Fault Protection System Research Articles

Dynamic response of wind energy conversion systems under various faults

One of the most important features of energy generation sources is robustness of their structure against faults. Wind energy conversion systems (WECSs) are generally subjected to occurrence of various faults. Many modelling techniques which have been already introduced for the modelling of the faults or observing the influences of the faults cannot be considered wide–ranging to include any fault at any point of the WECS. On the other hand, for the purpose to explore the impacts of faults on several components of the WECS and probably improving the future design of it, a type of model is required in which mechanical and electrical parts are modelled properly with some details. In this paper, a comprehensive dynamic model for the WECS is presented by which a variety of faults such as sensors, actuators and power grid faults can be studied and effects of these faults on voltage, current and other signals of the WECS can be investigated. In addition, the dynamic model described by this paper can be applied simply to design the fault detection, fault tolerant control and protection systems of the WECS.

Heat Transfer Simulation to Liquid Nitrogen from HTS Tapes at the Overload Currents

Knowledge of HTS materials behavior at overload currents is important to design fault current limiters or fault protection systems of electro-technical devices. There are sharp voltage peaks and voltage oscillations during rectangular current pulses (DC current) on HTS tapes cooled by liquid nitrogen. It is common knowledge that a homogeneous liquid can withstand certain amount of overheating before switching to the boiling phase. In the liquid nitrogen during the increase of the heat flux there is superheating (temperature overshoot) and boiling hysteresis takes place. We explain voltage peaks and voltage oscillations by the hysteresis phenomenon in boiling nitrogen during the increase and decrease of the heat flux in the nitrogen which is a result of current redistribution in the HTS tapes. Based on the measurements of voltage and temperature of the HTS tapes during current overload and numerical analysis of the process we estimated the heat-transfer characteristics from the HTS tapes to liquid nitrogen. We also obtained the information about limiting superheating of the liquid nitrogen. The influence of covers of the HTS tapes on superheating of the nitrogen is also discussed.

Sub-Module Controller and Sub-Module Steady-State Test Platform Design for MMC-HVDC

Compared with Line-Commutated-Converter High Voltage Direct Current (LCC-HVDC), the primary and secondary systems of modular multilevel converter based HVDC (MMC-HVDC) are more complicated. And control and protection function of sub-module controller (SMC) have great influence on the operation of MMC-HVDC system. This paper investigates the design method of SMC and sub-module (SM) steady-state platform. First, the structure of the primary system and the electrical parameters of the 21-level MMC-HVDC are designed. Second, the architecture of the control system and SM fault protection strategy are proposed, and the control program is developed and debugged. Then SM steady-state test platform and the relevant control and protection are designed. Finally, the steady-state test and the system test of the physical MMC-HVDC simulation system are conducted. The test result shows that the sub-module is of good property and SMC can communicate with upper control layer efficiently, control and protect the SM efficiently.

Investigate dynamic and transient characteristics of microgrid operation and develop a fast-scalable-adaptable algorithm for fault protection system

A microgrid (MG) system mainly consists of renewable energy sources, distributed generators, loads and energy storage devices. Development of the microgrid brings some emerging challenges. One of them is a microgrid fault protection system. In order to develop an optimal fault protection algorithm, this paper surveys dynamic and transient behaviours with respect to two operation modes of a microgrid, namely, islanded and grid-connected modes. Modelling and simulation of the MG's operation are performed by PSCAD/EMTDC software. A surveyed typical MG structure includes one dispatchable power source of microturbine (μT) system, another non-dispatchable power source of photovoltaic (PV) generation system and one battery power conditioning system (PCS). Whereas dynamic characteristics of the MG are investigated in cases of power change of loads or sources and motor starting, transient properties are surveyed through staged fault tests (e.g. single-phase and three-phase to ground faults) and the MG's operation transition between grid-connected and islanded modes. Simulation results are compared to actual experiment results performed at a 380V microgrid at Institute of Nuclear Energy Research (INER), Taiwan. From achieved dynamic and transient properties, this paper proposes a fast-scalable-adaptable (FSA) computing algorithm for a fault protection system to improve MG's reliability and adaptability operation. This new algorithm uses parameters of current, voltage and angle phase along with a communication network to protect online the microgrid. The proposed algorithm can solve challenging problems of high penetration of inverter-based distributed generators, reduced fault current values and non-directional power flow. Moreover, the algorithm can get a critical fault clearing time within one fault cycle, high accuracy and reliability for fault detection, identification of different types of faults and optimal isolation of faulted zones. Simulation and experiment results validate the proposed fast-scalable-adaptable fault protection algorithm.

Formal validation of fault management design solutions

The work presented in this paper describes an approach used to develop SysML modeling patterns to express the behavior of fault protection, test the model's logic by performing fault injection simulations, and verify the fault protection system's logical design via model checking. A representative example, using a subset of the fault protection design for the Soil Moisture Active-Passive (SMAP) system, was modeled with SysML State Machines and JavaScript as Action Language. The SysML model captures interactions between relevant system components and system behavior abstractions (mode managers, error monitors, fault protection engine, and devices/switches). Development of a method to implement verifiable and lightweight executable fault protection models enables future missions to have access to larger fault test domains and verifiable design patterns. A tool-chain to transform the SysML model to jpf-statechart compliant Java code and then verify the generated code via model checking was established. Conclusions and lessons learned from this work are also described, as well as potential avenues for further research and development.

Fault Protection and Overload Diagnosis in a Regulated High-Voltage Power Supply

Regulated high-voltage power supplies (RHVPSs) have been developed at Institute for Plasma Research and utilized for neutral beam and radio-frequency heating applications of the steady-state superconducting tokamak (SST-1) up to 80-kV, 130-A rating. They were developed in-house and are being delivered to different research institutes for various applications.The RHVPS delivers power to various loads at the megawatt level. These loads have very low fault energy tolerance; therefore, fault protection is mandatory. In addition to this, at each stage of the power transformation/conversion, a special diagnosis is necessary to protect the power supply components. Also, the output fault protection has to be done in such a manner that fault energy is not more than 10 J. In fault conditions, the output has to be turned off within 2 μs. Having these requirements, an output fault-protection system has been developed with suitable sensors and to manage fast turn off, choosing appropriate components.The multiple-secondary transformers (two of them, each at a 5.6 MV·A rating with 40 outputs) are used at the front end of the RHVPS. They may become damaged for overload at any one of their secondaries, while remaining secondaries carry much less current or no current. Such a localized overload is not sufficient for tripping the main circuit breaker, whose tripping level is set to an actual overload of the transformer. A special technique is applied to sense and diagnose this fault in addition to routine overload sensing. Differentiation of such a typical fault from a real overload condition is done by sensing and monitoring the primary current of the transformer with reference to different operating scenarios. Electronic means are used for fast detection and isolation of the RHVPS from the utility supply. The presented system effectively protects the transformer from fault at any one of its 40 secondaries and in an actual overload situation.This paper describes an overall RHVPS power scheme along with output fault protection and an internal fault diagnosis system and test results thereof.

Microcontroller based Under/Over Voltage and Double Phasing Fault Protection System: Design and Simulation

Microcontroller based Under/Over Voltage and Double Phasing Fault Protection System: Design and Simulation

A synchronous generator circuital model for internal fault analysis and protection system design

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.

Optical Coding for Next-Generation Survivable Long-Reach Passive Optical Networks

Optical coding has been proposed and has been well investigated for the monitoring of standard time domain multiplexing passive optical networks (TDM-PONs). We propose a physical layer fault management and protection system for next-generation passive optical networks, so-called long-reach PON (LR-PON), based on passive optical coding. Our approach exploits adapted, performance enhanced, and inexpensive passive optical components in the field, and electronic switches in the central office (CO). This allows detection and localization of the faulty segments in addition to the faulty nodes, hence decreasing the false alarm probability encountered in previous proposed approaches. We show that ring duplication protection in LR-PON can save almost half the cost compared with full duplication protection, with relatively high availability (99.992%). We describe the implementation strategy of our system in various well-known metro network topologies, including (1) single-ring-, (2) double-ring-, and (3) double-fiber-pairs-based ring topologies; all are considered different varieties of ring-and-spur LR-PON. The internal architecture of the remote nodes and the CO are also described in addition to the appropriate placement of our passive monitors. We develop two novel symmetric coding settings. We call them symmetrical optical encoders, which are suitable for fault detection and localization in the ring. We also develop the algorithms required to be executed by the network management system in the CO for fault detection, localization, and protection. Expressions for the upper bound notification and recovery times are also derived. Finally, we estimate that our system can recover from a fault in less than 0.5 ms for a 100 km ring length.

Design of Smart MVDC Power Grid Protection

Improved reliability and safety of the medium-voltage dc power distribution systems on board of all electric ships are the objectives of this paper. The authors propose the integration of the self-healing capability against faults of the measurement system in power system fault detection and protection systems. While most of previous work in the literature focuses on either one aspect independently, here, the two are integrated. On one hand, our approach addresses also the case of concurrent power system fault and measurement system fault. On the other hand, the proposed approach must be capable of distinguishing between the two types of failure. The proposed architecture is based on exchange of information between energy conversion and measurement devices. This makes the impact of communication delays critical, so its analysis is provided for the proposed case study. The impact on the performance of the measurement validation and protection systems is derived and can provide hints on the design. The protection method used as case study consists in controlling power converters to ride through the power system fault while maintaining power supply to the vital loads. To overcome failures of the measurement system, invalid data were detected and reconstructed through their expected value.

Fault Protection System for Current Source Inverter with Normally on SiC JFETs

This paper describes a simple fault protection system for Current Source Inverter built with normally-on SiC JFETs. Because all transistors are in on-state after loss of the gate drive(s) supply, list of possible fault modes is extended in reference to standard inverters. That is also why an additional normally off switch is introduced in the DC link. Operation principles of the protection system which follows the drain-source voltages of JFETs and the current of the DC link are presented. The 2kVA/100kHz model of the inverter equipped with the proposed system is validated via various laboratory tests including short-circuits and the auxiliary supply turn off.

발전기 고장보호를 위한 디지털 계전기에 관한 연구

전력설비의 대용량, 고전압화 됨에 따라 발전기 고장 예방을 위한 고장보호시스템의 필요성이 점차 증대되고 있다. 신속하고 신뢰성 있게 운전하며 보호하는 발전기 보호제어 시스템의 개발이 시급히 요구된다. 본 논문에서는 전력 공급의 안정을 도모하고 대용량, 고전압화 되는 발전기의 고장 예방을 위한 발전기 보호기능을 갖춘 디지털 보호계전기 설계에 관한 연구를 수행하였다. 디지털 계전기의 발전기 고장보호에 사용되는 고장보호 알고리즘을 개발하였고 디지털보호계전기 H/W를 설계 제작하였다.

ANN based real time incipient fault detection and protection system for induction motor

Artificial neural network (ANN) has its unique advantage in the area of incipient faults detection. This article presents an ANN based real time fault detection and protection system for two types of incipient faults viz. inter-turn insulation failure and bearing wear in single-phase induction motor. The ANN fault detection (ANNFD) program is developed in C++ and implemented using a PC based DSP controller board. The ANN is trained and tested by collecting the online experimental data for five input parameters viz. motor intake current, rotor speed, winding temperature, bearing temperature and noise. The results are compared with the signature of measurable parameters. The results of evaluation indicate that the system produces satisfactory performance for the fault detection as well as for the protection of motor.

Reliability Improvement of Ground Fault Protection System Using an S-Type Horn Attachment Gap in AC Feeding System

Contact wires used in feeding system for electric railroad are insulated by insulators. However, insulation of an insulator sometimes breaks down by surface dirt of an insulator and contact with a bird. The insulator breakdown derives a ground fault in feeding system. Ground fault will cause a human electric shock and a destruction of low voltage electric equipment. In order to prevent the damage by ground fault, an S-type horn has been applicable as equipped on insulators of negative feeder and protective wire until present. However, a concrete pole breaks down at the time of the ground fault because a spark-over voltage of the S-type horn is higher than a breakdown voltage of a concrete pole. Farther, the S-type horn installed in the steel tube pole does not discharge a case, because the earth resistance of a steel tube pole is very small. We assumed that we could solve these troubles by changing the power frequency spark-over voltage of the S-type horn from 12kV to 3kV. Accordingly, we developed an attachment gap that should be used to change the power frequency spark-over voltage of the S-type horn from 12kV to 3kV. The attachment gap consists of a gas gap arrester and a zinc oxide element. By the dynamic current test and the artificial ground fault test, we confirmed that the attachment gap in the S-type horn could prevent a trouble at the time of the ground fault.

Analysis of Common-Mode Voltage in Utility-Interactive Fuel Cell Power Conditioners

Fuel cell stacks produce a dc output with a 2:1 voltage variation from no load to full load. It is customary for a utility-scale fuel cell stack to consist of several hundreds of series-connected cells, each producing 0.6 V at full load. A power conditioner consisting of dc-dc and dc-ac converters is required for utility interface, which are operated in high frequency, employing pulsewidth-modulation control for voltage and current regulation. Due to their switch-mode nature, a common-mode voltage with respect to ground is generated. The common-mode voltage, in turn, contributes to the circulating ground current, which can interfere with the ground fault protection system. In addition, it also contributes to the neutral shift and electromagnetic interference. Moreover, the electrostatic potential to ground within the fuel cell stack needs to be limited for safe operation. This paper presents an analysis of common-mode voltage in several fuel-cell-powered converter topologies connected to the electric utility and discusses several mitigation methods suitable for utility-scale generation.

Autonomous safeing and fault protection for the New Horizons mission to Pluto

The New Horizons spacecraft now bound for the planet Pluto and beyond to the Kuiper belt was successfully launched on January 19, 2006. The New Horizons spacecraft has backup devices for its major electronic modules, and also has a heavily cross-strapped architecture that makes the spacecraft fully tolerant of almost all single-point failures. The onboard fault protection system detects failure of a component and autonomously activates the backup system as necessary. The onboard safeing system detects anomalies in spacecraft performance, such as attitude control errors or propulsion system problems, and then autonomously places the spacecraft into one of two safe states.

Co‐ordinated voltage control of DFIG wind turbines in uninterrupted operation during grid faults

AbstractEmphasis in this article is on the design of a co‐ordinated voltage control strategy for doubly fed induction generator (DFIG) wind turbines that enhances their capability to provide grid support during grid faults. In contrast to its very good performance in normal operation, the DFIG wind turbine concept is quite sensitive to grid faults and requires special power converter protection. The fault ride‐through and grid support capabilities of the DFIG address therefore primarily the design of DFIG wind turbine control with special focus on power converter protection and voltage control issues. A voltage control strategy is designed and implemented in this article, based on the idea that both converters of the DFIG (i.e. rotor‐side converter and grid‐side converter) participate in the grid voltage control in a co‐ordinated manner. By default the grid voltage is controlled by the rotor‐side converter as long as it is not blocked by the protection system, otherwise the grid‐side converter takes over the voltage control. Moreover, the article presents a DFIG wind farm model equipped with a grid fault protection system and the described co‐ordinated voltage control. The whole DFIG wind farm model is implemented in the power system simulation toolbox PowerFactory DIgSILENT. The DFIG wind farm ride‐through capability and contribution to voltage control in the power system are assessed and discussed by means of simulations with the use of a transmission power system generic model developed and delivered by the Danish Transmission System Operator Energinet.dk. The simulation results show how a DFIG wind farm equipped with voltage control can help a nearby active stall wind farm to ride through a grid fault, without implementation of any additional ride‐through control strategy in the active stall wind farm. Copyright © 2006 John Wiley &Sons, Ltd.

Experiences using lightweight formal methods for requirements modeling

The paper describes three case studies in the lightweight application of formal methods to requirements modeling for spacecraft fault protection systems. The case studies differ from previously reported applications of formal methods in that formal methods were applied very early in the requirements engineering process to validate the evolving requirements. The results were fed back into the projects to improve the informal specifications. For each case study, we describe what methods were applied, how they were applied, how much effort was involved, and what the findings were. In all three cases, formal methods enhanced the existing verification and validation processes by testing key properties of the evolving requirements and helping to identify weaknesses. We conclude that the benefits gained from early modeling of unstable requirements more than outweigh the effort needed to maintain multiple representations.

Modified Differential Ground Fault Protection for Systems Having Multiple Sources and Grounds

This paper discusses the modified differential ground fault protection system, for the purpose of illustrating that 1) such systems are suitable for application on service equipment having multiple sources of electrical power, each of which may have multiple grounds, 2) such systems may be applied using conventional equipment that is currently available from several suppliers, 3) such systems can meet requirements for generator grounding without the use of four-pole transfer switches and switched neutrals, 4) such systems may be analyzed for effectiveness using conventional circuit analysis techniques.

Design, construction and operation of the Fast Protection System of the windings of RFX

The protection of the windings of RFX against fast electric faults relies on an original dedicated Fast Protection System able to operate within 1 ms. The first ring of the protection chain is the fault protection system of the winding, named RGM, that consists of: about hundred highly reliable voltage and current probes, all electric signal lines and an analog-digital device where signals are processed and logic alarms are generated. RGM is an original machine that required a careful design and manufacturing work. After a long test and adjustment phase it now operates properly. It has already operated against some earth faults which, due to low level of earth current, mere not dangerous for the machine but very hard to detect. >