The integration of advanced measuring technologies in distribution systems allows distribution system operators to have better observability of dynamic and transient events. In this work, the applications of distribution grid measurement technologies are explored in detail. The main contributions of this review are the review of the most recent applications of microPhasor Measurement Units, Smart Meters, and Power Quality Monitoring devices used in distribution systems, considering different novel methods applied for data analysis; In addition, this work derives an inputoutput table that relates measured quantities from microPhasor Measurement Units and Smart Meters needed for each specific application found in this extensive review.
The integration of advanced measuring technology, such as Smart Meters, microPhasor Measurement Units (PMUs), and Power Quality Monitors (PQM) in distribution systems, allows distribution system operators to have better observability of the electrical distribution system. Highprecision measurements, rapid communication, and remote storage of the extracted data are some of the characteristics of these measuring devices.
The urgent reason to enhance the observability with the deployment of new technology devices is mainly driven by the increasing integration of distributed energy resources (solar energy, wind energy, bioenergy) and flexible loads (electric vehicles and air conditioning systems) in distribution grids. These devices have a significant effect on the operation, stability, and quality of energy distribution networks. Customers are able to exchange active power with the electric grid in twoway directions, increasing the complexity and uncertainty of the distribution system operation ^{[1]}^{[2]}^{[3]}.
Recent works have reviewed the general applications of measurement technologies in distribution systems. In Reference ^{[4]}^{[5]}, the authors described the technology architecture used in smart grids, including the metering and communication systems for transmission and distribution systems. In Reference ^{[6]}^{[7]}, the authors presented an overview of measurement technology, including smart meters, smart sensors, smart power meters, Phasor Measurement Units (PMUs), Phasor Data Concentrators (PDCs), and Supervisory Control And Data Acquisition (SCADA) systems, for monitoring, protection, and control in smart grid networks. However, none of these overviews mentioned the required data characteristics for each application or the types of measuring devices used for distribution systems.
Relevant overviews of PMUs applications for distribution grids were described in Reference ^{[8]}^{[9]}^{[10]}^{[11]}, which include monitoring, diagnostic, and control applications. In fact, these papers have not reviewed recent research work related to μPMUs data applications. In recent reviewed papers ^{[12]}^{[13]}, authors have focused on PMUs applications, including state awareness, event detection, adaptive protection, and network reconfiguration. However, these reviews do not include a list of PMUs applications based on the input data, methods, and visualization of each application.
Furthermore, several review papers have studied the applications of smart meter data for distribution networks ^{[14]}^{[15]}^{[16]}^{[17]}. In Reference ^{[14]}, the authors reviewed the smart meter data techniques and methodologies developed for different applications. They also discussed the big data issues, the transition of energy systems, data privacy, and security. In Reference ^{[15]}, the authors reviewed the methods and techniques for using smart meter data, such as forecasting, clustering, classification, and optimization. However, these works do not mention the data inputs necessary to implement each of these methods.
Some research papers have studied power quality applications. Reference ^{[18]} analyzed the harmonic impact of the integration of renewable sources into the distribution network. Some other recent applications are for optimal location of PQM in distribution systems, due to the limitation of measuring devices ^{[19]}. The development of optimal placement techniques and energy data are discussed in Reference ^{[20]}^{[21]}^{[22]}^{[23]}^{[24]}. To the best knowledge of the authors, this is the first time that a work integrates an overview of the applications of PQM for distribution systems. In this review the main contributions are:
A review of the most recent applications of microPhasor Measurement Units, Smart Meters, and Power Quality Monitoring devices used in distribution systems, considering different novel methods applied for data analysis.
An inputoutput table that relates the measured quantities from microPhasor Measurement Units and smart meters needed for each specific application found in this review.
In this section, a review of recent applications and techniques used for data processing ofμmimicroPMUs, smart meters, and PQM devices is shown, based on a literature review of the last four years. In addition, few relevant articles were considered due to their high impact of the research over the last few years. Figure 1 summarizes the overall groups of applications found in this work, considering only three advanced measurement devices (MicroPMUs, Smart meters, and PQMs). It is important to mention that each measurement device work with different resolutions; therefore, the applications are also oriented to monitoring events with the same time response.
Figure 1. Applications of Distribution Measurement Technologies.
Recent applications of microPMU data are shown in this subsection. Table 1 shows a general summary of the applications, methods and input data found in more than 25 articles. A total of eight application groups were obtained, and two large groups can be highlighted, situational awareness and state estimation. These two groups require a high sampling rate of the measured data in order to visualize transitory events in the distribution network. Table 2 lists the input data (MicroPMUs measurements) required for each specific application. Most of the described methods are based on synchronized current and voltage phasors (magnitude and phase) to identify, analyze, and monitor possible failures in the distribution network. A brief description of each of these application groups and methods found for data analysis is provided below.
Table 1. Recent application groups of microPMU data.PMU
Data
Application Group 
Input Data  Methods  Output Visualization  Year (Reference) 
Real MicroPMU Data?  Simulation Data? 

Situational Awareness 
3Ph voltage and currents (magnitudes and angles), frequency, active power, reactive power. 
1. Three stage algorithm 2. Dynamic WSMW 3. Generalized GLM 4. Parametric Sparsity 5. Compensation Theorem 6. CUSUM 7. Thevenin Estimation 8. LWSS 9. Experimental Analysis 10. Kernel PCA and pSVM 11. KF and Model Synthesis 12. Theoretical Analysis 
Voltage magnitud change, current magnitud change, active power change. 
1. 2020 ^{[25]} 2. 2019 ^{[26]} 3. 2019 ^{[27]} 4. 2019 ^{[28]} 5. 2018 ^{[29]} 6. 2018 ^{[30]} 7. 2018 ^{[31]} 8. 2017 ^{[32]} 9. 2017 ^{[33]} 10. 2016 ^{[34]} 11. 2016 ^{[35]} 12. 2019 ^{[36]} 
1. Yes 2. Yes 3. Yes 4. No 5. Yes 6. Yes 7. No 8. Yes 9. Yes 10. Yes 11. Yes 12. Yes 
1. No 2. No 3. No 4. Yes 5. Yes 6. Yes 7. Yes 8. Yes 9. No 10. No 11. Yes 12. Yes 
Topology Identification 
Voltage (magnitude and phase angle) 
1. Recursive Grouping 2. Adaptive Lasso 3. TSVTop 4. Projection of Norm tren Vector 
New switch configuration in the topology 
1. 2020 ^{[37]} 2. 2019 ^{[28]} 3. 2018 ^{[38]} 4. 2015 ^{[39]} 
1. No 2. No 3. No 4. No 
1. Yes 2. Yes 3. Yes 4. Yes 
Classification of Events 
3 PhVoltage and currents (magnitudes & angles) 
1. Multiclass SVM 2. NN based autocoders (Softmax) 3. PCA and SVM based autocoders 
Event location and disruptive classes 
1. 2019 ^{[26]} 2. 2018 ^{[40]} 3. 2017 ^{[41]} 
1. Yes 2. No 3. No 
1. No 2. Yes 3. Yes 
State Estimation 
Voltages, currents, line admittances, loads. 
1. WLS, WLS with NR 2. RNESE & WTVSE 3. LSE, ARMA and SVM 4. Compensation Theorem 5. Compressive Sensing & WLS 6. DFT and WLS 
Estimation of voltage magnitud, loads, currents and errors from actual states. 
1. 2020 ^{[42]} 2. 2020 ^{[43]} 3. 2019 ^{[44]} 4. 2018 ^{[45]} 5. 2017 ^{[46]} 6. 2018 ^{[47]} 
1. No 2. No 3. No 4. Yes 5. No 6. Yes 
1. Yes 2. Yes 3. Yes 4. Yes 5. Yes 6. Yes 
Optimal Placement 
Voltage phasor, parameters of the branch. 
1. Mixed Integer Semidefinite Programming Model 2. Integer linear programming 3. Greedy Search 
Optimal number and localization of microPMUs at buses 
1. 2020 ^{[43]} 2. 2019 ^{[48]} 3. 2018 ^{[30]} 
1. No 2. No 3. Yes 
1. Yes 2. Yes 3. Yes 
Model Calibration 
Frequency, voltage and current phasors. 
1. NonLinear Estimation  Calibrated parameters  1. 2020 ^{[49]}  1. No  1. Yes 
Operation Events 
Voltage and currents (magnitudes and angles) 
1. Fuzzy Cmeans 2. Data driven analysis based on RLC Model 
Switching event, operational parameters (real and reactive power flow), voltage and current (feeders and loads) 
1. 2017 ^{[50]} 2. 2017 ^{[51]} 
1. Yes 2. Yes 
1. No 2. No 
Table 2. Specific applications of MicroPMU data.
MicroPMU Data  Specific Applications in Distribution Network  

3 PhI (Phasors):  Analysis of Transient Load Behaviors ^{[50]}  
3 PhCurrents (Phasor) & Y (Admitance matrix): 
Optimal number and localization of microPMU in buses ^{[43]}^{[49]} μ 
3PhV (Phasors):  Estimation of Voltage Magnitude error ^{[43]}  Identification of swithching actions and new topology scenarios ^{[28]}^{[38]}^{[52]} 

3PhV (Phasors) & Loads:  Load and Voltage Estimation Error ^{[44]}  
3 PhV & 3 PhI (Phasors):  Single and 3 phase current & voltage event detection ^{[27]} 
Response of a PV farm (Current and Voltage) of 3 lightning events ^{[33]}. 
Detection of capacitor bank switching ^{[51]} 
3 PhV & 3 PhI (Phasors):  Fault position with accuracy, sensitivity to noise level ^{[32]} 
Distinguishing between two disruptive events and the normal load changing event ^{[42]}. 
Identify event location and disruptive classes ^{[28]}^{[40]} 
3 PhV & 3 PhI (Phasors):  Event Location and Identification ^{[29]}  Event detection of voltage sag based on Data Index and Reconstruction Error ^{[34]}. 
Fault currents to coordinate relays ^{[31]} 
3 PhV & 3 PhI (phasors), frequency: 
Estimation of subtransient generator model variables ^{[49]}. 
Cyclic frequency trend and anomaly signals detection ^{[25]} 

3 PhV & 3 PhI (Phasors), Active and Reactive Power, frequency: 
Anomaly Detection Architecture ^{[30]}^{[26]}  Optimal DPMU placement ^{[30]}  Event Classifier of PQ events ^{[26]} 
3 PhV & 3 PhI (Phasors), loads, Y (admitance matrix):  Tracking State Estimation ^{[45]}^{[46]} 
Situational Awareness: Most of applications are driven to aware distribution operator of transient events due to the high sampling frequency and communication abilities of microPMUs.μIn Reference ^{[29]}, the authors proposed a method based on the compensation theorem to detect abnormal events in distribution systems. This method generates an equivalent circuit using the current and voltage phasors captured byμmicroPMUs. Similarly, a cumulative sum (CUSUM) algorithm was proposed in Reference ^{[30]} to detect anomalies having limited microPMUs. Validation results showed the effectiveness of this algorithm to voltage, current, and active power changes in the distribution system. In Reference ^{[26]}, the authors proposed the multiclass Support Vector Machine (SVM) method to detect and classify abnormal events based on large volumes of data. A total of 1.2 billion real measurements of two microPMU installed in a distribution feeder were analyzed to evaluate their actual performance and were validated with two different methods, which are KNearest Neighbor (kNN) and Decision Tree (DT). The results showed that the proposed technique can accurately identify a total of 10,700 events, outperforming the other two evaluated techniques. In Reference ^{[27]}, a generalized Graph Laplacian Matrix (GLM) to visualize different voltage and current events in a real test feeder was proposed. Moreover, a kernel principle component analysis and a partially Support Vector Machine (pSVM) was used in Reference ^{[34]} for voltage sags detection based on data index and reconstruction error. The effectiveness of these methods were tested on a real distribution network with μPMUs. In Reference ^{[25]}, the authors proposed a Granger causality technique to analyze the frequency event propagation from the transmission network to the main feeder of a distribution network usingμmicroPMUs measurements. The authors also proposed a sparse coding method to determine the spectral frequency of abnormal events. The proposed approach was tested with realtime data from a public network located in Riverside, California. In Reference ^{[32]}, the authors proposed a state estimator to identify faults in distribution lines using microPMUs. This estimator determines the error, using a weighted residual metric. Validation tests have shown that the proposed estimator correctly detects and locates distribution line failures in presence of bidirectional flows. In Reference ^{[33]}, an experimental analysis of lightening strikes was proposed using microPMU data collected during a day of rainstorms. The main interest of the study was to analyze the transient response of a 7.5 MW PV farm and its associated substation. Results showed the high resolution of microPMU to capture transients of current and voltage phasors during lighteninginduced events. Reference ^{[28]} proposed a parametric sparsity method to detect and locate events from distribution grids. An optimization algorithm based on particle swarm was proposed in Reference ^{[31]} to coordinate overcurrent relays installed in microgrids and distribution networks. In addition, a technique to identify uncertainties in realtime was also proposed. Authors in Reference^{[35]} proposed a method to synthesize steady state models for multiplesections of active distribution networks (unbalanced) using realtime PMU data. Additionally, a Kalman filtering technique was proposed to extract the quasisteady state components, noise filtration, and outliers from PMUs. The results from two simulated events demonstrate that the proposed technique can produce an accurate model for any feeder configuration located between PMUs installed in active distribution networks. Authors in Reference ^{[36]} evaluated the transmission characteristics of a Rogowski electronic current transformer and an electronic voltage transformer (EVT) in a simulated and real testing platform. Experiment results showed that the EVT and the traditional power transformer have similar performance in the transient process of disconnecting switch breaking. Additionally, the power transformer was not affected by temperature changes, while that in the electronic voltage transformer the temperature had a great influence impact.
Topology Verification: Distribution networks models are often imprecise or outdated. Topology identification is essential for monitoring and control distribution systems. The microPMUs devices are able to extract measurements from network nodes in realtime in order to track topology changes. In Reference ^{[37]}, the authors proposed a technique to estimate impedances through a reduced Kron matrix also called “subKron” form. Additionally, a recursive clustering algorithm was implemented to reconstruct the topology of radial networks from line impedances. The results of the simulation showed that this technique is robust to measurements with additive noise that is generally captured by microPMUs; however, it has limitations when applied to large distribution networks. In Reference ^{[28]}, the authors proposed an adaptive lasso technique to identify changes in topology caused by permanent failures in distribution systems. This technique is able to locate faults geographically in real time using PMUs that capture voltage and current phasors with high accuracy. The results of this work demonstrated the efficiency of this technique in different case studies. In Reference ^{[38]}, the authors proposed a method to detect topology changes in distribution networks based on the TimeSeries Signature Verification (TSV) method. This method considers the relationship that occur when there are changes in network topology. Validation results showed that the proposed method works satisfactorily with the partial knowledge of the state of the network. Authors in Reference ^{[52]} proposed a data driven approach based on the projection of a norm tren vector in to a topology library. This method was able to detect over 32 possible topology scenarios in a distribution grid.
Classification of Events: The classification of disturbing events is responsible for quantifying abnormal events that occur in the system. Recent approaches of event classification have been explored. In Reference ^{[26]}, the authors proposed the multiclass Support Vector Machine (SVM) method to classify abnormal events based on large volumes of data. A total of 1.2 billion real measurements of two microPMU installed in a distribution feeder were analyzed to evaluate their actual performance, and were validated with two different methods (KNearest Neighbor (kNN) and Decision Tree (DT)). The results showed that the proposed technique can accurately identify a total of 10,700 events, outperforming the other two evaluated techniques. A neural network approach was proposed in Reference ^{[40]}, using autoencoders along with softmax classifiers to distinguish two disruptive events. The performance of the algorithm was tested to identify if a capacitor bank switching has a normal load change or if it has a malfunctioned switching. In Reference ^{[41]}, authors proposed two different algorithms to classify disruptive events in distribution networks. The first algorithm was based on a hybrid combination of Principle Component Analysis (PCA) together with a multiclass SVM, and the second algorithm was with an autoencoder along with softmax classifier. Validation results showed the superiority of the second algorithm over the first algorithm in term of accuracy. The data for training and testing was simulated in the IEEE 13bus distribution system.
State Estimation (SE): Distribution system state estimation (DSSE) is the minimum set of variables that can be used to describe the dynamic behavior of the system, advanced measurement devices are useful to quantify these variables. In Reference ^{[42]}, the authors proposed a decentralized state estimator to improve the operating privacy in active distribution networks and microgrids. In this work, the iterative procedure based on quadratic programming was demonstrated, which used microPMUs as main inputs. The studies demonstrated a high accuracy of this proposed approach for different scenarios. In Reference ^{[43]}, the authors proposed a regularized estimator to accurately identify the operating state of the system in a short time. This estimator operated with different measuring devices with different resolutions using data mainly from SCADAtype systems and microPMUs. This fusion of data allowed to provide greater robustness of the estimator to noise and less error in the estimation of states. The authors of Reference ^{[44]} proposed a weighted least squarebased for distribution system state estimation, in which voltages and loads are chosen as state variables to compensate insufficient realtime measurements in medium voltage distribution systems. In Reference ^{[45]}, the authors proposed a method based on the compensation circuit theory to generate an equivalent circuit. This method was able to estimate and follow the system states when sudden load changes occurred. This method used real measurement from microPMUs in a distribution system. In Reference ^{[46]}, the authors proposed a simple method to determine the state variables based on power line data and bus voltage phasors from microPMUs installed in a distribution network. The authors showed that the proposed method can be robust to noise measurements, high levels of distributed generation, and a reduced number of measurements. Authors in Reference ^{[47]} proposed an open testbed to evaluate and compare PMU estimation algorithms accuracy under experimental conditions, considering the noise propagation in order to quantify the uncertainty contributions and their impact on the estimates of the variables.
Optimal Placement: The optimal placement of microPMUs aims to maximize the observability of the distribution network while minimizing investment costs. In Reference ^{[43]}, the authors propose a DWeighted Total Variation State Estimation (WTVSE) algorithm to estimate system states with a reduced time scale (every 15 min), considering the observations of a SCADA system and microPMUs. In addition, a semidefined scheduling model was proposed to optimally locate microPMUs and thus improve state estimation. The results of the simulation of a 95 bus distribution network showed that this proposal presents a great accuracy in the estimation of states under a diversity of scenarios, in addition to its low computational complexity. In Reference ^{[48]}, the authors proposed a linear programming model to optimally locate phasor measurement units in distribution networks. The aim of this model was to ensure observability during possible changes in topology by operational actions. The results obtained from a medium voltage distribution network in southern China showed that the proposed method is efficient and robust to topology changes. In Reference ^{[30]}, a greedy search algorithm was proposed for optimal microPMUs placement. This algorithm uses an optimal location criterion to achieve maximum observability and therefore increase the monitoring range considering different event scenarios.
Model Calibration: Dynamic models can be calibrated based on realtime advanced measurements. This is a new field of application that promises to improve the current models. In Reference ^{[49]}, the authors proposed a methodology to enhance the synchronous generator model, based on PMU measurements. First, the estimation of the variables (frequency, voltage, and current phasors) of the dynamic state were obtained. Then, the authors calibrated the inertia constant and the reactances of the model. Finally, the performance results were obtained under different perturbation scenarios. The authors conclude that the calibration of parameters in real time requires high accuracy of advanced measurement devices.
Operation Events: The high resolution of the microPMU data allows to observe the dynamics (transient) of operational events that generally occur in distribution networks, such as the reconnection of microgrids, the connection of loads, and/or the connection of capacitor banks. In Reference ^{[50]}, the authors proposed a method to analyze the transient behaviors caused by the addition of flexible loads/generation in distribution feeders. This approach modeled the load profiles based on the collection of data from various μPMU located at the low voltage level. The authors demonstrated that it is possible to compromise network reliability if several flexible regulation resources are located on the same feeder. In Reference ^{[51]}, the authors analyzed the switching events of a threephase capacitor bank to determine the operational parameters and the flow of reactive energy from a capacitor. The authors conducted an experimental study based on real measurements from microPMUs that were installed in an electrical distribution network. The results showed that the magnitude of the transient current of the feeder depends on the initial condition and the phase angle at the time of capacitor switching.
The following subsection describe the applications of smart meter data. The objective is to present the methods developed in recent years, based mainly on machine learning techniques for the processing, prediction and monitoring of the distribution network. Table 3 shows a summary of the applications, methods and general input/output data of 37 relevant articles published in recent years. The classification of smart meters applications were divided into eight groups; however, the most prominent groups are the forecasting group and the topology identification group. These applications are mainly used by operators to monitor and control the electrical distribution network.
Table 3. Recent application groups of Smart Meter Data.
Application Groups  Input Data  Methods  Output Visualization  Year (Reference) 
Real SM Data ? 
Simulation Data? 

Anomaly Detection  Load Profiles (kWh), RMS Voltage, history data 
1. Isolation Forest 2. CCADSW, SVR, RF 3. Quasilinear classifier 4. Lambda system 
Anomaly consumption detection, data integrity assault, identification of anomalous consumption. 
1. 2019 ^{[53]} 2. 2017 ^{[54]} 3. 2017 ^{[55]} 4.2016 ^{[56]} 
1. No 2. Yes 3. No 4. Yes 
1. Yes 2. Yes 3. Yes 4. No 
Compression of Data  Load Profiles (kWh)  1. Deep Learning via SCSAE 2. SAE 3. SVD 4. KSVD, Kmean, DWT, PCA, PAA 
Storage and transmission of large sets of power consumption data measured by smart meters. 
1. 2020 ^{[57]} 2. 2019 ^{[58]} 3. 2017 ^{[59]} 4. 2017 ^{[60]} 
1. Yes 2. Yes 3. Yes 4. Yes 
1. No 2. No 3. No 4. No 
Customer Characterization 
Load Profiles (kWh), Sociodemographic atributes of households 
1. GBM, CART, RF, DWD, Discrimination with Polynomial Kernel 2. Random Forests, SVM, Knearest Neighbors and NN 3. Discriminative multitask relationship learning model 4. DeepCNN and SVM 
Unemployment prediction of household occupants, prediction of homeoccupancy status of households, prediction of multiple household characteristics. 
1. 2020 ^{[61]} 2. 2019 ^{[62]} 3. 2019 ^{[63]} 4. 2018 ^{[64]} 
1. Yes 2. Yes 3. Yes 4. Yes 
1. No 2. No 3. No 4. No 
Forecasting  Load Profiles (kWh), Weather 
1. Extended kmeans, ANN and MLR 2. ML using a Qlearning 3. LSTM Recurrent Neural Network 4. FFANN, NARX, DNN, Gradient Tree Boosting and Random Forests 5. Load Ensemble Method 6. Boosting additive quantile regression 7. Conditional Kernel Density estimation 
ShortTerm Load Forecast in Residential Buildings, prediction interval of electricity cost for different timeofuse tariffs, forecast the aggregated load. 
1. 2020 ^{[65]} 2. 2020 ^{[66]} 3. 2019 ^{[67]} 4. 2019 ^{[68]} 5. 2018 ^{[69]} 6. 2018 ^{[70]} 7. 2016 ^{[71]} 8. 2016 ^{[72]} 
1. Yes 2. Yes 3. Yes 4. Yes 5. Yes 6. Yes 7. Yes 8. Yes 
1. No 2. No 3. No 4. No 5. No 6. No 7. No 8.No 
Load Classification  Load Profiles (kWh)  1. Statistical Tool 2. Deep autoencoder and (SOM) 3. Finite Mixture Model of Gaussian multivariate distributions 4. Constrained kmeans algorithm 
Energy tariffs at different times of the day and identification of time periods during the season, months, etc. 
1. 2020 ^{[73]} 2. 2020 ^{[74]} 3. 2016 ^{[75]} 4. 2016 ^{[76]} 
1. Yes 2. Yes 3. Yes 4. Yes 
1. No 2. No 3. No 4. No 
Non Technical Loss Detection 
Load Profiles (kWh), Geographical information, line parameters 
1. Hybrid Deep Neuronal Networks 2. Deep convolutionalrecurrent NN 3. Hybrid DT and SVM classifiers 4. Optimum PF, kmeans, GMM, Birch, affinity propagation and SVM 
Detection and location of electricity thefts, irregular and regular profiles 
1. 2020 ^{[70]} 2. 2020 ^{[77]} 3. 2016 ^{[78]} 4. 2016 ^{[79]} 
1. Yes 2. No 3. No 4. Yes 
1. No 2. Yes 3. Yes 4. No 
Sensor Fusion  Load profiles (kWh), currents, voltages, admittance matrix, bus voltage phasor, power flows. 
1. Recurrent neural networks, and sparse Bayesian learning for state estimation 2. Modified Dynamic Mirror Descendent 3. Mixed integer linear programming 
Locating harmonic sources, separation of measurements in a distribution feeder, prediction of outage regions. 
1. 2020 ^{[80]} 2. 2020 ^{[81]} 3. 2019 ^{[82]} 
1. No 2. Yes 3. No 
1. Yes 2. Yes 3. Yes 
Topology Identification 
Load profiles (kWh), RMS voltage (feeder and smart meter), line parameters, currents. 
1. Physicalprobabilisticnetwork, lasso regression 2. Treebased search methodology 3. PCA and Grap Theory 4. DSTE Algorithm 5. Graphical Modeling 6. Inhouse algorithm based Voltage profile correlation analysis 
Operation mode of distribution networks and voltage correlations with different buses. Topology Estimation 
1. 2019 ^{[83]} 2. 2019 ^{[84]} 3. 2017 ^{[85]} 4. 2016 ^{[86]} 5. 2016 ^{[87]} 6. 2015 ^{[88]} 
1. No 2. Yes 3. No 4. Yes 5. Yes 6. Yes 
1. Yes 2. No 3. Yes 4. No 5. Yes 6. No 
Compression of Data: Data compression techniques help to reduce the volume of data collected from advanced measurement devices; they also help to improve the transmission speeds from multiple measurement points. In Reference ^{[57]}, the authors proposed a deep learning technique with a convolutional dispersion autoencoder for data compression. This method keeps more information than Singular Value Decomposition (SVD) and PCA methods, at the same coding speed, preserving details of the original power, and the calculation times are lower. In Reference ^{[58]}, the authors proposed a neural network based on an automatic encoder to compress household consumption data in a distribution network. This proposed encoder must be installed on the user’s side to compress the smart meter readings. Compared to some existing linear compression models, such as PCA, DWT, and SVD, the SAE compressor has lower % errors according to a study carried out with real data from China and Ireland. Similarly, in Reference ^{[59]}, a methodology using the SVD technique for data compression was presented. This methodology was used in a test system with data from different substations of a UK company. This technique achieves a significant reduction in the volume of data to be transmitted, with minimal error in its reconstruction. Reference ^{[60]} proposed a SVD sparse coding technique to compress smart meter data. This dispersion technique extracts the information using linear combinations from load clusters. The results obtained comparing 4 techniques showed that the proposed technique obtains the least loss of information.
Customer Characterization (Sociodemographic): Predictive analysis can also be applied to determine the characteristics of network consumers, for example, predicting the number of unemployed people, number of occupants in a building and/or predicting daily household activities. In Reference ^{[61]}, authors compared six machine learning models to determine the number of unemployed people in a household. The overall results showed that the most accurate models were the multilayered perception and distanceweighted discrimination aproach. Similarly, in Reference ^{[88]}, a neural model was proposed to determine the employment situation of consumers. This type of information can help governments to reduce unemployment levels and also help to improve their economy. In Reference ^{[62]}, the authors implemented a genetic algorithm to identify the number of occupants in a residential building using smart meter data. Validation results showed that this algorithm can optimally predict the number of occupants in households. In Reference ^{[63]}, an automatic learning model was proposed to identify characteristics of residential occupants, e.g., people living in the household, average age, and daily activities in the household, from the daily electricity consumption of the users. The validation of this model was implemented in a real distribution network in Ireland, in which technical characteristics allow obtaining this information.
Forecasting: The optimal generation planning requires that operators have tools to predict demand growth in a short and medium terms. In recent years, techniques based on machine learning have been developed, considering multiple variables in the prediction models, including electricity consumption, weather conditions, electricity tariff costs, and population growth that contributes to generate accurate prediction models. In addition, with the growing technological development, it is possible to concentrate all this data in real time, which allows the parameters of the models to be systematically updated. In Reference ^{[66]}, the authors designed a shortterm prediction model based on a Qlearning scheme that used meteorological data and smart meters as input variables. This scheme was composed of ten deterministic prediction models and four probabilistic heuristic models which were selected based on their accuracy. The results presented demonstrate a higher accuracy of Qlearning predictions than traditional approaches. In Reference ^{[65]}, an artificial neural network with a multiple regression technique was proposed to predict load consumption using temperature and solar irradiation variables in the model to obtain more accurate predictions. The validation of this proposal was demonstrated in a real data set of smart meters that included photovoltaic generation. In Reference ^{[67]}, the authors proposed a recurrent neural network technique to predict consumption in shortterm scenarios. This proposed approach was tested on a public data set on real residential consumption and compared with other techniques for validation. In Reference ^{[68]}, the authors proposed a NestBcktr algorithm for shortterm load forecasting. A comparison between other six machine learning algorithms were made, in terms of RMSE indices and absolute errors. The validation was programmed in Python using a 2year data set from smart meters. The results showed that this proposed algorithm predicts consumption with lower errors. In Reference ^{[69]}, a load ensemble method to forecast aggregated loads was proposed. This method produces multiple training and prediction models with different subprofiles. In addition, a weighted optimization is used to combine and determine the best prediction. In Reference ^{[71]}, an additive regression model was proposed to forecast the distribution of electricity consumption added to the network. This model generates different probability scenarios that help operators to plan and operate the network in the future. In Reference ^{[72]}, the authors used a method based on kernel density estimation to forecast future growth of electricity consumption. This method considered predictions of electricity costs for different tariffs, which means potentially important savings for users.
Load Classification: Refers to the grouping of electrical consumption including residential, commercial and industrial loads. In recent years, various grouping techniques have been proposed with data from smart meters that have provided useful information to distribution system operators. In Reference ^{[73]}, electricity consumption and energy tariff variability were analysed in four different seasons. In this analysis, several statistical tools were applied to analyze different energy consumption’s using real data from smart meters. The study showed that users consume more energy when they do not know the variability of energy costs. The authors recommended that consumers learn about tariff dynamics in order to minimize energy consumption costs. In Reference ^{[74]}, the authors proposed a prediction technique based on a trained autoencoder that analyzed smart meter data and also grouped them using a self organizing map. In Reference ^{[75]}, a finite mixture model based on a variant Gaussian distribution to identify nontypical behavior in the distribution system was proposed.^{[76]}, the authors proposed a kmeans clustering algorithm for phase identification of interconnected customers in the network. This algorithm uses as inputs the voltage signals from smart meters and SCADA measurement system. The test results obtained from a distribution network in California showed that the algorithm has an overall accuracy above 90%.
Nontechnical loss detection: Detection of nontechnical losses are basically electricity theft consumers, faulty meters or billing errors. In Reference ^{[70]}, a hybrid deep neuronal network to detect nontechnical losses in smart meters was proposed. This algorithm was tested with real smart meter data from the largest electric utility in Spain. Validation results showed the accuracy of this aproach to identify anomalies in distribution systems. In Reference ^{[77]}, the authors proposed a deep convolutional neural network to detect non technical losses in distribution grids. This approach detected manipulations of consumer energy readings that falsely overloaded the power company. The results obtained in this work indicate that the fusion of multiple data, including smart meters, SCADA systems, and meteorological reports, contributes to the accurate detection of energy theft consumers. Reference ^{[78]} proposed a methodology based on the hybrid combination of decision tree and support vector machine classifiers to detect fraudulent consumption. In Reference ^{[79]}, the authors proposed a classifier based on the optimalpath forest algorithm to detect anomalies and nontechnical losses in distribution networks. This machine learning technique requires training from regular consumer profiles in order to generate a sample group base, and, when a new consumer connects with irregular profiles, he is automatically identified. Validation results showed that this technique is robust and accurate for classifying different types of consumers.
Sensor Fusion: Sensor fusion is the integration of data from smart meters with other measurement devices and is intended to improve the observability and accuracy of monitoring distribution systems. In Reference ^{[80]}, the authors proposed a state estimator to identify harmonic sources in an unbalanced distribution system. The state estimator was based on neural networks and Bayesian learning, and the input signals were captured by smart meters and microPMUs. Validation results showed the high accuracy of the estimator even in presence of distributed generation. In Reference ^{[81]}, the authors proposed an algorithm to disaggregate loads from a distribution feeder into N components. The main objective was to separate network losses and reactive power injections from capacitors. This algorithm was based on a learning aproach and used multiple measurement sensors to determine the technical feasibility of separation. Validation results indicate that data fusion of reactive power measurements in the algorithm can improve the accuracy in the prediction of the network behavior up to 32%. In Reference ^{[82]}, the authors proposed a mixed integer linear programming algorithm to determine fault locations and prediction of outage regions. This algorithm requires of smart meter data and remote fault indicators measurements in near realtime in order to support distribution system operation in a precise timestep.
Topology Identification: Information on the topology of the distribution network helps the operator to make optimal decisions when unexpected events occur. Authors in Reference ^{[83]} proposed a physical probabilistic network model to identify the connections using voltage correlations between different buses. This method was compared with a lasso regression method. In Reference ^{[84]}, a treebased search methodology was proposed to approximate the missing cable information in low voltage distribution networks. In Reference ^{[85]}, a method to identify the connectivity between load phases in distribution networks was proposed. Additionally, the presence of technical losses and some errors that may arise during measurements (missing data, synchronization) were considered. This method implemented the principal component analysis to infer the topology of the use of smart meter measurements. This method proved to be robust in the presence of distributed generation. In Reference ^{[86]}, the authors presented an algorithm for topology estimation based on voltage measurements from smart meters. Validation results showed that 9 out of 10 of the estimates were correct in secondary circuits of a Georgia Tech distribution system, even in noisy environments. The authors mentioned that it is extremely important to have ultraprecise measurement devices for correct estimation of voltage drop based topology, especially when analyzing short lines feeding small loads. In Reference ^{[87]}, a graphical model to identify distribution topologies based on a probabilistic relationship between different voltage measurements was proposed. Additionally, the authors proposed an expansiontree based algorithm aimed at minimizing the KullbackLeibler divergence in a distribution system. In Reference ^{[88]}, an algorithm to correct connectivity errors of smart meters and meters on distribution feeders was developed. This algorithm identified the neighboring meters through a voltage profile correlation analysis.
In this last section, recent applications of PQM devices are shown, considering different methods. Table 4 shows a general summary of the applications, methods, and PQM input/output data obtained from 18 articles published in recent years. The PQM applications are divided into six groups, of which the optimal placement group can be highlighted by the number of publications in recent years. One of the groups included in this table was the power quality monitoring systems, which is basically the application of PQM in the distribution network of some countries that have carried out projects to improve the quality of transported energy.
Table 4. Application groups of Power Quality Monitoring Data.
Application Group 
Input Data  Methods  Output Visualization  Year (Reference) 
Is It Real PQM Data ? 
Simulation Data? 

Optimal Placement  Topology of Distribution Grid (Line parameters, Transformers capacity, Loads and generation). Historic Measurement of PQM (sag/swell, THD) 
1. TLBO Algorithm 2. Multiobjective Evolutionary Algorithm with Tables 3. Seeker Optimization Algorithm based on Pareto 4. Entropybased and Bayesian Network Model 5. PMRA Algorithm 6. WLS Method 
Optimal placement of PQM in complex distribution networks. 
1. 2019 ^{[89]} 2. 2018 ^{[90]} 3. 2018 ^{[91]} 4. 2016 ^{[92]} 5. 2016 ^{[93]} 6. 2018 ^{[94]} 
1. No 2. No 3. No 4. Yes 5. No 6. No 
1. Yes 2. Yes 3. Yes 4. Yes 5. Yes 6. Yes 
Fault Location  3Phase Voltage and Current Transient, such as Sags/Swell. 
1. Multihidden Markov model 2. LAMDA technique. 3. Fault distance estimation 
Locate and forecast the presence of PQ disturbances, and determine the fault type on radial DS. 
1. 2019 ^{[95]} 2. 2007 ^{[96]} 3. 2007 ^{[97]} 
1. Yes 2. Yes 3. Yes 
1. No 2. No 3. No 
Harmonic Analysis  3phase Voltage and Current magnitude of harmonic distortion, Odd harmonics, flicker, THD. 
1. Fast Fourier Transform 2. Fourier Analysis 3. Fourier Analysis 
Describe harmonic behavior at an individual site, as well as at many sites across a DS using different indices of PQ. 
1. 2017 ^{[98]} 2. 2016 ^{[99]} 3. 2016 ^{[100]} 
1. Yes 2. Yes 3. Yes 
1. No 2. No 3. No 
Power Quality Monitoring System 
Power quality indices (Voltage and current sags/swells, THD, indi vidual harmonics, flick ers, etc.) 
1. Sag reporting techniques. 2. Data acquisition system. 3. Data acquisition system. 4. Load Flow Algorithm 
Power Quality Monitoring Projects for Distribution Network Service Providers. 
1. 2018 ^{[101]} 2. 2017 ^{[102]} 3. 2017 ^{[103]} 4. 2019 ^{[104]} 
1. No 2. Yes 3. Yes 4. Yes 
1. Yes 2. No 3. No 4. No 
Data error detection  Voltage and current phasors, THD, TDD, and short term flicker. 
1. Correlation Analysis  Detection and correction error in PQ monitoring data. 
1. 2017 ^{[105]}  1. Yes  1. No 
Load Modeling  RMS voltage and current, Active and Reactive Power, during disturbances on the upstream networks. 
1. Load parameter derivation  Derive, test, and verify the dynamic load model parameters. 
1. 2013 ^{[106]}  1. Yes  1. Yes 
Optimal Placement: This large application group describes some recent approaches to determine the optimal positioning of PQM, with the aim of minimizing network investment costs. In Reference ^{[89]}, the authors implemented the TLBO algorithm to optimally locate PQMs by considering degradation in large distribution networks. The objective of this approach was to minimize the number of PQMs in order to minimize the costs of assets in the monitoring system. In Reference ^{[90]}, the authors proposed the MEAT optimization algorithm to find the best locations to install advanced PQM in distribution network. This proposed approach had multiple objectives, such as minimizing monitoring investment costs, minimizing voltage drops, and maximizing system observability. The authors recommend this approach for those electricity companies that need to evaluate the investments they will make to optimally improve network observability. In Reference ^{[91]}, authors proposed the seeker optimization algorithm to find the optimal locations of PQM devices in a 14bus test system. The test system results showed that with few locations of the PQMs the values of the harmonic state were accurately estimated. In Reference ^{[92]}, an optimization algorithm based on Bayesian network models was proposed. The objective was to minimize the investment costs of PQ monitoring devices and to maximize the observability of the distribution network. Evaluation results showed that this algorithm significantly reduced the uncertainty of PQ values on unsupervised feed links. In Reference ^{[93]}, the authors proposed a probabilistic method to observe the uncertainty associated with high/low impedance faults in distribution systems. The objective was to determine the optimal location of PQM devices to maximize observability in the system. In addition, two indices were proposed in this work to quantify the robustness of distribution networks with different voltage drops. The authors in Reference ^{[94]} mathematically analyzed the impact of the accuracy of state estimation (with power meters) by varying the spatial distribution and number of devices installed in the network. The objective was to minimize the number of devices to be installed and to identify the optimal location in the distribution networks, ensuring a desired accuracy in the estimation of voltage and current. The results show that the proposed mathematical framework is a useful tool for the design of optimal device placement strategies in current monitoring systems.
Fault Location: Due to the high sampling rate and precision of this device, some authors have proposed algorithms to track faults in distribution systems. In Reference ^{[95]}, the authors proposed a PQ disturbance predictor based on a MultiHidden Markov Model (MHMM). This predictor analyzes large volumes of data, including local weather variables to improve forecast accuracy, and also incorporates a Hadoop system that reduces calculation times for very complex systems. The forecast of this model can be adapted to different resolutions (minutes, hours, days, or up to 3 weeks). In Reference ^{[96]}, the authors proposed a multivariate data analysis technique to locate line failures in unbalanced distribution systems.
This technique was based on PQM devices installed in distribution substations, line parameters and the topology configuration. The authors concluded that the proposed technique benefits operators to accelerate the tasks of system restoration (permanent faults). In Reference ^{[97]}, the authors designed a power quality software to identify and locate faults in distribution feeders. This software performs a short circuit analysis based on historic and real measurements of PQM. The validation results showed that this software has better accuracy for locating faults in distribution feeders than some commercial software.
Harmonic Analysis: These application refers to detect harmonics or abnormal behaviours in distribution system using advanced PQ devices. The authors in Reference ^{[98]} presented multiple techniques to locate harmonic sources in distribution grids using PQ data. The objective was to design strategies to mitigate potential problems. Additionally, in this work a harmonic compliance index was presented, which allows to give a quick indication about violations of the permissible harmonic limit in a particular site. In addition, a graphical method based on harmonic reports showed a wide detail of harmonic performance in many sites in a compact form. The authors in Reference ^{[99]} presented several digital processing techniques to detect missing or abnormal data. The validation tests were implemented in 8 German networks with residential, commercial and mixed customer loads. The authors concluded that: "The identification of useful information cannot be manual anymore and requires a comprehensive set of intelligent and automated analysis tools". Authors in Reference ^{[100]}, compared the robustness, flexibility, and limitations of a composite bus index and an aggregate bus index. These two indices were proposed and validated in a test system to evaluate the PQ of buses installed in distribution networks. The authors concluded that these indices were closely related and it is important to provide an adequate weighting in order to have a greater flexibility between them.
Power Quality Monitoring System: Power Quality Monitoring Systems (PQMS) have been implemented in several countries to improve the power quality in distribution systems. In Reference ^{[101]}, the authors designed a power quality monitoring software based on realtime data. This software was capable to analyze complex power quality problems using a FPGAtype hardware that worked as an independent integrated system. The authors concluded that these modern monitoring system substantially improve the life of the assets that make up the smart grids. Authors in Reference ^{[102]} presented a project report of a power quality monitoring system which has been in operation in Australia since 2002. The objective of this report was to provide a general overview of the main problems found during the development of the PQMS. The authors concluded that monitoring systems with advanced measurement devices capable of providing PQ indices will rapidly increase in future power grids. Authors in Reference ^{[103]} designed a PQ monitoring system for a new generation of substations located in Shanghai, China. This system was based on international communication standards that allow remote monitoring of harmonics at a frequency of 12.8 kHz. This system is capable to analyze complex power quality problems, as well as the location of harmonic sources in the distribution networks. An improved hardware/software architecture with a realtime monitoring and control system for the integration of micro grids into MV distribution networks was presented in Reference ^{[104]}. The proposed system is capable of estimating the power flows of the medium voltage branch by means of load power measurements and a suitable load flow algorithm. The proposed system was considered more efficient than SCADA implementation.
Data error detection: Data error detection is the process where the system automatically detects and corrects errors in PQ monitoring data. In Reference ^{[105]}, an automatic detection and correction of errors system was developed based on data captured by PQ meters installed on a UK smart grid. The objective of the automatic system was to reduce the number of errors caused by various factors, such as poor installation of the devices, poor synchronization between multiple PQMs or by noncaptured data (missing data), and maximizing the useful data for future network operations. The authors conclude that the number of errors can be reduced considerably by adopting a correct installation procedure for PQ monitoring devices.
Load Modeling: To represent the loads of an electrical network, mathematical models are used to simulate the dynamic or static behavior considering the active and reactive power of the load with respect to the variation of the voltage and frequency. In Reference ^{[106]}, the authors derived the parameters of a dynamic load model of an 11 kV distribution network using a power quality monitoring system. The measurements used in the load model includes voltages, currents, active power, and reactive power at a sampling frequency of 1.6 kHz. To validate these results, the distribution network was simulated in a software using the parameters of the load model obtained and the load response to a disturbance was compared against a real disturbance in the distribution system captured by the PQMs. The general conclusion of this work was that 30–40% of the commercial loads considered in the distribution network are composed of induction motor loads, and if you want to make an accurate load model at the distribution level it is imperative to consider them.
This work made a comparison of eight advanced measurement devices for distribution networks based on their technical characteristics, including the sample frequency, reporting periods, measuring data, costs, precision, and time response. The comparative results showed that microphasor measurement unit and power quality monitor devices have the best performance overall to track dynamic and transitory events in distribution systems, due to their highprecision measurements, communication systems and remote storage of the extracted data.
This work also reviewed the most recent applications of microPMU, smart meters, and PQM data, considering novel methods and techniques. In addition, an inputoutput table that relates measured quantities from microPMU and smart meters needed for each specific application was developed in this review. From the extended literature reviewed in this work, the following conclusions are drawn:
The dominant applications of interest for PMU data is currently leaning towards analyzing situational awareness events and estimating the state variables of the system in near realtime. With the extremely high resolution (sampling rate up to 30,720 s/s), amplitude accuracy of 0.05%, and angle accuracy of 0.01%, it is possible to visualize transitory events in the distribution network. The sensor accuracy can have a strong influence on the uncertainty of the quantities to be measured and thus can highly impacting in the algorithms performance.
The dominant application of interest of smart meter data is currently driven to forecast future load consumption in a short term horizon based on artificial intelligence, machine learning, and deep learning techniques. Topology identification is also of current interest due to the limited knowledge about the topology of low voltage networks. Some novel methods are related to correlation techniques and graph theory methods.
The most recent applications of PQM devices are related to find the optimal placement of the PQM based on multiple objectives, focusing on minimizing the cost of monitoring, minimizing topological ambiguity and maximizing the load monitoring.
The integration of microPMU, PQM, and smart meters is an alternative to improve visibility, precision, and security in active distribution systems. However, the large amount of data generated with the use of these devices is a challenge that demands high computational complexity and the development of efficient algorithms with the ability to process information in realtime. Data connectivity with different resolutions, parameters, and locations is a challenge that requires further investigation.
This entry is adapted from the peerreviewed paper 10.3390/en13143730