R&M Data Center Handbook

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Results in accordance with EN 61000-4-4 (left) / Results operational test “mesh cable tray” (right)
The figure left shows the results of this test. All shielded systems allow the use of 10GBase-T in all environmental
conditions (E1, E2, E3). At the same time, higher quality shielding provided better immunity against fast transients.
High-quality unshielded cabling allows the use of 1000Base-T in an office environment. For an industrial environment
and for 10GBase-T, shielded cabling is necessary. Unshielded cabling, if it is to support 10GBase-T, needs
additional protective measures such as the careful separation of the data cables from the power cables.
A double-sided ground improves the immunity of shielded cabling against external fast transients above the
minimum requirements of the standard. If the shield is not continuous, its effectiveness with 10GBase-T is
negated, and the protection is then the same as with unshielded cabling. At lower frequencies (such as used in
1000Base-T), a certain protective effect of the non-continuous shield is apparent, especially with double-sided
grounding.
An operational test with fluorescent lamps that were located 0.5 m from the data cable showed that the test
conditions in the test based on the standard were entirely realistic. The interference that arises when a fluorescent
lamp is switched on influenced the 10GBase-T data transmission in the same way as during the test according to
the standard. Not only the lamp itself, but also the power cable to it, created interference. It must therefore be
ensured that there is sufficient separation of both from the data cabling.
In order to compare the standard test using the coupling clamp to an actual installation situation, the “mesh cable
tray” experiment was also carried out. The data cables and a power cable were laid in a mesh cable tray with a
total length of 30 m and with a constant separation from 0 to 50 cm. The interference signal according to the standard
was then applied to the power cable. The figure shows the results of these measurements. A comparison of
the results with those of the test according to the standard from the figure shows that the standardized test
simulates a separation of the cables of approximately 1 - 2 cm. In order to guarantee the operation of 10GBase-T,
a separation between the data and power cables of at least 30 cm must be maintained with an unshielded system.
The shielded cabling met the requirements even without any separation between the cables.
According to EN 50174-2, a separation of only 2 cm is defined for the unshielded system in this configuration,
which however is insufficient for 10GBase-T. In other words, with unshielded cables, when using 10GBase-T, a
far greater separation must be maintained than is defined in the standard.
A further test in accordance with EN 61000-4-6 was carried out to check the system’s immunity against conducted
RF interference in the range from 150 kHz to 80 MHz on power cables located nearby. Power cables can act as
antennas for high-frequency interference coming from external sources (such as shortwave and VHF transmitters)
or also intentionally subjected to a powerline signal. In this test, too, the previously mentioned coupling clamp was
used. The stress levels were chosen in accordance with the MICE table (see Figure, “Conducted high frequency”).
The results corresponded to the well-known pattern that the shielded cabling meets all requirements for 10GBase-
T. Unshielded cabling meets the requirements for offices and areas with light industry for 1000Base-T, however
for 10GBase-T transmissions additional protective measures such as increased separation of the data cabling
from power cabling is necessary.
Immunity from magnetic fields arising from power cables
This test in accordance with EN61000-4-8 checks the ability of a system to function in the presence of strong
magnetic fields at 50 Hz. These magnetic fields can be generated by power lines (cable or busbars) or powerdistribution
equipment (transformers, distribution panels). The stress levels were selected in accordance with the
MICE table (see Figure, “Magnetic fields”). All cabling fulfills the highest environmental class (E3) with both
1000Base-T and 10GBase-T. No difference was determined between the susceptibility of shielded or unshielded
cabling. No heightened susceptibility of the shielded cabling based on ground loops can be observed.
R&M Data Center Handbook V2.0 © 08/2011 Reichle & De-Massari AG Page 153 of 156