Stokbord | Protection of HV Cables Up to 33kV In Underground Trenched Applications

Step-by-Step Installation

Step 1: Excavate and prepare the trench

1. Excavate the trench to the specified depth and width. Keep side slopes stable and safe. Follow excavation safety rules and shoring requirements
2. Create a uniform bedding layer to the depth specified (often sand or fine granular material). Remove large stones or debris that could damage cables or covers
3. Compact bedding lightly where required, but maintain cable manufacturer’s bedding requirements

Step 2: Lay the cables

1. Place cables on the prepared bedding, maintaining the required separation between circuits and other services
2. Observe minimum bending radii and cable handling best practice. Use cable rollers or spreaders for long pulls
3. Secure temporary supports or spacers where required to keep cables in the correct alignment before placing covers

Step 3: Place Stokbord covers

1. Start at one end of the trench. Carefully place the first Stokbord panel so it fully covers the cables in that bay section
2. Ensure covers are laid flat and centered over the cable run. Avoid trapping cables between covers maintain clearance and avoid point loads on cable sheaths
3. Join adjacent covers using the supplied clips/fixings. Where protection covers need trimming, use the recommended cutting tool and deburr any sharp edges
4. For joint bays or irregular sections, use pre-cut pieces or joint bay kits to achieve continuous coverage

Step 4: Secure and seal

1. Fit any required edge seals, mechanical fixings, or locking clips per the Stokbord installation guide
2. If specified, place geotextile separation layer over covers to prevent stone migration and protect the panel surface
3. Lay warning tape (detector tape) at the specified distance above the covers to alert future excavators

Step 5 — Backfill and compact

1. Backfill the trench in layers (lifts) with the approved material. Avoid using large clods or stones directly above the panel
2. Compact each lift to the specification but avoid over-compaction directly on top of the covers/cables which could cause point loading
3. Maintain records of backfill material and compaction trials as required by project QA

Step 6 — Final checks and handover

1. Visually inspect the installed protection covers for gaps, poorly joined seams or damage
2. Confirm as-built cable positions and panel extents on the site drawings / GPS records
3. Provide the client with the installation checklist, any spare covers supplied and recommendations for future maintenance or marker locations

Quality & testing

Common checks:

• Make sure the covers are continuous and joints are fully engaged, small gaps can allow ingress of sharp objects during backfilling
• If covers are damaged during handling, replace the damaged section rather than attempting a field repair unless allowed by the manufacturer
• Ensure warning tape is clearly visible and at the correct depth to aid future excavators

THORNE & DERRICK are national distributors of LV, MV & HV Cable Installation, Jointing, Duct Sealing, Substation & Electrical Equipment – we service UK and global businesses involved in cable installations, cable jointing, substation earthing, overhead line and electrical construction at LV, 11kV, 33kV and EHV.

Since 1985, T&D have established an international reputation based on SERVICE | INTEGRITY | TRUST.

Contact us for 3M Electrical, ABB, Alroc, AN Wallis, CATU Electrical, Cembre, Centriforce, CMP, CSD, Elastimold, Ellis Patents, Emtelle, Euromold, Filoform , Furse, Lucy Electric & Zodion, Nexans, Pfisterer, Polypipe, Prysmian, Roxtec, Sicame, WT Henley.