Novel Earth Fault Protection Algorithm Based on MV Cable Screen Zero Sequence Current Filter

This paper presents novel zero sequence current filter and earth fault protection relay, which utilize cable screens earthing current in protection algorithm. Different problems connected with state of the art of zero sequence current filters and protection relays are presented and compared with the proposed solution. The presented concept is verified in PowerFactory simulation software, experiment concerning modeling the earth fault current flow in medium voltage (MV) cable supplied from the low voltage (LV) network and measurements in the MV network in the Polish distribution system. The proposed solution is characterized by higher sensitivity and reduced number of erroneous trips. The presented solution is suitable for any MV cable lines. Biggest advantages are observed in power output lines from renewable energy sources, which are often operated under no-load conditions.

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Analysis of Effective Three-Level Neutral Point Clamped Converter System for the Bipolar LVDC Distribution

Electronics ◽

10.3390/electronics8060691 ◽

2019 ◽

Vol 8 (6) ◽

pp. 691 ◽

Cited By ~ 8

Author(s):

Ju-Yong Kim ◽

Ho-Sung Kim ◽

Ju-Won Baek ◽

Dong-Keun Jeong

Keyword(s):

Distribution System ◽

Low Voltage ◽

Balance Control ◽

Short Circuit ◽

Renewable Energy Sources ◽

Neutral Point ◽

Extreme Load ◽

Zero Sequence ◽

Zero Sequence Voltage ◽

Short Circuit Condition

Low-voltage direct current (LVDC) distribution has attracted attention due to increased DC loads, the popularization of electric vehicles, energy storage systems (ESS), and renewable energy sources such as photovoltaic (PV). This paper studies a ±750 V bipolar DC distribution system and applies a 3-level neutral-point clamped (NPC) AC/DC converter for LVDC distribution. However, the 3-level NPC converter is fundamental in the neutral-point (NP) imbalance problem. This paper discusses the NP balance control method using zero-sequence voltage among various solutions to solve NP imbalance. However, since the zero-sequence voltage for NP balance control is limited, the NP voltage cannot be controlled to be balanced when extreme load differences occur. To maintain microgrid stability with bipolar LVDC distribution, it is necessary to control the NP voltage balance, even in an imbalance of extreme load. In addition, due to the bipolar LVDC distribution, the pole where a short-circuit condition occurs limits the short current until the circuit breaker operates, and a pole without a short-circuit condition must supply a stable voltage. Since the conventional 3-level NPC AC/DC converter alone cannot satisfy both functions, an additional DC/DC converter is proposed, analyzed, and verified. This paper is about a 3-level NPC AC/DC converter system for LVDC distribution. It can be used for the imbalance and short-circuit condition in bipolar LVDC distribution through the prototype of the 300 kW 3-level NPC AC/DC converter system and experimented and verified in various conditions.

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Dynamic stability of the functioning of current earth fault directional protection in networks with isolated neutral

Vestnik IGEU ◽

10.17588/2072-2672.2019.6.030-041 ◽

2019 ◽

pp. 30-41

Author(s):

Yu.D. Kutumov ◽

V.V. Tyutikov ◽

T.Yu. Shadrikova ◽

V.A. Shuin

Keyword(s):

Dynamic Stability ◽

Electrical Networks ◽

Medium Voltage ◽

Earth Fault ◽

Fault Protection ◽

Zero Sequence ◽

Protection Devices ◽

High Dynamic ◽

Isolated Neutral ◽

Zero Sequence Voltage

In distribution 6–10 kV networks with an insulated neutral for earth fault protection, zero sequence current directional protection devices are commonly used. According to the operation data, the main disadvantage of such kind of protection is the possibility of their functioning failures in transient conditions with the most dangerous for network intermittent arc earth faults. It is known that most earth faults in 6–10 kV networks, primarily in the initial stage of insulation damage, have an intermittent arc. Operation failures of zero sequence current directional protection in case of arc faults reduce the operational reliability of the protected network and, as a result, the reliability of power supply to consumers. Nowadays, new developments of electrical power systems relay protection devices, including earth fault protection of medium voltage distribution electrical networks, are implemented only on a microprocessor base. Therefore, the selection and justification of the implementation principles of zero sequence current directional protection which can provide high dynamic stability of functioning is a relevant objective. When analyzing the dynamic stability of the functioning of zero sequence directional current protection, regarding the complexity of transients during intermittent arc earth faults in medium voltage electrical networks with an isolated neutral, the simulation in Matlab using SimPowerSystem and Simulink was carried out. This study focuses on transient currents and voltages as the main factor influencing dynamic stability of the functioning of zero sequence current directional protection. The impact of other factors, for example, the inaccuracies of the primary zero sequence current and voltage transducers, the scheme of formation of compared quantities, etc. was not taken into account in simulation models. The study has allowed determining the causes of possible functioning failures of digital current earth fault directional protection in dynamic operation modes. It has been shown that the usage of orthogonal components of fundamental frequency of zero sequence voltage and current in current directional protection devices eliminates the failure of their operation with any kind of arc earth faults. To ensure high dynamic stability of operation under the influence of transients during arc intermittent earth faults, current directional protection for this type of damage should be performed on the basis of monitoring the phase relationships of the fundamental frequency components of 50 Hz of zero sequence voltage and current, but not their full values.

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Multiobjective Approach for Medium- and Low-Voltage Planning of Power Distribution Systems Considering Renewable Energy and Robustness

Energies ◽

10.3390/en13102517 ◽

2020 ◽

Vol 13 (10) ◽

pp. 2517

Author(s):

Diogo Rupolo ◽

Benvindo Pereira Junior ◽

Javier Contreras ◽

José Mantovani

Keyword(s):

Renewable Energy ◽

Power Distribution ◽

Distribution System ◽

Distribution Systems ◽

Low Voltage ◽

Renewable Energy Sources ◽

Optimization Techniques ◽

Neighborhood Search ◽

Medium Voltage ◽

Multiobjective Approach

In this paper, a multiobjective approach to carry out the planning of medium-voltage (MV) and low-voltage (LV) distribution systems, considering renewable energy sources (RES) and robustness, is proposed. Due to the uncertainties associated with RES and demand, the proposed planning methodology takes into account a robust planning index (RPI). This RPI allows us to evaluate the robustness estimation associated with each planning solution. The objective function in the mathematical model considers the costs of investment and operation and the robustness of the planning proposals. Due to the computational complexity of this problem, which is difficult to solve by means of classical optimization techniques, MV/LV planning is solved by a decomposition search and a general variable neighborhood search (GVNS) algorithm. To demonstrate the efficiency and robustness of this methodology, tests are performed in an integrated distribution system with 50 MV nodes and 410 LV nodes. Our numerical results show that the proposed methodology makes it possible to minimize costs and improve robustness levels in distribution system planning.

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Machine Learning and GIS Approach for Electrical Load Assessment to Increase Distribution Networks Resilience

Energies ◽

10.3390/en14144133 ◽

2021 ◽

Vol 14 (14) ◽

pp. 4133

Author(s):

Alessandro Bosisio ◽

Matteo Moncecchi ◽

Andrea Morotti ◽

Marco Merlo

Keyword(s):

Machine Learning ◽

Distribution System ◽

Low Voltage ◽

Regression Tree ◽

Distribution Networks ◽

Machine Learning Algorithms ◽

Extreme Weather Events ◽

Medium Voltage ◽

Weather Events ◽

Building Area

Currently, distribution system operators (DSOs) are asked to operate distribution grids, managing the rise of the distributed generators (DGs), the rise of the load correlated to heat pump and e-mobility, etc. Nevertheless, they are asked to minimize investments in new sensors and telecommunication links and, consequently, several nodes of the grid are still not monitored and tele-controlled. At the same time, DSOs are asked to improve the network’s resilience, looking for a reduction in the frequency and impact of power outages caused by extreme weather events. The paper presents a machine learning GIS-based approach to estimate a secondary substation’s load profiles, even in those cases where monitoring sensors are not deployed. For this purpose, a large amount of data from different sources has been collected and integrated to describe secondary substation load profiles adequately. Based on real measurements of some secondary substations (medium-voltage to low-voltage interface) given by Unareti, the DSO of Milan, and georeferenced data gathered from open-source databases, unknown secondary substations load profiles are estimated. Three types of machine learning algorithms, regression tree, boosting, and random forest, as well as geographic information system (GIS) information, such as secondary substation locations, building area, types of occupants, etc., are considered to find the most effective approach.

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Arcing Fault Protection for Low-Voltage Power Distribution System - Nature of the Problem

Transactions of the American Institute of Electrical Engineers Part III Power Apparatus and Systems ◽

10.1109/aieepas.1960.4500717 ◽

1960 ◽

Vol 79 (3) ◽

pp. 160-165 ◽

Cited By ~ 69

Author(s):

R. H. Kaufmann ◽

J. C. Page

Keyword(s):

Power Distribution ◽

Distribution System ◽

Low Voltage ◽

Power Distribution System ◽

Fault Protection ◽

Arcing Fault

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The influence of the network asymmetry on the settings and sensitivity of an earth fault protection using higher harmonics

E3S Web of Conferences ◽

10.1051/e3sconf/20198402008 ◽

2019 ◽

Vol 84 ◽

pp. 02008

Author(s):

Lubomir Marciniak ◽

Mateusz Piątek

Keyword(s):

Reactive Power ◽

Higher Harmonics ◽

Medium Voltage ◽

Earth Fault ◽

Power Setting ◽

Zero Sequence ◽

The Asymmetry ◽

Supply Voltages ◽

Zero Sequence Voltage

Detection of high resistance earth faults in medium voltage networks is an important problem due to ineffectiveness of traditional earth fault protections. Such short circuits can be detected by the criterion of a reactive power of higher harmonics for zero sequence current and voltage. The main problem is determination of the power setting value in the protection, which depends on the asymmetry of phase-to-earth capacitances and higher harmonics in supply voltages, which are generated by non-linear loads. The intensive tests of the asymmetry of the zero sequence currents and voltages for harmonics and their reactive power have been carried out in 15 kV compensated network as a function of all relevant parameters, i.e.: maximum capacitance deviation of the network and protected line, percentage content of harmonics in supply voltages, capacitive current of the network and the line. It has been shown that third harmonics of the zero sequence voltage and current are the best suited for practical use, since the asymmetry reactive power of these components is the smallest among the considered harmonics and the protection sensitivity will be the highest.

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Maintenance of Three-phase Load Voltage during Single Phase Auto Reclosing in Medium Voltage Radial Distribution Lines

International Journal of Emerging Electric Power Systems ◽

10.2202/1553-779x.2703 ◽

2011 ◽

Vol 12 (4) ◽

Cited By ~ 1

Author(s):

Kartik Prasad Basu ◽

Moley Kutty George

Keyword(s):

Radial Distribution ◽

Distribution System ◽

Single Phase ◽

Dead Time ◽

Low Voltage ◽

Radial Distribution System ◽

Load Voltage ◽

Medium Voltage ◽

Distribution Lines ◽

Three Phase

Most faults in medium voltage (MV) distribution lines are temporary line to ground (LG) faults. Three-phase auto reclosing (TPAR) is commonly used to remove this fault with temporary disconnection of all the phases. Multi-shot single-phase auto reclosing (SPAR) may also be used to remove the LG fault. But it produces highly unbalanced and low voltage across the load during the reclosure dead time. It is proposed to connect a zigzag winding grounding transformer at the load bus to maintain the 3-phase load voltage when one phase opens during the SPAR. With low value of grounding resistance the 3-phase voltage during the SPAR dead time becomes approximately balanced. Directional over current relays may be used for the protection. Analysis of a MV radial distribution system having a zigzag transformer connected to the remotest load bus is presented with the computation of voltages during the dead time of SPAR.

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