Ahad Esmaeilian

Transmission-Line Fault Analysis Using Synchronized Sampling

An automated analysis approach, which can automatically characterize fault and subsequent relay operation, is the focus of this paper. It utilizes synchronized samples captured during transients from both ends of the transmission line to detect, classify, and locate transmission-line faults and can verify that the tripped line has indeed experienced a fault. The proposed method is tested for several faults simulated on an IEEE 118-bus test system and it has been concluded that it can detect and classify a fault using prefault and postfault recorded samples within 7 ms of fault inception and can accurately locate a fault with 3% accuracy. This time response performance is highly desirable since with the increasing use of modern circuit breakers, which can open the faulty line in less than two cycles, the time window of the captured waveforms is significantly reduced due to the unavailability of measurement signals after breakers open.

Reliable Implementation of Robust Adaptive Topology Control

The topology (transmission line) switching to achieve economic and reliability gains in the power grid has been proposed some time ago. This approach did not gain much attention until recently when large penetration of renewable generation created incentives to use transmission line switching to control sudden changes in power flows and mitigate contingencies caused by the generation variability. This paper explores implementation issues related to circuit breaker (CB) monitoring, relay setting coordination and detection of relay misoperations in the context of the topology switching sequence implementation. The paper covers risk-based assessment of CB status needed for determination of reliable switching sequences; it indicates how relay settings may be changed due to switching actions; it also provides an on-line algorithm for detection of relay misoperations, which identifies the lines that may be switched back to service after being trip erroneously by a relay.

Fault Location Using Sparse Synchrophasor Measurement of Electromechanical-Wave Oscillations

This paper presents a novel system-wide fault-location method for transmission lines utilizing electromechanical-wave oscillation propagation phenomena. The method uses synchrophasor measurements during disturbances obtained from phasor measurement units sparsely located in the network. The method determines the time of arrival of electromechanical waves propagating from the fault point to sparsely located phasor measurement units. By taking the speed of electromechanical-wave propagation as well as topology of the network into account, the method is able to detect the faulty line. Finally, by adding fictitious buses inside the faulty line and applying a binary search method, the location of fault is accurately pinpointed. The main advantage of the proposed method is the use of a limited number of PMUs which reduces the cost of implementation. The method was developed in MATLAB and tested with the IEEE 118-test system. Test results reveal the high accuracy of the method in detecting and locating faults.

Prevention of Power Grid Blackouts Using Intentional Islanding Scheme

Intentional islanding is often conducted as the last resort to preserve the electric grid from severe blackouts. The intentional islanding scheme deliberately segregates the power system into a number of self-sustained islands to enhance the transient stability of the power network. In this study, a spectral clustering algorithm is presented to obtain an islanding solution, which results in minimal power flow disruption across boundaries of islands. The constraint in the spectral clustering method is introduced based on generator coherency grouping. The proposed scheme ensures that each island is only comprised of generators, which are synchronized with each other. The proposed clustering scheme utilizes a more computationally efficient and accurate k-medoids algorithm comparing to k-means ones. The proposed intentional islanding method is scrutinized using the IEEE 9-bus and IEEE 118-bus models. The results of simulations demonstrate that the proposed method can effectively prevent blackouts by separating the systems into stable islands.

Evaluation of Fault Analysis Tool under Power Swing and Out-of-Step Conditions

Several major blackouts were caused by distance relay mis-operation. Distance relay mis-operation may occur following a large disturbance in the system causing power swing and out-of-step conditions. If an on-line fault analysis tool is able to detect power swing or out-of-step conditions and indicate mis-operation of relays, the operator may be notified to switch back the healthy transmission lines tripped due to relay mis-operation. A new automated fault analysis tool comprising fault detection, classification and location has been developed and its performance under various power swing and out-of-step conditions is reported. The test results indicate that the fault analysis tool performs better than distance relay under power swing and out of-step conditions and can be used as a tool to verify distance relay operation in practical circumstances. The simulations have been performed using IEEE118 bus test system modeled in ATP software.

Controlled islanding to prevent cascade outages using constrained spectral k-embedded clustering

Controlled islanding scheme is frequently considered as the final solution to retain power system operation under cascading event outages which can lead to a major blackout. The islanding scheme can improve the power system transient stability by preserving stable areas from further outages as well as reducing the complexity and overall time required for restoration process. In this paper a constrained spectral k-embedded clustering method is defined to determine an islanding scheme with minimal active power flow disruption, while addressing generators coherency problem. The proposed spectral clustering method uses k-medoids algorithm which is more accurate and computationally efficient than conventional k-means algorithm. The proposed scheme is tested using the IEEE 9-, IEEE39- and IEEE 118-bus test systems. Simulation results show effectiveness of the proposed methodology in creation of stable islands and prevention of system blackouts.

Prevention of cascading outages using sparse wide area synchrophasor measurements

Early prediction of cascade events outages followed by immediate and proper control actions can prevent major blackouts. This paper introduces a novel method to predict cascade event outage at early stage and mitigate it with proper control strategy. In the first step, methodology employs sparsely located phasor measurement units to detect disturbances using electromechanical oscillation propagation phenomena. The obtained information is used to update system topology and power flow. Next, a constrained spectral k-embedded clustering method is defined to determine possible cascade event scenarios, and if needed proper switching action is listed to intentionally create islands to minimize load shedding and maintain voltage profile of each island. The method was developed in MATLAB and tested with IEEE 118 bus test system. The results demonstrate effectiveness and robustness of the proposed method.