Photovoltaic power systems - Reliability practices for operation

IEC TS 63265:2022 outlines methods that can be utilized to ensure reliability throughout the PVPS project phases. It is derived from a management motivation for long lasting and cost-effective energy performance, energy production, secure production and revenue, and safe function. The application of reliability practices in this document is designed to be practical and reduce the costs of unreliability. This document further identifies and defines a normative minimum set of processes and tools to meet the requirements of this document.
Key objectives of this document are to inform users of reliability tools and assessment methods (historic, predictive, and analytical) that can satisfy the stakeholders needs for dependable PV Power System (PVPS) operation. This document provides a fundamental process for ensuring reliability needs can be understood and met. IEC TS 63019 addresses availability which is a higher-level metric that combines reliability and maintainability, and it complements this document as a key normative standard. It should be used in combination with this document.

General Information

Status
Published
Publication Date
27-Jun-2022
Current Stage
PPUB - Publication issued
Completion Date
28-Jun-2022
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IEC TS 63265
Edition 1.0 2022-06
TECHNICAL
SPECIFICATION
colour
inside
Photovoltaic power systems – Reliability practices for operation
IEC TS 63265:2022-06(en)
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---------------------- Page: 2 ----------------------
IEC TS 63265
Edition 1.0 2022-06
TECHNICAL
SPECIFICATION
colour
inside
Photovoltaic power systems – Reliability practices for operation
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.160 ISBN 978-2-8322-3877-6

Warning! Make sure that you obtained this publication from an authorized distributor.

® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 3 ----------------------
– 2 – IEC TS 63265:2022 © IEC 2022
CONTENTS

FOREWORD ........................................................................................................................... 3

INTRODUCTION ..................................................................................................................... 5

1 Scope .............................................................................................................................. 6

2 Normative references ...................................................................................................... 8

3 Terms, definitions and abbreviated terms ........................................................................ 9

3.1 Terms and definitions .............................................................................................. 9

3.2 Abbreviated terms ................................................................................................. 11

4 Interrelationship of reliability, availability and maintainability ......................................... 11

4.1 General ................................................................................................................. 11

4.2 Information model ................................................................................................. 11

4.3 Link to IEC TS 63019 ............................................................................................ 13

4.4 Benefits and justification for a robust reliability program ....................................... 14

5 Development phase of a PVPS project .......................................................................... 14

5.1 General ................................................................................................................. 14

5.2 Initial reliability program plan, design for reliability ................................................ 14

5.3 Critical items list ................................................................................................... 16

5.4 Preliminary failure modes and effects and criticality analysis and other fault

analyses ............................................................................................................... 17

5.5 High level reliability model .................................................................................... 18

6 EPC phase of a PVPS project ........................................................................................ 21

6.1 General ................................................................................................................. 21

6.2 EPC reliability program plan .................................................................................. 21

6.3 Update FMECA, FMEA, FTA, and risk minimization approaches ........................... 22

6.4 Detailed reliability model and Monte Carlo modelling ............................................ 22

6.5 Designed and specified FRACAS .......................................................................... 23

6.6 Preliminary O&M plan ........................................................................................... 24

6.7 PVPS design and specification .............................................................................. 24

6.8 Documentation and stakeholder guidance ............................................................. 25

7 O&M phase of a PVPS project ....................................................................................... 25

7.1 General ................................................................................................................. 25

7.2 O&M plan for reliability .......................................................................................... 25

7.3 Failure identification .............................................................................................. 27

7.4 Failure database ................................................................................................... 30

7.5 Root cause analysis .............................................................................................. 30

7.6 Repair/replacement database ............................................................................... 31

7.7 Pareto sorting and weak links identified ................................................................ 32

7.8 Reliability assessment .......................................................................................... 32

7.9 Life cycle costs (LCC) of reliability ........................................................................ 33

Bibliography .......................................................................................................................... 34

Figure 1 – Clipping time decline ............................................................................................ 14

Figure 2 – Example high level reliability block diagram ......................................................... 20

Table 1 – Information category overview for a PVPS ............................................................. 12

Table 2 – Failure incident data tracking ................................................................................ 27

Table 3 – Model report content ............................................................................................. 29

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IEC TS 63265:2022 © IEC 2022 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
PHOTOVOLTAIC POWER SYSTEMS –
RELIABILITY PRACTICES FOR OPERATION
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

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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 63265 has been prepared by IEC technical committee 82: Solar photovoltaic energy

systems. It is a Technical Specification.
The text of this Technical Specification is based on the following documents:
Draft Report on voting
82/1993/DTS 82/2039/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

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at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are

described in greater detail at www.iec.ch/publications.
---------------------- Page: 5 ----------------------
– 4 – IEC TS 63265:2022 © IEC 2022

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

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IEC TS 63265:2022 © IEC 2022 – 5 –
INTRODUCTION

Key objectives of this document are to inform users of reliability tools and assessment methods

(historic, predictive, and analytical) that can satisfy the stakeholders needs for dependable PV

Power System (PVPS) operation. Stakeholders will be able to use this information as a common

basis for reliability assessments, effective operation and maintenance (O&M) planning and

execution, reporting, communication of field data, and reliability metrics. Reliability feedback to

stakeholders is an objective to be further defined by the stakeholders themselves as individual

stakeholders will have differing needs for data and reporting. This document provides a

fundamental process for ensuring reliability needs can be understood and met. IEC TS 63019

addresses availability which is a higher-level metric that combines reliability and maintainability,

and it complements this document as a key normative standard. It should be used in

combination with this document.

Many of these tools and methods can be used to consider design alternatives or to support

design validation during the project phases. The ability to target critical components and

discrete O&M actions will have demonstrated value in practice. The characterisation of

components lifetimes is derived from real-time capability assessments, and historical records

of reliability metrics. Failure estimates used in design will be replaced with recorded data over

time. The overall application of reliability practices in this document is intended to be practical

and reduce the costs of failures.

Using a design for reliability (DfR) approach, normative requirements are identified for the

development, engineering, procurement, and construction (EPC), and (O&M) phases of PVPSs.

In this document, they are defined as tasks or work products. The concept of PV plant reliability

stretches into many different aspects of planning, modelling, operation, and maintenance. The

use of a methodical approach using reliability and system engineering tools to apply reliability

practices aid in different ways. By improving understanding of the reliability of critical and key

components, informed decisions can be made regarding the trade-offs between higher reliability

and system component costs, or increased maintenance with lower initial cost approaches.

Original equipment manufacturers (OEMs) are key reliability stakeholders and will receive

stakeholders’ specifications addressing reliability inputs as well as field failure information.

Clarity on intended function, definitions of failure, and how to implement reliability practices

through the phases of PV system design, component and subsystem specification, operation

and analyses are included.
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– 6 – IEC TS 63265:2022 © IEC 2022
PHOTOVOLTAIC POWER SYSTEMS –
RELIABILITY PRACTICES FOR OPERATION
1 Scope

This document outlines methods that can be utilized to ensure reliability throughout the PVPS

project phases. It is derived from a management motivation for long lasting and cost-effective

energy performance, energy production, secure production and revenue, and safe function. The

application of reliability practices in this document is designed to be practical and reduce the

costs of unreliability.

The reliability planning documents throughout the phases include purpose, scope, limitations,

schedule, reference documentation, tasks, and standards. The work products build on the

documentation concurrently with the PVPS concept, design, specifications, studies,

procurements, and hiring of services. They are consistent with the project implementation

scheduling, including financing, insurance, underwriting, or other decisions, specification,

design, operating or maintenance planning and activities.

It is a phased approach, as there are specific needs for actions by the defined phases, decision

process and stakeholders involved.

This document further identifies and defines a normative minimum set of processes and tools

to meet the requirements of this document. The phases are development, EPC, and O&M.

These phases may not be universally applied and different parties in industry may have different

nomenclature and organizing principles. It is recognized that some organizations may be

vertically organized with multiple capabilities. An owner’s engineer may also have a role. The

thrust here is that however organized, the reliability tools, practices, and methods are assigned

with needed data collected and preserved for relevant analytics as generally outlined in this

document. It includes as a minimum, the identified work products and deliverables in this

document identified specifically in Clauses 5, 6, and 7. Integrated reliability products are

identified in this document on a task by task progression phased throughout the project. While

these tasks are part of the minimum set of actions and deliverables, it is recognized that

additional specificity is required. The reliability program plans provide clarification (contractual

in many cases) on approaches through the various phases. The plans are approved by the

management and/or ownership at the beginning of the phases. The expert practitioners may

choose to seek approval for alternate approaches as “approved equals” as the reliability

program plans (RPP) are optimized, clarified, and submitted for approvals. It is also

acknowledged that commercial software can be a valuable and professional aid in

implementation of analyses and tracking data and the plans are where those practices can be

identified.

While this document identifies normative requirements for reliability of an operating PVPS, it

has functional definitions of the various tasks described above and below as the minimum set.

This document performs the role of a functional specification and serves as a structure and an

aid to data collection, design, and O&M decisions. It provides parent requirements for a

subordinate family of documents that will describe in detail the scope and contractual elements

for the design and O&M of the PVPS. The purpose is to drive improvement in the reliability of

PVPS project approaches.

Some of these work products and documents are kept up to date through the phases as major

decisions may necessitate. A historian system to keep, maintain data and analyses, and reports

is kept for ready access of documentation needs.

Reliability metrics cannot be derived without important failure information. Determining the

answers to common questions may require the PVPS operation to properly collect the requisite

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IEC TS 63265:2022 © IEC 2022 – 7 –

data, such as what equipment or portion of the plant is failing, how long, how often, and how

much these failures will cost in repair and lost energy production? Asset management questions

include the source of the outage (i.e., Whose clock is it on? Was the outage due to internal or

external forces? What power/energy was generated? What was expected?). Effective reliability

design integration should reduce overall system costs through reduction and/or mitigation of

failures and their consequences. There are initial costs associated with design analyses and

reviews, component selection, and analysis of reliability testing. Failure to perform reliability

practices in both design/specification and operations/maintenance results in a lower reliability

PVPS and resultant costs for field repairs and replacements, and the impact to energy

generation.

It is important to address the OEMs’ design role in the PVPS design. The scope of this document

is primarily focused on the total system from a perspective of the three defined phases. Within

the EPC phase falls the design and specification of components. Mitigation of the component

reliability risk falls on the builder/OEMs as well as the owner/operators. After the EPC

specifications, it is the OEM who designs, builds, and tests the components, considering the

physics, environments, chemistry, metallurgy, and other parameters needed for robust

operation, including specifications for materials and subcomponents. All aspects are considered

as a “systems engineering” process (Incose) and maintaining the supplier/customer interface

needs management in the warranty period and beyond in the following operations and

maintenance. It is anticipated that some major components may be selected early near the time

of financing the project. Failure assessments and reliability design integration of those

components are made prior to specification and procurement.

Reliability assessments performed during the development phase help to support common

probabilities of performance exceedance where confidence levels are often stated as P50 and

P90. These are statistical probability numbers often stated as 50 % or 90 % confidence. For

example, the P50 figure is the annual average (statistical) level of generation over a specified

interval, usually a year. The P90 figure is the confidence that the annual generation that is

predicted to be met or exceeded 90 % of the time, usually over a year.

These estimates are often directed toward the variability of the resource but the health and

condition of the PVPS is equally important. The general attention to reliability, probabilities,

statistics, and the process of “designing reliability in” is intended to bolster the important metrics

of energy production probabilities. The reliability approaches of this document should also help

to support the sale of the project and subsequent potential resales.

IEC TR 63292 was written as a precursor to this document and is informative with additional

descriptions on the role of individual reliability tools and techniques as well as the benefits of

those approaches.

While this document identifies reliability tools, topics, methods, and procedures, there are

commercial software products available to perform analyses for the mature discipline of

reliability analysis. There is no assessment of those tools or recommendations for one tool over

another in this document.

A word of caution. An obvious concern is that a defined reliability system appears imposing at

first sight. It is not the intention that the effort to have a greater cost than its benefits. The

resultant specifications and design fit the business/financial needs of the project. The cost of

ensuring reliability is weighed against the costs of not ensuring reliability at achievable levels

over the life of the system.

It is not within the scope of this document to determine the method of information acquisition.

IEC 61724-1 has pertinent requirements and IEC TS 61724-3:2016,6.2.5 specifically identifies

measured data. These standards differ on approach for different levels of system nature and

size, and it is recognized that applicability is most apparent for utility scale systems. However,

the reliability aspects have like applicability for systems of any size and are recommended for

appropriate use. The failures and impacts will be similar.
---------------------- Page: 9 ----------------------
– 8 – IEC TS 63265:2022 © IEC 2022

The types of data and data collection systems are assessed for what is key and what is not

while addressing the initial and future data requirements. The Pareto techniques later described

allow insights to be gained on the vital few as per an 80/20 rule, where 80 % of the problems

typically arise from 20 % of the components. Key data are collected for sorting by Pareto

principles, and this document provides references to other documents that address data

requirements.

Formulas in the referenced standards provide normative guidance for standardization.

Examples and guiding principles for developing methods for calculation and estimation of

reliability metrics, are subject to the knowledge and coordination for use by the involved

stakeholders. Reliability aspects are critical, and the ownership and management of the projects

define exactly the scope of what is to be done contractually and by whom.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes recommendations 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 60300-1:2014, Dependability management – Part 1: Guidance for management and
application

IEC 60300-3-3, Dependability management – Part 3-3: Application guide – Life cycle costing

IEC 60812, Failure modes and effects analysis (FMEA and FMECA)
IEC 61078, Reliability block diagrams
IEC 61649:2008, Weibull analysis

IEC 61703, Mathematical expressions for reliability, availability, maintainability, and

maintenance support terms
IEC 61724-1:2021, Photovoltaic system performance – Part 1: Monitoring

IEC TS 61724-3:2016, Photovoltaic system performance – Part 3: Energy evaluation method

IEC TS 61836, Solar photovoltaic energy systems – Terms, definitions, and symbols

IEC 62740, Root cause analysis (RCA)

IEC TS 63019:2019, Photovoltaic power systems (PVPS) – Information model for availability

IEC TR 63292, Photovoltaic power systems (PVPSs) – Roadmap for robust reliability

ISO/IEC Guide 98-3, Uncertainty of measurement – Part 3: Guide to the expression of

uncertainty in measurement (GUM:1995) – Supplement 1: Propagation of distributions using a

Monte Carlo method

IEEE 762-2006: IEEE Standard Definitions for Use in Reporting Electric Generating Unit

Reliability, Availability, and Productivity
---------------------- Page: 10 ----------------------
IEC TS 63265:2022 © IEC 2022 – 9 –
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions

For the purposes of this document, the terms and definitions given in IEC TS 61836 and the

following 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
3.1.1
availability

ability of an item to be in a state to perform a required function under given conditions at a given

instant of time or over a given time interval, assuming that the required external resources are

provided
3.1.2
available state

where the PVPS, a subsystem, or a component is capable of providing service, regardless of

whether it is actually in service and regardless of the capacity level that can be provided

3.1.3
confidence level

probability that the value of a parameter falls within a specified range of values

3.1.4
dependability

measure of the degree to which an item is operable and capable of performing its required

function at any (random) time during a specified mission profile, given that the item is available

at mission start
3.1.5
derating

using an item in such a way that applied stresses are below rated values or lowering of the

rating of an item in one stress field to allow an increase in another stress field

3.1.6
failure

event or inoperable condition in which a PVPS, a subsystem, or a component did not, or could

not, perform as intended when required
3.1.7
forced outage
damage, fault, failure or alarm that has disabled a system or component
3.1.8
failure reporting and corrective action system
FRACAS

closed loop experience process used to improve dependability of current and future designs by

feedback of testing, modification, and use
3.1.9
incident

event or inoperable condition in which a PVPS, a subsystem, or a component did not, or could

not, perform as intended, or was prevented from operation due to external constraints

---------------------- Page: 11 ----------------------
– 10 – IEC TS 63265:2022 © IEC 2022
3.1.10
lowest level of repair

lowest level of item (component, assembly, module, card, box, or subsystem) that is repaired

or replaced as the result of failure of the end item
3.1.11
maintenance action

element of a maintenance event. One or more tasks (i.e., fault localization, fault isolation,

servic
...

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