COST OF A FAULTY PULL
Any contractor who has been on the jobsite during a difficult wire pull can attest to the frustration of a cable fault. You’ve spent hours pulling multiple parallels only for the Megger to show a faulty reading, resulting in overtime to replace and repull the damaged cable. This can have significant financial implications on your bottom line, putting you over budget and behind schedule.
Unfortunately, this is a common problem for installations that use cables with subpar insulation. Even the smallest nick in a cable during the pull can lead to outer sheath damage and a short circuit fault.
CABLE FAULT CAUSES
Cable fault occurs when the insulation of a cable has been deteriorated or damaged in some way that prevents it from being able to contain the electrical current. This can be caused by damage during installation and handling, environmental conditions (such as excess moisture, grit, or other contamination), or accelerated aging or corrosion of the cable's insulation or inner conductors.
QUALITY INSULATION IS KEY
To prevent cable faults, it is important to select cables insulated in materials that are built to last. XHHW-2 (RW90), for example, is made of crosslinked polyethene (XLPE), a thermoset insulation. XHHW-2 (RW90) is tougher and more resistant to environmental breakdown and abrasions than cables like THHN/THWN (TW75N or TW90N) that are made of thermoplastic PVC insulation.
When installing multiple single conductors, the higher pulling tension required and possible jamming in conduit bends can lead to insulation damage that adversely affects the conductors. Cabled conductors that limit contact between the cable's insulation surface and the conduit can reduce damage during a pull.
Contractors should take advantage prefab, twisted cable solutions made of XLPE insulation to prevent cable faults. This construction is designed to better withstand the tugging and pulling required during cable installation.