generating plants connected to the vde-ar-n_4105

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VDE-AR-N 4105:2011-08

Power generation systems connectedto the low-voltage distribution network

Technical minimum requirements for the

connection to and parallel operation with

low-voltage distribution networksEnglish translation of the

VDE application rule VDE-AR-N 4105

Note: In case of doubt the

German version will be valid.


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English translation

VDE-AR-N 4105:2011-08Power generation systems connected to the low-voltage distribution

network — Technical minimum requirements for the connection to andparallel operation with low-voltage distribution networks

Contents

Page

Foreword.............................................................................................................................................................6

Introduction.........................................................................................................................................................6

1 Scope .....................................................................................................................................................6

2 Normative references.............................................................................................................................7

3

Terms, definitions and abbreviations .....................................................................................................83.1 Terms and definitions.............................................................................................................................8

3.2 Abbreviations........................................................................................................................................14

4 General framework conditions .............................................................................................................15

4.1 Provisions and regulations ...................................................................................................................15

4.2 Application procedure and connection relevant documents ................................................................15

4.3 Initial start-up of the power generation system....................................................................................15

5 Network connection..............................................................................................................................16

5.1 Principles for determination of the network connection point ..............................................................16

5.2 Rating of the network equipment .........................................................................................................17

5.3 Permissible voltage change .................................................................................................................17

5.4 System reactions..................................................................................................................................18

5.4.1 General..............................................................................................................................................18

5.4.2 Rapid voltage changes......................................................................................................................18

5.4.3 Flicker................................................................................................................................................18

5.4.4 Harmonics and inter-harmonics ........................................................................................................19

5.4.5 Voltage unbalance ............................................................................................................................20

5.46

Commutation notches .......................................................................................................................20

5.4.7 Audio-frequency centralised ripple-control........................................................................................20

5.4.8 Carrier frequent usage of the customer network...............................................................................21

5.4.9 Precautionary measures against voltage drops and voltage interruptions.......................................21

5.5 Connection criteria ...............................................................................................................................21

5.6 Three-phase network ...........................................................................................................................22

5.6.1 General..............................................................................................................................................22

5.6.2 Three-phase synchronous generators ..............................................................................................22

5.6.3 Three-phase inverter systems...........................................................................................................23

5.7 Behaviour of the power generation system at the network..................................................................23


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Page

5.7.1

General............................................................................................................................................. 23

5.7.2 Maximum permissible short-circuit current....................................................................................... 24

5.7.3 Active power output.......................................................................................................................... 24

5.7.3.1 Basics.......................................................................................................................................... 24

5.7.3.2

Generation management/network security management ........................................................... 24

5.7.3.3 Active power feed-in at overfrequency........................................................................................ 25

5.7.3.4 Active power feed-in at underfrequency...................................................................................... 26

5.7.4 Principles for network support .......................................................................................................... 26

5.7.5

Reactive power................................................................................................................................. 26

6 Construction of the power generation system/network and system protection (NS protection) ......... 29

6.1 General requirements.......................................................................................................................... 29

6.2 Central NS protection .......................................................................................................................... 29

6.3 Integrated NS protection...................................................................................................................... 30

6.4 Interface switch.................................................................................................................................... 30

6.4.1 General............................................................................................................................................. 30

6.4.2 Central interface switch .................................................................................................................... 30

6.4.3 Integrated interface switch ............................................................................................................... 31

6.5 Protective devices for the interface switch.......................................................................................... 31

6.5.1 General............................................................................................................................................. 31

6.5.2 Protective functions.......................................................................................................................... 32

6.5.3 Islanding detection ........................................................................................................................... 33

7

Metering for billing purposes ............................................................................................................... 34

8 Operation of the system ...................................................................................................................... 35

8.1 General................................................................................................................................................ 35

8.2 Particular characteristics of the management of the network operator’s network............................... 36

8.3 Connection conditions and synchronisation........................................................................................ 37

8.3.1 General............................................................................................................................................. 37

8.3.2 Connection of synchronous generators ........................................................................................... 38

8.3.3 Connection of asynchronous generators ......................................................................................... 38

8.3.4 Connection of power generation units with inverters ....................................................................... 38

8.4 Reactive power compensation ............................................................................................................ 38

9 Verification of the electrical properties ................................................................................................ 38

9.1 General................................................................................................................................................ 38

9.2 Verification of the feed-in power.......................................................................................................... 39

9.2.1 Verification of the feed-in active power ............................................................................................ 39

9.2.2 Verification of the reactive power values.......................................................................................... 39

9.2.3 Verification of the reactive power transition function........................................................................ 39

9.3 Verification of the network reactions ................................................................................................... 39

9.4

Verification of the features of the network and system protection ...................................................... 39

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Page

Annex A (informative) Explanations ................................................................................................................40

A.1 “Power generation system” (3.1.8) and “power generation unit” (3.1.9)..............................................40

A.2 Permissible voltage change (5.3).........................................................................................................40

A.3 System reactions (5.4) .........................................................................................................................41

A.3.1

Rapid voltage changes.........................................................................................................................41

A.3.2 Flicker...................................................................................................................................................42

A.3.3 Harmonics and inter-harmonics ...........................................................................................................42

A.3.3.1 General..............................................................................................................................................42

A.3.3.2

Line-commutated inverters (six- or 12-pulse) ...................................................................................43

A.3.3.3 Pulse-modulated inverters ................................................................................................................43

A.4 Connection criteria (5.5).......................................................................................................................43

A.5 Reactive power (5.7.5).........................................................................................................................44

A.6 General requirements, single-fault tolerance (6.1)...............................................................................46

A.7 Interface switch (6.4)............................................................................................................................47

A.8 Protective devices for the interface switch (6.5) ..................................................................................47

A.8.1 General.................................................................................................................................................47

A.8.2 Protective functions..............................................................................................................................47

Annex B (informative) Connection examples..................................................................................................48

B.1 Maximum apparent connection power S Amax ≤ 4,6 kVA ......................................................................48

B.2

Maximum apparent connection power S Amax ≤ 13,8 kVA ....................................................................49

B.3 Power generation system with communicative coupling of the single-phase inverters and

with integrated NS protection...............................................................................................................50

B.4

Maximum apparent connection power of S Amax > 30 kVA ...................................................................51

B.5 New power generation unit connected in parallel to an existing system S Amax > 30 kVA ...................52

B.6 Connection with meter column.............................................................................................................53

B.7 Connection for excess feed-in (self consumption in accordance with EEG, § 33 EEG andKWK-G, § 4 (3))....................................................................................................................................54

B.8 Connection for excess feed-in of > 30 kVA ..........................................................................................55

Annex C (informative) Examples of meter panel configurations .....................................................................56

C.1

Meter panel for connection of a power generation system with a maximum apparentconnection power S Amax ≤ 30 kVA (full feed-in)...................................................................................56

C.2

Meter panel for the connection of a power generation system with a maximum apparentconnection power S Amax > 30 kVA and with central NS protection......................................................57

C.3 Meter panel for the connection of a power generation system that includes transformermeasurement .......................................................................................................................................58

C.4 Meter panel (that may also be arranged in a decentralised manner) for the connection of apower generation system for self consumption or excess feed-in in accordance with EEG,§ 33 and KWK-G, § 4............................................................................................................................59

C.4.1 General.................................................................................................................................................59

C.4.2

Schematic representation ....................................................................................................................60

C.4.3 Organisation of a central meter panel..................................................................................................60

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Page

Annex D (normative) Islanding detection........................................................................................................ 62

D.1 Islanding detection by means of the oscillating circuit test.................................................................. 62

D.2 Islanding detection by three-phase voltage monitoring....................................................................... 63

Annex E (informative) Examples for the connection evaluation of power generation systems...................... 64

E.1

Connection of a 20 kW photovoltaic system ....................................................................................... 64

E.2 Reactive power control of a heat led CHP .......................................................................................... 69

Annex F (normative) Forms (mandatory) ....................................................................................................... 71

F.1 initial start-up protocol for power generation systems......................................................................... 71

F.2

Data sheet for power generation systems........................................................................................... 72

F.3 Requirements for the test report for power generation units............................................................... 73

F.4 Requirements for the test report for the NS protection ....................................................................... 74

Annex G (informative) Forms (optional).......................................................................................................... 75

G.1 Application........................................................................................................................................... 75

G.2 Certificate of conformity for power generation units............................................................................ 76

G.3 Certificate of conformity of the network and system protection........................................................... 77

Bibliography ..................................................................................................................................................... 78

Figure 1 — Synchronous generated voltage of a synchronous generator as an ideal balanced three-phase system ...................................................................................................................................... 23

Figure 2 — Equivalent circuit diagram of a synchronous generator for the case of a short circuit ................. 23

Figure 3 — Active power reduction at overfrequency...................................................................................... 25

Figure 4 — Limit power range for the reactive power of a power generation system within the range

of 3,68 kVA 13,8 kVA (load-reference arrow system)...................................................................... 27 ∑ EmaxS

Figure 6 — Standard characteristic curve for cos ϕ ( P ) ................................................................................... 28

Figure A.1 — Overview on the concepts of power generation unit and power generation system................. 40

Figure A.2 — Potential for optimisation provided by a suitable reactive power feed-in for typicaloverhead line or cable types (related to an operation mode where cos ϕ = 1).................................... 44

Figure A.3 — Examples of a characteristic curve cos ϕ ( P ) with three nodes ................................................. 45

Figure B.1 — Connection of a single-phase power generation unit with full feed-in and a maximumapparent connection power ≤ 4,6 kVA................................................................................................. 48

Figure B.2 — Connection of 3 single-phase power generation units with full feed-in and a maximumapparent connection power ≤ 4,6 kVA per line conductor................................................................... 49

Figure B.3 — Connection of 3 single-phase power generation units in full feed-in and withcommunicative coupling...................................................................................................................... 50

Figure B.4 — Connection of 3 three-phase power generation units with full feed-in ...................................... 51

Figure B.5 — Connection of a new power generation unit connected in parallel to an existingsystem with full feed-in for a maximum apparent connection power S Amax >30 kVA......................... 52

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Foreword

This VDE application guide has been prepared under the responsibility of the Forum Network Techno-logy/Network Operation within VDE (FNN). It has been prepared by the project group „Erzeugungsanlagenam Niederspannungsnetz“ (Power generation systems connected to the low-voltage distribution network)founded by the FNN steering committee “Low and medium voltage.”

This VDE application guide was subject to public opposition proceedings.

Introduction

The VDE application guide summarizes the essential aspects which have to be taken into consideration forthe connection of power generation systems (translator’s note: the German term “Anlage” includes systemsas well as installations and plants) to the network operator’s low-voltage network. It serves as a basis for boththe network operator and the installer in the planning and decision-making process. In addition, the operatoris given important information regarding the operation of such systems.

This VDE application guide replaces the 4 th edition of the VDEW guideline on “Generating Plants Connectedto the Low-Voltage Network” („Eigenerzeugungsanlagen am Niederspannungsnetz“) [1] which has been fullyredesigned and restructured to be more logical.

Similar to the higher voltage levels, power generation systems supplying low-voltage networks will have tomake a contribution to the static voltage stability in the future. Therefore, they have to contribute to thevoltage stability in the low-voltage network during normal network operation. This has immediate effect on thesystems’ design. This VDE application guide summarizes the essential aspects that have to be taken intoconsideration for the connection to the low-voltage network so as to maintain the safety and reliability ofnetwork operation in accordance with the provisions of the Energy Industry Act in the light of a growing shareof decentralised power generation systems and to enable the limit values of voltage quality specified inDIN EN 50160 to be observed.

Additional information is given for individual aspects to explain certain provisions of the VDE applicationguide. In order to reduce this VDE application guide to the most important elements, this explanatoryinformation is summarized in Annex A in correspondence to the respective clauses.

The calculation examples listed in Annex E allow for the permissibility of the connection of a power genera-tion system to the low-voltage network to be checked based on the given data. If, in that context, connectionto the low-voltage network is shown to be impossible, then connection to the higher voltage level, i.e. themedium-voltage network, may generally be considered. The connection evaluation required for this shall becarried out in accordance with the BDEW guideline “Generating Plants Connected to the Medium-VoltageNetwork” („Erzeugungsanlagen am Mittelspannungsnetz“) [2].

The Annexes F and G contain forms for the compilation of the required data of a power generation systemfrom planning the network connection to the initial start-up of the power generation system.

This VDE application guide is an integral part of the VDN guideline „Technische Anschlussbedingungen fürden Anschluss an das Niederspannungsnetz“ (Technical connection conditions for connections to the low-voltage network; TAB 2007) [3].

1 Scope

This VDE application guide applies to the planning, erection, operation and modification of power generationsystems that are connected to a network operator’s low-voltage network and operated in parallel with thisnetwork (network connection point in the low-voltage network). In this context, in particular those modifica-tions to power generation systems have to be taken into account, which have significant influence on theelectrical behaviour at the network connection.

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For the planning of a network connection as well as for the reconstructed and extended part of a powergeneration system, the Technical Connection Conditions (TCC) valid at the time of filing the application shallapply. Network connection modifications include reconstruction, extension, deconstruction or dismantling of acustomer installation as well as modification of the maximum apparent power S Amax of a power generation

system or modification of the network protection strategy.

NOTE 1 If clauses or conditions of the TAB 2007 [3] are referred to in the following, then these are always references to

specifically the respective indication of TAB 2007 [3]. In other contexts, the technical connection conditions of the networkoperators are cited which are generally based on TAB 2007 [3] and which the network operators have to communicate tothe relevant regulation authority.

This VDE application guide also applies to standby electric systems (emergency power generators) whoseoperation in parallel with the public network exceeds the short-time parallel operation permissible forsynchronisation of ≤ 100 ms.

For power generation systems that are connected on the low-voltage side but also, via a separate customertransformer, to the network operator’s medium-voltage network, the connection point is on the medium-volt-age network. For their connection evaluation the BDEW guideline „Erzeugungsanlagen am Mittelspannungs-netz“ [2] shall be used.

NOTE 2 In that context, power generation systems, that are connected to a customer owned low-voltage networkprimarily designed for extraction, may be connected to and operated with a maximum apparent connection powerΣS Amax ≤ 100 kVA (sum all power generation systems connected to that low-voltage network and not meeting the require-

ments of the BDEW guideline „Erzeugungsanlagen am Mittelspannungsnetz“ [2]) in accordance with the present guideline“Power generation systems connected to the low-voltage distribution network.”

Power generation systems include:

– water-power systems;

– photovoltaic systems (PV systems);

– generators mechanically coupled with thermal engines, e.g. in combined heat and power units (CHP);

– fuel cell systems.

The electrical energy can be generated by synchronous or asynchronous generators with or without invertersof by direct-current generators (e.g. solar cells of photovoltaic systems) with inverters. The maximumapparent connection power up to which connection to the low-voltage network is permissible depends on thetype and mode of operation of the power generation system as well as on the network conditions.

2 Normative references

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

DIN 18015-2, Electrical installations in residential buildings — Part 2: Nature and extent of minimum equip-ment

DIN 43870, Meter mounting boards

DIN 43880, Built-in equipment for electrical installations — Overall dimensions and related mounting dimen-sions

E DIN EN 45011:1998-03, General requirements for bodies operating product certification systems(ISO/IEC EN 45011:1998-1996)

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

DIN EN 50438 (VDE 0435-901), Requirements for the connection of micro-generators in parallel with publiclow-voltage distribution networks

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DIN EN 60909-0 (VDE 0102), Short-circuit currents in three-phase a.c. systems — Part 0: Calculation ofcurrents

DIN EN 61000-3-2 (VDE 0838-2), Electromagnetic compatibility (EMC) — Part 3-2: Limits — Limits forharmonic current emissions (equipment input current ≤ 16 A per phase)

DIN EN 61000-3-3 (VDE 0838-3), Electromagnetic compatibility (EMC) — Part 3-3: Limits — Limitation ofvoltage changes, voltage fluctuations and flicker in public low-voltage supply systems, for equipment with

rated current ≤ 16 A per phase and not subject to conditional connection

DIN EN 61000-3-11 (VDE 0838-11), Electromagnetic compatibility (EMC) — Part 3-11: Limits — Limitation ofvoltage changes, voltage fluctuations and flicker in public low-voltage supply systems; Equipment with rated

current ≤ 75 A and subject to conditional connection

DIN EN 61000-3-12 (VDE 0838-12), Electromagnetic compatibility (EMC) — Part 3-12: Limits — Limits forharmonic currents produced by equipment connected to public low-voltage systems with input current > 16 Aand ≤ 75 A per phase

DIN EN 61000-4-7 (VDE 0847-4-7), Electromagnetic compatibility (EMC) — Part 4-7: Testing and mea-surement techniques — General guide on harmonics and inter-harmonics measurements andinstrumentation, for power supply systems and equipment connected thereto

DIN EN 61000-4-30 (VDE 0847-4-30), Electromagnetic compatibility (EMC) — Part 4-30: Testing andmeasurement techniques — Power quality measurement methods

DIN VDE 0100-460 (VDE 0100-460), Erection of power installations — Part 4: Protection for safety;Chapter 46: Isolation and switching

DIN VDE 0100 (VDE 0100), Erection of low-voltage installations

DIN VDE 0100-200 (VDE 0100-200), Low-voltage installations — Part 200: Definitions

DIN VDE 0100-410 (VDE 0100-410), Low-voltage electrical installations — Part 4-41: Protection for safety —Protection against electric shock

DIN VDE 0100-551 (VDE 0100-551), Low-voltage electrical installations — Part 5-55: Selection and erectionof electrical equipment — Other equipment — Clause 551: Low-voltage generating sets

DIN VDE 0100-712 (VDE 0100-712), Low-voltage installations — Part 7-712: Requirements for specialinstallations or locations — Solar photovoltaic(PV) power supply systems

DIN VDE 0105 (VDE 0105), Operation of electrical installations

DIN VDE 0105-100 (VDE 0105-100):2009-10, Operation of electrical installations — Part 100: Generalrequirements

DIN VDE 0603 (VDE 0603), Consumer distribution boards and meter panels AC 400 V

VDE-AR-N 4400:2011-08, Electricity Metrology (Metering Code)

3 Terms, definitions and abbreviations

3.1 Terms and definitions

For the purposes of this document the following terms and definitions apply.

3.1.1system operatorentrepreneur, or a natural or legal person acting on his behalf, assuming the entrepreneur’s responsibility forsafe operation and proper condition of the customer’s system, installation or plant (T.N.: in the followingalways called system)

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3.1.2system erectorpersons or enterprises erecting, expanding, modifying or running an electrical installation or system as well aspersons or enterprises who, though not having erected, expanded, modified or run this electrical system,have checked the executed works as experts and assume the responsibility for their proper execution

3.1.3

connection ownerany natural or legal person (e.g. owner) whose electrical system is connected through a supply connectiondirectly to the network of the network operator

NOTE The connection owner has a legal relationship with the network operator.

3.1.4automatic reclosing (AR; ge: Automatische Wiedereinschaltung, AWE)reclosing, by an automatic device, of a circuit breaker assigned to a faulty network part assuming that thefault disappears during the time of interruption

3.1.5rated current I r

current the respective device of installation is designed to be permanently operated with by the manufactureror on the basis of a standard

3.1.6three-phase system

3.1.6.1ideal three-phase systemsymmetric three phase system with the following characteristics:

1) electric symmetry of the power generation units, i.e.:

a) the r.m.s. values of the three phase to neutral or line voltages, respectively, are equal,

b) all voltages have the same frequency f or angular frequency ϖ = 2 π f ,

c) the phase displacement between the individual voltages is 120°;

2) symmetrically designed equipment, i.e. equal positive-sequence and negative-sequence impedances;

3) symmetric loading

3.1.6.2real three-phase systemthree-phase network in which the balance of the line voltages can be disturbed due to the influence ofunbalanced loads and power generation systems feeding non-symmetrically

3.1.7final circuitelectric circuit intended to supply directly electric current to current using equipment or socket-outlets

3.1.8power generation system (ge: Erzeugungsanlage, PGS)all power generation units using the same primary energy carrier (e.g. all PV units) connected to a powerport/house connection (also see Annex A)

NOTE Unit symbols relating to the power generation system are given the index “A”.

3.1.9power generation unit (ge: Erzeugungseinheit, PGU)individual unit for the generation of electrical energy (also see Annex A)

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NOTE 1 For a photovoltaic unit, this may be, e.g., the inverter including the components/solar modules connecteddownstream (from the network point of view). Thus, a photovoltaic power generation system with two inverters firmlyconnected to the meter panel consists of two power generation units.

NOTE 2 Unit symbols relating to the power generation unit are given the index “E.”

3.1.10

flickervoltage fluctuations producing the subjective impression of fluctuations in the luminance via the functionalchain electric lamp—eye—brain

3.1.10.1short-term flicker strength P st

quantity for the assessment of flicker-effective voltage fluctuations of a time interval of 10 min

NOTE Here, the index “st” indicates short term.

3.1.10.2long-term flicker strength P lt

quantity for the assessment of flicker-effective voltage fluctuations of a time interval of 120 min

NOTE Here, the index “lt” indicates long time.

3.1.11readily accessible disconnection deviceaboveground connection point of the house connection cable to the network operator’s low-voltage network(e.g. cable connection cabinet, cable distributor cabinet, transformer station, house connection box), providedthat it is freely and readily accessible to the staff of the network operator

3.1.12customer installationthe electrical installation as specified in NAV, § 13 and § 14 and, thus, with the exception of the measuringdevice(s), all electrical apparatus downstream of the supply point that is used to supply the network users

3.1.13short-circuit power

3.1.13.1

initial short-circuit power kS ′′

initial symmetrical short-circuit power decisive for the calculation of the short-circuit strength in accordancewith DIN EN 60909-0 (VDE 0102):

knk 3 I U S ′′⋅⋅=′′

3.1.13.2

network short-circuit powerkN

S ′′

short-circuit power available on the network side without the share of the power generation system that is tobe connected

3.1.13.3network short-circuit power S kV

the network’s short-circuit power (based on the sustained short-circuit power) at the point of commoncoupling (PCC), which is decisive for the calculation of network interactions

NOTE Cf. reference [4]. It is generally lower than the short-circuit power used for rating the short-circuit strength ofsystems and installations.

3.1.14

short-circuit current k I ′′initial short-circuit current in accordance with DIN EN 60909-0 (VDE 0102)

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3.1.15short interruptionshort interruption caused by automatic disconnection of a fault followed by an AR or other short-terminterruptions

3.1.16power

3.1.16.1rated apparent power S rE

apparent power that the components of the power generation unit are designed for

3.1.16.2reactive power Q part of the apparent power that does not contribute to the generation of electrical energy

NOTE It is the product of the apparent power and sine of the phase displacement angle ϕ between the fundamentalcomponents of the line to neutral point voltage U and the current I .

3.1.16.3maximum apparent power of a power generation system

S Amax

ratio of the maximum active power of the power generation system P Amax to the displacement factor cos ϕ

prescribed by the network operator

ϕ cos Amax

Amax P

S =

NOTE S Amax is used as a basis for the network connection test .

3.1.16.4maximum apparent power of a power generation unit S Emax

ratio of the maximum active power of the power generation system P Emax to the displacement factor cos ϕ

prescribed by the network operator

ϕ cosEmax

Emax P

S =

3.1.16.5maximum active power of the power generation unit P Emax

highest active power of a power generation unit which is obtained as the highest mean value possible duringa period of 10 min

3.1.16.6maximum active power of the power generation system P Amax

highest active power of a power generation system resulting from the sum of the maximum active powers ofthe power generation units ( )∑= Emax Amax P P

3.1.16.7apparent power S product of the r.m.s. values of the line-to-neutral voltage and the current carried by the individual lines

3.1.16.8active power P electric power relevant for the generation of electrical energy available for conversion into other forms ofenergy (e.g. mechanical, thermal or chemical)

NOTE This is the nominal power of the power generation unit given by the manufacturer for nominal conditions. Forcalculation purposes, the power of the apparatus on the network side (e.g. the inverters) is to be used.

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3.1.17

power factorratio of the magnitude of the active power P to the apparent power S :

S

P =λ

NOTE Just like P and S , λ relates to the r.m.s. values of the total alternating quantity, i.e. to the sum of their funda-mental component and all harmonics.

3.1.18maximum switching current factor K imax

ratio of the highest current occurring during a switching operation (e.g. starting or connecting current or thehighest breaking current under normal operating conditions) to the normal generator current I nG. For this, the

current is to be considered as an r.m.s. value over a period

3.1.19medium-voltage network

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3.1.28self-monitoringfunction which is normally executed within the protective device and is intended to automatically detect faultswithin and outside the protective device

3.1.29voltage

3.1.29.1rated voltage U r

voltage of a device or installation for which the device or installation has been designed for permanentoperation on the basis of a given standard or by the manufacturer

3.1.29.2operating voltage U b

voltage as the r.m.s. value (10-minute mean value) of the line-to-line voltage occurring during normaloperation in a certain point of the network and at a given point in time

3.1.29.3nominal voltage U n

voltage by which a network or system is described or identified

3.1.30

voltage change U max increase or decrease of the r.m.s. value of a voltage where a distinction is made between slow and rapidvoltage change

NOTE When indicating a relative voltage change, the voltage change of the line-to-line-voltage is related to theoperating voltage of the network:

b

max

U

U u ∆=∆

3.1.30.1slow voltage changevoltage increase or decrease (10-minute mean value) usually attributable to changes of the total load/totalfeed-in in a network or in a part of the network

3.1.30.2rapid voltage changea single rapid change of the r.m.s. value of a voltage between two consecutive voltage values of certain butnot specified durations

3.1.31over-excitedoperating condition of a synchronous generator, where the generator absorbs capacitive reactive power fromthe network

3.1.32supply pointnetwork point which represents the boundary between the network operator’s area of responsibility and thatof the operator of the connection system

NOTE The supply point is mainly of importance in the context of operation management. It is not always identical withthe property line.

3.1.33transfer factor ü ratio of the rated voltages of high-side and low-side voltage of transformers

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3.1.34under-excitedoperating condition of a synchronous generator, where the generator absorbs inductive reactive power fromthe network

3.1.35point of common coupling (PCC)

point in the public network closest to the customer system to which further customer systems are connectedor can be connected

NOTE The PCC is generally identical with the network connection point. It is used as a basis for the assessment ofnetwork reactions.

3.1.36

displacement factor cos cosine of the phase angle between the fundamental components of the line to neutral point voltage and therespective current

3.1.47

inter-harmonics µ

sinusoidal oscillation whose frequency is not an integral multiple of the fundamental frequency (50 Hz)

NOTE Inter-harmonics may also occur in the frequency range between 0 Hz and 50 Hz.

3.2 Abbreviations

For the purpose of this VDE application guide, the following abbreviations and symbols apply in additionthose given in the series of standards DIN EN 50173.

AR Automatic reclosing (ge: Automatische Wiedereinschaltung, AWE)

BGV Provisions of the institutions for statutory accident insurance and prevention(ge: Berufsgenossenschaftsvorschriften)

CHP Combined heat and power unit (ge: Blockheizkraftwerk, BHKW)

BKE Fastening and contacting device (ge: Befestigungs- und Kontaktiereinrichtung)

EMF Electromotive force (Elektromotorische Kraft, EMK)

PGS Power generation system (ge: Erzeugungsanlage, EZA)

PGU Power generation unit (ge: Erzeugungseinheit, EZE)

EL(circuit breaker) Earth leakage (circuit breaker) (ge: FI(Fehlerstrom)-Schutzschalter)

CHP Cogeneration of power and heat (ge: Kraft-Wärme-Kopplung, KWK)

NS protection Network and system protection (ge: Netz- und Anlagenschutz, NA-Schutz)

PEN Protective earth neutral conductor (ge: Schutz- und Neutralleiter)

PV Photovoltaic

RCD Residual Current Protective device (ge: Fehlerstrom-Schutzschalter)

TRA Audio-frequency centralised ripple control systems (ge: Tonfrequenz-Rundsteueranlagen, TRA)

TRBS Technical rules for operational safety (ge: Technische Regeln für Betriebssicherheit)

TN-C Combined protective and neutral conductor (fr: Terre Neutre Combiné)

TN-S Separate protective and neutral conductor (fr: Terre Neutre Séparé)

TT Separate protective conductor (fr: Terre Terre)

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4 General framework conditions

4.1 Provisions and regulations

Power generation systems shall be erected and operated, taking into consideration the valid provisions andregulations, in such a way that they are suitable for parallel operation with the network operator’s low-voltagenetwork and so that inadmissible reactions on the network or other customer systems are excluded. This alsoimplies that the maximum apparent power of a power generation system S Amax is not exceeded.

For the erection and operation of the electrical installations it is imperative to comply at least with:

– the applicable statutory and governmental provisions;

– the applicable DIN standards and DIN VDE standards, in particular DIN VDE 0100 (VDE 0100) and,thus, also DIN VDE 0100-551 (VDE 0100-551) that has been harmonised on the European level;

– the occupational health and safety provisions and the accident prevention regulations of the relevantinstitutions for statutory accident insurance and prevention;

– the provisions and guidelines of the network operator, in particular the technical connection conditions(TCC).

Any work on the electrical installation downstream of the service fuse shall only be carried out by anelectrician who is listed in an electrician’s directory of the network operators. The only exceptions aremaintenance works downstream of the measuring device.

If justified, the network operator may, on a case-by-case basis, demand modifications and additions toexisting systems or to systems to be erected as far as this is required for a safe and disturbance-free supply.

4.2 Application procedure and connection relevant documents

The network operator shall be involved as early as in the planning phase. As a rule, the following documentsshall be submitted to the network operator on time and in compliance with the application procedure applic-able in accordance with TAB 2007 [3]:

– application for connection to the network (usually a pre-printed form of the network operator, or else theform “Application” given in Annex G.1);

– site map indicating the plot number and showing the designation and boundaries of the plot as well asthe place where the power generation system is to be installed;

– data sheet with the technical data of the system (see Annex F.2);

– indication whether the system operator wishes for full or excess feed-in (see Annex F.2);

– for every power generation unit a certificate of conformity as well as the associated test report. Thisconformity certificate/test report indicates the electrical characteristics of the power generation unit andconfirms its conformity with the requirements of this guideline (see annexes F.3 and G.2);

– description of the protective devices in accordance with Clause 6 and a certificate of conformity for the

network and system protection as well as the associated test report (NS protection; see Clause 6 or theannexes F.4 and G.3, respectively);

– complete circuit diagram of the power generation system’s connection to the low-voltage network withthe data of the apparatus used, incl. the arrangement of the measuring and protective devices as well asthe arrangement of the meter panels (that includes decentralized meter panels). Also see Annex B.

4.3 Initial start-up of the power generation system

At the latest one week prior to the scheduled initial start-up of the power generation system, the systemerector submits to the network operator the fully completed and signed order for initial start-up. For this, thesystem erector uses a procedure customary with the network operator.

An initial start-up of a power generation system without the network operator’s consent can put the safety ofnetwork operation and the power quality in the network at risk and is therefore not permitted.

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The date of initial start-up of the power generation system and the date of first parallel operation shall beagreed upon between system erector and network operator.

For the initial start-up of heat-led CHP systems with a monovalent mode of operation (no other heat generatorpresent), the start-up should be as quick as possible.

The initial start-up of the power generation system is carried out by the system erector. For this, the network

operator and system operator have to agree as to whether or not the network operator’s presence is required.The system erector shall prepare an initial start-up protocol (see Annex F.1).

The system erector shall confirm on this initial start-up protocol that the power generation system has beenerected in accordance with the technical connection conditions listed in this VDE application guide.

The completed initial start-up protocol shall be signed in duplicate. One copy shall remain with the systemoperator and is to be kept as proof of the executed tests. The second copy shall be handed over to thenetwork operator.

For the initial start-up of the power generation system the following procedure shall be followed:

– inspection of the system;

– comparison of the system set-up with the planning specifications; – comparison of the set-up of the measuring device for billing purposes with the contractual and technical

specifications;

– execution of a start control procedure for the meters for supply and, if necessary, extraction;

– check of the connection/disconnection of the external reactive current compensation system with theassociated power generation system (if present);

– for power generation systems with system powers of more than 100 kW: check of the technicalequipment for the reduction of the feed-in power within the framework of generation management/feed-inmanagement/network security management;

– check of the equipment for monitoring the maximum apparent connection power (if monitoring is requiredby the network operator).

In the case of central NS protection (network and system protection; see Clause 6), the system erector is inaddition required to carry out a trigger test in order to test the trigger circuit “NA protection — interfaceswitch.” To this end, the central NS protection is equipped with a test button which when operated activatesthe interface switch. Activation shall be visualised at the interface switch.

The setting value for the rise-in-voltage protection U > in the NS protection closest to the network connection(this may be the central or the integrated NS protection) shall be verified and, if necessary, adjusted to 1,1 U n

and it shall be documented in the initial start-up protocol F.1.

Both central and integrated NS protections shall be sealed after the initial start-up of the power generationsystem or else shall be protected by password entry. The password shall not be made available to the system

operator.

5 Network connection

5.1 Principles for determination of the network connection point

Power generation systems shall be connected at a suitable point in the network, i.e. the network connectionpoint. Based on the documents listed in 4.2, the network operator determines the suitable network connectionpoint that ensures safe network operation, also when taking account of the power generation system, and atwhich the power applied for can be drawn and transmitted. The decisive aspect for evaluation of the networkconnection is always the behaviour of the power generation system at the network connection point or at thePCC. This is to ensure that the power generation system is operated without interfering reactions and without

affecting the supply of other customers. Annex E shows examples for connection evaluations of powergeneration systems.

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As a rule, power generation systems are connected to the supply point of the extraction system.

In individual cases it can be required to create a separate supply point in accordance with TAB 2007 [3] forconnection of the power generation system that is connected via a separate network connection line. It shallbe ensured that the power generation system is fully separated (electrically) from any other current-usingequipment of the customer. The supply point for the current-using equipment shall be marked with areference to the locality of the supply point for the power generation system.

Power generation systems which are installed on different plots with their own respective network connec-tions shall, as a rule, not be connected to the network operator’s network together in the same networkconnection point. Power generation systems installed on a building with several network connections may beconnected to the network operator’s network together at the same network connection point (supply pointmarking as described above).

All separate supply points shall be permanently marked by the supply point owner with the following label“Sectioning point: power generation system/supply network”.

For the purposes of evaluating the connectivity with regard to the network reactions, the impedance of thenetwork at the PCC (network short-circuit power, resonances), the maximum apparent connection power aswell as the type and operation mode of the power generation system are considered. The evaluation is made

assuming the regular switching state and undisturbed operation of the network. If more than one powergeneration system is connected in the same low-voltage network, their total effect shall be considered. Forcircuit modifications that are required for maintenance or forced outage reasons, it be required for thedetermined network connection point to temporarily reduce the power generation system’s output power or todisconnect it from the network. Examples of connections are given in Annex B.

5.2 Rating of the network equipment

Due to their operation mode, power generation systems may cause higher loading of lines, transformers andother network equipment. Therefore, the network operator examines the loading capacity of the networkequipment with regard to the connected power generation systems in accordance with the relevant ratingregulations.

For calculation purposes the maximum apparent power of the sum of all power generation systems ∑ AmaxS and usually the load factor m = 1 shall be used. The only exception are buried cables for the connection ofphotovoltaic systems for which a load factor m = 0,7 shall be used.

5.3 Permissible voltage change

For undisturbed operation of the network, the amount of the voltage change caused by all power generationsystems with a network connection point in a low-voltage network shall at none of the PCCs in this networkmay a value of 3 % as compared with the voltage without power generation systems:

∆ua ≤ 3 % (1)

If stipulated by the network operator and, if necessary, taking into account the possibilities of the staticvoltage stability it may be permitted in individual justified cases to deviate from this value of 3 %.

NOTE Depending on the resulting displacement factor of all power generation systems, the voltage change can bepositive or negative, i.e. the voltage may rise or fall.

When calculating the voltage change, the displacement factor shall be taken into account which is providedby the network operator for the maximum apparent connection power of the power generation system S Amax.

For determination of the voltage changes for meshed low-voltage networks and high spatially distributedfeed-in powers, it is recommended to use complex load-flow calculations.

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5.4 System reactions

5.4.1 General

The electrical installations of the customer system shall be planned, constructed and operated so thatreactions to the network operator’s network and to the systems of other customers are permanently reducedto a permissible minimum. Should interfering reactions on the network operator’s network occur nonetheless,

the customer shall apply measures to his system that are to be coordinated with the network operator. Thenetwork operator is entitled to disconnect the power generation system concerned from the network until thedeficiencies are corrected.

The connection owner provides the network operator with values from the device documents of the manu-facturer which are necessary in order to evaluate system reactions (see Annex F.3).

If connection of several power generation systems would result in exceedance of the flicker limits at the mostunfavourable PCC, then measures shall be taken which result in the flicker limits being complied with at themost unfavourable point. Responsibility for implementation of these measures lies in turn with the systemoperator whose system contributes the greatest share of flicker strength.

5.4.2 Rapid voltage changes

Voltage chances at the PCC attributable to the simultaneous connection and disconnection of power genera-tion units do not give rise to inadmissible network reactions if the maximum voltage change does not exceeda value of 3 % (related to U n) at the PCC:

∆umax ≤ 3 % (2)

For a value of 3 % the frequency shall not exceed once every 10 min.

Depending on the network short-circuit power S kV at the PCC of maximum apparent connection power S Emax

of the activated power generation unit and on the ratio of starting current I a to rated current I rE, the voltage

change can be estimated as follows:

kV

Emax

rE

a

kV

Emaximaxmax

S

S

I

I

S

S k u ⋅==∆ (3)

5.4.3 Flicker

Flicker describes a phenomenon which is characterised by voltage fluctuations whose frequency and ampli-tude are of a magnitude that causes lamps supplied with this voltage to show disturbing brightness fluctua-tions. Further details are given in [4]. The measured variable and the evaluation criterion for flicker caused bypower generation systems is the long-term flicker strength P lt.

For power generation systems with rated currents of up to 75 A, reactions are deemed to be limited sufficient-ly, if the power generation units comply with the limit values given in DIN EN 61000-3-3 (VDE 0838-3) orDIN EN 61000-3-11 (VDE 0838-11), respectively.

Together, all power generation systems in the low-voltage network shall not exceed the following flickerstrength at the most unfavourable PCC:

Long-term flicker strength: P lt = 0,5 (4)

This value also applies to power generation systems with rated currents above 75 A.

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5.4.4 Harmonics and inter-harmonics

The currents of harmonics and inter-harmonics generated by power generation systems shall be included inthe conformity check (see Clause 9).

For power generation systems reactions are deemed to be limited sufficiently, if the power generation unitscomply with the following limit values:

– for rated currents of up to and including 16 A per conductor: the limit values of class A (Table 1) specifiedin DIN EN 61000-3-2 (VDE 0838-2);

– for rated currents above 16 A and up to and including 75 A per conductor: the limit values of Table 2 andTable 3 specified in DIN EN 61000-3-12 (VDE 0838-12).

If in the standards mentioned above, limit values are explicitly stated for power generation units, then theselimit values shall apply.

If the limit values of DIN EN 61000-3-2 (VDE 0838-2) or DIN EN 61000-3-12 (VDE 0838-12), respectively, arenot complied with, then the maximum permissible harmonic currents I vzul of a power generation system are

calculated from the related harmonic currents ivzul of Table 1 multiplied by the network short-circuit power at

the PCC (minus the power generation system’s share in short-circuit power):

I vzul = ivzul ⋅ S kV (5)

Table 1 also applies for power generation systems with rated currents above 75 A.

If several power generation systems are effective at this PCC, then the currents to be evaluated inaccordance with Table 1 are obtained by superposition of the individual currents in accordance with A.3.3.

Table 1 — Permissible harmonic currents related to the network short-circuit power S kV

that may be supplied in a network connection point

Ordinal number ν, µ Permissible related harmonic current i vzul in A/MVA

3 3

5 1,5

7 1

9 0,7

11 0,5

13 0,4

17 0,3

19 0,25

23 0,2

25 0,15

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Harmonic currents shall be measured in accordance with DIN EN 61000-4-7 (VDE 0847-4-7).

NOTE Of the methods listed in DIN EN of 61000-4-7 (VDE 0847-4-7), the following shall be applied:

– in the case of harmonics: r.m.s. values of harmonic subgroups;

– in the case of inter-harmonics: r.m.s. values of inter-harmonic centred subgroups.

Harmonic currents which flow into the power generation system (e.g. into filter circuits) due to a distortednetwork voltage, are not assigned to the power generation system. The same shall apply if the powergeneration system works as an active harmonics filter and, due to its operating mode, brings about acontinuous reduction of harmonic voltages existing in the network voltage. However, centralised multi-servicecontrol systems shall not be inadmissibly affected (see 5.4.7).

5.4.5 Voltage unbalance

If several single-phase power generation systems are connected to the same network connection point, thenuniform distribution of the power supplied to the three line conductors shall be aimed for, where a maximumpower difference of 4,6 kVA shall not be exceeded.

5.46 Commutation notches

The relative depth of commutation notches d kom through line-commutated inverters shall not exceed the

value of

d kom = 5 % (6)

at the PCC in the most unfavourable operational state (d kom = ∆U kom/ with = the peak value of the

nominal voltage U n).nU

ˆnU

ˆ

5.4.7 Audio-frequency centralised ripple-control

Audio-frequency centralised ripple-control are usually operated at frequencies between approx. 100 Hz and1 500 Hz. Information about the locally applied ripple-control frequency can be obtained from the networkoperator. Broadcasting levels of audio-frequency impulses are normally about 1 % U n to 4 % U n.

In principle, power generation systems may inadmissibly influence the ripple-control installations throughadditional load on the centralised ripple-control transmitting station or through an inadmissibly high reductionof the signal level in the system operator’s network.

As a matter of principle, the audio-frequency level caused by the operation of power generation systems shallnot be reduced by more than 5 % at any point of the low-voltage network as compared to the operationwithout power generation systems; power consumption and generation installations shall be taken intoaccount according to their audio-frequency impedance.

With this reduction of the audio-frequency level by power generation systems, it is necessary to take accountof the fact that power generation systems supplying the network through static inverters without filter circuitsdo normally not cause a substantial reduction of the ripple-control level. Where filter circuits or compensatingcapacitors are present, it is necessary to examine whether the short-circuit reactance of the systemtransformer may give rise to a series resonance.

Apart from the limitation of the level reduction, it is not allowed to generate inadmissible interference voltages.The following rules shall apply in particular:

– The interference voltage caused by a power generation system whose frequency corresponds to thelocally applied ripple-control frequency or is very close to it (± 5 Hz), shall not exceed the value of0,1 % U n.

– The interference voltage caused by a power generation system whose frequency lies at the ambientfrequencies of ± 100 Hz to the locally applied ripple-control frequency or in its immediate proximity, shallnot exceed a value of 0,3 % U n.

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These limit values as well as further details can be found in the guidelines on audio-frequency centralisedripple control („Tonfrequenz-Rundsteuerung“) [5].

Should a power generation system inadmissibly impair the operation of the centralised ripple-control systems,the operator of the power generation system shall take appropriate remedial measures even if the impairmentis noticed at a later date.

5.4.8 Carrier frequent usage of the customer network

If the system operator runs a system with carrier frequent usage of his network, then it shall be ensured bymeans of suitable devices (e.g. carrier frequency limitation) that interfering influences on other customersystems as well as on the systems of the network operator are avoided.

Shared usage of the network operator’s network by the customer is permitted solely with the networkoperator’s consent for the carrier frequent transmission of signals.

5.4.9 Precautionary measures against voltage drops and voltage interruptions

If power generation systems are sensitive to short-time voltage drops or interruptions of supply, then the

customer shall take suitable measures to safeguard the system and to ensure operation operational safety.

5.5 Connection criteria

For the technical execution of connections of the power generation system or the customer system with apower generation system, the technical connection conditions of the network operator shall be considered. Ifthe generated power is fully supplied to the network operator’s network, then the connection line of the powergeneration system shall be firmly connected to the meter panel within the customer system and the meterpanel shall then be executed in accordance with the applicable TCC (currently TAB 2007 [3]). When doing so,supply to the meter panel is always carried out via the upper connection compartment.

The exception are those power generation systems that are operated with excess feed-in (e.g. in accordancewith EEG [6], § 33 (2) or KWK-G [7], § 4 (3a)). In that case, the power generation systems may also be

connected in sub-distributions; ((this also applies to)) photovoltaic systems with a maximum active power P Amax of up to and including 30 kW. The meter panels for feed-in meters Z2 (see Clause 7 and connection

examples in Annex B) then shall be executed as follows:

a) for central arrangement: in accordance with the applicable TCC (i.e. at present TAB 2007 [3]);

b) for decentralised arrangement next to the power generation system in accordance with the applicableTCC (i.e. at present TAB 2007 [3]) or in the small distributor (≥ 2 TE) in accordance with DIN VDE 0603(VDE 0603), also with top hat rail meter;

c) for decentralised arrangement in the power generation unit (CE certified unit) taking into considerationthe standards for the respective fastening of the chosen meter construction (three point: DIN 43870, BKEunit: DIN 43870, measuring devices for top hat rail mounting in accordance with DIN 43880 Size 1, 2 or3).

NOTE 1 With regard to item c) above: Mounting space and type of connection are included in the CE certification.

NOTE 2 With regard to item c) above: Extension function “ability to communicate”: The equipment manufacturer shallpoint out in the technical data sheet that subsequent connection to, e.g., SmartGrid is impossible or else show how suchan (internal or external) extension can be achieved.

Connection to a final circuit is not permitted in any circumstance. With regard to that, the system erector shallalso exercise special care to check of the electrical installation with respect to line dimensioning andprotection.

Examples of meter panel configurations are given in Annex C.

According to the amended version of DIN VDE 0100-551 (VDE 0100-551), it is not required anymore to havean additional section point for the connection of a power generation system to the network operator’s low-

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voltage network. For this reason, the section point, that had to be accessible at any time, is omitted for newconnections of power generation systems to the network operator’s network in future. This has consequencesfor the network operator with regard to the network operation (see 8.2).

As a rule, power generation systems shall be designed and connected to the network as balanced three-phase generators (characteristics of a three-phase system are explained in 5.6, the term “three-phasesystem” is defined in 3.1.6).

Power generation systems may also be single-phase connected to the network, if the sum of all single-phaseconnected power generation units per network connection does not exceed the following:

≤ 4,6 kVA per line conductor (7)∑ EmaxS

Therefore, it is possible to connect in single phase, distributed to the three line conductors, at maximum

3 × 4,6 kVA = ≤ 13,8 kVA. As soon as the limits given above are exceeded at the network

connection point, any extension shall be three-phase connected to the three-phase system. This requirementmay also be satisfied by communicatively coupling single-phase connected power generation units of thesame primary energy carrier. For extensions, the single-phase inverters can be replaced by three-phaseinverters (see 5.6.3), thus enabling the 3 × 4,6 kVA single-phase to be used for the power generation units tobe newly connected.

∑ EmaxS

The communicative coupling between power generation units ensures the power generation system’sbalanced supply to the individual line conductors of the three-phase network in accordance with 5.6.3.

NOTE Thus, communicatively coupled power generation units act like balanced three-phase inverters ensuringbalanced currents even in the event of a failure of individual power generation units.

For all that, the maximum permissible imbalance of 4,6 kVA (design and operational state) at a single networkconnection point for the sum of all power generation systems applies here as well (see Annex B.4).

NOTE Thus, the formerly valid regulation that PV systems may feed-in no more than 110 % of their nominal inverter

power is obsolete.

Explanations with regard to the connection criteria are given in Annex A, whereas Annex B shows examplesfor the connection of power generation systems.

5.6 Three-phase network

5.6.1 General

Unbalanced loads or unbalanced feed-in by power generation systems will cause unbalanced currents tooccur in balanced three-phase systems which may also lead to unbalanced voltages in the network becauseof the voltage drops thus caused. The maximum permissible value of the voltage unbalance is specified in

DIN EN 50160 as a line voltage product feature.For the purposes of maintaining the symmetric characteristics of the three-phase network, three-phase powergeneration systems shall have the characteristics described in the following.

5.6.2 Three-phase synchronous generators

Synchronous generators generate an electromotive force (EMF) or synchronous generated voltage (open-circuit voltage), respectively, satisfying the conditions for ideal balance (see Figure 1).

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Figure 1 — Synchronous generated voltage of a synchronous generatoras an ideal balanced three-phase system

In the event of a short circuit, the currents are limited by three identical “internal resistances” which areassumed to be nearly pure reactances (short-circuit reactance). Figure 2 shows the equivalent circuit diagramof a synchronous generator for the case of a short circuit. For a salient-pole synchronous generator thefollowing applies by way of approximation: (p. u.).dg x x ′′=′′

Figure 2 — Equivalent circuit diagram of a synchronous generator for the case of a short circuit

Due to the balance of the synchronous generated voltage and the small short-circuit reactance of thegenerator ( ), unbalanced currents in synchronous generators lead to only small asymmetries at the

terminal voltages of the generator. The generators are — in terms of symmetric components — able todeliver currents not only in the positive sequence system, but also in the negative sequence system and,given a suitable connection, also in the zero sequence system. This way, voltage unbalance is counteractedby the supplied generator currents.

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5.7.2 Maximum permissible short-circuit current

Due to operation of a power generation system, the short-circuit current of the low-voltage network isincreased by the short-circuit current of the power generation system. Therefore, information about the short-circuit current of the power generation system to be expected at the network connection point has shall beprovided in accordance with 4.2. For determination of the short-circuit current contributed by the powergeneration system the following roughly estimated values can be assumed:

– for synchronous generators: 8 times the rated current;

– for asynchronous generators: 6 times the rated current;

– for generators with inverters: 1 time the rated current.

If the power generation system gives rise to a short-circuit current increase in the network operator’s networkin excess of the rated value, then connection owner and network operator shall agree upon appropriatemeasures limiting the short-circuit current from the generating facility.

5.7.3 Active power output

5.7.3.1 Basics

In the following cases, the network operator is entitled to require and to carry out a system shot-down:

– potential danger to the safety of system operation;

– congestion or risk of overload on the network operator’s network;

– risk of islanding;

– risk to the steady-state or dynamic network stability;

– rise in frequency endangering the system;

– repairs or execution of construction measures;

– operation of network stand-by systems;

– resynchronisation of sub-networks; – within the scope of the generation management/network security management (see 5.7.3.2.)

5.7.3.2 Generation management/network security management

Power generation systems with a system power of more than 100 kW shall be able to reduce their activepower in steps of not more than 10 % of the maximum active power P Amax. For every operational state and

from each and every operation point, it shall be possible for this power to be reduced to a set point providedby the network operator. This set point is generally provided at the network connection point gradually orcontinually and it corresponds to a percentage related to the maximum active power P Amax. In the past, the

following values have been shown to be suitable: 100 %/60 %/30 %/0 %. (Still, the generated power may alsobe lower. If all else is technically impractical, then this may also be achieved by shutting down the power

generation system.) The network operators do not interfere with the open-loop control of the powergeneration systems. They are merely responsible for the signalling. Dry contacts are normally used for this.

The sole responsibility for the reduction of feed-in power lies with the system operator. For this, the contrac-tual conditions have to be taken into consideration, in particular if this leads to the customer system extractingpower.

Variable power generation systems shall carry out the power output reduction to the respective set pointimmediately, however, at maximum within a minute. It shall be technically possible for these power genera-tion systems to reduce the power to the set point 10 % without automatic disconnection from the network, andonly at a value of less than 10 % of the maximum active power P Amax are they permitted to disconnect from

the network. All other power generation systems shall carry out the power output reduction to the respectiveset point within a maximum period of five minutes. If the set point is not reached within five minutes, then the

power generation system shall be disconnected.

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5.7.3.3 Active power feed-in at overfrequency

At frequencies between 50,2 Hz and 51,5 Hz, all adjustable power generation systems shall reduce (forfrequency increase) or increase (for frequency decrease) the active power P M generated instantaneously (at

the time of exceeding the mains frequency 50,2 Hz; freezing the value on the current level) with a gradient of40 % of P M per Hertz (see Figure 3). From this, it follows that the power generation unit will continuously

move up and down the frequency characteristic curve in the frequency range of 50,2 Hz to 51,5 Hz with

regard to its active power feed-in (“running along the characteristic curve”). The increment of the frequencymeasurement shall be ≤ 10 MHz.

If the mains frequency drops again to a value below 50,2 Hz and if the possible generation power is greater atthat instant than the active power P M (frozen value, see above), then the increase of the active power

supplied to the network operator’s network shall not exceed a gradient of 10 % of the maximum active power P Amax per minute.

At mains frequencies >51,5 Hz, the power generation system shall disconnect from the network immediately(see 6.5.2).

Hz50

Hz25020 mainsM

f P P

−=∆

, for 50,2 Hz ≤ f mains ≤ 51,5 Hz

Where:

P M is the power generated at the time of exceeding 50,2 Hz;

P is the power reduction;

f mains is the mains frequency.

There are no restrictions for frequencies of 47,5 Hz ≤ f mains ≤ 50,2 Hz.

Disconnection from the network is required for f mains ≤ 47,5 Hz and f mains ≥ 51,5 Hz.

Figure 3 — Active power reduction at overfrequency

As an alternative to active power reduction at overfrequency, non-variable power generation systems arepermitted to disconnect from the network in the frequency range of 50,2 Hz to 51,5 Hz; in that case, uniformdistribution of the disconnection frequency in maximum increments of 0,1 Hz shall be ensured by the manu-facturer for every type of system.

Power generation systems that are variable under certain conditions, e.g. only within the range of 70 % P Amax to 100 % P Amax, are permitted to be adjusted in correspondence to the characteristic curve. Outside the

adjustable range disconnection is then carried out in correspondence to the evenly distributed shut-down limitcurve.

Linear generators, such as corresponding stirling engines with a maximum apparent power S Amax of up to an

including 30 kVA are exempt from this regulation; for frequencies between 50,2 Hz and their maximumfrequency upper limit, they are permitted to stay connected to the network and they may disconnect if thisupper limit is exceeded, however, at the latest when a frequency of 51,5 Hz is reached or exceeded.

In the event of the disconnection frequency being exceeded, the power generation system shall disconnectfrom the network within a maximum period of one second.

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5.7.3.4 Active power feed-in at underfrequency

For frequencies between 47,5 Hz and 50,0 Hz, automatic disconnection from the network as a result of afrequency deviation is not permitted (however, linear generators, such as corresponding stirling engines witha maximum apparent power S Amax ≤ 30 kVA, are exempt from the 47,5 Hz requirement because they are

currently considered to be of minor system relevance).

5.7.4 Principles for network support

As a rule, power generation systems shall be able to contribute to the static voltage stability in the networkoperator’s network. Static voltage stability is understood to be the voltage stability in the low-voltage networkat which the slow voltage changes are maintained within compatible limits in the distribution network.

If required due to network related circumstances and by the network operator, then the power generationsystems shall contribute to the static voltage stability in the low-voltage network.

A dynamic grid support, i.e. voltage stability in the event of voltage drops in the higher voltage levels, is notrequired for power generation systems feeding into low-voltage networks.

5.7.5 Reactive power

Irrespective of the number of feed-in phases, power generation systems shall allow for operation undernormal stationary operating conditions in the voltage tolerance band U n ± 10% and in their permissible

operation points starting with an active power output of more than 20 % of the rated active power with thefollowing displacement factors cos ϕ :

– power generation system ∑ EmaxS ≤ 3,68 kVA:cos ϕ = 0,95 under-excited to 0,95 over-excited in accordance with DIN EN 50438 (no default given by the

network operator);

– power generation system 3,68 kVA 13,8 kVA:characteristic curve provided by the network operator within cos ϕ = 0,90 under-excited to 0,90 over-excited

(see Figure 5).

In the load-reference arrow system, this means the operation in Quadrant II (under-excited) or III (over-excited).

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Figure 4 — Limit power range for the reactive power of a power generation system within the

range of 3,68 kVA 13,8 kVA (load-reference arrow system)∑ EmaxS

Within the hatched triangles for the reactive power limit shown in Figures 4 and 5 the reactive power of thepower generation system shall be freely adjustable.

Upon a change in the active power, the reactive power shall be able to adjust itself automatically incorrespondence to the predefined cos ϕ .

Type and set points of the reactive power setting will be determined by the respective network conditions andcan therefore be provided individually by the network operator within the triangles for the reactive power limit.For power generation systems, whose power generation units feed over inverters or synchronous generatorscapable to generate reactive power, it is permitted to provide as default either:

a) a displacement factor/active power characteristic curve cos ϕ ( P ); or

b) a fixed displacement factor cos ϕ .

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If the network operator provides a characteristic curve, then any set point resulting from that curve shall beset automatically on the power generation unit within 10 seconds.

As a rule, characteristic curve based regulation shall not be applied for power generations systems with gene-rators directly coupled to the network which, due their very operational principle, cannot control the reactivepower and, therefore, use constant capacities (such as CHP with asynchronous or linear generators). In thatcase, the network operator provides a fixed displacement factor cos ϕ .

For power generation units with a generator directly coupled to the network, a transition period between start-up and reaching the reactive power set point of 10 minutes is permitted.

Implementation of the reactive power requirements is carried out at the generator terminals of the powergeneration units.

NOTE 1 A characteristic curve cos ϕ ( P ) may be provided by the network operator for power generation units feedingwith fluctuating power. Such power generation units include, e.g., PV systems or CHP with a generator coupled viainverters.

NOTE 2 A fixed displacement factor is appropriate for power generation units feeding with constant power, such asCHP with a generator coupled directly to the network (see example in E.2). Compliance with this default value can be

realised by means of suitable capac

generating plants connected to the vde-ar-n_4105

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