SIST EN 50549-2:2019/A1:2024

Requirements for generating plants to be connected in parallel with distribution networks - Part 2: Connection to a MV distribution network - Generating plants up to and including Type B

This document specifies the technical requirements for the protection functions and the operational capabilities for generating plants, intended to operate in parallel with LV distribution networks.
For practical reasons this document refers to the responsible party where requirements have to be defined by an actor other than the DSO e.g. TSO, member state, regulatory authorities according to the legal framework. Typically the DSO will inform the producer about these requirements.

Anforderungen für zum Parallelbetrieb mit einem Verteilnetz vorgesehene Erzeugungsanlagen - Teil 2: Anschluss an das Niederspannungsverteilnetz - Erzeugungsanlagen bis einschließlich Typ B

Exigences relatives aux centrales électriques destinées à être raccordées en parallèle à des réseaux de distribution - Partie 2: Raccordement à un réseau de distribution MT - Centrales électriques jusqu'au Type B inclus

Zahteve za vzporedno vezavo generatorskih postrojev z razdelilnim omrežjem - 2. del: Vezava s srednjenapetostnim razdelilnim omrežjem - Generatorski postroji do vključno tipa B - Dopolnilo A1

General Information

• Status: Published In Translation
• Public Enquiry End Date: 30-Jun-2023
• Publication Date: 11-Jan-2024
• ICS: 29.160.20 - Generators
• ICS: 29.240.01 - Power transmission and distribution networks in general
• Technical Committee: NTF - Electricity energy supply systems
• Current Stage: 6100 - Translation of adopted SIST standards (Adopted Project)
• Start Date: 14-Mar-2025
• Due Date: 13-Mar-2026
• Directive: 2016/631 - Commission Regulation (EU) 2016/631 of 14 April 2016 establishing a network code on requirements for grid connection of generators
• Directive: 2021-01-2083 - Pravilnik o tehničnih zahtevah za priključitev proizvodnih naprav električne energije na distribucijsko omrežje in o izvajanju 5. člena Uredbe Komisije (EU) št. 2016/631 o vzpostavitvi kodeksa omrežja za zahteve za priključitev proizvajalcev električne energije na omrežje
• Ref Project: EN 50549-2:2019/A1:2023 - Requirements for generating plants to be connected in parallel with distribution networks - Part 2: Connection to a MV distribution network - Generating plants up to and including Type B

Relations

• Amends: SIST EN 50549-2:2019 - Requirements for generating plants to be connected in parallel with distribution networks - Part 2: Connection to a MV distribution network - Generating plants up to and including Type B
• Effective Date: 01-Feb-2024
• Revised: SIST EN 50549-2:2019 - Requirements for generating plants to be connected in parallel with distribution networks - Part 2: Connection to a MV distribution network - Generating plants up to and including Type B
• Effective Date: 16-Mar-2021

Overview

SIST EN 50549-2:2019/A1:2024 is a European standard developed by CLC that addresses the technical requirements for generating plants connected in parallel with medium voltage (MV) distribution networks, focusing particularly on generating plants classified up to and including Type B. This standard provides regulatory guidance on the protection functions and operational capabilities these generating units must meet to ensure safe, reliable, and efficient interaction with MV distribution grids.

The standard serves as an amendment to EN 50549-2:2019, incorporating essential updates such as phase jump immunity, harmonized Rate of Change of Frequency (ROCOF) immunity, and refined fault ride-through (FRT) requirements. It is crucial for distribution system operators (DSOs), regulators, and manufacturers to align their installations and products with the updated requirements to maintain grid stability and foster integration of distributed energy resources.

Key Topics

1. Technical Requirements for Generating Plants

• Protection functions: Guidelines on interface protection settings and immunity to network disturbances.
• Operational capabilities: Requirements ensuring generating units can operate resiliently during voltage and frequency anomalies.
• Fault ride-through (FRT): Mandatory ability to remain connected during voltage dips (UVRT) and over-voltage conditions (OVRT).

2. Immunity to Disturbances

• ROCOF immunity: Generating plants must sustain stable operation during rapid frequency changes with a minimum immunity value of 2 Hz/s, adjustable by the responsible party.
• Phase jump immunity: Plants must tolerate abrupt voltage phase shifts up to a symmetrical 20°, resuming power output swiftly within defined timeframes.
• Voltage ride-through: Detailed criteria specify the voltage magnitude and duration thresholds generating units must withstand without disconnection.

3. Active Power Response

• Frequency deviations: Generating sites are required to implement fast active power response mechanisms to counteract overfrequency events, with reaction times tailored to specific technologies (e.g., photovoltaics, wind turbines, fuel cells).
• Energy storage behavior: Energy storage systems (EES) must follow configurable droop control strategies and have defined modes for power output regulation, ensuring flexibility within network demands.

4. Standardized Conformance Testing

• EN 50549-10 complements this standard by providing test methods for conformity assessment of generating units, ensuring compliance with technical specifications.

Applications

• Distributed Energy Resources (DER) Integration: SIST EN 50549-2:2019/A1:2024 guides the integration of renewable and conventional small to medium generating plants into MV distribution networks, crucial for decentralized generation.
• Grid Stability Enhancement: The requirements for fault ride-through and disturbance immunity help maintain continuous power supply and prevent widespread grid failures.
• Equipment Manufacturing and Certification: Manufacturers of generating units and interface protection equipment rely on this standard to develop compliant products aligned with European grid codes.
• Regulatory Compliance: DSOs and regulatory authorities use the document as a reference for defining connection conditions and operational limits for generation plants.

Related Standards

• EN 50549-1: Covers general requirements for generating plants connecting to the distribution network.
• EN 50549-10: Provides test procedures for assessing conformity of generating units and protection devices to the EN 50549 series.
• RfG (Requirements for Generators) Network Code: Sets EU-wide rules for generator connection, particularly relevant for voltage ride-through capabilities.
• IEC 60364 Series: Offers electrical installation guidelines relevant to distribution network safety and testing.
• EN 50465: Specific standards that may influence disconnection requirements for small CHP and fuel cell units under over-voltage conditions.

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Adherence to SIST EN 50549-2:2019/A1:2024 ensures generating plants operate reliably and harmoniously within MV distribution networks, supporting resilience and sustainability goals in modern energy systems. For DSOs, manufacturers, and grid operators, compliance is a critical step toward future-proof power infrastructure and compliant grid connection processes.

Standards Content (Sample)

SLOVENSKI STANDARD
01-februar-2024
Zahteve za vzporedno vezavo generatorskih postrojev z razdelilnim omrežjem - 2.
del: Vezava s srednjenapetostnim razdelilnim omrežjem - Generatorski postroji do
vključno tipa B - Dopolnilo A1
Requirements for generating plants to be connected in parallel with distribution networks
- Part 2: Connection to a MV distribution network - Generating plants up to and including
Type B
Anforderungen für zum Parallelbetrieb mit einem Verteilnetz vorgesehene
Erzeugungsanlagen - Teil 2: Anschluss an das Niederspannungsverteilnetz -
Erzeugungsanlagen bis einschließlich Typ B
Exigences relatives aux centrales électriques destinées à être raccordées en parallèle à
des réseaux de distribution - Partie 2: Raccordement à un réseau de distribution MT -
Centrales électriques jusqu'au Type B inclus
Ta slovenski standard je istoveten z: EN 50549-2:2019/A1:2023
ICS:
29.160.20 Generatorji Generators
29.240.01 Omrežja za prenos in Power transmission and
distribucijo električne energije distribution networks in
na splošno general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN 50549-2:2019/A1

NORME EUROPÉENNE
EUROPÄISCHE NORM October 2023
ICS 29.160.20
English Version
Requirements for generating plants to be connected in parallel
with distribution networks - Part 2: Connection to a MV
distribution network - Generating plants up to and including
Type B
Exigences relatives aux centrales électriques destinées à Anforderungen für zum Parallelbetrieb mit einem Verteilnetz
être raccordées en parallèle à des réseaux de distribution - vorgesehene Erzeugungsanlagen - Teil 2: Anschluss an
Partie 2: Raccordement à un réseau de distribution MT - das Niederspannungsverteilnetz - Erzeugungsanlagen bis
Centrales électriques jusqu'au Type B inclus einschließlich Typ B
This amendment A1 modifies the European Standard EN 50549-2:2019; it was approved by CENELEC on 2023-09-21. CENELEC
members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this amendment the
status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC
Management Centre or to any CENELEC member.
This amendment exists in three official versions (English, French, German). A version in any other language made by translation under the
responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the same status as
the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the
Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Türkiye and the United Kingdom.

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2023 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN 50549-2:2019/A1:2023 E

Contents Page
European foreword . 3
1 Modification to Introduction . 4
2 Modification to Clause 2, “Normative references” . 4
3 Modification to Clause 3, “Terms and definitions” . 4
4 Modification to Clause 4, “Requirements on generating plants” . 5
5 Modification to Annex C, “Parameter Table” . 9
6 Modification to Annex D, “List of national requirements applicable for generating plants”
......................................................................................................................................................10
7 Modification to Annex F, “Examples of protection strategies” .10
European foreword
This document EN 50549-2:2019/A1:2023 has been prepared by TC 8X “System aspects of electrical energy
supply”.
The following dates are fixed:
• latest date by which this document has to be (dop) 2024-09-21
implemented at national level by publication of
an identical national standard or by
endorsement
• latest date by which the national standards (dow) 2026-09-21
conflicting with this document have to be
withdrawn
This document amends EN 50549-2:2019.
This amendment includes the following significant technical changes:
— Introduction of a phase jump immunity requirement.
— Harmonizing the ROCOF immunity requirement for synchronous and non-synchronous generating
technology.
— Modifying FRT for type A from recommendation to requirement.
— Providing additional detail for EESS in case of overfrequency.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national committee. A complete
listing of these bodies can be found on the CENELEC website.
1 Modification to Introduction
Replace item 8. with the following:
“8. Implementation of UVRT and LFSM-U to avoid legal conflict with RfG
Under Voltage Ride Through (UVRT) requirements are defined in RfG for modules type B, type C and type D.
There is no mentioning of this topic for type A modules.
Nevertheless, UVRT is seen as an important requirement in some member states even for small generation
modules like type A.
NOTE At the time of writing, LVRT requirements for type A modules have been implemented in the following countries:
Austria, Czech Republic, Germany, Portugal (for PGM of 15 kW and higher), Switzerland.
From a legal point of view there are two contradicting opinions on whether it is allowed or forbidden to require
UVRT for type A modules.
— Opinion 1: It can be required because the topic is not dealt with for type A modules.
— Option 2: It cannot be required because the topic UVRT is dealt within the RfG. Not mentioning UVRT for
type A in RfG therefore means that it cannot be required for type A modules.
TC8X WG03 adopts the view of ACER as expressed in “ACER Monitoring of the Implementation of the Grid
Connection Network Codes” 11 November 2021 Item 3.3.4 #D where it states the German UVRT requirement
for Type A as compliant with NC RfG.
This same explanation can be applied to the requirements regarding Limited Frequency Sensitive Mode -
Underfrequency (LFSM-U). In RfG, this LFSM-U is solely defined for type C and type D modules. In EN 50549,
LFSM-U is defined as a recommendation (should) for generating modules of type A and type B. The sole
exception is electrical energy storage systems having a requirement (shall). These systems are currently not
within the scope of the RfG.”
2 Modification to Clause 2, “Normative references”
Add the following reference:
EN 50549-10, Requirements for generating plants to be connected in parallel with distribution networks -
Part 10: Tests for conformity assessment of generating units
Delete the reference EN 60255-127.
3 Modification to Clause 3, “Terms and definitions”
Add the following note to entry to 3.2.9:
“
Note 3 to entry: Electric vehicle charging stations intended to feed power back to the grid are considered an EESS while
a vehicle is connected.”
Add the following note to entry to 3.2.10:
“
Note 2 to entry: Electric vehicle charging stations intended to feed power back to the grid are considered an EES while a
vehicle is connected.”
Add the following term entries:
“
3.4.9
phase
instantaneous phase
ϑ
argument of the cosine function in the representation of a sinusoidal quantity
Note 1 to entry: The term “instantaneous phase” is only used when the independent variable is time.
ˆ
Note 2 to entry: For the quantity a(t) = Atcos ω +ϑ , the phase is ωt+ϑ .
( )
0 0
[SOURCE: IEV 103-07-04]
3.4.10
instantaneous frequency
first derivative of instantaneous phase
3.4.11
rate of change of frequency
ROCOF
first derivative of instantaneous frequency or second derivative of instantaneous phase
3.4.12
phase jump
abrupt change in the phase of the voltage of an AC electrical network
“
4 Modification to Clause 4, “Requirements on generating plants”
4.1 Modifcation to subclause 4.1, “General”
Add the following at the end of the subclause:
“EN 50549-10 provides technical guidance for tests on generating units and interface protection to evaluate
their electrical characteristics. EN 50549-10 shall be applied to evaluate the characteristics of generating units
and interface protection used in generating plants relating to the requirements of this Standard.
Electrical characteristics may alternatively be evaluated according to standards other than EN 50549-10, if the
following prerequisites are fulfilled:
— The alternative verification procedure covers all required technical aspects and characteristic quantities
stipulated in EN 50549-1 and EN 50549-2, respectively.
— The alternative verification procedure shall not be less stringent or technically less demanding than the
correspondent verification procedure in EN 50549-10.
— The alternative verification procedure leads to results of at least equivalent confidence level as
EN 50549-10.
— The equivalent or higher confidence level of the alternative verification procedure shall be confirmed by the
entity stating compliance based upon these tests
— The entity stating compliance based upon these tests shall have sufficient expertise in both EN 50549-10
and the applied standard.
NOTE This also applies for a partial application of another standard only for specific functions or operational
capabilities.”
4.2 Modification to subclause 4.5, “Immunity to disturbances”
4.2.1 Modification to subclause 4.5.1, “General”
Add the following at the end of the subclause:
“The described immunity requirements are independent of the interface protection settings. Disconnection
settings of the interface protection relay always overrule technical capabilities. So, whether the generating plant
will stay connected or not will also depend upon those settings.”
4.2.2 Modification to subclause 4.5.2, “Rate of change of frequency (ROCOF) immunity”
Replace the content of the subclause with the following:
“ROCOF immunity of a power generating plant means that the generating modules in this plant stay connected
with the distribution network and are able to operate when the frequency on the distribution network changes
with a specified ROCOF. The generating units and all elements in the generating plant that might cause their
disconnection or impact their behaviour shall have the same level of immunity.
The generating modules in a generating plant shall have ROCOF immunity to ROCOF equal or exceeding the
value specified by the responsible party. If no ROCOF immunity value is specified, at least 2 Hz/s shall apply.
The ROCOF immunity is defined with a sliding measurement window of 500 ms.
NOTE 1 For control action based on frequency measurement shorter measurement periods are expected to be
necessary.
NOTE 2 For small isolated distribution networks (typically on islands) higher ROCOF immunity values might be required.”
4.2.3 Modification to subclause 4.5.3, “Under-voltage ride through (UVRT)”
4.2.3.1 Modification to subclause 4.5.3.1, “General”
Replace the content of the subclause with the following:
“Generating modules shall comply with the requirements of 4.5.3.2 and 4.5.3.3.
Exempted from this requirement are small generating units below 50 kW of the following generation
technologies: CHP, fuel cell, rotating machinery, hydro.
NOTE 1 The power threshold of this exemption is expected to be reduced in future or the exception might be deleted
completely especially once the installed capacity becomes relevant for the grid stability.
The requirements apply to all kinds of faults (1ph, 2ph and 3ph).
NOTE 2 A more distinctive differentiation for 1ph, 2ph and 3ph faults is under consideration.
NOTE 3 The FRT curves in Figure 6, Figure 7 and Figure 8 describe the minimum requirements for continued connection
of the generating plant to the grid. They are not designed for parameterising the interface protection.”
4.2.4 Modification to subclause 4.5.4, “Over-voltage ride through (OVRT)”
Replace the content of the subclause with the following:
“Generating modules shall be capable of staying connected to the distribution network as long as the volt
...