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8/3/2019 NC on Generator Connection DSOpaper FINAL3 2011 030 1073 01 E
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D e c e m b e r 2 0 1 1
Draft Network Code
“Requirements
for
All
Generators”
‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐
A EURELECTRIC DSO Position
Published with Support of GEODE & CEDEC
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The Union of the Electricity Industry–EURELECTRIC is the sector association representing the common interests of
the electricity industry at pan‐European level, plus its affiliates and associates on several other continents.
In line with its mission, EURELECTRIC seeks to contribute to the competitiveness of the electricity industry, to
provide effective representation for the industry in public affairs, and to promote the role of electricity both in the
advancement of society and in helping provide solutions to the challenges of sustainable development.
EURELECTRIC’s formal opinions, policy positions and reports are formulated in Working Groups, composed of
experts from the electricity industry, supervised by five Committees. This “structure of expertise” ensures that
EURELECTRIC’s published documents are based on high‐quality input with up‐to‐date information.
For further information on EURELECTRIC activities, visit our website, which provides general information on the
association and on policy issues relevant to the electricity industry; latest news of our activities; EURELECTRIC
positions and statements; a publications catalogue listing EURELECTRIC reports; and information on our events and
conferences.
Dépôt légal: D/2011/12.105/56
EURELECTRIC pursues in all its activities the application of
the following sustainable development values:
Economic Development
Growth, added‐value, efficiency
Environmental Leadership
Commitment, innovation, pro‐activeness
Social Responsibility
Transparency, ethics, accountability
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Draft Network Code “Requirement for All
Generators”
‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐
TF Grid Connection Codes
Jacques MERLEY (FR) Chair
Alberto CERRETTI (IT); Bruno GOUVERNEUR (BE); Tony HEARNE (IE); Riccardo LAMA (IT); Johan
LUNDQVIST (SE); Graeme VINCENT (GB); Siegfried WANZEK (DE)
Contact:
Pavla
MANDATOVA,
Advisor,
Networks
Unit‐
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1
TABLE OF CONTENTS
Executive Summary ...............................................................................................................2 Introduction...........................................................................................................................3
1. What is a “cross‐border network issue”?..........................................................................4 2. Various types of generators, various roles in European power systems .........................6 3. Various types of generators, various ways to ensure compliance.................................10 4. An open and evolutionary process rather than a state of the art document.................11 5. In‐depth involvement of DSOs to further revision of the document..............................11
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2
Executive Summary
In November 2011, ENTSO‐E released a new version of its working draft Network Code on
Connection Requirements Applicable to All Generators. EURELECTRIC welcomes improvement in the
new draft related to the no longer mandatory applicability of network code requirements to existing
plants. Nevertheless, EURELECTRIC DSOs feel the need to address their prevailing concerns about
the
scope
and
the
structure
of
the
working
draft
before
the
code
enters
the
public
consultation
planned by the end of January 2012.
The aim of this report is to present an alternative view on the rationale behind the draft. The
operation of DSO networks entails specific complexities, especially as DSO networks move from a
wholly demand‐dominated model to one where generation and demand have to be balanced to
some extent. The proposals hereby presented build on DSOs experience with network operation,
connection of an increasing number of generators at HV, MV and LV grids and development of the
related connection rules at national level.
The paper seeks to provide an explanation of the term ‘cross‐border network issue’. EURELECTRIC
DSOs believe that in order to comply with the goals of the Third Energy Package, to deal efficiently
with issues affecting cross‐border trade, the EU network code for grid connection of generators
should strictly and exclusively focus on issues that are directly cross‐border ones. The concept of
‘cross‐border network issue’ should be understood as the ensemble of effects related to
characteristics of the electric system, whether dynamic or static, where a local event or accident
can trigger a cross‐border system risk.
An explanation is given as to how the size and the characteristics of various types of generators
affect their role in the European power system with respect to various system variables. System
parameters listed in the ACER framework guideline are a relevant part of the EU network code but
for technical reasons not all of them have to be applied at the EU level to all sizes of generators.
Cross‐
border
impact
of
small
generators
connected
to
distribution
networks
is
limited
to
frequency management. Hence, substantial reduction of requirements for small generators and to
certain extent also medium size plants is proposed. Other issues should be kept in the framework
of technical standards and grid connection rules at national level, with due respect to the principles
of subsidiarity and proportionality. In this way, possible benefits of harmonisation with respect to
cross‐border issues could be maximised and difficulties with different local grid designs avoided.
The report also underlines that compliance of the smaller facilities should be ensured by
guarantees offered by manufacturers or vendors through type testing based on standards (with
engagement of independent certificators), complemented in some cases with testing and checking
before connection. Preferably, the process for testing and checking is to be defined according to
existing standards
and
national
rules.
Last but not least, emphasis is put on the in‐depth association of DSOs, as operators of networks
to which most of the new generators will be connected in coming years, due to the fact that even
for cross‐border issues across‐the‐board distribution grid design solutions are not always
available. There are numerous technical requirements for connection to distribution networks, as
well as associated commercial, legal and regulatory implications. In addition, the significant number
of connected customers calls for approaches susceptible to being efficiently applied in potentially
millions of individual cases. DSO expertise is essential in this respect.
EURELECTRIC DSOs, as members of the ‘DSO Expert Group’ (consisting of EURELECTRIC, CEDEC &
GEODE), therefore ask for close cooperation with TSOs in the drafting of this and the upcoming
codes in
order
to
ensure
a successful
outcome
of
the
process
in
due
time.
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3
Introduction
As emerges from the Third Energy Package, network codes are meant to lay down European‐
wide binding rules for electricity wholesale markets, system operation and grid connection. As
requested by the Heads of State in the February 2011 European Council, the emphasis shall fall
on framework guidelines and network codes necessary to implement the target model of the
European electricity
market
by
2014.
ENTSO
‐E is
the
primarily
responsible
party
for
drafting
the
network codes, whilst ACER is assigned to provide framework.
ENTSO‐E recently released a new version of its working draft Network Code on Connection
Requirements Applicable to All Generators that is together with other foreseen ‘technical
network codes’ for grid connection and system operation considered essential to facilitate the
functioning of the internal electricity market. Since the previous version released in March 2011,
the document has been adjusted in accordance with the final ACER Framework Guidelines
issued by ACER on 20 July 2011. EURELECTRIC warmly welcomes the substantial change related
to the application of the network codes requirements to existing plants (‘retrofitting’ issue)
being no longer mandatory but conditional to a prior positive cost‐benefit analysis at national
level.
Nevertheless, EURELECTRIC DSOs as network operators would like to address their prevailing
concerns about the scope, the structure and the philosophy of the working draft before the
code enters the public consultation planned by the end of January 2012. Even though the share
of distributed generation in Europe is on the rise and that most of the new generators (both in
number and capacity) are due to be connected to distribution networks in the coming years, it
must be noticed that the overall structure of the requirements has been designed without prior
coordination with DSOs. Similarly, very few comments raised by DSO experts in the process
have been taken on board in the newly released version of the code.
Until
recently,
DSOs
have
distributed
power
on
a
top‐down
basis.
With
more
and
more
generation capacities connected to their grids, their role will increasingly move beyond their
traditional role of “building and connecting” towards “connecting and managing”1. In order to
manage the distribution system and to contribute to the stability of the transmission grid, DSOs
will play a different role, like supporting balancing of load and generation and in the smart grids
perspective, possibly influencing dispatching distributed generation or managing voltage
regulation, and if necessary, using ancillary services for generators connected to their grid.
Structure, protection and automation systems as well as operation of distribution networks
(especially at MV and LV level) are completely different from transmission networks. And unlike
transmission
networks,
which
are
relatively
similar
to
each
other,
distribution
networks
may
vary with respect to DSO and grid design. Hence, issues raised by distributed generation differ
from the ones related to generators connected to transmission. The number of these plants and
of customers/producers is also much higher, and the capabilities of the generating facility
operator are widely diverse, ranging from household tenants to industrial operators. For these
reasons, simply extending concepts used in transmission with large scale generation to
distribution networks is usually not the best solution.
The network code should thus cover only the necessary subset of requirements for distributed
generation. This paper aims at explaining the main points that from EURELECTRIC DSO perspective
should be considered by the responsible bodies in order to ensure the successful outcome of the
network code
development
process
in
due
time.
1 EURELECTRIC 10 Steps to Smart Grids, http://www.eurelectric.org/10StepsTosmartGrids/
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1. What is a “cross‐border network issue”?
The interpretation of the term ‘cross‐border network issue’ is central in understanding the
objectives of the European network codes. ‘Cross‐border network issues and market integration
issues’ for which the network codes should be developed are not precisely defined by the
Regulation (EC) 714/2009. That leaves room for various interpretations of the term.
ENTSO‐E Proposal:
Considering that any two components in the electric system can potentially interact with each
other, ENTSO‐E interpretation includes not only any technical event on the interconnected
network, whether in distribution or transmission, but also any usage of this network that could
have technical or commercial consequences somewhere. According to this logic, “all the
requirements [included in the draft] have a system‐wide impact”.2 In addition, the current draft
calls for EU level harmonisation of technical standards in order to achieve cost efficiencies and
to facilitate markets for equipment.
EURELECTRIC DSOs Position:
The concept of cross‐border issue/effect should be strictly understood as a characteristic of a
network component, or connected apparatus, that allows a common mode action or reaction
to a network disturbance to propagate across borders to a significant fraction of the total
system, adversely and seriously affecting that fraction. In other words, cross‐border issues are
the ensemble of effects related to characteristics of the electric system, whether dynamic or
static, where a local event or accident triggers a cross‐border system risk.
The following
examples
attempt
to
clarify
this
principle.
Cross‐border issue: Frequency management
The frequency of the electrical system is the same for all users connected (in Europe, frequency is
typically maintained at 50 Hz) and the system can only function within a certain frequency range.
When generation exceeds consumption, power system frequency will increase and insufficient
generation to meet demand will result in falling frequency. Large frequency deviations could cause
cross‐border disturbances as the total amount of generation within the synchronous area, including
both large generators and distributed generation, would be potentially affected. This could result in
severe damage to generating equipment, disturbance of supply, etc. European requirements for all
types
of
generators
(including
those connected
at
distribution
level)
are
thus
needed
in
order
to
ensure the security of the whole system and continuity of supply.
Nevertheless, DSOs should be allowed to adapt the frequency range in which the generator
operates in the case when only distribution networks are affected. Possibility to increase
sensitivity of so‐called Interface Protection Relay (IPR) in case of faults on a MV feeder to avoid
island operation of a part of the network is a typical example.
2 See ENTSO‐E Pilot Network Code for Requirements for Grid Connection Applicable to All Generators FAQ, Answer
to FAQ no. 6.
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Typically non cross‐border issue: Voltage management
Maintaining voltage stability is essential to keep the electric system in good order. Voltage
control is essential to keep the voltage inside the contractual range for customers. However, it is
a variable with a much smaller range of influence than frequency. Only very large generation
facilities directly connected to high voltage feeder can exert a notable effect across borders.
Voltage influence ‘fades’ across long distance feeders, and through different voltage network
levels.
In addition, there is no European‐wide voltage common mode. The criticality of a given facility
contribution to voltage stability is highly dependent on the local network conditions and local
balancing. And in most cases, it is subject to possible trade‐off with local network
reinforcements.
This implies that some requirements must be specified with a severity directly conditioned by
the local network situation and the significance (size and voltage connection) of the facility.
Therefore, it is wise to set voltage management requirements for large facilities connected to
high level voltage in the European network code. However, for smaller facilities it is sufficient to
request that requirements are set at national level while taking into account the diversity of
possible system situations in order to achieve maximum efficiency.
All in all, the EU network code for grid connection of generators should exclusively focus on
issues that are directly cross‐border ones and which could not be attained without regulation
at the EU level.
Other issues should be kept in the framework of technical standards and existing and well‐
functioning grid connection rules at national level, with due respect to the principles of
subsidiarity and proportionality. The political intention to be derived from the Third Package
legislation ‐to deal efficiently with issues affecting cross‐border trade‐, must be correctly
addressed in the network code.
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2. Various types of generators, various roles in European power systems
ENTSO‐E Proposal:
ENTSO‐E classifies generators according to size and, as far as certain requirements are
concerned, according to their technological characteristics (synchronous, asynchronous modular
etc.)
and
intrinsic
capabilities.
Many of the proposed requirements deal in detail with the performance of generators who are
DSO customers and that often have limited impact beyond given distribution network and, in
most cases, no cross‐border impact.
EURELECTRIC DSOs Position:
EURELECTRIC DSOs agree that the achievement of the 2020 targets requires simple and
pragmatic process for connection of renewable generators to the system and lowering barriers
of entry to the business. However, considering the large amount of renewable power that will
be
connected
to
the
network,
TSOs
and
DSOs
all
over
Europe
must
be
able
to
foresee
their
behaviour in relation to their criticality for the system.
The principle of classification used by ENTSO‐E is excellent and necessary to fit the requirements
to capabilities inherent to some technologies and to keep them at an appropriate level of detail
and organisation. However, it should not be used to unnecessarily extend the requirements
beyond issues that are directly cross‐border.
Generator categories should be defined according to generator size considering the possible
role and impact of each category on the system. Size of the generation facility represents an
important criterion when related to various parameters/variables.
Our proposed
classification
as
outlined
below
is
thus
close
to
the
one
proposed
by
ENTSO
‐E,
or
even simpler. Considering that there is no need to regulate facilities that are hardly noticeable
from the network, we set a minimum capacity of 1kW for type A facilities. The capacity
threshold between type A and type B facilities in Continental Europe and Baltic synchronous
areas was extended to 1 MW because no strong argument in favour of an important difference
between synchronous areas was identified in our analysis.
Moreover, we take into account the revised understanding of the ‘cross‐border issue’ concept
with respect to each category.
Type A
Generators connected to low and medium voltage level with a facility capacity between 1kW and 1 MW.
Characteristics:
These generators are always connected at distribution level (exceptionally at transmission).
There are already millions of generators of this type connected in Europe. In many cases
there are also consumers on the same premises. The operator of the facility has no electro‐
technical background and is not even familiar with the idea and implications of being an
operator. Its facility is operated on the ‘connect‐and‐forget’ basis.
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Cross‐border impact:
The cross border impact is only related to frequency management since this variable is by
nature not border‐bound. The requirements for these generators are based on the ‘add and
do not harm the system’ principle. Thus the only requirement pertinent at European level is
the capability of such facilities to support a wide frequency range in case of disturbance. All
other requirements
should
be
set
at
national
level.
Type B
Generators connected at medium voltage level with a facility capacity between 1 MW and 10 MW.
Characteristics:
They are mostly DSO customers. They are numerous (thousands to tens of thousands) and
the facility operator is aware of being an operator even though he is not necessarily an
electro‐technical specialist.
Cross‐border
impact:
Same as for type A.
For the moment, there are no important differences between requirements for types A and
B pertinent at European level.
Type C
Generators connected at medium to high voltage level with a facility capacity above 10 MW. Characteristics:
They
are
DSO
or
TSO
customers
depending
on
the
organization
of
the
national
electric
system. They are numerous (thousands) and the facility operator is aware of being an
operator and mostly holds electro‐technical expertise, but frequently relies on
manufacturers’ skills as regards the capabilities of its machines.
Cross‐border impact:
Their cross‐border impact is related to frequency management since this variable is by
nature not border‐bound. The requirements for these generators are based on the ‘do not
harm the system and offer limited support in case of disturbance’ principle. The
requirements pertinent at European level concern the capability of those facilities to
support
a
wide
frequency
range
and
to
offer
regulating
capacity
to
support
the
system frequency in case of disturbance.
Type D
Generators connected at high to very high voltage with potentially unlimited capacity. Characteristics:
They are TSO and sometimes DSO customers depending on the organization of the national
electric system. They are rather numerous (hundreds to thousands) and they represent
most of the generation capacity in the existing system. The facility operator holds electro‐
technical
expertise
and
often
exerts
a
strong
influence
on
the
initial
idea
of
the
facility
and
its capabilities. This category includes the offshore facilities regardless of their power.
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Cross‐border impact:
Some of the most important facilities can exert an influence on system stability directly
across borders not only for frequency management but possibly also for other variables. The
requirements for these generators follow the ‘do not harm the system, offer extended
support for the defence of system integrity in case of disturbance and provide capacity to
restore the
system
after
large
scale
incident’
principle.
An
extended
set
of
requirements
is
probably pertinent at European level.
EURELECTRIC DSOs believe that this classification is fully in line with the ACER Framework
Guidelines that explicitly ask for definition of requirements for significant grid users with respect
to parameters listed in section 2.1. These system parameters should be part of the EU network
code but only for types of generators for which they are generally relevant with respect to
cross‐border impact. Table 1 outlines cross‐border impact of various system parameters in
relation to generation types.
For instance,
while
the
category
A
&
B
generators
cross
‐border
impact
(and
thus
significance)
is
only related to frequency management, other parameters that have cross‐border impact in
relation to large generators are not relevant at the EU level for types A & B and thus should not
be part of the network code. On the other hand, large generators (type D) can have an impact
on system stability also for other variables, such as voltage stability or inertia.
Table 1: Cross‐border impact of various system parameters in relation to generation types
Parameters listed in
the FG
Type A
LV/MV
(1kW –
1MW)
Type B
MV
(1MW‐10MW)
Type C
HV
>10MW
Type D
EHV
unlimited
Frequency
management
Yes
Limited
response &
automatic
disconnection
Yes
Limited
response &
automatic
disconnection
Yes
Extended
response &
automatic
disconnection
Yes
Extended response
with load
frequency control
Voltage & reactive
power management
No Cross‐
border Impact
No Cross‐
border
Impact
No Cross‐
border
Impact
Yes
Load ‐ frequency control No Cross‐
border
Impact
No Cross‐
border
impact
No Cross‐
border
impact
Yes
Short ‐circuit current No Cross‐
border impact
No Cross‐
border
impact
No Cross‐
border
impact
No Cross‐border
impact
Requirements for
protection devices &
settings
No Cross‐
border impact
No Cross‐
border
impact
No Cross‐
border
impact
No Cross‐border
impact
Fault ‐ride‐through
capability
No Cross‐
border Impact
No Cross‐
border
Impact
No Cross‐
border
Impact
Yes
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Since they are important at the Relevant Network Operator level, other requirements for types
A, B & C such as voltage level variations, voltage wave shape (harmonics, flickers, short duration
interruption etc.) grounding, signal quality and fault‐ride‐through should rely on regulations that
are proven and efficient, mostly at national level and on the use of standards.
As the share of variable RES in distribution grids increases, DSOs will need more tools to manage
their
grids
from
distributed
generators.
However,
with
respect
to
type
A
&
B,
frequency
response represents the essential requirements needed at European level. Requirements for
other functions, and if necessary ancillary services, should be set with involvement of DSOs in
the national grid codes and regulations.
To sum up, connection rules for distribution grids do not need to be lifted up to the European
level, except when there is a direct cross‐border impact. Reviewing (rewriting, consultation,
publication) of existing (or, when necessary, under development) national or local regulations
that already accurately address the topics would have minimal positive impact on the internal
market and on quality of supply for customers, both users and producers. Furthermore, it would
create legal uncertainty and risks resulting from the necessity to align detailed European wide
rules
with
national
rules
which
must
necessarily
provide
all
details
for
safe
operation
of
the
system in day to day operation. As a result, the global quality of the system would be reduced
(higher costs, lower performances).
Therefore, EURELECTRIC DSOs propose:
• to significantly reduce the scope of requirements for smaller facilities (A&B) and
substantially for medium size (C);
• to limit European level requirements concerning capabilities to offer ancillary services
to equipments connected to high voltage level (D) especially for ancillary services not
related to
frequency.
With
no
prejudice
for
requirements
at
national
level.
In addition, requirements must be expressed functionally at connection point with the
relevant Network Operator and apply to generating facilities rather than to generating units.
The operator of the generation facility should be responsible for transposing the constraints
expressed at connection point to generation units.
Expressing requirements at unit level should be accepted only if really necessary, for instance in
the case when specific capabilities at the unit level are also needed in addition to those at the
connection point in order to ensure that the facility as a whole meets a given requirement, and
not as a tool to refine and increase the requirements.
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3. Various types of generators, various ways to ensure compliance
Methods to test and monitor compliance of generation facilities also vary in relation to
generation type.
State of
the
Art:
For types A & B connected mostly to distribution grids, the primary responsibility for compliance
with requirements is on the generator side in most countries. Documentation including
verification of compliance is submitted by the generator to the Relevant Network Operator as a
part of the grid connection process. DSOs then can monitor compliance and participate in the
testing although they do not bear legal responsibility for accuracy of the compliance.
Testing by network operator and simulation is used mostly only for larger units connected to the
transmission grid and is inapplicable on distribution networks due to the number of generators.
ENTSO‐E Proposal:
The working draft lays down provisions for compliance testing and simulations of all types of
generators and the obligation for the relevant network operator to regularly assess the
compliance of a generating unit with the requirements under the network code throughout the
lifetime of the power generating facility.
EURELECTRIC DSOs Position:
Due to enormous number of connections at MV and LV level in many countries, it is impossible
for DSOs
to
perform
any
compliance
tests
with
the
exception
of
commissioning
ones.
In
order
to avoid costly and lengthy procedures in the case of smaller generation facilities, the current
best practices should be reflected. Generator capabilities should be assessed through type
tests, performed according to well defined testing procedures, in laboratories accredited by
EA (European Co‐operation for Accreditation) (EN 17025). Type tests shall be included in
product standards compliant with the requirements of the network code.
Specifically, we propose the following procedures with respect to different categories.
Type A
The compliance should be ensured by guarantees (e.g. certificates of compliance) given by
manufacturers or vendors through type testing based on standards. Type tests must be
performed in accredited laboratories, with reference to existing product standards or to
connection standards tests. For cases of need, DSOs should be given the option (not an
obligation) to monitor the compliance after connection.
Type B
The compliance should be ensured by guarantees offered by manufacturers through type
testing based on standards, like category A, possibly completed with testing and checking
before connection. The process for testing and checking is to be preferentially defined according
to existing standards and national grid codes and must be limited to main generation plant performances.
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Type C
Verification of compliance shall rest on guarantees offered by manufacturers through type
testing and/or standards and national grid codes, usually with some testing before connection
and/or simulation. The process for testing and checking is to be preferentially defined according
to existing standards. If this is not possible, it should be defined at national level.
Type D
Verification of compliance shall rest on guarantees offered by manufacturers through type
testing and/or standards, plus testing and simulation before connection possibly with periodical
checks. The process for testing and checking is to be preferentially defined according to existing
standards and national grid codes.
The compliance & simulation chapters of the draft code should be adjusted to take into account
the necessity to rely on standards and/or qualification procedures.
4. An open and evolutionary process rather than a state of the art document
The current working draft describes very precisely the variables on which the requirements are
based or the value span for those variables and the way compliance testing and simulation is to
be carried out as outlined above.
EURELECTRIC DSOs position:
The proposed
document
might
be
outdated
before
it
is
enforced
since
it
addresses
a very
broad
area of performances, with a restricted knowledge of the constraints and possibilities of
distribution networks. Considering the rapidly evolving organisation of the European electric
system, the network codes must be formulated in a flexible way that sets principles for
functionalities, but is open to future developments and designed for smooth implementation at
national level.
EURELECTRIC DSOs thus recommend that
• the present document is limited to essential issues. Other issues are already very well
reflected in existing national regulation (or in regulation to be developed before the
network code
comes
into
force);
• the maintenance and amendment process should be clarified and at best explicitly
included in the code;
• any maintenance should fully respect solutions that had already been implemented as
long as they are in line with the needs.
5. In‐depth involvement of DSOs to further revision of the document
As outlined in section 1, frequency management is undoubtedly a cross‐border issue. Extending
the frequency range in which the generation facilities connected to distribution grids can
operate is
necessary
for
maintaining
frequency
stability.
However,
the
following
example
of
safe
operation rules demonstrates that no easy across the board standardised solutions for actual
settings of the small generation facilities that could be applied in all countries are in place yet.
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Therefore, DSO expertise should be fully included in the ongoing development and drafting of
the network code.
EXAMPLE: Safe Operation Rules
Conflicts may
arise
from
incompatibility
of
work
safety
rules
and
adoption
of
functionalities
for
system security reasons. Disconnecting all power sources in case of an incident (or before
planned maintenance) is one of the first golden rules in prevention of electrical risk for persons
in network operations. This function is most of the time performed by protection devices
programmed to trip if some variables, like frequency, are out of set boundaries. With respect to
the high safety risks, obligations binding networks operators with very strong individual
responsibilities are laid down in various documents (i.e. national grid codes, labour legislation).
But from a system security point of view, as endorsed by the proposal, a simple and efficient
option is to ask for machines and protections to remain connected through a wider band of
frequency in order to prevent relatively small incidents from spreading into large scale ones.
While the
safety
rule
is
to
trip
in
case
of
any
incident,
the
decisive
factor
for
security
of
supply
is
to remain connected. However, proposed moderation of protection systems by weakening
frequency and voltage based protection settings could lead to an unacceptable increase of
electrical risk in distribution networks in some countries, depending on the adopted protection
strategy and type of generation. If implemented without due care, the requirements could
under certain circumstances (e.g. islanded operation) cause damage to generators and
consumer appliances.
Requirements with implications for protection settings at the grid connection point for the
generators connected to LV and MV networks may in some countries raise technical issues with
important
technical,
legal
or
financial
consequences
for
DSOs.
Abiding
the
wider
frequency
range requirements without any precaution could result in strong adverse effects on the quality
and operational safety to which DSOs are legally and financially committed in their day to day
operation.
EURELECTRIC DSOs position:
Although frequency requirements are needed to address cross‐border issues, potentially robust
adverse effects on functions, such as protections using frequency variation in their activation
routines, need to be taken into account. A suitable solution has to be found in order to enable
DSOs to
fulfil
their
requirements
to
ensure
the
quality
and
safety
of
networks
operation.
Therefore, it is essential that DSOs are fully included in the future development and drafting of
the network code so that the final draft is compatible with existing and future DSO practices for
both demand and generation.
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