Closed-form expressions for ground return impedances of overhead lines and underground cables

2012 ◽  
Vol 38 (1) ◽  
pp. 20-26 ◽  
Author(s):  
Antonio C.S. Lima ◽  
Carlos Portela
Keyword(s):  
Closed Form ◽  
Underground Cables ◽  
Overhead Lines

scholarly journals Photovoltaic Maximum Penetration Limits on Medium Voltage Overhead and Underground Cable Distribution Feeders: A Comparative Study

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3843
Author(s):  
Sultan Sh. Alanzi ◽  
Rashad M. Kamel
Keyword(s):  
Power System ◽  
Power Factor ◽  
Distribution System ◽  
Power Flow ◽  
Underground Cables ◽  
Overhead Lines ◽  
Medium Voltage ◽  
Load Power ◽  
Bus Voltage ◽  
Pv Penetration

This paper investigates the maximum photovoltaic (PV) penetration limits on both overhead lines and underground cables medium voltage radial distribution system. The maximum PV penetration limit is estimated considering both bus voltage limit (1.05 p.u.) and feeder current ampacity (1 p.u.). All factors affect the max PV penetration limit are investigated in detail. Substation voltage, load percentage, load power factor, and power system frequency (50 Hz or 60 Hz) are analyzed. The maximum PV penetration limit associated with overhead lines is usually higher than the value associated with the underground cables for high substation voltage (substation voltage = 1.05 and 1.04 p.u.). The maximum PV penetration limit decreases dramatically with low load percentage for both feeder types but still the overhead lines accept PV plant higher than the underground cables. Conversely, the maximum PV penetration increases with load power factor decreasing and the overhead lines capability for hosting PV plant remains higher than the capability of the underground cables. This paper proved that the capability of the 60-Hz power system for hosting the PV plant is higher than the capability of 50 Hz power system. MATLAB software has been employed to obtain all results in this paper. The Newton-Raphson iterative method was the used method to solve the power flow of the investigated systems.

scholarly journals An Effective Method to Calculate Frequency Response of Distribution Networks for PLC Applications

Electronics ◽  
2019 ◽  
Vol 8 (6) ◽  
pp. 649 ◽  
Author(s):  
Hongshan Zhao ◽  
Weitao Zhang ◽  
Yan Wang
Keyword(s):  
Frequency Response ◽  
Distribution Networks ◽  
Dynamic Changes ◽  
Binary Function ◽  
Underground Cables ◽  
Overhead Lines ◽  
Medium Voltage ◽  
Response Characteristics ◽  
Network Topologies ◽  
Propagation Matrix

Modelling and estimating power-line communication (PLC) channels are complicated issues due to the complex network topologies, various junctions, and changeable loads. This paper focuses on the frequency response characteristics (FRCs) of medium-voltage (MV) PLC networks with special consideration of two scenarios that are often neglected but generally exist. In the first scenario, the MV distribution network is of the ring topology. In the second scenario, the MV overhead lines and underground cables join at junctions, and the shields of underground cables are grounded with nonzero grounding impedances at the junctions. These conditions lead to the failure of currently popular methods to different degrees. For this reason, we developed an effective method to calculate the FRCs of distribution networks for PLC applications. With this method, the frequency responses of nodes are simply expressed as the binary function of the overall tube propagation matrix and overall node scattering matrix, which is convenient for calculations and analyses. The proposed method was validated by the agreement between the calculated and measured FRCs. The results of two test examples showed that the proposed method performed better in comparison with the traditional approximate method when nonideal grounding conditions were taken into account. The proposed method is also independent of the network topology, so it can adapt to the dynamic changes of the network structure.

scholarly journals Closed-Form Expressions for the Analysis of Wave Propagation in Overhead Distribution Lines

Energies ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 4519
Author(s):  
Theofilos A. Papadopoulos ◽  
Andreas I. Chrysochos ◽  
Christos K. Traianos ◽  
Grigoris Papagiannis
Keyword(s):  
Wave Propagation ◽  
Closed Form ◽  
System Analysis ◽  
Complex Form ◽  
Displacement Current ◽  
Decomposition Algorithms ◽  
Overhead Lines ◽  
Power System Analysis ◽  
Electromagnetic Transient ◽  
Time Domain Electromagnetic

The calculation of the influence of the imperfect earth on overhead conductors is an important issue in power system analysis. Rigorous solutions contain infinite integrals; thus, due to their complex form, different simplified closed-form expressions have been proposed in the literature. This paper presents a detailed analysis of the effect of different closed-form expressions on the investigation of the wave propagation of distribution overhead lines (OHLs). A sensitivity analysis is applied to determine the most important properties influencing the calculation of the OHL parameters. The accuracy of several closed-form earth impedance models is evaluated as well as the influence of the displacement current and imperfect earth on the shunt admittance, which are further employed in the calculation of the propagation characteristics of OHLs. The frequency-dependence of the soil electrical properties, as well as the application of different modal decomposition algorithms, are also investigated. Finally, results on the basis of frequency-domain signal scans and time-domain electromagnetic transient responses are also discussed.

Closed-Form Expression for Ground Return Admittance in Underground Cables

2019 ◽  
Vol 34 (6) ◽  
pp. 2251-2253 ◽  
Author(s):  
Joao P. L. Salvador ◽  
Antonio P. C. Magalhaes ◽  
Antonio C. S. Lima ◽  
Maria Teresa Correia de Barros
Keyword(s):  
Closed Form ◽  
Closed Form Expression ◽  
Form Expression ◽  
Underground Cables

scholarly journals Reliability cost/worth assessment of distribution network formed by underground cables and overhead lines. Case study of Latvia

Energetika ◽  
2015 ◽  
Vol 61 (1) ◽  
Author(s):  
Aleksandrs Ļvovs ◽  
Ilze Priedite
Keyword(s):  
Power Supply ◽  
Distribution Network ◽  
Distribution Networks ◽  
Actual Distribution ◽  
Underground Cables ◽  
Overhead Lines ◽  
Capital Costs ◽  
Reliability Level ◽  
Fault Statistics

The increasing number of severe weather occurrences that influence the number of large scale outages, especially in rural distribution networks, makes the question on the need of increasing reliability level of power supply of the distribution network even more actual. Distribution system operators and national regulators shall not only find a reliable but also a cost-effective solution for further distribution network development: the optimal reliability level of power supply. One of the reliability improvement solutions that allows effectively dealing with the reduction of the number of outages in rural distribution networks is the cablification of network. Construction costs of the aforementioned solution are quite high in comparison to other network line types, and due to that, the implementation of the solution always raises discussions on cost-effectiveness. The paper presents approaches for the cost/worth assessment of power line lifetime costs in the distribution network and for the assessment of customer costs of reliability that takes into account time-varying loads and outage costs (previously developed by authors of this paper [6, 7]) as well as for the assessment of traders’ losses due to electrical energy not supplied. The case study included in the paper is performed for Latvian conditions and takes into account information on the real customer costs of reliability of Latvian customers (information from the study of the Institute of Physical Energetics), fault statistics of Latvian underground cables and overhead lines, information with a high level of details on the capital costs, operational and fault elimination costs of distribution lines in Latvia.

scholarly journals Accuracy and Reliability of Switching Transients Measurement with Open-Air Capacitive Sensors

Energies ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1405
Author(s):  
Barakou ◽  
Steennis ◽  
Wouters
Keyword(s):  
Electromagnetic Compatibility ◽  
Cross Coupling ◽  
Interference Rejection ◽  
Underground Cables ◽  
Overhead Lines ◽  
Capacitive Divider ◽  
Measurement Methodology ◽  
Extra High Voltage ◽  
Transient Voltages ◽  
Line Coupling

Contactless capacitive (open-air) sensors are applied to monitor overvoltages near overhead line terminations at a substation or at the transition from underground cables to overhead lines. It is shown that these sensors, applied in a differentiating/integrating measuring concept, can result in excellent characteristics in terms of electromagnetic compatibility. The inherent cross-coupling from open-air sensors to other phases is dealt with. The paper describes a method to calibrate the sensor to line coupling matrix based on assumed 50 Hz symmetric phase voltages and in particular focuses on uncertainty analysis of assumptions made. Network simulation shows that predicted maximum overvoltages agree within typically 7% compared to reconstructed values from measurement, also with significant cross-coupling. Transient voltages from energization of an (extra-)high voltage connection can cause large and steep rising ground currents near the line terminations. Comparison with results obtained by a capacitive divider confirms the intrinsic capability in interference rejection by the differentiating/integrating measurement methodology.

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