IEEE Power & Energy Magazine - May/June 2017 - 37

An alternative approach is inserting autotransformers
in the middle of the problematic MV lines to correct
these contrasting voltage levels.
facilitate implementation (e.g., generator design and use of
public telecommunication infrastructure).
The tradeoff between grid expansion costs and curtailed
energy costs should be analyzed. To incorporate new DRESs,
it is often more efficient to reduce generation in critical
moments than to reinforce the grid. A fix curtailment for
PV installations, limiting the maximum injection to 70% of
nominal power, can lead to an energy curtailment of between
3 and 7%, which is acceptable, taking into account that it
produces around a 40% HC increase. When applied to wind
farms, a fix curtailment of 70% of nominal power can lead to
higher amounts of energy curtailed (above 10%) and, consequently, a higher economic impact on generators, for similar
results in terms of HC.
In France, a new nonfirm connection contract will allow
the curtailment of production during a few days a year, with
the benefit of a lower connection cost for generators due to
avoided reinforcements.
Regulation for DRES Connections
Should Be Homogenized

An overview of DRES connection procedures reveals relevant differences from country to country. Variations include
connection request processes, maximum acceptable limit
definitions, incentives, and cost attribution. Homogeneous rules
could contribute to the development of widely applicable SG
solutions that could pass more easily from research to business as usual.
In Spain, Royal Decree (RD) 413/2014 establishes that
generators with a nominal power of 5 MW or higher must
be connected to a control center [transmission system operator (TSO) or DSO]. The DSO must have access to real-time
measurements for RESs equal to or higher than 1 MW, with
measurement costs borne by the generator. In Greece, all
MV power plants and around 70% of LV ones can provide
remote measurements, but there is not a general requirement
for the DSO to have real-time measurements. Only measurements from large wind farms are linked to the TSO.
In Italy, DSOs have the obligation to connect DG units
with the fit-and-forget approach; this implies that, in some
cases, generators can be connected only after network reinforcements. Active users pay a standard connection fee,
depending on the power and on the straight distance from the
closest line. Generally, generators up to 100 kW are connected
to the LV level and larger plants (usually up to 10 MW) to
the MV level. In Spain there are no standard connection
costs. Each case should be studied and proposed that the
may/june 2017

generator pay extension costs. For generators lower than
10  kW, there is no payment for access or the connection
study (RD 900/2015).
The Italian Electrotechnical Committee (CEI) has released
the CEI 0-16 and CEI 0-21 standards, which define the technical rules for the connection of active and passive consumers to the HV, MV, and LV electrical public networks. Some
HV rules were extended to wind and PV plants in distribution
networks to avoid disconnection in case of system perturbations (Annex A.70 of the Italian network code). These standards also specify that the reactive power capabilities to be
provided by each technology (such as static and synchronous)
and the disconnection of DRES plants greater than or equal to
100 kW for system security after a TSO request (reduction of
distributed generation scheme, known as RIGEDI).
In Spain, the obligation of maintaining connection during voltage dips only applies to PV and wind plants larger
than 2 MW. In Greece, the obligation applies only beyond
3 MW. Concerning active voltage control, in Spain, plants
larger than 5 MW are must follow the TSO commands, and
the DSO can only propose actions to the TSO. In Greece, neither the TSO nor the DSO engages in active voltage control.
DSO Services Should be Fairly Compensated
with an Adequate Remuneration

Investment recovery schemes should be adapted to promote
the use of SG solutions. An SG has the potential to provide
a more sustainable, efficient, and secure electricity supply to
customers. However, the purchase, operation, and maintenance of the new components are difficult to justify in current regulatory frameworks. The economic analysis shows
that, frequently, the SG solutions proposed to connect additional renewable generation are less expensive than the traditional reinforcement of the grid, but DSOs are not stimulated
to take advantage of these solutions. The costs of grid reinforcement costs recouped, but, in general, innovative solutions are not covered by existing regulatory frameworks. In
certain countries, and in particular for SG solutions, capital
expenditures are covered, but operational expenditures are
not, yet. Many SG solutions reduce capital expenditures but
increase operational expenditures.
Incentives for information and communication technology
(ICT) deployment are required, and operation and maintenance
costs should be considered in DSO service remuneration.
Telecommunication solutions for some SG implementations
could be very expensive in sparsely populated areas. Regulators should consider incentives to support the development and
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Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - May/June 2017

IEEE Power & Energy Magazine - May/June 2017 - Cover1
IEEE Power & Energy Magazine - May/June 2017 - Cover2
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