Measurement WG – Review of Standards for Small Wind Turbine Measurements and User Surveys
Measurement standards document the professional principles and practices the interested stakeholder parties (policy makers, manufacturers, practitioners, end-users etc.) are required to adhere to and the level of quality and effort expected in all measurement activities. Standards have accompanying guidelines that present recommended best practices to fulfill the goals of the standards. While currently a plethora of measurement standards, as well as guidelines regarding testing and measuring AC sources are available, most of them mainly focus on measurements on the utility grids (i.e IEC 62053, IEC 61039).
The lack of a coherent set of documentation regarding off-grid applications in the context of data collection and high quality measurements, raises a challenging task, especially taking into account the particularities involved in small wind turbine applications, (i.e. the range of frequency varies from the standard frequency, 50Hz or 60Hz, and the current THD is as high as 40%).
This report, which is the outcome of the ongoing Wind Empowerment Network Measurement Working Group research activities, focuses on providing details on the principles and methods employed in the collection, storage and analysis of data measurements, thus providing guidelines based on existing standards and facilitating the progress towards future standardization activities. In this context, it further facilitates the establishment of an enabling environment for a rapid uptake of renewable energy technologies, by contributing to the development of the necessary quality infrastructure framework for small wind turbine applications with respect to the data measurement methods and resulting activities.
Data measurement methodologies and activities require the complete information flow, (from the setup of the installation site and the wind cup installation specifications, to the data harvesting interval and the current/voltage transducers specifications) to be accurate and adhere to the respective standards in order to provide a complete, reliable and consistent set of data to be exploited in a commonly accepted and reproducible way. In this report, significant effort has been made to maintain the above mentioned structure that will ensure every part of the data information flow will be accounted for and evaluated.
This document incorporates the review results of the following standards:
- IEC 61400-12-1:2005 – Power performance measurements of electricity producing wind turbines
The purpose of IEC 61400-12.1 is to provide a uniform methodology that will ensure consistency, accuracy and reproducibility in the measurement and analysis of power performance of wind turbines and provides guidance in the measurement, analysis, and reporting of power performance testing for wind turbines of all types and sizes when connected to either the electric power network or a battery bank.
- IEC 60688:2013 – Electrical measuring transducers for converting AC and DC electrical quantities to analogue or digital signals
This International Standard is intended to specify the terminology and definitions relating to transducers whose main application is in electrical power engineering, especially for the purposes of process control and telemetry systems. This chapter is not an integrated report of the standard, but aims to unify the test methods used in evaluating transducer performance and to specify accuracy limits and output values for transducers.
- IEC 60044:2003 – Instrument Transformers
These parts of IEC 60044 apply to new inductive voltage transformers and current transformers for use with electrical measuring instruments and electrical protective devices at frequencies from 15 Hz to 100 Hz.
- IEC 61400-25 – Communications for monitoring and control of wind power plants
The focus of the IEC 61400-25 series is on the communications between wind power plant components such as wind turbines and actors such as SCADA Systems. Internal communication within wind power plant components is beyond the scope of the IEC 61400-25 series. The IEC 61400-25 series addresses vendors (manufacturers, suppliers), operators, owners, planners, and designers of wind power plants as well as system integrators and utility companies operating in the wind energy market. The IEC 61400-25 series is intended to be accepted and to be used worldwide as the international standard for communications in the domain of wind power plants. The wind power plant specific information describes the crucial and common process and configuration information.
- IEC 61400-25-2 – Communications for monitoring and control of wind power plants – Information models
IEC 61400-25-2 specifies the information model of devices and functions related to wind power plant applications. In particular, it specifies the compatible logical node names, and data names for communication between wind power plant components. This includes the relationship between logical devices, logical nodes and data. The names defined in the IEC 61400-25 series are used to build the hierarchical object references applied for communicating with components in wind power plants.
- IEC 61400-25-3 – Communications for monitoring and control of wind power plants – Information exchange models
This part of IEC 61400-25 provides the information exchange models that can be applied by a client and a server to access the content and structure of the wind power plant information model defined in IEC 61400-25-2. Also, gives an overview of the information exchange models for operational functions and management functions.
One of the main concerns of the Measurement Working Group as expressed in the Athens 2014 conference and later was that while all of WE projects include measurement activities (from current/voltage levels to environmental parameters, i.e. wind speed/direction, humidity) and remarkable efforts have already resulted in robust, reliable low – cost loggers, which facilitate and validate the organization’s activities, not much work has been done towards the specifications of the data loggers employed. It would prove really helpful if input could be gathered from all the participants of this survey, regarding the data needed to be measured and stored, the specifications of the majority of the applications, the type of the environmental parameters that need to be measured, in a few words specify what we really need to measure in a typical small wind turbine application.
Therefore, this online survey, conducted by the Measurement Working Group of WE, aims at better understanding attitudes, practices and technology choices across the community’s various implementations, regarding the measurement procedure and respective techniques on SWT applications. It analyzes respondents who completed or updated the survey during a five-week window in October and November of 2016 and represents a snapshot of 35 users, constructors and designers of SWT and data loggers, who participated voluntarily.
A lot of prior design was necessary and many drafts had to be processed, in order to address the contextual and notional issues encountered, as well as to minimise the subjective factor inevitably present in structure, language, even grammar of the questions.
All results are statistically analysed and graphically presented to enable easy and appealing, yet direct and complete access to the results and the respective information.
In order for the survey to provide a holistic overview of its subject, it is divided in 4 main sectors:
- Participants profile, that includes general information regarding the participants and their involvement to small wind turbines applications.
- Current practices, intended to investigate the current practices that participants follow, regarding the installation of small wind turbines as well as the specification of data loggers. The questions are divided into two main subcategories, one concerning the SWT and the other regarding data loggers present in SWT installations.
- Practicality of measurements, which is intended to gather information regarding the way the participants perceive the usefulness of measurements.
- Failure and maintenance, which is intended to gather information regarding the most common data logger failures and the respective maintenance services, as well as the possible relations between the measured quantities and the fault recognition information that they may provide.
Each section has its respective subsections, aiming to highlight the subtle differentiations within each section that came up at the design of the survey, resulting in concrete sets of answers, thus providing information with minimum notional overlapping, repetition or vagueness.
This effort intends to provide feedback to the broader community, and to provide Wind Empowerment network with better data to make decisions regarding the roadmap and feature enhancements.