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Wide area monitoring system (WAMS) installed in Croatian Transmission system operator (HOPS) control center collects and process synchrophasor data in real time. There are ongoing activities on continuous, incremental and gradual upgrading of existing WAMS with new protection functions and control algorithms towards WAMPAC system. This paper describes line differential protection based on synchrophasor data and implemented on PDC server running in control room. In the first phase, the algorithm was applied to historical synchrophasor data. That check revealed that estimation block in PMUs at both line ends must implement the same estimation technique. Because of this finding, only lines with the same PMU type on both ends were selected for real-time performance test in the second phase. Several months long performance test successfully confirmed a soundness of concept and its implementation. It was proven in practice that new algorithm can be used as an effective tool for validation of basic protection performance and a solid foundation for development and implementation of backup protection.

Croatian TSO has finalized a Proof of Concept (PoC) for monitoring generators with purpose of primary frequency regulation mode within Wide Area Monitoring System (WAMS) using synchrophasors in control room. The main goal of PoC was testing well proven synchrophasor technology for purposes of advanced monitoring of generator units connected to transmission network. This technology was tested on six generators connected to 220 kV and 110 kV transmission network in five power plants. For this project three different ways of acquiring synchrophasor data for analyses were used. Data were collected with phasor measurement units (PMU) and from archives. Some PMUs were already installed on high voltage side of step up transformer earlier for other purposes, rest of measurement campaign was done using portable PMUs in two power plants. Results show full potential of using this data for monitoring generator for primary regulation. Output from project gives Croatian Transmission system operator (TSO) possible technical solution which can be implemented in control room.

The power system is an example of a nonlinear system with many different oscillation sources and accordingly many oscillation types, including electromechanical oscillations, oscillations caused by control elements, or subsynchronous oscillations. The estimation of oscillation types in the power system gives a direct insight into the state of the system stability. The ability to estimate oscillations in real time is facilitated by installing a Wide Area Monitoring System (WAM), which enables accurate metering with accurate timestamps. The HOPS synchrophasor concentrator, in addition to its main role of collecting and processing synchrophasor measurements, has an electromechanical oscillation analysis module. This paper describes the oscillation detection tool for historical data with an aim to develop real time oscillation detection system for potentially unstable events in real-time.

Energy Storage Systems installed at primary substations can be used by different participants of the power system for handling the emerging uncertainties caused by supply-side variations, demand-side flexibility and grid topology changes. This work presents a practical design for the monitoring system of the controller of the grid interactive energy storage system. This monitoring scheme takes advantage of synchrophasor measurements gathered by phasor measurement units of wide area measurement systems. The analysis of synchrophasor measurements provides real-time situational awareness over the status of the grid. Therefore, the integration of synchrophasor measurements into the control loop of GI-ESS will enable them to participate in power services of the flexibility market. Furthermore, the implementation of a basic power oscillation damping function as an example of power services using the proposed monitoring system is illustrated in this paper.

This paper presents a measurement-based load modelling approach. The approach uses portable Phasor Measurement Unit (PMU) devices that can be rapidly installed at substations. These PMUs use GPRS communication to send data to a Phasor Data Concentrator (PDC). Two PMUs are installed at each monitored station. One PMU is installed at the low-voltage side of the supply transformer while the other PMU is installed on a selected substation outgoing feeder. Disturbances are continuously monitored by these devices. A measurement-campaign of at least 6 months is typically required to capture enough data to characterize the load dynamics and load behaviour. To this purpose, voltage disturbances are filtered out and extracted from the measurement campaign data. Each relevant voltage disturbance is “replayed” off-line using a simulation software to identify the most likely aggregated load model at the monitored feeder/substation. The load model identification methodology produces representative load models for system planning applications. This method provides added value to transmission operators as a better and more realistic representation of load model will aid planning engineers to adequately assess dynamic voltage stability.

Synchrophasor data are used in new protection functions created in wide area monitoring, protecting and controlling system in control center. Basic voltage and current protection were developed as a first tool. Also angle protection was implemented on lines equipped on both ends with phasor measurement unit. In this paper testing procedures and results for whole chain from substations to control center will be described. Operating monitoring functions will be extended with these new basic protection functions. New protection in control center will use overcurrent protection and system protection for transmission lines. Comprehensive testing procedures were used at final stage of test process and will be presented in paper. Time delay aspect for protection function using different device types and communications links will be elaborated in detail.

Transmission system operators utilize phasor measurement unit devices from different vendors. Those devices are basic parts of Wide Area Monitoring Protection and Control system installed in control center. Detail study work needs to be obtained in order to have deep analyses of data generated from those devices. Data gathered in WAMPAC system is used as input for protection and control functions. Extensive laboratory and field test procedures have to be carried out for whole chain of phasor data. Complete testing from substation to control center is presented.

In this paper, noise propagation through a two-stage nonlinear algorithm for measurement of harmonic distortion in power systems according to IEC 61000-4-7 is analyzed. Noise generated in the instrument’s input circuitry is considered as an aggregated noise source without detailed characterization of its origin. The first stage of the measurement algorithm is the discrete Fourier transform (DFT) of the input signal. Noise propagation through the DFT is analyzed by means of probability theory. The result of this analysis, the probability density function (pdf) of the DFT spectrum amplitudes, is used for characterization of the second stage of the measurement algorithm – the root-sum-square grouping of several spectrum components into a single harmonic distortion index. In this way, pdfs of the most common harmonic indices are derived and analyzed. The study presented reveals that noise generated in the input stage produces, besides the already known variance of the results, an offset in the harmonic distortion indices. Analysis of the resulting pdfs implies that an increase in the number of components in the grouping procedure increases the offset error, whereas the standard deviations are essentially independent of the number of components included in the group. The validity of the model derived has been tested with a prototype of a low-cost portable instrument for three-phase power quality measurements.

Power distribution systems often exhibit different harmonic behaviours at different locations. It is not usually possible to completely characterise the distortion at a particular site, however, due to insufficient data about the measured system and instrumentation inability to evaluate or register complete set of measurement quantities. In this paper existing power quality standards are analysed and new harmonic distortion indices are derived. A new index describing the total harmonic distortion in current measurements, TRD, is suggested in order to simplify and standardise harmonic measurements. Another index representing the increase of harmonic voltage distortion with TRD, equivalent harmonic impedance zeq, is proposed as an efficient way of characterising a particular site. The framework described here can be used to predict future harmonic behaviour at any previously measured point. Finally, extensive harmonic measurements of a real distribution system were performed to prove the usefulness of the proposed indices.

The paper presents a control system solution based on synchronized phasor measurements for the urban area transmission system. Specificity of the analyzed system is a highly meshed overhead and cable sections network, with two city power plants, providing the city's district heating and electricity supply. The mathematical model for static and dynamic analyses of various scenarios was build and verified using measurements from originally developed and deployed portable hand-held phasor measurement units. The control system architecture and functionalities as well as developed control actions algorithms are given, focusing on island operation of the issued transmission system, as the city power plants are capable to supply the critical consumers.

The influence of noise on the measurement uncertainty of different harmonic indices calculated according to IEC grouping algorithms is analyzed in this paper. The results of a previously published paper are extended to cases where the input noise is superimposed on to the harmonic signal. Probability density functions (pdf) of the harmonic indices are obtained by means of numerical integration and are used for assessment of the statistical properties of the output noise. The values of the offset errors and standard deviations are compared to uncertainties obtained by applying the uncertainty propagation law, as indicated by The Guide to the Expression of Uncertainty in Measurement (GUM).

A simple measurement is proposed for source identification and characterization. Power transformer is proposed as a point to perform the measurements in a cheap and practical way. Simulation has been undertaken to confirm validity of the proposed method. The procedure for the load characterization, outlined in this paper, has been tested in real power distribution system to establish the contribution of the certain industrial customer to the harmonic distortion. In contrary to previous assumption, it has been found out that the analyzed customer is not dominant source of distortion and is only partially responsible for the harmonic distortion at the PCC.