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58 Planning the electrical installation
Not allowed power cable types
PVC
EMT
PE
Generator cable shield
If the generator cable shield is used as the sole protective earth conductor of the generator,
make sure that the conductivity of the shield is sufficient. See subsection
above, or IEC 61800-5-1.
To effectively suppress radiated and conducted radio-frequency emissions, the cable shield
conductivity must be at least 1/10 of the phase conductor conductivity. The requirements
are easily met with a copper or aluminum shield. The minimum requirement of the generator
cable shield of the converter is shown below. It consists of a concentric layer of copper wires
with an open helix of copper tape or copper wire. The better and tighter the shield, the lower
the emission level and bearing currents.
1
1
Insulation jacket
2
Helix of copper tape or copper wire
3
Copper wire screen
4
Inner insulation
5
Cable core
Single core vs multicore cables in grid cabling
￭
Use symmetrical grid cabling. Asymmetry leads to unequal current distribution between the
conductors which may cause disturbances and fault trips. To avoid asymmetry, use
symmetrical multicore (three-phase) cables where possible. Single core cabling is also
allowed if the cables are grouped symmetrically.
The table below shows three possible cabling options.
A four-conductor system (three phase conductors and a PE conductor in a PVC
conduit)
Corrugated cable with three phase conductors and a protective conductor or cable
in EMT conduit
A well-shielded (Al/Cu shield) four-conductor system (three phase conductors and
a PE conductor or four conductors)
Symmetrical shielded cable with individual shields for each phase conductor is not
allowed on any cable size for grid and generator cabling.
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3
4
General rules
5
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