Tips to Identify Copper Clad Aluminium (CCA) Cables
18 января 2017 г. / General
So you came across some Category 6 cable available online for practically half what you've been paying for that brand name. It claims TIA-568-C compliance, includes the UL listing mark and even has a ETL verification legend printed right on the cable. Before you get too excited, you might want to make sure that cable isn't made with copper clad aluminum (CCA).
Less expensive than using solid copper, cables made with CCA conductors are simply not worth the risk. Not only are they non-standards compliant, but they often do not have a valid UL safety listing per the National Electric Code (NEC).
What about that UL mark on the box? If the cable is made with CCA and claims standards compliance, it could be counterfeit cable, and that means the UL mark is likely unauthorized. UL listed cables got their safety listing because they passed strict flame spread testing to reduce the spread of fire. If the UL listing is fake, there's a chance the safety is too.
A Hot Balancing Act
While the biggest concerns surrounding counterfeit CCA cables should be the safety risk, these types of cables can significantly reduce network performance--especially with the increasing use of PoE to power everything from phones, laptops and Wi-Fi access points, to video surveillance cameras, digital displays and even LED lights.
The resistance of an aluminum cable is about 55% greater than for a copper cable of the same diameter. This means more heat generated within CCA cable and lower voltage available at the end device. So not only is there a chance that the end device won't have the power it needs, but heat rise within cable bundles also leads to increased insertion loss since signals attenuate more in proportion to temperature.
It's not just the heat that causes problems. When power is delivered, it is split between each conductor of a pair. If the resistance of the two conductors is equal, the DC Resistance Unbalance (the difference in resistance between two conductors) is at zero, current is split evenly, and common-mode current is achieved. But this is rarely the case with CCA cables.
While good workmanship and consistency in termination is important to preventing DC Resistance Unbalance, the variations in the diameter, concentricity (roundness), contour and smoothness found in CCA cable causes a higher risk for unbalance that distort the waveform of Ethernet data signals. The result is greater bit errors, retransmits and even non-functioning data links.
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That's Why You Test It
There are a few tips for identifying CCA cables that include scraping the conductor to reveal the silver colored aluminum beneath the copper cladding and even weighing the box since aluminum is lighter than copper.
Cutting cable and scraping conductors isn't exactly the preferred method if the cable is already installed and the customer isn't pleased with the performance (especially if CCA cable turns out NOT to be the problem). And there have been reports of ballast being placed in cable boxes or counterfeiters using heavier versions of CCA to match the weight of real copper cabling.
Then there's testing. Not only is it important for verifying standards compliance and application assurance, but it also might help detect CCA cable. Fluke Network's DSX-5000 CableAnalyzer has the ability to test for DC Resistance Unbalance, verifying that both conductors in a pair have equal resistance to enable common-mode current and effectively support PoE while avoiding distortion of the data signals transmitting on the same pair.
When testing a CCA cable, Fluke Networks found the DC Resistance Unbalance to be clearly out of specification, and data suggests that CCA fails DC Resistance Unbalance regardless of link length. Besides, as the number of devices simultaneously running gigabit Ethernet and PoE continues to rise, and as the amount of power delivered via PoE increases, field testing of DC Resistance Unbalance becomes even more important--for all cables. Click here to read more about the importance of testing for DC Resistance Unbalance in PoE applications.