Part B - Certificates and approval requirements 
23 
3.4.3.2 Magnetic fields 
3.4.3.2.1 Alternating current 
With three-conductor cables, the magnetic fields almost cancel one another out. The limit value of 100 
pT at 50 Hz required by BlmSchV for areas in which people stay for long periods is thus complied with, 
without restrictions. The same applies for coaxially operated three-phase single-conductor cables as 
well as for three-phase single-conductor cables operated in a bipolar arrangement. 
When non-stranded cables are used, it is necessary to demonstrate that they have been laid in accord 
ance with BlmSchV. 
3.4.3.2.2 Direct current 
The magnetic fields almost cancel one another out when bipolar cables are used. The limit value of 
400 pT at 0 Hz for areas in which people stay for long periods, as required by BlmSchV, is therefore 
complied with without restrictions. 
When monopolar cables are used, it is necessary to demonstrate that they have been laid in accordance 
with BlmSchV. 
3.4.3.3 Heat loss from power cables 
The limit temperature of 2 K suggested from a natural protection perspective applies in the EEZ of the 
North Sea and Baltic Sea for a reference point depth of 20 cm. 
A calculation method shall be used that has its starting point in the time average of the cable losses, and 
goes on from here to calculate the time average of reference point heating. IEC 60287 can be used as 
the relevant calculation method for this. To take account of full-load phases of wind farms lasting several 
days, transient heating is superimposed on this average reference point heating (this transient heating 
resulting from a jump in cable losses from the time average to their maximum value). This transient tem 
perature curve can be calculated with reference to IEC publication IEC 60853-2 £38]. f391 demonstrates 
that both calculation methods suggested by IEC for cable technology are equivalent to the significantly 
more complex FE method for all boundary conditions in question. 
When calculating the time average for cable losses, it is necessary to consider the parameters of the 
connected wind farm, the mean wind speed of the location and the resulting wind farm output. For 
three-phase cables in addition, this time average is also determined by parameters of the transmission 
system. For example, the length of the cable route has an influence on the capacitive currents supplied 
into both cable ends, while the installation of compensation systems has a decisive influence on this 
as well. A magnitude of 0.7 km/W (T401. f411. £42], f43T) is not exceeded as specific thermal resistance 
values for water-saturated soils. 
3.4.4 Cable laying and construction site safety 
There are no (inter)national regulations on cable laying and repair. For this reason, this standard relies 
on relevant experience. With regard to safety provisions, reference is made to the relevant international 
and national safety regulations, and in particular to strict compliance with BGV C23 F441 in particular due 
to the high risk potential for diving work.