Power System Fault Analysis and Protection

To date, the skin effect has not been considered in the analysis of network fault response and the design of protection systems for DC networks. However, the naturally high resonant frequencies of some modern marine and aerospace electrical networks under electrical fault conditions suggest that skin effect should be investigated more closely. The studies reported in this paper compare the system fault response for both a conventional circuit model and a model incorporating the skin effect. The results show a noticeable difference, demonstrating that in some cases the skin effect should be considered for studies of this nature. The paper builds upon these findings by investigating the impact on protection system operation, making recommendations for associated modelling and simulation practices. (5 pages)

Since 1988, the system relay engineer of Kansas Power & Light Gas Service has served as a guest lecturer for the course on fault analysis and protection of power systems at Kansas State University. He meets the class five times during the semester. Two of these visits are field trips. In the other three visits he discusses power systems protection from a practicing engineer's point of view. He also discuss a practical design problem prepared for this class. The details of the course, the design project, and other activities are described. The benefits of such cooperation between university and industry are outlined. The main objectives of this course are to: make the students familiar with symmetrical components and fault analysis; make the students familiar with computer methods for fault analysis; make the students familiar with directional overcurrent, differential, distance, and pilot protection; impart practical knowledge on protection to the students; are prepare students for projection-related jobs in the utilities.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Distribution transformers are a vital component of electrical power transmission and distribution system. Frequent Monitoring transformers faults before it occurs can help prevent transformer faults which are expensive to repair and result in a loss of energy and services. The present method of the routine manual check of transformer parameters by the electricity board has proven to be less effective. This research aims to develop a low-cost protection system for the distribution transformer making it safer with improved reliability of service to the users. Therefore, this research work investigated transformer fault types and developed a microcontroller-based system for transformer fault detection and protection system using GSM (the Global System of Mobile Communication) technology for fault reporting. The developed prototype system was tested using voltage, current and temperature, which gave a threshold voltage higher than 220 volts to be overvoltage, a load higher than 200 watts to be overload and temperature greater than 39 degrees Celsius to be over temperature was measured. From the results, there was timely detection of transformer faults of the system, the transformer protection circuits were fully functional, and fault reporting was achieved using the GSM device. Overall, 99% accuracy was achieved. The system can thus be recommended for use by the Electricity Distribution Companies to protect distribution transformers for optimal performance, as the developed system makes the transformers more robust, and intelligent. Hence, a real-time distribution transformer fault monitoring and prevention system is achieved and the cost of transformer maintenance is reduced to an extent.

A fault protection and location method for ungrounded dc traction power systems is presented in this paper. Many dc traction power systems have an ungrounded power circuit to increase the leakage path resistance. Although ungrounded systems can continue operating with a single ground contact, unlike solid- or low-resistance grounded systems, because of the very low fault current, a second ground fault in another pole will result in a line-to-line fault that could cause significant system damage. However, it is difficult to detect the first ground contact due to the low ground current and even harder to locate because it can be seen by many detectors in the network. The proposed scheme in this paper uses a probe unit to detect and locate the first single ground fault in ungrounded traction power systems. The probe unit applies probe voltage to detect the fault and, once the fault is detected, analyzes the response to dc or swept-frequency ac probe voltage to locate the fault. The proposed concepts have been verified with computer simulations and hardware experiments and demonstrated a successful performance.

In this paper, we adopt a novel approach to the fault analysis of complex electric power systems. Electric power system is one of the most complex artificial systems in the world. Its ...

With the high penetration of Renewable Energy Sources (RES) in power systems, the short-circuit levels have changed, creating the requirement for altering or upgrading the existing switchgear and protection schemes. In addition, the continuous increase in power (accounting both for generation and demand) has imposed, in some cases, the need for the reinforcement of existing power system assets such as feeders, transformers, and other substation equipment. To overcome these challenges, the development of superconducting devices with fault current limiting capabilities in power system applications has been proposed as a promising solution. This paper presents a power system fault analysis exercise in networks integrating Superconducting Cables (SCs). This studies utilized a validated model of SCs with second generation High Temperature Superconducting tapes (2G HTS tapes) and a parallel-connected copper stabilizer layer. The performance of the SCs during fault conditions has been tested in networks integrating both synchronous and converter-connected generation. During fault conditions, the utilization of the stabilizer layer provides an alternative path for transient fault currents, and therefore reduces heat generation and assists with the protection of the cable. The effect of the quenching phenomenon and the fault current limitation is analyzed from the perspective of both steady state and transient fault analysis. This paper also provides meaningful insights into SCs, with respect to fault current limiting features, and presents the challenges associated with the impact of SCs on power systems protection.

A high voltage DC (HVDC) parallel electric power system (EPS) is studied in this paper. The HVDC parallel EPS provides uninterrupted onboard power supply with better performance and higher reliability. Four different frameworks of the parallel EPS are studied. The performance, complexity and reliability of the four frameworks are compared, and the "annular parallel connection" structure is selected as the best framework for the EPS. To avoid collapse of the parallel EPS, the fault detection and protection system is designed. Several sensors, breakers and relays are mounted in the EPS. The common faults of the HVDC parallel EPS are analyzed and corresponding solutions are proposed. The framework of the parallel connection and the fault analyses can provide an effective solution for the development in the HVDC EPS for the MEA.

Micro grid is a localized grouping of distributed generation, storage system and load, all operating as a single system and providing electric power and heat. It can either operate in parallel to the main grid or in an islanded mode in case of faults in the grid. However, technical challenges of current practices include distribution protection, control and fault diagnosis, protection strategies and load management. This paper demonstrates the development of advanced automated fault detection, diagnosis and protection system and algorithms for the micro grid system using fault semantic network.

Faults of the traction power system threaten the reliability and safety seriously in the urban rail transit. This paper establishes the state space average (SSA) model of the traction power system to explore the effects caused by the short-circuit fault and open-circuit fault. The SSA model solutions prove that the short-circuit fault affects train operations obviously. While the open-circuit fault affects little owing to the unilateral power supply mode. Moreover, based on the SSA model, traction network current distributions of metro lines can be predicted for protections, which is conductive to improve the reliability of traction power system.

In recent years, the concept of solid-state transformers (SSTs) has evolved to be one of the front runners in the development and realization of a smart grid. The recent strides in the field of medium voltage wide bandgap semiconductor devices and the availability of 10 kV SiC MOSFETs and 15 kV SiC IGBTs have made it possible to build medium voltage SSTs using simple converter topologies. With the SST interfacing two grids, it forms a crucial juncture in the electrical distribution system which necessitates a high fault tolerance capacity of the SST during grid fault conditions. In addition, the grids need to be protected from any faults or abnormal operation in the SST which makes it imperative to implement different fault protection considerations on the SST. In this paper, these fault protection systems are studied in terms of their breaking time, breaking current/voltage, and fault coordination. The protection schemes are analyzed on a Gen3 10 kV SiC MOSFETs based Mobile Utility Support Equipment Solid-State Transformer (MUSE-SST) which is developed at FREEDM Systems Center aimed at interconnecting a 4.16 kV grid to a 480 V grid or load. Simulation results and are provided to evaluate the protection schemes. Initial experimental test results are also provided.

Heavy-load multi-wheel electric vehicles are deemed to have significant potential by their superior fuel utilization efficiency and low-carbon environmental benefits. The DC power systems with relatively high bus voltages are adopted for HLMWEVs and inevitable to faults under harsh operating conditions, which threaten the safety and stability of the system, even lead to equipment damage and personnel injuries. Therefore, it is essential to implement comprehensive fault protection for HLMWEV DC power systems, encompassing both local-level and system-level protection. As means of local-level fault protection, fuses play a crucial role in ensuring the reliability and safety of power system operations. In order to minimize impacts of the fault or to avoid other undesirable situations in the system, fuses should totally clear the fault in the designed time while ensuring uninterrupted operation of healthy feeders. However, due to the flexible topology, diverse operating conditions, and complex fault current characteristics, it is a significant challenge to achieve the selectivity and sensitivity of fuses. This paper proposes a novel approach by means of additional branch inductors and bus capacitors to coordinate fuse protection actions and improve fault response performance. The principle of the proposed approach is introduced and the selection criteria for these components are discussed in detail. By modeling and simulating the DC power system of HLMWEVs, the fault clearing time of feeder protection is analyzed to validate the proposed method. The results demonstrate that the proposed approach effectively enhances the selectivity and sensitivity of feeder protection.

SUMMARY This paper presents a model for the analysis of internal faults of synchronous generators with multiple parallel connection paths for phase. Several kinds of faults between different portions of the stator windings (and ground, if the case) can be described in the subtransient time frame. Data necessary for the model derive from the electromagnetic design of the machine, as well as from details on equivalent parameters of the external grid and from the neutral connection characteristics. Such modeling procedure allows accurate insight of currents in windings and terminals, exploring each possible fault configuration. In the second part of this work, the developed model will be applied to assess the validity and to define possible improvements of conventional protection configurations against internal faults. Copyright © 2013 John Wiley & Sons, Ltd.

Circuit breakers are widely applied in power system protection by interrupting fault current. Among all types of circuit breakers, we focus on the modeling of thermal-magnetic circuit breakers in this paper. Data regression and curve fitting methodologies are employed to study the manufacturer's time/current data. A brand new simulation model that contains probability tools is developed to realistically describe the tripping characteristics, and a product failure rate is also considered to reflect possible circumstances in real-world application of the thermal-magnetic circuit breakers. A simulation testbed system is included for the purposes of illustration and validation.

Fault protection and real-time monitoring of Satellite Electrical Power Systems (SEPS) are of importance for the advancement of modern satellite systems of high power, compact sizing and long lifespan. Conventional protection methods could handle the overcurrent faults but lack flexibility in fault clearance time. With these important considerations, a compact and programable Silicon Carbide (SiC) power MOSFET based DC circuit breaker module is developed to not only handle multiple levels of overcurrent faults with suitable time-delay protection scheme, but also provide the real-time monitoring of circuit breaker status by using the Long Range (LoRa) and Internet of Things (IoT) Technology. The proposed module has been implemented and its effectiveness was tested and confirmed in laboratory under various overcurrent fault conditions.

The power electronic converters have a heavily influence in our life-style, since they are today used everywhere in-home applications, office, medicine, industry, and energy transmission machines and processes. The power electronic systems are based on fast-switching power semiconductors, such as diodes, mosfets, igbts, etc. These power devices represent the fragile part in a power electronic converter. Thus, to ensure safety and reliability of the power conversion system, a fault detection method must be provided. When a failure occurs, the fault detection and protection system become the most important function of the converter control unit. If the fault management is not adequate, the entire converter can be totally destroyed, causing catastrophic effects on the entire power conversion system. Accordingly, fault detection, classification, and diagnoses for all power electronic converters, including three phase rectifiers, three phase inverters, DC-DC converters and AC-AC converters, have to be investigated. In this paper, the fault analysis of the 3-phase 5-level E-Type Converter (3Φ5L E-Type Converter) is addressed. The 3Φ5L E-Type Converter is proposed for grid connected applications. All possible converter semiconductor switches and diodes faults are theoretically analyzed. The fault effects, the detectability and the safety shutdown actions are identified and summarized. The analysis is covered by simulation results performed in MATLAB/Simulink. The control algorithm has been implemented in FPGA using LabVIEW environmental. The experimental tests have been performed on the 20kVA prototype multilevel converter in order to validate the proposed analysis.