Alternative method of determining zero-sequence voltage for fault current passage indicators in overhead medium voltage networks

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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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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Detection of broken conductor with ground contact faults in medium voltage power networks

Facta universitatis - series Electronics and Energetics ◽

10.2298/fuee0603429t ◽

2006 ◽

Vol 19 (3) ◽

pp. 429-438 ◽

Cited By ~ 3

Author(s):

Dumitru Toader ◽

Stefan Haragus ◽

Constantin Blaj

Keyword(s):

Ground Contact ◽

Power Networks ◽

Grounding System ◽

Medium Voltage ◽

Protective System ◽

Zero Sequence ◽

Technical Solutions ◽

Zero Sequence Voltage ◽

Types Of Faults ◽

Good Agreement

A major problem concerning the operation of medium voltage power networks refers to the neutral-point grounding system. Several technical solutions are in use, none of them being completely satisfactory. One criterion to appreciate the efficiency of a grounding system is the ability of the network?s protective system to accurately detect various types of faults such as broken conductor with ground contact faults. This type of fault make a relatively important figure (3 to 10 %) in the total faults statistics for a medium voltage network. In order to detect such faults, the sensed variables are the zero-sequence voltage and the neutral-grounding current. In this paper an analytical and computational analysis is performed to see how various fault and network parameters affect these variables, assuming different grounding systems. Measurements made in two real medium voltage networks show good agreement with the theoretical results.

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Space Vector Pulse Density Modulation Scheme for Zero Sequence Voltage Elimination in Dual Inverter fed Open End Winding Induction Motor Drive

IECON 2020 The 46th Annual Conference of the IEEE Industrial Electronics Society ◽

10.1109/iecon43393.2020.9254706 ◽

2020 ◽

Author(s):

Menon A Monisha ◽

Biji Jacob

Keyword(s):

Induction Motor ◽

Motor Drive ◽

Modulation Scheme ◽

Induction Motor Drive ◽

Space Vector ◽

Pulse Density ◽

Zero Sequence ◽

Density Modulation ◽

Zero Sequence Voltage ◽

Open End Winding

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Zero-Sequence Voltage-based Method for Determination and Classification of Unloaded Overhead Line Operating Conditions at the Moment of Energization

Electric Power Components and Systems ◽

10.1080/15325008.2018.1433252 ◽

2018 ◽

Vol 46 (2) ◽

pp. 162-176 ◽

Cited By ~ 1

Author(s):

Sasa Mujovic ◽

Snezana Vujosevic ◽

Luka Vujosevic

Keyword(s):

Operating Conditions ◽

Overhead Line ◽

Zero Sequence ◽

The Moment ◽

Zero Sequence Voltage

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A Novel Neutral-Point Potential Balance Strategy for Three-Level NPC Back-to-Back Converter Based on the Neutral-Point Current Injection Model

Mathematical Problems in Engineering ◽

10.1155/2015/736828 ◽

2015 ◽

Vol 2015 ◽

pp. 1-12 ◽

Cited By ~ 2

Author(s):

Yingjie Wang ◽

Haiyuan Liu ◽

Wenchao Wang ◽

Kangan Wang

Keyword(s):

Balance Control ◽

Neutral Point ◽

Control Algorithms ◽

Model Based ◽

Point Potential ◽

Injection Model ◽

Zero Sequence ◽

Flow Through ◽

Dc Bus ◽

Zero Sequence Voltage

The neutral-point (NP) potential balance control in three-level neutral-point-clamped (NPC) back-to-back converter is a research nodus. Its current strategies are the same as the strategies of a single three-level NPC converter. But the strategies do not give full play to its advantages that the neutral-point current can only flow through the connected midlines in both sides of the converter but does not flow through the DC-bus capacitors. In this paper, firstly the NP potential model based on the NP current injected is proposed. It overcomes numerous variable constraints and mutual coupling in the conventional model based on the zero-sequence voltage injected. And then on this basis, three NP-potential balance control algorithms, unilateral control, bilateral independent control, and bilateral coordinated control, are proposed according to difference requirements. All of these algorithms use the midlines rather than the DC-bus capacitors to flow the NP current as much as possible. Their control abilities are further quantitatively analyzed and compared. Finally, simulation results verify the validity and effectiveness of these algorithms.

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