Identifying Transformer Incipient Events for Maintaining Distribution System Reliability

This paper presents the time domain and timefrequency domain analysis results of incipient events in single-phase distribution transformers. This analysis will aid in the development of an automatic detection method for internal incipient faults in the transformers. The detection method can provide information to predict failures ahead of time so that the necessary corrective actions are taken to prevent outages and reduce down times. The analyzed data was obtained from simulations and experiments. Time-frequency analysis was performed using Discrete Wavelet Transform (DWT). The obtained results are discussed

Black Start Restoration of Islanded Droop-Controlled Microgrids

The electricity grid faces the possibility of outages due to extreme weather events, cyber-attack, and unexpected events. When these unwanted events occur, it is desired that electricity be restored as soon as possible to meet the power demands of critical loads. The microgrid approach to power restoration holds a lot of promise, since microgrids can operate in island mode. This paper presents a novel sequential restoration methodology for microgrid black start. The microgrid architecture considered is assumed to be operating in multi-master mode. The master distributed generators (DGs) are coordinated to operate together through droop control. Several operational constraints are formulated and linearized to realize a mixed-integer linear programming (MILP) problem. The method is studied on an islanded microgrid based on a modified IEEE 13 node test feeder. Detailed transient simulation in PSCAD was used to verify the accuracy of the restoration methodology. The developed restoration method can maximize the energy restored while ensuring good voltage and frequency regulation, and ensure that power scheduling mismatch is shared in the desired proportion

Islanded Microgrid Restoration Studies with Graph-Based Analysis

The need to restore and keep the grid running or fast restoration during emergencies such as extreme weather conditions is quite apparent given the reliance of other infrastructure on electricity. One promising approach to electricity restoration is the use of locally available energy resources to restore the system to form isolated microgrids. In this paper, we present a black start restoration method that forms islanded microgrids after a blackout. The master DGs in the formed microgrids are coordinated to work together through droop control. Several constraints, including incentive-based demand response (DR) with direct load control (DLC) and distributed generator (DG) operation constraints, were formulated and linearized to realize a mixed-integer linear programming (MILP) restoration model. To improve compactness and to ensure that the model is neither under-sized nor over-sized, a pre-processing graph analysis approach was introduced which helps to characterize the least number of restoration steps needed to optimally restore the microgrid. Studies were performed on a modified IEEE 123 node test feeder to evaluate the effects of demand response, non-dispatchable DGs, and choice of restoration steps on the quality of the restoration solution. When possible, the proposed method yields an interconnected multi-master microgrid with improved redundancy

Configuration Validation Using ATP Simulation For An Automatic Shipboard Power System Restoration Method

Abstract – When a fault occurs in power systems, protective devices detect fault areas and disconnect the faulted sections of the network by opening circuit breakers, fuses etc.. Some loads become unavailable after the fault and should be reenergized, as quickly as possible, after the fault has been isolated. The re-energizing procedure is called service restoration. In Navy shipboard power systems (SPS), the automated reconfiguration for service restoration is a new focus area of research. The main objective of restoration on the SPS is to restore as much out-of-service load as possible by reconfiguration with priority given to critical loads. Once the switching actions to restore a load have been determined, the next step is to make sure that there are no operating constraint violations because of those switching actions. To check for constraint violations, line flows and voltage at each node need to be determined via a Load Flow. In this paper a method using ATP simulation, during runtime, to determine if the suggested switching actions for restoring loads violate any operating constraints, have been presented

A Flocking-Based Paradigm for Hierarchical Cyber-Physical Smart Grid Modeling and Control

It is well known that information will play an important role in enhancing emerging smart grid system operation. Therefore, questions naturally arise as to when the increased data-dependence may be considered excessive. Two practical considerations emerge: 1) communications and computational overhead, in which redundant and irrelevant information acquisition and use results in heavy computational burden with limited performance return; and 2) increasing risks of power system disruption due to information delay from communication congestion or cyber attack. One strategy to improve smart grid resilience is to determine the appropriate degree of dependence on cyber information to balance performance with overhead and risk. In this paper, we present a hierarchical cyber-physical multiagent model of smart grid system operation based on flocking theory in the context of the transient stability problem. Through this model, we study strategies that harness a selective degree of cyber technology by leveraging physical couplings. Our formulation enables the identification of large-scale distributed control strategies for robust and resilient power grid operation. We demonstrate the potential performance improvements of our findings on the New England 39-bus power system for case studies involving a variety of system faults and communication delays

PSCAD Implementation of IEEE 123 Node Test Feeder

The accompanying file is a PSCAD setup of the IEEE 123 node test feeder. In the PSCAD model, the substation transformer has been omitted. The switches default states have been set according to their default setting in the IEEE 123 node test feeder documents. All voltage regulators’ tap settings have been fixed to those obtained in the IEEE results though an option is provided to set each regulator to vary its tap settings with changing primary voltage. The loads are modeled as ZIP loads with values set to be the same with the IEEE test system. The results from the PSCAD simulation closely matches the published result in the original test system. This PSCAD model could potentially be used in such applications as restoration, reconfiguration, distributed generator interconnection and transient simulation studies

PSCAD Implementation of IEEE 123 Node Test Feeder

The accompanying file is a PSCAD setup of the IEEE 123 node test feeder. In the PSCAD model, the substation transformer has been omitted. The switches default states have been set according to their default setting in the IEEE 123 node test feeder documents. All voltage regulators’ tap settings have been fixed to those obtained in the IEEE results though an option is provided to set each regulator to vary its tap settings with changing primary voltage. The loads are modeled as ZIP loads with values set to be the same with the IEEE test system. The results from the PSCAD simulation closely matches the published result in the original test system. This PSCAD model could potentially be used in such applications as restoration, reconfiguration, distributed generator interconnection and transient simulation studies