A Modified Algorithm for Harmonics and Interharmonics Measurement

This paper proposes a low cost three-phase power quality meter. Due to its characteristics, the meter can be applied for residential or small businesses use. The proposed device uses the power definitions from IEEE Standard 1459-2010. Moreover, it calculates the true rms value, the individual harmonics, and the voltage unbalanced factor. In order to validate the power quality meter, simulations and experimental results are presented. The results are presented on a web page that can be accessed by any device with internet access.

O objetivo deste trabalho é apresentar uma nova metodologia para estimar a distorção harmônica em um sistema elétrico, a partir de medições em locais específicos. O algoritmo desenvolvido se baseia em Estratégias Evolutivas. Esta técnica compreende um ramo de desenvolvimento dos Algoritmos Evolutivos, no qual se inserem os Algoritmos Genéticos. As vantagens no uso desta técnica residem nas facilidades de modelagem e em encontrar uma solução para problemas complexos. A maioria das técnicas encontradas na literatura para solução deste problema utiliza sincronização das medições por meio de métodos de alta tecnologia como GPS. O algoritmo proposto visa sincronizar os dados de forma offline por meio das informações do fluxo de carga para a freqüência fundamental, o que o torna muito mais econômico para compor um sistema de monitoramento de qualidade de energia. O algoritmo foi aplicado em uma rede de teste cujos dados foram extraídos do IEEE.

The paper introduces a concept for integration of substation IED data, primarily coming from digital protective relays (DPRs) and digital fault recorders (DFRs). Modern substations are equipped with different types of IEDs. DFRs are traditionally used to capture data from various events and disturbances in the power system that may need to be analyzed. Most of the modern IEDs such as digital relays, power quality meters, and sequence of event recorders can offer data recording function that is quite similar to that of DFRs. In some recent substation designs there are cases where DFR function is replaced by an equivalent function provided by DPRs. There are also cases when both DFRs and DPRs are used and configured to record the same events. In this case records from DPRs are used as a redundant source for event analysis. The paper addresses main requirements for integration of substation data: communication and automated IED data retrieval, unifying event data file formats, verification of event data content, and proper handling of the system configuration parameters. Examples of substation data integration using the proposed concept are discussed through expansion of an existing DFR data integration and analysis system and through introduction of data coming from different substation IEDs. Digital simulator was used to evaluate the concept in the example with multiple IED types

The need for small-scale renewable energy generation is predicted to increase. Distributed energy production, in general, can be more profitable due to the cost of distribution and use of energy storage, especially from the microgrid. However, the utility and consumers face difficulties maintaining demand imbalance, frequent load-shedding, and a drop in power quality. To address this issue, a portable power quality meter and protection based on the Internet of Things (IoT) for low-voltage distribution are proposed. The proposed prototype has several advantages. First, the procedure for implementing a portable IoT-based power meter with power quality and protection features for residential networks. Compared to other devices, this type has the advantages of power quality measurement, such as power factor, frequency, and harmonics. Second, an approach is proposed device with a parallel function in maintaining network security and quality. This increases the advantage of monitoring loads connected to the grid. Third, perform IoT power monitoring devices that provide notifications in real-time. Fourth, an experiment using a power meter on a microgrid connected to renewable energy combines a LiFePO4 battery and methanol to get the maximum benefit from green energy. The test results found that the IoT model can work reliably, where access to monitoring can be done via the website. The smart meter consists of a voltage transformer, current transformer, and microcontroller unit with an embedded communication module. The existence of more affordable monitoring and protection tools can increase the user’s opportunity to gain profitability.

The interest for solar Photovoltaic (PV) systems installation has been recently increasing due to their reducing cost and high electricity price from the utilities. However, the PV power generation is sensitive to variable solar irradiation, which causes technical difficulties related to power quality and control. Severity of those problems directly depends on PV penetration level, grid design and geographic location. This paper explores the flicker indices of grid-tied PV power plant, one of the major power quality issues. The study has been carried out on a real grid-integrated PV system, situated at Engineering Center, Florida International University (FIU). The field measurements of various solar output power and flicker quantifying indices at the point of common coupling (PCC) have been recorded using data acquisition system and power quality meter respectively. The collected data has been categorized and analyzed for voltage fluctuations and flicker. Different approaches have been done to investigate the influence of PV power plant on the flicker indices. Results show that solar output power has a marginal effect towards flicker indices with existing penetration level. Load connection and variation are the key indicators of high flicker value during observation time.

This project was motivated by the fundamental match between hotel space conditioning load response capability and power system contingency response needs. As power system costs rise and capacity is strained demand response can provide a significant system reliability benefit at a potentially attractive cost. At ORNL s suggestion, Digital Solutions Inc. adapted its hotel air conditioning control technology to supply power system spinning reserve. This energy saving technology is primarily designed to provide the hotel operator with the ability to control individual room temperature set-points based upon occupancy (25% to 50% energy savings based on an earlier study [Kirby and Ally, 2002]). DSI added instantaneous local load shedding capability in response to power system frequency and centrally dispatched load shedding capability in response to power system operator command. The 162 room Music Road Hotel in Pigeon Forge Tennessee agreed to host the spinning reserve test. The Tennessee Valley Authority supplied real-time metering equipment in the form of an internet connected Dranetz-BMI power quality meter and monitoring expertise to record total hotel load during both normal operations and test results. The Sevier County Electric System installed the metering. Preliminary testing showed that hotel load can be curtailed by 22% to 37% depending on the outdoor temperature and the time of day. These results are prior to implementing control over the common area air conditioning loads. Testing was also not at times of highest system or hotel loading. Full response occurred in 12 to 60 seconds from when the system operator s command to shed load was issued. The load drop was very rapid, essentially as fast as the 2 second metering could detect, with all units responding essentially simultaneously. Load restoration was ramped back in over several minutes. The restoration ramp can be adjusted to the power system needs. Frequency response testing was not completed. Initial testing showed that the units respond very quickly. Problems with local power quality generated false low frequency signals which required testing to be stopped. This should not be a problem in actual operation since the frequency trip points will be staggered to generate a droop curve which mimics generator governor response. The actual trip frequencies will also be low enough to avoid power quality problems. The actual trip frequencies are too low to generate test events with sufficient regularity to complete testing in a reasonable amount of time. Frequency response testing will resume once the local power quality problem is fully understood and reasonable test frequency settings can be determined. Overall the preliminary testing was extremely successful. The hotel response capability matches the power system reliability need, being faster than generation response and inherently available when the power system is under the most stress (times of high system and hotel load). Periodic testing is scheduled throughout the winter and spring to characterize hotel response capability under a full range of conditions. More extensive testing will resume when summer outdoor temperatures are again high enough to fully test hotel response.

The recommended power quality (PQ) indices in electric power systems are defined based on the discrete Fourier transform (DFT). DFT is mostly evaluated applying fast Fourier transform (FFT) algorithm which requires signals to be periodic in nature. Hence, it evaluates PQ indices accurately for stationary PQ disturbances only. However, in case of nonstationary PQ disturbances signal is aperiodic and FFT results in erroneous assessment due to spectral leakage phenomena. Furthermore, FFT cannot provide time information of the PQ indices as computation is performed in frequency domain only. Which is significant shortcoming of the FFT when dealing with time-varying PQ disturbances to extract dynamic signature of the signal. Thereby, this paper presents a framework of redefining PQ indices for stationary and nonstationary PQ disturbances employing time-frequency distribution (TFD) method. Among all TFDs, reduced interference distribution (RID) represents the most suitable properties for analyzing time-varying PQ disturbances. Hence, in this work, it is employed to reformulate PQ indices typically used in electric power systems. The results of two synthetic examples considering stationary and nonstationary PQ disturbances imply that the RID-based redefined PQ indices are closer to the actual values. Also, they provide more accurate results than the existing transient PQ indices and traditional FFT-based method.

The Internet of Things (IoT) has progressed to the point where it is now providing actual commercial value to industrial clients. As a result, people are naturally beginning to wonder about the influence of IoT on the well-established area of PLC programming. When it comes to integrating PLCs with IoT technologies, there are a variety of choices available, all of which have the same goal: to effectively merge the hard real-time guarantees and robust form factor of PLCs with the remote monitoring, alerting, and sophisticated data analytics of the IoT. Implementing good asset quality and demand management perceptions necessitates a basic consideration of processes and the loads that are controlled or reduced, as well as a consideration of utility pricing, auditing, and measurement. A redesigned intelligent monitoring and controlling system with capacity to modify data at high rates utilizing Profibus technology, as well as a new generation of digital meters, were also presented in the research. The proposed upgraded system features a completely automated demand monitoring/load shedding approach. In addition, the control module's power quality meters and software may be utilized to test and assess power quality. This is a PLC SCADA application that was made. There are now six buttons: three for controlling the tube lights and three for controlling the fans. The four LEDs at the bottom display the output status and are based on the Fatek PLC FBS-14; the ladder logic has been created using WinProLadder.

This paper aims to provide an insight into the measured background changes of harmonics due to operational changes in a typical Dutch transmission grid. Multiple use cases on different locations throughout a meshed 150kV grid have been considered. The nodes that were studied had measured exceedances of planning levels or were indicated to be critical for the future in earlier studies. This study provides an insight into the measured response of harmonics with respect to different operational changes such as specific scheduled outages that occurred and the impact of capacitor banks. Per use-case, individual conclusions are reported. The analysis was conducted on data of power quality meters (PQM) and various other data sources provided by the Dutch TSO TenneT. Data-processing, visualization, and computations were performed using Python. These results are useful for model validation, planning purposes, and maintaining power quality.

Detecting abnormal signals of electric power equipment in the incipient stage is a crucial task for maintaining a reliable supply of power. Early failures or incipient faults can be manifested in power signals with different types of power quality disturbance. Incipient faults may repeatedly occur until it becomes a permanent failure. If an electric utility is able to detect the incipient fault before actual damages occur, one can prevent the power system from outages and unnecessary economic losses. To accurately detect and classify incipient faults of five commonly seen power equipment in the high-voltage substation, this paper proposes a multiple anomaly detection scheme using a random forest algorithm to filter out irrelevant waveforms among the recorded waveforms from power quality meters and compare the detection performance with the other three machine learning algorithms. Results show that random forest has superior performance s to the compared methods in incipient fault classification accuracy.

In this paper, a new index is proposed in order to track and find the location of switched capacitor banks in distribution systems. The method is based on branch current changes immediately after the switching instant. The hypothesis states that branch current, measured by Power Quality Meter (PQM), is increasing for monitoring location at line and branches which feed the capacitor bank and is decreasing for monitoring location at other branches of the systems. Comparing the index calculated for each branch, it is possible to track and find the location of switched capacitor banks. The method is valid for both wye and delta configured capacitor banks. The size of the switched capacitor banks has no effect on method accuracy. The efficacy of the proposed technique is demonstrated using simulation results on the IEEE 13-bus distribution system. Results show that the new method is accurate and applicable in real distribution systems.

This article presents a methodology for detection of high impedance faults (HIF). HIF occurs when e.g. a cable makes contact with objects of high electric resistance, resulting in a nonsignificant increase in current. Such faults cannot be detected by traditional protection devices that operate due to overcurrent. The developed methodology is based on making use of variables from a power quality meter (PQM), such as harmonic and sequence components of the currents measured at a substation. Such variables compose descriptors for decision making in artificial neural networks (ANN). In order to test the proposed method HIF events were simulated as well as other common network events using the ATP software. The proposed framework is part of a HIF detection system to be implemented in a substation of an electric utility in the state of Sao Paulo.

A PC-based instrument for harmonics and interharmonics measurement in power supply systems

Power quality (PQ) metrics deterioration occurs in the distribution system by increasing the distributed generation plants, the existence of non-linear and harmonic loads. As a distribution system operator running under the Turkishelectricity regulation, a battery investment was made to improve PQ metrics to provide quality electricity service to customers by focusing on Volt/VAr optimization to obtain voltage stability parameters. The reverse power flow caused by the distributed generation can be eliminated and the power factor would be improved with the reactive support with this investment. This study includes the reasons for the battery pilot project, the engineering methodology, and post-solution improvements.

The measurement of Power Quality (PQ), generally performed at Low Voltage (LV) level, is gaining more and more importance also at the Medium Voltage (MV) level, due to the increasing presence of switching power converters (both loads or generators) directly connected to MV grids. In this case, the use of Voltage Transformers (VTs) is unavoidable to scale voltage down to amplitudes compatible with the input ranges of PQ instruments. However, the current absence of an international standard dealing with VTs used for PQ measurements leaves the manufacturers and the users in a situation of complete uncertainty, since different products can have performance specifications tested and stated in completely different ways. This paper aims at defining an integrated approach for the evaluation of VTs accuracy used for PQ measurements, focusing on harmonics and interharmonics. The paper provides experimental results of the tests performed on a MV inductive VT according to the proposed procedure. As a result, it is demonstrated that VT accuracy in the measurement of a specific phenomenon should be evaluated with complex waveforms including the contemporary presence of different PQ phenomena.