IEC 61724-1:2021

Photovoltaic system performance - Part 1: Monitoring

IEC 61724-1:2021 outlines terminology, equipment, and methods for performance monitoring and analysis of photovoltaic (PV) systems. It also serves as a basis for other standards which rely upon the data collected. This document defines classes of photovoltaic (PV) performance monitoring systems and serves as guidance for monitoring system choices. This second edition cancels and replaces the first edition, published in 2017. This edition includes the following significant technical changes with respect to the previous edition:
- Monitoring of bifacial systems is introduced.
- Irradiance sensor requirements are updated.
- Soiling measurement is updated based on new technology.
- Class C monitoring systems are eliminated.
- Various requirements, recommendations and explanatory notes are updated.

Performances des systèmes photovoltaïques - Partie 1: Surveillance

L'IEC 61724-1:2021 présente une terminologie, des équipements et des méthodes relatifs à la surveillance des performances et à l’analyse des systèmes photovoltaïques (PV). Elle sert également de base à d’autres normes qui s’appuient sur les données collectées. Cette deuxième édition annule et remplace la première édition parue en 2017. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
- Présentation de la surveillance des modules PV bifaciaux.
- Mise à jour des exigences relatives aux capteurs d’éclairement énergétique.
- Mise à jour du mesurage de l’encrassement pour tenir compte des nouvelles technologies.
- Suppression des systèmes de surveillance de classe C.
- Mise à jour de différentes exigences, recommandations et notes explicatives.

General Information

• Status: Published
• Publication Date: 20-Jul-2021
• ICS: 27.160 - Solar energy engineering
• Technical Committee: TC 82 - Solar photovoltaic energy systems
• Drafting Committee: WG 3 - TC 82/WG 3
• Current Stage: PPUB - Publication issued
• Start Date: 13-Aug-2021
• Completion Date: 21-Jul-2021

Relations

• Revises: IEC 61724-1:2017 - Photovoltaic system performance - Part 1: Monitoring
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC 61724-1 ®
Edition 2.0 2021-07
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Photovoltaic system performance –
Part 1: Monitoring
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
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IEC 61724-1 ®
Edition 2.0 2021-07
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Photovoltaic system performance –
Part 1: Monitoring
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.160 ISBN 978-2-8322-5086-0

– 2 – IEC 61724-1:2021 RLV © IEC 2021
CONTENTS
FOREWORD . 6
INTRODUCTION . 8
1 Scope . 10
2 Normative references. 10
3 Terms and definitions . 11
4 Monitoring system classification . 16
5 General . 17
5.1 Measurement precision and uncertainty . 17
5.2 Calibration . 17
5.3 Repeated elements . 17
5.4 Power consumption . 17
5.5 Documentation . 17
5.6 Inspection . 18
6 Data acquisition timing and reporting . 18
6.1 Samples, records, and reports . 18
6.2 Timestamps . 20
6.3 Parameter names . 20
7 Measured parameters Required measurements . 21
8 Irradiance . 27
8.1 Sensor types . 31
8.2 General requirements . 31
8.2.1 Overview . 31
8.2.2 Sensor requirements . 31
8.2.3 Sensor locations . 32
8.2.4 Recalibration. 33
8.2.5 Soiling mitigation . 33
8.2.6 Dew and frost mitigation . 33
8.2.7 Inspection and maintenance . 34
8.2.8 Sensor alignment . 34
8.3 Measurements . 34
8.3.1 Global horizontal irradiance . 34
8.3.2 In-plane irradiance . 34
8.3.3 In-plane rear-side irradiance . 35
8.3.4 In-plane rear-side irradiance ratio . 35
8.3.5 Horizontal albedo . 35
8.3.6 Direct normal irradiance . 35
8.3.7 Diffuse horizontal irradiance . 35
8.3.8 Spectrally matched irradiance . 35
8.3.9 In-plane irradiance for concentrator systems . 36
8.3.10 Spectral irradiance for concentrator systems . 37
8.3.11 Circumsolar ratio measurements for concentrator systems . 37
8.3.12 Satellite remote sensing of irradiance . 38
9 Environmental factors . 39
9.1 PV module temperature . 39
9.2 Ambient air temperature . 41

9.3 Wind speed and direction . 42
9.4 Soiling ratio . 42
9.5 Rainfall . 45
9.6 Snow . 45
9.7 Humidity . 45
10 Tracker system . 45
10.1 Single-axis trackers . 45
10.2 Dual-axis trackers for >20x systems . 45
10.2.1 Monitoring . 45
10.2.2 Pointing error sensor alignment . 45
11 Electrical measurements . 46
11.1 Inverter-level measurements . 46
11.2 Plant-level measurements . 47
12 Data processing and quality check . 48
12.1 Daylight hours Night . 48
12.2 Quality check . 48
12.2.1 Removing invalid readings . 48
12.2.2 Treatment of missing data . 49
13 Calculated parameters . 49
13.1 Overview. 49
13.2 Summations . 50
13.3 Irradiation . 50
13.4 Electrical energy . 51
13.4.1 General . 51
13.4.2 DC output energy . 51
13.4.3 AC output energy . 51
13.5 Array power rating . 51
13.5.1 DC power rating . 51
13.5.2 AC power rating . 52
13.6 Yields . 52
13.6.1 General . 52
13.6.2 PV array energy yield . 52
13.6.3 Final system yield . 52
13.6.4 Reference yield . 52
13.6.5 Bifacial reference yield . 53
13.7 Yield losses . 53
13.7.1 General . 53
13.7.2 Array capture loss . 53
13.7.3 Balance of systems (BOS) loss. 53
13.8 Efficiencies . 54
13.8.1 Array (DC) efficiency . 54
13.8.2 System (AC) efficiency . 54
13.8.3 BOS efficiency . 54
14 Performance metrics . 54
14.1 Overview. 54
14.2 Summations . 55
14.3 Performance ratios . 55
14.3.1 Performance ratio . 55

– 4 – IEC 61724-1:2021 RLV © IEC 2021
14.3.2 Temperature-corrected performance ratios . 56
14.3.3 Bifacial performance ratios . 58
14.4 Performance indices . 59
15 Data filtering .
...

IEC 61724-1 ®
Edition 2.0 2021-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Photovoltaic system performance –
Part 1: Monitoring
Performances des systèmes photovoltaïques –
Partie 1: Surveillance
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.

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ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie
et les microfilms, sans l'accord écrit de l'IEC ou du Comité national de l'IEC du pays du demandeur. Si vous avez des
questions sur le copyright de l'IEC ou si vous désirez obtenir des droits supplémentaires sur cette publication, utilisez
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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.

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containing more than 22 000 terminological entries in English
details all new publications released. Available online and
and French, with equivalent terms in 18 additional languages.
once a month by email.
Also known as the International Electrotechnical Vocabulary

(IEV) online.
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need further assistance, please contact the Customer Service
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IEC 61724-1 ®
Edition 2.0 2021-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Photovoltaic system performance –

Part 1: Monitoring
Performances des systèmes photovoltaïques –

Partie 1: Surveillance
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 27.160 ISBN 978-2-8322-1002-5

– 2 – IEC 61724-1:2021 © IEC 2021
CONTENTS
FOREWORD . 6
INTRODUCTION . 8
1 Scope . 10
2 Normative references. 10
3 Terms and definitions . 11
4 Monitoring system classification . 15
5 General . 16
5.1 Measurement precision and uncertainty . 16
5.2 Calibration . 16
5.3 Repeated elements . 16
5.4 Power consumption . 16
5.5 Documentation . 16
5.6 Inspection . 16
6 Data acquisition timing and reporting . 16
6.1 Samples, records, and reports . 16
6.2 Timestamps . 18
6.3 Parameter names . 18
7 Required measurements . 18
8 Irradiance . 23
8.1 Sensor types . 23
8.2 General requirements . 23
8.2.1 Overview . 23
8.2.2 Sensor requirements . 23
8.2.3 Sensor locations . 24
8.2.4 Recalibration. 25
8.2.5 Soiling mitigation . 25
8.2.6 Dew and frost mitigation . 25
8.2.7 Inspection and maintenance . 26
8.2.8 Sensor alignment . 26
8.3 Measurements . 26
8.3.1 Global horizontal irradiance . 26
8.3.2 In-plane irradiance . 26
8.3.3 In-plane rear-side irradiance . 27
8.3.4 In-plane rear-side irradiance ratio . 27
8.3.5 Horizontal albedo . 27
8.3.6 Direct normal irradiance . 27
8.3.7 Diffuse horizontal irradiance . 27
8.3.8 Spectrally matched irradiance . 27
8.3.9 In-plane irradiance for concentrator systems . 28
8.3.10 Spectral irradiance for concentrator systems . 29
8.3.11 Circumsolar measurements for concentrator systems . 29
8.3.12 Satellite remote sensing of irradiance . 30
9 Environmental factors . 31
9.1 PV module temperature . 31
9.2 Ambient air temperature . 31

9.3 Wind speed and direction . 32
9.4 Soiling ratio . 32
9.5 Rainfall . 33
9.6 Snow . 33
9.7 Humidity . 33
10 Tracker system . 33
10.1 Single-axis trackers . 33
10.2 Dual-axis trackers . 33
10.2.1 Monitoring . 33
10.2.2 Pointing error sensor alignment . 33
11 Electrical measurements . 34
11.1 Inverter-level measurements . 34
11.2 Plant-level measurements . 34
12 Data processing and quality check . 35
12.1 Night . 35
12.2 Quality check . 35
12.2.1 Removing invalid readings . 35
12.2.2 Treatment of missing data . 35
13 Calculated parameters . 36
13.1 Overview. 36
13.2 Summations . 36
13.3 Irradiation . 36
13.4 Electrical energy . 37
13.4.1 General . 37
13.4.2 DC output energy . 37
13.4.3 AC output energy . 37
13.5 Array power rating . 37
13.5.1 DC power rating . 37
13.5.2 AC power rating . 38
13.6 Yields .
...