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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
General rules
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
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.
2
3
4
5
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