Energy losses’ reduction in metallic screens of MV cable power lines and busbar bridges composed of single-core cables

Changing the connection type of a medium voltage (MV) cable screen is linked to a decrease in power loss, although it may also lead to the generation of overvoltage in a metallic cable screen, which is hazardous for proper cable line work. In this paper, results of simulation and field researches are presented, showing the range of voltages that occurs in cable screens during single-phase ground fault. There are considered to be three scenarios according to the applied type of cable screen connection. Conducted researches allow the comparison of chosen methods of simulation with an actual outcome. Results obtained during simulation and field studies lead to the conclusion that the range of overvoltage occurred in a cable screen could in fact be dangerous for the cable line's sheath insulation without proper overvoltage protection.

Section: Methodsmentioning

confidence: 99%

Section: Second Scenariomentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Analysis of Overvoltages Appearing in One-Sidedly Ungrounded MV Power Cable Screen

Schött-Szymczak

Walczak

2020

“…Mathematical description of cable lines reduction factor is given by the formula [46]. Mathematical description of reduction factor of cables with ECC wire can be found in [47], the reduction factor of 3 core cables in [48] and in [49] reduction factor of parallel lines.…”

Section: Simulation Testsmentioning

confidence: 99%

Detection and Location of Earth Fault in MV Feeders Using Screen Earthing Current Measurements

Łowczowski

Lorenc

Zawodniak³

et al. 2020

The paper analyzes the utilization of cable screen currents for earth fault identification and location. Attention is paid on cable and mixed feeders—cable and overhead lines. The principle of operation is based on utilization of 3 criterion values: Ratio of cable screen earthing current and zero sequence cable core current—RF110/15, phase shift between cable screen earthing current and zero sequence cable core current—α and cable screen admittance defined as a ratio of cable screen earthing current and zero sequence voltage—Y0cs. Earth fault location is possible thanks to discovered relation between RF110/15 and α, whereas Y0cs allows for reliable detection of earth faults. Detection and identification are very important because it allows to increase the reliability of supply—reduce downtime and number of consumers affected by the fault. The article presents a phase to ground fault current flow for different power system configurations. At the end solution, which improves location capabilities is proposed. The solution is analyzed in PSCAD software and verified by network experiment.

“…This advantage is also appreciated by electricity distributors, for which changing the configuration of cable screen operation is a non-invasive and relatively cheap method to reduce transmission losses. At the time of writing this manuscript, one of the distribution companies started to implement such a method in its MV cable networks [9].…”

Section: Introductionmentioning

confidence: 99%

Impact of Cable Configuration on the Voltage Induced in Cable Screen during Work with One-Sidedly Ungrounded Cable Screen

Schött-Szymczak

Walczak

2021

In the latest research, it has been proven that from the point of view of losses in a cable distribution line, the most advantageous operation is to work with two or one phase of metallic cable screen ungrounded. However, such an operation may cause changes in the network characteristics and thus the occurrence of undesirable phenomena. One of those characteristics is the overvoltages in those cable screens, which can lead to cable line damage. The simulation tests presented in this article are closely related to the unusual method of operation of the MV cable screens and their performance, and they address the question of whether in a given system ground fault overvoltages may be a significant threat to the operation of the cable. The research methods used to verify these risks are related to the simulation of the cable line operating states using the DIgSILENT PowerFactory program (DIgSILENT GmbH, Gomaringen, Germany). Overvoltage simulations were performed, taking into account changes in the network configuration, such as the method of cable screens grounding, the length of cable lines, the cross-section of the conductor and cable screen, or the method of operation of the neutral point. The results for the cable line modeled as a part of the MV network with the variables considered during the tests indicate the possible impact of the one-sidedly cable screen ungrounding on overvoltages in this cable screen. The obtained results at the level of a few kV in one-sidedly ungrounded cable screens show that the change of the configuration of the operation of these cable screens may affect the safety of the network operation.