers, low voltage distribution boards and link boxes.
T&D provide competitive prices and fast delivery from stock for Earthing & Lightning Protection products including copper tapes, rods, electrodes, earth bars and ancillary items for low, medium and high voltage substations.
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T&D distribute the most extensive range of LV, MV & HV Cable Jointing, Terminating, Installation & Cable Pulling Equipment – we service UK and international clients working on underground cables, overhead lines, substations and electrical construction at LV, 11kV, 33kV and EHV transmission and distribution voltages.
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T&D’s Power Blog covers: LV MV HV & EHV Transmission & Distribution, Substations, Switchgear, Cable Jointing & Termination, Cable Fault & Repair, Underground Cables.
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Published 06 Jun 2022
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