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The current and voltage in High Voltage DC (HVDC) line is not pure DC but contain superimposed ripple components. The current ripple in core of HVDC cable magnetically induces a voltage in the sheath, whereas the voltage ripple causes the flow of charging current from core to sheath. The knowledge of sheath voltage is necessary to ensure compliance...
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... Similarly, the cable sheath LIWL is 60kV. The sheath of cable sections can be grounded in multiple ways to reduce any stress on outer jacket of insulator under transient conditions [34]. Here, analysis is done by considering multiterminal grounding as shown in Fig. 7(b). ...
Medium voltage direct current (MVDC) transmission system are growing due to their assistive quality in conventional grid and compatibility with renewable power network. MVDC distribution links with “Mixed” overhead (OH) & underground (UG) sections could be devised based on urban planning. UG Cables or substations are indirectly exposed to lightning strikes due to adjacent tower sections. In case of MVDC converter or cable, present researchers do not specify lightning voltage impulse level for related system voltage. Therefore, preluding electromagnetic (EM) transient investigation are required to determine the maximum lightning overvoltages for system peripherals i.e. cable & Modular Multilevel Converter (MMC) substation. This research focuses on analyzing lightning performance of OH transmission towers-cable junction & tower-substation link in case of a shielding failure (SF) and back flashover (BF) for a ±35kV short-length mixed MMC-MVDC transmission scheme. This article provides broad-band modeling method for MMC substation for lightning investigation. In addition, based on a detailed time-domain parametric evaluation in
PSCAD/EMTDC
program, lightning impulse voltage across the transmission line’s pole insulator and embedded cable section are estimated along with numerical validation relying on travelling wave theory. Effect of project parameters such as tower grounding resistance, riser section surge impedance (which connects cable & OH line) and cable length on lightning overvoltage impacting the cable and connected tower section has been demonstrated.
... The literature [5] investigates the calculation of induced voltages in multiple circuits of cables and proposes a new method for the calculation of induced voltages in metal shields of three-circuit, single-core power cables. The literature [6] analyzes the sheath voltage and current of HVDC cables, considering different cable lengths and sheath grounding schemes. The literature [7,8] proposes a single-core cable sheath overvoltage analysis method and suppression measures considering harmonics and inrush currents. ...
The metal shield and metal armor layers of single-core cables on high-speed railroad power penetration lines are usually grounded by common equipment protectors. This grounding method brings a continuous circulating current between the metal shield and metal armor layer compared to the subequipment protection grounding. In order to quantitatively study the circulating current condition of the through line and its influence on the reliability of the railroad power through line, the induced electric potential and circulating current generation mechanism of the single-core cable of the through line and its influencing factors were firstly analyzed in depth. Then, based on the cross-sectional structure of the single-core cable and the location of the traction network and cable in the roadbed section, a traction power supply model was established and simulated for the interlayer-induced potentials and circulating currents due to the two grounding protection methods under no load, single train operation, and heavy load four-train operation of the line. Finally, three actual sections of the Shanghai–Kunming and Nan–Kunming high-speed railroads in China were selected to collect and analyze the loop flow data with no load and with vehicles passing through, and finally the loop flow law of single-core cable for railroad electric through traffic was derived. The analysis shows that when the metal sheath of a single-core cable is grounded by ordinary equipment, the circulating current generated does not exceed 1% of the core current, which meets the relevant safety standards, but the induced voltage in the case of large loads will exceed 50 V safety voltage.
... With EHV transmission projects widely used, the number and voltage level of DC transmission lines are growing, and the DC magnetic bias problem caused by AC/DC hybrid transmission is becoming increasingly serious [1][2][3][4]. Transformer DC magnetic bias monitoring is usually carried out by measuring grounding current [5][6][7][8][9], which requires electromagnetic coupling and has weak safety. As a mechanical wave detection method, acoustic signal detection can realize the mechanical state detection of equipment without electromagnetic coupling. ...
The acoustic signal in the operation of a power transformer contains a lot of transformer operation state information, which is of great significance to the detection of DC bias state. In this paper, three typical parameters used for DC bias state detection are selected by comparing the acoustic variation of a 500 kV Jingting transformer substation No. 2 transformer with that of the core model built in the laboratory; then, acoustic samples of the 162 EHV normal state transformers are collected, and the distribution regularity of three typical parameters in normal state is given. Finally, according to the distribution regularity, clear warning threshold of typical parameters are given, and the DC bias cases from the 500 kV Jingting transformer substation are used to verify the effectiveness of the threshold.
... This has established a 10 kV cable operating state evaluation model based on the test results obtained by conducting macroscopic and microscopic tests on the test cable, and has fully considered the cable operating life, operating environment and other ancillary factors, and evaluated the new and old cables [9,10]. It applies D-S evidence theory to the state assessment of cables [11], uses multiple monitoring indicators, and proposes a comprehensive evaluation model for cable insulation that integrates evidence theory and fuzzy theory. It also established a comprehensive indicator system for cables [12], and obtained the weight values of various indicators based on the improved analytic hierarchy process [13]. ...
... According to Formula (11), the probability matrix of each evaluation cable belonging to different states is: Figure 7 and the calculation results of the probability matrix, it can be seen that S 1B , S 5A , and S 5B are in the normal state, and S 1C and S 5C are in the normal state with a probability of 97.7% and 85.8%, respectively. S 2A is in the interval of the attention state, and S 2C belongs to the attention state with a probability of 97.5%. ...
In view of the problem that the weight value given by the previous state evaluation method is fixed and single and cannot analyze the influence of the weight vector deviation on the evaluation result, a method based on the weight space Markov chain and Monte Carlo method (Markov chains Monte Carlo, MCMC) is proposed. The sampling method is used for evaluating the condition of high-voltage cables. The weight vector set obtained by MCMC sampling and the comprehensive degradation degree of the high-voltage cable sample are weighted and summed then compared in pairs to obtain the comprehensive degradation degree result. The status probability value and overall priority ranking probability of the object to be evaluated are obtained based on probability statistics, and the order of maintenance is determined according to the status probability value and the ranking result. It is realized that the cable line that needs to be identified in the follow-up defect is clarified according to the evaluation result. This is helpful for operational and maintenance personnel to more accurately implement the maintenance plan for the cable and improve the operational and maintenance efficiency.
... These large-scale mixed source models were used for the analysis of complicated failures such as a cascading collapse problem caused by fast-acting distributed energy resources [105]. Of course, PSCAD/EMTDC is widely used beyond GMT integration, especially for dynamic modeling of AC or DC components in electrical engineering [106]. ...
This paper gives a comprehensive insight into gas microturbine (GMT) as a part of microgeneration systems. The gas microturbine is a highly effective source that can operate on various types of fuel, including a low-percentage methane fuel such as biogas or landfill gas. The microturbine is widely used in an industrial, rural and commercial application that can benefit from combined heat and power production as a prime or backup source. A microgrid is a modern way to support decentralised power production. It can operate in off-grid mode or as a tool to stabilise the grid and help with peak-shaving as well as to supply remote areas with generated power. The combination of gas microturbine as a prime mover for the microgrid is a smart solution that can quickly react and implement renewable and new technologies. The GMT can be coupled with solar photovoltaics, wind turbine, fuel cells or combustion engines. Use of these technologies can create a sophisticated, stable and highly effective power system. Based on the findings, the combination of microgrid and gas microturbine is very viable and favourable in terms of efficiency, controllability, stability and variety of applications. This paper provides a survey in the field of gas microturbine, its operation, industrial applications, software for microturbine integration, microgrid operation, and coupling the microgrids with gas microturbines, as well as possible challenges and perspectives for this area of combined power generation.
... These currents produce additional power losses in the cables and hence decrease the current-carrying capacity. Such power losses, due to the induced voltages, may occur even in HVDC power cable systems, as underlined in [16]. Therefore, it is important to evaluate sheath circulating currents with relatively high accuracy [17], taking into account different geometries of the cables [18], sheath resistance, phase rotation and cable armouring [19] as well as varied load conditions [20]. ...
Load currents and short-circuit currents in high-voltage power cable lines are sources of the induced voltages in the power cables’ concentric metallic sheaths. When power cables operate with single-point bonding, which is the simplest bonding arrangement, these induced voltages may introduce an electric shock hazard or may lead to damage of the cables’ outer non-metallic sheaths at the unearthed end of the power cable line. To avoid these aforementioned hazards, both-ends bonding of metallic sheaths is implemented but, unfortunately, it leads to increased power losses in the power cable line, due to the currents circulating through the sheaths. A remedy for the circulating currents is cross bonding—the most advanced bonding solution. Each solution has advantages and disadvantages. In practice, the decision referred to its selection should be preceded by a wide analysis. This paper presents a case study of the induced sheath voltages in a specific 110 kV power cable line. This power cable line is a specific one, due to the relatively low level of transferred power, much lower than the one resulting from the current-carrying capacity of the cables. In such a line, the induced voltages in normal operating conditions are on a very low level. Thus, no electric shock hazard exists and for this reason, the simplest arrangement—single-point bonding—was initially recommended at the project stage. However, a more advanced computer-based investigation has shown that in the case of the short-circuit conditions, induced voltages for this arrangement are at an unacceptably high level and risk of the outer non-metallic sheaths damage occurs. Moreover, the induced voltages during short circuits are unacceptable in some sections of the cable line even for both-ends bonding and cross bonding. The computer simulations enable to propose a simple practical solution for limiting these voltages. Recommended configurations of this power cable line—from the point of view of the induced sheath voltages and power losses—are indicated.
Accurate fault location with a short data window is crucial and challenging for cable faults in the modular multilevel converter high voltage direct current (MMC-HVDC) system. Aiming at this issue, this paper proposes a frequency-domain fault location method, which accurately and comprehensively addresses the frequency dependency and unbalance of the parameter matrices without any approximation while considering the distributed parameters. Firstly, the frequency-domain decoupling is analyzed for DC cables with the metallic sheath and armor grounded at two terminals. Secondly, a method is proposed to calculate the voltage distribution along the cable using voltages and currents at one side of the cable based on the numerical Laplace transform (NLT). Subsequently, the cable parameter calculation method suitable for the NLT is presented, and a multi-round iterative algorithm for voltage distribution calculation is proposed. Ultimately, the complete fault location scheme is presented. Extensive simulations validate that the proposed method can achieve fault location with minor errors using a 20 kHz sampling rate and a 4 ms data window. Besides, high accuracy is maintained even under the influence of large fault impedance and noise. Compared to existing methods, the approach exhibits lower fault location error while requiring less computational complexity.
In this paper, 22 equations for high voltage cable sheaths are simulated in one model. The model outputs are represented by cable sheath voltages, circulating currents, losses and factors, eddy currents, losses, and factors in both tides laying states (trefoil and flat) when grounding the sheaths from a single point, two points, or cross-link. These values depend on the cable manufacturing's specific factors. The other factors affecting these values are specific to the laying and operation: the load current, the length of the cable to be laid out, the spacing between the cables, and the power frequency. This research aims to reduce or eliminate the losses of the cable sheath. These two types of currents cause losses that may sometimes equal the losses of the conductor of the cable carrying the load current. Which reduces the capacity of the cable and reduces the heat dissipation of the cable into the soil and damages it. Electricians are at risk of electrocution due to the high voltages of the sheaths when there is no current in the sheaths. Therefore, these currents and voltages must be eliminated by making a new model that studies the effect of all these factors on them.
