Transmission Line Distance Research Articles

Transient synchronization stability of a weak‐grid connected VSC considering the interaction of outer control loops and PLL dynamics

AbstractSince these large‐scale renewable power generation (RPGs) stations are always located far away from load centres, voltage source converters (VSCs) always operate in weak‐grid connected conditions, due to the long distance of transmission line and increasing capacity of RPGs. Large power disturbance of RPGs easily causes weak‐grid connected VSCs (WG‐VSCs) suffering from transient synchronization instability issue, which is lack of theoretical and quantitative analysis. This paper is motivated to fill this gap. By considering the dynamic interaction of outer DC voltage control, reactive power loop, and phase‐locked loop (PLL), an equivalent synchronization model of a WG‐VSC system is established first. Then, the mechanism of transient synchronization instability is revealed by the combination of equal area criterion and numerical integration method. Furthermore, the concept of feasible region of active power disturbance (FR‐APD) is introduced for the first time. With the constructed FR‐APD, the transient stability of the WG‐VSC system can be confirmed. Finally, experimental results based on the RT‐BOX hardware‐in‐the‐loop platform are presented to verify the theoretical analysis.

Application of SSSC for Voltage Stability Improvement in the Nigerian 330 kV Transmission System using Particle Swarm Optimization Technique

Load imbalance has always been a major cause of voltage instability of the power system network and increase in voltage instability affects the power system reliability. In this paper, static synchronous series capacitor (SSSC) FACTS device was implemented to improve the voltage stability in the Nigerian 330 kV transmission network using particle swarm optimization (PSO) technique. Modelled power system network in the power system analysis toolbox (PSAT) is simulated to determine the existing power flow analysis and the level of instability in the power system generation plants situated in the Northern region. The outcome of the power flow is thereafter, optimized with PSO by generating the relationship with a high prediction accuracy between voltage at each location and an inter-linked transmission line distance of the 330kV. The model was generated with least square method and the high prediction accuracy determination was carried out with R-square value of the polynomial order. The best model was optimized and the entire computations were carried out in MatLab resulting in the determination of the optimal location which was between Jebba transmission and Shiroro generation stations. SSSC FACTS controller was implemented on the optimized transmission line and the simulation results showed that the introduction of SSSC improved the voltage stability of the power system network.

High Impedance Fault Detection and Location in the Nigerian 330 kV Transmission Network Using Adaptive Neuro-Fuzzy Inference System

Fundamentally, the occurrence of high impedance fault (HIF) can be established when an energy filled conductor contacts a semiconductor. The occurrence of HIF can be described to be subtle and disastrous as it results to low current signal and a signal voltage arc if undetected and without implementation of protective measures, leads to the damage of the power system equipment and in many cases fire outbreak. In this study, the occurrence of HIF on the south-south region of Nigerian 330kV transmission line was studied with the data utilized obtained from the Nigerian control center (NCC) Osogbo. The data obtained was modeled in simulink and the outcome at normal condition was obtained. The transmission line distance was split into 4 points with the current signal at each point generated in simulink and exported to the Matlab file. The data in Matlab file was split to train, test and validate at 70%, 15% and 15% respectively. The data analysis performed was sent to Adaptive Neuro-fuzzy inference system (ANFIS) with the current signal at normal condition and at 3-phase HIF was used as input data while the split distance was implemented as the target data to the model. The effectiveness of the model in detecting and locating HIF was obtained and analyzed in a comparative plot of the location distance. From the results presented, the highest error deviation for fault location with ANFIS was 10%. Hence, it was concluded that ANFIS model had a satisfactory outcome in HIF detection and as such should be utilized for the HIF detection and location.

Impact of power flow on the apparent impedance calculated by the distance protection in transmission lines

AbstractThe reach of primary protection zones of transmission lines distance relays is affected when large power flows circulate through the transmission line prior to a short circuit occurrence. This can cause improper operation of the protection system in certain scenarios. In practice, protection zone adjustments are made by considering the apparent impedances obtained from short‐circuit simulations in the line of interest using standard methods such as IEC 60909‐0 or ANSI/IEEE C37.010. However, these short‐circuit calculation methods omit the existing operating conditions prior to the fault. Therefore, this work proposes a set of equations developed for calculating the apparent impedance seen by the distance relay in view of different types of short circuits, including the effects of power flow prior to the fault. These equations are then used to establish the distance primary protection zone settings. The analysis uses the mathematical expressions proposed of voltages and currents at the relay location, and the impedance diagrams obtained from simulated short circuits. Subsequently, the settings obtained with these equations are compared to those achieved using the IEC 60909‐0 standard, allowing for the differences in settings and their effectiveness. Finally, this procedure is applied to a part of the Ecuadorian Transmission System.

Performance enhancement of distance relay in presence of unified power flow controller

The characteristics of the distance relay are devised based on online and fault impedance. The relay uses fault information to react to the expected state; however, integrating the grid with a unified power flow controller (UPFC) might stop the relay from fault-triggered operations, requiring altered relay characteristics. Building relay tripping parameters are among the critical challenges that must be addressed for transmission line distance relays because current transmission networks face higher stress regarding power system operation. Furthermore, the use of flexible AC transmission systems (FACTS) instruments at the transmission level adversely affects distance relay performance due to impedance differences. The UPFC is among the essential FACTS instruments; it comprises shunt and series converters to alter the apparent relay impedance; hence, it was considered for this study, where a test system during fault was assessed to demonstrate the output of the distance relay before and after using the UPFC. MATLAB was used to build scenarios demonstrating the effect of a UPFC located in the transmission line's midsection or end or not using the UPFC. This research offers an analytical technique to determine the probable effects of UPFC on distance relay characteristics. The outcomes provide new relay characteristics for several fault resistances and locations for fault-specific impedance trajectory reactions.

Effects of Conditional Changes on High-Voltage Direct Current Transmission Line Characteristic

The high-voltage direct current (HVDC) transmission system, which links the Gurun Substation of the National Electric Authority of Malaysia (Tenaga Nasional Berhad, TNB) with the Khlong Ngae Station of the Electricity Generating Authority of Thailand (EGAT), has been extensively researched to achieve the highest quality because it is the largest of its kind in Thailand, and there is a plant to expand its transmission power. However, the impact on the whole system is under-researched. To study and develop this system, the HVDC transmission line is modelled with the MATLAB/Simulink program and a laboratory setup to investigate the effect of transmission line distance, load power, and voltage on power loss, voltage drop, and waveform. The HVDC transmission line parameters are calculated from the actual transmission line parameters and converted to the simulation model parameters using the per-unit method. The model is verified and tested by the simulation program before creating the experimental setup. The simulation and experimental results demonstrate the effects of changing system conditions via the three aspects. All the three conditions directly affect the HVDC transmission line; nevertheless, they affect each aspect differently.

An Algorithm to Mitigate the Infeed Effect on Overreaching Distance Zones Settings

This paper revisits the analysis of the well-known infeed effect on transmission lines distance protection. A new adaptive algorithm to overcome this drawback is proposed, which requires solely impedance data and the operational status of power apparatus to perform overreaching distance zones settings. A comparison of the proposed strategy and the traditional one is performed. The obtained results demonstrate that the proposed settings ensure the correct operation of overreaching zones. Thereby, the backup coverage is improved significantly, besides avoiding distance zones overlapping between adjacent lines. It reveals the proposed strategy usefulness and value from the practical point of view, since it can be implemented with technology readily available on the market.

Transmission Line Distance Protection Algorithm Based on Bayesian Inference

This paper presents a distance protection method based on estimating the resistances and inductances seen by the relay using a least-squares (LS) approach combined with the application of Bayesian inference (BI) to determine fault probabilities in the protected zone over time. The use of BI in the presented algorithm increases the security and reliability of the LS-based line protection approach, which, although fast, may yield impedance estimates with numerical inaccuracies and therefore configures a solution capable of detecting faults internal to the protected zone rapidly and dependably. The authors tested the proposed algorithm using data sets obtained from transmission line fault simulations performed in Alternative Transients Program (ATP), which considered noisy measurements, current transformer (CT) saturation, capacitive-coupling voltage transformer (CCVT) transients, switching onto fault, close-in faults, frequency variations, uncertainties in the line’s parameters, and power swings. Furthermore, the authors tested the presented method against measurements recorded by field protection equipment during seventy-nine actual fault events on four existing 500 [kV] lines. The results indicate that the proposed algorithm is a fast, secure, and reliable distance protection solution and that using BI to the LS-based distance protection approach increases security while maintaining fast fault detection.

Transmission line distance measurement with millimeter wave radar based on improved robust Kalman filter

Abstract In this paper, a millimeter wave radar ranging algorithm based on improved robust Kalman filter is proposed. In order to solve the problems of multi-point return of radar, unstable output and susceptible to environmental influences in the real-time monitoring of transmission line anti-mechanical collision line. Firstly, the effective target distance minimum extraction algorithm based on time domain is used to filter out the outliers. Next, the continuous output data is subjected to robust Kalman filter to realize data smoothing, so as to improve the anti-coarse interference capability of the system. Finally, static and dynamic experiments were conducted to simulate different mobile states of construction vehicles. The experimental results show that accuracy of distance measurement of our algorithm is about ±0.1m, and the ranging error is 2%, which can meet the overall demand for real-time monitoring of transmission line anti-mechanical collision line.

Optimization of minimum crossing distance of transmission line based on multi objective ant colony algorithm

In the test of cross span distance of transmission line, the estimation of cross span distance is not accurate, which leads to the increase of subsequent test error. Therefore, a test method of transmission line cross span distance based on a multi-objective ant colony algorithm is proposed. Statistics of the actual information of different crossovers including trees and forest areas. Considering the transmission line as a flexible cable, the objective function for estimating the cross span distance of the transmission line is constructed according to the catenary model of the flexible cable model. On this basis, the multi-objective ant colony algorithm is used to solve the function, and the optimization results of transmission line crossing distance are output. The experimental results show that the method has high accuracy, small error, short time and reliability.

대용량 부유식 해상풍력발전단지의 연계선로 거리에 따른 경제성 분석

In this study, economic evaluation of large-scale floating offshore wind farms(OWF) is conducted. The floating wind turbine is not limited by water depth, so it can be installed in the sea far from the coast, and also expected to increase the productivity of electricity energy due to higher mean wind speed. As the cost of the project increases as the distance to shore increases and the capacity of the power generation complex increases. However, as the distance to shore increases and the capacity of the offshore wind farm increases, the project cost will be increased. Therefore this research is needed to confirm whether it is economically sustainable. The case models to be evaluated are a 400㎿ and 480㎿ wind farm. The cost model is composed of the installation and operating cost of the floating offshore wind farm. In particular, the electricity production and income are calculated by applying the wind speed model according to the transmission line distance and the electricity energy price according to the renewable energy certificate(REC) weight. Economic analysis is evaluated on annual energy production(AEP), net present value(NPV), cost-benefit ratio(B/C ratio), and levelized cost of energy(LCOE).

Low Frequency Oscillations in a Hydroelectric Generating System to the Variability of Wind and Solar Power

The penetration of multiple integrated renewable energies to the power grid are relevant for decision making in energy policy, environment and business. Such an electricity penetration is affected by the intermittent and volatile characteristics of integrated energies, mostly significantly related to the safe and stable electricity production and supply in real world. Here, this paper focuses on the low frequency oscillation analysis of the hydropower generation response to the wind and solar variability. To enable this analysis, a hybrid model of hydropower system integrating with the wind and solar power system is presented. The Nyquist and root-locus stability methods are used to investigate the sensitivity performance of the hydropower governor to the fluctuation of the integrated renewable energies. Additionally, to quantify the risk of the hybrid system, the low frequency oscillation response of hydropower system to wind/solar/hydropower quota and transmission line distance ratio is extensively investigated in this study. The results show that under the case of the wind, solar and hydropower ratio is 40:1:150, the optimal values for maximally reducing hydropower low frequency oscillation are finally determined as kp = 0.8, ki = 0.25 and kd = 0.5. Regarding a certain wind/solar/hydropower quota, it is a promising strategy to increase the solar-load transmission line in order to achieve the safe and stable operation of the hybrid system and a relatively excellent dynamic regulation capacity of the hydropower governor. The model, methods and results implemented in this study are exploited to markedly improve new knowledge applications, policy management, low carbon emissions and investment competitiveness of future energy systems.

Research on induced current and induced voltage of 500 kV double circuit transmission line

Due to the loop distance of double circuit transmission line on the same tower is small, the electromagnetic coupling and electrostatic coupling between the power failure line and the running line are greatly enhanced, and higher induced current and induced voltage are generated on the power failure line. At the same time, the line is erected without transposition, the line’s three-phase parameter is asymmetrical, and the induced current and induced voltage show obviously phase separation characteristics. The paper apply transient simulation software EMTP to simulate the induced current and induced voltage under different line lengths, transmission power flow and phase sequence arrangement, which provides a reference for the design, planning and operation of 500 kV double lines on the same tower in the regional power grid.

Transmission Line Distance Protection Under Current Transformer Saturation

Conventional transmission line distance protection approaches are subject to malfunction under reverse fault-induced current transformer (CT) saturation for the typically employed breaker-and-a-half configuration. This paper addresses this issue by proposing a new distance protection approach that combines the blocking and unblocking criteria of distance protection based on the values of incomplete differential current, operation voltage, and current harmonic content. The proposed approach is verified by theoretical analysis, dynamic simulation testing, and field operation to ensure that the obtained distance protection is reliable and refrains from operating unnecessarily under reverse fault-induced CT saturation in the breaker-and-a-half configuration. Meanwhile, the proposed approach is demonstrated can operate reliably when forward faults occur or various reverse faults are converted to forward faults.

Cost-optimal evaluation of centralized and distributed microgrid topologies considering voltage constraints

Optimal design of hybrid renewable mini-grids requires both economic and power quality considerations. Existing modeling approaches address these considerations via separate or loosely coupled models. Here, we extend REopt—a techno-economic optimization model developed at the National Renewable Energy Laboratory—to consider both within a single model. REopt formulates the design problem as a mixed-integer linear program that solves for a site's optimal technology mix, sizing, and operation to minimize life cycle cost. REopt has traditionally assumed a single node system. In the work presented here, we expand the REopt platform to consider multiple connected nodes with associated voltage constraints. In order to do this, we model power flow using a fixed-point linear approximation method. We then use the model to explore design considerations of mini-grids in Sub-Saharan Africa. Specifically, we evaluate under what combinations of transmission line distance and capacity it is technically viable and economically preferable to build multiple isolated mini-grids versus an interconnected, centralized system.

Traveling Wave-Based Transmission Line Earth Fault Distance Protection

This paper proposes a one-terminal traveling wave (TW)-based transmission line earth fault distance protection function. It only needs the detection of the first incident modal earth fault-induced TWs, so that, the challenging detection of wavefronts reflected from the fault point is not required. Both the sampling frequency effect and inaccuracies on the wave propagation velocity are considered in order to define the distance protection zone. Simulated fault records were played back in an actual relay, allowing the comparison between a commercially existing time-domain distance protection element and the proposed one. The proposed function is more accurate and significantly reduces transmission line distance protection tripping times without dependability losses.

Mal-Operation of Mho Relay In Transmission Line Due To Presence of TCSC

Distance protection is simple and it provides fast response to clear the fault. Distance protection is also providing primary and remote backup function depending upon distance of transmission line. Distance protection uses various relays like mho relay/admittance relay, impedance relay and reactance relay. In power transmission system, Flexible AC Transmission System (FACTS) controllers are used to increase power transfer capability and reactive power control, but distance relay get affected due to presence of FACTS devices. This may create the stability issues, security and it may affect on voltage profile. The changes in impedance level would affect the accuracy of distance protection. This paper represents the effect of TCSC on operation of mho relay in transmission line. The work presented here emphasis on the interaction of TCSC on distance protection and their performances under different condition i.e., load angle variation, variation of SCL, different fault location. Design and control performance of MHO relay during normal operation as well as during variation in different condition is verified by using PSCAD simulation software.

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.

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.