IEC TS 63222-2:2023

IEC TS 63222-2 ®
Edition 1.0 2023-10
TECHNICAL
SPECIFICATION
colour
inside
Power quality management –
Part 2: Power Quality Monitoring System

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

IEC Secretariat Tel.: +41 22 919 02 11
3, rue de Varembé info@iec.ch
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigendum or an amendment might have been published.

IEC publications search - webstore.iec.ch/advsearchform IEC Products & Services Portal - products.iec.ch
The advanced search enables to find IEC publications by a Discover our powerful search engine and read freely all the
variety of criteria (reference number, text, technical publications previews. With a subscription you will always have
committee, …). It also gives information on projects, replaced access to up to date content tailored to your needs.
and withdrawn publications.
Electropedia - www.electropedia.org
IEC Just Published - webstore.iec.ch/justpublished
The world's leading online dictionary on electrotechnology,
Stay up to date on all new IEC publications. Just Published
containing more than 22 300 terminological entries in English
details all new publications released. Available online and once
and French, with equivalent terms in 19 additional languages.
a month by email.
Also known as the International Electrotechnical Vocabulary

(IEV) online.
IEC Customer Service Centre - webstore.iec.ch/csc

If you wish to give us your feedback on this publication or need
further assistance, please contact the Customer Service
Centre: sales@iec.ch.
IEC TS 63222-2 ®
Edition 1.0 2023-10
TECHNICAL
SPECIFICATION
colour
inside
Power quality management –
Part 2: Power Quality Monitoring System

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.020  ISBN 978-2-8322-7588-7

– 2 – IEC TS 63222-2:2023 © IEC 2023
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 7
4 Purposes and applications analysis . 8
5 Preliminary study . 9
5.1 Background information collection . 9
5.2 Selection of monitoring sites . 10
5.3 Selection of monitoring parameters . 11
5.4 Voltage Transformer (VT)/Current Transformer (CT) characteristics analysis . 12
5.5 Data sources . 12
6 PQ monitoring system structure and functions . 13
6.1 General . 13
6.2 Function modules . 14
6.2.1 Data collection . 14
6.2.2 Communication . 14
6.2.3 Data storage . 15
6.2.4 Data processing and analysis . 15
6.3 System structure . 15
6.3.1 General . 15
6.3.2 Brower/Server (B/S) and Client/Server (C/S) architecture . 15
6.3.3 Centralized and distributed architecture . 15
7 Communication and protocol . 16
7.1 General . 16
7.2 Communication . 17
7.2.1 Communication mode . 17
7.2.2 Communication interface . 17
7.3 Protocol . 17
8 Data storage and management . 18
8.1 Data storage . 18
8.2 Data management . 19
8.2.1 Data backup . 19
8.2.2 Data quality management . 19
8.2.3 Missing data checking . 19
8.2.4 Data security . 20
8.3 Data setting . 20
8.3.1 General . 20
8.3.2 Time aggregation setting . 20
8.3.3 Grouping and sub-grouping setting . 20
8.3.4 Flagged data pre-processing setting . 20
8.3.5 Sites attribution setting . 20
8.3.6 Time setting . 20
8.3.7 Accessing setting. 21
8.4 Power quality assessment . 21
8.5 Advanced data analysis . 21
Annex A (informative) Characteristics of instrument transformers . 22

A.1 Inductive instrument transformers . 22
A.1.1 Inductive voltage transformers . 22
A.1.2 Inductive current transformers . 22
A.2 Low-power instrument transformers (LPIT) . 23
A.2.1 Low-power voltage transformers (LPVT) . 23
A.2.2 Low-power current transformers (LPCT) . 24
A.3 Capacitive voltage transformers (CVT) . 24
Bibliography . 26

Figure 1 – Function modules of power quality monitoring system . 13
Figure 2 – Structure of a typical power quality monitoring system . 14
Figure 3 – Centralised architecture . 16
Figure 4 – Distributed architecture . 16
Figure A.1 – Frequency response of a typical 420 kV inductive VT . 22
Figure A.2 – Different types of LPVTs . 23
Figure A.3 – Estimated amplitude and phase error up to 2 kHz . 23
Figure A.4 – Frequency response of an optical current transformer . 24
Figure A.5 – Frequency response of a Rogowski current transformer . 24
Figure A.6 – Frequency response of a typical 220 kV CVT . 25

– 4 – IEC TS 63222-2:2023 © IEC 2023
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
POWER QUALITY MANAGEMENT –
Part 2: Power quality monitoring system

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international
co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and
in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports,
Publicly Available Specifications (PAS) and Guides (hereafter referred to as "IEC Publication(s)"). Their
preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with
may participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for
Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence between
any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent
rights. IEC shall not be held responsible for identifying any or all such patent rights.
IEC TS 63222-2 has been prepared by IEC technical committee 8: System aspects of electrical
energy supply. It is a Technical Specification.
The text of this Technical Specification is based on the following documents:
Draft Report on voting
8/1658/DTS 8/1674/RVDTS
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this Technical Specification is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at http://www.iec.ch/standardsdev/publications.

A list of all parts in the IEC 63222 series, published under the general title Power quality
management, can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under 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 document indicates
that it contains colours which are considered to be useful for the correct understanding
of its contents. Users should therefore print this document using a colour printer.

– 6 – IEC TS 63222-2:2023 © IEC 2023
POWER QUALITY MANAGEMENT –
Part 2: Power Quality Monitoring System

1 Scope
This part of IEC 63222 defines technical requirements for designing a power quality monitoring
system for public power supply networks. It is applicable for LV, MV and HV public power supply
networks.
The design procedure of a power quality monitoring system (PQMS) generally includes the
following four steps:
• Step 1: purpose and application analysis
Analyse power quality monitoring (PQM) demand and define the purpose of PQM.
• Step 2: preliminary study
Collect background information such as network configuration, the parameters of instrument
transformers, e.g. the output levels and performance capabilities, attributes of loads or
distributed generations (DG), communication conditions, budgets, and other restrictive
conditions, and select the parameters to be monitored and monitoring sites according to
corresponding principles.
• Step 3: system structure design
Design the overall structure of the monitoring system according to the monitoring purpose
based on the analysis of the advantages and disadvantages of various system structures.
• Step 4: detailed design of functional modules
Design the function modules of data collection, communication, data storage, data
processing and analysis in detail according to the functional requirements.
This document defines the main purposes of PQM and gives recommendations for preliminary
study, such as how to select monitoring sites and monitoring parameters and whether the
instrument transformer is suitable for monitoring. This document also classifies the PQMS
structure and specifies the functional requirements of the modules such as data collection,
communication, data storage, data processing and analysis.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies.
For undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 61000-2-2:2002, Electromagnetic compatibility (EMC) – Part 2-2: Environment −
Compatibility levels for low-frequency conducted disturbances and signalling in public low-
voltage power supply systems
IEC TR 61000-3-6, Electromagnetic compatibility (EMC) – Part 3-6: Limits – Assessment of
harmonic emission limits for the connection of distorting installations to MV, HV and EHV power
systems
IEC TR 61000-3-7:2008, Electromagnetic compatibility (EMC) – Part 3-7: Limits − Assessment
of emission limits for the connection of fluctuating load installations to MV, HV and EHV power
systems
IEC TR 61000-3-13, 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 61000-4-7, Electromagnetic compatibility (EMC) – Part 4-7: Testing and measurement
techniques − General guide on harmonics and interharmonics measurements and
instrumentation, for power supply systems and equipment connected thereto
IEC 61000-4-30:2015, Electromagnetic compatibility (EMC) – Part 4-30: Testing and
measurement techniques − Power quality measurement methods
IEC TR 61850-90-17:2017, Communication networks and systems for power utility automation
- Part 90-17: Using IEC 61850 to transmit power quality data
IEC 61869-6:2016, Instrument transformers – Part 6: Additional general requirements for low
power instrument transformers
IEC 61869-11, Instrument transformers – Part 11: Additional requirements for low power
passive voltage transformers
IEC TR 61869-103, Instrument transformers – Part 103: The use of instrument transformers for
power quality measurement
IEC 62443 (all parts), Industrial communication networks − Network and system security
IEC 62586-1:2017, Power quality measurement in power supply systems – Part 1: Power quality
Instruments (PQI)
IEC 62586-2, Power quality measurement in power supply systems – Part 2: Functional tests
and uncertainty requirements
IEC TS 62749:2020, Assessment of power quality − Characteristics of electricity supplied by
public networks
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
NOTE Terms are listed in alphabetical order.
3.1
flagged data
for any measurement time interval in which interruptions, dips or swells occur, the marked
measurement results of all other parameters made during this time interval
[SOURCE: IEC 61000-4-30:2021, 3.5]
3.2
flicker
impression of unsteadiness of visual sensation induced by a light stimulus whose luminance or
spectral distribution fluctuates with time
[SOURCE: IEC 60050-161:1990, 161-08-13]
3.3
point of common coupling
PCC
point in an electric power system, electrically nearest to a particular load, at which other loads
are, or may be, connected
Note 1 to entry: These loads can be either devices, equipment or systems, or distinct network user's installations.
[SOURCE: IEC TS 62749:2020, 3.25, modified – "network" has been replaced by "system"]

– 8 – IEC TS 63222-2:2023 © IEC 2023
3.4
point of connection
POC
reference point on the electric power system where the user's electrical facility is connected
[SOURCE: IEC 60050-617:2009, 617-04-01]
3.5
power quality
PQ
characteristics of the electric current, voltage and frequencies at a given point in an electric
power system, evaluated against a set of reference technical parameters
Note 1 to entry: These parameters might, in some cases, relate to the compatibility between electricity supplied in
an electric power system and the loads connected to that electric power system.
[SOURCE: IEC 60050-617:2009, 617-01-05]
3.6
power quality instrument
PQI
instrument whose main function is to measure, record and possibly monitor power quality
parameters in power supply systems, and whose measuring methods (class A or class S) are
defined in IEC 61000-4-30
[SOURCE: IEC 62586-1:2017, 3.1.1]
3.7
residual voltage
minimum value of U rms(½) recorded during a voltage dip or interruption
[SOURCE: IEC 61000-4-30:2021, 3.28]
3.8
time aggregation
combination of several sequential values of a given parameter (each determined over identical
time intervals) to provide a value for a longer time interval
[SOURCE: IEC 61000-4-30:2021, 3.31]
3.9
voltage deviation
difference between the supply voltage at a given instant and the declared supply voltage
3.10
voltage dip
sudden reduction of the voltage at a point in an electrical system followed by voltage recovery
after a short period of time from a few cycles to a few seconds
[SOURCE: IEC 60050-161:1990, 161-08-10]
3.11
voltage unbalance
in a polyphase system, a condition in which the magnitudes of the phase voltages or the phase
angles between consecutive phases are not all equal (fundamental component)
[SOURCE: IEC TS 62749:2020, 3.47]
4 Purposes and applications analysis
The most important step in the design of a PQ monitoring system is clear identification of the
purpose for PQ monitoring, which is crucial for the selection of monitoring sites, the selection
of monitoring parameters, monitoring system structure and requirements of functional modules,
etc.
The following main purposes for PQ monitoring can be distinguished from the present PQM
practices:
• Compliance verification
Compliance verification compares a defined set of power quality parameters with limits given
by standards, contracts or regulatory specifications. The verification results are reported
externally to promote power quality management. It includes typical tasks such as
verification of compliance with the connection contracts for a connected user, or verification
of compliance with regulatory specification for a system operator. Compliance verification
is usually done for individual sites and provides qualitative results. It can also be applied to
multiple sites by using appropriate aggregation.
• Performance analysis
Performance analysis is mainly undertaken by system operators to assess average power
quality levels in a grid. The analysis results can be used to determine long term trends by
system operators and provide support for strategic planning, asset management and
benchmarking, etc. Performance analysis is usually done for multiple sites but can be
applied to single sites as well. It provides quantitative results (indices), which can be
selected flexibly and it is not mandatory to follow specific standards. Benchmarking
compares one or more indices for different sets of sites and is part of performance analysis.
• Site characterization
Site characterization is used to describe PQ at a specific site in a detailed way. It includes
typical tasks such as to predefine the expected power quality for a potential customer or to
assess and verify power quality once the customer is already connected to the grid. It is
important to know the power quality at a particular site, in particular to predict the effect of
a new non-linear, unbalanced or intermittent load, and subsequently survey the ability of the
site to comply with the contractual constraints.
• Troubleshooting
Troubleshooting is used to diagnose power quality related problems such as system
harmonic resonance, the abnormal interruption of the customer production process,
equipment malfunction, etc. A long term PQM campaign by permanent monitoring equipment
can provide more useful information for troubleshooting, especially for process interruptions
caused by voltage dips. Typically, raw unaggregated power quality measurement data are
most useful for troubleshooting, as they permit any type of post-processing preferred.
• Advanced applications and studies
Advanced applications and studies are relevant for purposes of different aspects from both
system operator's side and end user's side, e.g. how to improve the efficiency of system
operation, how to promote end user's immunity capability, etc., it includes more specific
measurements and deep analyses that are often not part of the daily business. Typical
applications and studies include fault location, signature analysis and studies of propagation
of power quality phenomena.
5 Preliminary study
5.1 Background information collection
The following background information should be collected before the design of the PQMS:
• Power supply network configuration to be monitored
The configuration of the power supply network to be monitored such as power grid
topological structure (e.g. radial or meshed networks), three-phase or single-phase, short-
circuit powers, the categories of feeders available for monitoring (e.g. urban, semi urban or
semi-rural, rural), and the parameters of instrument transformers, e.g. the output levels and
performance capabilities, should be collected, which can be used for the selection of
monitoring sites.
– 10 – IEC TS 63222-2:2023 © IEC 2023
• Attributes and information of loads or DGs
The attributes and information of loads or DGs should be collected, such as the access
location, voltage level, and installed capacity of wind farms, solar plants, electric railways,
arc furnaces, energy storage power stations, and electric vehicle charging infrastructure or
stations, etc.
• Existing communication condition
Understanding the existing communication condition available for PQ monitoring is very
important. The communication between PQ equipment and data centre will be based on the
available conditions. Analysis should also be made to carry out whether the existing
communication condition is enough and feasible to be used for the operation of future
PQMS, otherwise measures should be taken to improve it in advance.
• Constraints
Constraints should be clearly identified in advance, e.g., budget, limited condition at
present, etc. The PQMS designing should be subject to these factors.
• Future development anticipation
Understanding system development planning in short term, medium term and long term is
crucial for PQMS designing. Technically and economically, PQMS designing should be
based on and adapted to power supply system planning, especially for PQMS structure
selection, data storage strategy selection and configuration of different kinds of function
services, although it can be updated and upgraded in the future step by step.
Generally, the anticipation should not only focus on the development of the supply system
topological structure, but also on the trend of power station digitalization and the connection
scale of power-electronic interfaced renewable energy.
5.2 Selection of monitoring sites
The selection of monitoring sites is strongly related to the power grid architecture and also to
monitoring purpose. The principles for selecting monitoring sites for different monitoring
purposes are given below.
• Compliance verification
The monitoring sites should be set up in accordance with the standards, the contracts or
the regulation that the compliance verification is based on. In most cases, the compliance
verification only requires voltage measurements, and the monitoring sites should be at
customer's POC or PCC. When the compliance verification additionally requires current
measurements, the monitoring sites should be located somewhere along the feeder
supplying the customer (either at customer's POC or at the substation busbar to which the
feeder is connected).
• Performance analysis
The system performance analysis can be scalable by focusing on the part of certain area,
monitoring at only a limited number of sites from all sites will be sufficient. Statistical
methods are recommended to select partially representative site samples in order to achieve
an acceptable accuracy and to reduce the costs.
• Site characterization
For the background PQ characterization of the site that a new customer may connect to, the
monitoring sites should be as close as possible to the customer's future connection point,
such as the nearest substation busbar or any other close customer where PQ is already
monitored. For performance verification of existing customers, the monitoring sites should
be at customer's POC or PCC.
• Troubleshooting
The monitoring sites should be as close as possible to the location where the PQ problem
or customer complaints is reported, such as the terminal of the connected equipment that
failed, the PCC of the customer who made the complaints or the outgoing feeder in the
substation. Additionally, disturbance propagation analysis may be needed, and relevant
sites accordingly may be selected.

• Advanced applications and studies
PQ monitoring sites should be set up according to the specific tasks of advanced
applications and studies. For example, for signature analysis of specific equipment, the
monitoring sites should be as close as possible to the concerned equipment, such as a
transformer branch or capacitor branch.
5.3 Selection of monitoring parameters
The selection of monitoring parameters mainly depends on the monitoring purpose. The
following factors need to be considered to determine the monitoring parameters:
• Power quality indicators to be monitored: such as frequency, root-mean-square (RMS)
voltage, voltage unbalance, voltage harmonics, voltage interharmonics, voltage transients
and voltage dips and swells.
• Voltage or current to be measured: generally, it is required to measure voltage, the need to
measure current should be determined according to the monitoring purpose aforementioned.
• Time interval and data processing method: time interval and aggregation method different
from that defined in IEC 61000-4-30 may be needed for monitoring purposes such as
troubleshooting and site characterization. Time interval less than 10 minutes for aggregation
may be selected. If it is needed, the maximum/minimum/average RMS value may be
recorded in the selected aggregation time duration.
• Voltage dip and swell are characterised by retained voltage and time duration according to
IEC 61000-4-30. As an advanced option, it is recommended to record voltage and current
waveforms during voltage dip and swell. A pre-windows and a post window during the event
may be included according to the performance of PQ analysis requirement.
The details of the selection of monitoring parameters for different monitoring purposes are given
below.
• Compliance verification
The parameters to be monitored depend on the standard, the contract or the regulation
which is to be applied. The most common parameters required are frequency, RMS voltage,
voltage unbalance, voltage harmonics and voltage dips and swells.
Most standards or recommendations only call for compliance with respect to voltage
disturbances, e.g. IEC TR 61000-3-6, IEC TR 61000-3-7 and IEC TR 61000-3-13. Some
national regulations and grid codes require measurement of current parameters as well as
voltages.
According to IEC TS 62749, the aggregated values (3 second values, 10 minute values and
2 hour values) are required for continuous PQ phenomena assessment. Residual voltage
and duration combined with the RMS voltage variation shape are required for single event
assessment.
• Performance analysis
For performance analysis of a system with a large number of sites, it is generally required
to monitor only voltage disturbances. Generally, 10 minute values are sufficient to obtain an
accurate picture of the performance across a grid. Weighting rules may be used applying
both to statistical indices and events in order to obtain results that are universally
comparable. Refer to IEC TS 62749:2020, Annex B for detailed information on weighting
rules.
• Site characterization
For characterization of a particular site that a new customer may connect to, the parameters
to be monitored depend on the standard used and the nature of the customer's load. For
non-linear and fluctuating loads such as electrified railways, arc furnaces, rolling mills,
parameters such as voltage unbalance, voltage harmonics and flicker should be monitored.
For electric vehicle charging facilities, variable speed drives or renewable energy
generations with power electronics as interface, parameters such as voltage harmonics up
to 40th (60 Hz system) or 50th (50 Hz system) and corresponding interharmonics should be
monitored. When it is needed, frequencies up to 150 kHz may be measured. For voltage

– 12 – IEC TS 63222-2:2023 © IEC 2023
sensitive loads such as automatic production lines, parameters such as supply voltage
variations, voltage dips and voltage swells should be monitored.
Generally, 10-minute values are sufficient. However shorter intervals (e.g. 3 seconds,
1 minute) may be used for more details depending on the nature of the customer's loads.
• Troubleshooting
In order to troubleshoot specific problems, e.g. equipment malfunction or the abnormal
interruption of the customer production process, the parameters to be monitored depend on
the problem being investigated (e.g. flicker at an arc furnace or rolling mill) and can include
transients. It is recommended to use shorter interval values, such as 3 second values or
1 minute values. Particularly in the case of transients, raw unaggregated measurement data,
e.g. waveform data, are most useful. Waveform data triggered by PQ parameters related to
the problems and even continuous recording of waveforms may be required.
In this case, both voltage and current are required to be monitored, since combined voltage
and current can help to determine if the disturbance comes from upstream or downstream.
In some cases, the phase angle may be needed.
• Advanced applications and studies
For the purpose of advanced applications and studies, the parameters to be monitored
depend on the specific application. For example, in the case of studying propagation of PQ
phenomena, the parameter of interest (e.g. flicker, unbalance and harmonics) needs to be
monitored in a consistent and comparable manner on each system. Many applications
require the measurement of currents as well as voltages (e.g. fault location, signature
analysis).
5.4 Voltage Transformer (VT)/Current Transformer (CT) characteristics analysis
The frequency response of instrument transformers have a significant impact on the overall
accuracy of the PQ measurements, especially for harmonics. Therefore, attention shall be paid
to the accuracy and frequency bandwidth of instrument transformers. The accuracy
requirements of instrument transformers should be determined according to the monitoring
purposes. For example, a higher accuracy may be necessary for compliance verification rather
than for performance analysis. Refer to Annex A for detailed characteristics of each kind
instrument transformers.
NOTE The impact on the accuracy of instrument transformers in case of multiple intelligent electronic devices (IED)
connecting to a single VT/CT cannot be negligible.
5.5 Data sources
The data sources mainly include: fixed instruments, portable instruments, data files and other
devices or systems with PQM functions. The selection of monitoring data sources depends on
monitoring purposes and cost constraints.
• Fixed instruments
Fixed instruments are used for long-term, continuous PQM, which helps to obtain PQ
parameter variations within a year or a week and get information on relatively rare voltage
events such as voltage dips and swells. Fixed instruments can be used for various
monitoring purposes, especially where it is necessary to monitor voltage dips and swells.
• Portable instruments
Portable instruments are used for temporary and short-term PQM. The monitoring using
portable instruments shall be over a time period sufficient to determine the normal
characteristic operating cycles at the site. In general, one or two full business cycles may
be sufficient for this purpose. The business cycle is one week in the case of most commercial
or residential loads, but it can be as short as a few hours for an industrial installation.
Portable instruments can be used for performance analysis with a rotating approach, where
a monitor stays at a site for a specific period of time to capture a sample of measurements
and then is moved to another site.

• Others
Other data sources include:
a) Other devices that can provide monitoring data, such as smart meters, relays,
controllers, remote terminal units (RTU), phasor measurement units (PMU). Especially
for performance analysis, these devices can provide useful information due to their wide
applications in future power grids.
b) PQ data files, such as power quality data interchange format (PQDIF) files and
COMTRADE files.
c) Other systems that can provide monitoring data, such as supervisory control and data
acquisition (SCADA) system, wide area measurement system (WAMS) and the main
station system for the access of smart meters, RTUs and other devices.
The requirements of monitoring instruments should be determined according to the monitoring
purpose. For example, IEC 61000-4-30 Class A compliant instruments should be used for
compliance verification according to standards or regulatory specifications. IEC 61000-4-30
Class A or S compliant instruments can be used for performance analysis. The performance of
monitoring instruments should comply with IEC 62586-1 and IEC 62586-2.
6 PQ monitoring system structure and functions
6.1 General
The functions of the PQMS generally include data collection, communication, data storage, data
processing and analysis, system maintenance, which can be presented as function modules.
Figure 1 shows the various modules of the system and their main functions.
The above-mentioned functions can reside in various hardware or software components of the
system. Note that these functions do not necessarily always match up with separate devices,
as several functions can be performed by a single device. As an example, a high-performance
PQI can collect the monitoring data, store it temporarily, analyse it and transmit it through the
network, which can be called a simple PQ monitoring system.
Logically, several services undertaking the same function may be needed for large scale
monitoring system.
PQMS can be based on common communication infrastructure, required for other systems like
power management system (PMS) or energy management system (EMS).

Figure 1 – Function modules of power quality monitoring system

– 14 – IEC TS 63222-2:2023 © IEC 2023
The structure and function of the PQMS are closely related to the monitoring purpose. For
example, for the purpose of compliance verification at individual sites, a PQ monitoring system
consisting of only a few PQIs is sufficient. For the purpose of performance analysis at multiple
sites in a grid, a complicated PQ monitoring system containing multiple servers and software
may be required. Figure 2 shows the structure of a typical PQ monitoring system for the purpose
of performance analysis.
Figure 2 – Structure of a typical power quality monitoring system
Routine maintenance work should be performed to ensure the system availability, including
monitoring site management, access management, system configuration, communication
management, data backup, etc.
6.2 Function modules
6.2.1 Data collection
The principles of data collection from data sources (e.g. PQIs, smart meters) to PQ monitoring
system rely on the relevant purposes. For general PQ assessment or benchmarking, data record
of PQ parameters defined in IEC TS 62749 should be transferred. For troubleshooting or
advanced data application, thresholds triggered waveform, 150/180 cycle record, or
aggregation duration less than 10 min record may be collected.
If the PQI is used for long term PQ assessment, in order to reduce the massive data, only the
resultant evaluation conclusion can be transferred.
6.2.2 Communication
In order to ensure the reliable transmission of monitoring data between the monitoring data
source and the monitoring system, the communication module should be designed according to
the monitoring purpose and considering sufficient flexibility, and the communication mode,
communication interface and protocol should be selected reasonably. Details of communication
and protocol are given in Clause 7.

6.2.3 Data storage
The function of data storage module is to store the monitoring data in a suitable way so that it
can be accessed at any time when needed. There are three different data storage strategies:
centralized, distributed and hybrid. Different data storage strategies should be adopted based
on monitoring purposes. For example, when the monitoring purpose is performance analysis,
there is no need to upload all PQ monitoring data to the central database for a monitoring
system with hundreds of monitoring sites since it will be rarely used. In this case, it is
recommended to adopt the hybrid storage strategy, that is, only the most useful data (e.g.
statistical data) are uploaded to the central database, and the detailed data (e.g. waveforms,
harmonics, interharmonics) can be stored in the distributed database. See 6.3.3 for details of
data storage.
6.2.4 Data processing and analysis
The function of data processing and analysis module is to process and analyse a large amount
of monitoring data collected according to monitoring purposes and present the analysis results
to system users in an easy-to-understand manner, including power quality assessment,
graphics or table display, data statistics, etc. This module should also have data management
functions, such as data backup, data qu
...