Distance Protection Of Transmission Lines Research Articles

Studying a novel method for mitigation of the adverse impacts of SFCL on transmission line distance protection

In the situation where the superconducting fault current limiter (SFCL) is installed at the downstream of voltage transformer, the apparent impedance seen by the conventional distance relay changes significantly. In this study, a novel method is proposed to improve the performance of distance protection in the presence of SFCL. The calculated apparent impedance is corrected using the information of the appeared voltage among SFCL terminals during fault conditions. The proposed approach is immune to the impedance characteristic of SFCL during fault conditions. Hence, it is independent of SFCL topology and is able to be applied to different fault current limiting concepts. Moreover, the proposed method has the flexibility so that the sensitivity is kept even if SFCL is not picked up. For verification, three types of SFCL involving the saturated iron-core type SFCL, hybrid type SFCL, and transformer isolated bridge type SFCL are modelled in PSCAD/EMTDC software. Then, the assessments are carried out for factors such as fault type and fault location. The results show the accuracy and simplicity of the proposed approach while keeping the original setting of the protective zone.

Secure transmission line distance protection during wide area cascading events using artificial intelligence

The problem of distance protection misoperation has been a research priority recently because it was a major contributing factor in blackouts around the world such the 2003 US-Canada blackout and the 2015 Turkish blackout. In this paper, we propose a method that uses local relay data to enhance the security of zone 3 distance protection for transmission lines, even during wide area cascading events. Three k-nearest neighbor classifiers are trained using the details coefficients of discrete wavelet transform of the aerial mode currents without using any voltage signals altogether. The first classifier determines whether a fault has occurred. The second and third classifiers collectively determine whether this fault is within the zone 3 reach of the relay. If the second and third classifiers determine that the fault is outside the zone 3 reach of the relay, then a blocking signal will be sent to the relay to prevent operation even if the impedance falls within the operating characteristic of the relay. Alternatively, if the second and third classifiers determine that the fault is within zone 3 reach of the relay, a permissive trip signal will be sent to the relay only if the fault has not been cleared.

A faulted side identification scheme-based integrated distance protection for series-compensated transmission lines

This paper introduces an integrated distance protection technique for series-compensated transmission lines (SCTLs) based on a new scheme to identify the faulty side with respect to the compensator. Conventional distance algorithms suffer from mal-operation under faults behind the Series Compensator (SC). Therefore, the modified mathematical algorithm of the distance relay treats with these faults via compensating the voltage drop through the SC to integrate the relay performance along the line. Consequently, the faulty side either upstream or downstream the SC must be identified. This identification is accomplished via a new function inserted in the mathematical algorithm. The presented function is a voting system based on both of the angles of the obtained conventional and modified apparent impedances. The presented voting scheme is based on basics theories of the fault analysis and the phasors diagrams of the equivalent apparent impedances seen by the conventional and modified algorithms whether the fault is upstream or downstream the SC. The presented scheme is suitable for all fault types even with high fault resistances. MATLAB package is used to simulate 400 kV compensated transmission lines and also to implement the presented algorithm. Diverse fault cases are investigated to test the response of the presented voting system under different fault conditions including the fault type, location, and impedance. The results confirm the efficacy of the presented scheme.

The Modeling and Simulation Research on High-Voltage Transmission Line Distance Protection Devices

Transmission line protection is a very important part of the power system. In order to effectively study the distance protection of high-voltage transmission lines, this paper introduces the setting and operation of distance protection., build the mode with Simulink tool box in the software of Matlab, and simulate the mode by S functions. The simulation results illustrate the Matlab software can effectively reflect the behavior of the distance protection when there are some faults in the simulated transmission line, which proves a simple and effective method to research the relay protection in the power system.

Distance protection of EHV long transmission lines considering compensation degree of shunt reactor

This study investigated the feasibility of distance protection in extra-high voltage (EHV) networks. In long-distance transmission lines, the distributed parameter characteristic of the EHV network is obvious. When a fault occurs far away from the measurement site, the measured impedance might not be directly proportional to the fault distance, and the protection domain of distance protection will be decreased. The detailed theory inferred and proven in this paper reveals that this phenomenon is widespread in EHV transmission lines. The results indicate that the protection domain error is greatly reduced by the application of the shunt reactor. Overall, simulation results show that the proposed method is effective for impedance relay, considering different characteristics, different lengths of lines, and compensation degrees.

Emulation of Auto-Reclosing Scheme with Adaptive Dead Time Control for Protection of Series Compensated Transmission Line

Series compensation plays an important role in smart power grid to improve power transfer capacity and voltage profiles. Majority of faults occurring in grid are transient in nature. However, discrimination between transient fault and permanent fault are contemporary problems in the field of distance protection of transmission line. Auto-reclosure is one of the foremost solutions for the same. This paper demonstrates implementation of auto-reclosing scheme using Modified Full Cycle Discrete Fourier Transform with adaptive dead time control. The fault detection logic is based on monitoring impedance trajectory in the R-X diagram of distance relay. The reclosing instance is identified by examining differential voltage across the contacts of circuit breaker. During transient fault condition, based on the time by which the breaker voltage retarded to normal value (below preset threshold) is used to set adaptive dead time of reclosure. Software validations have been performed with the variation in fault location, fault resistance, and fault location with varying line compensation level. Real time validation is also performed using digital signal controller on laboratory prototype. The outcome of simulation and emulation indicates substantial reduction in dead time indicating effectiveness of the developed scheme.

Temperature safety analysis and backup protection scheme improvement for overhead transmission line in power oscillation condition

The oscillating block module is usually adopted to avoid false action of distance protection of overhead transmission lines during power oscillation. However, this scheme ignores the safe operation of conductor temperature during oscillating block. This paper focuses on the conductor overheating problem and safety protection issue during power oscillation. Firstly, through analysis the differences in conductor temperature calculations under oscillating current, short-circuit current and normal load, a numerical iterative method of conductor temperature rise (CTR) calculation under power oscillating current is proposed using the transient thermal balance equation. Then, the safe operation scheme of transmission line is proposed by setting temperature alarm and temperature off-limit trip out. An improved backup protection based on the combination of temperature and impedance is proposed to avoid false action of distance protection, also provide overheating protection for transmission line during power oscillation. Finally, a two-source power system and the modified 29-bus system are adopted to verify the CTR calculation and the improved backup protection. Results indicate that the proposed scheme can provide effective evidence of safe operation and relay setting for transmission lines through excavating the tolerance ability of overcurrent and oscillating current.

Impact of ‘intermediate’ sources on distance protection of transmission lines

A strategy to evaluate the impact of intermediate sources on the performance of transmission line distance protection is proposed in this study. The influence of an intermediate infeed on the sensitivity of the reach setting and the resulting tripping performance of a distance protection scheme is the main emphasis of this study. The proposed strategy considers the effectiveness of various protection schemes on the protection challenges expected on the National Grid transmission network due to future changes in the generation mix. PowerFactory (DIgSILENT PowerFactory software package) will be used to simulate a double circuit transmission network, when a fault occurs and the strength of the main and intermediate sources change from weak to typical to strong. This study discusses various solutions to the problems observed and a methodology for adapting the grading strategy of distance protection as transmission networks evolve into the future.

Fault Studies and Distance Protection of Transmission Lines Connected to DFIG-Based Wind Farms

Doubly fed induction generator (DFIG) based wind farms are being increasingly integrated into power grids with transmission lines, and distance protection is usually used as either the main or the backup protection for the transmission line. This paper analyzes the composition of a DFIG short circuit current and indicates the existence of a rotor speed frequency component. By analyzing several real fault cases of the DFIG-based wind farms connected to transmission lines, the weak power supply system and current frequency deviation of the wind farm side are illustrated. When a fault occurs on the transmission line, the short circuit current on the wind farm side is small and its frequency may no longer be nominal due to the existence of rotor speed frequency component, whereas the voltage frequency remains nominal frequency because of the grid support. As a result, the conventional distance protection cannot accurately measure the impedance, which can result in unnecessary circuit breaker tripping. Therefore, a time-domain distance protection method combined with the least-squares algorithm is proposed to address the problem. The efficacy of the proposed method is validated with real fault cases and simulation.

Distance protection for transmission lines of DFIG-based wind power integration system

This paper proposes a distance relay in time domain based on the R-L differential-equation algorithm which is suitable for wind power integration system. However, the conventional R-L differential-equation algorithm cannot detect the correct fault direction if the fault point is very close to the relay location. Therefore, this paper mainly focuses on this problematic conditions and proposes a solution. The instantaneous value equivalent model of DFIG is established and characteristics of the transient electromotive force (EMF) of DFIG after the faults are also analyzed, which shows that the EMF of DFIG has the inertia within a short time after the faults. The memory voltage drop and actual voltage drop on equivalent impedance from relay location to back-side and opposite-side equivalent power sources are introduced in this paper to detect the fault direction. Meanwhile, the characteristics of the memory voltage drop and actual voltage drop under forward and reverse fault conditions are deduced, respectively. With the differentiated correlation coefficient between the memory voltage drop and actual voltage drop under different fault conditions (forward and reverse fault), the fault direction identification criterion is formed accordingly. Finally, an extensive performance evaluation using PSCAD/EMTDC simulation corroborates the effectiveness of the proposed method. Results show that the proposed method can detect the fault direction quickly with high sensitivity during zero-voltage fault conditions.

Performance evaluation of distance protection of transmission lines connected with VSC-HVDC system using closed-loop test in RTDS

Voltage Source Converter (VSC) based High Voltage Direct Current (HVDC) can control voltage and power flow on ac transmission lines with the priority of reactive current support during the fault as suggested in the grid codes for HVDC connections. Furthermore, the fault current contribution from the converter is limited in magnitude and modified in the waveform in order to protect the power electronic devices during the fault, which on the other hand affects the apparent impedance seen by the distance relay. This paper addresses the challenges faced by the distance protection of transmission lines connected with VSC-HVDC system by performing a closed-loop test of a commercial distance relay using Real Time Digital Simulator (RTDS). The power system with VSC is modeled in detail under a more realistic scenario in RTDS so that the performance of the distance protection can be tested under near to actual field conditions. The responses of the commercial distance relay for balanced and unbalanced faults are analyzed. The oscillograph data of the voltage, current and protection bits recorded by the relay are extracted and compared with the simulation results.

Effects of VSC based HVDC system on distance protection of transmission lines

The priority to reactive power contribution from the Voltage Source Converter (VSC) based High Voltage Direct Current (HVDC) connection to support the grid during faults as suggested by the modern Network Code (NC) for HVDC affects the distance protection of transmission lines. Moreover, suppressing the negative sequence current during an unbalanced condition also interferes with the proper operation of the distance relays. This is because the current contribution from the converter is limited in magnitude and modified in the waveform in order to protect the power electronic devices during the fault in comparison to the synchronous generator fault current characteristics. This paper discusses the cause as well as the severity of the problems faced by the distance protection of transmission lines connected to the VSC based HVDC system by analyzing the apparent impedance analytically and in the simulation. The response of the relay to balanced and unbalanced faults lying on transmission lines is investigated. It is shown that the VSC limited reactive support and suppressed negative sequence current affect fault detection, forcing the relay to malfunction. The results of this paper can be used as a reference for understanding the effects of VSC-HVDC system on the operation of the distance protection during faults.

A continually online trained impedance estimation algorithm for transmission line distance protection tolerant to system frequency deviation

Distance relays are protective devices which main goal is the protection of transmission lines. However, the presence of harmonics and the exponentially decaying DC offset in the system voltage and current signals negatively affects the relay performance. In this paper, an adaptive phasor estimation method based on Artificial Neural Networks is presented to reduce these components’ effects, focusing on impedance estimation for distance relaying. The method uses the multilayer perceptron architecture to estimate the current and voltage signals, and then proceeds to calculate the complex apparent impedance during a continually online training process. This online training allows for adaptability regarding the system frequency, providing tolerance against its deviation. Graphical results of the test cases are presented, comparing the functionality and performance of the proposed algorithm with a Fourier-based method.

Studies on the active SISFCL and its impact on the distance protection of the EHV transmission line

The active saturated iron-core superconductive fault current limiter (SISFCL) is a good choice to decrease fault current. This paper introduced the principles and impedance characteristic of the active SISFCL. Then, it shows the current-limiting effects of the SISFCL. Besides, the impact of the active SISFCL on the distance protection of the EHV transmission line is evaluated. Based on that, the coordination scheme of the distance protections is proposed. A 500 kV double-circuit transmission system with SISFCLs is simulated by Electro-Magnetic Transients Program including DC (EMTDC). Simulation tests demonstrate the correctness and validity of theoretical analyses.

Synchrophasor‐based backup distance protection of multi‐terminal transmission lines

The distance protection of multi-terminal transmission lines need to be redesigned due to possible changes in the backup protection emanating from probable infeed currents produced from tapped transmission lines. Furthermore, high-resistance fault is another factor that relay become under-reach and cannot correctly identify the fault. In this study, an algorithm is presented based on synchrophasors. In this method, voltage and current signals of buses will be sent to system protection centre (SPC) and in SPC an algorithm based on active power calculation in buses is provided that is able to eliminate the effects of both mentioned factors. In this method, measurement or relay in tapped transmission line location are not required. The study includes analytical analysis and modelling and in modelling results a variety of faults with different fault resistances is considered. Two power systems including teed-feeder system and IEEE 14-bus power system are considered. The results show that in both power systems, and different types of faults, backup distance protection is improved. Simulations are conducted by Electro-Magnetic Transient Program works.

An adaptive approach for three zone operation of digital distance relay with Static Var Compensator using PMU

Modern energy transmission systems suffer from great voltage dropping due to enormous loads. Therefore appropriate schemes should be devised to regulate the voltage. FACTS devices such as Static Var Compensator are often used for this purpose. However, SVC at mid-point of transmission line may leads to deteriorate of distance relay operation, resulting in inaccurate estimation of faults locations i.e. over-reach or under reach for different cases. This paper proposed a new algorithm that utilizes synchronized phasors measurement (SPM) to enhance the operation of distance protection zone in many aspects. The proposed method is tested for 230 kV system simulated in EMTDC/PSCAD with Bergeron model of transmission line. The results prevailed for adaptive approach scheme are more accurate, victor and robust in equivalence with usable transmission line distance protection with SVC.

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

Adaptive distance protection setting in presence of mid-point STATCOM using synchronized measurement

Abstract EHV and HV transmission lines are used widely to transfer power from power generating area to large load centers. Nowadays compensating devices which uses modern power electronic devices are mostly used to improve the power transfer capability of transmission lines. Use of FACTS devices in transmission lines affect protection system very drastically. In this paper, the issues related with distance protection of transmission lines with STATCOM connected at mid-point are addressed. To mitigate the problems associated with distance protection, a novel algorithm based on synchronized measurement for adaptive relay setting is proposed. The power system is modeled in EMTDC/PSCAD software with frequency dependent model of transmission line. The results obtained for the new adaptive setting scheme are accurate, robust and superior in comparison with those obtained from existing distance protection schemes for transmission line with STATCOM.

Transmission Lines Distance Protection Using Differential Equation Algorithm and Hilbert-Huang Transform

This paper proposed the scheme of transmission lines distance protection based on differential equation algorithms (DEA) and Hilbert-Huang transform (HHT). The measured impedance based on EDA is affected by various factors, such as the distributed capacitance, the transient response characteristics of current transformer and voltage transformer, etc. In order to overcome this problem, the proposed scheme applies HHT to improve the apparent impedance estimated by DEA. Empirical mode decomposition (EMD) is used to decompose the data set from DEA into the intrinsic mode functions (IMF) and the residue. This residue has monotonic trend and is used to evaluate the impedance of faulty line. Simulation results show that the proposed scheme improves significantly the accuracy of the estimated impedance.

Optimized echo state networks using a big bang–big crunch algorithm for distance protection of series-compensated transmission lines

Distance protection of transmission lines compensated by Thyristor-Controlled Series Capacitor (TCSC) suffers malfunction due to series variable voltages injected by TCSC. To mitigate the problem, echo state networks (ESNs) are used in this paper through the voltage compensation technique by subtracting estimated TCSC voltages from measured phase voltages where fault loop observed by the relay contains TCSC. The design parameters of ESNs are optimized using a big bang–big crunch (BB–BC) algorithm with an especial random generation scheme in big bang phase. Main features of our study are: (a) only locally measured phase currents at the relaying point is used, assuming firing angles and other variables of TCSC are not accessible there; and (b) high accuracy of estimations is achieved using optimized ESNs for a large number of test cases. The method is tested on a 400km, 500kV line for all fault types using Matlab/Simulink. Tests for 7680 cases with varying fault resistance, fault inception-angle, fault location, load angle and compensation degree show much improved accuracy of estimations by ESN in comparison to time-delay neural network (TDNN), radial basis function neural network (RBFNN), nonlinear autoregressive network with exogenous inputs (NARX) and Elman network particularly at instants immediately after fault incidence. The effectiveness of the ESN-based method is examined using two distance relay algorithms.