Overcurrent Fault Research Articles

Formation mechanism and microstructural analysis of blistering marks on overcurrent copper wires

Electrical fires frequently result in severe casualties, with overcurrent faults being a primary cause. This study investigates the formation mechanisms of blistering marks on polyvinyl chloride (PVC) insulated copper wires, traditionally attributed to direct flame exposure. We conducted a comprehensive analysis of PVC copper wires subjected to overcurrents ranging from 190 to 240A, examining the resultant microstructural changes. Our findings challenge conventional beliefs by demonstrating that certain blistering marks, especially on non-flame-retardant PVC (NF-PVC) insulated wires, are indicative of overcurrent faults rather than flame exposure. By integrating detailed microstructural analysis with the thermal decomposition characteristics of the PVC insulation, this study provides new insights into diagnosing the causes of electrical fires and advocates for more meticulous methods in fire investigations.

Investigation into the overcurrent failure and combustion characteristics of copper‐clad aluminum conductors

AbstractElectrical fires perennially rank first in fire occurrence types, with conductor overcurrent being one of the main inducements. This topic draws significant attention from scientific researchers and fire investigators. To understand the overcurrent fault and combustion characteristics of copper‐clad aluminum conductors, this paper examines 2.5 mm2 copper‐clad aluminum conductors that meet national standards, investigating morphological changes, temperature variations in the core and insulation layer, and flame propagation patterns under overcurrent conditions. Experiments using an electrical fault simulation device were conducted to study overcurrent failures of copper‐clad aluminum conductors under 52.5–105 A conditions. The results indicate that when the current exceeds 67.5 A, the conductor undergoes a series of changes during energization, including smoking, expanding, carbonizing, burning, and breaking; at 52.5 A, the insulation layer reaches thermal equilibrium at 150 s without combustion; for currents between 60–67.5 A, wire core temperature variations can be divided into three stages; at 75 A, the insulation layer reaches thermal equilibrium 10s before breaking; currents above 82.5 A see a sharp increase in temperature in both the core and insulation layer before the conductor breaks; above 97.5 A, the conductor first breaks and then burns. The research results have significant theoretical value in improving the scientific rigor of fire accident investigations and forensic evidence examinations.

Experimental and theoretical research on the temperature evolution law of overcurrent fault wires

AbstractTo investigate the problems of overload and excessive thermal insulation associated with building electrical fires caused by wires, a theoretical model of wire heat transfer is established, and the pyrolysis and combustion phenomena of the insulation layer are analyzed. The results showed that the temperature evolution of the wire underwent three stages: constant temperature, insulation heating, and high‐temperature pyrolysis. The insulation layer experiences bulging, exhausting, carbonization, dripping, and burning in sequence, and insulation layer dripping requires at least 160 A of current. As the current increases, the temperature increase rate of the wire increases gradually, and the fusing time of the wire gradually decreases. Under the same current, 160°C is the turning point at which the temperature increases. The temperature increase rate of the copper wire is greater than that of the aluminum alloy wire, and the temperature increase rate of the bare wire is greater than that of the insulated wire. The fusing time of an aluminum alloy wire is less than that of a copper wire, and the fusing time of a bare wire is less than that of an insulated wire. The research results provide theoretical guidance for the prevention and investigation of building electrical fires.

Development of 3-phase fault detection, protection, and automation application with the present of DG in AC power system using GOOSE protocol

In this research work, a protection and automation solution is developed, encompassing SEL751 and SEL751A protection relays that communicate through the IEC-61850 Generic Object-Oriented Substation Event (GOOSE) protocol to deliver high-speed detection and clearance of a 3-phase (3P) fault. The study case is a standard IEEE 13-bus grid including the main system generator (G1), power lines, loads, distributed generation (DG), bus bars, and feeders, equipped with protection relays for detecting over-current faults based on time and current. Two protection relays, B1 in the main system and B2 on the DG side, are integrated with a GOOSE protocol communication system. These settings are configured in such a way that, in the event of the main system breaker being disconnected, the DG cannot be connected to the network, making it a suitable setting for anti-islanding mode (AIM). The efficiency of the relay settings is tested by subjecting the power grid to a 3P fault, by the selected Time-Overcurrent (TOC) U3 inverse curve. Throughout the paper, the descriptions of the study, the grid, assumptions, settings calculations, and analysis of results are systematically presented. For the verification of relay settings, the performance of relays is practically tested and accurately analyzed in detail. The results obtained indicate that the presented strategy is quite effective for the configuration, setting operation, and coordination of relays for fast detection and communication through the GOOSE protocol.

A combined regulation method of transient power angle stability control and fault current suppression for VSG

When a serious grid fault occurs, a virtual synchronous generator (VSG) tends to lose transient power angle stability (TPAS) and cause the fault current to exceed the limit. Most existing research usually neglects the inherent relationship between transient power angle instability (TPAI) and fault over-current (FOC), which leads to the two problems being solved separately rather than simultaneously. In this paper, the transient power angle and fault current characteristics of VSG are first studied, and the causes and influencing factors of TPAI and FOC are explored. Then, the TPAS analysis is carried out based on the phase portrait theory. A TPAS control method for VSG considering fault current suppression (FCS) is proposed. This method is fulfilled by the combined regulation of active power reference and reactive voltage regulation coefficient, in which the reference and coefficient can be adjusted adaptively according to different fault degrees and application scenarios. In addition, a quasi-static approximate (QSA)virtual inductance is introduced to limit the instantaneous inrush current (IIC). The proposed method achieves both the TPAS and FCS at the same time during the fault. Finally, simulations and experiments verify the correctness of the theoretical analysis and the proposed method.

Study on the microstructure characteristics of melting marks in copper-clad aluminum wires under overcurrent faults

Study on the microstructure characteristics of melting marks in copper-clad aluminum wires under overcurrent faults

A novel fault location strategy based on Bi‐LSTM for MMC‐HVDC systems

AbstractThe integration of modular multilevel converters (MMCs) with high voltage direct current (HVDC) transmission systems is an efficient method for transporting electricity from distant renewable energy sources to demand centres. However, MMC‐HVDC systems face reliability challenges during DC overcurrent faults, often caused by component failures that can lead to HVDC network shutdowns. Consequently, a reliable fault location approach is crucial for grid protection and restoration, aiding in fault isolation and alternate power flow identification. Conventional fault location methods struggle with manual protective threshold setting, susceptibility to fault resistance and noise, and the need for communication channels, resulting in signal delays. In multi‐terminal HVDC networks, fault location becomes even more complex due to poor selectivity and sensitivity in traditional schemes. This study proposes a robust fault location approach based on bidirectional long short‐term memory (bi‐LSTM). The method offers a simplified decision‐making model with low computational requirements, utilizing fault features from one end of the network, eliminating the need for a communication channel. Remarkably, this approach achieves high fault location accuracy, even with varying fault types, resistances, and noise levels, as demonstrated by an MSE of 0.006 and a percentage error below 1% in simulations conducted using a real‐time simulator with MATLAB/Simulink.

Adaptive control of DFIG-based wind turbines for fault ride-through and reactive power support based on stator current transient component

The fault ride-through performance is improved through the control of the transient components of the stator current. The reactive power provided by the DFIG within the margin of the converter can significantly enhance the grid-connected safety of the DFIG. Firstly, the reasons for the fault overcurrent of the DFIG’s rotor are analyzed. Secondly, according to the operating conditions of the wind turbine, the reactive power support limit of the DFIG-based wind turbines based on the stator current transient component control is analyzed, and an adaptive reactive power support control suitable for fault ride-through is proposed to maximize its support potential for grid-connected voltage. Finally, the DFIG can not only suppress the rotor overcurrent through the transient component of the stator current but also have a reactive power support capability that is superior to the grid-connected standard.

An experimental study on the combustion process and thermodynamic characteristic parameters of copper wire overcurrent fault

AbstractThe overcurrent fault of copper wire is an important cause of electrical fire, and the combustion process of which is relatively complicated. In this study, the rated current of 32A of the wire was taken, and the electrical fault simulation device was used. After the overcurrent Io was set to 128A, 160A, 192A, and 224A, respectively, to analyze the combustion evolution process of PVC‐insulated copper wire, the evolution of pyrolysis gas from the insulating layer, and the change of functional groups. The results show that when the overcurrent fault of PVC‐insulated copper wire happened, the core wire was turning red, the wire was deforming, the smoke was releasing, the insulating layer was dripping, the wire was fusing, and the continuous burning occurred. When the current Io < 160A, there was only one fusing point on the wire. In addition, when an overcurrent fault occurred in the PVC‐insulated copper wire, the temperature rise rate increased exponentially, which can be divided into three stages of the initial heat accumulation stage, the wire fusing stage, and the continuous burning stage. Furthermore, CO, HCl, CH4, olefins, and aliphatic and aromatic compounds were precipitated during the combustion process of the PVC insulating layer. The quality of the insulating layer decreased with the increase in temperature, and the weight loss rate was higher at 300°C. The conclusions of this study have provided experimental basis and technical support for the physical and evidence identification of fire accidents.

Numerical simulation and experimental study on metallographic structure characteristics of melting trace caused by overcurrent fault of copper wire

The microscopic characteristics of melting trace caused by copper wire fault are an important basis for the physical evidence identification of electrical fires. Metallography is an important method in electrical fire research, and computer-aided quantitative analysis on metallographic structure is common in materials aspect. In this study, the metallographic structure and phase composition characteristics of melting trace caused by overcurrent fault were explored with the aid of a metallographic microscope and an X-ray diffractometer (XRD). The results show that the grains are mainly slender dendritic and columnar crystals when the current is 128 A, while they are coarse dendritic and cellular crystals when the current is greater than 192 A; the average grain diameter of melting trace of copper wire grows with the increase in current. The main phases of melting trace caused by overcurrent fault of copper wire are α-Cu base and Cu2O, and the new phases Cu4Si and Cu2Mg are formed when the current is higher than 160 A. In addition, the solidification process of metallographic structure of copper wire under different currents was simulated by the Procast software. It is found that the simulation results are basically in agreement with the experimental data, which suggests that this model can effectively predict the microstructure characteristics of melting trace of copper wire under different currents. The research results can provide a sound basis for the physical evidence identification of electrical fire and improve the accuracy and scientificity of electrical fire investigation.

Demonstration of ITER Real-Time Framework with application of PF coil control in KSTAR

ITER Real-Time Framework (RTF) is a middleware for developing fast real-time control applications such as plasma control system (PCS). In this framework, applications are built by creating and assembling Function Blocks (FBs) as atomic components of the application. The RTF can easily configure the application to be operated with multi-thread, multi-process, or multi-node processing under real-time mode. In this paper, we demonstrated capability of the RTF on the Poloidal Field (PF) coil Magnetic Power Supply (MPS) system of KSTAR. First, we fully implemented the KSTAR PF coil control logic from the KSTAR PCS into an independent RTF application. By configuring the real-time mode and multi-thread processing, 11 PF coils can be simultaneously controlled with a 20 KHz execution cycle. Second, we applied a built-in exception handler in the RTF to implementing protection from specified off-normal events such as PF Power Supply Fault (PSF) and PF OverCurrent Fault (OCF). Third, we integrated the standard real-time network interfaces of the KSTAR, the Reflective Memory (RFM) network, with the RTF application. Finally, we made a shot automation interface in order to run the RTF application according to the KSTAR shot sequence stages. This interface also has a snapshot functionality to store and load all experimental parameters for each shot number. We evaluated the effectiveness of the RTF application through a single PF MPS test connected with a 40 mH dummy load coil.

In Situ Diagnosis of Multichip IGBT Module Wire Bonding Faults Based on Collector Voltage Undershoot

Condition monitoring of insulated gate bipolar transistor (IGBT) modules is an effective way to improve the transient performance and reliability of modular multilevel converters (MMC). This article proposes a novel bond wire failure monitoring method for the multichip IGBT modules in the MMC half-bridge submodule (SM) structure. The collector voltage undershoot <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CA(np)</sub> of the complementary IGBT switch is measured during the turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> switching transition of the controlled IGBT switch. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CA(np)</sub> is sensitive to the induced voltage over the stray inductance of the IGBT bond wires and provides high sensitivity as a health indicator. The non-intrusive measurement technique is demonstrated using a half-bridge circuit during the turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> transition of the controlled IGBT, while its complementary switch (i.e., the device under test) is in the <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> state. Theoretical analysis and experimental results show that the parametric drift due to wire bonding failures can be effectively monitored with high specific relative sensitivity and granularity. To ensure its effectiveness in practical applications, the influence of load current, SM capacitor voltage, and junction temperature is discussed. In addition, a readout circuit is designed featuring the integrated desaturation detection and voltage peak detection, which offers both the short-term overcurrent fault protection and long-term bond wire aging monitoring functions.

An Improved Protection Circuit Design for Fast Detection of Short-Circuit in IPM

Short-circuit protection plays a vital role in ensuring the overall reliability of intelligent power module (IPM), where the shorter the duration of a short-circuit fault, the smaller its impact on the module. The conventional <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CE</sub> desaturation detection circuit suffers from a blanking time problem. This paper aims to solve this problem by improving the IPM short-circuit fast detection and protection circuit with integrated shunts in order to achieve ultra-fast detection and protection of the IPM short-circuit faults. First, the types of IPM short-circuit faults and the experimental principle of a short-circuit are introduced in this paper. Second, the overcurrent fault protection of the improved circuit with the shunts integrated at different positions in the IPM power unit is analyzed and verified using the PSPICE simulations. Third, a selection method for the component parameters of a compensation link of the improved circuit is proposed, and the functions for the remaining parts in the circuit are introduced. Last, it is verified through experiments that the improved circuit can quickly detect various short-circuit faults, and initiate the corresponding shutting down of the insulated gate bipolar transistor (IGBT) at 490 ns. Compared with the conventional <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CE</sub> desaturation detection method, the detection time of the proposed method and the associated short-circuit loss for modules under different short-circuit faults are significantly reduced.

An energy and leakage current monitoring system for abnormality detection in electrical appliances

Unsafe electrical appliances can be hazardous to humans and can cause electrical fires if not monitored, analyzed, and controlled. The purpose of this study is to monitor the system’s condition, including the electrical properties of the appliances, and to diagnose fault conditions without deploying sensors on individual appliances and analyzing individual sensor data. Using historical data and an acceptable range of normal and leakage currents, we proposed a hybrid model based on multiclass support vector machines (MSVM) integrated with a rule-based classifier (RBC) to determine the changes in leakage currents caused by installed devices at a certain moment. For this, we developed a sensor-based monitoring device with long-range communication to store real-time data in a cloud database. In the modeling process, RBC algorithm is used to diagnose the constructed device fault and overcurrent fault where MSVM is applied for detecting leakage current fault. To conduct an operational field test, the developed device was integrated into some houses. The results demonstrate the effectiveness of the proposed system in terms of electrical safety monitoring and detection. All the collected data were stored in a structured database that could be remotely accessed through the Internet.

Research on Fault Diagnosis of Switchgear Based on Temperature Cloud Image Technology

In the process of power system operation, contact aging, partial discharge and overcurrent faults are the main causes of switch cabinet faults. At the same time, it is difficult to install sensors inside the switch cabinet due to its closed operation. In this paper, in order to solve the over current problem of switchgear, according to the principle of high current heating, the thermal flow model of power switchgear is established, and the characteristics of heat flow inside the switchgear are studied. The infrared temperature detector is designed to collect the surface temperature cloud map of the switchgear. Combined with the internal heat flow law of the switchgear, the over current phenomenon in the switchgear is judged, so as to judge the operation state of the switchgear. In order to verify the correctness of the theory proposed in this paper, the operation state of the fault switch cabinet is designed for detection and comparative analysis. The test results show that the heat change caused by the over-current fault can be accurately fed back to the surface of the switch cabinet, which can be used as an effective means to diagnose the fault of the switch cabinet.

Short-Circuit and Over-Current Fault Detection for SiC MOSFET Modules Based on Tunnel Magnetoresistance With Predictive Capabilities

This letter proposes a short-circuit and over-current fault detection solution for silicon-carbide (SiC) <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> modules based on tunnel magnetoresistance (TMR). The TMR sensor is integrated into an SiC <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> module to noninvasively measure its current. The measured current is compared with a threshold to detect short-circuit and over-current faults. The TMR sensor is installed in a chosen location, where the TMR sensor gain is automatically doubled in the event of short-circuit fault. As a result, a short-circuit fault can be predicted, i.e., the fault is detected before the actual short-circuit current reaches the threshold. Besides, only one TMR sensor is required to detect both short-circuit and over-current faults for a half-bridge power module. According to the experimental results, the short-circuit fault is detected when the fault current reaches half of the fault threshold current. The experimental results indicate general superiority over desaturation technology and better performance in detection time, reaction time, and total protection time compared with Rogowski switch-current sensor-based technology.

Research on Latching Current Limiter Circuit of Aerospace Power System

The input terminal of the aerospace power system is connected with surge suppression and overcurrent protection circuits. However, prior art methods have many demerits such as complex circuits, high surge currents, and slow response of overcurrent protection. Hence, this paper proposes a novel latching current limiter (LCL) circuit with both surge suppression and over-current protection functions. When over-current occurs, the circuit snap into the current limiting state within the adjustable time-delay period. When the over-current fault despairs during the time-delay period, the LCL circuit turns into the output lock state and rapidly lock down the output bus wire. Theoretical analysis of LCL circuit including the three operation states (i.e., the normal operation state, current limiting state and output lock state) and basic circuit equation derivation have been carried out. And the experimental platform is set up to validate the superior performance of the proposed LCL circuit. Results show that the proposed LCL circuit can effectively suppress the inrush current and sensitively respond the over-current fault of dc-link bus wire.

A New Detection Method for Load Side Broken Conductor Fault Based on Negative to Positive Current Sequence

Faults in distribution overhead lines occur due to various reasons, such as rain, strong winds, lightning, and other natural causes. The protection from the load side broken conductor (LSBC) faults has been one of the biggest challenges in the power distribution network. The small current generated by the LSBC fault makes the traditional protection system unable to detect this type of fault. The danger of LSBC fault is still enormous; besides, the available works of literature addressing this issue face difficulties when applying it to the real power system. This paper proposes a new method for detecting LSBC fault using single-ended measurements to the overhead distribution lines. The detection method is based on the constant ratio of negative to positive sequence current measured at the feeder end. The proposed study is performed using MATLAB software to implement a real network as a case study and verified by mathematical analysis. According to obtained results, we demonstrated that the fault in the electrical network had been detected with 100% of feeder protection. The proposed method has the benefit of being applicable and compatible with the existing measurement equipment, even when used in conjunction with overcurrent and earth fault relay in the electrical substation. Therefore, the negative to positive sequence currents are powerful in aiding fault detection. The benefit of this approach is providing a suitable LSBC protection solution for utilities while also opening new prospects in fault detection techniques in the distribution system.

Concise Silicon Carbide DC Circuit Breaker Module for Satellite Electrical Systems

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.

Enhanced Back Controlled Phase Fault and Earth Fault Busbar Protection Scheme using Overcurrent and Earth Fault Relays

Enhanced Back Controlled Phase Fault and Earth Fault Busbar Protection Scheme using Overcurrent and Earth Fault Relays