Intrinsic time decomposition based fault location scheme for unified power flow controller compensated transmission line

In the presence of nonlinear response created by power electronics-based compensators, reliable fault detection and classification by distance protection relays is a major concern. The unified power flow controller (UPFC) has a dynamic characteristics that causes stability and protection issues. A intrinsic time decomposition (ITD) based strategy is proposed for addressing this issue. A differential energy based detection index computed using ITD and adaptive thresholding technique is employed such that unerring fault detection is achieved wherein faulty phases of a UPFC compensated transmission line are well pointed out. Various fault and non-fault cases considering critical power system conditions are analysed for power systems with varying configurations modelled using EMTDC/PSCAD. A comparison of the current detection method to recently proposed techniques reveals the benefits and feasibility of the presented detection strategy, which has been proved to be accurate and efficient.

In this paper, a fault detection and faulty phase selection of a two generator two bus system with unified power-flow controller (UPFC) is studied extensively by generating the data in EMTDC/PSCAD environment. Distance relaying of transmission line having UPFC is a very challenging task. Different fault cases are simulated by placing the UPFC at the sending end of a 230kV transmission line in two generator two bus system. A one cycle three-phase current data are collected at 1 kHz sampling rate for detection and classification of different faults by moving sum based technique. The results presents the proposed technique of frequency domain analysis possesses very fast and accurate protection for UPFC based power transmission lines.

New smart fault locator in compensated line with UPFC

This paper addresses two issues in operation of a unified power flow controller (UPFC), enhancement of fault recovery and controller design accounting for filter dynamics. Performance of a UPFC is improved by a temporary modification of the UPFC into double static synchronous series compensator (SSSC) in order to double its capability in fault recovery mode. A battery is required as an energy source in the DC link of the double SSSC. The size of the battery for the SSSC has been be investigated. It was found that the double SSSC in fault recovery mode has almost twice the performance of the UPFC and the size of battery for the UPFC is reasonable for grid scale use. With the double SSSC in fault recovery mode, a combination control mode is suggested for the UPFC. One of the important parts of the UPFC is the filter at the output of the inverter. The function of the UPFC filter is to attenuate the harmonics generated by the inverter. In this paper a harmonic trap filter together with a low-pass filter are applied to the UPFC and investigated. Single-phase models are used to design cut-off frequencies whilst the d-q model is included in the UPFC controller design. It was found that if the filter dynamics are neglected in the control design, then the controllers response will be different. The test system used is a one-machine, two transmissions lines and an infinite busbar. All of the simulations were implemented using the EMTP. Additionally Matlab and Simulink programming environment were used to provide transfer function simulation for the controller design. The simulation results from both programs are compared.

This study presents a new fault location algorithm for a transmission line operating with a unified power flow controller (UPFC). The proposed algorithm is based on a new matrix version of the conventional S‐transform called sparse S‐transform (SST), using selected frequency components to increase the speed of the computation significantly. A variety of faults are initiated before and after the location of UPFC on the transmission line using MATLAB/SIMULINK platform. Further, the impedance trajectories and fault location are estimated using SST with significant accuracies. The computational speed of the SST is almost 30 times faster than the conventional discrete S‐transform which makes it a suitable candidate for real‐time application in digital relaying.

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.

This paper presents a screening technique for greatly reducing the computation involved in determining the optimal location of a unified power flow controller (UPFC) in a power system. The first-order sensitivities of the generation cost with respect to UPFC control parameters are derived. This technique requires running only one optimal power flow (OPF) to obtain UPFC sensitivities for all possible transmission lines. To implement a sensitivity-based screening technique for guidance in optimally locating a single UPFC in a power system, we propose a new UPFC model, which consists of an ideal transformer with a complex turns ratio and a variable shunt admittance. In this model, the UPFC control variables do not depend explicitly on UPFC input and output currents and voltages. Accordingly, this model does not require adding extra buses for UPFC input and output terminals. IEEE five-, 14- and 30-bus systems were used to illustrate the technique

Author response for "Intrinsic time decomposition based fault location scheme for <scp>unified power flow controller</scp> compensated transmission line"

A fast time–frequency transform based differential relaying scheme for UPFC based double-circuit transmission line

– The unified power flow controller (UPFC) is the most versatile and complex power electronic equipment that has emerged as the indispensable equipment for the control and optimization of power flow in electrical power transmission system. In this manuscript is investigated the control of real and reactive power flow through a transmission line with the use of UPFC at the sending end. Computer simulation using MATLAB Simulink is done and the behavior of the UPFC is studied. In the UPFC based control of transmission line parameter control systems, it is observed that whenever the SSSC sources some real power into the transmission line it is manifested as a voltage drop across the DC link. Reactive power demand is indicated as fall in the bus bar AC voltage. The fall of the DC link voltage is an indication of real power demand from the receiving end. Similarly a fall of the bus bar AC voltage is an indication of reactive power demand from the receiving end. Fuzzy Logic and PI controllers are used in this works, the control of DC voltage, AC voltage and power transfer.

Due to ever-increasing power demand, the power system is facing issues such as congestion, line outages, system reliability, and stability challenges. The impetus to revise the traditional power transmission theory and practice, and to introduce new concepts for improving the performance of the existing AC transmission system caused the development of flexible AC transmission system controllers (FACTs). Due to their capability of controlling transmission system parameters, the utilization of FACTs controllers has become essential to enhance the power system capability. To investigate the performance of FACTs controllers, this study incorporates the Unified Power Flow Controller (UPFC) in the power system. UPFC is used to mitigate transmission line congestion by controlling the transmission line power flow. In this paper, a modified control circuit for UPFC is implemented. Moreover, the selection of a suitable location for UPFC is necessary because of its techno-economic impacts. Therefore, this work uses a sensitivity-based approach for the selection of a suitable place of UPFC. To decide the suitable location, control parameters of UPFC along with system loss sensitivity indices are used. The model of UPFC along with the control circuit is simulated in PSCAD/EMTDC. To investigate the performance of UPFC, a five bus seven-line transmission system is used. After installing the UPFC at an appropriate location, the power flow results of transmission lines are compared with and without the usage of UPFC.

ABSTRACTFaults in power transmission systems pose significant challenges due to the complexity and length of transmission lines. Effective fault detection, classification and location are essential for preventing further damage to the power grid. While travelling wave‐based algorithms are commonly used for fault location, they often focus on identifying the fault's location without classifying the fault type. Accurate classification is crucial for enabling efficient and timely responses from protection systems. This paper introduces an integrated model for fault detection, classification and location using voltage signals from a single terminal of a series‐compensated transmission line with a static synchronous series compensator (SSSC). The Gabor Transform (GT) is utilised for feature extraction, enabling both fault detection and classification. Travelling wave theory is then applied to identify the faulty segment and estimate the fault location. Additionally, a novel technique adaptively calculates the threshold value during the protection algorithm's execution. The proposed method is validated through a comprehensive analysis of various fault scenarios and sensitivity analysis. Numerical simulations in MATLAB/Simulink show that the model achieves 100% accuracy for fault detection, classification, and faulty segment identification, with 99.7925% accuracy for fault location estimation, demonstrating its effectiveness in fault management.

Feature extraction of rolling bearing multiple faults based on correlation coefficient and Hjorth parameter

This paper proposes a parameter modification based transmission line fault location algorithm using single-ended current, which requires less information than the method with two-ended current and avoids the effects of TA saturation or break. At the same time, considering the impacts of dynamic conditions on the parameters of transmission line, such as power oscillation , Parameter Modification Fault Locator(PMFL) based on Phasor Measurements is presented. Simulations with the help of PSCAD/EMTDC are done and the results allow us to make a conclusion that the proposed method has an effective performance on fault location at the cost of minor computation increase.

In this paper, analytical and simulation results are carried out about the application of distance protection with the presence of the unified power flow controller (UPFC) in the AC system. Combined with the UPFC protection, the impact of UPFC on distance protection is analyzed under different operation conditions. The influence to the distance protection is bigger when the series unit remains in the system after fault occurs. The simulation results show the impact of UPFC on protection for different operation conditions and different fault locations.