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This study introduces a novel approach to power system fault diagnosis by synchronised phasor measurements. Conventionally, faults are diagnosed through the status of protective relays and circuit breakers which are activated following a fault. However, the hidden failures of the protection system has itself often been among the main suspects of partial or widespread blackouts. This study proposes an alternative fault diagnosis approach independent of the function of the protection system. An analytical method is introduced for power system fault diagnosis using dispersed synchronised measurements and bus impedance matrix (Zbus). Fault inception is first detected by local phasor measurement units (PMUs). Fault diagnosis is then carried out in a hierarchical manner so that first the faulted zone of the system is diagnosed, next the faulted line in the faulted zone is diagnosed and finally the fault point along the diagnosed line is located by gradient descent. The proposed method is applied to the WSCC 9-bus, where fault incidents on all of the transmission lines are examined. Moreover, the proposed method is successfully applied to the IEEE 118-bus test system consisting of 28 PMUs, which demonstrates successful fault diagnosis and location for a large-scale power system despite the limited coverage of PMUs.

A new approach is proposed for obtaining a non-linear area-based equivalent model of power systems to express the inter-area oscillations using synchronised phasor measurements. The generators that remain coherent for inter-area disturbances over a wide range of operating conditions define the areas, and the reduced model is obtained by representing each area by an equivalent machine. The parameters of the reduced system are identified by processing the obtained measurements, and a non-linear Kalman estimator is then designed for the estimation of equivalent area angles and frequencies. The simulation of the approach on a two-area system shows substantial reduction of non-inter-area modes in the estimated angles. The proposed methods are also applied to a ten-machine system to illustrate the feasibility of the approach on larger and meshed networks.

The study presents a fault locator for three-terminal transmission lines under dynamic conditions such as power oscillation based on synchronised phasor measurement units. This approach based on conventional static fault locator can express the dynamic characteristics of supplied signals and consider them as time-variant signals whose magnitude and frequency are changing against time. Therefore the authors can apply its ability of describing dynamic characteristics to three-terminal transmission lines and get the dynamic parameters of transmission lines under the dynamic conditions. By using Newton iteration, the proposed dynamic fault locator can acquire the three-terminal fault-location indices to identify a fault section and estimate the distance to fault. The performance of the proposed method is evaluated by Power Systems Computer Aided Design/Electromagnetic Transients including DC (PSCAD/EMTDC)-generated signals under various situations. An extensive set of simulation results show that the distinctive features of this method are that it performs with better accuracy than the conventional method for all types of faults at different fault locations and is practically immune to fault resistance.

Synchrophasor measurement data enhances the transmission line protection. This paper proposes an improved line protection against single phase-ground faults using synchronized phasor data. This algorithm prevents the relay mal-operation caused by high fault resistance. This algorithm calculates the phase difference between relay point voltage and fault point voltage based on the relation between negative sequence of relay point current and fault point current. After, the calculated phase difference between relay point voltage and fault point voltage will be compared with set point voltage phase referred from the relay point voltage phase. The fault detection action will be taken according to a certain phase difference relation between fault point voltage and set point voltage. This method is then applied to a practical single machine single line system. The results show that the suggested algorithm could determine in-line faults accurately with less computational time. It also has proved that this method is immune to the fault resistance, system conditions.

With the development of synchronized phasor measurement technology in recent years, it gains great interest the use of PMU measurements to improve state estimation performances due to their synchronized characteristics and high data transmission speed. The ability of the Phasor Measurement Units (PMU) to directly measure the system state is a key over SCADA measurement system. PMU measurements are superior to the conventional SCADA measurements in terms of resolution and accuracy. Since the majority of measurements in existing estimators are from conventional SCADA measurement system, it is hard to be fully replaced by PMUs in the near future so state estimators including both phasor and conventional SCADA measurements are being considered. In this paper, a mixed measurement (SCADA and PMU measurements) state estimator is proposed. Several useful measures for evaluating various aspects of the performance of the mixed measurement state estimator are proposed and explained. State Estimator validity, performance and characteristics of the results on IEEE 14 bus test system and IEEE 30 bus test system are presented.

This paper presents a new method for transient stability assessment (TSA) of power systems using kernel fuzzy rough sets and extreme learning machine (ELM). Considering the possible real-time information provided by phasor measurement units, a group of system-level classification features were firstly extracted from the power system operation condition to construct the original feature set. Then kernelized fuzzy rough sets were used to reduce the dimension of input space, and ELM was employed to build a TSA model. The effectiveness of the proposed method is validated by the simulation results on the New England 39-bus test system.

Weak fault detection and localization have been a major concern in power grid for a long time. Existing methods are usually model-based, and extracting fault characteristics by frequency domain signal analysis, which are difficult to cover a variety of situations. And when the signal-to-noise ratio (SNR) is low, the success rate cannot be guaranteed. Based on the widespread synchronized phasor measurements, a model-free data-driven method is proposed to address these issues. From the point of view of statistical characters, the M-P law is used to filter the abnormal eigenvalues of the matrix formed by raw data of a power grid, which is the key to extract features of weak fault without modeling. Furthermore, the SNR is improved by the correlation analysis of the matrix elements. With the use of split window, the method is able to monitor power grid in real time, and can eliminate random errors by considering the width of the window. The case studies, using both 80-node simulated network and real distribution network, validate that the proposed method is sensitive and universal to different scenarios.

Although there has been a practice of transposition of transmission lines, most of the real life EHV/UHV lines are untransposed. The distance protection of such lines becomes very complicated. With the advent of Global Positioning System (GPS) and Fiber optics technology, current differential protection can be a better choice for such lines. This paper proposes current differential protection scheme for protection of untransposed transmission lines based on equivalent-π line model. The proposed differential relay basically works on difference of currents in series branch (computed) from equivalent-π line model. As the measurements are time synchronized, the performance of relay is immune to line charging current. The analysis has been carried out in phase coordinates. ATP/EMTP programs have been used to simulate system disturbance and algorithm is implemented MATLAB. The result shows the efficacy and robustness of proposed algorithm. (4 pages)

Research presented in this paper is part of the idea for developing smart transmission grid (STG) supported by system integrity protection schemes (SIPS) based on phasor measurement unit (PMU) technology. The main objective of SIPS is to monitor the state of power transmission networks in real-time and if needed in emergency cases to undertake advanced actions. Contribution of this paper is new SIPS development method and busbar splitting scheme supported by synchronized phasor measurement technology (SPMT). Proposed method gives detail description how to develop SIPS through several steps, as well as the simulation of their operation. It is based on heuristic approach and detailed AC power flow analysis. Busbar splitting scheme is described through its activity and initiation conditions in this paper. Initiation model is given in the form of graphical representation with its releasing and blocking conditions. Developed method application to the IEEE 14 busbar system is given after its defining. Carried out tests show that developed method can mitigate potential overloads of the observed network part by using suggested busbar splitting schemes.

In order to prevent large scale cascading failure, continuous measuring and monitoring of the system in real time is necessary for secure and reliable operation of the interconnected Power Grid system. The actual analog signal has to be sampled to establish the fundamental frequency within a specific frequency zone. With the help of that frequency, the signal is reconstructed at time domain of fundamental frequency tone and dynamic phasors of the system are estimated by using Phasor Measuring Unit. The objective of this paper is to determine proper algorithm of the Phasor Measuring Unit and detection of fault within a specified time when disturbance occurs in the system.