Underground Cables Research Articles

Underground Cable Fault Detection

Underground cables play a crucial role in delivering electricity, ensuring a dependable power supply in both urban and industrial regions. However, detecting and resolving faults in these cables can be difficult due to their hidden placement. This project aims to develop an effective underground cable fault detection system that accurately identifies fault locations, reducing downtime. The system will combine electrical principles with modern sensing technologies to detect faults such as short circuits, open circuits, and insulation issues. By injecting a small current into the cable and analyzing the resulting voltage drop, the system will calculate the distance to the fault from the measurement point. Using a microcontroller along with sensors and signal processing units, it will determine and display the fault location in kilometers. Real-time fault detection will significantly decrease maintenance time and costs by quickly locating problem areas, enabling faster repairs and reducing power outages. This project aims to improve the efficiency and reliability of power transmission systems. Additionally, the system can be integrated with communication technologies for remote monitoring, allowing utility companies to detect and manage faults from centralized control centers.

2023: a soil odyssey–HeAted soiL-Monoliths (HAL-Ms) to examine the effect of heat emission from HVDC underground cables on plant growth

BackgroundThe use of renewable energy for sustainable and climate-neutral electricity production is increasing worldwide. High-voltage direct-current (HVDC) transmission via underground cables helps connect large production sides with consumer regions. In Germany, almost 5,000 km of new power line projects is planned, with an initial start date of 2038 or earlier. During transmission, heat is emitted to the surrounding soil, but the effects of the emitted heat on root growth and yield of the overlying crop plants remain uncertain and must be investigated.ResultsFor this purpose, we designed and constructed a low-cost large HeAted soiL-Monolith (HAL-M) model for simulating heat flow within soil with a natural composition and density. We could observe root growth, soil temperature and soil water content over an extended period. We performed a field trial-type experiment involving three-part crop rotation in a greenhouse. We showed that under the simulated conditions, heat emission could reduce the yield and root growth depending on the crop type and soil.ConclusionsThis experimental design could serve as a low-cost, fast and reliable standard for investigating thermal issues related to various soil compositions and types, precipitation regimes and crop plants affected by similar projects. Beyond our research question, the HAL-M technique could serve as a link between pot and field trials with the advantages of both approaches. This method could enrich many research areas with the aim of controlling natural soil and plant conditions.

An investigation on NGR failure in Indian smart cities while replacing the existing overhead lines by underground cables

Abstract Nowadays, Indian power distribution companies (PDCs) are implementing smart distribution networks. Older cities are becoming smarter as per the recent government’s policy. Existing overhead distribution lines are being replaced by underground cables as an essential criterion of a smart city. One of the main problems arising in this process is the overheating of the neutral grounding resistor (NGR) in 11 kV distribution systems, even in normal conditions. NGRs, placed inside the substations, are overloading the air conditioning and exhaust systems of the substation. Sometimes failure of the NGR occurs due to overheating. In this paper, a comprehensive investigation has been carried out to reach the roots of this problem. It is observed that long underground cables have a higher ground capacitance than overhead distribution lines. Due to the higher cable capacitance, the third harmonic current circulates through neutral, which overheats the NGR even in normal conditions. The situation becomes worse when the substation runs on diesel generators (DGs) in an isolated state under main grid failure, as a higher amount of third-harmonic current circulates depending on the type of winding and pitch factor of the DGs. Different solutions are proposed, and their advantages and disadvantages are analyzed. Finally, the rating of the NGR is modified, and louvers-cooling fan arrangement is preferred for the running substation.

Calculation of Maximum Permissible Load of Underground Power Cables–Numerical Approach for Systems with Stabilized Backfill

The maximum permissible load of underground power cables (known in U.S. engineering as “ampacity”) is a function of many parameters, in particular, the thermal resistivity of the native soil. If this resistivity is relatively high, thermal/stabilized backfill is applied, i.e., another material is placed around the cables, providing favourable conditions for heat transfer to the environment. It has a positive impact on the reliability of the power supply and favours the operational durability of the cables. In design practice, however, there is a difficult task—correct determination of the ampacity of the cable line depending on the thermal parameters and the geometry of the backfill. Therefore, this article presents the results of a numerical analysis to determine the ampacity of cable lines in which stabilized backfill is used. A new mathematical relationship is proposed that allows the correction of the ampacity of cable lines depending on their cross-section as well as the thermal and geometric parameters of the cable surroundings.

Experimental determination of soil thermal conductivity for design of underground cables

The dimensioning of underground extra-high voltage direct current transmission lines (HVDC) requires detailed knowledge of soil properties, particularly thermal conductivity, to optimise cable spacing and minimise project costs and environmental impact. Given the absence of an internationally standardised procedure for testing soil thermal conductivity, a novel approach was developed as part of the SuedLink project - a 700 km long underground power line which will transmit renewable wind energy between northern and southern Germany. The unique aspect of this methodology lies in its ability to deliver reproducible results of the thermal conductivity of a soil across the entire water content spectrum. This allows the use of realistic thermal conductivity values, as opposed to the current use of overly conservative values in the design of underground power lines. Additionally, the highly efficient testing configuration enables the test to effectively be rolled out on a large scale as was shown with over 6000 tests done on the SuedLink project. This article explains the thermal conductivity test procedure and the evaluation of the raw-data obtained from these tests.

Development of a high current density, high temperature superconducting cable for pulsed magnets

Abstract A low AC loss Rare Earth Barium Copper Oxide (REBCO) cable, based on the VIPER cable technology has been developed by Commonwealth Fusion Systems for use in high field, REBCO based tokamaks. The new cable is composed of partitioned and transposed copper ‘petals’ shaped to fit together in a circular pattern with each petal containing a REBCO tape stack and insulated from each other to reduce AC losses. A stainless steel jacket adds mechanical robustness—also serving as a vessel for solder impregnation—while a tube runs through the middle for cooling purposes. Additionally, fiber optic sensors are placed under the tape stacks for quench detection. To qualify this design, a series of experiments were conducted as part of the SPARC tokamak Central Solenoid Model Coil program—to retire the risks associated with full scale, fast ramping, high flux HTS Central Solenoid (CS) and Poloidal Field (PF) coils for tokamak fusion power plants and net energy demonstrators. These risk study and risk reduction experiments include (1) AC loss measurement and model validation in the range of ~5 T/s, (2) an IxB electromagnetic loading of over 850 kN/m at the cable level and up to 300 kN/m at the stack level, (3) a transverse compression resilience of over 350 MPa, (4) manufacturability at tokamak relevant speeds and scales, (5) cable to cable joint performance, (6) fiber optic based quench detection speed, accuracy, and feasibility, and (7) overall winding pack integration and magnet assembly. The result is a cable technology, now referred to as PIT VIPER, with AC losses that measure fifteen times lower (at ~5 T/s) than its predecessor technology; a 2% or lower degradation of critical current (Ic) at high IxB electromagnetic loads; no detectable Ic degradation up to 570 MPa of transverse compression on the cable unit cell; end to end magnet manufacturing, consistently producing Ic values within 7% of the model prediction; cable to cable joint resistances at 20 K on the order of ~15 nΩ; and fast, functional quench detection capabilities that do not involve voltage taps. This cable technology will be tested comprehensively in a Central Solenoid Model Coil to prove its readiness for compact, high field tokamak operation.

Elucidating the increased ohmic resistances in zero-gap alkaline water electrolysis

This study investigates the increased ohmic resistances observed in zero-gap alkaline water electrolyzers, aiming to provide insights that can help enhance electrolyzer efficiency and enable operation at higher current densities. Electrochemical impedance spectroscopy (EIS) has been employed in combination with chronopotentiometry, utilizing a custom-designed flow cell with nickel perforated electrodes and a Zirfon UTP 500 diaphragm. Observed differences in area-ohmic resistance values obtained through I-V fitting and EIS, are ascribed to a non-linear Tafel slope at higher current densities. Ohmic resistance values measured with EIS are up to 27% higher than the ex-situ determined value, a significantly smaller percentage than expected based on previous studies. The presence of bubbles outside and inside the diaphragm is identified as the key factor contributing to this increased resistance. We recommend the use of an improved fitting approach, accounting for non-linear Tafel behavior, and the use of a 4-terminal configuration when performing EIS measurements to minimize cable and contact resistance.

Deep learning-based fault detection and location in underground power cables using resonance frequency analysis

Deep learning-based fault detection and location in underground power cables using resonance frequency analysis

Analysis of Field Trial Results for Excavation-Activities Monitoring with φ-OTDR.

Underground telecommunication cables are highly susceptible to damage from excavation activities. Preventing accidental damage to underground telecommunication cables is critical and necessary. In this study, we present field trial results of monitoring excavation activities near underground fiber cables using an intensity-based phase-sensitive optical time-domain reflectometer (φ-OTDR). The reasons for choosing intensity-based φ-OTDR for excavation monitoring are presented and analyzed. The vibration signals generated by four typical individual excavation events, i.e., cutting, hammering, digging, and tamping at five different field trial sites, as well as five different mixed events in the fifth field trial site were investigated. The findings indicate that various types of events can generate vibration signals with different features. Typically, fundamental peak frequencies of cutting, hammering and tamping events ranged from 30 to 40 Hz, 11 to 15 Hz, and 30 to 40 Hz, respectively. Digging events, on the other hand, presented a broadband frequency spectrum without a distinct peak frequency. Moreover, due to differences in environmental conditions, even identical excavation events conducted with the same machine may also generate vibration signals with different characteristics. The diverse field trial results presented offer valuable insights for both research and the practical implementation of excavation monitoring techniques for underground cables.

A study of XLPE insulation failure in power cables under electromagnetic stress

Underground cables with cross-linked polyethylene (XLPE) insulation are integral to medium voltage (MV) power transmission systems, ensuring continuous electricity supply amidst operational challenges and environmental conditions. However, the reliability of these cables can be compromised over time due to aging and installation-related factors, particularly at joints and terminations. This study offers a comprehensive analysis of how various defects, including spherical air voids, pinholes, and irregularities in semiconducting layers, affect electric field and potential distributions within cable end terminations using COMSOL Multiphysics software. Through detailed simulations, the study identifies significant variations in electric field strength caused by these defects, highlighting critical stress concentration areas. In this study, it assumed that the cable and termination have the same cross-section. By analyzing these simulations, the study provides insights into optimizing cable design and installation practices to enhance the reliability and lifespan of underground power transmission systems. This study introduces a novel approach by combining advanced COMSOL Multiphysics simulations with a detailed analysis of defect impacts on electric field distributions, offering new insights into stress concentrations and degradation at cable terminations. Simulation outcomes reveal significant variations in electric field strengths due to air voids and pinholes in cables and terminations: for 2 mm voids, up to 2.45×106 V mm−1 near the conductor and 56.5 V mm−1 at termination. These findings enhance the understanding of XLPE-insulated cable behavior under electromagnetic stress, providing a basis for mitigating failures and improving overall system performance.

Optimization of Phase Change Materials as Backfill Materials for Underground Cable

Optimization of Phase Change Materials as Backfill Materials for Underground Cable

High-frequency transients in buried insulated wires: Transmission line simulations and experimental validation

This paper presents experimental results on the transient response of a buried insulated wire subjected to fast transient signals. It reports measurements of voltage and current at the sending end, as well as the voltage at the receiving end of the insulated wire. The obtained experimental results are utilized to assess the accuracy of recent formulations proposed for computing the ground-return impedance and admittance of underground cables, which are important for simulation of transients using models based on the transmission line theory. The good agreement between measurements and simulations bolsters confidence in incorporating these newly proposed expressions for computing the cable's ground-return parameters into EMT-type simulators.

The dynamic resistance of muti-layer conductor on round core cables for SMES systems

The conductor on round core (CORC) cables with multi-layer structure show great potential for superconducting magnetic energy storage (SMES) because of their low AC losses and large current carrying capacity. The dynamic resistance is an important electro-magnetic property of CORC cables for SMES. Considering that experimental results of multi-layer CORC cables are usually difficult to obtained, numerical model is an efficient method to demonstrate their electro-magnetic properties. In the work, a numerical model is proposed to illustrate the dynamic resistance of the multi-layer CORC cables. Then, an analytical model using method of rotating magnetic field is proposed to provide mathematical expressions for computing the dynamic resistance, which verifies the numerical model. According to the numerical model, the impacts of DC current and AC magnetic field on dynamic resistances of the multi-layer CORC cables are investigated respectively. The simulation clearly illustrates the dynamic resistance characteristics of CORC cables, showing dynamic resistances and currents in individual layers. This study can serve as a valuable guidance for the implementation of multi-layer CORC cables in SMES systems.

An Electromagnetic-Thermal Modeling Method for the Joint Resistance of the CORC Cable

An Electromagnetic-Thermal Modeling Method for the Joint Resistance of the CORC Cable

Cable Modeling and DC Resistance Analysis of Terminations for 16 T Superconductor Test Facility

Cable Modeling and DC Resistance Analysis of Terminations for 16 T Superconductor Test Facility

Design and Development of A Traffic Light Simulation Model Based on Arduino Microcontroller

Congestion is one of the transportation problems with the highest percentage to occur at every intersection in all corners of the region. Efforts can be made to solve these problems by making the traffic light regulation system (APILL) in general, APILL still uses static cycle time with cable networks as interconnects between lamp poles, making it difficult to adjust the phase and cycle time referring to traffic conditions that tend to be dynamic, even requiring high procurement and maintenance costs for underground cables. Based on the above, the research team wants to create a simulation mockup of APILL whose cycle time and phase can be set through calculations on the Android platform with wireless interconnection, as well as can be used as a learning facility for cadets/I to provide an understanding of the applicable phase at the intersection, to be able to analyze the performance of an intersection and how APILL works on roads.

Enhancement of the underground cable current capacity by using nano‐dielectrics

AbstractIn most underground power cables, cross‐linked polyethylene (XLPE) is utilized as the main insulating material, while polyvinyl chloride (PVC) is usually used as a nonmetallic sheath or jacketing for the cable. Accordingly, improving the electrical and thermal characteristics of these materials leads to an increase in cable dielectric strength, besides a rise in the current capacity of the underground power cables. Thus, enhancing the thermal characteristics of cable insulation is the goal of many research studies. In this regard, increasing the current capacity of underground power cables is an essential topic for electrical distribution and transmission networks. This usually occurs by increasing the cross‐sectional area of the cable conductor, which means raising the cost of transmitting electrical energy. Another proposed alternative may be to improve the thermal properties of the dielectric material using nanotechnology to allow better dissipation of heat resulting from the cable losses. This article proposes the use of nano‐composite dielectrics to increase the current capacities of underground power cables. Nano‐fillers are used to enhance the thermal and electrical characteristics of XLPE and PVC, which represent cable dielectric materials. Accordingly, in this paper, many experiments are conducted on various nano‐dielectric materials to choose the most appropriate nano‐dielectrics for improving both the thermal and electrical properties. Hence, measurements are performed on the thermal and electrical properties of dielectric nano‐materials manufactured in the laboratory. Further, calculations of the cable's current capacities by the use of the measured properties of nano‐dielectrics are done considering several backfill soils. From the obtained measurements and calculations carried out on cable capacities, it is concluded that the use of XLPE/ZnO 5 wt.% as the insulation and PVC/ZnO 5 wt.% as the jacket material increased the cable current capacity by 6.2% for a cable of 33 kV rating, 9.2% for 66 kV cable, and 15.7% for 220 kV cable when wet clay is used as backfill soil. From the calculations carried out it is found that the use of nano‐composite dielectrics reduces the temperature of the cable components by significant values. For example, the core temperature of the 33 kV cable is reduced by 15.6°C, while for the 66 kV cable, the cable core temperature is decreased by 12.6°C, and for 220 kV the conductor temperature is reduced from 71.3°C to 58.3°C when each cable is loaded by its rating.

Collaborative international partnership: Enabling the development of a state-of-the-art minimally invasive surgical center in rural Uganda through telementoring.

Access to minimally invasive surgery (MIS) is limited in Sub-Saharan African countries. In 2019, the Mount Sinai Department of Surgery in New York collaborated with local Ugandans to construct the Kyabirwa Surgical Center (KSC), an independent, replicable, self-sustaining ambulatory surgical center in Uganda. We developed a focused MIS training program using a combination of in-person training and supervised telementoring. We present the results of our initial MIS telementoring experience. We worked jointly with Ugandan staff to construct the KSC in the rural province of Jinja. A solar-powered backup battery system ensured continuous power availability. Underground fiber optic cables were installed to provide stable high-speed Internet. The local Ugandan general surgeon (JOD) underwent a mini-fellowship in MIS and then trained extensively using the Fundamentals of Laparoscopic Surgery program. After a weeklong in-person session to train the Ugandan OR team, JOD performed laparoscopic cases with telementoring, which was conducted remotely by surgeons in New York via audiovisual feeds from the KSC OR. From October 2021 to February 2024, JOD performed 61 telementored laparoscopic operations at KSC including 37 appendectomies and 24 cholecystectomies. Feedback was provided regarding patient positioning, port placement, surgical technique, instrument use, and critical steps of the operation. There were no intra-operative complications. Postoperatively, field medical workers visited patients at home to collect follow-up information. Two superficial wound infections (3.3%) were reported in the short-term follow-up. Telementoring can be safely implemented to assist surgeons in previously underserved areas to provide advanced laparoscopic surgical care to the local patient population.

Study and measurement of magnetic emission generated by underground 400kV power cables

Study and measurement of magnetic emission generated by underground 400kV power cables

Navigation Techniques and Algorithms for Mobile Robots and Automated Guided Vehicles

Mobile robots are self-contained devices that can navigate and move around their surroundings. They observe their environment and create maps using different sensors such as lidar, Global Positioning System (GPS), and cameras. Automated Guided Vehicles (AGVs) are vehicles that can move independently utilizing different approaches such as underground cables, laser scanners, or GPS systems. This research investigates several navigation methodologies and algorithms used in AGVs and mobile robots. It focusses on the advantages of integrating lidar technology with other sensors as well as how it is used in local navigation techniques. We look at two motion planning techniques for obstacle avoidance: the Artificial Potential Field (APF) approach and the Vector Field Histogram (VFH) algorithm. Two effective techniques for finding the best routes are discussed: the A* algorithm and Dijkstra's algorithm. The various AGV types and their navigation systems (such as wired, guide, laser, vision-based, and gyro-based) are also examined in the study. Neural networks and fuzzy logic are investigated as AGV control techniques, with line following and obstacle avoidance as examples of their use. The study emphasizes how crucial precise and dependable navigation systems are to the effective and secure operation of mobile robots and AGVs.