IEEE Power & Energy Magazine - July/August 2019 - 20

substation results in a smaller physical
footprint and adds additional flexibility
to the assets. Gathering data from the
substations is also expected to deploy
even more DERs by being better able
to visualize the local needs and drive
investment strategies by various stake
holders. Relevant issues around cybersecurity and workforce development are
also discussed because they will influence the adoption rate of new technologies by investor-owned utilities.
The fourth article, by Dirk Van Hertem, Willem Leterme, Geraint Chaffey,
Mudar Abedrabbo, Mian Wang, Firew
Zerihun, and Mike Barnes, brings to the
forefront the discussion around dc technology and its application in substations of
the future. The authors begin by describing applications of two current converter
station technologies: line commutated
converters (LCCs) and voltage source
converters (VSCs). High-voltage (HV) dc
applications have grown to meet the need
for the bulk energy transfers from generation sources to population centers, as is

evident in China, India, and Latin America. HVdc technology also supports the integration of large-scale renewables, such
as offshore wind resources that are primarily connected through underground/
subsea cross-link polyethylene cables. The
discussions on ac/dc conversion equipment highlight the challenges surrounding propagation of fault currents and the
equipment that can be used to interrupt
fault current at the converter. An examination related to dc circuit breakers and
switchgear is followed by various mechanisms that can be utilized for dissipating
excess energy. The development of new
dc power-flow control devices enables use
of the full capacity of the power system
network, but it could increase the land
area requirement for substations. Secondary equipment, such as nonconventional
instrument transformers for dc voltage
measurement, is also being developed
and is expected to support the development of dc substations.
In the context of grid control for stable
operations, the authors talk about the po-

tential to employ a voltage droop scheme
at the substation level utilizing a grid
controller concept. Increased integration
of intelligent electronic devices using the
IEC 61850 protocol and other standards
for communication and teleprotection for
the dc substations will also need higher
bandwidth and communication speed,
which will require us to rethink how we
deploy communication networks. This is
expected to lead to the development of
digital platforms for dc grids, echoing the
message we heard from Hunt et al.
Considerations for dc substation design, influenced by the choice of substation technology, bus bar design topology,
and protection philosophies, are also detailed by the authors. Offshore dc substations primarily use VSC technology,
which requires a smaller footprint and
lower installation costs than LCC installations. Other considerations for offshore dc
substations relate to weather conditions,
implementation logistics, spare part philosophies, access to substations, and revenue loss analysis that takes into account

http://www.nuscalepower.com

IEEE Power & Energy Magazine - July/August 2019

Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - July/August 2019