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The selection of a grounding configuration and design of a grounding impedance is of vital importance for the stability and functionality of power systems, including industrial and commercial power systems. These key aspects of grounding systems have been the subject of various standards, industrial codes, and recommended practices. In this article, a review, modeling, and analysis of different grounding system designs are provided. The different grounding system design discussed in this article is compared in terms of the ground potential, ground currents, and overvoltage during ground faults. The various grounding system designs are implemented for power systems components in order to assess their capabilities and performance. Several tests are conducted for ground faults, when different grounding system designs are used. Test results show that some grounding system design can limit ground currents, with minor effects on ground potentials. Other grounding system design can limit ground potentials, while fail to limit ground currents. [ABSTRACT FROM AUTHOR]

This article presents the implementation and performance testing of a bus-differential protection for buses, which interconnect battery storage systems (BSSs). The proposed bus-differential protection is based on employing the α β 0 components of the apparent powers flowing in all branches of the protected bus. The α β 0 components of the apparent powers are employed due to their ability to accommodate changes in the power flow direction in the branches connected to the protected bus. The apparent powers are determined using the measured voltage and currents in all branches connected to the protected bus. The proposed α β 0-based bus-differential protection is implemented and tested for internal and external faults, which are created during the charging and discharging of BSSs. Test results demonstrate the ability of the proposed α β 0-based bus-differential protection to initiate fast, accurate, and reliable responses to internal and external faults in the protected bus. Observed response features of the proposed protection are found to have minor sensitivity to the mode of operation of the BSS (charging and discharging), fault location (internal and external), and/or fault type. [ABSTRACT FROM AUTHOR]

This article presents the development, implementation, and testing of a digital differential protection for three-phase (3φ) solid-state transformers (SSTs). The developed digital differential protection is designed to implement the ANSI 87 T protection function. The differential currents used by the developed protection are created by the dq0 components of the currents flowing in the high and low voltage sides of a 3φ SST. Internal faults are detected and identified using the energy contents of high-frequency subbands present in the dq0 differential currents. The desired high-frequency subbands are extracted using the phaselet transform that processes signals without sensitivity to nonstationary changes in their frequency and/or phases. Energy contents in the extracted high-frequency subbands allow accurate, fast, and reliable detection and identification of faults in any part of a 3φ SST. The proposed digital differential protection is implemented for performance testing using a laboratory 25-kVA 3φ SST. Performance results demonstrate accurate, fast, and reliable response to different fault and nonfault events. Furthermore, responses of the developed differential protection are found to be consistent regardless of the fault type, fault location, and/or loading level. [ABSTRACT FROM AUTHOR]

This paper presents the development and performance evaluation of a new approach for detecting voltage flicker events in power systems hosting distributed generating units. The proposed approach is based on extracting the magnitudes and phases of the different frequency sub-band contents present in the voltage signal(s). Desired magnitudes and phases are extracted by processing the voltage signal(s) using nine phaselet frames that are realized by a modulated filter bank. The modulated filter bank is designed using nine digital high-pass filters (HPFs), each of which implements one phaselet frame. The coefficients of HPFs are determined by bi-orthogonal phaselet basis functions. Extracted high-frequency sub-band contents provide signature information for accurate detection and quantification of voltage flickers. The performance of a phaselet transform based approach is experimentally tested for different conditions, including voltage flicker events that are triggered by an interconnected photovoltaic system. Performance results show accurate, reliable, and fast detection and quantification of voltage flickers, along with a negligible sensitivity to the source producing voltage flicker events. [ABSTRACT FROM AUTHOR]

This paper develops and tests a new method for managing the responses of multiple digital relays employed in interconnected permanent-magnet generator (PMG)-based wind energy conversion systems (WECSs) with battery storage. The developed method utilizes digital relays (modules), each of which provides protection for a specific location of the PMG-based WECS and battery storage. The outputs of the developed digital protection scheme are trip signals to operate circuit breakers in PMG-based WECS, battery storage, and point-of-common-coupling. The modular digital protection is implemented for experimental testing on a 5-kW PMG-based WECS that has a 2.3-kW battery storage. Test results show that the developed protection can offer fast, accurate, and reliable responses to faults occurring in different parts of the tested WECS and battery storage. In addition, test results show that the modular digital protection has minor sensitivity to the location of faults, charge/discharge cycles of the battery storage, and/or levels of power delivery to the host grid. [ABSTRACT FROM AUTHOR]

This paper presents the analysis and development of a new method for electric fault detection in induction motor drives. The proposed method is based on extracting the magnitudes and phases of the high-frequency subband (HFSB) contents present in the d - q-axis components of the stator currents (id and iq) in an induction motor. The desired magnitudes and phases are extracted by processing id and iq using phaselet frames that are realized by a modulated filter bank. This filter bank is designed using six digital high-pass filters, whose coefficients are determined by biorthogonal phaselet basis functions. Extracted HFSB contents provide signature information that can offer accurate and fast detection of faults. The phaselet-based electric fault detection method has been made into a procedure for digital implementation. The performance of the proposed method is evaluated offline for collected stator currents from two different induction motor drives under different operating conditions. Offline test results show accurate, reliable, and fast detection of electric faults, with minor sensitivity to the ratings, loading levels, and type and location of faults. [ABSTRACT FROM PUBLISHER]

This paper presents the online implementation and performance evaluation of the phaselet-based method for detecting electric faults in induction motor drives (IMDs). The online implementation of tested fault detection method is achieved using a digital signal-processing board, where the inputs are the 3φ stator currents and the output is a trip signal. The desired fault feature is extracted using six digital high-pass filters, whose coefficients have been obtained using phaselet basis functions that are generated by the biorthogonal 2.1 scaling function. The performance of the phaselet-based fault detection method is tested for two different IMDs that are fed across-the-line and through a frequency drive system, when operated at different loading levels. Experimental test results show accurate, reliable, and fast fault detection, along with negligible sensitivity to the speed, loading levels, IMD ratings, and fault type. [ABSTRACT FROM PUBLISHER]

This paper develops and experimentally tests the performance of a digital interconnection protection for grid-connected wind energy conversion systems (WECSs). The developed protection is constructed by two frequency frames to process voltages and currents measured at the point-of-common-coupling (PCC). The first frequency frame is set to process the d-q-axis components of the instantaneous 3\phi apparent powers ( sd and sq) determined at PCC. This processing of sd and sq aims to extract their high-frequency subband contents in order to detect the islanding condition. The second frequency frame is set to extract the high-frequency contents (magnitudes and phases) present in the $3\phi$ currents flowing through PCC. These high-frequency contents provide signature information for detecting faults occurring on either side of PCC. The multiframe digital interconnection protection is implemented for performance evaluation on two different WECSs operated in grid connection. Performance results show accurate and reliable detection and identification of the islanding condition and faults occurring on either side of PCC. In addition, performance results show that the multiframe digital interconnection protection has minor sensitivity to the type, structure, ratings, and levels of power delivery to the host grid. [ABSTRACT FROM PUBLISHER]

This paper presents the real-time implementation and experimental performance evaluation of the phase-based digital protection against arc flash faults. The tested digital protection is based on extracting the high frequency components from fault currents triggered by an arc flash fault. The desired high frequency components are extracted using a filter bank that is composed of five exponentially modulated Kaiser window-based high-pass filters (HPFs). The structure of the used filter bank is selected to ensure extracting high frequency components with nonstationary phases, which represent a unique signature of arc flash faults. Such a signature allows detecting and identifying arc flash faults, as well as initiating responses against such events. The performance of the phase-based digital protection is experimentally evaluated for a laboratory $3\phi$ system that supplies linear, nonlinear, and dynamic loads. Test results demonstrate fast, accurate, and reliable detection, identification, and response to arc flash faults. In addition, test results show that the phase-based digital protection has minor sensitivity to the type of arc flash fault or supplied loads. [ABSTRACT FROM PUBLISHER]

This paper proposes a new approach for detecting and identifying arc flash faults in power systems. The proposed approach is structured to extract the phases of transient frequency components present in arc flash fault currents. The desired phases can be extracted by processing fault currents using a modulated filter bank that is composed of high-pass finite impulse response (FIR) filters. These filters are designed by using the Kaiser window method to achieve linear phase responses. Extracting the phases of transient frequency components, present in arc flash fault currents, can provide signature information for accurate and fast detection and distinguish of an arc flash fault. The proposed phase-based approach is implemented for off-line testing to evaluate its performance. Test cases of parallel and series arch flash faults are conducted for supplying linear, nonlinear, and dynamic loads. Simulation and off-line results demonstrate the validity, accuracy, speed, and reliability of the phase-based approach to detect and distinguish arc flash faults with minor sensitivities to the load type and arch flash type. [ABSTRACT FROM AUTHOR]

Ground faults are among the major causes of disrupting the safe, secure, stable, and profitable operation of doubly fed induction generator (DFIG) based wind energy conversion systems (WECSs). On one hand, minimizing the possible damage in a DFIG-based WESC, caused by ground faults, requires accurate detection and fast response of ground protective devices. On the other hand, the responses of ground protective devices are highly dependent on ground currents and potentials, especially during high-impedance ground faults. This paper investigates the influences of grounding configurations on the responses of ground protective devices used in DFIG-based WECSs during high-impedance ground faults. Investigated influences are observed through the ability of ground protective devices, used in DFIG-based WECSs, to quickly and accurately respond to high-impedance ground faults for different grounding configurations. In this paper, the solid, low-resistance, high-resistance, and open grounding configurations are tested for DFIG-based WECS in order to establish comprehensive investigations. The results of the investigations show that the responses of ground protective devices vary depending on ground fault currents, which can have different levels due to the grounding configuration. Moreover, the results of the investigations reveal that the frequency-selective grounding configuration can offer a minimum impact on the responses of ground protective devices used in DFIG-based WECSs. [ABSTRACT FROM AUTHOR]

The growing interest in clean and sustainable electric energy pushes toward increasing the interconnection of wind energy conversion systems (WECSs) to utility grids. The designs of the majority of WECSs employ power electronic converters (PECs), which generally have nonlinear and switched characteristics. The characteristics, operation, and control of PECs in WECSs can result in nonconventional voltage–current behaviors during faults. This paper investigates the voltage–current behaviors during faults that occur in grid-connected WECSs. Two types of WECSs are considered in this paper, which are the doubly fed induction generators and permanent magnet generator based WECSs. The voltage–current behaviors are investigated in experimentations for different faults occurring in different parts of the test grid-connected WECSs. [ABSTRACT FROM PUBLISHER]

Photovoltaic (PV) systems have become a popular type of distributed generation units (DGUs) for small and medium levels of renewable energy generation. When grid connected, these DGUs are designed and operated to deliver electric power to their host grid through power electronic converters. The nonlinear and switched natures, along with the control actions, of these PECs can influence the voltage–current behaviors during faults in grid-connected PV systems. This paper experimentally investigates the voltage–current behaviors during faults occurring in grid-connected PV systems. Results of these investigation show that voltages and currents at the point-of-common-coupling (PCC) experience changes in their magnitudes and harmonic distortions due to faults occurring on both sides of PCC. These results can be incorporated in the improvement of the accuracy and reliability of protective devices used for grid-connected PV systems. [ABSTRACT FROM PUBLISHER]

One of the requirements for safe, stable, sustainable, and profitable operation of doubly fed induction generators (DFIGs)-based wind energy conversion systems (WECSs) is the accurate and reliable protection against electrical faults, in particular, ground faults. The performance of protective devices employed to achieve this requirement is highly dependent on the grounding configuration of the DFIG-based WECS. This paper investigates impacts of the grounding configuration on the performance of protective devices used to protect DFIGs-based WECSs from electrical ground faults. Investigated grounding configurations include solid grounding, low-resistance grounding, high-resistance grounding, and no grounding. This paper also investigates the use of a capacitor in parallel with a low resistance, as a grounding configuration, to limit ground potentials, reduce ground currents, and minimize impacts on responses of ground protective relays. The impacts of the grounding configurations on protective devices are observed through their ability to identify faults, as well as their speed to respond to identified faults. Simulation and experimental results reveal that adequately designed low-resistance grounding offers the minimum impacts on protective devices used for ground protection of DFIG-based WECSs. [ABSTRACT FROM PUBLISHER]

This paper presents the implementation and performance evaluation of an embedded digital protection for three-phase $(3\phi)$ interior permanent-magnet synchronous motor (IPMSM) drives. The presented digital protection is established through extracting the high-frequency subband present in the $d$– $q$-axis components of the currents drawn by the protected IPMSM. The desired high-frequency subband is extracted using the wavelet packet transform (WPT) from the $d$– $q$-axis current components, which are obtained from the controller of the IPMSM drive. The extracted high-frequency subband contains signature information that allows detecting and classifying transient disturbances into fault and nonfault events. The presented method is insensitive to the variations in the drive parameters, loading levels, nature of electrical faults (open circuit or short circuit), and operation of the drive controller. These features of the $d$– $q$ WPT-based digital protection simplify its implementation and facilitate its embedding within the controller of the IPMSM drive. The performance of the $d$– $q$ WPT-based digital protection is experimentally evaluated on a laboratory 5-hp IPMSM drive for various fault and nonfault events. Test results demonstrate fast, accurate, and reliable detection, classification, and response to fault and nonfault events. [ABSTRACT FROM PUBLISHER]