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A fault properties identification scheme for a hybrid multi‐terminal DC (MTDC) system is proposed to improve the power supply reliability in the system recovery stage. Firstly, a current signal injection strategy based on line commutated converter (LCC) is proposed using the fault control capability. Secondly, the difference between the calculated value (CV) and the measured value (MV) of the current signal under permanent and temporary faults is analyzed for the distributed parameter line model. By introducing the dynamic time warping (DWT) algorithm to represent the difference between CV and MV, a fault properties identification scheme for permanent fault identification is constructed. Finally, the proposed scheme for permanent fault location with the distributed parameter model is obtained by introducing the trust region reflection (TRR) algorithm. The simulation results show that the proposed fault properties identification scheme has the function of permanent fault identification and location. The proposed scheme fully considers the effects of fault impedance, sampling rate, noise, and data loss. It can be applied to high voltage DC long‐distance transmission lines with LCC. [ABSTRACT FROM AUTHOR]

Hybrid HVDC consisting of line commutated converter (LCC) on rectifier side and modular multilevel converter (MMC) on inverter side is the favourable future trend of HVDC projects utilising the advantages of both converter technologies. However, fault clearing and adaptive restart capabilities of such hybrid HVDC are not much investigated in the literature. In this paper fault clearing of hybrid HVDC transmission line is investigated using mechanical DC breaker at MMC terminal and forced firing angle retardation at LCC terminal. Then, the characteristics of the line voltages are analysed during the fault blocking states of converters to clear the transient fault. Characteristics of the line voltages of LLC rectifier have shown prominent difference under permanent and temporary fault states, and also dependent on the severity of fault. Therefore, based on line voltage characteristics, a restart strategy is proposed for hybrid HVDC which is adaptive to the fault characteristics. Several PSCAD/EMTDC based simulation studies are conducted to validate the proposed fault recovery strategy. Simulation results validate the effectiveness of the proposed strategy for hybrid HVDC under DC line faults. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the feasibility of smart metering system based on narrowband power line communications (NB‐PLC) by using low‐voltage (LV) and medium‐voltage (MV) power line channels. The LV and MV networks of two different sites are selected to carry out comprehensive field measurements to investigate the characteristics of NB‐PLC channels for narrowband frequencies. The NB‐PLC channels of both sites are classified into two categories, that is, bad and good channels of LV and MV networks by considering their characteristics and performance. On the basis of measured results, the simulation models for the modeling of LV and MV NB‐PLC channels are developed and thus proposed. The measured and simulated results are compared to validate the efficiency of proposed methods. A state of the art mechanism for the modelling of capacitative coupling device and impedances of LV and MV networks is developed. It is proposed that simulation‐based NB‐PLC channel models and analyses can play a vital role in examining the residential and industrial types of channels. This research work will pave the way to standardize the future smart metering equipment and sensing devices of power system protection. [ABSTRACT FROM AUTHOR]

This study investigates the feasibility of advanced metering infrastructure (AMI) based on narrowband power line communications (NB-PLC) by incorporating all possible types of low voltage (LV) and medium voltage (MV) power line channels. The extensive field measurements are carried out on six selected sites that include residential, commercial, and industrial LV and MV NB-PLC channels. On the basis of measured results, NB-PLC channels of various under evaluation sites are segregated into two classes i.e. worst and good channels for both LV and MV networks. The simulation models for the modelling of LV and MV NB-PLC channels by considering the practical data of measured sites are developed and thus proposed. The proposed methods are validated by comparing the measured and simulated results. A sophisticated mechanism for the modelling of LV and MV network impedances and capacitive coupling device is formulated. The proposed analyses and simulation-based NB-PLC channel models can play a key role in examining the characteristics of various types of NB-PLC channels. This research work will help to standardise the future smart metering equipment and sensing devices of power system protection. [ABSTRACT FROM AUTHOR]

One of the leading causes of power system outages is lightning surges. A precise calculation of lightning overvoltages across insulators has vital significance for the investigation of lightning outages. This study investigates the impact of different lightning surges for the analysis of transient frequency characteristics of line commutated converter (LCC) based $\pm $± 800 kV ultra-high-voltage direct current (UHVDC) converter station by developing a wideband (WB) model of the converter station. The influence of lightning flashover criterion (LFC) of double exponential and Heidler surges methods on insulator/gap for precise lightning withstand level is examined. An analytical comparison for LFC of insulator/gap installed at high altitude transmission lines by incorporating the IEEE volt/time curve, CIGRE leader propagation (LP) and improved LP methods is presented. The proposed WB model explores the novel attributes of high-frequency transfer characteristics and the coupling mechanism of transient frequencies passing through the converter station. Moreover, the effect of internal frequency dependant DC line faults on the WB model is examined. The analysis presented here aims to investigate issues like overvoltage, electromagnetic disturbance prediction, insulation design of the equipment and standardisation of sensitivity issues that are being faced by the present relay protection systems. [ABSTRACT FROM AUTHOR]

High voltage dc (HVDC) transmission, especially voltage source converter (VSC)-based HVDC transmission requires high-speed operation for relay protection. However, traditional derivative-based non-unit travelling wave-based protection (TWP) methods are sensitive to the fault impedance, resulting in low protection sensitivity in case of the high-impedance fault. First, the fault information containing in the fault travelling wavefront is analysed based on the frequency-dependent parameters of the dc transmission line and the broadband characteristic of the fault-point initial travelling wave. It can be concluded that the distortion of the fault travelling wavefront depends on the fault distance and the amplitude of the fault travelling wavefront depends on the fault impedance. Then, a principle of non-unit TWP for dc transmission line based on waveform correlation calculation is proposed. The proposed method is verified in both thyristor-based HVDC and VSC HVDC PSCAD test systems. The simulation results verify the high-speed, high fault-impedance tolerability and correctness of the proposed protection method. [ABSTRACT FROM AUTHOR]

This study presents a single-ended fault location method that does not need the information of the remote-end system. As the foundation of the proposed method, the fault location equations under different fault types are derived based on the fault loops. The fault distance, fault impedance, and equivalent resistance and inductance of the remote-end system are considered as the unknowns of the fault location equation. Then the equation can be solved using the Gauss-Newton method, by which the four unknowns can be obtained. Therefore, the proposed method is not sensitive to the fault impedance and the system parameters. A two-terminal 500 kV ac transmission line test system is built in PSCAD to verify the proposed method. Numerous simulation data of faults of different fault distances, fault impedances, and fault types verify the accuracy and robustness of the proposed method. The proposed method is a time-domain method that can locate the fault using 5 ms data after the faults. [ABSTRACT FROM AUTHOR]

Modular multilevel converter (MMC) is widely used in hybrid AC/DC power transmission system. Strong control capability of MMC provides a new way of the adaptive autoreclosing scheme in such systems to enhance the power supply reliability and system stability. A novel fault identification method is proposed in this study. It is based on characteristic signal injection utilising the control strategy of MMC and line coupling features. A characteristic signal from MMC can be injected to healthy lines which in turn induce characteristic signal to the faulty phase/line. Induced signals have different performances under normal or fault conditions. The proposed method is independent of electrical characteristics of recovery voltage and secondary arc, and multiple independent injections could be implemented. Finally, the adaptive autoreclosing scheme based on injection method is proposed. Simulation studies are carried out under the single line to ground and symmetrical faults, which strongly verify the effectiveness of the proposed scheme. [ABSTRACT FROM AUTHOR]

The authors proposed a faulty feeder detection method based on the combination of feature extraction and information entropy in the distribution network. Firstly, analysed the characteristics of a transient zero-sequence current (TZSC) waveform, and constructed a mixed atom dictionary by a cosine packet and a wavelet, and then, the authors adopted the matching pursuit algorithm to extract characteristic atoms of each feeder. For energy aspects, used energy spectrum entropy (ESE) to measure; for the waveform similarity, calculated correlation coefficient between characteristic atoms and the original TZSC, then, the authors obtained the ESE of modified atoms and integrated atoms, respectively. In a faulty feeder detection criterion, calculated the difference value between the maximum and the minimum of integrated atoms ESE, and compared the value and the threshold. If the value is smaller than the threshold, the bus is judged as a faulty feeder, otherwise, the maximum corresponding to the feeder is judged as the faulty feeder. Simulation and field tests show that the method can accurately judge the faulty feeder, and its accuracy is immune to transition resistance, iteration numbers, data window length, different compensation degrees, capacitor switching, and unbalanced load. [ABSTRACT FROM AUTHOR]