1. PURPOSE: This Method statement covers the on site installation of the final electrical connections to the MV-LV equipment. As defined in General Specifications.
2. SCOPE OF WORK: This procedure defines the method to be used to ensure that Cable ladder – Cable Tray and associated cable for final electrical connections to the MV-LV equipment and workmanship are correct and acceptable, and shall conform to the Contract documents and specifications. Schedule of material to be reviewed; See latest revision of Material Procurement Schedule.
3. RESPONSIBLE PERSONNEL
- Construction Manager
- MV-LV Electrical Superintendent.
- QC Inspector.
4. PRE INSTALLATION REQUIREMENTS
- All materials and documentation relevant to a particular section of works will be checked by the Construction Department prior to the Commencement of works ensuring that these are of correct type as reviewed.
- Before commencement of any permanent works pre-inspection will be carried out on all materials prior to them leaving the storage area.
- Prior to the commencement of permanent works, areas and access will be inspected to confirm they are in a suitable condition for permanent works to commence. The Client is invited to attend this inspection.
5. METHOD STATEMENT FOR INSTALLATION
- Ladder Rack and Cable Tray – To support PVC insulated Power Cables.
- Installation supervisor will instruct tradesmen regarding the execution of the works and will distribute all necessary approved construction drawings of the latest revision.
- The supervisor will also check that tools and equipment available are in compliance with contract requirements.
- Cable trays formed from perforated metal will be installed at correct elevations and coordinated locations as indicated on the approved construction drawings.
- Cable trays will be independently supported from the main structure, wherever possible, at intervals not exceeding 1.5m, and on one side of and at a distance not exceeding 500 mm from a bend or intersection, with approved galvanized brackets.
- Cable trays will be cut along a plain line of metal and not through the perforations, all cut edges shall be prepared and treated with cold galvanized paint and de-burred of any rough remaining metalwork.
- Cable trays will be connected between adjacent lengths tee or bend pieces by butt joints, and securely fastened by mushroom head steel roofing bolts, connections shall be mechanically strong so that no relative movement between the two lengths can occur and shall be efficiently and adequately bonded.
- Perforations for cable entry and exit will be made with the correct size cutting device. Trays with a nominal width of 100mm or 150mm will not have cable entries within the circular portion of the bend.
- Holes cut in cable tray for the passage of cable shall be provided with grommets. Alternatively they will be bushed or lined.
- A minimum clear space of 20mm shall be left behind all cable trays wherever possible.
- Property expansion splice plate will be used to join adjacent lengths of tray. Trays will not joined when crossing a construction expansion joint. At these points the tray shall be bridged with a flexible earth conductor.
- Cable ladders will follow the same criteria as trays where applicable and shall be supported at intervals of not more that 1500mm on steelworks of adequate strength and rungs shall be slotted for cable clamping or tying.
- Where cables turn down to MV-LV panels or switch boards, drop out accessories will be used with each ladder to support the cables as shown on the construction drawings.
- Cable tray deflection shall not exceed 1/100 of a 1.2m span at the mid point of the span after cable installation. It will comply with the manufacturer recommendation.
- Where cables are required to peel off a tray, a moulded protective edging shall be fitted to the tray.
- Cable ladder deflection shall not exceed 1/100 of the span at the mid-point of the centre span of a 1.5 span continuous beam after cable installation. It will comply with the manufacturer recommendation.
6. CABLE INSTALLATION
Layout and method of installation will be as shown on the approved construction drawing.
- In particular the following will be adhered to: a) Maximum allowable pulling tension shall not be exceeded. b) Minimum bending radii shall be adhered to as per specifications/manufacturers recommendations. c) Rollers will be used at intervals to prevent dragging the cables during the cable installation on cable tray or ladder rack. Curve rollers will be settled at the proper position in order to keep the cable within suitable bending radius for pulling cable around curves and bends.
- The installation from cable drum onto cable tray or ladder rack : drum setting position will be determined in consideration of the cable laying direction, so that the cable can be reeled out onto tray or rack in a smooth curve without being .
- Each cable will be fitted with a cable identification tag as per specifications. The tag will indicate the cable number and destination.
- Cables installed on cable ladder will be secured by approved cable fasteners. The cable cleating will have adequate strength to support the cable during fault conditions.
- Saddles and fixings for securing multi-core cables to the cable tray system will be of the approved type, with the maximum spacing of 150mm. Single core cables installed on cable trays will be secured by the approved cable fasteners
- Internal Bending Radii of Power Cables: as per specifications/manufacturers recommendations
- At each joint or termination, a non-ferrous label shall be fixed to the cable giving size and identification of the cable.
- Cable trays as per approved material will be connected to the MV-LV equipment via appropriate wiring accessories
- Reduction in the number of strands of a cable core will not be allowed at a cable joint or termination.
- Where a compression joint is made, the appropriate tools specified by the manufacturer of joint connectors will be used. The compression joints will be made by inserting the cores to be jointed into the opposite end of a compression jointing coupling.
- Cable support bracket will firmly clamp the incoming cable at a suitable distance from the termination.
- MV cable terminations will be carried out in strict accordance with the termination manufacturers instruction leaflets and great care shall be taken to ensure that terminations and equipment remain clean and free from contamination during the terminating process.
- Final testing of MV cables will be by the supplying authority prior to energization.
- Final testing of LV Cables with be by the client as per specification / contract requirements. Testing will normally consist of installation and continuity checks for phase and neutral conductors.
7. BUS BAR TRUNKING INSTALLATION
- BUS bar trunking will be installed as per the approved construction drawings and manufacturers shop drawings and details.
- BUS bar trunking support system shall maintain the trunking in both horizontal and vertical plane without stress on the Joints.
- Both joints and final connections of trunking will be torque tightened to manufacturer’s recommendations.
- Final testing as per clause 6.15 of this method statement.
8. Safety and Environmental Consideration
In ordered to ensure that all final electrical connections to MV-LV equipment workers to takes place in a safe manner, contractor will consider the suitability of: –
A- The workers
B- Work on height
C- Power tools
D- Cable drum setting
A- The workers
- The workers is to be trained and certified for the job.
- The workers must be healthy.
- The workers must be trained for safe working.
- Personal safety equipments will be used all the time.
B- Work on height
Mobil tower scaffold
- Stand or erect towers on a firm base or level ground
- Brakes on castors are always using
- Secure the tower to the structure if necessary by ties
- Inspections the towers will be done regularly by competent persons / safety officers
- OnlyLouisvillewooden step ladders type are allow to use
- Unsound ladders never use
- Lean sideways from ladders is forbidden
- Ties to be fitted all the time with right length
- Regular inspections will be done.
C- Power tools
- Only earthed tool allow to used
- Damaged tool is not allow to use before repairing
- All electric staff must be in good shape
- The power tools will be regularly inspected by competent persons
D – Cable drum setting
- Cable drum set must be made form good strong steel
- The shaft must be strong enough for the weight
- The stand’s height must be correct
- Braking system for the drum will be advise
- Communication between working group will take place.
Inspection Check Lists for:
- Cable Ladder/Tray
- Cable Installation
- Mv test on cable
- LVtest on cable
- LV test of trunking
10. REFERENCE DOCUMENTS
- Latest Rev Approved Construction Drawing.
- Plant Equipment – Manufacturer’s Instruction & Wiring diagrams.