Single-phase Earth Fault Research Articles

СИСТЕМА "АЛЬТРА" ДІАГНОСТУВАННЯ СТАНУ ІЗОЛЯЦІЇ ЕЛЕКТРИЧНОЇ МЕРЕЖІ ТА ЗАХИС-ТУ ЇЇ ВІД ОДНОФАЗНИХ ЗАМИКАНЬ

One of the problems in an electrical network with an isolated (compensated) neutral is the selective determina-tion of a damaged element during a single-phase earth fault. Taking into account the negative impact of single-phase earth faults on the equipment of electrical networks with an isolated or compensated neutral, as well as improving the electrical safety conditions of people and animals, it is necessary to install selective protections with the of turning off of damaged element. Selective operation of protections against such damage can be en-sured on the basis of the analysis of zero-sequence currents, phase voltages and zero-sequence voltage of the bus section from which these feeders are powered. As operational experience has shown, selective operation of pro-tection against single-phase earth faults in such networks can be ensured only with the use of digital devices. The work considers the "Altra" system, designed for diagnosing the state of insulation, protecting feeders of 6-35 kV from single-phase earth fault, recording analog and binary signals of electrical installations. Altra digital protec-tion simultaneously covers up to 28 feeders, which provides comprehensive protection against single-phase earth faults of all substation feeders. The working algorithm of the developed protection against single-phase earth faults is based on the analysis of the transient process immediately after the occurrence of damage, which provides selective identification of the damaged feeder both in networks with an isolated neutral and in networks with a compensated. The system organizes the recording of oscillograms of emergency processes and infor-mation about damage by "Altra" devices, followed by their transfer to the dispatcher's automated workplace. This makes it possible to carry out a detailed analysis of accidents and diagnose the insulation of the electrical net-work.

Effect of SF6 circuit breaker parameters on switching overvoltages evaluated based on nominal modes of converter transformers

In this work, we set out to investigate the influence of operating currents of SF6 circuit breakers on the magnitude of overvoltages during switching of converter transformers. The experience of electrical equipment operation is analyzed with a focus on the problems associated with the natural aging of insulation, overloads, and switching overvoltages. The methods of equipment diagnostics were used. According to statistical data, at present, about 37% of short circuits between phases and 42% of single-phase earth faults in electrical networks of industrial enterprises occur due to switching overvoltages. The conducted tests showed that the overvoltages emerging during switching by SF6 circuit breakers of converter transformers, which are used in aluminum smelters, may reach a three-fold rated voltage of the network. This threatens the insulation of transformer windings, cable line, and the switch itself. It was established that an increase in operating currents of an LF2 circuit breaker, not exceeding 27.8% of the rated current of the switch, leads to an increase in overvoltages during switching of converter transformers. At a further increase in the operating currents of the circuit breaker by more than 27.8% of the rated current of the circuit breaker, a sharp decrease in the value of switching overvoltages is observed. Therefore, the operating currents of SF6 circuit breakers were established to affect the level of switching overvoltages of converter transformers. The underlying mechanism of this phenomenon was determined, which should be taken into account when improving the reliability of power supply of converter transformers and, consequently, the reliability of aluminum production. The feasibly of resistive-capacitive dampers as the most effective means for limiting overvoltages during switching of converter transformers was confirmed.

Универсальная централизованная защита от однофазных замыканий на землю в кабельных сетях напряжением 6–10 кВ

Selective protection against single phase earth faults in distribution 6–10 kV cable networks can be performed both with the use of individual (per connection) and centralized devices covering all connections of the protected object. The advantages of centralized devices are reduction of specific (per connection) costs of protection, simplification of its operation and design. Well-known technical solutions in terms of centralized protection devices against this type of damage do not always provide versatility (the possibility to use neutral cables of 6–10 kV in various grounding modes) and high technical perfection (selectivity and stability of operation). Thus, it is relevant to develop a universal centralized protection against single-phase earth faults, ensuring high technical perfection for all types of earth faults in 6–10 kV cable networks with different neutral grounding modes. The authors have used a comprehensive simulation model "cable network – protection device" to study the selectivity and stability of the developed principles of implementation and algorithms for centralized protection against earth faults. The model is designed in SimPowerSystems and Simulink software. The configuration and parameters of the cable network model have been selected considering the key features of 6–10 kV distribution cable networks of industrial and urban power supply systems. A universal centralized protection against all types of earth faults in 6–10 kV cable networks with various neutral grounding modes has been developed. The results of functional tests on the simulation model have confirmed the effectiveness of the developed algorithms of the developed centralized protection for all types of earth faults both in uncompensated and compensated cable networks of 6–10 kV. The proposed technical solution implements a multifunctional multiparametric centralized protection against earth faults. It has such properties as versatility, selectivity, and high stability of operation for all types of earth faults, recognition of types of single-phase earth faults, continuity of action in stable and most dangerous arc intermittent earth faults.

Studying the Single-Phase Earth Fault Protection Based on Measuring the Negative-Sequence Current

Studying the Single-Phase Earth Fault Protection Based on Measuring the Negative-Sequence Current

Principles of protection against single phase earth faults in networks with capacitive current compensation

Principles of protection against single phase earth faults in networks with capacitive current compensation

Medium voltage digital instrument transformer

Instrument transformers with digital output provides significant advantages, including those related to increased reliability of power system operation. With the appearance of digital instrument transformers, the topology of the measurement channel and the functional purpose of its components change. This paper considers some function migration examples from protection devices to the primary converter (digital current and voltage transformer). Combined digital transformers expand the application area of distance protection principles, increase the fault location accuracy, as well as improve sensitivity and speed of single-phase earth fault (SPF) protection in 6-35 kV networks.

РАЗРАБОТКА КОМПЛЕКСНОЙ МЕТОДИКИ ОПРЕДЕЛЕНИЯ ТОКОВ ОДНОФАЗНЫХ ЗАМЫКАНИЙ НА ЗЕМЛЮ В РАСПРЕДЕЛИТЕЛЬНОЙ СЕТИ КАРЬЕРА

The paper discusses methods for determining single-phase ground fault currents in the quarry's electrical distribution network. The appearance of these short circuits in an electrical network with an isolated or compensated neutral leads to the appearance of significant overvoltages of undamaged phases at the time of the circuit and a decrease in the stability of the functioning of protection devices against single-phase ground faults. It has been established that oscillography is carried out to study the components of higher harmonics in the groundfault current, the network voltage, the neutral bias voltage, as well as to determine the time required to restore the voltage on the grounded phase to a normal value after disconnecting the ground fault. Methods for determining the current of single-phase earth faults by indirect methods are presented, corresponding measurement schemes are presented in the absence of natural unbalance voltage, without a voltage transformer, as well as at a certain value of natural unbalance voltage...

Influence of Ultra-High-Voltage hybrid reactive power compensation on interruption performance of circuit breakers under different faults

For extremely large ultra-high-voltage (UHV) power transmission and distribution lines with typical project using hybrid reactive power compensation (HRPC), single-phase earth fault (1LG), three-phase ground fault (3LG), phase-to-phase fault (2LS), and two-phase grounding fault (2LG) often occurs. Circuit breaker is one of the most critical equipment of UHV transmission system. And the interruption performance is crucial to circuit breakers’ breaking capability. In this study, formal expressions of the indicators for the interruption performance of the circuit breaker are deduced in case of different faults based on the equivalent-valued parameter circuit based on the structure a UHV demonstration project. The simulations are used to validate the accuracy of formal expressions. Then, the influence of such factors as the location of the fault and the degree of HRPC on the interruption performance of the 1LG, 2LG, 3LG, and 2LS is analyzed. Finally, the interruption performance of circuit breakers under different faults are compared. A quantitative evaluation of the influence of changes in the relevant indicators on the interruption performance of circuit breakers can provide a technical basis for choosing the appropriate design of the circuit breaker in light of the application as well as equipment development and assessment.© 2017 Elsevier Inc. All rights reserved.

Including Shield Wires in the Analysis of Transient Processes Occurring in HVAC Transmission Lines

The article presents an analysis of electromagnetic transient processes in long ultra-high voltage transmission lines, taking into account shield wires. It was shown that EMTP and Matlab/Simulink software are currently widely used in the study of transient processes in power lines. The EMTP software package uses the finite element method when integrating the equation that mathematically models the distributed parameter transmission line. The Matlab/Simulink software uses the d’Alembert method. In both cases, it is not known how the boundary conditions for the partial differential equation that mathematically models the transmission line are determined. The power line is analyzed as a distributed parameter system, described by a second-order partial differential equation. The advantage of the proposed method of calculating the boundary conditions for the abovementioned equation is the use of boundary conditions of the second and third types of Neumann and Poincaré, which allowed us to take into account the mutual influence of shield wires and phase conductors of the line in one power system. On this basis, the methodology for obtaining time domain graphs, spatial distributions, and traveling wave distributions of voltages and currents for phase conductors and line shielding wires is presented. The results of a computer simulation of transient processes when switching on the power line, taking into account controlled phase commutation and under single-phase earth fault conditions, are presented. All calculation results of transient processes presented in the article were obtained exclusively using numerical methods.

Development of a method for selective determination of the outgoing line and the distance to the place of occurrence of a single-phase earth fault

Subject of research: algorithms for selective determination of the outgoing line in the event of a single-phase earth fault; algorithms for determining the distance to the fault location.
 Purpose of research: development of an industrial frequency overlay method for determining the outgoing line with a single-phase earth fault. Development of an algorithm for determining the distance to the place of a single-phase earth fault by the method of standing waves.
 Object of research: electrical networks 6-35 kV.
 Methods of research: theory of electrical circuits, mathematical analysis and modeling; resonant modes; standing wave method.
 Main results of research: An algorithm for the selective determination of the outgoing line with a single-phase earth fault has been developed. An algorithm for determining the distance to the closure site by the standing wave method has been developed.

Development of an arc extinguishing reactor control system

Subject of research: the system of automatic control of the arc-extinguishing reactor.
 Purpose of research: development of an automatic control system of an arc-extinguishing reactor to improve the efficiency of the electrical network.
 Object of research: 6-35 kV electric networks with compensated neutral through an arc-extinguishing reactor.
 Methods of research: the main provisions of the theory of electrical circuits, mathematical analysis and modeling, numerical programming.
 Main results of research: The article proposes the idea of using the wavelet transform to organize software The article proposes a refined mathematical model of a distribution network with an arc-extinguishing reactor, which allows to increase the accuracy of determining network parameters, including the neutral offset voltage. The algorithm of the reactor settings according to the extreme method in the absence of a single-phase earth fault in a distribution network with a high natural asymmetry.

RESEARCH OF ADAPTIVE RELAY PROTECTION AGAINST SINGLE-PHASE EARTH FAULTS IN 6-35 KV POWER GRIDS

This article shows the results of a study of relay protection against single-phase earth faults. The originality of the study lies in a completely new approach to identifying the fault feeder by the constant component in the zero sequence current. Further research is currently underway. In the article there is a review of one of the received patents for the invention of the Republic of Kazakhstan.

Study on fault waveform library of PT high voltage side fuse in hydropower station

In the arc-suppression coil grounding system of a medium voltage distribution network, high voltage side voltage transformer insurance fusing faults frequently occur, including fusing during startup and grid connection, fusing during operation, fusing during the shutdown, etc., which will directly affect the accuracy of measurement, metering, protection, and other secondary equipment. In this paper, we used the calculation of electromagnetic transient EMTP-ATP software, theoretical analysis of the typical hydropower station wiring and parameters of the medium voltage system, set up the improved model of neutral point grounding system, simulation of single-phase earth fault line and disappeared in the transient process, calculation of PT transient current, to verify that the way to study the mechanism of frequent fusing of fuse in the PT. Typical fault waveform databases are established under different bad working conditions (ferromagnetic resonance, low-frequency nonlinear oscillation, lightning wave invasion, etc.).

ERROR ESTIMATION OF THE DEVELOPED METHOD FOR UNGROUNDED AC SYSTEMS TO DETERMINE THE NETWORK INSULATION

The problem of efficient and safe mining has recently become more relevant due to the intensification of production processes, for example, during the operation of electrical installations at mining enterprises, the insulation of electrical networks and electrical equipment undergoes a change in the electrical insulating properties of materials, which reduces the electrical safety. The network insulation admittance determines the safety of electrical receivers and operational personnel in mining facilities, since the current of a single-phase earth fault is directly proportional to the value of the network insulation admittance, and by controlling its active and reactive components, this will allow for a violation of the integrity of the insulation, thereby taking preventive measures. The article depicts the analysis of the reliability of the devised method by estimating the error of insulation parameters in ungrounded AC systems which is done by indirect measurements. Graph-analytical studies of relative root-mean-square error reveal that the accuracy of the calculation in the devised method can be effectually managed by selecting the susceptance of the additional capacitor and accuracy class of measuring units.

Identification of single-phase ground faultin networks 6-35 kV using the wavelet transform

Subject of research: methods for selective determination of an outgoing line with a single-phase earth fault based on the relative measurement of higher harmonics.
 Purpose of research: to develop a method for software filtering of high-frequency components and a method for identifying a line with a single-phase ground fault.
 Object of research: distribution networks 6-35 kV.
 Methods of research: wavelet-transformation of zero-sequence currents and voltages.
 Main results of research: the article proposes the idea of using the wavelet transform to organize software filtering of the zero-sequence current in order to increase the sensitivity of the admittance protection. On the basis of the wavelet transform, a modernization of the algorithm for determining a power line with a single-phase earth fault is proposed according to the principle of relative measurement of the energy of the spectrum of higher harmonics. The paper proposes to determine the energy of the spectrum by the wavelet coefficients of the discrete wavelet transform.

"Approbation of the developed method for determining network insulation parameters on an operating excavator"

"One of the factors that determine the safety of electrical installations in ungrounded AC systems is the insulation resistance to earth. Early recognition and fault clearance, accompanied by a change in the active and reactive components of the insulation conductivity in ungrounded AC systems, will ensure work safety in electrical installations. Due to the fact the scale of cases of electrical injuries continues to remain significant, despite the tightening of the requirements of regulatory and technical documentation and the creation of newer effective methods and protection equipment against electric shock, therefore, increasing the level of electrical safety in the operation of mining machines and complexes is an urgent task. The article depicts the results of the approbation of the developed method for determining network insulation parameters on an operating excavator. The developed method is based on measuring phase voltages and angles of their vectors before and after connecting an additional capacitance to the phase of the electrical network and to the earth. According to the developed method, numerical data of the insulation condition in an electrical network with a voltage up to 1000 V and the single-phase earth fault current were calculated. During the approbation of the developed method, the lack of the existing protective residual current device was identified. Keywords: network insulation, admittance, susceptance, neutral shift, zero-sequence voltage. "

A New Model for Correcting and Improving the Sequence Networks Method of Single-Phase Earth Fault to Accommodate All Resistance Grounding Systems

The method of sequence networks is still well-known and widely utilized for analyzing and computing unsymmetrical faults in power system networks today, particularly in solid grounding systems where it was initially introduced for short circuit analysis. When it comes to single-phase earth fault that is a dominant majority type of fault in power distribution grids, different neutral grounding methods with varied impedances result in distinct fault characteristics, to continue utilizing sequence networks could cause inaccurate calculations by the reason of neutral voltage during earth fault does not remain as close to zero as it’s pinned in solid grounding system. As neutral resistance increases gradually, the impact of line-to-ground capacitance becomes more pronounced and can no longer be ignored. In this case, applying sequence networks could lead to calculated results that are far from the actual situations in grids. This paper discovers and proves an obscurely hidden defect of the sequence network, while proposing a new and novel modeling to derive comprehensive equations of fault calculations for all types of resistant grounding systems, including solid grounding, low resistance grounding, high resistance grounding, and ungrounded systems.

Determination of a damaged connection in single-phase earth fault

Subject of research: single-phase earth faults in electrical networks of medium voltage class.
 Purpose of resarch: the development of a simulation model for the analysis of transient processes that occur during a "metallic" single-phase earth fault in a 35 kV electrical network.
 Object of research: distribution electrical networks 6-35 kV operating in isolated neutral mode.
 Main results of research: a simulation model was developed in the Matlab Simulink environment, which makes it possible to analyze the oscillograms of currents and voltages during a single-phase earth fault in networks with an isolated neutral. A method for determining the outgoing line with an earth fault is presented, based on the superimposition of non-power frequency currents. The source frequency is determined based on the condition for the occurrence of a resonant mode. Oscillograms are presented, from which it follows that the current in the damaged phase increases by more than 2 times, which makes it possible to selectively determine the damaged connection.

Overvoltages during Single-Phase Earth Fault in Neutral-Isolated Networks (10÷35) kV

Aims: The purpose of the article is to analyze networks with zero insulation (10 ÷ 35) kV, which have disadvantages that adversely affect the insulation of operating equipment, as a result of which, in modern conditions, it is desirable to improve the operating modes of such networks.
 Place and Duration of Study: Department of Electromechanics (Electrical and electronic engineering).
 Methodology: To limit the surges that occur in such networks, an arc quenching coil is used, the operation of which is based on two processes: a coil that compensates for the capacitive current, a sharp decrease in the voltage recovery rate in the arc range.
 Results: In connection with the above, by carrying out accurate calculations, it is necessary to solve a number of issues on grounding the neutral with active resistance in networks (10÷35) kV: effective grounding of networks, ensuring safety, limiting the impact on communication lines, limitation of emerging surges, ensuring normal operation of switching devices, etc.
 Conclusion: 1. Due to the difficulty of obtaining an accurate adjustment when earthing the neutral through an arcing coil, and even under normal conditions, overvoltages in the phases are likely as a result of the displacement of the neutral. 2. Networks with zero insulation (10÷35) kV have disadvantages that adversely affect the insulation of operating equipment, and in modern conditions it is desirable to improve the operating modes of such networks.3. In networks with an isolated neutral (10÷35) kV, the connection of the neutral to earth with active resistance allows you to significantly limit the extreme voltages that may occur in the network.

ДВУХСТОРОННИЙ МЕТОД ОПРЕДЕЛЕНИЯ МЕСТА ОДНОФАЗНОГО ЗАМЫКАНИЯ НА ЗЕМЛЮ В СЕТЯХ С ИЗОЛИРОВАННОЙ НЕЙТРАЛЬЮ

Relevance Currently, on the part of enterprises operating 6–35 kV distribution networks, there is a request for a deep modernization of networks and the transformation of existing, outdated networks into digital ones. A separate aspect of modernization is the introduction of high-precision measuring devices and new principles of data transmission. At the same time, the probability of damage for various reasons remains. Single-phase earth faults in networks with isolated neutral are still the most common problem in distribution networks that do not have universal solutions. The problem is particularly acute with determining the location of single-phase earth faults. The opportunities provided by the introduction of digital networks can become the basis for the implementation of new algorithms for relay protection and determining the location of damage. Aim of research The article considers, developed by the authors, a two-way method for determining the location of damage in single-phase earth faults according to the parameters of the emergency mode when installing current transformers in all three phases. The two-way method of determining the location of damage is based on the use of zero-sequence currents and voltages, which are determined by calculation for phase current and voltage differences at the beginning and end of the line. The algorithm is focused on digital electrical networks equipped with high-precision measuring transformers and a communication channel. To calculate the parameters of the zero sequence, the differences of the phase emergency parameters at the beginning and at the end of the line are used. Research methods To develop and study a two-way method for determining the location of damage in single-phase earth faults, the principle of superposition in combination with the method of symmetrical components was used. Decomposition of three-phase currents and voltages into symmetrical components is a linear procedure. Therefore, the zero-sequence current in a three-phase line, in accordance with the superposition principle, can be represented as the sum of three zero-sequence currents, each of which is determined by one of the phase currents at zero values of phase currents in the other two phases. This application of the method of symmetric components is valid only for purely emergency values of phase currents. Therefore, in advance, the load current must be excluded from the phase currents of the emergency mode. Results It is shown that the use of the method of symmetric components for single-phase earth faults separately for the damaged phase and undamaged phases makes it possible to determine the zero-sequence current at the site of damage and the intrinsic zero sequence current of the damaged line. It is shown that this separation of the zero-sequence current makes it possible to distinguish two components of the zero sequence in the voltage difference at the ends of the line. Based on the allocation of two components in the current and voltage of the zero sequence, an algorithm for two-way determination of the damage location has been developed, which allows determining the distance to a single-phase earth fault in networks with an isolated neutral. To study the two-way method of determining the location of damage, a network model and a device for determining the location of damage were implemented in the MATLAB Simulink software package. A functional diagram of a two - way damage location detection device is presented. The performed studies on the model of the electrical network have shown the high accuracy of the proposed algorithm for determining the location of damage.