Development Of Multi-Channel Portable Power Quality Monitoring Devices Based On PQDIF Data Format

Multi-channel portable power quality monitoring devices can carry easily and operate simply. It also can monitor flexibly and easily at any time, when it can not be installed online. It can choose special function to monitor and analysis the electricity load of different property and working conditions, and have full functions of online power quality monitoring devices. The most basic function of power quality monitoring network is to realize the data exchange between monitoring terminal (device) and monitoring system. However, so far, there is a prominent problem in the data exchange between the terminal and the system, which is no uniform communication protocol. PQDIF is a universal power quality data specified in IEEE 1159, which can be used as the standard format for data exchange between heterogeneous systems, generally. Therefore, it is very important to develop the multi-channel portable power quality monitoring device based on PQDIF format.Multi-channel portable power quality monitoring devices based on PQDIF format can be divided into three parts:Hardware design of multi-channel portable power quality monitoring device, Design and develop of power quality monitoring software, accomplish PQDIF in power quality monitoring system.Hardware platform of power quality monitoring deviceis are established by signal acquisition sensor, signal conditioning circuit, data acquisition module, and data processing in this paper. The voltage signals of voltage transformer in the substation is reduced 1/100 times of the secondary side by the voltage probe. The current signal of the secondary side of the current transformer is the small voltage signal through the current clamp mutual inductor. Two small voltage signals through signals isolating, linear transforming and signals conditioning, received by the data acquisition module. Small voltage signals, low pass filter, voltage followe, ADC analog digital converter, and memory SRAM, are accomplished by data acquisition module. An adaptive frequency tracking can solve spectral leakage at entire cycle time of sampling, in the data acquisition module. Besides, We calculate half-wave RMS of sampling data, as transient fault events recorded wave initiation criterion of measured values, saving the memory of software processing for running data, and improving working efficiency of the multi-channel portable power quality monitoring device, in the data acquisition module.In this paper, DFT is used to analysis power quality data. Creating eight multi-threads, for example data-switching thread, transient event record thread, flicker-calculating thread, real-time waveform-displaying thread, FFT data-updating thread, harmonic data-writing thread, and RMS/power data-writing thread, solve the problem of parallel tasks. Monitoring software includes voltage, current, power and power factor of three-phase imbalance degree, flicker and other basic electrical parameters measurement, harmonic measurement, and the transient event log, trend records, data statistics, waveform recording module.According to the characteristics of the power quality data, physical and logical structure of PQDIF, this paper builds a process framework for four custom data convert to PQDIF file format, including harmonic data file, power data file, valid value data file and flicker data file. In LabWindows/CVI platform, calling the COM components by ActiveX control to obtain the PQDIF library file. Using the new object, open the object, activate the object, get and set the MW flag and other functions in the library, which accomplishing multi-channel portable power quality monitoring device to store PQDIF data.