Unshielded Cables Research Articles

Constructing a model of the influence of structural and technological inhomogeneities on electromagnetic energy losses in cables based on a twisted pair

The objects of research reported here were cables based on twisted pairs of various designs. The issue of the emergence of additional losses of electromagnetic energy is related to structural and technological inhomogeneities at the technological stage of cable production. The influence of the working capacitance of the twisted pair on the energy losses in the cables has been substantiated. A methodology was proposed for the numerical calculation of the electric field under the condition of ellipticity of the structural elements of the twisted pair. That has made it possible to determine the distortion of the electric field and the effect of inhomogeneities on the working capacitance of a twisted pair of different designs. Specifically, it was shown that for shielded structures with continuous polymer insulation, the distortion of the electric field and the growth of the working capacitance are observed to a greater extent. The need to find technological solutions to reduce the effect of screen ellipticity on cable capacitance has been emphasized. The effectiveness of capacitance regulation in the presence of inhomogeneities has been confirmed, by using foamed insulation to reduce the loss of electromagnetic energy in the cable. The effect of reducing the working capacitance and increasing additional losses under the simultaneous influence of the ellipticity of the electrical insulation and the protective polymer shell has been established, which necessitates the technological process adjustment in the manufacture of twisted pair. An applied aspect of using the results is the possibility of improving the typical technological process of manufacturing twisted pairs to reduce additional losses of electromagnetic energy at the final technological stage of cable production. The adequacy of the numerical studies was confirmed by experimental dependences of the attenuation coefficient and additional energy losses of the unshielded cable in the frequency range up to 100 MHz

Ensuring standardized parameters for the transmission of digital signals by twisted pairs at the technological stage of manufacturing cables for industrial operating technologies

Introduction. In production control and control systems, buildings use many simple devices - sensors to detect light, heat, movement, smoke, humidity and pressure, mechanisms for activation and control of switches, closing devices, alarm, etc. - «operating technologies» (OT). Different communication protocols and field tire technologies, such as Modbus for conditioning systems, Bacnet for access control and Lonworks for lighting, have been traditionally used and used for their connection. Network fragmentation leads to the need to use gateways to transform protocols when creating a single automation system, which complicates the implementation of complex control systems for any object. At the same time, information networks are unified, but the Ethernet protocol used in them for operating technologies for various reasons (technological, cost) has not been widespread. Due to its high bandwidth compared to existing field tire networks, industrial Ethernet is significantly capable of increasing flexibility in the implementation of additional functions in OT. Modern industrial Ethernet networks are based on non - shielded and shielded twisted pair category 5E cables. The presence of additional metal screens in the structure of twisted pair causes the increase in electrical resistance of conductors due to the effect of closeness, the electrical capacity, and the ratio of attenuation in the range of transmission of broadband signals. Purpose. Substantiation of the range of settings of technological equipment to ensure standardized values of the extinction coefficient and immunity based on the analysis of the results of measurements in a wide frequency range of electrical parameters of shielded and unshielded cables for industrial operating technologies. Methodology. Experimental studies have been performed for statistically averaged electrical parameters of the transmission of pairs for 10 and 85 samples of 305 meters long and shielded cables of category 5e, respectively. It is determined that in the frequency range from 1 to 10 MHz, unshielded cables have less values of the attenuation coefficient. In the range of more than 30 MHz, the shielded cables have smaller values of the attenuation due to the influence of the alumopolymer tape screen. It is established that the coefficient of paired correlation between asymmetries of resistance and capacity of twisted pairs is 0,9735 - for unshielded and 0,9257 - for shielded cables. The impact has been proven to a greater extent asymmetry of resistance the pairs on the increasing noise immunity of cables. The influence noise interference on the deviation of the diameter and electrical capacity of the isolated conductor from the nominal values in the stochastic technological process is analyzed. The strategy of technological process settings to ensure the attenuation and the noise immunity in the high -frequency range is substantiated. Practical value. Multiplicative interference, caused by random changes in the stochastic technological process, can lead to a deviation of diameter 2 times from the nominal value at level of probability at 50 %. The equipment settings of the technological equipment must guarantee the coefficient of variation capacity of the insulated conductor at 0.3 % for high level of noise immunity.

Design of a Three-Phase Three-Level Back-to-Back Bridge Interconnection-Based Filter Scheme

This article proposes a systematic design methodology for a back-to-back bridge structure to be used with three-phase bidirectional AC-AC converters (also called an active front end) feeding a motor with long unshielded cables. The bridge provides a path for circulating common-mode (CM) harmonics, resulting in low motor-bearing voltage, suppression of motor winding over-voltage, superior low-frequency conducted emissions attenuation, and wide band performance. The proposed filter structure is designed using simplified sets of derived analytical attenuation pertaining to different groups of harmonics. Consequently, each filter component is optimized for low weight using specific core materials depending on current-ripple content. Following the physical design, parasitic models for the converter, filter, motor, and long cables are developed in the time domain to allow prediction of CM and differential-mode (DM) voltages as well as reducing the filter’s impact on high-frequency emissions. The overall design methodology is validated through emissions characterization using a 12-kW rated three-level neutral point clamped (NPC) converter in a back-to-back configuration.

Coupling Analysis of Shielded and Unshielded Star Quad Cables Excited by an Intentional Electromagnetic Pulse

Coupling analysis of shielded and unshielded star quad cables excited by an intentional electromagnetic pulse (IEMP) is investigated using the transmission line theory-based perturbation technique. A detailed modal analysis is presented to obtain the modal per-unit-length parameters of the modal signals in such shielded/unshielded star quad cables. Due to their geometrical balanced structures, with opposite wires used for +leg and −leg to transfer the differential-mode (DM) signal, the external coupling is dramatically suppressed. Moreover, stochastic analyses based on the Monte Carlo simulation are also performed to study the sensitivity of the induced common-mode (CM) and DM currents, due to the deformation effects of the twisting structure of the cable. It is found that the induced CM and DM currents are slightly affected by the twisting deformation of the cable because the interference cancelations do not mainly depend on the twisting loops of the cable. In particular, time domain analysis is performed to study the field-to-wire coupling of the star quad cables exposed to an IEMP, where the worst-case waveform signals in the presence of an IEMP attack are captured and analyzed.

Miniature Crack or Damage Detection on Cable Insulation and Jacket Using Conformal Surface Wave Reflectometry

This letter introduces the study and application of a conformal surface wave launcher array to detect miniature insulation and/or jacket damage on unshielded cables. Simulation and experimental results are presented that demonstrate that with the proposed concept, very small instances of damage at various distances along power cables can be detected. Effects of damage detection feasibility in the presence of other cables in proximity and for cables containing semiconducting screen are also presented.

Aging Assessment of XLPE/CSPE LV Nuclear Power Cables Under Simultaneous Radiation–Mechanical Stresses

The preliminary results of an ongoing laboratory cable aging program are reported in this article. This work deals with the effect of simultaneous radiation–mechanical​ aging on the electrical and mechanical properties of XLPE/CSPE low-voltage unshielded nuclear power cables. The dielectric response, particularly the complex permittivity and the polarization/depolarization current (PDC), were investigated. At the same time, the Shore D hardness measurement was conducted as a mechanical property test. Cable samples were coincidingly aged under a bending diameter of 15 cm and a total dose of 240 kGy γ-irradiation at a 0.5 kGy/h dose rate. The real and imaginary parts of permittivity were investigated over a frequency range from 200 μHz to 1 Hz. The electrical parameters presented a monotonic increase with aging. Besides, the cable hardness has increased with increasing the radiation dose. Furthermore, the insulation conductivity has risen with aging, which strongly correlates with the imaginary permittivity at 1 mHz. The obtained results showed an excessive degradation of the cable samples under the combined radiation–mechanical aging as the insulation electrical and mechanical properties showed a good agreement.

EMI Filter Design for a Three-Phase Buck–Boost Y-Inverter VSD With Unshielded Motor Cables Considering IEC 61800-3 Conducted and Radiated Emission Limits

The standard converter concept employed in variable speed motor drives is the two-level three-phase Si insulated-gate bipolar transistor voltage source inverter with its switch nodes connected to the motor terminals via shielded cables to avoid excessive high-frequency noise emissions. However, high dv/dt pulses of the inverter pose substantial stresses on the motor, which are further intensified by the ever-faster switching speeds of wide band-gap semiconductors, hence promoting interest in inverters with full-sinewave output filters, which potentially enable the use of inexpensive unshielded motor cables. However, the IEC 61800-3 standard dictates stringent conducted and radiated emission limits on unscreened power interfaces. In this article, a dc input and ac output filter structure allowing operation with unshielded cables is derived for a phase-modular 11-kW buck-boost Y-inverter motor drive system employing 1.2-kV SiC MOSFETs with a switching frequency of 100 kHz. First, regulations and measurement techniques for conducted and radiated emissions of motor drives are analyzed. Next, the operating principle of the Y-inverter is described and an electromagnetic interference equivalent circuit is derived, followed by a systematic filter design. Finally, measurements are conducted on an ultracompact hardware prototype of the converter system with 12 kW/dm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> (197 W/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ) power density, where the results indicate full compliance with the IEC 61800-3 conducted and radiated emission limits for operation with unshielded dc supply and motor cables in a residential area.

Aging Mechanisms and Non-Destructive Aging Indicators of XLPE/CSPE Unshielded LV Nuclear Power Cables Subjected to Simultaneous Radiation-Mechanical Aging.

Low-voltage cable systems in nuclear power plants are key components that have a crucial role in the safe operation of nuclear facilities. Thus, the aging management of cable systems is of utmost importance as they cannot easily or economically be replaced or upgraded. Therefore, there is a continuous need to develop reliable non-destructive condition monitoring techniques, mostly based on the measurement of the dielectric properties of cable insulation. This paper introduces the changing of dielectric and mechanical properties of XLPE insulated and CSPE jacketed unshielded low-voltage nuclear power plant power cable in case of simultaneous mechanical and radiation aging. The cable samples were bent and exposed to 400 kGy gamma irradiation with a 0.5 kGy/hr dose rate. Dielectric response (real and imaginary permittivity) in the 0.1 Hz−1 kHz frequency range, extended voltage response (EVR), and the Shore D hardness test techniques were measured to track aging. The electrical and mechanical parameters have increased monotonically with aging, except the imaginary permittivity, which increased only at frequencies higher than 10 Hz. Furthermore, different quantities were deducted based on the frequency and permittivity data. The electrical parameters and deducted quantities correlation with aging and mechanical parameters were investigated. Since the deducted quantities and the electrical parameters are strongly correlated with absorbed dose and mechanical properties, the electrical measurements can be applied as a non-destructive aging indicator for XLPE/CSPE unshielded low-voltage nuclear power cables.

The Analysis of Shielding Effectiveness of the enclosure of an EMI-Filter for a Spacecraft Power Bus

In this paper, the shielding enclosure of an electromagnetic interference (EMI-) filter for a spacecraft power bus was analysed for shielding effectiveness (SE). By using an electro- dynamic approach, the authors conducted simulation in the frequency domain taking into account losses in the shield. The investigation covered the performance of the shielding enclosure with and without the connected cables and the in uence of apertures formed between the enclosurebase and its cover. It was found that the smallest value of the SE of the enclosure is observed for the configuration with unshielded cables. However, whilst maintaining shielding integrity, attenuation of at least 88 dB in the frequency range from 0 to 20 GHz was achieved. In the study, the authors analysed the in uence of printed circuit boards of EMI-filter in the shielded volume on SE of the enclosure and found that they have a weak effect on the SE. In conclusion, there is some practical guidance on the design of similar EMI-protection devices.

Electrical and Mechanical Condition Assessment of Low Voltage Unshielded Nuclear Power Cables Under Simultaneous Thermal and Mechanical Stresses: Application of Non-Destructive Test Techniques

Low voltage cables play a crucial role in the safe and reliable operation of nuclear power plants. This paper discusses the effect of simultaneous combined thermal and mechanical stresses on the overall insulation of unshielded low voltage power cables used in nuclear power plants. Cable samples based on XLPE/CSPE insulation were exposed to thermal-mechanical combined accelerated aging tests for an extended period lasted to 907 hours. Time and frequency domain dielectric spectroscopy were applied to reveal the degradation level of the core insulation and jacket due to combined stresses. The former technique was conducted through the measurement of the decay and return voltage slopes, while the latter technique was based on the measurement of the complex permittivity. Moreover, the mechanical properties of the cable insulation were investigated by applying the measurement of the Shore D hardness. The results showed that the combined aging affects both the electrical and mechanical properties of the overall insulation. The complex permittivity at 100 Hz, the decay voltage slope, and the hardness had an upward trend with aging, while the return voltage slope showed an inverse trend. In addition, the results of the electrical and mechanical measurements showed strong correlation with aging time and further correlation was observed between the dielectric and mechanical properties. The correlation between aging time and test results suggests that the presented test methods are promising tools for in situ condition monitoring of low voltage unshielded cables in nuclear power plants.

Subnanosecond Time Synchronization Using a 100Base-TX Ethernet Transceiver and an Optimized PI-Clock Servo

This work presents a real-time 100Base-TX Ethernet physical layer (PHY) transceiver chip implemented in a 180-nm technology. The PHY chip implements highly accurate hardware timestamping by using an 8-bit digital-to-phase converter (DPC) generating 256 phases of the 125 MHz system clock. Using these clock phases, spaced 31.25 ps apart from each other, phase relationships can be evaluated to timestamp ingress and egress frames with improved resolution. Connected by up to 120-m-long category five unshielded twisted-pair cables, two of these PHY chips are used to demonstrate the synchronization in a two-node scenario. A proportional-integral (PI)-clock servo is used at the slave for the synchronization. To optimize the performance, the parameters of the controller need to be chosen carefully. To do so, a simple model is used to find a suitable bandwidth of the controller as a tradeoff between the noise of the timestamping and the noise of the oscillator. All in all, a synchronization accuracy with a standard deviation of only 64 ps and a mean offset of well below 100 ps is achieved in the given scenario. To the best of our knowledge, this is the highest synchronization accuracy over copper-based Ethernet reported to date.

INCREASING NOISE IMMUNITY OF CABLES FOR FIRE PROTECTION SYSTEMS

Introduction Technical means of fire protection systems are capable of operating at data rates from tens to hundreds of Kbit/s with components of a digital signal in the frequency spectrum up to several tens of MHz. Appropriate cable infrastructure with a high level of noise immunity is required to transmit broadband digital signals. Purpose: Substantiation of ways to increase noise immunity of cables based on twisted pairs for modern fire protection systems with the ability to transmit digital signals in the frequency spectrum up to 100 MHz. Methodology: A comparison is made of the influence of the twisting step of pairs in unshielded 4-pair and multi-pair shielded balanced cables on the parameters of electromagnetic effects. It has been experimentally shown that twisting each pair with different steps provides a higher level of noise immunity of cables based on twisted pairs. Practical value: The frequency dependencies of the near end crosstalk in 10-, 30- and 4-pair balanced cables are shown. The influence of the common shield on the attenuation coefficient of the shielded 4-pair cable is established.

Impact of twisting rate in 10 pairs of unshielded twisted-pair copper cables on insertion loss and crosstalk coupling for G.fast technology

An ultrafast digital subscriber line (DSL) technology called G.fast is important for ultrafast broadband Internet access services. In G.fast, the existing cable bundles installed for 250 m from the distribution point to the customer’s premises are used to support the gigabit data transmission (aggregated 1 Gbit/s) for frequency up to 106 MHz or 212 MHz. Since unshielded cable is used, and the frequency is 12 times higher compared to the very high-speed DSL2 (VDSL2), it is important to investigate the cable performance in terms of insertion loss and crosstalk coupling. In this paper, the impact of cable twisting rate on 10 pairs of unshielded twisted-pair copper cables for a small copper bundle on insertion loss and crosstalk coupling is investigated. A simulation model is developed based on the standard cable installed in Malaysia. The model reliability is validated by comparing the obtained result with the published result in the literature. Besides, the twisting rate of 100 m cable is manipulated by changing its lay size to determine its impact on insertion loss and crosstalk coupling. The results showed that a high twisting rate can reduce the far-end crosstalk but increase both the insertion loss and near-end crosstalk.

ERROR OF CONTROL OF ELECTRICAL INSULATION STRUCTURES BY DIELECTRIC ABSORPTION PARAMETERS ACCORDING TO THE CONCEPT OF UNCERTAINTY OF MEASUREMENTS

Introduction. Measurements on alternating current of dielectric absorption parameters – capacitance and dielectric loss tangent tgδ allow us to evaluate the quality of insulation of cables, electrical machines, transformers, etc., both at the technological stage of manufacture and in operation. An increase in the reliability of the measurement result of the parameters is provided by a decrease in the measurement error due to the improvement of measuring instruments and measurement methods and an increase in the number of measurements Purpose. The estimation of the error of control of electrical insulation structures by dielectric absorption parameters in accordance with the concept of measurement uncertainty. Methodology. The error of measurements of the capacitance and the tangent of the dielectric loss angle is estimated using the example of a twisted unshielded pair of category 5e. A statistical analysis of the results of multiple measurements of the capacitance and the tangent of the dielectric loss angle of an unshielded cable is carried out. The linear regression equations for the measured values of the dielectric absorption parameters of the number of measurements are obtained. Practical value. Ensuring unity in the methods for estimating the error of measurement results, both when using the traditional concept of «measurement result error» and when introducing the concept of «measurement result uncertainty» into practice, it will allow to unambiguously interpret and correctly compare the results of measurements of the capacitance and tangent of the dielectric loss angle of electrical insulation structures.

PLC Systems Under the Presence of a Malicious Wireless Communication Device: Physical Layer Security Analyses

This paper investigates the physical layer security (PLS) of a broadband in-home power line communication (PLC) system when a malicious wireless device tries to eavesdrop private messages exchanged between two PLC devices. Such a security issue arises when electric power circuits, which are used for data communication, are constituted by unshielded power cables. In this regard, the hybrid wiretap channel model for formulating achievable secrecy rate and secrecy outage probability is considered. Additionally, a data set of channel estimates and measured additive noises obtained from a measurement campaign carried out in several in-home facilities is used for providing practical results, which can offer direction for dealing with the security aspects of broadband in-home PLC systems in the physical layer perspective. The attained results show high values of secrecy outage probability for all chosen values of target secrecy rate and total power transmission (practical and theoretical) when the PLC devices are far from each other and the eavesdropper is close to the PLC transmitter (i.e., the distance is shorter than 2 meters). Overall, the numerical results show that the vulnerability of broadband in-home PLC systems, in terms of PLS, is relevant when practical values of total transmission power apply. Therefore, a rethinking of the use of unshielded power cables or new designs of the broadband in-home PLC system deserves special attention for ensuring security at the physical layer.

Application of Non-Destructive Condition Monitoring Techniques on Irradiated Low Voltage Unshielded Nuclear Power Cables

In this paper, the effect of radiation stress on the overall degradation of jacket and insulation of low voltage unshielded power cable used in nuclear power plants is discussed. The XLPE insulated and CSPE jacketed cable samples were exposed to a total dose of 400 kGy γ-irradiation with 0.5 kGy/h dose-rate. Dielectric spectroscopy; complex permittivity, and extended voltage response; namely slopes of decay and return voltages were used to study the effect of the irradiation on the cable with an aim to establish the application of these techniques for a non-destructive condition monitoring of the unshielded cables. Shore D hardness was also used to investigate the mechanical characteristic of the cable. It was observed that the radiation stress affected the electrical and mechanical properties of the cable polymeric components i.e. insulation and jacket. The imaginary part of permittivity at low frequency; 100 Hz, the slope of return voltage, and hardness showed a significant increase with absorbed dose showing the effect of irradiation on the jacket and insulating material, as well. A strong correlation was observed between the imaginary part of permittivity at 100 Hz, slopes of return voltage, and hardness. The results show the dielectric measurement techniques are potential non-destructive condition monitoring methods for the unshielded low voltage nuclear power plant power cables for on-site diagnosis.

Time-Domain Gating Applied to the Quantitative Evaluation of Soft Defects in Embedded Electric Cables

The recent development of reflectometry-based methods for the diagnosis of embedded cables has highlighted the need for the full frequency characterization of soft faults. The purpose of this paper is to report for methods and laboratory experiments for deembedding the fixture effects of connectors in a defective embedded electrical line. It is shown how the two-window time-gating method can be applied to the diagnosis of real embedded electrical cables and its benefit concerning the quantitative estimation of the frequency signature of soft defects compared to the single-window gating technique. A new method is also introduced showing how, in such cases, the prior healthy line measurement can be approximated from the defective line measurement. The studied soft defects were partially unshielded coaxial cables.

Frequency-domain modeling of unshielded multiconductor power cables for periodic excitation with new experimental protocol for wide band parameter identification

A complete modeling technique for unshielded power cables is proposed. The focus is on applications where the resonance phenomena take place in electrically long cables and is originated from periodic excitation, such as power converters. The resonance problems caused by switching converters tend to become more common with the advent of wide band gap semiconductors. This paper includes a new experimental protocol specific for unshielded power cable parameter identification in a wide frequency band, from DC up to medium frequencies (tens of MHz), with an impedance analyzer. It also introduces a frequency-domain simulation tool with conversion to the time domain, via the Fourier series. This frequency-domain modeling is straightforward, and its accuracy depends only on the accuracy of the cable parameter identification.

Medium Access Control Protocols for Power Line Communication: A Survey

In the literature, the majority of research efforts in power line communication (PLC) has been focused on the physical layer in order to deal with issues such as the time varying behavior of loads in electric power systems, the presence of high power impulsive noise, the occurrence of impedance mismatching, the widespread use of unshielded power cables, and the existence of coupling losses. While some works have also been carried out on the PLC medium access control (MAC) sublayer, there are scopes for further research to address the novel demands associated with cyber physical systems that need to mitigate unfairness in resource sharing, collisions and starvation, among other issues which may degrade data communication quality. In this paper, we provide a comprehensive survey regarding the state-of-the-art of MAC protocols for PLC systems, including an overview of existing PLC MAC research results and an organization of current PLC MAC protocols in terms of type of protocols, applications, and main research focus. Moreover, we present modern PLC technologies and standards, highlighting their MAC sublayer characteristics and providing a detailed comparative analysis of PLC MAC protocols in the context of current and emerging PLC applications. Finally, we identify future trends within the scope of the MAC sublayer for PLC systems with a view to stimulating additional research efforts on PLC MAC design.

Influence of motor cable on common-mode currents in an inverter-fed motor drive system

Induction motor drive systems fed by cables are widely used in industrial applications. However, high-frequency switching of power devices will cause common-mode (CM) voltages during operation, leading to serious CM currents in the motor drive systems. CM currents through the cables and motors in the drive systems can cause electromagnetic interference (EMI) with the surrounding electronic equipment and shorten the life of induction motors. Therefore, it is necessary to analyze the CM currents in motor drive systems. In this paper, high-frequency models of unshielded and shielded power cables are formulated. The frequency-dependent effects and mutual inductances of the cables are taken into account. The power cable parameters are extracted by the finite element method and validated by measurements. High-frequency models of induction motors and inverters are introduced from existing works. The CM currents at the motor and inverter terminals are obtained, and the influence of the cable length and cable type on the CM currents is analyzed. There is a good agreement between the experimental results and the CM currents predicted by the proposed models.