4. These stresses cause
the ageing the cable insulation, impacting its
dielectric and mechanical properties, and thus
the reliability the cable. But the standards support
such compatibility and ensure the reliability of
MVDC infrastructure not yet exist. Early results suggest
that MVAC cables may age differently from MVDC
cables, that insulation materials behave differently
in and [46]. this case, voltage can
cause polar impurities originating from the
insulation itself, neighbouring layer, from the
environment migrate under high electric
field, leading non-homogeneous mechanical
and electrical properties within the cable and
accelerating ageing.1 Voltage
Selecting the appropriate voltage level MVDC
system significantly impacts the system’s overall
efficiency, stability, safety and scalability. applications often involve
independent qualification type-testing of
accessories, with compatibility determined by
industry standards.
For example, and cables use polymeric
insulation that subject electrical, thermal, and
environmental stresses. However,
this integrated approach less common in
MV systems. particular, the electrical performance
of infrastructure such cables under conditions
of prolonged MVDC stress has yet fully
examined.82, Medium Voltage Cable
System Requirements, has recently been
established examine requirements for MVDC
cable systems.6.
CIGRE B1. The thermal behaviour accessories
under conditions can also deviate from AC
conditions, affecting the ageing process. The electric field distribution
within these accessories different and DC
applications, causing varying degrees stress
on insulating materials, potentially accelerating
degradation.
.
4. Key considerations the system design
stage are listed below.
In HVDC systems, cable accessories are typically
designed and tested integral components a
complete, pre-qualified cable system. However, higher voltage
requires enhanced insulation strength for the
equipment, leading greater device size and
cost.39
MVDC technologies and operational considerations
maintain constant polarity, resulting unique
electrical field distributions and stress accumulation
within the insulating materials. Higher
voltage results lower power losses and
enables implementation efficient long-
distance transmission.6 System design
Bringing all the components and technologies
described into the previous section into reliable,
cost-effective MVDC system the role system
design. This fundamental
difference might impact reliability and long-term
performance cables and related infrastructure. Voltage selection the
basis for all associated equipment and therefore a
crucial decision point system design. This work expected include
consideration materials and where DC-specific
materials and accessories are required. Ultimately, such accumulation
can increase electrical stress and premature failure.
An example different ageing characteristics
under the phenomenon space charge
accumulation. therefore imperative perform
conductivity assessments, space charge
measurements and accelerated ageing stresses of
MVDC cables and related infrastructure.
These ageing effects are less understood MVDC
systems due their relative lack operational
history.
The difference between and systems
might also affect the ageing and/or reliability of
MVDC cable accessories such terminators,
joiners and insulators. Voltage
varies depending transmission distance and
load characteristics and acts key element
in minimizing power loss. should
include the following factors:
§ Transmission distance and capacity
