/images/TDUpdate2.gif/images/southwire_100x70.jpgSpacer Cable Eases Right-of-Way Squeeze - 2008SpacerCableEasesRightOfWaySqueezeFeb2008.htmSometimes a right-of-way is a tight squeeze for a distribution circuit. If you’re running a 25kV line down an urban alleyway, there simply may not be room to leave safe clearance around bare conductors on insulators. Spacer cable can help you out.
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Spacer Cable Eases Right-of-Way Squeeze - 2008

Holding distribution conductors in close – but safe – proximity lets engineers put circuits in tight quarters.

Sometimes a right-of-way is a tight squeeze for a distribution circuit. If you’re running a 25kV line down an urban alleyway, there simply may not be room to leave safe clearance around bare conductors on insulators. Spacer cable can help you out. “Southwire can help you with all the accessories and know-how you need to simplify a spacer-cable project,” says Joe McAuliffe, Southwire senior engineer.

Save space and reduce tree problems

Spacer cables are groups of three covered conductors separated by tough, high-density polyethylene spacers that hold the conductors about 12” apart. Placed about every 30 feet on a span, the spacers are supported by a steel messenger wire. The messenger wire also serves as a ground conductor. Hanging a spacer cable bundle on each end of a cross arm can give you two circuits going into an area instead of one.

Spacer cable itself is a single aluminum conductor protected by a layer of track-resistant polyethylene (TR HDPE). The covering resists tracking at distribution voltages up to 46kV, and it prevents direct shorts if a tree limb brushes the wire. Where overhanging trees are common, spacer cable can increase service reliability compared to bare overhead conductors, at a lower cost than underground installations.

Proper accessories are important

Because spacer cable is not shielded, it’s important that spacer cable accessories have a dielectric constant that’s compatible with the cable covering. HDPE typically has a dielectric constant around 2.3 - 2.4. Porcelain insulators typically have a dielectric constant around 5. Mismatch of the dielectric constant invites partial-discharge conditions that can eat away the covering. Then traveling waves from lighting strikes may cause destructive arcing at the covering’s weak point.

“The polyethylene insulators are also useful in some standard overhead conductor distribution applications,” says McAuliffe. In areas where vandalism is a problem, polyethylene insulators are resistant to shattering when shot at. Polyethylene insulators also reduce inventory losses due to breakage in warehouses or in transit, compared to porcelain.

Southwire spacer cable is available in 5kV to 46kV constructions, with conductor sizes from #4 AWG to 795kcmil. These non-shielded, covered conductors should be handled like bare conductors during installation and operation.

Get complete spacer support from Southwire

The key to an easy spacer cable installation is ready access to the proper accessories and know-how. In addition to appropriate spacers, Southwire supplies a complete line of supports, arms, brackets, clamps and pin insulators that guide the spacer-cable span around bends. Southwire’s ratchet-lock spacers cut conductor installation time by eliminating separate ring ties that can be dropped or broken in the installation process

McAuliffe concludes, “Spacer cable can deliver cost-effective solutions to common application problems. And you can get everything you need for the installation – including expert engineering advice – as a part of Southwire’s family of transmission and distribution products.”