Insulated underground cables have the potential to reduce power outages, maintenance costs, and transmission losses compared to overhead lines.</span><span style="font-family:""> </span&g...Insulated underground cables have the potential to reduce power outages, maintenance costs, and transmission losses compared to overhead lines.</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">On the other hand, they are exposed to several risks and physical damages, since they are buried in the ground. Though the cables are armoured in order to provide mec</span><span style="font-family:Verdana;">hanical protection and achieve tensile strength, and also to provide effective conductance of earth fault currents.</span></span><span style="font-family:""> </span><span style="font-family:Verdana;">The main purpose of this paper is to introduce insulated underground cables, armouring process, and to analyze the induced currents in metallic parts such as sheath and armour </span><span style="font-family:Verdana;">that causeohmic losses which are categorized mainly in two groups as circulating current and eddy current. This paper presents a review on analytical techniques used to analyze the effect of magnetic fields, andcalculate the losses in </span><span style="font-family:Verdana;">the armour of the cables,</span><span style="font-family:""> </span><span style="font-family:Verdana;">besides providing the strategies and solutions used for armour loss reduction.展开更多
For an accurate estimation of the AC losses of superconducting triaxial cables,in this paper we present a two‐dimensional model capable to provide a global assessment of multi‐layer triaxial cables,validated against...For an accurate estimation of the AC losses of superconducting triaxial cables,in this paper we present a two‐dimensional model capable to provide a global assessment of multi‐layer triaxial cables,validated against the reported AC‐losses measurements on single‐phase cables provided by the Russian Scientific and Research Institute of the Cable Industry(VNIIKP).Four models are presented,the first being a single‐phase cable of 50 tapes and the others being three triaxial cables made of up to 135 coated conductors distributed in up to 9 layers.A systematic study is devised,where the number of layers per phase increases from 1 to 3,with at least 14 tapes distributed across each layer of the first(innermost)phase,15 in the secondary(middle)phase,and 16 in the third(outermost)phase,respectively.Remarkably,our results reveal that the simple strategy of considering an unbalanced distribution for the amplitudes of the applied current,can generally balance the magnetic field between the three phases even for the bilayer and trilayer cables,resulting in negligible magnetic leaks in all situations.Besides,our high‐resolution simulations allow to see for the first time how the transport and magnetization currents distribute across the thickness of all the superconducting tapes,from which we have found that the AC‐losses of the 2nd phase is generally higher than at the other phases at low to moderate transport currents,I_(tr)<0:8I c,being I_(c) the critical current of the corresponding tapes.Nevertheless,depending on whether the I_(c) of the SC tapes at the 3rd phase layers is lower than the one at the 2nd phase,the layers at the third phase can exhibit a considerable increment on the AC losses.This is result of the considered magneto angular anisotropy of the superconducting tapes,which lead to intriguing electromagnetic features that suggest a practical threshold for the applied transport current,being it 0:8I_(c).Likewise,the relative change in the AC‐losses per adding layers,per phase,and as a function of the entire range of applied transport current is disclosed.展开更多
To avoid stray current and maintain the benefit of no phase-split in the DC traction power supply system, an AC traction power supply system was proposed for the urban public transport such as metro and light rail tra...To avoid stray current and maintain the benefit of no phase-split in the DC traction power supply system, an AC traction power supply system was proposed for the urban public transport such as metro and light rail transit. The proposed system consists of a main substation （MSS） and cable traction network （CTN）. The MSS includes a single-phase main traction transformer and a negative-se- quence compensation device, while the CTN includes double-core cables, traction transformers, overhead catenary system, rails, etc. Several key techniques for the proposed system were put forward and discussed, which can be summarized as （1） the power supply principle, equivalent circuit and transmission ability of the CTN, the cable-catenary matching technique, and the selection of catenary voltage level; （2） the segmentation technology and status identification method for traction power supply network, distributed and centralized protection schemes, etc.; （3） a power supply scheme for single-line MSS and a power supply scheme of MSS shared by two or more lines. The proposed industrial frequency single-phase AC traction power supply system shows an excellent technical performance, good economy, and high reliability, hence provides a new alternative for metro and urban rail transit power supply systems.展开更多
文摘Insulated underground cables have the potential to reduce power outages, maintenance costs, and transmission losses compared to overhead lines.</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">On the other hand, they are exposed to several risks and physical damages, since they are buried in the ground. Though the cables are armoured in order to provide mec</span><span style="font-family:Verdana;">hanical protection and achieve tensile strength, and also to provide effective conductance of earth fault currents.</span></span><span style="font-family:""> </span><span style="font-family:Verdana;">The main purpose of this paper is to introduce insulated underground cables, armouring process, and to analyze the induced currents in metallic parts such as sheath and armour </span><span style="font-family:Verdana;">that causeohmic losses which are categorized mainly in two groups as circulating current and eddy current. This paper presents a review on analytical techniques used to analyze the effect of magnetic fields, andcalculate the losses in </span><span style="font-family:Verdana;">the armour of the cables,</span><span style="font-family:""> </span><span style="font-family:Verdana;">besides providing the strategies and solutions used for armour loss reduction.
基金supported by the UK Research and Innovation,Engineering and Physical Sciences Research Council(EPSRC),grant Ref.EP/S025707/1,led by H.S.R.
文摘For an accurate estimation of the AC losses of superconducting triaxial cables,in this paper we present a two‐dimensional model capable to provide a global assessment of multi‐layer triaxial cables,validated against the reported AC‐losses measurements on single‐phase cables provided by the Russian Scientific and Research Institute of the Cable Industry(VNIIKP).Four models are presented,the first being a single‐phase cable of 50 tapes and the others being three triaxial cables made of up to 135 coated conductors distributed in up to 9 layers.A systematic study is devised,where the number of layers per phase increases from 1 to 3,with at least 14 tapes distributed across each layer of the first(innermost)phase,15 in the secondary(middle)phase,and 16 in the third(outermost)phase,respectively.Remarkably,our results reveal that the simple strategy of considering an unbalanced distribution for the amplitudes of the applied current,can generally balance the magnetic field between the three phases even for the bilayer and trilayer cables,resulting in negligible magnetic leaks in all situations.Besides,our high‐resolution simulations allow to see for the first time how the transport and magnetization currents distribute across the thickness of all the superconducting tapes,from which we have found that the AC‐losses of the 2nd phase is generally higher than at the other phases at low to moderate transport currents,I_(tr)<0:8I c,being I_(c) the critical current of the corresponding tapes.Nevertheless,depending on whether the I_(c) of the SC tapes at the 3rd phase layers is lower than the one at the 2nd phase,the layers at the third phase can exhibit a considerable increment on the AC losses.This is result of the considered magneto angular anisotropy of the superconducting tapes,which lead to intriguing electromagnetic features that suggest a practical threshold for the applied transport current,being it 0:8I_(c).Likewise,the relative change in the AC‐losses per adding layers,per phase,and as a function of the entire range of applied transport current is disclosed.
文摘To avoid stray current and maintain the benefit of no phase-split in the DC traction power supply system, an AC traction power supply system was proposed for the urban public transport such as metro and light rail transit. The proposed system consists of a main substation （MSS） and cable traction network （CTN）. The MSS includes a single-phase main traction transformer and a negative-se- quence compensation device, while the CTN includes double-core cables, traction transformers, overhead catenary system, rails, etc. Several key techniques for the proposed system were put forward and discussed, which can be summarized as （1） the power supply principle, equivalent circuit and transmission ability of the CTN, the cable-catenary matching technique, and the selection of catenary voltage level; （2） the segmentation technology and status identification method for traction power supply network, distributed and centralized protection schemes, etc.; （3） a power supply scheme for single-line MSS and a power supply scheme of MSS shared by two or more lines. The proposed industrial frequency single-phase AC traction power supply system shows an excellent technical performance, good economy, and high reliability, hence provides a new alternative for metro and urban rail transit power supply systems.
