Creating a Power Acquisition Network with LabVIEW
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Author(s):
Petr Bilik - VSB TU Ostrava/ELCOM
Industry:
Energy/Power
Products:
PXI/CompactPCI, Signal Conditioning, Data Acquisition, Real-Time Module, Lookout, LabWindows/CVI, LabVIEW
The Challenge:
Developing an independent network of power quality analyzers and a network server configuration tool to send data to other interfaces and store it in a Power Quality Data Interchange Format (PQDIF) database.
The Solution:
Creating the Power Acquisition Network (PAQ Net) Explorer (PAX) software application using NI LabVIEW for configuring measurement nodes (PAQ Nodes) via the instrument driver of a selected analyzer.
"Using NI RT Series data acquisition (DAQ) and PXI devices compatible with the LabVIEW graphical development environment helped us run the PAQ Nod Elcom on independent hardware using a real-time operating system."
Power distribution companies receive many requests to monitor power quality in different distribution points and use many instruments from different vendors. To keep all measured parameters in one location independent of the instrument type or topology of communication network, we developed the Power Acquisition Network (PAQ Net).
PAQ Net
We based PAQ Net on independent power quality analyzers called PAQ Nodes. Users can connect to these nodes from anywhere in the world through Internet or an intranet connection. To add power analyzers from any vendor to PAQ Net, the instrument must have an instrument driver and an Ethernet or modem connection to the Internet. Users can add any power analyzer that meets these conditions to PAQ Net with PAQ Net Explorer (PAX). The PAQ Net server of each node provides measured parameters in many ways: Dynamic Data Exchange (DDE) for Supervisory Control and Data Acquisition (SCADA)/human machine interface (HMI), PQDIF for saving data to PQDIF data files or database, ASCII for saving data to ASCII files, and Structured Query Language (SQL) for saving data to the Microsoft SQL Server.
In addition, PAQ Net provides data in many formats and is open to other data interfaces such as OPC. For every PAQ Node in the system, the server runs in parallel, even when other connected nodes take measurements. PAQ Net retrieves information about aliases, IP addresses, and other properties of properly configured PAQ Nodes from configuration files, which PAX generates. This network can integrate with other types of instruments and measurement units to measure physical quantities and display them at one central point.
PAX – PAQ Net Explorer
Users can configure the PAQ Nodes with PAX, which helps them choose the proper alias of the node, IP address, averaging interval, connection scheme, and ranges. PAX uses an instrument driver to communicate with a specific node and users can insert new nodes or change the configuration of existing nodes with a simple step-by-step wizard.
To add a new node, the user specifies the type of node to use the proper driver and the alias of the node to identify the node on the server side. Then the user defines the IP address of the node and averaging interval and configures the instrument connection and ranges.
After inserting or changing any of the nodes, PAQ Net restarts with new configurations. A green check mark or a red cross in the PAX list of nodes indicates the connection status of the node, PAQ Net delivers this information to PAX, and the right side of the panel lists the preset parameters of the selected node.
Using the PAQ Net DDE Server in Lookout
The PAQ Net server can interface data using DDE, and because DDE is a common data exchange standard, PAQ Net can provide data to many environments, applications, and programming languages supporting the standard.
The Lookout application is a testing application from the electrical drives laboratory. The application visualizes the measured values in Lookout and stores them as ASCII data files, all driven by PAQ Net. We use two Elcom PQA01 analyzers as the PAQ Nodes.
PAQ Node Elcom PQA01
The PAQ Node Elcom PQA01 is a scalable, remotely controlled, and displayless PC-based power analyzer. We use the device as a stand-alone instrument, but it serves as a base software element for a user-defined power analyzer or distributed system. Remote commands make all setups and data readouts possible. Our VISA PnP drivers written in NI LabWindows™/CVI and LabVIEW correspond with the PQA01 analyzer. The PC platform inherently provides important interfaces for remote control of the instrument by Ethernet or modem connection. Five instruments – a fast Fourier transform (FFT) analyzer, power flow monitor, EN50160 voltage monitor, transient recorder, and symmetrical components analyzer of a three-phase system – can capture data and perform processing in parallel. Instead of storing data as files on a local hard disk, the system uses the concept of circular data buffer, similar to the asynchronous data acquisition process. The system presets an averaging interval for all analyzed values before the start of the measurement. At the end of each averaging interval, measured values write to the circular buffer and the user can select the buffer length. Through the remote commands, users can read required scans from the buffer and scan the backlog value. With data buffering, the system can handle interruptions in connection with the supervising system.
Hardware Platforms for the PAQ Node Elcom PQA01
We implemented the analyzer on the PXI hardware platform. The PXI chassis includes an NI PXI-8175 controller and an NI PXI-6052E 16-bit DAQ module. The NI SCXI-1120D module, equipped with antialiasing filters, provides signal conditioning. To extend the input range of the SCXI module, we used the NI TBX-1316 high-voltage terminal block. This configuration delivers connection of up to a 1,000 VDC/680 Vrms maximum working voltage. The data acquisition process of instrument software uses sampling frequency 9.6 kS/s per channel. Generally, users can implement the developed application on other platforms based on a PC, data acquisition board, and a signal conditioning board.
Developments for the Future
We want to extend the set of available instruments for use with the PAQ Net system by focusing our R&D efforts on developing a distributed system for monitoring electrical quality and power parameters based on the PQA01 analyzer. Our R&D team is developing devices for using Microsoft Internet Explorer as the only tool for full remote setup of distributed PQA01 analyzers.
By using NI RT Series DAQ and PXI devices along with the LabVIEW graphical development environment, we can run the PAQ Node Elcom on independent hardware using a real-time operating system so that only the supervising system runs on a standard PC, taking full advantage of the graphical Windows OS features.
The mark LabWindows is used under a license from Microsoft Corporation. Windows is a registered trademark of Microsoft Corporation in the United States and other countries.
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