Permanent faults in medium-voltage cable joints significantly impact the reliability of distribution networks.Radial breakdowns caused by water ingress often lead to several self-extinguishing arc discharges—referred...Permanent faults in medium-voltage cable joints significantly impact the reliability of distribution networks.Radial breakdowns caused by water ingress often lead to several self-extinguishing arc discharges—referred to as incipient faults—before developing into permanent faults.Effective monitoring of incipient faults can help reduce outage costs associated with permanent faults.However,the specific fault scenarios of incipient faults remain insufficiently understood.To address this gap,this study designed a simulation experiment replicating incipient fault conditions in medium-voltage cable joints under humid environments,based on actual operating scenarios.The experiment compared the insulation strength required to trigger incipient faults and examined both non-electrical fault characteristics,such as insulation damage and arc flame intensity,and electrical characteristics,such as fault current and impedance.Experimental observations show that,in cable joints,gaps without accumulated water retain sufficient insulation strength to prevent breakdown.However,the infiltration of accumulated water shortens the effective insulation path,thereby lowering the breakdown threshold.The peak current of an incipient fault can range from hundreds to thousands of amperes,with a duration of approximately 1/8 to 1/4 of a power–frequency cycle.During incipient faults,arc burning on the pore wall leaves conductive traces,which progressively reduce the insulation strength of the surrounding environment.As these traces accumulate over multiple events,the likelihood of breakdown increases,ultimately resulting in a permanent fault.Permanent faults are characterized by intense,sustained arc discharges that persist over a macroscopic time scale and exhibit flat-shoulder waveforms within individual cycles,with discharge intensity increasing progressively over time.展开更多
Power line communication(PLC)provides intelligent electrical functions such as power quality measurement,fault surveys,and remote control of electrical network.Most of research works have been done in low voltage(LV)s...Power line communication(PLC)provides intelligent electrical functions such as power quality measurement,fault surveys,and remote control of electrical network.Most of research works have been done in low voltage(LV)scenario due to the fast development of in-home PLC.The aim of this paper is to evaluate the link-level performance of a medium voltage(MV)MIMO-OFDM communication system based on transmission link under underground power line channel.The MIMO channel is modeled as a modified multipath model in the presence of impulsive noise and background noise.We first perform a measurement on the practical MV MIMO channel parameters for a section of buried cable of 1 km long in Ganzhou city,Jiangxi province,China.Based on the measured channel,we design the frame structure based on an IEEE standard for broadband over power line networks[1]to support MV MIMO-OFDM transmission.According to designed frame structure,we design an encoder and a decoder for a dual binary tail-biting turbo code and optimize some key decoder parameters for low bit error rate performance.Finally,the link-level performance for both spatial multiplexing and spatial diversity are evaluated.Numeral results show that MV MIMO-OFDM is a promising approach to provide both high data rate and link reliability for PLC.展开更多
基金supported by National Natural Science Foundation of China(No.52077133).
文摘Permanent faults in medium-voltage cable joints significantly impact the reliability of distribution networks.Radial breakdowns caused by water ingress often lead to several self-extinguishing arc discharges—referred to as incipient faults—before developing into permanent faults.Effective monitoring of incipient faults can help reduce outage costs associated with permanent faults.However,the specific fault scenarios of incipient faults remain insufficiently understood.To address this gap,this study designed a simulation experiment replicating incipient fault conditions in medium-voltage cable joints under humid environments,based on actual operating scenarios.The experiment compared the insulation strength required to trigger incipient faults and examined both non-electrical fault characteristics,such as insulation damage and arc flame intensity,and electrical characteristics,such as fault current and impedance.Experimental observations show that,in cable joints,gaps without accumulated water retain sufficient insulation strength to prevent breakdown.However,the infiltration of accumulated water shortens the effective insulation path,thereby lowering the breakdown threshold.The peak current of an incipient fault can range from hundreds to thousands of amperes,with a duration of approximately 1/8 to 1/4 of a power–frequency cycle.During incipient faults,arc burning on the pore wall leaves conductive traces,which progressively reduce the insulation strength of the surrounding environment.As these traces accumulate over multiple events,the likelihood of breakdown increases,ultimately resulting in a permanent fault.Permanent faults are characterized by intense,sustained arc discharges that persist over a macroscopic time scale and exhibit flat-shoulder waveforms within individual cycles,with discharge intensity increasing progressively over time.
文摘Power line communication(PLC)provides intelligent electrical functions such as power quality measurement,fault surveys,and remote control of electrical network.Most of research works have been done in low voltage(LV)scenario due to the fast development of in-home PLC.The aim of this paper is to evaluate the link-level performance of a medium voltage(MV)MIMO-OFDM communication system based on transmission link under underground power line channel.The MIMO channel is modeled as a modified multipath model in the presence of impulsive noise and background noise.We first perform a measurement on the practical MV MIMO channel parameters for a section of buried cable of 1 km long in Ganzhou city,Jiangxi province,China.Based on the measured channel,we design the frame structure based on an IEEE standard for broadband over power line networks[1]to support MV MIMO-OFDM transmission.According to designed frame structure,we design an encoder and a decoder for a dual binary tail-biting turbo code and optimize some key decoder parameters for low bit error rate performance.Finally,the link-level performance for both spatial multiplexing and spatial diversity are evaluated.Numeral results show that MV MIMO-OFDM is a promising approach to provide both high data rate and link reliability for PLC.
