IEEE Power & Energy Magazine - March/April 2014 - 52

Implementing smart grids is central to the transition
to a low-carbon economy, and DSOs are key players
in this transition.
defines its own provisions regarding, for instance, support
for renewable energy.
in most european countries, intermittent generation is
developing very quickly, leading to a total current installed
capacity of 106 GW of wind and 70 GW of PV in europe.
The vast majority of these plants are connected to distribution
networks. Together with the development of active demand
and electric vehicles, this will lead to a deep transformation
of the role of dsos.

Active Distribution System Management
With the eu well on its way to meeting a 20% target for
renewable energy sources (ress) in total energy consumption by 2020, the share of electricity supply from ress is
on the rise. A large proportion of these resources, including
intermittent solar and wind, will be connected to low- and
medium-voltage distribution networks. in fact, Germany,
ireland, and spain are already experiencing a high penetration of such generation. in addition to this, e-mobility, local
storage, and demand response will all affect the distribution grids heavily. The operation of this future system will
become more complex since significant power will flow not
only from the power system to the customer but also from
the customer to the power system. Problems like excessive
voltage variations and bottlenecks will occur more frequently. Technical limits will be breached, requiring additional investments in network reinforcement and in more
sophisticated protective relaying and control systems.
Today's distribution networks are designed to meet peak
loads. The current "fit-and-forget" approach implies that all
issues are resolved up front, at the planning stage; the shift to
more decentralized power production and new applications,
however, means that this approach alone is not cost-effective.
Peak demand occurs for only a limited number of hours per
year, and the utilization rate is declining. in addition, the priority
grid connection and access granted to ress contributes to inefficiencies in grid development. decentralized generation, flexible loads, and storage offer the potential for greater flexibility
within the grid, but the current approach to grid design means
that this potential cannot be used.
The european dsos believe in promoting active system
management, which could optimize the distribution network
by allowing greater interaction among the key network processes-planning, connection and access, and operation-
which take place within different time frames. Greater
flexibility, on both the supply side and the demand side,
will represent a key tool in this respect. While traditional
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network reinforcement will remain important, such flexibility would help optimize the use of the existing network and
thereby minimize distribution grid extensions. To make this
paradigm change happen, the active involvement of customers is a must. in addition, dsos need to play a more active
role, and their networks must evolve facilitated by the right
tools to allow them to comply with their fundamental tasks
of maintaining reliability of supply and quality of service.
in november 2012, edso for smart Grids (edso) listed
the key elements of active distribution system management:
✔ A variety of network planning and access options
that would reduce the need for investment: longterm network planning would let dsos prevent bottlenecks in the most cost-effective way. To this end,
coordination among all relevant actors, particularly
transmission system operators (Tsos) and dsos, will
be important. new types of network access could also
help reduce network investments. Variable network
access contracts could be one such option. in addition,
alternatives involving close-to-real-time operation
should also be investigated.
✔ An adequately designed connection requirement
for distributed generation (DG): dG resources must
fulfill certain technical criteria without which they
cannot be properly integrated into the network: they
must be able to resist voltage dips and prevent islanding. separate metering for production and consumption should be provided.
✔ A new role of services in distribution grid operation: dsos should be able to obtain flexibility from
dG resources and consumers to solve grid constraints. This could result in new market mechanisms:
so-called flexibility platforms. To manage the operation of distribution systems, basic system conditions
should be defined, as is the practice for transmission
networks today. A "traffic-light" scheme could be
used to select the actions appropriate for various system conditions. under normal "green light" conditions, dsos would operate using market procedures.
in insecure "yellow light" states, the dso would use
a set of market-based procedures to incentivize grid
users to adapt production and/or consumption to the
grid situation. Finally, in well-defined emergency
"red light" conditions, the dso should be able to
undertake direct load management or emergency dG
curtailment after the contracted options have been
exhausted. The increasing share of dG and flexible
march/april 2014

Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - March/April 2014