Cable and Wiring

Burnt cable

Raceway exposed to sun

• Narrow cross section or excessive length causes resistance heating.
• Exposed to direct sunlight or other heat sources.
• Short circuit or ground fault.
• Overloaded busbar. K-rated transformer can reduce harmonics.

• Comply with the requirements of electrical installations as per BS 7671:2008+A3:2015, SS CP 5:1998, NFPA 70 [5]; including the location and number of power points.
• Ensure switchboards have adequate space and access for operation and maintenance.
• Specify suitable switch closets with regard to moisture exposure conditions.
• Refer to the definition of types and functionality of RCCBs and specifications for RCBOs as per SS 480:2016 (IEC 61009-1:2010+AMD1:2012+AMD2:2013 CSV BS EN 61009-2-1:1995).
• Provide sub-metering system with remote measurement capability and link to BMS/EMS to track energy consumption data trends [6].

Construction

• Conform to the guidelines for construction and compliance inspection of electrical connections and earthing thereof (BS 1363-4:2016, SS 403:2013).
• Refer to BS 8512:2008 for storage, handling and installation of power cables on wooden drums.
• Install sub-metering system with remote measurement capability and link to BMS/EMS to track energy consumption data trends [6].
• All accessible metal parts of connection units should be in electrical contact with the earthing terminal(s) (BS 1363-4:2016, SS 403:2013).

• Maintenance

• Conform to the maintenance of electrical installations as per BS 6423:2014, BS 6626:2010, SS 538: 2008, [3;7].
• Check for insulation damages (e.g. cracks, blisters, warping) caused by overheating, physical impact or by spillage of cleaning chemicals.
• Check for potential short circuits or ground faults. Ensure that switchboards are not exposed to direct sunlight or alternative heat sources.
• Conduct annual shutdown to eradicate hot spots along the distribution network as witnessed by the owner and certified by a Licensed Electrical Worker (LEW).
• Provide necessary warning notices/labels at switchboards (e.g. shock hazard warnings).

Corroded light fittings due to poor indoor environment regulation

Corroded metal conduit

Corroded busbar trunking

• Water seepage due to poorly designed / finished joint.
• Use of unsuitable lubricant, pulling or cleaning agent.
• Lashing water jet for cleaning enters through end / joints not properly designed or sealed.
• Adjacent structure is not water resistant.
• Galvanic corrosion.

• Intermediate (junction or pull) box – not made of rust proof material.
• Knockouts are made using improper tools or methods. Should be done before mounting.
• Knockouts are made forcefully big to accommodate too many cables.
• Screw / cover missing during careless installation or maintenance.

Worn insulation

• Softened from prolonged exposure to high temperature (>70°C)
• Use of unsuitable lubricant, pulling or cleaning agent.
• Narrow cross section or excessive length causes resistance & heating.
• High inrush current from short circuit or ground fault.

• Movement or dangling if support is not secured or insufficient.
• Broken / loose supports from excessive corrosion.
• Excessive tension – careless workmanship.
• Too close to structural frame or no hangers to allow movement. Damage is more prominent in absence of expansion joint or open run.
• Inadequate protection from crush, impact or abrasion.
• Sharp or too many bends, pulled over excessive length. Intermediate junction / pull box can solve such problem to a great extent.
• Nicks during careless cutting results in broken wire beneath the cover.
• Damaged during maintenance of other services running too close / interfering. Result of poor planning.
• Conductor not firmly secured – pulsating current causes sway.
• Missing cover of junction/ pull box (H17) encourages vandalism. Esp. if the cables can be pulled easily due to gap between cable and knockouts.