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Original Authors: Daniel Kaminský, ELCOM, a.s.
Edited by Cyth Systems
Why Are Power Quality Measurements Important?
Monitoring power quality identifies potential problems before they are big enough to create damage that all too often comes with serious financial losses. Industry-standard prevention options are now relatively cheap and range from simple best-practice-design-considerations to global monitoring and control equipment installations.
What Has to Be Measured?
A typical power quality analyzer analyses 3 voltages of a power network to calculate voltage quality defined in international standards. Voltage quality is described by frequency, voltage level variation, three-phase system unbalance, distortion, and voltage leveling. In some cases, it is necessary to analyze the current signals along with the voltages. This requires analyzing current parameters and calculating indirect quantities like active power, reactive power, energies, and other quantities.
We chose to implement our system on the NI CompactRIO platform with C Series modules. Compared to PC-based systems cRIO offers a more compact and rugged built chassis, better temperature specifications and lower power consumption. From the variety of I/O modules, we used the NI 9225 300V power measurement module for performing high-voltage measurements. The module is designed for measurements, such as line-to-neutral as well as line-to-line measurements of 110V power grids and line-to-neutral measurements of 240V power grids. For current measurements, we use NI 9227. The NI 9225 and NI 9227 have simultaneously sampled channels at 50 kS/s for accurate three-phase power metering and power quality measurements such as flicker, harmonics, and power factor. Alternatively, we have designed voltage and current modules: EL9215U-R1 and EL9215I-R1 that are based on the NI 9215 module to use for our signal conditioning electronics. These are embedded in the free slots of a CompactRIO chassis.
The system, deployed in transformers, uses NI CompactRIO to calculate power quality parameters.
The CompactRIO-based Power Quality Analyzer
The model name that we present here is ENA-450, but due to the scalability of the NI CompactRIO family and the portability of the LabVIEW code, we were able to implement the system in different form factors to accommodate various different applications and customer-specific needs. Besides the implementations based upon the fully flexible NI CompactRIO system (ENA450.EC), we have created turnkey solutions where we have deployed our application to:
Integrated CompactRIO systems that combine a real-time processor and a reconfigurable field-programmable gate array (FPGA) within the same chassis (ENA450.EB, ENA450.NB)
NI Single-Board RIO systems that integrate the three core components of an NI CompactRIO system - real-time processor, field-programmable gate array (FPGA), and I/O - on a single printed circuit board (ENA460).
The main advantage of the described power quality monitoring system is its high performance, flexibility, and small size. Using the C-Series modules with built-in signal conditioning, and implementing the powerful and user-friendly solution, dramatically simplifies the software maintenance and further development without impact on the current solution. In case of any updates or changes to the standards, the instrument features can be updated quickly, and the system stays up to date. Due to the open solution, the existing system can be easily integrated with other systems, as the communication protocols can be adjusted in accordance with customer needs or integration into existing SCADA systems. The open hardware architecture makes it possible to add a new DIO for monitoring and controlling as well as modules for wireless communication via GPS or GSM.
Daniel Kaminský, ELCOM, a.s.
Edited by Cyth Systems