Protection For EHV Transmission Lines Research Articles

A simple approach for the protection of EHV transmission lines

A simple approach for the protection of EHV transmission lines

A Simple Approach for the Protection of Ehv Transmission Lines

A Simple Approach for the Protection of Ehv Transmission Lines

A novel EHV transmission line protection of adequate fault-resistance sensitivity and faulted-phase selectivity

The summation impedance relay (SIR) is characterized by a strong sensitivity to high-resistance faults. However, previous studies have not made SIR completely immune to the adverse influence of distributed capacitive currents and have ignored its inherent deficiency of faulted-phase selectivity. Therefore, a novel protection scheme is proposed. First, by compensating distributed capacitive currents, an improved ground-type SIR (composed of ground distance relays) is created. Using this SIR, the identification of internal high-resistance faults is performed while guaranteeing security under external faults. Then, a novel phase-type SIR (composed of phase distance relays) is designed, based on which a suitable phase-selection algorithm is proposed to distinguish single-phase faults and multi-phase faults. Comprehensive simulations show the security and dependability of the proposed protection scheme in various fault scenarios, including non-linear high-impedance faults and series compensation scenarios. Moreover, the approach’s performance under power swings is investigated, revealing its complementarity with existing protection principles.

Real-Time Wide-Area Disturbance Monitoring and Protection Methodology for EHV Transmission lines

This paper presents a real-time wide-area disturbance monitoring and protection (RWADMP) methodology for the backup protection of EHV transmission lines in smart grids (SG). The proposed methodology employs harmonic phasors (1st, 2nd, and 3rd order) of 3-Φ current signals estimated using multi-phasor measurement unit (MPMU) for fault detection, classification, and discrimination of faulty line accurately. Further, the stressed condition such as load encroachment is discriminated from fault. The phasors which were estimated at MPMU are communicated to phasor data concentrator (PDC) at system protection center. MPMU is realized in hardware using NI cRIO, current sensor and GPS module in conjunction with LabVIEW software. Performance of the proposed methodology has been validated on the scale down laboratory models of 400 kV EHV transmission systems such as two-generator two-bus and two-generator three-bus systems. The experimental results show the efficacy of the proposed methodology in improving the overall reliability of the protection system. Also, the proposed methodology is less sensitive to the different fault conditions like fault resistance (FR) and fault distance (FD). Further, the user-friendly LabVIEW monitoring system enhances the visualization of the power system state in PDC. Also, it helps the grid operator to take appropriate action in case of system stressed condition and avoids the mal-operation of the protective devices.

New development in relay protection for smart grid

This series of papers report on relay protection strategies that satisfy the demands of a strong smart grid. These strategies include ultra-high-speed transient-based fault discrimination, new co-ordination principles of main and back-up protection to suit the diversification of the power network, optimal co-ordination between relay protection and auto-reclosure to enhance robustness of the power network. There are also new development in protection early warning and tripping functions of protection based on wide area information. In this paper the principles, algorithms and techniques of single-ended, transient-based and ultra-high-speed protection for EHV transmission lines, buses, DC transmission lines and faulty line selection for non-solid earthed networks are presented. Tests show that the methods presented can determine fault characteristics with ultra-high-speed (5 ms) and that the new principles of fault discrimination can satisfy the demand of EHV systems within a smart grid.

Impact Analysis of midpoint Connected STATCOM on Distance Relay Performance

This paper presents the impact of the Static Synchronous Compensator (STATCOM) on the performance of distance protection of EHV transmission lines. A 400kV transmission system having midpoint connected STATCOM with its control circuit is modeled using MATLAB/SIMULINK software. The impact of STATCOM on distance relay for different fault conditions and different fault locations is analyzed. Simulation results indicate that the presence of the STATCOM in the transmission system significantly changes the line impedance seen by the distance relay to be lower or higher than the actual line impedance. Due to this the performance of the distance relay changes, either overreaches or under reaches. DOI: http://dx.doi.org/10.11591/telkomnika.v13i2.6987 Full Text: PDF

Power Balance Protection Using Long-distance Discretization Equation for EHV Transmission Lines

Based on the distribution parameters equation of long-distance transmission lines, which is expressed in phasor form, the paper proposes a discretization equation model, analyzes the protection of EHV transmission lines with shunt reactors by applying power balance principle and then the power balance protection criterion is determined. The power balance protection method, which is based on discretization equation of long-distance transmission lines, maximizes the use of the fault information such as voltage and current, etc. In this way, the fault of EHV transmission lines with shunt reactors can be removed accurately and quickly. On the other hand, this method is more convenient for modern microprocessor protection to process the discrete data and improve the power system performance after the criterion of power balance protection is determined. Results of EMTP simulation have demonstrated that under various fault conditions of EHV transmission lines with shunt reactors the power balance protection method has higher sensitivity and reliability and can be applied to identify the internal or external fault correctly.

Analysis of the electrical characteristics and surge protection of EHV transmission lines supported by tall towers

The electrical characteristics of a new 280-m-tall transmission line are analyzed. The geometrical distance of the phases, wires height and physical structure of the line are intrinsic associated with its electrical performance in steady state as well as in transient conditions. Thus, a frequency-domain analysis is proposed comparing the longitudinal and transversal electrical parameters calculated from the tall transmission line with the same parameters obtained for a conventional 440-kV line. An adapted method for the mutual parameters is proposed to calculate the shunt capacitances considering two dielectrics between the wires and ground (air and forest), taking into account that the new transmission system has not a corridor, as usually observed in conventional lines. A second analysis is performed based on both lines modeling and time-domain simulations using the EMTP. Electromagnetic transient simulations from an atmospheric impulse shows that the tall transmission line has a major transient overvoltage than a conventional line. In sequence, an alternative surge protection is proposed using metal-oxide arresters connected directly at the phases, in parallel with the line insulators. The main objective of this technical report is to evaluate the electrical characteristics of the new transmission system using tall structures and, by this means, to highlight the possible variations concerning its operation and transient response.

Equal transfer processes-based distance protection of EHV transmission lines

The overreach of the distance protection caused by CCVT is still a serious problem for high-speed line protections. Based on the theory of Equal Transfer Process of Transmission Lines (ETPTLs), a new high-speed distance relay scheme is proposed in order to overcome above problem. The solution is to make the three-phase voltages and currents at the relay location and the voltage at the fault point have the same transfer links by virtue of a new design. Three major steps of the new method are demonstrated: re-structuring of the voltage at the fault point, the virtual digital transfer method and solving the R–L differential equation. A variety of ATP simulation tests show that the new method effectively reduces the transient error caused by CCVT and improves the operating speed by a series of technical countermeasures including three major steps, iterative calculations of the fault distance and an inverse time delay setting criterion. The distance measuring error is within 5% at approximately 15ms after fault occurrence, which is superior to various adaptive protection algorithms based on CCVT transient error estimation or source impedance ratio (SIR).

A Wavelet Technique for Directional Protection for EHV Transmission Lines with Series Compensation

The author provides a novel directional protection scheme for transmission lines with series compensation capacitors based on travelling waves. The ability of wavelet transform techniques to focus on system transients provides an effective and reliable method for fault detection and classification. Therefore, wavelet transforms are applied to the three phase currents at both ends of the transmission line. Directions and magnitudes of spikes in the wavelet coefficients are used for this purpose. The scheme is able to detect all types of internal faults at different locations in front and back of the series capacitor, at different fault inception angles and at different fault resistances. It also determines the type of fault and detects the faulty phase(s). Furthermore, it can detect external faults and blocks tripping if they exist. The relay remains stable for normal conditions, as well as in the presence of nonfaulty normal transients. The protection scheme is tested by simulating faults using the MATLAB power system toolbox. Simulation results show the high accuracy, security, and dependability of the proposed scheme.

A novel short-window algorithm of phasor computation for EHV line protection

A novel phasor computation algorithm is presented in this paper. The real and imaginary part filters of this algorithm have identical magnitude frequency characteristic (IMFC) at all the frequencies and orthogonal phase frequency characteristic (PFC) at fundamental frequency. Considering the conditions of the same magnitude frequency characteristic (MFC) and the orthogonal PFC, the two-sample algorithm is derived. Once two-sample orthogonal filters with IMFC are obtained, the algorithm design is just to select proper shapes and lengths of windows, which determine the filtering performance and response-time, respectively. This method could be applied to design filter in any window-length, especially in short-window. Therefore, this class of phasor algorithms is suitable for EHV transmission line protection where a short-window is crucial for fast response and better operation performance. The proposed algorithm has been applied to a series of EHV relay devices by China Xuchang Relay Group.

Theoretical concept and digital simulation of the Pramod scheme for UHS protection of EHV transmission lines

The theoretical concept of the Pramod scheme for ultra-high-speed (UHS) protection of EHV transmission lines is described. The principle is based on detection of the fault-induced high-frequency signals of the order of kilohertz. A technique for the digital simulation of the transmission line and the high-frequency detecting circuit is explained, and the results are presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Digitally simulated test performance of the Pramod scheme for UHS protection of EHV transmission lines

The author describes a digital simulation technique for the signal processing of the Pramod scheme and studies the digitally simulated test performance of the scheme for satisfactory operation under different fault conditions. The Pramod scheme is based on the detection of high-frequency voltage signals through stack tuners. It is assumed that the digitally simulated stack tuner output signals are available for the purpose of the signal processing under different fault conditions. The Pramod scheme has been investigated for the discrimination feature of reverse fault, faults at different points of the transmission line, and different types of faults, and the performance has been found satisfactory.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Performance of the Pramod Johns scheme for UHS protection of EHV transmission lines under arcing fault conditions

The performance of the scheme of Pramod Agrawal (1989) for ultra-high-speed (UHS) protection of EHV transmission lines under arcing fault conditions is described. The arc with reignition effect is modeled, and a method for digital simulation of the superimposed arc voltage is discussed. Simulated tests have shown that the arc voltage has significant higher-frequency components. These tests also confirm that the arcing fault response repeats every half-cycle for a fault inception angle of the voltage from 0 to 90 degrees , which is a significant improvement over schemes based on traveling-wave phenomena which have been considered a failure for faults at 0 degrees C fault inception.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Performance of the Pramod Scheme for UHS Protection of EHV Transmission Lines Under Arcing Fault Conditions

Performance of the Pramod Scheme for UHS Protection of EHV Transmission Lines Under Arcing Fault Conditions

Digital simulation of fault autoreclosure sequences. With particular reference to the performance evaluation of protection for EHV transmission lines

The successful development of EHV transmission-line protection increasingly depends on a detailed simulation of power-system faulted responses. In consequence, increasing use is being made of programmable test equipment in which the primary-system responses are simulated digitally. Previous work on digitally simulating faulted-system responses has been concentrated very largely on the initial faulted period prior to the initiation of an autoreclosure sequence. The implications of incorrect operation of protection at any time throughout the process of fault clearance are, however, often serious, and the paper is therefore concerned with detailing methods of frequency-domain simulation which have been developed to greatly extend the capability of computer-based simulation methods in their application to protective-gear testing. Problems associated with the simulation of various network time nonlinearities are overcome, and the new methods enable both 3-phase and single-pole autoreclosure to be simulated. The paper concludes with a presentation of some simulation studies relating to a short 500kV interconnection which is subjected to various transient and sustained fault conditions

Discussion on “New ultra-high-speed directional comparison technique for the protection of EHV transmission lines”

Discussion on “New ultra-high-speed directional comparison technique for the protection of EHV transmission lines”