IEC/TR 61000-2-1
(Main)Amendment to CISPR 11 and CISPR 15: ISM lighting apparatus
Amendment to CISPR 11 and CISPR 15: ISM lighting apparatus
Has the status of a technical report, and gives information on the various types of disturbances that can be expected on public power supply systems. The following disturbance phenomena are considered: - harmonics - inter-harmonics - voltage fluctuations - voltage dips and short supply interruptions - voltage unbalance - mains signalling - power frequency variation - d.c. components.
Amendement aux CISPR 11 et CISPR 15: Appareils d'éclairage ISM
Renseigne sur les divers types de perturbations qui peuvent intervenir sur les réseaux publics d'alimentation électrique. Traite ainsi les phénomènes perturbateurs suivants: - harmoniques - interharmoniques - fluctuations de tension - creux de tension et coupures brèves - déséquilibre de tension - transmission de signaux sur le réseau - variation de la fréquence d'alimentation - composantes continues. Cette publication a le statut d'un rapport.
Electromagnetic compatibility (EMC) - Part 2: Environment - Section 1: Description of the environment; electromagnetic environment for low-frequency conducted disturbances and signalling in public power supply systems
General Information
Standards Content (Sample)
SLOVENSKI SIST-TP IEC/TR3 61000-2-
1:2004
STANDARD
april 2004
Electromagnetic compatibility (EMC) - Part 2: Environment - Section 1: Description
of the environment; electromagnetic environment for low-frequency conducted
disturbances and signalling in public power supply systems
ICS 33.100.01 Referenčna številka
SIST-TP IEC/TR3 61000-2-1:2004(en)
© Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno
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RAPPORT CEI
TECHNIQUE IEC
1000-2-1
TECHNICAL
Première édition
REPORT
First edition
1990-05
Compatibilité électromagnétique (CEM)
Partie 2:
Environnement
Section 1: Description de l'environnement —
Environnement électromagnétique pour les
perturbations conduites basse fréquence et
la transmission de signaux sur les réseaux
publics d'alimentation
Electromagnetic compatibility (EMC)
Part 2:
Environment
Section 1: Description of the environment —
Electromagnetic environment for low-frequency
conducted disturbances and signalling
in public power supply systems
© CEI 1990 Droits de reproduction réservés — Copyright - all rights reserved
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rt cation may be reproduced or utilized In any
utilisée sous quelque forme que ce soit et par aucun procédé, form or by any electronic or mechanical, Including
means,
électronique ou mécanique,
y compris la photocopie et les photocopying and microfilm, without permission In writing
microfilms, sans l'accord écrit de
l'éditeur. from the publisher.
Bureau Central de la Commission Electrotechnique Internation ale 3, rue de Varembé Genève, Suisse
CODE PRIX
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PRICE CODE
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• Pour prix, voir catalogue en vigueur
•
For price, see current catalogue
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1000-2-1 ©IEC
CONTENTS
Page
FOREWORD 5
INTRODUCTION 7
Clause
1 Scope 9
2 Normative references 9
11
3 Definitions
13
4 Purpose of specifying electromagnetic compatibility levels
15
Harmonics
5
21
6 Interharmonics
27
7 Voltage fluctuations
8 rt supply interruptions 31
Voltage dips and sho
35
9 Voltage unbalance
10 Mains signalling 37
11 Power frequency variation 41
43
12 D.C. components (Under consideration)
44
Figures
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1000-2-1 © IEC
INTERNATIONAL ELECTROTECHNICAL COMMISSION
ELECTROMAGNETIC COMPATIBILITY (EMC)
Part 2: Environment
Section 1: Description of the environment -
Electromagnetic environment for low-frequency
conducted disturbances and signalling in public
power supply systems
FOREWORD
The formal decisions or agreements of the IEC on technical matters, prepared by Technical Committees on
1)
which all the National Committees having a special interest therein are represented, express, as nearly as
possible, an international consensus of opinion on the subjects dealt with.
They have the form of recommendations for international use and they are accepted by the National
2)
Committees in that sense.
3) In order to promote international unification, the IEC expresses the wish that all National Committees
should adopt the text of the IEC recommendation for their national rules in so far as national conditions will
permit. Any divergence between the IEC recommendation and the corresponding national rules should, as
far as possible, be clearly indicated in the latter.
This section of IEC 1000-2, which has the status of a technical report, has been prepared
by IEC Technical Committee No. 77: Electromagnetic compatibility between electrical
equipment including networks.
The text of this section is based on the following documents:
Two Months' Procedure Report on Voting
Six Months' Rule Report on Voting
77(CO)34
77(CO)26 77(CO)30 77(00)32
Full information on the voting for the approval of this section can be found in the Voting
Reports indicated in the above table.
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1000-2-1 © IEC - 7 -
INTRODUCTION
IEC 1000 is published in separate pa rts according to the following structure:
Part 1: General
General considerations (introduction, fundamental principles)
Definitions, terminology
Part 2: Environment
Description of the environment
Classification of the environment
Compatibility levels
Part 3: Limits
Emission limits
Immunity limits (in so far as they do not fall under the responsibility of the product
committees)
Part 4: Testing and measurement techniques
Measurement techniques
Testing techniques
Part
5: Installation and mitigation guidelines
Installation guidelines
Mitigation methods and devices
Part 9: Miscellaneous
Each part
is further subdivided into sections which can be published either as International
Standards or Technical reports.
These standards and reports will be published in chronological order and numbered
accordingly.
This section is a Technical Report serving as a reference document for those associated
parts of IEC 1000 that give values of compatibility level, for example IEC 1000-2-2.
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1000-2-1 © IEC -9 -
ELECTROMAGNETIC COMPATIBILITY (EMC)
Part 2: Environment
Section 1: Description Of the environment -
Electromagnetic environment for low-frequency
conducted disturbances and signalling in public
power supply systems
1 Scope
This section of IEC 1000-2 is concerned with conducted disturbances in the frequency
range up to 10 kHz with an extension for mains signalling systems. Separate sections give
numerical compatibility levels for different system voltage levels.
This section does not deal with the application of compatibility levels to assess, for
example, the permissible interference emission from specific items of equipment or
installations, because other system parameters, such as its impedance as a function of
frequency, have also to be considered. Furthermore, it does not prejudge the specification
of immunity levels by the product committees but merely provides a guide.
The disturbance phenomena considered are:
harmonics;
inter-harmonics;
voltage fluctuations;
voltage dips and short supply interruptions;
voltage unbalance;
mains signalling;
power frequency variation;
d.c. components.
The object of this section is to give information on the various types of disturbances that
can be expected on public power supply systems. It is a reference document for those
associated parts that give values of compatibility level.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute
provisions of this section of IEC 1000-2. At the time of publication, the editions indicated
were valid. All standards are subject to revision, and parties to agreements based on this
section of IEC 1000-2 are encouraged to investigate the possibility of applying the most
recent editions of the standards indicated below. Members of IEC and ISO maintain
registers of currently valid international standards.
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1000-2-1 ©IEC - 11 -
IEC 38: 1983,
IEC standard voltages.
IEC 50(161): 1990, International Electrotechnical Vocabulary (IEV), Chapter 161:
Electromagnetic Compatibility. (Under consideration.)
IEC 146: 1985, Semiconductor convertors. Second impression 1985 incorporating:
Supplement 146A (1974) and Amendment No. 1 (1975).
IEC 555-3: 1982, Disturbances in supply systems caused by household appliances and
similar electrical equipment. Part 3: Voltage fluctuations.
IEC 868: 1986, Flickermeter. Functional and design specifications.
IEC 1000-2-2: 1990, Electromagnetic compatibility (EMC). Pa rt 2: Environment. Section 2:
Compatibility levels for low-frequency conducted disturbances and signalling in public
low-voltage power supply systems.
3 Definitions
The definitions are taken from IEC 50(161): International Electrotechnical Vocabulary
(IEV), Chapter 161: Electromagnetic compatibility.
The relevant basic definitions are:
3.1 Electromagnetic compatibility; EMC (abbreviation) (IEV 161-01-07)
The ability of an equipment or system to function satisfactorily in its electromagnetic
environment without introducing intolerable electromagnetic disturbances to anything in
that environment.
3.2 (Electromagnetic) compatibility level (IEV 161-03-10)
The specified maximum electromagnetic disturbance level expected to be impressed on a
device, equipment or system operated in particular conditions.
NOTE - In practice the electromagnetic compatibility level is not an absolute maximum level, but may be
exceeded with a small probability.
3.3 Electromagnetic disturbance (IEV 161-01-05)
Any electromagnetic phenomenon which may degrade the pe rformance of a device,
equipment or system, or adversely affect living or inert matter.
NOTE - An electromagnetic disturbance may be an electromagnetic noise, an unwanted signal or a
change in the propagation medium itself.
3.4 Disturbance level (not defined in IEV 161)
The value of a given electromagnetic disturbance, measured in a specified way.
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1000-2-1 © IEC
3.5 Limit of disturbance (IEV 161-03-08)
The maximum permissible electromagnetic disturbance level, as measured in a specified
way.
3.6 Immunity level (IEV 161-03-14)
The maximum level of a given electromagnetic disturbance incident on a particular device,
equipment or system for which it remains capable of operating at a required degree of
performance.
3.7 (Electromagnetic) susceptibility (IEV 161-01-21)
The inability of a device, equipment or system to perform without degradation in the
presence of an electromagnetic disturbance.
NOTE - Susceptibility is a lack of immunity.
4 Purpose of specifying electromagnetic compatibility levels
NOTE - An interpretation of the basic definitions for practical application in IEC is in preparation. The
main results are considered in this clause.
From the definition of electromagnetic compatibility level it can be seen that it is a
reference value by means of which the disturbance level on the system and the immunity
level for various equipment types can be coordinated.
For practical purposes the limit of disturbance" is the maximum disturbance level
appearing with a certain probability in the electromagnetic environment of a device,
equipment or system. This is the reference value to which the other levels have to be
related, in order to avoid causing interference.
In some cases, this maximum disturbance level is the result of the superposition of several
sources (e.g. harmonics), in other cases it is produced by a single source (e.g.
non-repetitive voltage dip).
It must be emphasized that in general, the disturbance level is not a single value, but
varies with position and time. In practice, the statistical distribution of the disturbance
must be considered.
The maximum disturbance level may be derived from actual network measurements or,
possibly, theoretical study.
Because of this variability of the disturbance level, it is often very difficult or even
impossible to determine the actual highest level of disturbance which may appear very
infrequently. It is also generally not economical to define the compatibility level in terms of
this highest value to which most devices would not be exposed most of the time.
It therefore seems appropriate to define the compatibility level not as the "maximum value"
of a disturbance but as the level of the disturbance that would be exceeded in only a small
or very small number of cases - the aim being for the compatibility level to cover at least
95 % or so of situations.
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1000-2-1 ©IEC - 15 -
The immunity level of equipment should be equal to the compatibility level or higher.
The immunity level has to be checked by an appropriate test. Determining its value and
the test procedure is the responsibility of a relevant Technical Committee (or is subject to
agreement between the parties involved).
The susceptibility level of equipment is the level of disturbance which would disturb the
function of the equipment. It should be equal to, or higher than, the immunity level fixed
for the tests.
The susceptibility level should be fixed by the manufacturer taking into account anticipated
service conditions and the specified immunity limit. The susceptibility level may require
consideration in statistical terms.
The compatibility level is intended to serve as a reference value for trouble-free operation,
in particular for public power supply systems to which items of equipment are connected
by independent consumers not normally in contact with each other.
The relation between the different levels of disturbance taking into account the statistical
features is illustrated by figure 1.
In dedicated or independent systems, servicing for example only one customer's
equipment of a particular kind, other compatibility levels may be agreed.
5 Harmonics
5.1
Description of the phenomenon
Harmonics are sinusoidal voltages or currents having frequencies that are whole multiples
of the frequency at which the supply system is designed to operate (e.g. 50 Hz or 60 Hz).
Harmonic disturbances are generally caused by equipment with a non-linear
voltage/current characteristic. Such equipment may be regarded as current sources of
harmonics.
The harmonic current from the different sources produces harmonic voltage drops across
the impedance of the network. This phenomenon is represented in figure 2 in a simplified
way. In reality, the different harmonic currents add vectorially.
As a result of the connection of reactive loads (e.g. power factor correction capacitors)
and the effect of cable capacitance, shunt and series resonance may occur in the network
and cause a voltage magnification even at a point remote from the distorting load.
5.2 Sources of harmonics
Harmonic currents are generated to a small extent and at low distortion levels by
generation, transmission and distribution equipment and to a larger extent, at relatively
large distortion levels, by industrial and domestic loads. Normally there are only a few
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1000-2-1 © IEC - 17 -
sources generating significant harmonic currents in a network; the individual harmonic
power rate of the majority of the other devices is low.
The following sources generate significant harmonic currents in a network:
- equipment with phase-control and high power;
- uncontrolled rectifiers, especially with capacitive smoothing (e.g. used in
televisions, frequency converters, and self-ballasted lamps), because these harmonics
are in phase to each other and there is no compensation in the network.
Sources may produce harmonics at a constant or varying level, depending on the method
of operation.
5.2.1 Generation, transmission and distribution equipment
This category covers equipment used by utilities to supply electricity, especially
generators, transformers and more recently, though to a limited extent, equipment like
static compensators and frequency converters.
Since it is impossible for the designer of a generator to obtain a pure sine wave, rotating
machines generally represent a source of harmonics. However the magnitude of these
harmonics is normally negligible as proper selection of slots per pole, coil pitches etc.
ensures that almost sinusoidal generated waveshape can be obtained. However,
unbalanced operation will result in the generation of third and higher harmonics.
Distortion from transformers is caused by the saturation of iron in the magnetic circuit of
the transformer coil.
5.2.2 Industrial loads
Industrial loads which may be a source of significant levels of harmonic distortion include
power converters (rectifiers), induction furnaces, arc furnaces etc.
Electronic power equipment may have a significant influence on the level of disturbance of
networks. The use of this type of equipment is increasing in terms of numbers and the unit
ratings involved.
According to theory, the characteristic harmonic current of power converters will be of the
order:
n = pxm±1
where
n is the harmonic order;
p
is the pulse number of the converter;
m
is any integer (1, 2, 3 .).
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1000-2-1 © IEC
In practice, however, non-characteristic harmonics are also generated due to inaccuracies
in the values of control angles, unbalance in supply voltages, and any causes liable to
affect the balance of the bridge. For example, harmonic currents of orders 5 and 7 may be
measured in the supply to 12-pulse rectifiers.
Theoretically the amplitude of a perfect instantaneous switching rectifier should decrease
according to the law:
where
In is the harmonic current of order n;
li is the magnitude of the fundamental current.
In reality, rectifiers do not switch instantaneously and the current waveforms are not truly
of the square-wave type.
The amplitude of harmonic currents depends on the inductive voltage drop due to circuit
inductances and the switching angle. The amplitude of harmonic currents flowing in lines
supplying rectifiers may be approximated by the following law:
n <_
In = In / (n - 5/n) 1 '2 for 5<_ 31
where n is the harmonic order.
This applies if there is good smoothing of the d.c. current, otherwise the level of 5th
harmonic can be higher.
More detailed values of harmonic currents, considering delay angle and inductive voltage
drop, are given in IEC 146.
Arc furnaces may be represented as generators of harmonic currents with an internal
impedance consisting of an inductance and a damping resistance. The current spectrum
shows a discrete spectrum superimposed on a continuous spectrum.
5.2.3 Residential loads
Residential loads have a lower power rating, but may be a major source of harmonic
distortion on account of the large number of appliances used simultaneously and for long
periods. The most impo rtant contributors in this area are television receivers, thyristor-
controlled devices (lamp dimmers, household appliances) and fluorescent lamps. Existing
standards do not allow the use of phase-controlled heating loads.
Television receivers are generally supplied through a rectifier and a high smoothing
rt impulses
capacitor with the result that the current drawn from the network consists of sho
containing a high percentage of harmonics.
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1000-2-1 © IEC – 21 –
The use of thyristor-controlled loads is increasing. Although, the power involved in each
load may be low, the cumulative effects may result in a high distortion of the supply
voltage.
5.3 Effects of harmonics
The main detrimental effects of harmonics are:
defective operation of regulating devices;
malfunction of ripple control and other mains signalling systems, protective relays
and, possibly, other means of control;
additional losses in capacitors and rotating machines;
additional noise from motors and other apparatus;
- telephone interference.
An influence on induction-disc electricity meters is not discernible.
The phenomenon of interference with telephone and communication circuits by inductive
coupling is discussed by CCITT and is not considered further here.
The harmful effects of harmonics on equipment may be classified as either instantaneous
or long-term.
5.3.1 Instantaneous effects
rformance of
These effects are associated with failures, malfunctions or downgraded pe
devices through displacement of zero crossing of the voltage wave. Regulation devices,
electronic equipment and computers are especially susceptible.
High amplitudes of harmonics may cause a malfunction of ripple control receivers and
protective relays.
5.3.2 Long-term effects
Long-term effects are principally thermal. Additional losses and overheating result in
excessive ageing or even damage to capacitors and rotating machines.
6 Interharmonics
6.1 Description of the phenomenon
Between the harmonics of the power frequency voltage and current, further frequencies
can be observed which are not an integer of the fundamental. They can appear as discrete
frequencies or as a wide-band spectrum. Summation effects of interharmonics are not
likely and need not be considered.
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Sources of interharmonics
6.2
Sources of interharmonics can be found in low-voltage networks as well as in
medium-voltage and high-voltage networks. The interharmonics produced by low-voltage
sources mainly influence devices in their vicinity; the interharmonics produced in the
medium-voltage/high-voltage networks flow in the low-voltage networks they supply.
The main sources are static frequency converters, cyclo-converters, subsynchronous
converter cascades, induction motors, welding machines (low-voltage networks) and arc
furnaces (medium-voltage/high-voltage networks only).
There is also low-level background noise superimposed on the low-voltage curve, even in
the absence of a local source of interharmonics.
NOTE - The signals of mains signalling systems could also be considered as interharmonics in the
broadest sense, but it is thought preferable to deal with these separately.
6.2.1 Static frequency converters
Static frequency converters transform the mains voltage into an a.c. voltage of frequency
rts, namely an a.c.-d.c.
lower or higher than the mains frequency. They consist of two pa
rectifier and a d.c.-a.c. inverter. The d.c. voltage is modulated by the output frequency of
the converter and as a result interharmonic currents appear in the input current, causing
interharmonic voltages to be generated in the mains voltage.
Static frequency converters are used mainly for variable frequency drives and are
developing rapidly. Small drives up to some tens of kW are connected directly to the
low-voltage network, larger drives are connected to the medium-voltage network via
dedicated transformers. Similar converters are used to supply medium-frequency
furnaces.
Several forms of static frequency converters exist with different characteristics. The
harmonic and interharmonic frequencies are given by the following formula:
n] x F
fv _ [(pi x m) t 1 ] x f1 t [p2 x
where
p1 is the pulse number of the rectifier;
p2 is the pulse number of the converter;
m are 0, 1, 2, 3 .(integers);
n are 0, 1, 2, 3 .(integers);
F
is the output frequency;
f1
is the fundamental frequency of the supply voltage (e.g. 50 Hz or 60 Hz);
fv is the produced harmonic or interharmonic.
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1000-2-1 ©IEC - 25 -
gives the harmonics. These harmonics in combination with
The combination of p 1 and m
n F
p2, and give the interharmonics.
6.2.2
Cyclo-converters
Cyclo converters are electronic converters of high rating (several MW) which draw
symmetrical three-phase power from the power system to produce a three-phase or single
phase output of low frequency (generally less than 15 Hz) for large slow motor drives.
They consist of two or more controlled rectifiers connected as a bridge.
The formula which gives the harmonic and interharmonic frequencies is the same as for
static frequency converters.
6.2.3 Subsynchronous converter cascades
The purpose of the subsynchronous converter cascade is to control the speed of an
induction motor while reducing the losses when the motor is operating out of the rated
conditions. The usual resistors connected to the rotor terminal of the wound rotor motor
are replaced by a frequency converter connected between the rotor terminal and the lines
that supply the stator of the motor. Interharmonic emission is often low.
6.2.4
Induction motors
Induction motors may give rise to an irregular magnetizing current due to the slots in the
stator and rotor — possibly in association with saturation of the iron — which generates
interharmonics in the low-voltage network. At the normal speed of the motor, the
disturbing frequencies are practically in the range 500 Hz to 2 000 Hz but during the
starting period they run through the whole frequency range up to their final values.
Such motors can be disturbing when they are installed at the end of long overhead
low-voltage lines (>1 km). Interharmonic voltages of up to 1% of the nominal voltage have
been measured. These interharmonic voltages have disturbed ripple control receivers in a
few cases.
6.2.5 Arc welding machines
Welding machines also generate a continuous wide-band frequency spectrum. Welding is
an intermittent process with the duration of the individual welding actions varying between
a second and several seconds.
Welding machines are mostly connected to the low-voltage network. At present no
measurements of interharmonic voltages produced by welding machines are available.
However, due to the intermittent character of the welding process and the high power
involved, the impedance of the supplying networks has to be quite low in order to avoid
disturbing flicker effects. It seems that the limits imposed thereby on the network
impedance reduce interharmonic voltages sufficiently.
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6.2.6 Arc furnaces
Arc furnaces produce continuous but randomly varying interharmonic frequency spectra
due to the irregular input current. These devices have a high rating (50 MVA to 100 MVA)
but are always connected to the medium-voltage/high-voltage network. In order to avoid
excessive voltage fluctuations and flicker disturbances the network impedance should be
low. Consequently interharmonics emission is also low.
The highest interharmonic voltages occur during the starting phase of a melting process.
Typical values are to be investigated.
6.2.7 Background noise
Background noise appears as a Gaussian noise, with a continuous regular frequency
spectrum between the harmonics.
Up to now little detailed investigation has been carried out. Typical voltage levels seem to
be in the range of:
40 mV to 50 mV (= 0,02 % of UN) when measured with a filter bandwidth of 10 Hz;
20 mV to 25 mV (= 0,01 % of UN) when measured with a filter bandwidth of 3 Hz.
6.3 Effects of interharmonics
An effect of interharmonics is the pe
rturbation of ripple control receivers by discrete
frequencies. This effect has been observed with induction motors and arc furnaces,
though it could be caused by the other types of equipment referred to above.
A flicker effect could also appear with discrete frequencies close to the fundamental
frequency. These frequencies may produce amplitude modulation of the fundamental
current and this would be particularly perceptible if the modulation frequency were close to
10 Hz (see 7.3.1). Investigations into this phenomenon are continuing.
7 Voltage fluctuations
7.1
Description of the phenomenon
Voltage fluctuations can be described as a cyclical variation of the voltage envelope or a
series of random voltage changes (see figures 3 and 4) the magnitude of which does not
normally exceed the range of operational voltage changes mentioned in lEC 38 (up
to ±10%).
A clear distinction must be drawn between voltage fluctuations and slow voltage variations
within the same limit of up to ±10% due to gradual load changes in the networks.
Voltage dips and sho rt
interruptions, which have amplitudes of between 10% and 100% of
the nominal voltage, are infrequent and are caused in the main by faults and the operation
of protective systems (see clause 8).
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1000-2-1 © IEC – 29 –
There are various types of voltage fluctuations, which have been classified as follows
(IEC 555-3):
Type a): periodic rectangular voltage changes (step changes) of equal magnitudes (e.g.
switching of single resistive loads) (see figure 5a);
Type b): a series of step changes of voltage which are irregular in time. Their magnitudes
may be equal or not, and in either the negative or positive direction (e.g.
switching of multiple loads) (see figure 5b);
Type c): clearly separated voltage changes which are not all step changes (e.g. switching
of non-resistive loads) (see figure 5c);
Type d): a series of random or continuous voltage fluctuations (e.g. cyclic or randomly
changing loads) (see figure 5d).
Note that two or more changes in the same direction occurring in a total period of not
more than 30 ms are considered to be a single change.
The type of voltage fluctuation may be deduced from the characteristics of the appliance,
or observed by instrumentation.
7.2 Sources of voltage fluctuations
In low-voltage networks domestic appliances are significant sources, but each appliance
will affect only a limited number of consumers.
In general, the main sources are industrial loads:
resistance welding machines;
rolling mills;
mine winders (or large motors with varying loads);
arc furnaces;
arc welding plant.
Of a similar nature are step voltage changes that occur with the connection (or
disconnection) of capacitor banks, or more generally when switching large loads.
It is important to point out that these industrially-produced fluctuations can affect a large
number of consumers from the same source. Operation of all this equipment ranges from
continuous to very infrequent. As there is a wide range of supply impedance on the public
networks, conditions change substantially from the substation to the end of a feeder.
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7.3 Effects of voltage fluctuations
Generally, since voltage fluctuations have an amplitude not exceeding ±10%, most
equipment is not disturbed by this type of disturbance. The main disadvantage which can
be attributed to them is flicker, or fluctuation of luminosity of an incandescent lamp (the
important point is that
...
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