IEC TR 63282:2020

IEC TR 63282 ®
Edition 1.0 2020-11
TECHNICAL
REPORT
colour
inside
LVDC systems – Assessment of standard voltages and power quality
requirements
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IEC TR 63282 ®
Edition 1.0 2020-11
TECHNICAL
REPORT
colour
inside
LVDC systems – Assessment of standard voltages and power quality

requirements
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.020 ISBN 978-2-8322-9078-1

– 2 – IEC TR 63282:2020 © IEC 2020
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 8
4 Structure of LVDC systems . 12
4.1 General . 12
4.2 Architecture . 12
4.3 Operation modes . 13
4.3.1 Passive DC systems . 13
4.3.2 Active DC systems . 13
5 LVDC voltage division. 13
5.1 General . 13
5.2 Voltage bands . 14
5.3 Operation ranges with respect to DC voltage and time . 15
5.4 States . 16
6 Power quality phenomena relevant to LVDC networks . 17
6.1 General . 17
6.2 Relationships between voltage band and power quality in LVDC systems . 17
6.3 Supply voltage deviation . 18
6.4 Ripple and high frequency noise . 19
6.5 Voltage swell . 20
6.6 Voltage dip . 21
6.7 Voltage supply interruption. 22
6.8 Rapid voltage change (RVC) . 22
6.9 Voltage surges . 23
6.10 Voltage unbalance . 24
7 Recommendations . 25
7.1 General . 25
7.2 Recommended voltages . 25
7.3 EMC and compatibility levels . 26
7.4 Power quality recommendations . 28
7.5 Measurement methods . 29
7.5.1 General . 29
7.5.2 DC system RMS value integration time . 29
7.5.3 DC power quality measurement methods . 29
Annex A (informative) PQ waveforms collected from a certain LVDC project . 30
Annex B (informative) Load distance in DC distribution systems . 32
Annex C (informative) Electric power and power quality computation in DC systems . 33
C.1 DC RMS value of voltage or current . 33
C.2 General electric power system: decomposition of a general electric load . 33
C.3 Computation of electric powers and PQ indices. 34
C.4 Representation of electric powers in AC system . 37
C.5 Representation of electric powers in DC system . 37
C.6 Power quality indices in DC system. 38
C.7 Illustration example of deformation power in DC system . 39

C.8 Main conclusions on electric value computation in DC systems . 40
C.9 Need of characteristics of DC voltage . 41
Annex D (informative) District LVDC system demonstration project in Tongli, China . 42
D.1 Project overview . 42
D.2 Voltage level selection principle . 42
D.3 System operation . 43
Annex E (informative) An office building with general building utilities and office work
places . 44
Annex F (informative) An example of configurations for active DC systems . 50
F.1 General . 50
F.2 Structure . 50
F.3 State of grid (SOG) . 50
Annex G (informative) Preferred voltage in different countries . 55
G.1 Preferred voltage in China . 55
G.2 Preferred voltage in the Netherlands . 57
G.3 Preferred voltage in Germany . 58
Annex H (informative) Voltage with respect to earth . 59
Annex I (informative) CIGRE approaches for DC systems . 62
Bibliography . 63

Figure 1 – Unipolar, balanced and bipolar DC systems . 12
Figure 2 – Voltage bands in DC systems . 14
Figure 3 – DC Voltage areas for safe interoperability . 15
Figure 4 – Relationships between voltage band and power quality in LVDC systems . 18
Figure 5 – Voltage swell example. 20
Figure 6 – Voltage dip example . 21
Figure 7 – RVC event: example of a change in average voltage that results in an RVC
event . 23
Figure 8 – Example of voltage surge . 24
Figure 9 – A schematic of a bipolar system (the CIGRE B4 DC test system) . 25
Figure 10 – Relation between disturbance levels (schematic significance only) . 26
Figure 11 – LVAC voltage compatibility and immunity levels . 27
Figure A.1 – Voltage deviation caused by load switching . 30
Figure A.2 – Voltage ripple in steady state . 30
Figure A.3 – Voltage dip caused by the start-up of motor load . 31
Figure C.1 – Equivalent model of a general electric load . 34
Figure C.2 – Representation of electric powers in AC system . 37
Figure C.3 – Representation of electric powers in DC system . 37
Figure C.4 – Ripples . 38
Figure C.5 – DC powers . 40
Figure C.6 – Compatibility level measured in differential mode values . 41
Figure D.1 – Architecture of the district LVDC system in Tongli . 42
Figure E.1 – Office building with general building utilities and office work places . 44
Figure E.2 – Overview of DC-zones for DC system . 46
Figure F.1 – Active DC distribution system . 50

– 4 – IEC TR 63282:2020 © IEC 2020
Figure F.2 – DC distribution system with one load and one source . 52
Figure F.3 – DC distribution system with more than one load and a source and
increasing source power . 53
Figure F.4 – Distribution system with more than one load and a source and DUMP
LOAD active . 53
Figure F.5 – Distribution system with more than one load and source in overloaded
mode . 54
Figure H.1 – DC voltage definitions . 59
Figure H.2 – DC voltage bands relative to earth . 60
Figure H.3 – DC voltages to earth – examples . 61
Figure I.1 – Temporary DC pole to ground voltage profiles in DC systems . 62

Table 1 – Difference between unipolar and bipolar systems . 13
Table 2 – Voltage between lines (unipolar systems) or line and midpoint (bipolar
systems) . 26
Table 3 – Voltage between lines (bipolar systems) . 26
Table 4 – Immunity: DC input and output power ports, residential, commercial and light

industrial environment . 28
Table 5 – Immunity: DC input and output power ports – Industrial environment . 28
Table B.1 – 1,5 (±0,75) kV typical load distance of overhead DC lines . 32
Table B.2 – 750 (±375) V, 220 (±110) V typical section load distance of overhead
DC lines . 32
Table C.1 – Different powers . 40
Table E.1 – Aspects regarding the DC zone classification in DC installation . 49
Table F.1 – Examples in case of 350/700 V DC systems . 51
Table F.2 – Allowed voltages cable drop . 52
Table G.1 – Nominal voltage in LVDC distribution system . 55
Table G.2 – Nominal voltage in ELVDC equipment . 56
Table G.3 – Comparison between DC and AC system voltages . 57
Table G.4 – Overview of the recommended voltage classes (VC) and the
corresponding U and U values . 58
2 3
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
LVDC SYSTEMS – ASSESSMENT OF STANDARD
VOLTAGES AND POWER QUALITY REQUIREMENTS

FOREWORD
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The main task of IEC technical committees is to prepare International Standards. However, a
technical committee may propose the publication of a Technical Report when it has collected
data of a different kind from that which is normally published as an International Standard, for
example "state of the art".
IEC TR 63282, which is a Technical Report, has been prepared by IEC technical committee 8:
System aspects of electrical energy supply.
The text of this Technical Report is based on the following documents:
Draft TR Report on voting
8/1549/DTR 8/1556/RVDTR
Full information on the voting for the approval of this Technical Report can be found in the
report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

– 6 – IEC TR 63282:2020 © IEC 2020
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
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of its contents. Users should therefore print this document using a colour printer.

INTRODUCTION
LVDC (Low voltage direct current) distribution systems have recently been recognized by a
number of stakeholders as an alternative approach to provide efficient power supply to the
consumers. LVDC covers a wide range of power applications from USB-C up to megawatts for
aluminium melting. LVDC is now seen not only as a solution for electricity access in developing
economies but also as a solution for greener and more sustainable energy in developed
economies.
In industrial applications, LVDC is utilized where processing of resources results in the
production, distribution and storage of physical goods, especially in a factory or special area of
a factory.
The standardization of DC voltages is a key issue, and urgent work is needed. Existing LVAC
systems have different standard voltages, depending on the geography and application. LVDC
distribution voltages should be optimized to provide a good context for industries that import
and export equipment but also for general travellers. Appropriate international LVDC voltage
ranges will provide a basis for design and testing of electrical equipment and systems and ease
of transition for equipment from AC to DC supply.
LVDC voltages should meet the range of use cases where LVDC systems can make a difference.
The list of standard voltages should be as short as possible and allow for cost-effective and
safe operation.
The power quality phenomena for the distribution of DC power are not identical to AC
phenomena while there are some common issues. Power quality considerations are well studied
and standardized on AC power systems, but many power quality phenomena and EMC have
not yet been fully evaluated for DC distribution systems.
Power electronic converters/inverters add further demands. Power quality phenomena in LVDC
distributed systems can be related to the topology of the entire system, and the operating
condition of sources and loads. At the same time, the DC output performance of a single
converter and the coordination among several converters can also result in different power
quality issues and grid stability.
Requirements for power quality and EMC in LVDC distribution should be established in order
to provide a solid basis for the planning and operation of LVDC distribution systems. In addition,
the design and configuration of the protection system is to be addressed with the objective to
enhance the availability of the source, the reliability, and the lifetime of the system.
Generally, the standardization of voltage level and PQ phenomena of LVDC distribution should
greatly stimulate the wide adoption of LVDC.
Besides the main contents concerning voltage level and power quality, the following topics are
also presented:
Clause 4 discusses architectures and topologies for LVDC networks.
Clause 7 recommends permissible limits for voltage bands and PQ phenomena.

– 8 – IEC TR 63282:2020 © IEC 2020
LVDC SYSTEMS – ASSESSMENT OF STANDARD
VOLTAGES AND POWER QUALITY REQUIREMENTS

1 Scope
The purpose of this document is to collect information and report experience in order to make
recommendations for the standardization of voltage levels and related aspects (power quality,
EMC, measurement …) for LVDC systems (systems with voltage level lower than 1 500 V d.c.).
Rationale for the proposed voltage values are given. Variation of parameters for the voltage
(power quality) and recommendation for their boundaries are defined. Nevertheless, some of
the technical items are not exhaustively explained in this document and some gaps are
identified for future work.
Attention is paid to the definition of DC voltage.
Systems in which a unipolar voltage is interrupted periodically for certain purposes, e.g. pulse
voltage, are not considered.
Traction systems are excluded from this document.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
nominal system voltage
suitable approximate value of voltage used to designate or identify a system
[SOURCE: IEC 60050-601:1985, 601-01-21]
3.2
DC supply voltage
line-to-line or line-to-midpoint voltage at the supply terminals
3.3
bipolar DC system
DC system comprising positive, midpoint and negative lines
3.4
unipolar DC system
DC system comprising of two lines

3.5
DC system nominal voltage
U
n
suitable approximate value of voltage used to designate or identify a DC system
Note 1 to entry: A bipolar DC system is preferred to use a dual notation, for example, "±U "or "U / U ".
L-M L-M L-L
3.6
DC voltage deviation
voltage deviation due to the slow change in power system operation state
Note 1 to entry: Voltage deviation is the difference between actual voltage and nominal system voltage when the
change rate of the average DC voltage is in the appropriate speed in order to limit the deviation in an acceptable
range.
3.7
voltage unbalance
condition in a bipolar system in which the line to mid-point voltages are not equal
3.8
ripple
set of unwanted periodic deviations with respect to the average value of the measured or
supplied quantity, occurring at frequencies which can be related to that of the mains supply, or
of some other definite source, such as a chopper
Note 1 to entry: Ripple is determined under specified conditions and is a part of PARD (Periodic and/or random
deviation). It may be assessed by instantaneous value or RMS value.
Note 2 to entry: Sources of ripple may include, but are not limited to, voltage regulation instability of the DC power
source, commutation/rectification within the DC power source, and load variations within utilization equipment.
Note 3 to entry: Ripple is determined as well in percentage to DC component and in RMS value computed in
frequency range < 150 kHz (in line with SC77A and CISPR for conducted disturbances).
[SOURCE: IEC 60050-312: 2001, 312-07-02, modified – A sentence has been added to Note 1
to entry; Notes 2 and 3 to entry have been added]
3.9
over-voltage
voltage, the value of which exceeds a specified limiting value
[SOURCE: IEC 60050-151:2001,151-15-27]
3.10
under-voltage
voltage, the value of which is lower than a specified limiting value
[SOURCE: IEC 60050-151:2001,151-15-29]
3.11
voltage swell
sudden increase of the voltage at a point in the electrical supply system followed by voltage
recovery after a short period of time
Note 1 to entry: Application: for the purpose of this document, the swell start threshold is equal to the 110 % of the
reference voltage (see CLC/TR 50422, Clause 3, for more information).
Note 2 to entry: For the purpose of this document, a voltage swell is a two dimensional electromagnetic disturbance,
the level of which is determined by both voltage and time (duration).

– 10 – IEC TR 63282:2020 © IEC 2020
3.12
voltage dip
sudden voltage reduction at a point in the electrical supply system, followed by voltage recovery
after a short period of time
Note 1 to entry: The residual voltage may be expressed as a value in volts, or as a percentage or per unit value
relative to the reference voltage.
[SOURCE: IEC 60050-614:2016,614-01-08, modified – Reference to sinusoidal voltage has
been removed and time interval has been changed to period of time]
3.13
voltage surge
transient voltage wave propagating along a line or a circuit and characterized by a rapid
increase followed by a slower decrease of the voltage
[SOURCE: IEC 60050-161:1990, 161-08-11]
3.14
voltage supply interruption
disappearance of the supply voltage for a time interval whose duration is between two specified
limits
3.15
rapid voltage change
RVC
quick transition in voltage occurring between two steady-state conditions, and during which the
voltage does not exceed the dip/swell thresholds
3.16
active distribution system
ADS
distribution networks that have systems in place to control a combination of distributed energy
resources (i.e., distributed generation, controllable loads or energy storage)
Note 1 to entry: Protection can also be included in ADS.
3.17
passive distribution system
PDS
distribution systems in which the energy balance is controlled by the voltage source (e.g.,
outside grid or battery)
3.18
droop in a DC system
ratio of per-unit change in voltage to the corresponding per-unit change in power of the demand
3.19
distribution network operator
DNO
party operating a distribution network
3.20
distribution system operator
DSO
party extending the function of a DNO to incorporate active management of some power
resources
3.21
positive voltage
U+
voltage between the positive line and the midpoint
Note 1 to entry: Only defined for bipolar DC systems.
3.22
negative voltage
U-
voltage between the midpoint and the negative line
Note 1 to entry: Only defined for bipolar DC systems.
3.23
balanced voltage
U
b
average of the positive and the negative voltage
Note 1 to entry: U = (U +U )/2.
b p n
Note 2 to entry: Only defined for bipolar DC systems.
3.24
unbalanced voltage
U
u
average difference of the positive and the negative voltage
Note 1 to entry: U = (U -U )/2.
u p n
Note 2 to entry: Only defined for bipolar DC systems.
3.25
midpoint
common point between two symmetrical circuit elements the opposite ends of which are
electrically connected to different line conductors of the same circuit
Note 1 to entry: Only defined for bipolar DC systems.
[SOURCE: IEC 60050-195:1998, 195-02-04, modified – The note to entry has been added]
3.26
under-voltage ride through
capability of equipment to stay connected and continue functioning during loss or drop of supply
voltage
3.27
DC voltage
voltage equal to its average value during a defined time interval
3.28
over-voltage ride through
capability of equipment to stay connected and continue functioning during voltage swells

– 12 – IEC TR 63282:2020 © IEC 2020
4 Structure of LVDC systems
4.1 General
A LVDC system is a combination of different electronic devices, whose operation is strongly
based on different control strategies. Thus, as far as the recommended voltages and power
qualities of certain LVDC systems are concerned, different analysis dimensions and elements
should be taken into consideration, including different architectures, operation modes, etc.
4.2 Architecture
Several use cases concerning existing technologies and projects have been introduced to
support the analysis and classification of LVDC systems, including but not limited to:
• LVDC system in buildings,
• LVDC systems between buildings.
Details and examples can be found in Annex D, Annex E and Annex F. Formal use cases are
also under work in the frame of the SyC LVDC WG2.
Unipolar or bipolar DC systems can be designed with two or three output lines, respectively.
Taking the earthing into account, it can be divided into TN-S system and IT system as Figure 1
shows.
In the TN-S system, the midpoint connection (M) is directly connected to the protective earth
(PE) while in the IT system, the midpoint connection is not directly connected to the protective
earth (PE) and there are intentional (by design) or unintentional impedances which are between
conductors and earth.
A list of differences between unipolar and bipolar systems can be seen in Table 1.

NOTE All IT systems will have impedances between conductors and earth. These impedances can be parasitic and
poorly defined, or can be well designed.
Figure 1 – Unipolar, balanced and bipolar DC systems

Table 1 – Difference between unipolar and bipolar systems
Item Unipolar Bipolar
Cable utilization* U*I / 2 2 U* I / 3
(U * I / 3 with PE) (U* I / 2 with PE)
Available operating voltage(s) U+ nominal U+ nominal, U- nominal, 2 U nominal
Maximum fault voltage U nominal 2 U nominal
Protection and Control Complexity Low Higher
High in case of multiple sources
Connectors 2-pin 3-pin
(3-pin with PE) (4-pin with PE)
Switching and breakers Single-pole Double-pole
RCD 2-pole 3-pole
* Cable utilisation = (Max voltage to ground) × (Max conductor current) / (number of conductors)

NOTE Both positive earthing and negative earthing are possible. However, the positive earthed system will
introduce negative leakage currents, and in the case of very high voltages, the metal structure of DC systems
including earthing conductors might become more brittle. On the other hand, the negative earthed system will
introduce positive leakage currents that can result in corrosion issues.
4.3 Operation modes
4.3.1 Passive DC systems
In passive DC systems, most of the integrated sources, which need control objectives as an
input from outside, can be either voltage source or current source. The control strategy of
passive sources is frequently based on master-slave control and the energy balance margin of
the system mostly relies on the capability of the voltage source. Normally, the voltage source
is designed to support the power supply of the system. The system voltage can only vary within
a narrow range under normal operating conditions.
4.3.2 Active DC systems
In active DC systems, nearly all the sources and loads are connected to the DC bus by self-
controllable electronic devices. The control strategies of active sources are frequently based
on drooped control and the energy balance of the system is realized automatically by tracing
the U-I curves configured in the devices. In this case, the voltage can fluctuate in a wider range
than that in passive DC systems, which is regarded as voltage band. The normal operation
voltage band can be adjusted by different configurations of control parameters in devices. A
wider voltage band brings higher technical requirements to the system and equipment.
5 LVDC voltage division
5.1 General
In active DC systems, the voltages are divided into different levels for temporary and continuous
operation.
Between zero and maximum, the voltages are divided into 6 different stages: U . U and in
1 6
the centre U for continuous and steady state operation.
n
To cover steady state and transient voltage levels, a matrix with all the voltages, voltage bands,
operating states and areas is made. The matrix is presented in Figure 2.

– 14 – IEC TR 63282:2020 © IEC 2020
5.2 Voltage bands
The range between two voltages is called a voltage band. Voltage bands are useful for
describing voltage limits without going into the level of detail of time limits. Ui is corresponding
to the upper limit of band Bi (i=1,2,3,4,5,6).

Figure 2 – Voltage bands in DC systems
B1: Blackout band
In this voltage band, only short dips to zero (State S1, as shown in Figure 3) are allowed. Longer
events will cause a shutdown of the whole system in S2 to S4.
B2: Emergency band
This is the band in which the voltage may drop below the normal operation band due to high
overload.
NOTE Emergency devices and infrastructure relevant devices can operate in this voltage band.
B3: Nominal band
This is the normal operation band (between U2 and U3; see Figure 2).
B4: Switching, commutation and protection devices operation band
In this band, the voltage may overshoot or rise due to a sudden change of current. Surge
protection devices do not operate in this band.

B5: Overvoltage protection devices operation band
This band is dedicated to the operation of the overvoltage protection devices. Above B5,
semiconductors can be destroyed by an overvoltage lasting for a very short time.
B6: Overvoltage trip band
In this band, voltages are not tolerated by the equipment and are likely to cause breakdown.
B7: Prohibited band
In this band, permanent equipment damage is very likely.
5.3 Operation ranges with respect to DC voltage and time
To achieve continuity of operation, 4 states are defined, of which 3 states (S1 to S3) are
transient states and 1 state (S4) is the steady state. These states may occur routinely or in
exceptional situations. In each state, the allowed overvoltage and dynamics are different.
Voltage bands are divided in these 4 states. See Figure 3.

Figure 3 – DC Voltage areas for safe interoperability
To account for time-limited capabilities of the system components, the following time-limited
states are defined in the graphic.
NOTE In Figure 3, the widths of the states only indicate that:
S1 < S2 < S3 < Continuous operation (S4)
States S1 through S3 are transient states and can have different durations.
S1: Transient range
The transient state is limited to a very short time. After being in the transient state, the system
will return to a steady state.

– 16 – IEC TR 63282:2020 © IEC 2020
S2: Fault range
A system state which involves, or is the result of, failure of a system circuit or item of system
plant or equipment or apparatus and which normally requires the immediate disconnection of
the faulty circuit, plant or equipment or apparatus from the power system by the tripping of the
appropriate circuit-breakers. [IEC 60050-448:1995, 448-13-02, modified]
S3: Voltage control range
In this state, action is required by the system to address system balance issues.
S4: Steady range
The system may remain in this state indefinitely.
5.4 States
The area between these voltages and states is defined as follows:
A1: Blackout state
Supply in this area is insufficient for operation to be maintained.
A2: Emergency state
The voltage in this area indicates that the supply is under stress. Loads should still be able to
operate correctly, but perhaps not meet all performance requirements. Action may be taken to
reduce the stress on the system, for example through load-shedding or the introduction of
additional power sources.
A3: Normal operating band/nominal band (U to U )
2 3
For the normal operation of a DC system, the voltage difference between the power terminals
should be maintained between U and U under all conditions. All equipment performance
2 3
requirements should be met within this band.
Operation between these limits includes all normal operating states of the system, and normal
droop control ranges. The voltage delivered to a load should be within this band allowing for IR
voltage drop in cabling.
The nominal voltage (U : U nominal)
n
As stated in IEC 60050-161:1985, 601-01-21, nominal voltage is a suitable approximate value
of voltage used to designate or identify a system. The nominal voltage U is within the nominal
n
band but is not always half-way between U and U ; however, we may say that in all cases,
2 3
U ≤ U ≤ U
2 n 3
A4: Abnormal state
In exceptional circumstances, voltage may stray into this area for an extended period.
Installation and equipment shall be designed to withstand this, and continue to operate normally,
but possibly with reduced performance. Overvoltage protection devices shall not operate.
Action may be taken to modify power input to rebalance the system.

A5: Overvoltage state without clamping
Area in which the voltage may overshoot due to operation of switching or protection devices.
Overvoltage clamping shall not clamp these voltage overshoots.
A6: Overvoltage with clamping
In this area, overvoltage protection devices shall operate to clamp overvoltage.
A7: Prohibited state
In this area, permanent equipment damage is very likely. If technically possible, all power
sources shall be switched off.
6 Power quality phenomena relevant to LVDC networks
6.1 General
Voltage quality is important for ensuring that systems function as intended. Voltage quality shall
be specified in order to provide a system designer with a reference to design the supply, load
and distribution system. Voltage quality requirements may be different for different use cases
and respective system layouts. Designers’ responsibility is to ensure that regardless of the
system layout and network topology, the voltage variation, transients and other voltage
disturbances do not exceed the application and use-case specific limits of the operating ranges
nor the values tolerated by the devices used in the installations.
Ideally, a perfect voltage source is considered, with a stable voltage within a normal voltage
band. Voltage quality is defined in terms of limits to deviations outside this band or disturbances.
These deviations outside this band or disturbances may be continuous and discontinuous.
Use case, application and electromagnetic environment specific compatibility levels shall be
defined for temporary voltage variation, voltage dips and swells, flicker, and the maximum
duration and magnitudes of DC voltage fluctuations.
The characteristics of good power quality are:
• Voltage is maintained within agreed limits in normal operation (Subclause 6.2 to Subclause
6.8);
• Ripple and high frequency voltages/current disturbances are below permissible limits (6.4).
6.2 Relationships between voltage band and power quality in LVDC systems
For the normal operation of a DC system, the voltage at a certain node should be maintained
at the target operating value for each operating point within limited variations under all
conditions. A constant DC voltage indicates a balance of the power injected into or exported
from the DC system.
DC system control sha
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