Underground Cable Laying Method Statement
The objective of this Method Statement of the Underground Cable Laying is to describe the procedures and methods that will be utilized to install underground 33 kV electricity and fiber optic cables, including the end of the trench and cable.
According to particular site conditions, the electrical contractor reserves the right to modify the execution methods described in this document as needed from time to time.
The list of tasks included in the scope of work includes manual site surveying, trail pit excavation, trenching, cable pulling, cable jointing, cable termination, backfilling, installation of warning tape and protection tiles, reinstatement, installation of route markers and joint markers, cable testing, horizontal directional drilling for road crossings, and site clearing.
Table of Contents
References & Standards
The following documents should be read alongside the method statement:
- Electrical specifications for the project
- Approved cable route drawings
- Existing underground installations
- Any additional instructions provided by the site’s civic authorities
Equipment & Tools
Depending on the site conditions, the following tools & tackles will be arranged as necessary:
- Winch for cable pulling
- Trailer
- Coaxial trolleys
- Drum cable stand and shaft
- Rolling Cables
- Pulling a Rope or a Wire
- Taking Eye
- Link Block
- Swivel / Shackle
- Tester for KV Insulation (Megger) Resistance
- Testing HV Kit
- Digital Multimeter
- Hand Gloves HV
- Grounding Stick for HF
- A Hand Tool
- Trucks
- Crane
- Excavator
- Tanker for water
- 3.5 Ton Truck for moving materials.
- Compactor for plates
- Research Instrument
- Trailer With Low Bed
- Machine for Directional Boring
Work Sequence for Cable Laying
Prior to beginning work, obtain route approval as required. Identify the cable route, conduct a site survey, and mark the cable trench where the cable is being laid.
(Exploratory Excavation) Trial Pits
Obtain a work permit or NOC and “As Built” drawings that indicate all of the current services.
Set up the site, mark the areas to be explored with warning tape or safety cones, spaced 100 meters apart or as required, and close to the existing specified services.
Prior to disclosing their associated services, if necessary, notify the relevant departments.
Using a hand shovel and a pickaxe without any sharp edges, begin manual digging.
Take the required precautions while excavating and keep an eye out for any warning signs, warning tape, or cable tiles that may protrude during excavation.
Open up any known buried services.
Note the specifics of the current services.
As per the given recommendations, protect the services.
Road Crossing
At highway and road crossing points, the contractor must construct separate ducts for each cable circuit, as well as one spare circuit in the required location, in accordance with the requirements of applicable standards and specifications.
The duct must be made of PVC pipes with a wall thickness of 5 mm and a minimum internal diameter of 200 mm.
Future road crossings must be constructed using either the HDD method or an open-cut concrete bank in accordance with established protocols.
Drilling in a horizontal direction (how GDD works)
The number of ducts must meet the requirements, and road crossing by directional drilling (HDD) must be carried out in accordance with the method statement of the approved subcontractor for the HDD works.
As required by the road work specifications, bentonite must be filled in the pipes.
Work on Excavating Trenches
Establish and mark the precise cable route in accordance with authorized drawings, then get NOC or permission to work.
A mechanical excavator is used to perform excavation.
The trench is made through human digging in areas where using an excavator is risky or impossible.
Where sand dunes or any other obstructions are present in the proposed cable routes, they must be cleared to normal ground level in accordance with the project specifications’ route requirements.
Each machine will have a specific charge hand or supervisor attached to it.
The charge hand or his construction supervisor or project engineer will give instructions to the machine operator.
Minimum trench depth and breadth requirements, placement of power cable, 100mm dia UPVC pipe and FO cable, sand filling, protection tiles, warning tape, and other items must all generally follow authorized drawings.
Along the upper edge of the trench, warning tape and safety cones will be provided.
As required, temporary steps will be taken to preserve any existing services that are exposed as a result of excavation.
The excavation’s edge will be cleared of all loose material that was extracted at the trench’s top level.
Prior to sand bedding, the bottom of the excavation or trench must be cut down and clear of pointed objects, such as stones.
Sand Bedding: For cable cushions, a trench with a minimum of 150 mm of sand bedding must be provided.
Cable Pulling and Laying Method
Make sure the areas and trenches where cables are to be hauled out or laid are inspected and approved.
Drums must be positioned on a pair of stands and shafts for smooth pulling.
For the purpose of moving a cable drum or laying cable, the direction of rotation must carefully follow the directions marked on the drums.
Winch should be carefully adjusted and fixed with security to the required distance.
Cable rollers must be positioned at a maximum of 2-meter intervals in accordance with the specifications in order to prevent cable breakage during pulling operations.
The space between the rollers must be kept constant and securely fixed.
As required, the proper corner rollers will be provided.
Pulling into and through curves, crossing roads, and existing ducts will all be done with extra caution.
Clean the ducts if necessary after checking for trash and sharp edges in the cable ducts.
If necessary, cables should be treated with a sealant or pulling compound to make them smooth and simple to draw through cable ducts.
the identification must be provided, and both ends of the cable severed must be sealed and taped.
Prior to jointing and backfilling in accordance with the specification, do a sheath test and merger test on the lay cable.
The sheath test must be conducted by applying 10 kV DC for one minute between the sheath and the exterior graphite surface of the armor, with all other phases being securely grounded and the leakage current being recorded on the sheath test form.
Cable Jointing & Termination: Cable jointing must be completed with the best workmanship possible in accordance with the Joint Kit manufacturer’s instructions or instruction manual.
Backfilling and reinstatement of trenches
Along the cable route, soil thermal resistance must be measured in accordance with the specification.
According to the requirements of the specifications, the soil’s thermal resistivity and temperature of the backfilling material must be measured.
According to the specifications of the project specification, backfilling material must be chemically neutral and have a maximum thermal resistivity of 120 cm2 C/W under operational conditions.
Where the thermal resistance of natural soil exceeds 120 cm2 C/W, special bedding material must be employed in accordance with project requirements.
To maintain the continuity and progress of the work, the Consultant, Owner, or Client may undertake inspections prior to the installation of warning tapes, final backfilling, or cable route markers.
According to the drawings, installed cables must be covered with carefully chosen fine sand up to the level of warning tape.
The 33 KV cable trench protection tiles must be 500 mm long, 250 mm wide, and made of concrete grade C35 with cement type V (SRC), with a minimum cement content of 370 kg/m3. All corners must be chamfered, and names must be fixed to each protection tile in accordance with the specification.
The dimensions of the protection tiles for MV and LV cables must be 500 mm long, 200 mm wide, and 60 mm thick.
If there is any remaining excavated material, it must be leveled and distributed to restore the area to its pre-excavation state, and extra earth may need to be dumped if necessary.
In tiled areas and on footpaths, permanent repair is required.
Markers for Cable Routes:
For each circuit of a power cable, cable route and joint marks must be installed.
The cable route markings must be installed on straight routes at intervals of no more than 30 meters, at the locations where the cable route turns, and at any road crossings on both sides.
To identify the joint, a joint marker must be installed on top of the jointing.
According to authorized specifications, all cable route and joint markers must be made of reinforced concrete and be of the truncated cone type.
Testing and commissioning of cables
Measurement of conductor insulation resistance and sheath test
Notify the parties in question so they can attend the test as needed.
Verify that the cable’s rating, type, size, and number adhere to the drawings and specifications.
The area around the testing area must be fenced off, with access limited to authorized individuals only.
Make that the testing location has current, calibrated test equipment.
For the safe handling and draining of voltage residue, HV hand gloves and HV grounding sticks must be provided.
By removing the cable’s 500 mm-long graphite coating, you can prepare the ends of the cable at both ends for testing.
Prior to the start of cable testing, a shortwave communication system must be in place.
One authorized representative is responsible for watching the cable at the non-testing end for safety precautions.
Cables must be examined for continuity and proper phase alignment.
The results of all required tests must be recorded in test formats in accordance with local requirements.
The sheath test must be conducted by applying 10 kV using an HV DC test kit between the sheath and the exterior graphite surface of the armor for one minute, with all other phases being firmly grounded and the leakage current being recorded.
Immediately following the testing of each phase, voltage leftovers must be removed using a grounding stick that is linked to the earth’s ground.
Prior to jointing, the insulating resistance between phase and earth must be measured.
In accordance with the approved test formats, results must be recorded.
HV testing:
Following the completion of all straight-through joints and end termination, the phasing out/identification process should be completed from one end to the other end. An HV test should then be conducted in accordance with the specification, and the results should be recorded.
Health and Safety Conditions
All excavation work will be carried out in accordance with the project’s health and safety plan, and essential precautions will be made to ensure worker safety and environmental protection. Special focus will be placed on:
encircling the excavation site’s open pit.
If required, create a stable slope.
installation of notice boards and cable safety warning devices.
The site should only be accessible to authorized personnel.
First aid supplies are available on site.
tag: # Method Statement of the Underground Cable Laying