Ground Fault Protection Research Articles

Development of the self-learning machine for creating models of microprocessor of single-phase earth fault protection devices in networks with isolated neutral voltage above 1000 V

The paper proposes the development of a self-learning machine for creating models of microprocessor-based single-phase ground fault protection devices in networks with an isolated neutral voltage higher than 1000 V. Development of a self-learning machine for creating models of microprocessor-based single-phase earth fault protection devices in networks with an isolated neutral voltage higher than 1000 V. allows to effectively implement mathematical models of automatic change of protection settings. Single-phase earth fault protection devices.

Impact of Power-Electronic Sources on Transmission Line Ground Fault Protection

Power-electronic sources, such as Type 3 wind turbine generators and static synchronous compensators (STATCOM), interface to the grid through, partial- or full-scale, and power converters that have inherently fast switching capability to control their output current during short circuits. The short-circuit current is a function of the specific converter control algorithm and differs significantly from the conventional rotating machine sources without converter interfaces. Therefore, if a transmission-line protection scheme is designed for conventional sources, (not taking into account these differences in short-circuit current characteristics), reliability can be at risk. Using real-life short-circuit currents on lines supplied by sources having a power converter interface, this paper illustrates the reliability risk to conventional line protection schemes, in particular, to those which use negative-sequence quantities for the detection of unbalanced faults. This paper discusses the protection schemes, adopted by BC Hydro–a large Canadian Electric Utility, for transmission lines interconnecting Type 3 wind turbine and STATCOM sources. Their application for ground faults is independent of the converter control algorithm as long as the source is interconnected to the grid via a transformer which is a source of zero-sequence current.

Modeling and Experimental Verification of a 100% Stator Ground Fault Protection Based on Adaptive Third-Harmonic Differential Voltage Scheme for Synchronous Generators

In this paper, a novel adaptive stator-ground fault protection scheme based on third-harmonic differential voltages is implemented on a lab scale synchronous generator. The lab scale generator is used to emulate the fault characteristics of industrial generators along the stator windings. Simulations based on finite element analysis methods were used to design and tune the laboratory testbed. Experimental results prove the expected fault characteristics as well as fault detection capability of the adaptive stator-ground fault protection scheme.

Ground Fault Protection methods for Distribution Systems

The system grounding method option has a direct influence on the overall performance of the entire medium voltage network as well as on the ground fault current magnitude. For any kind of grounding systems: ungrounded system, solidly and low impedance grounded and resonant grounded, we can find advantages and disadvantages. A thorough study is necessary to choose the most appropriate grounding protection system. The power distribution utilities justify their choices based on economic and technical criteria, according to the specific characteristics of each distribution network. In this paper we present a medium voltage Portuguese substation case study and a study of neutral system with Petersen coil, isolated neutral and impedance grounded.

Effect of Neutral Grounding Protection Methods for Compensated Wind/PV Grid-Connected Hybrid Power Systems

The effects of the wind/PV grid-connected system (GCS) can be categorized as technical, environmental, and economic impacts. It has a vital impact for improving the voltage in the power systems; however, it has some negative effects such as interfacing and fault clearing. This paper discusses different grounding methods for fault protection of High-voltage (HV) power systems. Influences of these grounding methods for various fault characteristics on wind/PV GCSs are discussed. Simulation models are implemented in the Alternative Transient Program (ATP) version of the Electromagnetic Transient Program (EMTP). The models allow for different fault factors and grounding methods. Results are obtained to evaluate the impact of each grounding method on the 3-phase short-circuit fault (SCF), double-line-to-ground (DLG) fault, and single-line-to-ground (SLG) fault features. Solid, resistance, and Petersen coil grounding are compared for different faults on wind/PV GCSs. Transient overcurrent and overvoltage waveforms are used to describe the fault case. This paper is intended as a guide to engineers in selecting adequate grounding and ground fault protection schemes for HV, for evaluating existing wind/PV GCSs to minimize the damage of the system components from faults. This research presents the contribution of wind/PV generators and their comparison with the conventional system alone.

Advanced Generator Ground Fault Protections in Pulp and Paper Mill Applications

Ground faults in field/rotor and generator stator circuits are serious events that can lead to damage, costly repair, extended outages, and loss of revenue. This paper explores advances in field/rotor circuit ground fault and stator ground fault protection. These advanced protection strategies employ ac injection, ground differential protection, and the use of hybrid grounding to reduce both internal generator ground fault levels and facility ground levels in utility-paralleled operating modes.

Photovoltaic ground fault detection recommendations for array safety and operation

PV faults have caused rooftop fires in the United States, Europe, and elsewhere in the world. One prominent cause of past electrical fires was the ground fault detection “blind spot” in fuse-based protection systems discovered by the Solar America Board for Codes and Standards (Solar ABCs) steering committee in 2011. Unfortunately, while a number of alternatives to ground fault fuses have been identified, there has been limited adoption or historical use of these technologies in the U.S. Analytical and numerical SPICE simulations were conducted for a wide variety of ground faults and array configurations to understand the limitations of fuse-based ground fault protection in PV systems and determine proper trip settings for alternative GFPDs. Simulation results were compared with experimental measurements on arrays to validate the SPICE model as well as provide direction on proper thresholding of residual current detector (RCD), current sense monitor (CSM) and isolation monitor (Riso) devices based on historical fault current data. We argue the combination of simulation results with historical data indicates robust settings are possible for each of these technologies to minimize unwanted tripping events while maximizing PV fault detection.

Applicability of a Hall Sensor in Directional Ground Fault Protections of MV Cable Networks with no-effective Earthing

Paper presents and discusses results of analysis and research on the possibility of use of the Hall sensor as measuring element in directional ground fault protection. The considerations have been carried out for the new balance transformer structure with magnetic shielding. Its applicability has been confirmed by tests under real ground faults in MV networks of 6 kV and 20 kV with no-effective earthing. On the basis of the investigated results appropriate practical conclusions have been formulated.DOI: http://dx.doi.org/10.5755/j01.eie.22.5.16339

A novel single phase grounding fault protection scheme without threshold setting for neutral ineffectively earthed power systems

The setting values of thresholds for fault feature parameters are critical in all kinds of protection schemes. When the detected feature parameter value exceeds the setting value, the protection will trip. However, the setting value based conventional protection schemes sometimes cannot satisfy the protection requirements of neutral ineffectively earthed power systems (NIEPS) due to wide variations in operating conditions and the complexities of fault cases. In this paper, a novel single phase grounding fault protection scheme without threshold setting is proposed. The fault detection is achieved based on operating states rather than setting values. A fuzzy c-means algorithm is used to divide the operating state of the protected feeder into non-fault states and fault states. The cluster center of each state is then obtained by classifying the historical feature samples of the protected feeder extracted under various operating conditions into their corresponding states in a constructed multi-dimensional fault feature space. The distances between the detected feature samples and the cluster centers of the non-fault and the fault states are calculated. If the distance to the fault state is shorter than that to the non-fault state, a fault is detected. Otherwise, the feeder is considered normal. A PSCAD/EMTDC simulator is used to simulate a 35 kV NIEPS under various operating conditions, non-linear loads, and complex fault cases. Results show that the proposed single phase grounding fault protection scheme without threshold setting can protect the system correctly under all kinds of faults.

Comparative performance study of the Hall sensor based directional ground fault protection in MV mining network with ineffective earthing

Comparative performance study of the Hall sensor based directional ground fault protection in MV mining network with ineffective earthing

Adaptive 100% Stator Ground Fault Protection Based on Third-Harmonic Differential Voltage Scheme

The paper presents a new adaptive 100% stator ground protection for high-impedance-grounded (HIG) synchronous generators. This is done by first examining reliability, that is, dependability and security of the most prominent conventional 3rd-harmonic voltage schemes. Using field data from various capacity industrial generators, it is shown that the conventional 3rd-harmonic differential voltage scheme, while being dependable, lacks security. Using the same field data, it is shown that the new adaptive scheme is a highly secure and sensitive scheme. Moreover, the new adaptive scheme is a zero-setting scheme which does not require any setting calculations, 3rd-harmonic voltage testings, or additional hardware.

DC‐side fault detection for photovoltaic energy conversion system using fractional‐order dynamic‐error‐based fuzzy Petri net integrated with intelligent meters

Fault occurrence or voltage disturbance, such as mismatch operations or electrical faults caused by structural changes in photovoltaic (PV) panels, local/remote faults, or heavy load operation, can disturb a PV energy conversion system (PVECS) on both the DC and AC sides. On the AC side, any serious disturbance can be isolated using power fuses, overcurrent protection and ground-fault protection devices. Therefore, the authors propose the use of fractional-order dynamic-error-based fuzzy Petri net (FPN) to detect disturbance events in a microdistribution system. PV energy conversion depends on solar radiation and temperature, and a maximum power point tracking control is used to maintain stable output power and voltage to microdistribution loads. When the desired maximum power is estimated, a bisection approach algorithm is used to regulate the output voltage of the PVECS by adjusting the duty ratios of a buck–boost converter. The maximum power drops, which are compared with meter-reading power from intelligent meters, are used to detect faults on the DC side. Then, fractional-order dynamic errors between the desired and estimated powers and a FPN are employed to detect faults. For a small-scale PVECS, computer simulations are conducted to show the effectiveness of the proposed model.

Multi-objective optimization of the balancing of phases in primary distribution circuits

The primary distribution systems are among the more unbalanced three-phase networks. The unbalance of the phase currents causes two fundamental problems in the circuits: the increase of energy losses in the primary feeders and the presence of a high neutral current in normal operating status that makes it difficult the detection of ground faults by corresponding protections. These circuits are always protected at the substation. Nevertheless, other protections can also be located downstream in some sections or laterals of the circuit. Additionally, a circuit or some section of it can be supplied from another adjacent circuit in emergency conditions. In all the points where a ground fault protection is used, the maximum current of imbalance must be reduced to a minimum considering the several operating conditions that can change the circuit topology. This paper formulates the problem of phase balancing as a multi-objective optimization problem that minimizes: the neutral current at the desired points of the circuit, the energy losses in the primary feeders and the number of reconnected elements to achieve these objectives. The Non-dominated Sorting Genetic Algorithm (NSGA-II) has been used to develop the optimization application, which has shown a very successful performance in the solution of the phase balancing problem. A test example with all the needed data is solved to show the advantages of the presented approach.

Ground-Fault Protection of Personnel: The Field Applications of a Class C GFCI in a Crude Oil Refinery

Most Refineries, Drilling Platforms, and chemical plants are equipped with receptacles used for powering equipment. This can present a shock hazard; therefore, the National Fire Protection Association (NFPA) and Occupational Safety and Health Administration (OSHA) require ground-fault circuit interrupters (GFCIs) on all receptacle powering equipment used by personnel. However, these GFCIs are not part of the building?s permanent wiring. Due to the lack of GFCIs at voltages above 240 V, both the NFPA and OSHA require employers to implement the assured equipment-grounding conductor program for all temporary wiring installations.

Transition and verification of ground fault protection method in Hokuriku Shinkansen line

The electrical discharge gaps called S type horn are applied to the ground fault detection and protection in AC traction power supply system for high speed railway called Shinkansen. In this method, the earth resistance of the steel pipe pillar is an important factor for the ground fault protection by the electrical discharge. In this study, the analyses of the transient characteristics of grounding fault are carried out by using EMTP, and the ground resistance value required to trigger discharge at S type horn was calculated. Moreover, the protection effect of a discharge gap called GP the substation equipment that is a discharge gap which is inserted between rails and substation mesh is evaluated.

Cooperative Operation of Superconducting Fault-Current-Limiting Cable and SMES System for Grounding Fault Protection in a LVDC Network

This paper investigates grounding fault protection characteristics in a novel low-voltage direct-current power transmission, distribution, and utilization network integrated with multiple fault-current-limiting (FCL) superconducting cables (SCs) and multiple superconducting magnetic energy storage (SMES) devices. The effectively integrated system is highlighted with a self-acting fault current limitation feature of the FCL SC and a fast-response grid voltage protection feature of the SMES. The simulation results show that the cooperative operations of the FCL SC and the SMES are favorable for achieving advanced fault current limitation, fault-ride-through capability enhancement and critical load protection during a grounding fault.

On the Design and Capacity of a Grounding Configuration for Grid-Connected <roman>DGUs</roman>

Established standards and industrial codes, for interconnecting distributed generation units (DGUs), address voltage and frequency changes, levels and quality of injected power, islanding conditions, and protection. However, these standards and codes do not clearly address the grounding configurations for grid-connected DGUs. One of the challenges related to the grounding configuration for DGUs is the harmonics generated by power electronic converters employed in DGUs. These harmonics can raise the ground potentials and disrupt the function of ground fault protection. This paper develops and tests a frequency-selective grounding configuration for grid-connected DGUs. The developed grounding configuration offers limiting ground potentials and ground fault currents, while imposing negligible impacts on the function of ground fault protective devices. The frequency-selective grounding configuration is designed and tested for two wind energy conversion systems and a photovoltaic system. Test results show that the developed grounding configuration achieves its objectives with negligible impacts on the grounded DGU and its ground fault protection.

Comparative Evaluation of DC Fault-Mitigation Techniques in Large PV Systems

Over the past five years, the industry has learned that photovoltaic (PV) system fault protection must be refined to include additional fault protection not provided in most existing PV system installations. Using a failure mode and effects analysis scoring system, this study evaluated the risk associated with 13 faults that could be missed by typical PV System fault protection and the effectiveness of 20 different solutions in containing these faults. Based on the analysis in this study, the ground fault protection in all new PV systems should be capable of detecting any ground fault with 50 mA or more of fault current to address the highest risk faults. For resistively grounded systems, both high- and low-risk faults can be prevented by using a combination of combiner box arc-fault circuit interrupt (AFCI) protection and either continuous isolation monitoring or inverter input differential current protection. For solidly grounded systems, combiner box AFCI protection should be paired with either higher sensitivity current detectors in the ground bond or inverter input differential current protection.

Insights Into Applications of IEEE Standards for Ground-Fault Protection in Industrial and Commercial Power Systems

Insights Into Applications of IEEE Standards for Ground-Fault Protection in Industrial and Commercial Power Systems

On-line stator ground-fault location method for synchronous generators based on 100% stator low-frequency injection protection

Locating stator-winding ground faults accurately is a very difficult task, especially in high-impedance grounded generators. Through the conventional measurements of power plants, obtaining the precise location of these defects in on-line operating conditions is not possible, because the fault resistance is unknown. This paper presents a general algorithm for locating stator-winding ground faults in on-line operating conditions, based on the measurements provided by the 100% ground-fault low-frequency injection protection, and other available measurements. Some simplifications are applied to the general algorithm, and a simplified method is also presented for generators with especially low capacitance-to-ground, whose implementation in modern protective relays is more simple. The location through the general algorithm, and the simplified algorithms, has been validated by simulation and experimental tests, for several fault resistance values at different points of the stator winding. These algorithms assure an acceptable accuracy for a wide range of fault resistance values and locations, without the need of any additional equipment.