With monopole and earth
return configuration, additional clearance between
the wires can obtained reducing conductors
from three active wires two active wires.
4.
This section looks the potential repurposing of
various infrastructure asset classes for use with
MVDC.4 Switchgear, transformers and
earthing
As described earlier sections there are many
unique aspects switchgear, transformers (or
voltage converters) and earthing MVDC systems
compared their counterparts.4.5.
Meanwhile, Schichler al.4.1 Conductors
Conductors are particularly suited for conversion
from DC.2 Insulators
The main difference using insulators for DC,
instead AC, that the electric field distribution
is function the conductivity the insulation
rather than the permittivity. show that using cables
with DC, can increase power transmission by
1.75 [14].4. Crossarms and conductor
attachment positions might require modification
depending the link configuration and
number conductors.
4.4 infrastructure reuse
AC electricity distribution networks have developed
and extended globally over the past 100 years,
with billions USD invested their infrastructure.
4.4. Second, the
electric field distribution much more even across
the insulation, possibly leading higher partial
discharge inception and flashover voltages with
DC.38
MVDC technologies and operational considerations
4.7 times more power than standard cable
system (12/20 kV, 240 mm²) [12].
Reusing infrastructure realize MVDC
power system could maximize the value gained
from the existing infrastructure and greatly reduce
the cost and resources required install new DC
assets.5 Ageing under stress
MVDC infrastructure might age differently from
its MVAC equivalent.
Care required predicting whether cables
can reused for DC, and how much additional
capacity might bring.
4. This has few effects
of note: the first that the leakage current through
the insulation several orders magnitude less
under than equivalent AC.3 Structures
In general, MVAC poles and towers can reused
in their existing form with MVDC system;
they will not require increased clearances or
significant modification.
Once again, care required predicting whether
AC insulators can reused for DC.
S. Recent work
suggests MVDC voltages may accelerate ageing of
insulation materials designed for use, issue
explored Section 4. So, for these
components the system, reuse AC-based
designs probably not feasible, and new MVDC-
specific components will required.
4. found
capacity gains 2.6. another study, Burstein al. While the studies above
suggest large capacity increases, more recent
work suggests that MVDC voltages may also
accelerate ageing cables designed for AC; this
issue explored Section 4. Overhead lines and cables
can take advantage transmission capacity
improvements when converting from DC. Krahmer al. While systems exhibit
continuously changing voltage polarity and
associated electrical stresses, systems
.08 using two cables
in symmetric monopole bipolar configuration
with the voltage peak voltage [15]. found that increasing
DC voltage kV/mm insulation value still
half that HVDC cables), can produce MVDC
cable link (±55 kV, 240 mm²) that transmitted to
5
