IEC TR 61000-3-13:2008
(Main)Electromagnetic compatibility (EMC) - Part 3-13: Limits - Assessment of emission limits for the connection of unbalanced installations to MV, HV and EHV power systems
Electromagnetic compatibility (EMC) - Part 3-13: Limits - Assessment of emission limits for the connection of unbalanced installations to MV, HV and EHV power systems
This part of IEC 61000 provides guidance on principles which can be used as the basis for determining the requirements for the connection of unbalanced installations (i.e. three-phase installations causing voltage unbalance) to MV, HV and EHV public power systems (LV installations are covered in other IEC documents). For the purposes of this report, an unbalanced installation means a three-phase installation (which may be a load or a generator) that produces voltage unbalance on the system. The connection of single-phase installations is not specifically addressed, as the connection of such installations is under the control of the system operator or owner. The general principles however may be adapted when considering the connection of single-phase installations. The primary objective is to provide guidance to system operators or owners on engineering practices, which will facilitate the provision of adequate service quality for all connected customers. In addressing installations, this document is not intended to replace equipment standards for emission limits. The report addresses the allocation of the capacity of the system to absorb disturbances. It does not address how to mitigate disturbances, nor does it address how the capacity of the system can be increased. Since the guidelines outlined in this report are necessarily based on certain simplifying assumptions, there is no guarantee that this approach will always provide the optimum solution for all unbalanced load situations. The recommended approach should be used with flexibility and judgment as far as engineering is concerned, when applying the given assessment procedures in full or in part. The system operator or owner is responsible for specifying requirements for the connection of installations which may cause unbalance on the system. The disturbing installation is to be understood as the complete customer's installation (i.e. including balanced and unbalanced parts). Problems related to unbalance fall into two basic categories.
- Unbalanced installations that draw negative-sequence currents which produce negative-sequence voltages on the supply system. Examples of such installations include arc furnaces and traction loads (typically connected to the public network at HV), and three phase installations where the individual loads are not balanced (typically connected at MV and LV). Negative-sequence voltage superimposed onto the terminal voltage of rotating machines can produce additional heat losses. Negative-sequence voltage can also cause non-characteristic harmonics (typically positive-sequence 3rd harmonic) to be produced by power converters.
- Unbalanced installations connected line-to-neutral can also draw zero-sequence currents which can be transferred or not into the supply system depending on the type of connection of the coupling transformer. The flow of zero-sequence currents in a grounded neutral system causes zero-sequence unbalance affecting line-to-neutral voltages. This is not normally controlled by setting emission limits, but rather by system design and maintenance. Ungrounded-neutral systems and phase-to-phase connected installations are not, however, affected by this kind of voltage unbalance. This report gives guidance only for the coordination of the negative-sequence type of voltage unbalance between different voltage levels in order to meet the compatibility levels at the point of utilisation. No compatibility levels are defined for zero-sequence type of voltage unbalance as this is often considered as being less relevant to the coordination of unbalance levels compared to the first type of voltage unbalance. However, for situations where a non-zero impedance exists between neutral and earth with the system still being effectively grounded (i.e., where the ratio between zero-sequence, X0 and positive sequence reactance X1 is 0 < X0/X1 = 3), this type of voltage unbalance can be of concern especially when the type of connection
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IEC/TR 61000-3-13
Edition 1.0 2008-02
TECHNICAL
REPORT
BASIC EMC PUBLICATION
Electromagnetic compatibility (EMC) –
Part 3-13: Limits – Assessment of emission limits for the connection of
unbalanced installations to MV, HV and EHV power systems
IEC/TR 61000-3-13:2008(E)
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IEC/TR 61000-3-13
Edition 1.0 2008-02
TECHNICAL
REPORT
BASIC EMC PUBLICATION
Electromagnetic compatibility (EMC) –
Part 3-13: Limits – Assessment of emission limits for the connection of
unbalanced installations to MV, HV and EHV power systems
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
X
CODE PRIX
ICS 33.100.10 ISBN 2-8318-9607-X
– 2 – TR 61000-3-13 © IEC:2008(E)
CONTENTS
FOREWORD.4
INTRODUCTION.6
ACKNOWLEDGMENT.7
1 Scope.8
2 Normative references .9
3 Terms and definitions .9
4 Basic EMC concepts related to voltage unbalance.14
4.1 Compatibility levels .14
4.2 Planning levels.15
4.2.1 Indicative values of planning levels.15
4.2.2 Assessment procedure for evaluation against planning levels.15
4.3 Illustration of EMC concepts.16
4.4 Emission levels .17
5 General principles .18
5.1 Stage 1: simplified evaluation of disturbance emission .19
5.2 Stage 2: emission limits relative to actual system characteristics.19
5.3 Stage 3: acceptance of higher emission levels on a conditional basis.19
5.4 Responsibilities .19
6 General guidelines for the assessment of emission levels .20
6.1 Point of evaluation.20
6.2 Definition of unbalance emission level.20
6.3 Assessment of emission levels from unbalanced installations.21
7 General summation law .21
8 Emission limits for unbalanced installations in MV systems .22
8.1 Stage 1: simplified evaluation of disturbance emission .22
8.2 Stage 2: emission limits relative to actual system characteristics.23
8.2.1 Global emission to be shared between the sources of unbalance .23
8.2.2 Individual emission limits .24
8.3 Stage 3: acceptance of higher emission levels on a conditional basis.26
8.4 Summary diagram of the evaluation procedure .27
9 Emission limits for unbalanced installations in HV or EHV systems.29
9.1 Stage 1: simplified evaluation of disturbance emission .29
9.2 Stage 2: emission limits relative to actual system characteristics.29
9.2.1 Assessment of the total available power .29
9.2.2 Individual emission limits .30
9.3 Stage 3: acceptance of higher emission levels on a conditional basis.32
Annex A (informative) Guidance for setting planning levels and emission limits .33
Annex B (informative) Calculation examples for determining emission limits .38
Annex C (informative) List of principal letter symbols, subscripts and symbols.39
Bibliography.41
TR 61000-3-13 © IEC:2008(E) – 3 –
Figure 1 – Illustration of basic voltage quality concepts with time/ location statistics
covering the whole system.17
Figure 2 – Illustration of basic voltage quality concepts with time statistics relevant to
one site within the whole system.17
Figure 3 – Illustration of the emission vector U /U and its contribution to the
2i 1
measured unbalance at the point of evaluation. .20
Figure 4 – Example of a system for sharing global contribution at MV.23
Figure 5 – Diagram of evaluation procedure.28
Figure 6 – Determination of S for a simple HV or EHV system.29
t
Figure 7 – Determination of S for a meshed HV or EHV system .30
t
Figure A.1 – The reduction factor T as a function of the factors k k , and k .36
,
uML m s sc
Figure A.2 – Example of unbalance ratio measurement for a remote mine with largely
motor loading.36
Table 1 – Compatibility levels for voltage unbalance in low and medium voltage
systems reproduced from references IEC 61000-2-2 and IEC 61000-2-12 .14
Table 2 – Indicative values of planning levels for voltage unbalance (negative-
sequence component) in MV, HV and EHV power systems .15
Table 3 – Indicative value of exponent for the summation of general unbalanced
installations .22
Table A.1 – Portion of unbalance for accounting for the system inherent asymmetries .34
Table A.2 – Summation of unbalance from different sources .35
Table A.3 – Range of values of planning levels given different parameters .37
– 4 – TR 61000-3-13 © IEC:2008(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTROMAGNETIC COMPATIBILITY (EMC) –
Part 3-13: Limits –
Assessment of emission limits for the connection of
unbalanced installations to MV, HV and EHV power systems
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