Tech Briefs Magazine - October 2021 - 13a

SIMULATION-BASED PRODUCT DEVELOPMENT
FIGURE 7  
   
        
      
real μ-value that has been fitted to
experimentally obtained material
data by considering only the average
H-field in the armor wire, not the local
one. Therefore, the permeability is not
nonlinear or imaginary. Instead, it is
set to the correct value for the average
armor wire H-field, given the particular
operating point of the cable. Once
the solution has been obtained, the
losses can be computed afterward as a
postprocessing step. This is because from
measurements,
they know precisely
what losses they
get for a certain
field intensity. So
in their models, the
hysteresis losses
are not electrically
linked to either
the voltage or the
current response of
the cable.
To get the
correct effective
permeability, the
team ran the 3D
model for different
μ-values for each
modeled current.
They calculated
and averaged the
H-values from each
solution and took
into account the
reduction in armor wire cross section,
when using coarse meshes. Then, the
μ-values and average H-values were
plotted on the measured μr
All of the modeling in the world will not
matter, however, if the results of the model
do not accurately represent the physics of
the device in reality. To make sure that the
simulation results for the cable analyses are
accurate, Thyrvin and his team validated
them with the existing cable data. When
computing the armor losses of the cable,
they found that the modeled results were
within 3% of the losses measured from
cables experimentally (Figure 8). While
that sounds impressive in itself, these
results are actually more accurate than
the IEC standard for the type of cable
being modeled, in which the total loss
differs between 10-30% compared to
measurements.
» PUTTING TRUST IN
CABLE ANALYSES
(H) wire curve.
The team found that higher μ-values
meant lower average H-values in armor,
and vice versa. Finally, the intersection of
the curves with the measured one gave
the correct effective value at the cable's
operating point (Figure 7).
The validated results of the 3D cable
model proved to NKT that simulation is
a reliable and trustworthy way to study
cable designs. This knowledge has had farreaching
effects for the organization. For
one, they feel confident studying cables
without comparing to measurements
each time, because they have already
confirmed that the simulations are
accurate based on the previously validated
results. " We can now simulate instead of
measure, " says Thyrvin. " You can simulate
before making, but you cannot measure
before making. " Now, with simulation
software, NKT knows how large the losses
are in a cable before manufacturing,
based on the simulation analyses.
FIGURE 8      
     
REFERENCES
1. " Wire and Cable Market (Type - Wire, and
Cable; Voltage Type - Low Voltage, Medium
Voltage, and High and Extra High Voltage;
Applications - Power Transmission and
Distribution, Transport, Data Transmission,
Infrastructure): Global Industry Analysis,
Trends, Size, Share and Forecasts to 2024 " ,
Infinium Global Research, 2020.
2. M. Ardelean and P. Minnebo, " HVDC
submarine power cables in the world " ,
Institute for Energy and Transport, pp.
50-51, 2017.
3. G. White, " Insurance and Risks in the
Underground Cable World " , SubOptic, 2013.
4. D. Willen, C. Thidemann, et al., " Fast
Modelling of Armour Losses in 3D Validated
by Measurements " , 10th International
Conference on Insulated Power Cables, C74,
2019.
COMSOL NEWS 13a
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» VALIDATING THE CABLE
MODEL RESULTS
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Tech Briefs Magazine - October 2021

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