Protection Devices Research Articles

Reversible negative compressibility metamaterials inspired by Braess’s Paradox

Negative compressibility metamaterials have attracted significant attention due to their distinctive properties and promising applications. Negative compressibility has been interpreted in two ways. Regarding the negative compressibility induced by a uniaxial load, it can only occur abruptly when the load reaches a certain threshold. Hence, it can be termed as transient negative compressibility. However, fabrication and experiments of such metamaterials have rarely been reported. Herein, we demonstrate them. Inspired by Braess’s paradox, a novel mechanical model is proposed with reversible negative compressibility. It shows multiple types of force responses during a loading-unloading cycle, including transient negative compressibility and hysteresis. Phase diagrams are employed to visualize the relationship between force responses and system parameters. Besides, explicit expressions for the conditions and intensity of negative compressibility are obtained for design and optimization. The model replacement method inspired by compliant mechanism design is then introduced to derive specific unit cell structures, thus avoiding intuition-based approaches. Additive manufacturing technology is utilized to fabricate the prototypes, and negative compressibility is validated via simulations and experiments. Furthermore, it is demonstrated that metamaterials with transient negative compressibility can be activated through electrical heating and can function as actuators, thereby possessing machine-like properties. The proposed mechanical metamaterial and the introduced design methodology have potentials to impact micro-electromechanical systems, force sensors, protective devices, and other applications.

Amino-functionalized Ti3C2 and ZIF-8-induced high lubricity, friction robust self-healing polyurethanes as solid lubrication films

Self-healing polyurethane (SPU) has important applications in areas such as protective coatings, medical devices and solid lubrication. However, improving the lubricating properties of self-healing polyurethanes to reduce their friction and wear is still an important challenge. Herein, an amphoteric SPU is prepared and used as the solid lubrication matrix. NH2-Ti3C2-ZIF-8 is grown on NH2-Ti3C2 in situ to obtain NH2-Ti3C2-ZIF-8 as lubrication additive. The lubrication performance of NH2-Ti3C2-ZIF-8/SPU composites is the best when the NH2-Ti3C2-ZIF-8 content is 1.00 wt%. The coefficient of friction (COF) is only 0.10, and the wear rate is only 1.315×10−4 mm3/(N·m), which are reduced by 80.4 % and 99.4 % respectively compared with single SPU. By exploring the lubrication mechanism, it is found that NH2-Ti3C2-ZIF-8 participated in producing transfer film during friction, and the excellent lubricity and anti-wear effect of NH2-Ti3C2 and the unique adsorption and rolling effect of ZIF-8 jointly improved the friction performance of the samples. In addition, the composite material can realize rapid healing within 5 min at 75 %RH, 20℃, the self-healing efficiency can reach 84.7 %. Therefore, the SPU containing NH2-Ti3C2-ZIF-8 has potential applications in the field of solid lubricated materials.

Improvement of the model for calculating the protection coefficient of filtering respirators from harmful aerosol

Research objective. Improvement of the model for calculating the protection coefficient of filtering respirators from harmful solid aerosol. Materials and methods. For the experimental determination of the protection coefficient of the filtering respirator according to the standard DSTU EN 149:2017 «Personal respiratory protective devices. Filtering half masks to protect against aerosols. Requirements, testing, marking» and the application of the method DSTU EN 13274-1:2005 «Personal respiratory protective devices. Methods of testing. Part 1. Determination of the penetration coefficient and the overall penetration coefficient», lightweight filtering half masks of «Standard» FFP2 type were used on volunteers. Results. The protection coefficient of the filtering respirators used on volunteers in laboratory conditions was calculated at the specified concentration of test aerosol in the ambient air by the standard testing method described in DSTU EN 13274-1:2005 «Personal respiratory protective devices. Methods of testing. Part 1. Determination of the penetration coefficient and the overall penetration coefficient» and takes into account the measurement error from the instruments not exceeding 10%. A comparison of the obtained indicators of the protection coefficient of filtering respirators in laboratory conditions and with the developed theoretical model, taking into account particle deposition in the sampling probe and submask space during the exhalation process, showed a good agreement of the indicators by the Student's t-test criterion. Scientific novelty. The scientific novelty lies in the development of a model for calculating the protection coefficient of filtering respirators based on the assessed mass distribution function of aerosol particles in the breathing zone; penetration function through the gap between the face and the half mask, taking into account the inhalation and exhalation process, as well as particle deposition in the sampling probe. Practical significance of the work lies in the development of a formula for the theoretical determination of the protection coefficient of filtering respirators, which is used to calculate the professional risk of pneumoconiosis among users

Evaluasi Kinerja Sistem Proteksi Penyulang Trawas PT. PLN (PERSERO) ULP Pandaan

The primary objective of this research was to minimize disruptions in the feeder at ULP Pandaan by analyzing the coordination between recloser outgoing and incoming feeders. This study addressed the frequent issue of recloser trips, which caused instability in power supply. The purpose of this research was to provide conclusions and solutions to mitigate these disruptions. The methodology involved a detailed analysis of OCR (Over Current Relay) settings for protective devices on Trawas feeder. This included measurements of primary current settings and TMS (Time Multiplier Setting) values using both standard inverse and normal inverse configurations. Specific settings, such as 25518 A for the Trawas Recloser primary current and a TMS of 0.07, were determined to yield optimal performance. Additional settings for the Outgoing CB (Circuit Breaker) (357061 A, TMS 0.04) and the Incoming CB (181865 A, TMS 1.0) were also established. The important findings revealed that these settings significantly enhanced the reliability of the protective devices, ensuring better coordination between the recloser and CB systems. The implications of this research were substantial, as the optimized settings were expected to reduce the frequency and impact of feeder disruptions. This improvement in system reliability directly benefited both the electricity provider, PT. PLN (Persert), and the consumers by providing a more stable and efficient power supply. In conclusion, this study offered a comprehensive analysis and practical solutions for enhancing the protection system's performance on the Trawas feeder, which could be applied to similar electrical distribution networks to achieve better stability and reliability.

Use of an embolic protection device during carotid artery stenting is associated with lower periprocedural risk

ObjectiveTo investigate associations between individual embolic protection device (EPD) use and respective center policy with periprocedural outcomes after carotid artery stenting (CAS).MethodsThis analysis is based on the nationwide German statutory...

Effects of percutaneous endovascular angioplasty for severe stenosis or occlusion of subclavian artery

To investigate the effect and safety of percutaneous endovascular angioplasty (PEA) with optional stenting for the treatment of severe stenosis or occlusion of subclavian artery, patients with severe stenosis ≥ 70% or occlusion of subclavian artery treated with PEA were retrospectively enrolled. The clinical data were analyzed. A total of 222 patients were retrospectively enrolled, including 151 males (68.0%) and 71 females (32.0%) aged 48–86 (mean 63.9 ± 9.0) years. Forty-seven (21.2%) patients had comorbidities. Subclavian artery stenosis ≥ 70% was present in 201 (90.5%) patients and complete subclavian occlusion in 21 (9.5%) cases. Angioplasty was successfully performed in all (100%) patients. Balloon-expandable stents were used in 190 (85.6%) cases, and self-expandable stents in 20 (9.0%) cases. Only 12 (5.4%) cases were treated with balloon dilation only. Among 210 patients treated with stent angioplasty, 71 (33.8% or 71/210) cases underwent balloon pre-dilation, 139 (66.2% or 139/210) had direct deployment of balloon-expandable stents, and 2 (1.0% or 2/210) experienced balloon post-dilation. Distal embolization protection devices were used in 5 (2.3% or 5/222) cases. Periprocedural complications occurred in 3 (1.4%) patients, including aortic dissection in 2 (0.9%) cases and right middle cerebral artery embolism in 1 (0.5%). No hemorrhage occurred. Among 182 (82.0%) patients with 6-month follow-up, restenosis > 70% occurred in 1 (0.5%) patient, and among 68 (30.6%) patients with 12-month follow-up, restenosis > 70% took place in 11 (16.2%) patients. Percutaneous endovascular angioplasty can be safely and efficiently performed for the treatment of severe stenosis ≥ 70% or occlusion of subclavian artery.

Bioprotective Respirator Assembled by Defective Carbon Nitride for Long-Term Light Triggered Health Protection.

Wearing face masks is the best way to stop the spread of respiratory infections. However, if masks are not sterilized, changing them too frequently can actually increase the risk of cross-contamination. Herein, the construction of an antipathogen photocatalytic mask with carbon vacancy-modified carbon nitride nanosheets (g-C3N4-VC Ns) coated on the non-woven fabrics of the out layer of the mask, offering effective and long-term protection against damaging pathogens when exposed to light is reported. The introduced carbon vacancies are found capable of creating energy-disordered sites and inducing energetic electric force to overcome the Coulomb interactions between electron-hole pairs, thus promoting the electron-hole separation to achieve a high generation of reactive oxygen species (ROS). Thanks to its high activity in generating ROS upon exposure to light, the as-prepared photocatalytic mask shows high pathogen sterilization performance. This, in turn, prolongs the mask's protective lifetime, decreases the need for regular replacement, and decreases medical waste production. The work demonstrated here opens new viewpoints in designing pathogens biocidal protective devices for health protection, offering significant promise in specific environment self-protection.

Research on the analysis method of power system relay protection action characteristics based on fault recording data

The action characteristics of power system relay protection devices can well analyze whether the relevant actions are correct. An analysis method of relay protection action characteristics in power system based on fault recording data is designed. After analyzing the relay device structure and protection action characteristics and requirements, the power system relay protection action record data recorded by the fault recorder; The second order RC low-pass filter is used to preprocess the recorded data; The filtered data is input into the analysis model of relay protection action characteristics based on SVM algorithm. The SVM algorithm classifies whether the relay protection action characteristics recorded by the filtered fault recording data meet the expectations, and completes the analysis of power system relay protection action characteristics. The experimental results show that this method can effectively analyze the operation characteristics of power system relay protection, and can accurately check whether the relay protection device can operate correctly.

Error analysis and improved method of time-domain distance protection for wind power transmission lines

Time-domain distance protection has a good transient performance and operation speed when applied to wind power transmission lines. In this paper, the error analysis and improved method of phase-to-phase time-domain distance protection are investigated. Firstly, based on the time-domain mathematical model, the location error caused by fault resistance is analyzed, and then the algorithmic convergence and accuracy of conventional phase-to-phase distance relay are evaluated. To solve the computational non-convergence problem, an improved phase-to-phase distance relay is proposed, in which the instantaneous negative-sequence current is used to improve the location accuracy, especially during the fault transient stage of wind farms. In order to avoid the protection overreach problem, the threshold selection method is designed based on the maximum allowable error of the calculated distance. According to the proposed method, the corresponding protection device is developed. And the hardware-in-the-loop (HIL) test system is built based on the real-time digital simulation (RTDS) platform. Extensive experimental tests are carried out, to verify the feasibility and superiority of the proposed time-domain distance protection.

Droplet Micro-Sensor and Detection of Respiratory Droplet Transmission.

Droplet transmission is the primary infection route for respiratory diseases like COVID-19 and influenza, but small and low-cost wearable droplet detection devices are a significant challenge. Herein, a respiratory droplet micro-sensor based on graphene oxide quantum dots (GOQDs) assembled onto SiO2 microspheres by the nebulized natural deposition is presented. Benefiting from the energy dissipation of the microsphere to droplets, the sensor can detect droplets as far as 2 m from coughing. With this sensor, droplet signal variations caused by some factors like distance, speech, angles, and wind directions are explored, and the effectiveness of different protective measures in preventing droplet transmission is evaluated. This droplet detection technology is expected to be utilized for the development of personal detection and protection devices against infectious respiratory diseases.

Minimizing tearing during vaginal delivery with a perineal protection device: a randomized controlled trial

There is a growing body of evidence indicating that second-degree tears cause both short- and long-term consequences. Very few preventative measures have been found to reduce the incidence of these tears. This study aimed to investigate whether the use of a perineal protection device during vaginal birth reduces severe perineal tearing (grade ≥2 tear) in primiparous women compared with routine manual perineal support. A single-center randomized controlled trial was conducted in Sweden from 2019 to 2021. Primiparous women at term were randomly allocated to the intervention group (n=43), where a perineal protection device was used, or to the routine care group (n=49). The primary outcome was grade of perineal tear. The secondary outcomes were vaginal and labial tearing. Continuous data were analyzed using the Student t test or Mann-Whitney U test. Dichotomous data were analyzed using the Pearson X2 test, Fisher exact test, and ordinal logistic regression. Women in the intervention group had a significantly lower risk of sustaining more extensive perineal tearing than those in the control group. The use of the perineal protection device decreased the risk of grade ≥2 tears in relation to grade 0 to 1 tears (odds ratio, 0.40; 95% confidence interval, 0.17-0.94). Ordinal logistic regression analyses revealed an odds ratio of 0.36 (95% confidence interval, 0.16-0.81) per incremetn of grade injury using the perineal protection device vs routine care (P=.013). The number needed to treat using the perineal protection device was 4.3 to avoid 1 grade ≥2 tear. Women in the treatment group showed less labial tearing (P=.016). No adverse effect was detected. The use of a perineal protection device reduced the risk of grade ≥2 perineal tearing by 60% and labial tearing. El resumen está disponible en Español al final del artículo.

AR Lightning Protection Device Teaching System Based On Vuforia

With the advent of the information age, augmented reality technology superimposes virtual three-dimensional models and real environments, giving us richer visual effects. Based on this problem, the augmented reality technology is introduced in the teaching process of lightning protection, and the teaching software of AR lightning protection device is developed. Taking various common lightning arrester contents in daily life as an example, Unity3D development engine and Vuforia augmented reality development tools were used to complete the systematic development and teaching of AR lightning protection devices. The realization process includes material resource production, scene construction and function development. After the software is released, the virtual model is presented in three-dimensional form through scanning pictures, which enhances the interest in the teaching process and is conducive to improving the teaching quality.

Contrast-enhanced ultrasound reveals free-floating thrombus in carotid artery: The cause of stroke is surprisingly plaque rupture.

Acute stroke poses a serious threat to people's health. The occurrence of a thrombus following the rupture of vulnerable plaques in the carotid artery is a significant contributor to the development of stroke. In previous case reports, it has been challenging to visualize tiny ulcerations within carotid artery plaques using computed tomography angiography (CTA) and digital subtraction angiography (DSA), even when the rupture of the plaque leads to the formation of a free-floating thrombus (FFT). However, in this particular case, contrast-enhanced ultrasound (CEUS) was able to overcome this limitation and provide a more precise assessment, confirming that the FFT formation was indeed a result of plaque rupture rather than any other potential causes. Cases that utilize CEUS to visualize the formation of ulcers and FFT resulting from plaque rupture are even more rare. As such, we present this case to shed light on this infrequent phenomenon. In this case study, we present a 65-year-old male patient who was admitted to the hospital due to headache and abnormal mental behavior for one day. During the routine cervical artery ultrasound examination upon admission, we detected the presence of plaque in the right internal carotid artery of the patient, resulting in luminal stenosis. Additionally, we observed suspected hypoechoic material at the distal end of the plaque. After undergoing CEUS examination, it was definitively determined that an ulcer had formed and a FFT had developed due to the rupture of carotid artery plaque. Subsequent CTA and DSA examinations further confirmed the presence of the FFT. The magnetic resonance imaging (MRI) reveals an acute lacunar infarction in the head of the right caput nuclei caudate, which strengthens the potential link between the patient's neurological and psychiatric symptoms observed during admission. The patient received prompt antiplatelet therapy and underwent cervical artery stenting surgery with the assistance of a distal embolic protection device. Following the procedure, the patient was discharged on the fourth day and experienced a complete recovery. CEUS is a valuable tool for visualizing FFT resulting from the rupture of vulnerable plaques in the carotid artery.

Holistic evaluation of inlet protection devices for sediment control on construction sites

To address the deleterious impacts of excess soil erosion from the construction sites, the United States Clean Water Act requires that erosion and sediment control measures (ESCs) be implemented on construction projects disturbing more than 0.4 ha. Inlet protection devices (IPDs) are a common ESC utilized on construction projects to reduce the amount of sediment entering storm sewers. In Ohio, regulatory agencies use approved, non-proprietary IPDs made from commonly available materials (e.g., silt fence, geotextile, lumber, and aggregate) to mitigate sediment on construction projects; however, these IPDs often rely on extended ponding to remove sediment and require frequent maintenance making these unsuitable for road construction projects. Commercially manufactured (i.e., proprietary) IPDs which rely on filtration to quickly dewater following rainfall may prove more practical for road construction projects. However, little research which quantitatively compares the holistic performance of these two types of IPDs in field settings has been performed to date. To address this knowledge gap, the performance of 24 proprietary IPDs was evaluated at field-scale using simulated construction site runoff and compared to three non-proprietary IPDs currently approved for use in Ohio. Bypass flows, which typically occurred due to poor IPD fit to standard drainage inlets used in Ohio transportation settings, significantly increased effluent total suspended solids (TSS) and turbidity compared to tests of IPDs where bypass did not occur. Overflow, or intentional bypass around primary IPD flow pathways during high flows, did not significantly impact effluent water quality. Despite differences in treatment mechanisms (i.e., sedimentation versus filtration), the water quality performance of non-proprietary and proprietary IPDs were not statistically different, indicating comparable sediment removal was provided by both categories. Findings from this research can provide design engineers and state regulatory agencies the necessary tools to evaluate IPD performance in road construction settings and, ultimately, alleviate the impact of excess sediment discharged from construction sites.

An extremely rare complication during carotid artery stenting using a Wallstent: Migration of a stent holder of a Carotid Wallstent

Background Carotid artery stenting (CAS) is an established treatment for internal carotid artery stenosis (ICS). The Carotid Wallstent is commonly used as a stent device in CAS procedures. Rare complications associated with the use of the Carotid Wallstent in CAS procedures include delayed shortening and incomplete stent expansion due to displacement of a marker ring. However, there have been no previous reports of a stent holder becoming unpredictably detached from a Carotid Wallstent during a procedure, requiring the additional deployment of another Carotid Wallstent. Case presentation The case of a 72-year-old man with progressive ICS is described. Since the ICS was resistant to medical treatment, CAS was planned to prevent ischemic events. During the procedure, a Mo.Ma Ultra and a carotid guardwire were used for proximal and distal protection, respectively. Following the introduction of those protective devices, a Carotid Wallstent was deployed at the stenotic lesion of the ICS. After the deployment of the Carotid Wallstent, a stent holder unpredictably detached was identified in the lumen of the Carotid Wallstent. Since it was impossible to mechanically retrieve the detached stent holder, another Carotid Wallstent was deployed to trap the substance. Postoperatively, the substance was identified as a stent holder of the first Carotid Wallstent. Conclusion This is the first report of an extremely rare complication concerning a Carotid Wallstent in CAS.

Lattice use in rugby headguards

This project is related to the design of rugby headguards. The World Rugby regulations limit the ability of headguards to reduce impact force. As such, World Rugby approved headguards are not intended to reduce the risk of serious injuries, like concussion or skull fracture. Rather, current headguards only limit the risk of superficial injuries to the soft tissue, like lacerations and contusions. With concussions linked to CTE (Chronic traumatic encephalopathy), an improvement in headguards could lead to an increased quality of life for all rugby players. With about a quarter of all rugby union injuries being concussion in the 2021/2022 season, there is justification to explore new headguard designs with potential to reduce the risk of such injuries. With World Rugby and the RFL recently introducing new rules for tackle height to try to reduce concussion rates, headguards that offer more protection could also help to reduce concussion rates. A lattice is a structure made from connected cells. When used within protective devices, lattices have potential advantages over the materials traditionally used, such as foams, from reducing the overall mass to allowing forces to be spread more evenly throughout the structure. The aim of this study was to design and comparatively impact test a lattice against foam in relation to rugby headguards. Prior data was limited as most studies on lattices focused on combining materials to have either a hollow lattice or a filled lattice which is not applicable to this study due to World Rugby regulations on protective equipment which states no sandwich material. The FEA results show that the force is more equally distributed through the lattice then it is foam allowing a lower force to hit the base.

Impact of Cerebral Embolic Protection Devices on Disabling Stroke After TAVR: Updated Results From the STS/ACC TVT Registry.

Cerebral embolic protection devices (EPDs) were developed to mitigate the risk of stroke during transcatheter aortic valve replacement (TAVR), but their benefit remains unproven. In the PROTECTED-TAVR trial (Stroke Protection With Sentinel During Transcatheter), EPD use did not reduce periprocedural stroke (primary study outcome) but led to a 62% reduction in the secondary end point of disabling stroke. Given these results, the impact of EPDs during TAVR remains unclear. We used STS/ACC TVT registry data to examine the association between EPD use and a proxy for disabling stroke among transfemoral TAVR patients between January 2018 and June 2023. The primary outcome was in-hospital disabling stroke-defined as stroke associated with either in-hospital death or discharge to a nonhome location. We evaluated the association between EPD use and disabling stroke using instrumental variable analysis with a site-level preference for EPD use as the instrument-a quasi-experimental approach that can support causal inference. In addition, we performed a propensity score-based comparison using overlap weighting as a secondary analysis. The study population consisted of 414 649 patients of whom 53 389 (12.9%) received an EPD. The unadjusted rate of in-hospital disabling stroke was 0.7% among the EPD group and 0.9% in the no-EPD group. EPD use was associated with a reduction in disabling stroke in both instrumental variable analysis (relative risk, 0.87 [95% CI, 0.73-1.00]) and propensity-weighted analysis (odds ratio, 0.79 [95% CI, 0.70-0.90]) but was not associated with a reduction in nondisabling stroke. In subgroup analyses, the benefit of EPD was greater among those with versus without prior stroke (Pinteraction<0.05 for both instrumental variable and propensity-weighted analyses). In the largest study to date, among patients undergoing TAVR, EPD use was associated with a small, borderline significant reduction in stroke associated with death or discharge to a nonhome location (a proxy for disabling stroke) that is likely to be causal in nature. Taken together with previous mechanistic and clinical studies, these findings provide credible evidence that EPDs benefit patients undergoing TAVR.

Lightning-induced voltages on low-voltage distribution lines

Special attention has been drawn to transients in low-voltage systems in recent years. As the surge withstand capabilities of low-voltage networks are much lower than those of medium-voltage lines, they are more susceptible to lightning-caused disturbances. One of the primary sources of overvoltages is related to indirect lightning strokes. Such overvoltages are highly dependent on the soil characteristics and generally tend to increase with the soil resistivity. Considering realistic conditions, this paper discusses the effects of different parameters on the phase-to-ground and phase-to-neutral lightning-induced voltages on the low-voltage side of a typical distribution transformer. In the case of high-resistivity soils or high ground resistance values, phase-to-ground voltages induced by indirect strokes can reach several tens of kilovolts. Phase-to-neutral voltages higher than 5 kV may be common if surge protective devices are not applied.

Interventions for renal artery stenosis: Appraisal of novel physiological insights and procedural techniques to improve clinical outcome.

Randomized clinical trials failed to show additional benefit of renal artery stenting on top of medical therapy. Instead of writing an obituary on renal artery stenting, we try to explain these disappointing results. A transstenotic pressure gradient is needed to reduce renal perfusion and to activate the renin-angiotensin-aldosterone system. In only a minority of patients included in trials, a transstenotic pressure gradient is measured and reported. Like the coronary circulation, integration of physiological lesion assessment will allow to avoid stenting of non-significant lesions and select those patients that are most likely to benefit from renal artery stenting. Renal artery interventions are associated with peri-procedural complications. Contemporary techniques, including radial artery access, no-touch technique to engage the renal ostium and the use of embolic protection devices, will minimize procedural risk. Combining optimal patient selection and meticulous technique might lead to a netto clinical benefit when renal artery stenting is added to optimal medical therapy.

Modeling of double ground fault modes in power supply systems of non-traction consumers of railway transport

THE PURPOSE. Development of digital models to determine the modes of double ground faults in 6-10 kV overhead signaling lines supplying signaling, centralization and automatic blocking facilities.METHODS. To create the models, methods of multiphase modeling of electric power systems were used, based on the use of lattice equivalent circuits from RLCelements connected according to complete graph circuits. For modeling, the industrial software package Fazonord, developed at the Irkutsk State Transport University, was used.RESULTS. The developed models provide correct accounting of all factors influencing the modes of double ground faults, including increased electromagnetic influences of the traction network. In contrast to known approaches, the dynamics of changes in these influences caused by variations in traction loads during train movement are modeled.CONCLUSION. The proposed approach to modeling double ground fault modes is universal and can be used for standard traction power supply systems, as well as promising high-voltage traction networks. The results obtained can be used in practice to configure relay protection devices for overhead signaling lines in order to reliably detect double ground fault modes and take measures to eliminate them. In addition, the modeling methodology presented in the article can be used when selecting measures to improve the reliability of power supply to signaling and automatic blocking facilities that ensure the safety of train traffic, as well as to develop methods and algorithms for determining distances to places of double ground faults in overhead power lines feeding signaling facilities , centralization and autoblocking. The presented results confirmed the effectiveness of the proposed approach for modeling double ground fault modes.