DS DSF-CLC-FprTS 50549-2-2011.pdf

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FORSLAG / DRAFT DSF/CLC/FprTS 50549 2:2011 Forslagsnr.: M256968 Draft no.: Forslaget er: CLC/FprTS 50549 2:2011 IDT The draft is: (IDT = identisk med/identical to EQV = baseret på/equivalent to MOD = modificeret/modified) IDT Dette forslag til Dansk Standard er til offentlig høring fra: This draft Danish Standard is submitted for public enquiry from: 2011 07 15 til/to 2011 09 20 Forslag til dansk titel: Krav for tilslutning af generatorer over 16A per fase Del 2: Tilslutning til MV distributionssystemer Proposal for English title: Requirements for the connection of generators above 16 A per phase Part 2: Connection to the MV distribution system Der kan fremsendes tekniske og redaktionelle kommentarer til forslaget. Technical and editorial comments on the draft can be submitted. Kommentarer fremsættes ved at rekvirere en elektronisk kommentarskabelon hos projektlederen. Skabelonen udfyldes og returneres til projektlederen inden høringsperiodens udløb. Modtagne kommentarer vil blive behandlet af det teknisk ansvarlige udvalg. A template for comments must be used and can be obtained from the responsible project manager. The comments will be dealt with in the DS Committee responsible for the area. Kommentarer skal være DS i hænde senest: 2011 09 20 Comments shall be sent to DS no later than: Standardiseringsudvalg: DS/S 508 DS committee: Projektleder: Søren Nielsen Project manager: [email protected] Bemærk, at forslaget skal bearbejdes yderligere, og at det derfor ikke har gyldighed som Dansk Standard Note that the draft will be edited further and has no validation as a Danish Standard. COPYRIGHT Danish Standards. NOT FOR COMMERCIAL USE OR REPRODUCTION. DSF/CLC/FprTS 50549-2:2011

description

DS DSF-CLC-FprTS 50549-2-

Transcript of DS DSF-CLC-FprTS 50549-2-2011.pdf

Page 1: DS DSF-CLC-FprTS 50549-2-2011.pdf

FORSLAG / DRAFTDSF/CLC/FprTS 50549 2:2011

Forslagsnr.: M256968Draft no.:

Forslaget er: CLC/FprTS 50549 2:2011 IDTThe draft is:(IDT = identisk med/identical to EQV = baseret på/equivalent to MOD = modificeret/modified)

IDT

Dette forslag til Dansk Standard er til offentlig høring fra:This draft Danish Standard is submitted for public enquiry from:

2011 07 15 til/to 2011 09 20

Forslag til dansk titel:Krav for tilslutning af generatorer over 16A per fase Del 2: Tilslutning til MV distributionssystemer

Proposal for English title:Requirements for the connection of generators above 16 A per phase Part 2: Connection to the MVdistribution system

Der kan fremsendes tekniske og redaktionelle kommentarer til forslaget.Technical and editorial comments on the draft can be submitted.

Kommentarer fremsættes ved at rekvirere en elektronisk kommentarskabelon hos projektlederen. Skabelonen udfyldes og returnerestil projektlederen inden høringsperiodens udløb. Modtagne kommentarer vil blive behandlet af det teknisk ansvarlige udvalg.

A template for comments must be used and can be obtained from the responsible project manager. The comments will be dealt with in theDS Committee responsible for the area.

Kommentarer skal være DS i hænde senest: 2011 09 20Comments shall be sent to DS no later than:

Standardiseringsudvalg: DS/S 508DS committee:

Projektleder: Søren NielsenProject manager: [email protected]

Bemærk, at forslaget skal bearbejdes yderligere, og at det derfor ikke har gyldighed som Dansk StandardNote that the draft will be edited further and has no validation as a Danish Standard.

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FINAL DRAFT TECHNICAL SPECIFICATION CLC/FprTS 50549-2 SPÉCIFICATION TECHNIQUE

TECHNISCHE SPEZIFIKATION June 2011

CENELEC European Committee for Electrotechnical Standardization

Comité Européen de Normalisation Electrotechnique Europäisches Komitee für Elektrotechnische Normung

Management Centre: Avenue Marnix 17, B - 1000 Brussels

© 2011 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Project: 23224 Ref. No. CLC/FprTS 50549-2:2011 E

ICS 29.160.20

English version

Requirements for the connection of generators above 16 A per phase - Part 2: Connection to the MV distribution system

Prescriptions relatives au raccordement de générateurs de plus de 16A par phase - Partie 2: Connexion au réseau de distribution MT

This draft Technical Specification is submitted to CENELEC members for vote by correspondence Deadline for CENELEC: 2011-09-30. It has been drawn up by CLC/TC 8X. 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, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are aware and to provide supporting documentation. Warning : This document is not a Technical Specification. It is distributed for review and comments. It is subject to change without notice and shall not be referred to as a Technical Specification.

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Foreword

This draft Technical Specification was prepared by WG 03 - Requirements for connection of generators to distribution networks of the Technical Committee CENELEC TC 8X, System aspects for electrical energy supply. It is circulated for voting in accordance with the Internal Regulations, Part 2, Subclause 11.3.3.3. The following date is proposed: – latest date by which the existence of the CLC/TS

has to be announced at national level (doa)

dor + 6 months

__________

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Contents

1 Scope ................................................................................................................................................52 Normative references ......................................................................................................................53 Terms and definitions .....................................................................................................................64 Interconnection requirements........................................................................................................9

4.1 General ...................................................................................................................................94.2 Network integration ..............................................................................................................94.3 Connection scheme ........................................................................................................... 10

4.3.1 General................................................................................................................... 104.3.2 Choice of switchgear General ........................................................................ 11

4.4 Voltage and frequency tolerances ................................................................................... 114.4.1 General................................................................................................................... 114.4.2 Continuous operation .......................................................................................... 124.4.3 Low frequencies ................................................................................................... 124.4.4 High frequencies ................................................................................................... 12

4.5 Starting, synchronisation and reconnection .................................................................. 134.5.1 Plants using rotating machines .......................................................................... 134.5.2 Plants using static converters ............................................................................ 13

4.6 Response to normal voltage and frequency variations ................................................. 134.6.1 Power-frequency control ..................................................................................... 134.6.2 Voltage control ...................................................................................................... 13

4.7 Response to abnormal voltage and frequency variations ............................................. 144.7.1 Abnormal voltage variations ............................................................................... 144.7.2 Abnormal frequency variations ........................................................................... 15

4.8 Short circuit power requirements .................................................................................... 164.9 Power quality ...................................................................................................................... 164.10 Protection ........................................................................................................................... 16

4.10.1 General................................................................................................................... 164.10.2 Protection which trips the interface switch ....................................................... 164.10.3 Protection of the producer’s network ................................................................. 174.10.4 Generating unit protections................................................................................. 17

4.11 Coordination of protections .............................................................................................. 174.12 Exchange of information ................................................................................................... 18

5 Conformance test procedure ...................................................................................................... 195.1 General ................................................................................................................................ 19

5.1.1 Scope and object .................................................................................................. 195.1.2 Measurement system requirements ................................................................... 195.1.3 Requirements for simulated grid ........................................................................ 195.1.4 Test signals ........................................................................................................... 205.1.5 Step up signal ....................................................................................................... 205.1.6 Step down signal .................................................................................................. 205.1.7 Phase step signal ................................................................................................. 205.1.8 List of symbols ..................................................................................................... 215.1.9 Test reports ........................................................................................................... 21

5.2 Description of tests............................................................................................................ 215.2.1 Starting .................................................................................................................. 215.2.2 Synchronisation .................................................................................................... 22

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5.2.3 Reconnection ........................................................................................................ 235.2.4 Power-frequency control ..................................................................................... 235.2.5 Voltage control ...................................................................................................... 245.2.6 Abnormal voltage variations ............................................................................... 255.2.7 Abnormal frequency variations ........................................................................... 265.2.8 Short-circuit power requirement ......................................................................... 265.2.9 Protection .............................................................................................................. 275.2.10 Loss of mains protection test ............................................................................. 275.2.11 Directional power protection function test ........................................................ 285.2.12 Environmental testing for the interface protection system ............................. 295.2.13 EMC testing for the interface protection system .............................................. 30

Annex A (informative) Abbreviations ................................................................................................. 31Annex B (informative) National requirements ................................................................................... 32Bibliography ......................................................................................................................................... 34

Figures

Figure 1 Electricity generating plant connected to a Public Distribution Network (schematic view) .................................................................................................................................. 11

Figure 2 Fault-Ride-Through curve, voltage at the point of connection of the generating unit ..................................................................................................................................... 15Figure 3 Active power reduction for over frequency conditions ............................................... 16

Figure 4 Single phase equivalent circuit for loss of mains protection test .............................. 28

Tables

Table 1 Maximum allowable power reductions in case of low frequency on the grid ............. 12Table 2 Maximum allowable power reductions in case of high frequency on the grid ........... 12

Table 3 Behaviour of generating plants providing dynamic grid support during voltage events ...................................................................................................................................... 15

Table 4 Protections for generating plants connected to a Public Distribution Network ......... 17Table 5 Sequence of operation of the switches .......................................................................... 18

Table 6 Sequence of operation of the protective devices in case of an individual line connection............................................................................................................................................ 18

Table 7 Voltage dips to be tested .................................................................................................. 25

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1 Scope

The purpose of this Technical Specification is to provide technical guidance for the connection of generating plants which can be operated in parallel with a public distribution network.

This Technical Specification is intended to be used as a technical reference in connection agreements between DNOs and electricity producers.

The requirements of this Technical Specification only apply to electrical machinery and equipment, irrespective of the kind of primary energy source.

This Technical Specification applies to all three-phase generating units that meet all of the following conditions as an individual generating unit or as a cluster of generating units with a common point of connection:

• converting any primary energy source into AC electricity;

• connected to the MV network;

• intended to operate in parallel with a public distribution network under normal network operating conditions.

This Technical Specification defines interconnection requirements and a conformance test procedure.

Island operation of generating plants, both intentional and unintentional, where no part of the public distribution system is involved is out of the scope of this Technical Specification.

Safety of personnel is out of the scope of this Technical Specification.

This Technical Specification recognises the existence of National Standards and Network Codes: these must be complied with. Only in the absence of these National Standards and Codes should the requirements of this Technical Specification be applied.

2 Normative references

The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

EN 50160, Voltage characteristics of electricity supplied by public distribution networks

EN 61000-2-2, Electromagnetic compatibility (EMC) Part 2-2: Environment Compatibility levels for low-frequency conducted disturbances and signalling in public low-voltage power supply systems (IEC 61000-2-2:2002, equivalent)

EN 61000-3-2, Electromagnetic compatibility (EMC) Part 3-2: Limits Limits for harmonic current emissions (equipment input current <= 16 A per phase) (IEC 61000-3-2:2005, equivalent)

EN 61000-3-3, Electromagnetic compatibility (EMC) Part 3-3: Limits Limitation of voltage changes, voltage fluctuations and flicker in low-voltage supply systems, for equipment with rated current 16 A per phase and not subject to conditional connection (IEC 61000-3-3:2008, equivalent)

EN 61000-3-11, Electromagnetic compatibility (EMC) Part 3-11: Limits Limitation of voltage changes, voltage fluctuations and flicker in public low-voltage supply systems Equipment with rated current 75 A and subject to conditional connection (IEC 61000-3-11:2000, equivalent)

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EN 61000-3-12, Electromagnetic compatibility (EMC) Part 3-12: Limits Limits for harmonic currents produced by equipment connected to public low-voltage systems with input current > 16 A and 75 A per phase (IEC 61000-3-12:2004, equivalent)

EN 61400-25-2, Wind turbines Part 25-2: Communications for monitoring and control of wind power plants Information models (IEC 61400-25-2:2006, equivalent)

IEC 60050, International Electrotechnical Vocabulary

IEC 60068-2-1:2007, Environmental testing Part 2-1: Tests Test A: Cold

IEC 60068-2-2:2007, Environmental testing Part 2-2: Tests Test B: Dry heat

IEC 60068-2-14:2009, Environmental testing Part 2-14: Tests Test N: Change of temperature

IEC 60068-2-78:2001, Environmental testing Part 2-78: Tests Test Cab: Damp heat, steady state

3 Terms and definitions

For the purposes of this document, the terms and definitions given in IEC 60050 and the following definitions apply.

3.1 connection agreement written agreement between a producer and a DNO regarding the connection of a generating plant to a Public Distribution Network

3.2 disconnection separation of the active parts of the generator from the public distribution network by means of mechanical contacts providing basic insulation at least

3.3 Equipment Under Test (EUT) generating unit -or part of a generating unit, or piece of equipment associated to a generating unit- that is being subjected to the functional tests and protection tests described in this Technical Specification

NOTE Each individual test should be referred to a EUT. Different tests, referred to the same generating unit, may require different EUT’s.

3.4 general switch switch installed as close as possible to the point of connection, for protection and disconnection of the whole plant from the distribution network

3.5 generating plant set of one or more generating units, circuits, equipment and auxiliary services for the production of electricity

NOTE A generating plant may include electric loads.

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3.6 generating unit set composed of one or more primary energy sources and one generator, to which the primary energy sources supply their non-electric energy for conversion into electricity

3.7 generator electric equipment which converts non-electric energy (supplied by primary energy sources) into electricity

3.8 generator switch switch installed electrically close to the terminals of each generator of the generating plant, for protection and disconnection of that generator

3.9 interconnection system equipment and functions (included the generator switch) used to connect a generating unit to a public distribution network

3.10 islanding condition in which the generating plant is supplying loads not connected to a public distribution network

3.11 interface switch switch installed in the producer’s network, for separation of a part of the producer’s network from the public distribution network, in order to enable island operation of a part of the producer’s network

3.12 interface protection system protection system which, in case of a fault on the public distribution network, opens the interface switch of a generating unit or prevents its closure, whichever is appropriate

3.13 medium voltage (MV) system electric system with a voltage whose nominal r.m.s. value is 1 kV < Uc 36 kV

NOTE Because of existing network structures, in some Countries the boundary between MV and HV can be different.

3.14 network one or several electric systems which are outside the generating plant

3.15 network operation under normal conditions stationary operating conditions where electricity demand is fully met without the ratings of any component of the electricity network being exceeded

3.16 operation in parallel with the Public Distribution Network situation where the generating plant is connected to and operating in synchronism with a public distribution network

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3.17 power/frequency control system automatic control system of a generating unit which opposes network frequency oscillations by adjusting power output accordingly

3.18 point of connection (POC) point on a public power supply system where a generating plant is, or can be connected

3.19 primary energy source non- electric energy source supplying an electric generator

NOTE Examples of primary energy sources include natural gas, wind and solar energy. These sources can be utilised, e.g., by gas turbines, wind turbines and photovoltaic cells.

3.20 producer party planning to connect an electricity generating plant to a public distribution network

3.21 producer’s network electrical installations owned/operated by the producer for internal distribution of electricity

3.22 protection any function that automatically trips a switch when a given condition occurs

3.23 rotating generating plant generating plant that, through rotating machinery, converts the primary energy source into electric energy to be supplied to a network

3.24 Short Circuit Ratio (SCR) ratio of the following quantities, referring to a synchronous generator: - numerator: Open Circuit Field Current to obtain 1 p.u. Terminal Voltage, - denominator: Short Circuit Field Current to obtain 1 p.u. Terminal Current

3.25 simulated grid set of equipment, movable or immovable, for voltage and frequency testing, which simulates an electric grid that, where appropriate, can itself be employed instead of the simulated grid, provided its integrity and the safety of operation are guaranteed

3.26 static generating plant generating plant that, through static devices, converts the primary energy source into electric energy to be supplied to the network

3.27 temporary operation in parallel with the Public Distribution Network conditions in which the generating plant is connected to a public distribution network, during defined short periods, to maintain the continuity of the supply voltage and to facilitate testing

3.28 trip time time lag starting when the measured quantity (e.g. frequency, voltage, power) exceeds the trip threshold and ending when the circuit breaker opens

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3.29 voltage control system automatic control system of a generating unit which opposes network voltage variations by adjusting reactive power output accordingly

4 Interconnection requirements

4.1 General

This clause defines connection criteria of the generating plants to the public distribution network and provides guidance for the selection of connection schemes and for the co-ordination of protection.

Three-phase generating plants (whether equipped with rotating or static generators) may be operated in parallel with a public distribution network, subject to compliance with the requirements of this Technical Specification. When the generating plant is composed of clusters of single-phase generators, efforts should be made to ensure power and voltage balance between phases. In this case unbalance of power shall not exceed 4,6 kVA.

NOTE Communication links between the single-phase generators are necessary to ensure this feature.

The provisions of this Technical Specification are independent of the duration of generating unit operation in parallel. It rests with the DNO to relax, if deemed appropriate, interconnection requirements for an individual generator whose operation in parallel only lasts for a short time (temporary operation in parallel). The relaxed requirements shall be recorded in the Connection Agreement, along with the maximum allowable duration of the temporary operation in parallel. An appropriate device shall automatically disconnect the generator as soon as the maximum allowable duration has elapsed.

4.2 Network integration

All generating plants shall meet the following connection requirements:

• the total installed power shall be compatible with the operating criteria agreed with the DNO;

• the connection of the generating plant shall not cause the short circuit current to exceed the breaking and making capacity of any circuit breaker;

• the settings applied to the protection equipment shall be selected to ensure correct tripping of the generator under fault conditions and stability against network disturbances as agreed with the DNO;

• where the generating plant is connected to a public distribution network that is fitted with fast automatic switching devices (e.g. auto-reclose circuit breaker), the trip times of the generator switches shall be such that the risk of out of phase reclosure is negligible. However, arrangements shall be provided, if appropriate, to prevent damage to the generator in case of out of phase reclosure.

• the generating plant shall not cause the current carrying capacity of the lines and transformers to be exceeded in any n-1 configuration of the network.

A connection agreement shall be reached between the DNO and the Producer, prior to connection. The connection agreement shall include, but shall not be limited to, the following issues:

• maximum power to be installed in the generating plan;

• connection voltage at POC (to be agreed upon between the producer and the DNO, in compliance with national standards and regulations;

• contribution of the generating plant to short circuit current;

• if appropriate, power factor at POC;

• operation and settings of automatic voltage power factor controller and power controller where present;

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• single line diagram of installation, showing the point of connection, the installation boundary, the measuring point, the breakers, the protection devices, the inverter (if any) etc.;

• earthing arrangement of the generating plant (in compliance with national legislation, standards and regulations;

• reconnection requirement;

• setting applied to the interface protection.

4.3 Connection scheme

4.3.1 General

The plant shall be in compliance with national legislation, standards and regulations and agreed upon between the producer and the DNO. Arrangements may be subject to agreement between the Producer and the DNO and can be different depending on the system needs.

The plant shall assure the following:

a) start up, operation and stop under normal network operating conditions, i.e. in the absence of faults or malfunctions;

b) faults and malfunctions within the generating plant shall not impair the integrity of the public distribution network;

c) co-ordinated operation of the interface switch with the generator switch, the general switch and the public distribution network switch, for faults or malfunctions during operation in parallel with the public distribution network;

d) disconnection of the generating plant from the public distribution network by tripping the interface switch in the following cases: 1) intentional opening of the public distribution network switch, 2) faults on the public distribution network, 3) abnormal voltage or frequency (i.e. excursions outside of set limits).

In order to satisfy the above functions, co-ordinated but independent switches and protection equipment may be applied to each of the following sections of the generating plant, as shown in example Figure 1:

• generator;

• part of the producer’s network designed to run as an island (if required);

• the remaining part of the producer’s (i.e. all of the producer’s network less the island section;

• Public Distribution Network.

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Figure 1 Electricity generating plant connected to a Public Distribution Network (schematic view)

4.3.2 Choice of switchgear General

Switches shall be chosen based on the characteristics of the system in which they are intended to be installed; for this purpose, the short circuit current at the installation point shall be assessed, taking into account, inter alia, the contribution of the generating plant being connected. All switches shall comply with relevant standards.

Unless otherwise stated in the connection agreement, a means of isolating the generating plant shall be accessible to the DNO at all times.

4.4 Voltage and frequency tolerances

4.4.1 General

The provisions in this paragraph apply to the voltage control system and to the power-frequency control system of the generating unit.

The voltage and frequency requirements shall be subject to the National Connection Codes applicable. In the absence of these codes, the following shall apply.

A generating unit must be resilient to the maximum deviations of voltage and/or frequency at the point of connection (POC), while reducing the maximum power as little as possible.

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The requirements governing reactive power in case of voltage fluctuations are described in more detail in 4.6.2.

In the frequency range from 47,5 Hz to 50,2 Hz the generating unit must be able to stay connected until voltage protection trips. Exception can be made for direct coupled Stirling generators with a rated power below 30 kVA.

For parallel operation with the Public Distribution Network, automatic start-up and synchronisation is allowed when the voltage and the frequency are within the normal continuous operation limits specified by the DNO.

4.4.2 Continuous operation

The area of normal continuous operation in the full-load frequency range is the nominal operational voltage ± 10 %.

At voltages Un -5 % > U Un -10 % and Un +5 % < U Un +10 % the generating unit shall provide voltage support according to 4.6.2.

At voltages below Un - 10 % or above Un + 10 % the generating unit must stay connected with a minimum reduction of power until under or over voltage protection trips.

Where minimum reduction is required, the generating unit may produce what it is capable of.

4.4.3 Low frequencies

When the frequency is low (below 49,5 Hz) and if voltages at the POC are within the full-load voltage range, a generating unit must be able to supply power only reduced from the maximum power at frequencies at the generating unit connection point as shown in Table 1.

Table 1 Maximum allowable power reductions in case of low frequency on the grid

Frequency range f

Hz

Operating time t

Maximum power reduction

%

47,5 < f 48,0 > 3 min < 15 %

48,0 < f 49,0 > 30 min < 10 %

49,0 < f 49,5 > 5 h < 10 %

4.4.4 High frequencies

When the frequency is high (above 50,2 Hz) and if voltages at the generating unit connection point are within the full-load voltage range, a generating unit must supply power reduced from the maximum power as shown in Table 2. Power reduction should be adjustable.

Table 2 Maximum allowable power reductions in case of high frequency on the grid

Frequency range f

Hz

Operating time t

Power reduction %

50,2 < f 52,0 > 15 min 40 % per Hz (see 4.7.2)

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4.5 Starting, synchronisation and reconnection

4.5.1 Plants using rotating machines

The provisions in this paragraph apply to the interface protection system of the generating plant.

The start-up and re-synchronization of the generating plant shall be performed by means of the primary energy source. Power to run the control system and auxiliary equipment may be drawn from the public distribution system, subject to the terms of the connection agreement.

Connection to the public distribution network shall be performed by means of the interface switch or the generator switch, whichever is appropriate.

Connection shall only be allowed if voltage amplitude, frequency and phase angle on the generating plant side differ from the corresponding quantities on the network side less than a tolerance threshold. The thresholds shall be stated in the connection agreement.

Between any two start-ups there shall be a delay of no less than 10 s.

Reconnection after tripping of interface protection shall be in compliance with national regulation and in agreement with the DNO.

4.5.2 Plants using static converters

The start-up and re-synchronization of the static generating plant shall be performed electrically and actuated with step-by-step control from no-load to the load conditions.

4.6 Response to normal voltage and frequency variations

4.6.1 Power-frequency control

The provisions in this paragraph apply to the power-frequency control system of the generating unit.

Generators exceeding 1 MW shall be able to contribute to grid frequency control, both in case of over frequency and in case of under frequency; whether or not each individual unit should actually contribute to grid frequency control shall be stated in the connection agreement, along with the relevant quantities (droop, accuracy, etc.).

It shall be possible to control the frequency regulation via an external signal.

Frequency control devices shall meet at least the following functional requirements:

• frequency control accuracy better than 0,02 % under all operating conditions;

• droop setting to be selectable between 1 % and 6 %;

• insensitivity range to be ± 10 mHz or less;

• deadband setting to be selectable between 0 mHz and ± 200 mHz;

• capable of correct operation between 47 Hz and 52 Hz.

The droop to be set on each frequency device shall be provided by the DNO and shall be stated in the Connection Agreement.

4.6.2 Voltage control

The provisions in this paragraph apply to the voltage control system of the generating unit.

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The voltage control (through reactive power management) and the provision/absorption of reactive power are meant to ensure that slow voltage variations remain within acceptable limits during normal operation of the network.

If required, the DNO may require the generating plant to make a contribution to voltage control or to the provision/absorption of reactive power.

When assessing the impact of generators on voltage profiles over the network, the obligations of the DNO towards all the network users shall be taken into considerations. In most cases, the requirements which must be met correspond to the voltage range given in EN 50160.

Contribution to voltage control:

a) all generators should be able to operate at power factors down to 0,95 (lagging or leading) when operated at 20% or more of rated active power, in order to provide reactive power or participate to voltage control through reactive power management;

b) if actually required for a particular generator, the form of the contribution to voltage control during active power infeed shall be agreed with the DNO. It is limited to the following possibilities;

Generators shall be able to: 1) operate in power factor control mode:

i) a constant power factor set-point (local automatic control);

ii) a cosφ(P) characteristic (local automatic control); iii) a constant reactive power set-point (local automatic control); iv) a variable (online) reactive power set-point (remote control);

2) operate in voltage control mode: i) a Q(U) characteristic (local automatic control);

c) the necessary voltage transducer should be precision class 1%; d) the generating plant should be able to complete its closed loop control within 1 min.

4.7 Response to abnormal voltage and frequency variations

4.7.1 Abnormal voltage variations

The provisions in this paragraph apply to the voltage control system of the generating unit.

Generating units shall contribute to the stability of the public distribution network. In this paragraph dynamic behaviour (“Fault Ride-Through”, FRT) of generating units is described. Dynamic grid support shall contribute to voltage stability at the high voltage level if voltage dips occur. It shall be prevented that unintentional switch-off of numerous generating units in the medium voltage level destabilise the grid further. National standards permitting, generating units contributing to dynamic grid support shall technically be able to behave during grid faults in accordance with FRT-curve in Figure 3 and with Table 3.

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Figure 2 Fault-Ride-Through curve, voltage at the point of connection of the generating unit

Table 3 Behaviour of generating plants providing dynamic grid support during voltage events

Sector Behaviour of generating plant

A • Generating unit shall stay connected • Operation within this area must not cause instability or separation from

the public distribution

B • Generating unit shall be able to run through without disconnecting • Injection of short circuit current according to 4.8

C • No requirements; generating unit may disconnect

NOTE These requirements are independent of the interface protection settings. Whether the generation plant will stay connected or not will also depend upon those settings.

These requirements apply to all kinds of faults (1ph, 2ph and 3ph). In case of unsymmetrical faults it has to be ensured that currents injected by the generating plant into phases not under fault do not cause voltages at the POC to exceed 1,1*Vc.

4.7.2 Abnormal frequency variations

The provisions in this paragraph apply to the power-frequency control system of the generating unit.

Even if the generating unit does not contribute to power-frequency control as described in 4.6.1, it will need to reduce active power for grid frequencies equal or higher than f1 = 50,2 Hz as presented in Figure 3. When reaching 50,2 Hz actual active power injection is stated as PM. Active power has to be reduced ( P) with a slope of 40 % per Hz. Active power may only be increased again when the grid frequency is lower than f3 = 50,05 Hz. Disconnection of the generating unit at frequencies below f2 = 52,0 Hz is not allowed. The insensitivity range of the frequency measurement shall be ± 10 mHz or less.

502.50

20 gridM

fPP

−××=∆

where

PM: actual power;

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fgrid: grid frequency.

Figure 3 Active power reduction for over frequency conditions

4.8 Short circuit power requirements

The generating unit shall support the system voltage at the POC during voltage dips, with the aim of contributing to the stability of the collective electricity supply grid and to regulation of reactive power.

Synchronous generating units shall have a short circuit ratio of 0,45 or more (see 3.24).

All other generating units, if required by the DNO, shall support the voltage during Fault Ride-Through in area B (see Figure 2) to an extent limited by the inherent boundaries of the technology of the generating unit.

NOTE For PV inverters, the above boundary is the rated current.

4.9 Power quality

Each generating unit shall comply with applicable IEC standards dealing with power quality and electromagnetic compatibility for generators.

4.10 Protection

4.10.1 General

The protection equipment shall be suitably rated to ensure a correct operation even in the presence of harmonic voltages and harmonic currents in the network.

4.10.2 Protection which trips the interface switch

The provisions in this paragraph apply to the interface protection system of the generating unit.

This clause refers to all generating units connected to a public distribution network.

Over and under frequency protection is aimed at disconnecting the generating plant from the public distribution network under conditions when the network is unstable and normal frequency can no longer be maintained.

Over and under voltage protection is aimed at disconnecting the generating plant when the network voltage is outside of agreed limits.

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Loss of mains protection is aimed at preventing islanded operation on a part of the public distribution network. National legislation permitting, any kind of implementation can be chosen for loss of mains protection, including dedicated devices and transfer trip facilities.

The type of protection functions shall be in compliance with national legislation, standards and regulation and shall be agreed upon between the producer and the DNO based on the characteristics of the generating plant and of the distribution network. The method chosen shall be recorded in the connection agreement.

Interface protection is not required to clear faults in the public distribution network; it is required to protect the generating plant from faults on the network and to prevent the generating plant energising the network at times when the generation is expected to be disconnected. Islanded operation shall be cleared before the reclosing time of the DNO switch, in order to allow fault clearing and prevent damage to the generators. Settings and tripping times for the interface protection shall be chosen accordingly.

The protections indicated in Table 4 shall be installed as a minimum requirement.

Table 4 Protections for generating plants connected to a Public Distribution Network

Protection Under Frequency

Over Frequency

Under Voltage stage 1

Under Voltage stage 2

Over Voltage

Max zero sequence voltage a

Loss of mains protection b a As appropriate with reference to earthing arrangements (not applicable to systems with static

generators).

b If required by the DNO, and provided national legislations and regulations are abided by.

The above relays shall trip the interface switch.

4.10.3 Protection of the producer’s network

The general protection of the producer’s network shall trip the general switch.

Any protection or set of protection is admissible, provided the following conditions are detected: earth fault, short-circuit and overload.

4.10.4 Generating unit protections

The generating units shall be protected according to the instructions of the manufacturer. The generating unit protection shall not trip as long as voltage and frequency are within the operating range of the interface protection.

4.11 Coordination of protections

The following sequence of operation is meant to be a guide to the requirements of the protection co-ordination and inter-tripping requirements. The detailed protection system shall be designed to take into account safety, operational requirements and network configuration.

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The sequence of operation of the switches for the various conditions is described in Table 5.

Table 5 Sequence of operation of the switches

Event Public

Distribution Network switch

General switch Interface switch Generator switch

Fault or anomalous operation of the Public Distribution Network

YES

(MAIN)

NO YES

(MAIN)

YES

(BACK UP)

Fault or anomalous operation of the producer network

YES

(BACK UP)

YES

(MAIN)

YES

(MAIN)

YES

(BACK UP)

Fault on the generating plant NO YES

(BACK UP)

YES

(MAIN)

YES

(MAIN)

In the case of a connection to a Public Distribution Network by means of an individual line, if the general switch is also the interface device, Table 6 is replaced by Table 6.

Table 6 Sequence of operation of the protective devices in case of an individual line connection

Event Public Distribution

Network switch Interface switch Generator switch

Fault or anomalous operation of the Public Distribution Network

YES

(MAIN)

YES

(MAIN)

YES

(BACK UP)

Fault or anomalous operation of the producer network

YES

(MAIN)

YES

(MAIN)

YES

(BACK UP)

Fault on the generating plant YES

(BACK UP)

YES

(MAIN)

YES

(MAIN)

4.12 Exchange of information

The generating plant shall be prepared for receiving an external start-stop signal for stopping and releasing the feed-in operation. The signal can be delivered via a dedicated electrical input (e.g. a terminal block) or by commands sent via a communication link. In the case of a wind power plant the communication link has to comply with EN 61400-25-2.

As a minimum the generating unit shall be able to exchange status and operating states with a remote location.

Future requirements may include the following list of quantities that could be measured in relevant generating plants, and may be provided through agreement to the DNO:

• Active Power;

• Reactive Power;

• Apparent Power;

• Power Factor;

• Voltage;

• Current;

• Frequency;

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• Harmonics;

• THD (Total Harmonic Distortion);

• Energy;

• Modes and States of Operation;

• Actual Status Information including Connection Status Information. CLC/TC 8X NOTE This subclause needs to be developed, improved and updated in combination with the development of IEC 61850-7–420 taking into consideration of modern concepts like multi agents, smart metering, energy management, electric vehicles, demand side management, ancillary services and any other quantity which should be measured in every Generating Plant (DG) and then possibly provided to the DNO.

5 Conformance test procedure

5.1 General

The conformance tests shall be subject to National Codes and Standards. In the absence of these Standards, the following shall apply.

5.1.1 Scope and object

The tests described in this clause are aimed at verifying the functions for connection of the generating units to the public distribution network.

Generators rated less 1 MVA shall normally be type-tested. If, for a legitimate reason, they have not been type-tested, then they shall be individually tested.

Generators rated 1 MVA or more shall be individually tested.

Type-tests can be performed in the factory, in a laboratory equipped with testing facilities or in the field.

Individual tests shall be performed in the field.

NOTE If necessary, mobile facilities can be used for field testing.

Each generator (or a representative sample, where applicable) shall be tested for requirements of this Technical Specification that are applicable to that generator.

If a test has been successfully performed, conformance of generator to the relevant requirement (and to that requirement only) is assumed to be guaranteed.

As far as is reasonably practicable, tests shall be performed prior to connection.

5.1.2 Measurement system requirements

The uncertainty of each measurement of a generating unit function shall not exceed 0,5 times the accuracy declared by the manufacturer of the generating unit.

5.1.3 Requirements for simulated grid

During each test, the simulated grid shall meet the following minimum requirements:

• the simulated grid shall provide the requested voltage and frequency, with appropriate stability and accuracy;

• the individual voltage harmonics and the voltage THD shall meet the requirements of EN 50160 for the appropriate voltage class;

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• the simulated grid steady state voltage shall not vary more than ± 1 % of rated value;

• for voltage protection tests, the voltage definition of the simulated grid shall not exceed 0,5 x a, where “a” is the accuracy declared by the manufacturer for the EUT;

• for frequency protection tests, the frequency definition of the simulated grid shall not exceed 0,5 x a, where “a” is the accuracy declared by the manufacturer for the EUT;

• for three-phase simulated grids, the inverse sequence component of phase-to-ground voltage shall not exceed 2 % of the relevant direct sequence component;

• for voltage protection tests, the simulated grid shall be capable to step the voltage between (Vtr - 2 x a) and (Vtr + 2 x a) within one cycle or within 1 % of the trip time set on the EUT, whichever is longer; the step is “uphill” for over voltage tests and “downhill” for under voltage tests;

• for frequency protection tests, the simulated grid shall be capable of steppimg the frequency between (ftr - 2 x a) and (ftr + 2 x a) within one cycle or within 1 % of the trip time set on the EUT, whichever is longer; the step is “uphill” for over frequency tests and “downhill” for under frequency tests.

5.1.4 Test signals

This clause deals with the step functions to be employed in the different tests described above.

The step-up function (Equation (1)) applies to tests where a maximum threshold is involved (i.e. over voltage, over frequency).

The step-down function (Equation (2)) applies to tests where a minimum threshold is involved (i.e. under voltage, under frequency).

For every function, the step time (whether step-up or step-down) shall be less than one cycle or 1 % of delay time set on the EUT, whichever is longer.

5.1.5 Step up signal

For tests involving a maximum threshold (i.e. over voltage, over frequency) a step function like Equation (1) shall be used. Parameter p varies from a value just below to a value just above Ptr (where Ptr is the trip value for the protection function that is under test).

)(4)2()( itr ttuaaPtp −××+×−= (1)

5.1.6 Step down signal

For tests involving a minimum threshold (e.g. under voltage, under frequency), a step function like Equation (2) shall be used. Parameter p varies from a value just above to a value just below Ptr.

)(4)2()( itr ttuaaPtp −××−×+= (2) 5.1.7 Phase step signal

For tests involving phase inversion of a sinusoidal quantity, a step function like Equation (3) shall be used. Phase angle of parameter under test varies from 0° to 180°.

)(180)( tutp ×°= (3)

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5.1.8 List of symbols p(t) Value of parameter under test at time t. Depending on circumstances, p may be a

voltage, a current, a frequency, etc. t Time u(t - ti) Unit step function (u = 0 when t < ti ; u = 1 when t > ti) Prt Trip value for parameter under test. Depending on circumstances, Ptr may be a

maximum threshold or a minimum threshold. ti Time when stepping occurs a Accuracy declared by the manufacturer for the EUT. Accuracy “a” is an absolute

quantity, and is expressed in the same unit as p(t) (t) Phase angle of a sinusoidal quantity at time t

5.1.9 Test reports

The test results shall be described in a test report. The test report shall refer to the generating unit as a whole, equipped with all functional and protection devices that will be used during normal operation.

The test report shall provide at least the following information:

a) manufacturer of generating unit; b) type or serial number of generating unit; c) manufacturer of primary energy source; d) type or serial number of primary energy source; e) rated power of primary energy source; f) manufacturer of electric generator; g) type or serial number of the electric generator; h) rated apparent power of the electric generator; i) list of functional and protection devices requested by this Technical Specification for the

generating unit being tested; j) Trip value and trip time for each protection function; k) accuracy of trip value and trip time for each protection function; l) reference to the clause of this Technical Specification according to which the generating unit has

been tested; m) the results of each test, as requested by this Technical Specification.

5.2 Description of tests

5.2.1 Starting

5.2.1.1 General

The EUT for this test is the generating unit.

For starting of the generating unit, voltage and frequency should be within the threshold stated in the connection agreement with the DNO. These frequency and voltage thresholds have to be tested. After each test it has to be verified that the EUT will start, under nominal connection conditions.

For all cases, measurement results have to be included in the test report. The connection of the generating unit to public distribution network has to be documented, giving the measured values of voltage and frequency.

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5.2.1.2 Test for under frequency threshold flow

Frequency is varied from (flow – 0,5 Hz) up to (flow – 0,1 Hz) in steps of 0,1 Hz with time duration of 20 s per step.

Test if the generating unit will start, under nominal connection conditions.

5.2.1.3 Test for over frequency threshold fhigh

Frequency is varied from (fhigh + 0,15 Hz) down to (fhigh + 0,01 Hz) in steps of 0,01 Hz with a time duration of 20 s per step.

Test if the generating unit will start, under nominal connection conditions.

5.2.1.4 Test for Under voltage threshold Vlow

Voltage is varied from (Vlow - 5 % of Vn) up to (Vlow - 1 % of Vn) in steps of 1 % of Vn with a time duration of 20 s per step.

Test if the generating unit will start under nominal connection conditions.

5.2.2 Synchronisation

5.2.2.1 Test purpose

The EUT for this test is the generating unit.

This test is aimed at checking that the generator switch is allowed to close if the voltage difference, the frequency difference and the phase angle difference are all within the limits recorded in the Connection Agreement, and is not allowed to close otherwise.

5.2.2.2 Test procedure

Connect the EUT in accordance with the instructions of the manufacturer.

Connect instrumentation to measure voltage difference, frequency difference and phase shift between EUT and simulated grid, then proceed as follows:

a) In this first part of the procedure, voltage and frequency of the simulated grid are kept constant to rated values; the generator voltage is variable. The test is aimed at checking that the EUT operates correctly both from a low voltage that is raised up to within the allowable range and from a high voltage that is lowered down to within the allowable range. 1) Set voltage and frequency of the simulated grid to rated values. 2) Set the generator voltage to a value exceeding the simulated grid voltage, so that the voltage

difference equals the allowable value plus twice the accuracy declared by the manufacturer. 3) Adjust generator frequency to the simulated grid frequency so that the frequency difference

and the phase angle difference are within the ranges set in the Connection Agreement.

NOTE In order to prevent unintentional blocking of the generator switch, the frequency difference and phase angle difference should not be too close to their respective limits.

4) Issue a closing command to the generator switch. 5) Vary generator voltage until the voltage difference equals the allowable value (set in the

Connection Agreement) minus twice the accuracy declared by the manufacturer. 6) Issue a further closing command to the generator switch. 7) Repeat steps 1) to 6) for four more times (five times overall). 8) Repeat steps 1) to 7) starting with the generator voltage lower than the simulated grid voltage,

so that the voltage difference equals twice the accuracy declared by the Manufacturer.

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b) In this second part of the procedure, voltage and frequency of the simulated grid are kept constant

to rated values; the generator frequency is variable. The test is aimed at checking that the EUT operates correctly both from a lower frequency that is raised up to within the allowable range and from a higher frequency that is lowered down to within the allowable range. 1) Set voltage and frequency of the simulated grid to rated values. 2) Set the generator frequency to a value exceeding the simulated grid frequency, so that the

frequency difference equals twice the accuracy declared by the manufacturer. 3) Adjust generator voltage to the simulated grid voltage so that the voltage difference is within

the range set in the Connection Agreement.

NOTE In order to prevent unintentional blocking of the generator switch, the voltage difference should not be too close to its limit.

4) Issue a closing command to the generator switch. 5) Decrease generator frequency until frequency difference equals the allowable value (set in the

Connection Agreement) minus twice the accuracy declared by the manufacturer. 6) Issue a further closing command to the generator switch. 7) Repeat steps 1) to 6) four more times (five times overall). 8) Repeat steps 1) to 7) starting with the generator frequency lower than the simulated grid

frequency, so that the frequency difference equals twice the accuracy declared by the Manufacturer.

5.2.2.3 Test result With reference to Tests 1 and 2 above, the test is successful if:

• the closing command is always executed within the requested time for tests a-g only (i.e. where voltage and frequency are within limits), and

• the closing command is never executed for tests h (which include re-runs of tests 1-g with voltage or frequency outside of set limits).

5.2.3 Reconnection

The EUT for this test is the generating unit.

The generating unit should be connected to public distribution network under nominal connection conditions. Active power injection should be 0,9*Pn. The generating unit is switched off, as if disconnected for an interface protection operation. The generating unit should then automatically reconnect to the public distribution network, in accordance with the requirements of the Connection Agreement.

The time between disconnection and reconnection to public distribution network should be measured. Also, the active power injection after reconnection should be measured until the generating unit reaches rated power injection.

5.2.4 Power-frequency control

The EUT for this test is the generating unit.

In the absence of specific European Standards for Equipment defining design and tests, the following should apply.

The power-frequency control capability as required in 4.6.1 shall be tested as stated below.

The droop shall be set to the lowest value of the setting range.

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Starting from 60 % of rated active power, the frequency set point of the generator speed governor shall be stepped up. The step amplitude shall be 10 mHz. The steady-state active power variation shall be recorded.

Starting from 60 % of rated active power, the frequency set point of the generator speed governor shall be stepped down. The step amplitude shall be 10 mHz. The steady-state active power variation shall be recorded.

Starting from 90% of rated active power, the frequency set point of the generator speed governor shall be stepped up. The step amplitude shall be 10 mHz. The steady-state active power variation shall be recorded.

Starting from 90% of rated active power, the frequency set point of the generator speed governor shall be stepped down. The step amplitude shall be 10 mHz. The steady-state active power variation shall be recorded.

The tests shall be repeated after setting the droop at its medium setting value (centre of the setting range) and at its highest setting value.

The test shall be deemed successful if all of the above active power variations are > 0.

5.2.5 Voltage control

The EUT for this test is the generating unit.

The reactive power provision and the contribution to voltage control through reactive power management as required in 4.6.2 shall be tested as stated below.

The test shall be performed according to the way the reactive power management is implemented and for the following active power levels:

• 100 % of the nominal power;

• 75 % of the nominal power;

• 50 % of the nominal power;

• 25 % of the nominal power (may be omitted if lower than generator minimum power).

The magnitudes of the following parameters shall be measured during the test on a one-cycle RMS basis:

• voltage;

• current;

• active power;

• reactive power.

Operate in power factor control mode:

a) Constant power factor set-point (local control): The test shall demonstrate that the generator is able to operate at a defined power factor set-point within the range 0,95 lagging to 0,95 leading. The accuracy will be assessed by comparing the set point with the actual power factor. Tests will be performed between 0,95 lagging and 0,95 leading with a step of 0,01 and for the power levels previously mentioned. The measured power factor shall not deviate by more than ±0,01 from the set-point.

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b) Constant reactive power set-point (local control): The test shall demonstrate that the generator is able to operate at a defined reactive power set-point within ± 33 % of the nominal power (corresponding to a power factor of 0,95). The accuracy will be assessed by comparing the set point with the actual reactive power. Tests will be performed for 0 %, 14 %, 20 %, 25 %, 29 % and 33 % and for the power levels previously mentioned. The measured reactive power shall not deviate by more than ±5 % of the nominal power from the set-point.

c) cosφ(P) characteristic (local control):

For this test, a linear characteristic between active power and power factor must be considered (P = 0 kW - cosφ = 1; P = PN - cosφ = 0,95). Tests will be performed for the power levels previously mentioned. The measured power factor shall not deviate by more than ±0,01 from the set-point.

d) A variable (online) power factor or reactive power set-point (remote control): The test shall be performed as in a) or b) above. In addition, the response to a step from cosφ = 1 to cosφ = 0,95 shall be measured. The response time shall be smaller than 1 min.

Operate in voltage control mode:

e) Q(U) characteristic (local control): The test shall demonstrate that the generator is able to set the reactive power according to the measured voltage. For this test, a programmable voltage source is needed, and a linear characteristic shall be used (U = 0,90 p.u. – Q = 33 % PN (leading)/ U = 0,90 p.u. – Q = -33 % PN(lagging)). The accuracy will be assessed by comparing the desired value (from the characteristic) with the actual reactive power. Tests will be performed in voltage steps of 0,025 p.u. and for the power levels previously mentioned. The measured reactive power shall not deviate by more than ±5 % of the nominal power from the desired value.

f) Constant voltage set-point (local control): This test shall be performed as per Test e) above, but inserting a reactance between the source and the EUT. The size of the reactance shall be chosen so that a voltage drop of 10 % is achieved with a reactive power flow of 33 % PN and the generator voltage set-point shall be set to 1 p.u. The measured voltage at the generator terminals shall deviate by no more than 0,01 p.u. from the set point.

g) A variable (online) voltage set-point (remote control): The test shall be performed as per Test f) above. In addition, the response to a step from U = 1,0 p.u. to U = 1,1 p.u. shall be measured. The response time shall be smaller than 1 min.

5.2.6 Abnormal voltage variations

The EUT for this test is the generating unit.

In order to demonstrate that a generating unit can fulfil the requirements for abnormal voltage variations, as stated in 4.7.1, it is necessary to conduct tests or prove by simulation, using validated models. The half-cycle RMS values of the three phase voltages at the POC are taken as the reference. If the voltage is not measured at the POC, the voltage will need to be calculated considering actual grid impedances. The voltage dips in Table 7 shall be verified.

Table 7 Voltage dips to be tested

Test Nr. Remaining voltage V/Vn Fault time

1 20-30 % 500 ms 2 45-60 % 800 ms 3 70-80 % 1 200 ms

Each test shall be carried out for 3-phase and for 2-phase faults.

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Each test has to be carried out at two active powers, from 0,1*Pn to 0,3*Pn and 0,9*Pn. Measured active power should be a 10 s average value.

For each test, the half-cycle RMS values of the voltages and currents shall be measured. The active and reactive power shall be calculated and shall be documented for each test.

A generating unit must remain connected after the faults in the transmission grid listed below. Compensation equipment must also remain connected:

• 3-phase short circuit: short circuit lasting 100 ms;

• 2-phase short circuit: short circuit lasting 100 ms followed by a new;

• with/without earth fault: short circuit (300-500) ms later, also lasting 100 ms.

A generating unit must have sufficient capacity to meet the foregoing requirements in the event of the following two independent sequences:

• at least two 2-phase short circuits within 2 min;

• at least two 3-phase short circuits within 2 min.

A generating unit must have sufficient reserves (auxiliary power, hydraulic capacity, etc.) to withstand the following two independent sequences:

• at least six 2-phase short circuits at 5 min intervals;

• at least six 3-phase short circuits at 5 min intervals.

The short-circuit protection of a generating unit must not be triggered by the cur-rents that can occur during and after faults in the transmission grid. This requirement is considered met for the individual generating unit if the short circuit protection is not triggered by the currents occurring in the above mentioned tests.

5.2.7 Abnormal frequency variations

The objective of this test is to verify the behaviour of the generating unit when operating at an “over frequency” condition. This test shall confirm if the generating unit can fulfil the requirements for abnormal frequency variations, as stated in 4.7.2 for abnormal frequency variations. All measurement recordings should be made using a moving average of 0,2 s for all signals. Measurements of primary energy, active power output and frequency shall be recorded. The accuracy of frequency measurements should be at least 10 mHz.

Tests shall be conducted at six different frequency set points:

• rated frequency ± 0,01 Hz;

• rated frequency + 0,2 Hz to 0,3 Hz;

• rated frequency + 1,10 Hz to 2 Hz;

• rated frequency + 0,06 Hz to 0,08 Hz;

• rated frequency ± 0,01 Hz.

Each test shall be carried out with two different active power injections. For the first test the active power shall be higher than 80 % of the nominal power of the generating unit; for the second test the active power shall be between 40 % and 60 % of the nominal power of the generating unit.

5.2.8 Short-circuit power requirement

Short-circuit current for each generating unit shall be determined by measurement results of test for abnormal voltage variations.

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5.2.9 Protection

5.2.9.1 General

The EUT for this test is the interface protection system of the generating unit.

It shall be proved with tests at the generating unit that the generating unit is able to fulfil the protection requirements stated in 4.10.

Tests shall be conducted for under and over voltage conditions and for under and over frequency conditions.

In all cases the trip value and the trip time shall be measured. The following measurements shall be made.

5.2.9.2 Measurement of release values a) Under voltage protection Vth-low:

Voltage is varied from 100 % of Vn down to (Vth-low – 5 % of Vn) in steps of 1 % of Vn with a time duration of 20 s per step.

b) Over voltage protection Vth-high:

Voltage is varied from 100 % of Vn up to (Vth-high + 5 % of Vn) in steps of 1 % of Vn with a time duration of 20 s per step.

c) Under frequency protection fth-low:

Frequency is varied from 50,0 Hz down to (fth-low – 0,5 Hz) in steps of 0,1 Hz with a time duration of 20 s per step.

d) Over frequency protection fth-high:

Frequency is varied from 50,0 Hz up to (fth-high + 0,5 Hz) in steps of 0,1 Hz with a time duration of 20 s per step.

5.2.9.3 Measurement of trip times a) Under voltage protection:

Negative voltage step from Vn down to measured under voltage release value minus 5 % of Vn.

b) Over voltage protection:

Positive voltage step from Vn up to measured over voltage release value plus 5 % of Vn.

c) Under frequency protection:

Negative frequency step from 50,0 Hz down to measured under frequency trip value minus 1 Hz.

d) Over frequency protection:

Positive frequency step from 50,0 Hz up to measured over frequency trip value plus 1 Hz.

Trip values and trip times shall be documented in the test report. Also the response time of the interface switch shall be measured and documented.

5.2.10 Loss of mains protection test

5.2.10.1 Test purpose

The EUT for this test is the interface protection system of the generating unit.

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This test is aimed at checking that the loss of mains protection function trips the appropriate switch.

This test is applicable to all types of loss of mains protection function other than directional power protection.

5.2.10.2 Test procedure

Figure 4 Single phase equivalent circuit for loss of mains protection test

Figure 5 shows the test circuit to be connected between each phase of EUT and the neutral:

a) connect the EUT in accordance with the instructions of the manufacturer; b) set all parameters of the EUT to the respective values of normal operation; c) adjust the voltage and frequency of the simulated grid to the EUT’s rated voltage ± 2 % and to

EUT’s rated frequency ± 0,1 Hz; d) choose appropriate values for R, L and C so that the quality factor (Qf) equals 1 ± 0,05 and

resonance frequency is as close as possible to rated frequency;

NOTE If the EUT output power factor is not 1, the EUT reactive power output shall be measured and taken into account when assessing Qf.

e) close switches 52-1, 52-2 e 52-3, and adjust the EUT output power to its rated value; f) adjust R, L and C until the fundamental frequency current through 52-3 in each phase is 2 % of

the EUT rated current or less; g) trip 52-3 and record time duration between tripping of 52-3 and the tripping of the generator

switch; h) repeat the test, increasing the reactive power by 1 % each time. For each test, record the time

duration between tripping of 52-3 and the tripping of the generator switch; stop testing when no further increase of this time occurs;

i) repeat steps a) to h) for no less than two intermediate operating conditions (e.g. 20 % and 50 % of rated power).

5.2.10.3 Test result

The test is successful if, for each of the tests, the generator switch trips within the expected time.

5.2.11 Directional power protection function test

5.2.11.1 Test purpose

The EUT for this test is the interface protection system of the generating unit.

This test is aimed at checking that the active power directional protection function trips the switch as prescribed.

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5.2.11.2 Test procedure

This test procedure employs step function (3):

a) connect the EUT in accordance with the instructions of the manufacturer; b) set all parameters of the simulated grid to the respective values of normal operation for the EUT; c) set (or verify) all parameters of EUT to the respective values of normal operation; d) adjust the EUT current amplitude to trip value minus twice the accuracy declared by the

manufacturer; e) adjust the EUT current phase angle to 0° (current in phase with relevant voltage); f) step change the current phase angle from 0° to 180° according to Equation (3); the current shall

be kept to this amplitude an this phase angle during ti seconds, ti being at least twice the trip time; g) after time ti has elapsed, step the current amplitude according to Equation (1); h) record the time lag from step to the expected EUT response; i) repeat steps d) to h) four more times (five times overall); j) if the trip voltage is selectable, repeat steps d) to h) at the medium value and at the maximum

value of the setting range; k) for multi-phase generators, repeat steps d) o i) for each phase individually and for all phases at a

time.

5.2.11.3 Test result The test is successful if, for each of the tests, the appropriate switch trips within the maximum allowable time. 5.2.12 Environmental testing for the interface protection system

5.2.12.1 General The installer shall provide documentation proving that the interconnection system has been subjected to the following environmental tests and severities. 5.2.12.2 Non energized (non heat-dissipating) EUT

- Dry heat according to IEC 60068-2-2:2007, test Bd (+55°C for 16 h);

- cold according to IEC 60068-2-1:2007, test Ab (-10°C for 16 h);

- change of temperature according to IEC 60068-2-14:2009, test Nb (+55°C for 2h, then -10°C for

2 h). 5.2.12.3 Energized (heat-dissipating) EUT

- Dry heat according to IEC 60068-2-2:2007, test Bd (+55°C for 16 h);

- damp heat, steady state according to IEC 60068-2-78:2001, test Cab (+40°C, RH 93±3% for

24 h);

- cold according to IEC 60068-2-1:2007, test Ad (-10°C for 16 h);

- change of temperature according to IEC 60068-2-14:2009, test Nb (+55°C for 2h, then -10°C for 2 h).

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5.2.13 EMC testing for the interface protection system The installer shall provide documentation proving that the interconnection system has been subjected to EMC tests according to the following standards as appropriate:

EN 61000-2-2;

EN 61000-3-2;

EN 61000-3-3;

EN 61000-3-11;

EN 61000-3-12.

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Annex A (informative)

Abbreviations

DNO distribution network operator DSO distribution system operator (DSO=DNO) EMC electromagnetic compatibility EUT equipment under test FRT fault ride-through MV medium voltage POC point of connection RH relative humidity SCR short circuit ratio THD total harmonic distortion

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Annex B (informative)

National requirements

This informative annex provides a survey of codes, legislation and standards in force in a few Counties, dealing with connection of generating plants to a public distribution network. GB – United Kingdom In Great Britain (GB), the following National Codes, Standards and Legislation deal with requirements for the connection of Generating Plant to the public distribution network and therefore shall be complied with: Grid Code

As required by the transmission licence, National Grid implemented the Grid Code, which is designed to permit the development, maintenance and operation of an efficient, co-ordinated and economical system for the transmission of electricity, to facilitate competition in the generation and supply of electricity and to promote the security and efficiency of the power system as a whole. National Grid and users of its transmission system are required to comply with the Grid Code.

The Grid Code is required to cover all material technical aspects relating to connections to and the operation and use of the transmission system or, in as far as relevant to the operation and use of the transmission system, the operation of the electric lines and electrical plant connected to it or to a distribution system.

The Grid Code also specifies data which system users are obliged to provide to National Grid for use in the planning and operation of the transmission system, including demand forecasts, availability of generating sets and intended dates of overhaul of large generating sets.

Any changes to the Grid Code are subject to the approval of the Authority.

http://www.nationalgrid.com/uk/Electricity/Codes/gridcode/ Distribution Code

Licensed distribution businesses, or distribution network operators (DNOs), are obliged under Condition 21 of their licences to maintain a Distribution Code detailing the technical parameters and considerations relating to connection to, and use of their systems. All DNOs currently operate the same version of the code, and the code is maintained by the GB Distribution Code Review Panel. All modifications to the Code have to be approved by the UK regulator Ofgem http://www.energynetworks.info/the-distribution-code/

Engineering Recommendation G59/2 Recommendations for the Connection of Generating Plant to the Distribution Systems of Licensed Distribution Network Operators

The purpose of this Engineering Recommendation is to provide guidance on the connection of Generating Plant to the Distribution Systems of licensed Distribution Network Operators (DNOs). It is intended to address all aspects of the connection process from standards of functionality to site commissioning, such that Customers, Manufacturers and Generators are aware of the requirements that will be made by the local DNO before the Generating Plant will be accepted for connection to the Distribution System. http://2010.energynetworks.org/distributed-generation/

Electricity Safety, Quality and Continuity Regulations (ESQCR): 2002 The Electricity Safety, Quality and Continuity

These Statutory Regulations specify safety standards which are aimed at protecting the general public and consumers from danger. In addition, the Regulations specify power quality and

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Regulations 2002 (Amended 2006) – Statutory Instrument Number 2665 –HMSO ISBN 0-11-042920-6

supply continuity requirements to ensure an efficient and economic electricity supply service for consumers. Part VI of these regulation lay out specific requirements in relation to Generation.

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Bibliography

IEC/TR 61000-3-6, Electromagnetic compatibility (EMC) Part 3-6: Limits Assessment of emission limits for the connection of distorting installations to MV, HV and EHV power systems

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