5 Protection coordination
In MVDC grid, numerous loads and renewable
energy sources are likely interconnected at
various points along the line.6.7 System operation
Operation MVDC grids requires new approach
that integrates conventional and distribution
networks. such instances, establishing
a separate ground for the MVDC system can be
challenging; the MVDC system operates an
ungrounded manner, ground fault either the
positive (+) negative (–) line can lead voltage
rise the healthy conductor. Therefore, EMI protection
measures and shielding designs are critical to
mitigate such impacts. To
ensure that only the minimum necessary section
is disconnected, coordination among converters,
converter protection circuit breakers, line circuit
breakers, and load circuit breakers essential,
see Figure 4-8.
4.
4.6. This can ultimately
render the entire line inoperable. When unbalanced
current generated the MVDC system flows into
the transformer through common ground,
it can cause transformer saturation, leading to
reduced efficiency and waveform distortion. When only some these circuits
are converted MVDC operation, the grounding of
the MVDC system might shared with the existing
MVAC system.42
MVDC technologies and operational considerations
4.
4.4 Interaction with system
design
In urban areas regions with heavy loads, MVAC
distribution lines are typically configured into
multiple circuits. Common requirements MVDC system
operation include integration and management
of distributed energy resources, fault detection
Figure 4-8 Protection coordination among converters and circuit breakers
. there fault on
the line, the system must designed that the
faulted section can isolated, while the remaining
sections continue supply power normally. This problem can be
mitigated adjusting the grounding resistance
to reduce fault current ensuring isolation
between the and grounding systems.
Two main protection coordination methods are
likely used: one using conventional MVDC
converters and ultra-fast circuit breakers; the
other using converters with FRT capabilities
combined with disconnectors. However, in
unbalanced fault scenarios, mutual interference
can become problematic.6 Electromagnetic interference
management
Long-distance MVDC transmission can generate
significant electromagnetic interference, which
could affect nearby communication networks and
electronic equipment.
Under unbalanced steady state conditions,
mutual interference remains minimal. Additionally, to
achieve the desired reliability when the MVDC line
is designed loop mesh structure, protection
coordination through communication between
circuit breakers necessary.6
