Guidelines for electricity generation facilities with a
rated current greater than 16 A per phase, which are
connected to the low-voltage network via inverters
22 October 2012
SFJ/AKN
These guidelines cover the basic requirements for electricity generation facilities
with a rated current exceeding 16 A per phase, which are connected to the lowvoltage network via inverters
Electricity generation facilities larger than 1.5 MVA are not covered by these
guidelines, as they are expected to be connected at the medium-voltage level.
Guidelines for such systems must be agreed with the grid companies.
Wind turbines/wind power stations are not covered by these guidelines, as they
are covered by Technical Regulation TF 3.2.5.
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Working group
These guidelines have been formulated by an industry working group
comprising:
•
•
•
•
•
•
•
•
•
•
The Danish Energy Association
The Danish Solar Cell Association
TEKNIQ
EnergiMidt
Dong Energy
Østjysk Energi
Schüco International
Danfoss Solar Inverters
Solarpanels
Energinet.dk
Reading instructions
These guidelines have been subdivided in relation to the phase current of the
electricity generation facility:
-
Electricity generation facilities larger than 16 A and up to and including 75 A
per phase
-
Electricity generation facilities larger than 75 A per phase
These guidelines make use of various terms and definitions. The most important
of these are explained in section 1. Terms and definitions used in the guidelines
have been highlighted in the text using italics.
The guidelines have been published by the system operator and can be
downloaded from www.energinet.dk.
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Table of contents
1.
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
1.10
1.11
1.12
1.13
1.14
1.15
Terminology and definitions ...................................................
Plant owner .........................................................................
Electricity generation facility ..................................................
Electricity generation facility connection point (PGC) .................
Public electricity supply network .............................................
Low-voltage network .............................................................
Supplier ..............................................................................
Rated power ........................................................................
Rated current .......................................................................
Grid faults ...........................................................................
Grid company ......................................................................
Nominal voltage ...................................................................
Normal output range .............................................................
Interconnected electricity supply system .................................
System operator...................................................................
Point of Connection (POC) .....................................................
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
2.10
2.11
Electricity generation facility connected to low voltage .............. 7
Voltage quality ..................................................................... 7
Engagement and synchronisation .......................................... 14
Asymmetry ......................................................................... 14
Active power regulation ........................................................ 14
Reactive power regulation..................................................... 15
Tolerance of voltage dips and peaks, FRT ............................... 17
Protection towards the grid ................................................... 17
System protection ............................................................... 18
Communication ................................................................... 18
Registration and documentation ............................................ 18
Decommissioning, changes or replacement ............................. 20
2.
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1. Terminology and definitions
1.1
Plant owner
The legal owner of the electricity generation facility
1.2
Electricity generation facility
Facility producing three-phase alternating current.
•
•
1.3
The electricity generation facility may consist of one or more units in the
same installation
The electricity generation facility may consist of one or more units directly
connected to the public electricity supply network
Electricity generation facility connection point (PGC)
The point in the public electricity supply network or the installation where the
electricity generation facility is connected.
•
•
1.4
When connected to the public electricity supply network, the electricity
generation facility connection point (PGC) may coincide with the point of
connection (POC), see figure 1.
When connected within the installation, the electricity generation facility
connection point (PGC) is the point in the installation where consumption is
connected, see figure 1.
If common grid protection is used, consumption must not be connected
after this protection.
Public electricity supply network
Transmission grids and distribution networks the purpose of which is to transmit
electricity for an indefinite group of electricity suppliers and consumers on the
terms laid down by public authorities.
The transmission grid is defined as the public electricity supply network with a
nominal voltage greater than 100 kV, while the distribution grid is defined as
the public electricity supply network with a nominal voltage lower than 100 kV.
1.5
Low-voltage network
The public electricity supply network with a nominal voltage of up to 1000 V AC.
1.6
Supplier
The company which supplies the electricity generation facility to the plant
owner. The supplier is responsible for ensuring that the electricity generation
facility complies with these guidelines.
1.7
Rated power
The highest nominal electrical output of an electricity generation facility under
nominal operating conditions. Stated in kW or kVA.
1.8
Rated current
The greatest nominal current from the electricity generation facility under
nominal operating conditions.
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1.9
Grid faults
Failure or faults in the public electricity supply network.
1.10 Grid company
An approved company which operates the distribution grid. The grid company is
the company which operates the grid the electricity generation facility is
physically connected to.
1.11 Nominal voltage
The voltage at a point of connection, e.g. 400 V for three-phase connection.
1.12 Normal output range
The normal output range specifies the voltage/frequency range within which the
facility must be able to constantly produce power, see section 2.
1.13 Interconnected electricity supply system
The public electricity supply network and associated facilities in a large region
which is interconnected for the purpose of joint operation.
1.14 System operator
The company with general responsibility for maintaining security of supply and
ensuring effective utilisation of an interconnected electricity supply system. The
system operator is Energinet.dk.
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1.15 Point of Connection (POC)
The point in the public electricity supply network where the electricity
generation facility or installation is connected.
•
In the case of direct connection to the public electricity supply network, the
electricity generation facility connection point (PGC) is the same as the
point of connection (POC), see figure 1.
10 kV
0,4 kV
PGC
POC
POC
Direkte tilsluttet til det kollektive
elforsyningsnet
Installationstilsluttet
PGC
Forbrug
Solcellepanel
Solcellepanel
POC: Tilslutningspunkt til det kollektive elforsyningsnet
PGC: Det elprducerende anlægs tilslutningspunkt
Figure 1
Example of points of connection
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2. Electricity generation facility connected to low
voltage
The normal output range is defined as the nominal voltage Un ±10% and is
within the 47.50-50.05 Hz frequency range.
The electricity generation facility must be designed for three-phase connection.
If the electricity generation facility consists of three single-phase units, it is also
considered to be a three-phase facility, see the requirements in section 2.3.
The requirements set in the guidelines apply at the point of connection (POC). If
the electricity generation facility complies with the requirements at the
electricity generation facility connection point (PGC), it is assumed that the
requirements are also met at the point of connection (POC).
2.1
Voltage quality
All inverters must be tested and certified for compliance with voltage quality
requirements. Voltage quality covers the following elements:
•
•
Flicker
Harmonic and interharmonic currents
Definitions and explanations for these terms can be read in detail in the
following standards, which also specify the associated limit values and
requirements:
•
•
•
•
DS/EN 61000-3-2 "Electromagnetic compatibility (EMC) – Part 3-2: Limits
- Limits for harmonic current emissions (equipment input current ≤ 16 A
per phase)"
DS/EN 61000-3-3 "Electromagnetic compatibility (EMC) – Part 3-3: Limits
– Limitation of voltage 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" (IEC61000-3-3)
DS/EN 61000-3-11 "Electromagnetic compatibility (EMC) – Part 3-11:
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"
DS/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 rated current >16 A and ≤75 A per
phase"
2.1.1
Electricity generation facilities producing between 16 A and 75 A per
phase
Electricity generation facilities producing between 16 A and 75 A per phase are
considered to comply with these guidelines if each inverter complies with the
above standards.
Compliance is demonstrated by submitting the necessary documentation, as
described in section 2.10.1
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2.1.2 Electricity generation facilities larger than 75 A per phase
For electricity generation facilities larger than 75 A per phase, the following
requirement must be met.
Compliance is demonstrated by submitting the necessary documentation, as
described in section 2.10.2
Flicker
The electricity generation facility's flicker contribution during continuous
operation, Plt, must be complied with at the point of connection (POC).
The following limit values must be observed for all electricity generation
facilities.
Plt ≤ 0.50
2.1.2.1 Electricity generation facilities consisting of a single unit
If an electricity generation facility consists of a single unit, flicker contribution,
Plt, is calculated in the following manner.
Plt = c (ψ k )⋅
Plt:
c (ψk):
1
25
long term flicker
flicker coefficient (value ψ=30° from the test
report)
2.1.2.2 Electricity generation facilities consisting of several identical units
If an electricity generation facility consists of several identical units, total flicker
contribution, Plt, is calculated in the following manner.
First calculate the flicker contribution Plt,i for a single unit:
Plt,i = c i (ψ k ) ⋅
1
N ⋅ 25
Plt,i:
i:
Ci (ψk):
long term flicker for a single unit
unit which is part of the facility
flicker coefficient (value ψ=30° from the test
N:
the number of identical units
report)
Then calculate the flicker contribution for the entire electricity generation facility
by adding together the individual flicker contributions, Plt,i, based on the
formula:
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Plt = 2
∑ (P )
2
lt,i
i
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Example 1:
Four 15 kW inverters with a flicker coefficient
c, (ψk)=17.84
1
Plt,i = 17.84 ⋅
Plt =
4 ⋅ 25
= 0.18
4 ⋅ 0.18 2 = 0.36
2
2.1.2.3 Electricity generation facilities consisting of different units
If an electricity generation facility consists of different units, flicker contribution,
Plt, is calculated in the following manner.
First calculate the flicker contribution Plt,i for a single unit:
Plt,i = c i (ψ k )⋅
S n ,i
S n ⋅ 25
Plt,i:
i:
Ci (ψk):
long term flicker for a single unit
unit which is part of the facility
flicker coefficient (value ψ=30° from the test
Sn,i:
Sn:
unit i's rated power
the facility's total rated power
report)
Then calculate the flicker contribution, Plt, for the entire electricity generation
facility by adding together the individual flicker contributions, Plt,i, based on the
formula:
Plt = 2
∑ (P )
2
lt,i
i
Plt:
Example 2:
long term flicker
Two 15 kW inverters with a flicker coefficient
C15 (ψk)=17.84 and two 12.5 kW inverters with a flicker
coefficient c12.5 (ψk)=19.74
Plt,15 k = 17.84 ⋅
15
(15 + 15 + 12.5 + 12.5) ⋅ 25
Plt,12 k 5 = 19.74 ⋅
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= 0,19
12.5
(15 + 15 + 12.5 + 12.5) ⋅ 25
= 0.18
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Plt =
2
0.19 2 + 0.19 2 + 0.18 2 + 0.18 2 = 0.37
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Harmonic currents
The electricity generation facility must comply with the limit values for harmonic
currents specified in table 1.
Odd harmonic order h
(not a multiple of 3)
Harmonic
Limit value
[%]
Table 1
Even harmonic order h
(not a multiple of 3)
5
7
11
13
17≤h≤49
2
4
8≤h≤50
3.6
2.5
1.0
0.7
–
-
-
-
limit values for harmonic current Ih/In (%)
Ih
≤ grænseværdi
In
Ih:
I n:
(%)
harmonic current [5,7,11,13]
nominal rated current
If an electricity generation facility consists of several inverters, the contributions
for each inverter must be summed in accordance with the general summation
rule described in IEC 61000-3-6, as specified in the following formula:
Ih = α
∑ Iα
h ,i
i
α:
h:
report
i:
Table 2
exponent of α (table 2)
harmonic [5,7,11,13] (highest value from the test
for the given unit)
number of units [1,2,3,4…]
Harmonic order
α (alpha)
h<5
1
5 ≤ h ≤ 10
1.4
h > 10
2
Value for the exponent α
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Example 3:
Two 15 kW inverters with rated current of 22A and 5th and 7th
harmonics of 0.31% and 0.36% respectively, and two 12.5 kW
inverters with rated current of 19A and 5th and 7th harmonics of
0.29% and 0.33% respectively
First calculate Ih,i for all the harmonic currents for each unit:
I h ,i =
I h ,i / I n ,i [%]
100
⋅ I n ,i
0,31
⋅ 22 A = 0.0682 A
100
I 5,15 k =
I 5,12,5 k = 0,0551A
;
I 7 ,15 k = 0.0792 A
;
I 7 ,12,5 k = 0.0627 A
Then calculate the harmonic currents for the total electricity generation facility
using the general summation rule and exponent α=1.4:
I5 =
1, 4
0.06821, 4 + 0.06821, 4 + 0.05511, 4 + 0.05511, 4 = 0.166 A
I7 =
1, 4
0.07921, 4 + 0.07921, 4 + 0.06271, 4 + 0.06271, 4 = 0.192 A
Finally, calculate the harmonic currents as a % of the rated current:
I n = 22 + 22 + 19 + 19 = 82 A
Ih / In =
Ih
⋅ 100%
In
I5 / In =
0,166
⋅ 100= 0.20%
82
;
I7 / In =
0,192
⋅ 100= 0.23%
82
Interharmonic currents
The electricity generation facility must comply with the limit values for
interharmonic currents specified in table 3.
Interharmonic
Frequency (Hz)
75 Hz
125 Hz
>175 Hz
0.40
0.60
75
f *)
Limit value
[%]
*) But not less than 0.1%
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Table 3
Limit values for emission of interharmonic currents
If the electricity generation facility consists of several inverters, the
contributions must be summed in the same way as for emission of harmonic
currents, but using exponent α=2.
Disturbances from 2-9 kHz
The limit values for currents with frequencies in the 2-9 kHz range must not
exceed 0.2% of the rated current in any of the measured frequency groups.
2.2
Engagement and synchronisation
Within the normal output range, the electricity generation facility must be able
to start-up and produce continually within the design specifications, limited only
by the protection settings specified in section 2.7.
Automatic engagement and synchronisation of the electricity generation facility
must be delayed until at least three minutes after the voltage and frequency are
within the normal output range.
Following automatic re-engagement after a grid fault, the active power output
must not rise by more than 10% per minute.
Engagement with manual synchronisation is not permitted.
As an alternative to the requirements listed above, the requirements in VDEAR-N 4105 may be used.
2.3
Asymmetry
During normal operation or in the case of a fault, the electricity generation
facility must not have asymmetry greater than 16 A between the phases.
If the electricity generation facility consists of three single-phase units, the
necessary communication must be established to ensure that the above limit is
not exceeded.
2.4
Active power regulation
The electricity generation facility must be equipped with an output reduction
function for frequencies greater than f1, as specified in figure 2.
For frequencies greater than f1, a reduction of the current active power must be
effected with a gradient of current power, Pcurrent, which was available at the
time the f1 limit was exceeded. Frequency f1 is 50.2 Hz, and the gradient
(droop) is 40% per Hz.
The active power must continually move up and down the frequency
characteristic for frequencies greater than f1 and up to fmax (the disengagement
frequency) specified in the protection settings in section 2.7.
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Aktiv effekt
Paktuel
Droop 1
fmax
fmin
Pmin
0
47.00
48.00
49.00
50.00
51.00
52.00
Frekvens [Hz]
f1
Figure 2
Power reduction requirements for electricity generation facilities
The requirements in VDE-AR-N 4105 may be used as an alternative to the
requirements listed above. The only difference is a disengagement frequency of
51.5 Hz.
2.5
Reactive power regulation
The electricity generation facility must be able to regulate the reactive power in
the following ways:
•
•
constant power factor, cos φ
variable power factor, cos φ (P)
Any change in the active power must automatically result in the necessary
adjustment to the reactive power for the selected power factor (cos φ) setting.
Except where agreed otherwise with the grid company, the electricity
generation facility must follow the cos φ characteristic specified in figure 3. The
setting must be cos φ=1.
2.5.1
Constant power factor
The electricity generation facility must have a power factor (cos φ) which can
be set to any value within the 0.90 inductive and 0.90 capacitive range when
production is greater than 20% of the rated power, and when the voltage and
frequency lie within the normal output range specified in section 2. The required
adjustment range corresponds to the shaded area in figure 3.
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P/Pn
PF=1
1,0
PF=0,90
+
PF=0,90
0,2
Kapacitiv
-1,0
- 0,8
Figure 3
Induktiv
- 0,6
- 0,4
- 0,2
0,2
0,0
0,4
0,6
0,8
1,0
Q/Pn
Characteristic for constant power factor, cos φ
As an alternative to the requirements listed above, the requirements in VDEAR-N 4105 may be used, which are identical.
2.5.2
Variable power factor
The electricity generation facility must have a characteristic whereby the power
factor is dependent on the produced active power, cos φ (P), as specified in
figure 4.
Depending on the topology (consumption and production) of the public
electricity supply network, the grid company may also require a characteristic
which deviates from figure 4.
P/Pn
1,0
PF=0,90
PF=1
0,5
0,2
Kapacitiv
- 1,0
- 0,8
- 0,6
- 0,4
Induktiv
- 0,2
0,0
0,2
0,4
0,6
0,8
1,0 Q/Pn
Figure 4 Characteristic for variable power factor, cos φ (P)
As an alternative to the requirements listed above, the requirements in VDEAR-N 4105 may be used, which are identical.
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2.6
Tolerance of voltage dips and peaks, FRT
The electricity generation facility must remain connected to the public electricity
supply network during voltage dips and peaks, limited only by the protection
settings specified in section 2.7.
There is no requirement to supply active/reactive power during the period of the
fault.
2.7
Protection towards the grid
The protection equipment must ensure that the electricity generation facility
does not impact negatively on the public electricity supply network or the safety
of people and equipment.
The protection functions for electricity generation facilities connected to the
public electricity supply network must be established at the point of connection
(POC), as specified in table 4.
If the electricity generation facility complies with the requirements at the
electricity generation facility connection point (PGC), it is assumed that the
requirements are also met at the point of connection (POC).
Protection function
Symbol
Setting
a)
Maximum
function time
Minimum
measured
time d)
d)
Overvoltage (stage 2) b)
U>>
1.13 x Un
0.2 s
0.1 s
Overvoltage (stage 1)
U>
1.10 x Un
40 s
39 s
Undervoltage (stage 1)
U>
0.90 x Un
10 s
9s
Over-frequency
f>
52.0 Hz
0.3 s
0.2 s
Under-frequency
f<
47.5 Hz
0.3 s
0.2 s
df/dt
2.5 Hz/s
0.3 s
0.2 s
"ROCOF"
Table 4
facilities
Protection function requirements for electricity generation
a
) All values are RMS values. The electricity generation facility must be
disengaged d if a measured value deviates from its nominal value by more
than the given setting. A measured value must not give rise to
disengagement if the value lies between the nominal value and the setting
value. Voltages must be measured as phase-zero voltages.
b
) Two-stage overvoltage protection is required.
c)
The electricity generation facility must be disengaged via mechanical relay
contacts for which the control signal is galvanically isolated from the poles
(e.g. optically or electrically isolated).
d)
Maximum function time is the sum of the minimum measured time and
time to break. The minimum measured time is the time during which the
trip condition must be constantly fulfilled before the protection function
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may issue a trip signal. It therefore does not refer to a simple delay to the
trip signal.
A joint protection unit is required at electricity generation facility connection
point (PGC) if the electricity generation facility consists of microinverters
(typically less than 500 VA) or if the electricity generation facility is larger than
100 kVA. Where there is any doubt, the grid company will decide what
requirement applies to the electricity generation facility.
Consumption must not be connected after the grid protection unit.
As an alternative, the protection functions and settings in table 2 of VDE-AR-N
4105 may be used. There are alternative setting values for voltage and
frequency, and the active frequency method is used for islanding detection.
2.8
System protection
There are currently no requirements for system protection.
2.9
Communication
There are currently no requirements for communication.
A requirement of being able to communicate with the electricity generation
facility is expected in the future Smart Grid. Implementation is expected to take
place in accordance with IEC 61850.
2.10 Registration and documentation
Pursuant to the common regulations (for the connection of electrical systems
and user devices), registration must take place when an electricity generation
facility is connected to the grid. Registration (incl. master data) must be carried
out by an authorised electrician prior to commencing installation.
Documentation for the electricity generation facility must be as described in this
section. A "Grid connection and usage agreement" (Nettilslutnings- og
netbenyttelsesaftale) must be prepared for the electricity generation facility.
The supplier is responsible, on behalf the plant owner , for preparing the
specified documentation for the electricity generation facility and submitting it
electronically to the grid company.
The required documentation for electricity generation facilities is specified in the
following subsections, categorised by phase current.
2.10.1 Electricity generation facilities producing between 16 A and 75 A per
phase
The supplier must prepare a supplier declaration and a test report, as described
below.
Supplier declaration
The supplier declaration must declare that the requirements in these guidelines
have been met. The required contents of the supplier declaration are specified
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in appendix 1 of the "Guidelines for electricity generation facilities with a rated
current of between 16 A and 75 A per phase, which are connected to the lowvoltage network via inverters" Appendix 1 can be downloaded at
www.energinet.dk.
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Test report
The test report must document that the requirements in these guidelines have
been met. The required contents of the test report are specified in appendix 2
of the "Guidelines for electricity generation facilities with a rated current of
between 16 A and 75 A per phase, which are connected to the low-voltage
network via inverters" Appendix 2 can be downloaded at www.energinet.dk.
As an alternative to the test report in appendix 2, documentation in accordance
with VDE-AR-N 4105 appendix F3, F4, G2 and G3 may be used.
2.10.2 Electricity generation facilities larger than 75 A per phase
The supplier must prepare a supplier declaration and a test report, as described
below.
Supplier declaration
The supplier declaration must declare that the requirements in these guidelines
have been met. The required contents of the supplier declaration are specified
in appendix 3 of the "Guidelines for electricity generation facilities with a rated
current greater than 75 A per phase, which are connected to the low-voltage
network via inverters" Appendix 3 can be downloaded at www.energinet.dk.
Test report
The test report must document that the requirements in these guidelines have
been met. The required contents of the test report are specified in appendix 4
of the "Guidelines for electricity generation facilities with a rated current greater
than 75 A per phase, which are connected to the low-voltage network via
inverters". Appendix 4 can be downloaded at www.energinet.dk.
In addition to the requirements specified above, the following documents must
also be supplied:
•
•
•
Line diagram including point of connection and settlement meter
Documentation for the protection settings for the central grid protection
(if used)
Calculations in relation to voltage quality (such as supplier-specific test
reports)
As an alternative to the test report in appendix 4, documentation in accordance
with VDE-AR-N 4105 appendix F3 and F4 may be used, whereby the test report
must be filled out using values calculated for the total electricity generation
facility.
2.11 Decommissioning, changes or replacement
Where an electricity generation facility is decommissioned, changed or replaced,
the grid company's normal procedures must be followed.
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