Small-scale wind turbine certification with imc systems

Wind of Change

Directtech has reinvented the wheel with their new Windtracker. To be more precise: the wind wheel. The large, rotating “wheel” was replaced by a newer technology. Unlike the large turbines with their often giant rotor blades that move like a propeller, the Directtech Windtracker has vertical blades that rotate like a gyro in the wind and thus generate electricity.

The new Windtracker wind turbine is 20 meters high and has a nominal output of 10 kilowatts. The Windtracker not only eliminates the shadowing-effect, but the vertical turbine is almost completely silent and very compact. Thus, the new small-scale turbines can be installed in areas where larger turbines can't: e.g., in residential areas, in commercial parks, at charging stations for electric cars or on narrow street medians. They also provide a clean form of electricity generation for private customers – depending on the location, the Windtracker can generate enough electricity for two to six households.

Vertical wind turbine Windtracker, © Photo Directtech

Tested according to IEC 61400
The world's first IEC 61400 certificate for a vertical wind turbine has recently been awarded by TÜV Rheinland to Directtech GmbH.

As part of the certification of the Windtracker turbine, all relevant safety requirements and loads on the wind turbine were tested. The verification and data analysis of the field measurements were carried out by the accredited company Windtest Grevenbroich. For performing the measurement tasks within the scope of small-scale wind turbine certification, Windtest used measurement systems from imc Meßsysteme GmbH.

The meteorological data (temperatures, atmospheric pressures, etc.), mechanical loads (strain gauges), as well as current quality and sound emissions, were measured in long-term tests. The results are important for certification – as proof that the wind turbine meets the quality requirements for the market.

Robust, distributable and fail-safe: imc CRONOSflex

The core of the measurement data acquisition for the certification tests is the modularly expandable imc CRONOSflex measurement system. It consists of the CRFX-2000 base unit and can be easily expanded with additional measurement amplifier modules. The base unit allows for an aggregate sampling rate of up to 2000 kSamples/s.

In addition, the base unit offers:

• Integrated real-time analysis and control functionality with imc Online FAMOS
• TCP/IP Ethernet interface for the connection of a PC
• Built-in flash memory and optional hard drive
• Connection possibility for GPS (time and position information)
• Self-starting and data backup function in case of power failure

Main cabinet with imc CRONOSflex base unit with measurement modules and imc CANSAS

Measurement modules

The imc CRONOSflex-series offers a wide range of amplifier types with up to 100 kS/s per channel, integrated signal conditioning and sensor supply. The system supports almost every sensor. Whether analog signals, incremental encoders, digital process variables or data from fieldbus systems such as CAN, CAN FD, PROFIBUS, PROFINET – all are acquired synchronously by the imc CRONOSflex.

And thanks to the robust design, the measurement systems ensure precise results even under difficult ambient conditions with high temperature fluctuations.

Cabinet with measurement modules from imc

The ISO2-8 and HV-4U modules were chosen especially for the certification measurement.

The ISO2-8 is an isolated differential measurement amplifier with eight electrically isolated, potential-free channels for the highly accurate measurement of:

• Voltage and current (20 mA)
• Temperatures (thermocouples and PT100)
• IEPE/ICP sensors (using an optional DSUB extension plug)
  
• Amplifier module ISO2-8 

Special features of the ISO2-8 amplifier:

• Channel-isolated, galvanically separated inputs
• Wide, fine-adjustable input voltage range (from ± 50 mV to ± 60 V)
• High signal bandwidth up to 11 kHz
• Each channel with its own adjustable filter (e.g., anti-aliasing filter) and simultaneous A/D converter
• Supports imc Plug & Measure (Transducer Electronic Data Sheets, IEEE 1451)

With the four-channel HV-4U measurement amplifier, high voltages up to 1000 V can be acquired.

Amplifier module HV-4U 

Special features of the HV-4U amplifier:

• Detection of voltages up to: 600 V_eff CAT III and 1000 V_eff CAT II
• 48 kHz analog bandwidth (-3 dB)
• Phase accuracy better than 1° for measurements up to the 50^th harmonic at 50/60 Hz mains voltage
• Input ranges from ± 1000 V to 2.5 V, selectable per channel

imc CANSAS modules in operation

For the measurements in the tower, imc CANSAS modules were used. The data collected by these systems were sent via CAN bus to the base unit at a secondary location. The complete measurement was monitored by a computer in the main building.

imc CANSAS L-CI8

The imc CANSAS-CI8 CAN-measurement module is an isolated differential measurement amplifier, which acquires 8 channels of analog physical measurement variables:

• Voltage
• Current (20 mA sensors)
• Thermocouples
• PT100 (optional PT1000) temperature sensors
• Resistance

Special features

• Isolated channels allow measurements in environments where the potential conditions are not properly defined
• Measurement of signals on high electrical common-mode potential
• 440 Hz bandwidth at max. 1 kSps/channel sampling rate
• Measurement ranges and sampling rates can be individually selected (in 1, 2, 5 steps)
• 16-bit resolution (with internal 24-bit processing)
• Supports imc Plug & Measure TEDS (Transducer Electronic Data Sheets, IEEE 1451.4)

Measurement data analysis and evaluation with imc FAMOS
For the visualization, evaluation and documentation of the measurement data, Windtest used the proven imc FAMOS data analysis software.

In this case, both the meteorological data, such as wind speed, wind direction and air pressure, as well as the performance data of the turbine and its accompanied loads were examined.

Example representation of meteorological data such as wind speed and air pressure

Example representation of electrical power

Finally, Windtest compiled a comprehensive test report for the customer Directtech, which documented the results of the stress and durability tests of the wind turbine.

Example load data evaluation

The combination of simple operations and powerful functions ensured productivity throughout the evaluation process. For example:

• Quickly calculate large amounts of data: 64-bit technology
• Visualization at the push of a button
• Comprehensive analysis functions
• Multi-page report generation
• Multi-layered macro creation
• Project management

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