Earthing Armoured Cables To Safely Protect LV AC Cables In The Solar Industry
Published 28 Feb 2024
Challenge | This week a Solar EPC client of Thorne & Derrick engaged our Technical Sales Department to assist with ongoing O&M issues relating to the termination connection of steel wire armour (SWA) on 450off 4 core x 240sqmm LV AC cables, 0.6/1kV – the outdoor location cables are connected to a string inverter and the MV station at the remote end on a UK based 50MW solar farm in Derbyshire. The cable armouring provides mechanical protection but is not intended to circulate electrical current.
SWA Cable Steel Wire Armoured Cables | Image FS Cables
BS7671 Clause 522.8.10Â
“Except where installed in a conduit or duct which provides equivalent protection against mechanical damage, a cable buried in the ground shall incorporate an earthed armour or metal sheath or both, suitable for use as a protective conductor. The location of buried cables shall be marked by cable covers or a suitable marker tape. Buried conduits and ducts shall be suitably identified. Buried cables, conduits and ducts shall be at a sufficient depth to avoid being damaged by any reasonably foreseeable disturbance of the ground.”
Earthing Armoured Cables
Solution
Initially, from the viewpoint of the above British Standard the client considered connecting the wire armour at the MV station to ensure that during a fault (e.g.cable strike) an earth path exists to allow safe disconnection of the cable. Earthing the armours of buried SWA cables is important for safety – this prevents/reduces the severity of electric shocks and equipment damage should a person dig inadvertently into the cable. The cable wire armours provide a complete earth path around the cable. Utilizing a single phase within a 4 core cable as earth is not sufficient as it does not offer complete protection around the circumference of the cable. Also, in solar farm installations un-earthed wire armours can have induced voltage from excessive current generated. Therefore, the contractor should always consult the circuit designer.
Customer Service
From initial application, to concept, to design and to sample acceptance by the end client we subsequently completed the despatch and delivery of their order in 5 working days for 450off Armour Earthing Kits.
Important Note
Solderless earth kits that are intended for copper tape screens (MV cables) are a substandard method to earth SWA cables. Solderless earth kits utilize a constant force spring which do not offer a secure earth bond for SWA’s. Also, the cross sectional area of the braid within these kits is inadequate which is why you should always use an armour earth kit for this application. Contact us to discuss your application.
Innovative Connection & Grounding Solutions for LV Cables
Excerpt from Installation Instruction
Heat Shrink Outdoor Armour Earth Kit To Suit
XLPE SWA PVCÂ
The Heat Shrink Outdoor Armour Earth Kit includes medium wall adhesive lined heat shrink tubes, mastic tapes, solder-blocked earth braids and clamps. Contact us for further information, technical support or for a quotation.
THORNE & DERRICK are Specialist Distributors of LV HV Solar Cable Accessories, Jointing, Termination, Earthing & Electrical Equipment 1500V DC to 33kV – we service UK and global businesses involved in cable installations, jointing, substation and electrical construction.
Since 1985, T&D have established reputation based on SERVICE | INTEGRITY | TRUST – we are highly customer responsive and absolutely committed to providing a world-class service.
We provide expert technical support and supply from a multi-million pound stock holding:
- Cable Joints, Terminations & Connectors
- Earthing & Lightning Protection
- Cable Accessories – Lugs & Glands
- Circuit Protection & Fuses
- Cable Cleats & Clamps
- Electrical Safety Equipment
- Cable Pulling & Laying Equipment
- Arc Flash Protection & Clothing
- Cable Duct Seals & Transit Systems
- Surge Arresters & Bushings
- MV HV Overhead Line & Substation Power Products
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Further Reading
Thorne & Derrick are Specialist Distributors of Innovation Tooling & Accessories for LV HV Power Systems to facilitate safe and reliable cutting, crimping, preparation, termination and installation of cables, 600V to 132kV.
