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 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.

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.