Lightning Disturbance Research Articles

Study on fault mechanism of LCC HVDC large disturbances under cloud-to-ground lightning with long continuous current

The safe and stable operation of the line commutated converter high voltage direct current (LCCHVDC) system is of great significance to the reliability of electricity supply. In order to clearly reveal the mechanism of LCCHVDC large disturbance fault under the Cloud-to-Ground (C-G) lightning with long continuous current, the HVDC-lightning simulation model considering long continuous current, actual control and protection systems is proposed. The effect of long continuous current on traveling wave protection is analyzed. Transient processes including commutation failure (CF), fault restart and blocking of the DC system under the lighting with long continuous current are simulated. The reasons for CF of LCCHVDC system caused by long continuous current are analyzed, and the influence of long continuous current amplitude and duration on fault restart process is studied. Results show that the long continuous current has little influence on the response characteristics of travelling wave protection, but during the regulation process of control system under lightning disturbance, the DC current control regulation quantity will increase due to the presence of long continuous current. If the amplitude of long continuous current exceeds 80 A, the CF will occur in the DC system. If the duration of long continuous current exceeds the deionization time, the line will fail to restart, and the line can be successfully restarted only if the long continuous current is over before the voltage begins to rise.

A novel identification method of lightning strokes for hvdc transmission lines based on voltage deviation

Reliable protections are the guarantee of the safe and stable operation of HVDC system. In order to avoid the mal-operation of the transmission line protection in HVDC system due to the lightning stroke disturbance, this paper studies the different characteristics of lightning disturbance and fault, and proposes a voltage deviation based lightning stroke identification method. The voltage deviation of positive pole is utilised to distinguish lightning disturbance from lightning fault, and the voltage deviation of negative pole is utilised to identify the fault type. Extensive simulation results show that the proposed lightning stroke identification method can distinguish disturbances form faults and judge the fault type correctly.

A Novel Identification Scheme of Lightning Disturbance in HVDC Transmission Lines Based on CEEMD-HHT

For high-voltage direct current (HVDC) transmission systems that use overhead transmission lines, the lightning disturbance is the main reason for the line protection mal-operation. To avoid the impact of lightning disturbance on the safety and stability of DC line protection, the model of HVDC transmission system including lightning strokes is constructed. On this basis, the complementary ensemble empirical mode decomposition (CEEMD) and Hilbert transform are combined as a time-frequency analysis method to calculate the energy distribution of the signals. Then the low-to-high-frequency energy ratio of the 1-mode voltage signal in a 3 ms data window after the protection startup is used as the protection criterion for identifying lightning disturbance, and that of the current signal in 1 ms is used as the criterion to further distinguish lightning and non-lightning faults. Verified through simulation tests, the scheme appears good adaptability and accuracy in different situations.

Analysis of lightning disturbance at 150 kV high voltage power lines

The power transmission line channels electrical energy from power plants to consumers through diverse natural conditions. East Java is an area with a unique topography, where clouds causing rain and lightning are frequently formed. Such clouds strongly interfere with the 500 kV Extra High Voltage Line (SUTET), causing a lightning strikes. Therefore, the lightning strikes along the channel needed to be analyzed. The random method used in this research measured the lightning safety at the tower, within a quarter of the distance from the tower and half the distance from the tower (Lightning disturbance due to back flashover) Based on the calculation, the highest number of disturbances in the phase wire per 100 km2 of conductor per year has obtained and (SFO) was 1.073399.10-3. while tower impedance has found at 273.6219 Ohms.

An Auxiliary Fault Identification Strategy of Flexible HVDC Grid Based on Convolutional Neural Network With Branch Structures

Lightning disturbance may be misjudged as dc fault by the primary protection in the flexible high voltage dc (HVDC) grid. To solve this problem, an auxiliary fault identification strategy based on convolutional neural network with branch structures (BR-CNN) is proposed in this paper. In the proposed scheme, the voltage and current characteristic matrix is constructed as the input matrix of BR-CNN model and the output categories include positive pole-to-ground (PTG) fault and lightning disturbance. Voltage and current branches are constructed to extract high-level local features of input data layer by layer, and main branch is designed to realize the comprehensive utilization of voltage and current information. Through autonomous learning of the model, the nonlinear mapping relationship between input and output is constructed. The method only uses the single-terminal quantities, and can be used as an auxiliary criterion to improve the reliability of the primary protection. The test results verify the effectiveness of the method, and the recognition accuracy is better than the traditional classification models.

A Pilot Protection for HVDC Transmission Lines Based on Transient Energy Ratio of DC Filter Link

To overcome shortages in the traditional current differential protection for HVDC transmission lines, a pilot protection based on transient energy ratio is proposed. The fault identification criterion is put forward based on the impedance-frequency characteristic of the line boundary, and the fault analysis which shows that under internal faults, with regard to either terminal of the dc line, the transient energy within a specific frequency band on the line side of the boundary is much greater than that on the valve side of the boundary, whereas after rectifier-terminal (inverter-terminal) external faults, the transient energy on the line side of the rectifier-terminal (inverter-terminal) boundary is much less than that on the valve side of the boundary. Moreover, the lightning disturbance identification criterion is implemented based on the magnitude ratio of fault components of high- and low-frequency band currents. Fault-pole selection is constructed by using the fault components of pole voltages. Simulation results demonstrate that the proposed scheme, with low computational complexity, can distinguish internal faults from external ones and protect the entire line reliably. It can also identify high-impedance faults and select the faulted pole correctly. Besides, it is not subject to lightning interferences and the dc line distributed capacitor.

Entropy SVM-Based Recognition of Transient Surges in HVDC Transmissions.

Protection based on transient information is the primary protection of high voltage direct current (HVDC) transmission systems. As a major part of protection function, accurate identification of transient surges is quite crucial to ensure the performance and accuracy of protection algorithms. Recognition of transient surges in an HVDC system faces two challenges: signal distortion and small number of samples. Entropy, which is stable in representing frequency distribution features, and support vector machine (SVM), which is good at dealing with samples with limited numbers, are adopted and combined in this paper to solve the transient recognition problems. Three commonly detected transient surges—single-pole-to-ground fault (GF), lightning fault (LF), and lightning disturbance (LD)—are simulated in various scenarios and recognized with the proposed method. The proposed method is proved to be effective in both feature extraction and type classification and shows great potential in protection applications.

A Fast Non-Unit Protection Method Based on S-Transform for HVDC Line

To overcome the problems existing in the main protection of HVDC transmission lines, such as low reliability and poor ability of resisting high ground resistance fault, this paper proposes a novel non-unit protection method based on S transform. Analysis shows the high and low frequency components of the transient voltage signals suffer from different degrees of attenuation when they pass through the HVDC line boundary. Therefore, according to this characteristic, the voltage signals of specific frequency bands are extracted accurately using S transform, which be used to identify the internal from external faults. By comparing the high and low frequency components generated by the lightning disturbance with those generated by the faults, S transform based energy ratio criterion to identify lightning disturbance is constructed. In addition, for a bipolar HVDC transmission system, a method using the 0 Hz energy difference of S transform of the voltage transient signals is proposed to identify the faulted pole. Simulation results verify the feasibility and validity of the proposed protection method.

Novel transient-energy-based directional pilot protection method for HVDC line

This paper proposes a novel directional pilot protection method based on the transient energy for bipolar HVDC line. Supposing the positive direction of current is from DC bus to the DC line, in the case of an internal line fault, the transient energies detected on both sides of the line are all negative within a short time, which denotes the positive direction fault; while for an external fault, the transient energy on one end is positive, which means a negative direction fault, but the transient energy on the opposite end is negative, which indicates that the fault direction is positive. According to these characteristics, an integration criterion identifying fault direction is constructed. In addition, through setting a fixed energy threshold, the faulted line and lightning disturbance can also be discriminated. Simulation results from UHVDC transmission system show the validity of the proposed protection method.

Development of a Novel Protection Device for Bipolar HVDC Transmission Lines

A novel nonunit transient-based protection scheme for bipolar high-voltage direct current (HVDC) lines is proposed. The protection scheme is composed of a starting unit, a boundary unit, a directional unit, a faulty pole identification unit, and a lightning disturbance identification unit. The prototype based on the proposed scheme is developed and its performance is evaluated through a hardware-in-the-loop test using real-time digital simulator (RTDS) and real HVDC control devices. Better than the presently used line protection, the proposed protection not only can detect faults on HVDC lines more rapidly and accurately in different HVDC operation modes, but is also more effective in detecting high-impedance grounding faults. In addition, the novel protection is designed to identify lightning disturbances from short-circuit faults correctly, which avoids the unnecessary restart of HVDC systems due to protection misjudgment.

The UHVDC Transmission Line Lightning Disturbance Identification Based on the Morphology

Research and identify overhead transmission lines’ transient characteristic which was caused by lightning stroke is significant to develop the protection and improving its reliability based on transient state. A complex signal can be resolved into several parts which have respective physical meanings by mathematical morphology’s multi-scale decomposition and this can reveal the local features of waves. Therefore, the transient current of ±800 kV UHVDC transmission lines, caused by the non-fault lightning stroke, fault lightning stroke and other line short circuit, can be decomposed by the multi-scale morphology decomposition to extract the spectral energy from the high and the low frequency bands, and the ratio of those two spectrum energy forms main criterion to realize the identification between lightening disturbance and the fault states. According to the ratio of the maximum of the current’s amplitudes of decomposition waveform of the first head of current’s second scale and sixth scale, to further distinguish the lightning stroke fault from the line short circuit. Extensive simulations show that the approach is correct and effective.

Dynamic Lightning Protection of Smart Grid distribution system

With the integration of renewable resources, distributed generation (DG) and Microgrids, the Smart Grid distribution systems are more decentralized and interactive. As a System-level protection mode, the Dynamic Lightning Protection (DLP) focuses on the preventive actions for improving lightning performance of the whole system. In this paper, the DLP for Smart Grid distribution system is discussed. Taking advantage of the flexibility and interactivity of Smart Grid, the mode aims to maintain the system dynamic balance and minimize the lightning disturbance during the lightning storms. A dynamic hierarchical multilevel control model is also proposed in the paper, which could coordinate with a Dynamic Lightning Protection System (DLPS) to switch the control strategies, control the power exchange and improve the system reliability.

The Lightning Preventing Methods for 10kV Distribution Lines

The importance and necessity of the domestic and international distribution lightning direction and governance of the distribution line lightning damage are described, and the distribution line lightning protection assessment methods and procedures and how to choose the arrester combined with the actual situation are discussed. The lightning location system and counter combination is a means to test the merits of lightning protection components are deep-seated argued, and it will be an important part of future governance lightning disturbance of distribution lines. To prevent induction lightning damages is the main direction for distribution system is clarified through lightning damages prevention of 10kV Langshi line.

A Novel Bus Protection Based on Morphological Top-Bottom-Operator

A novel transient component bus protection based on morphological bop-bottom-operator is presented in this paper, which takes the max top-bottom-operator of current traveling wave to fast distinguish the bus internal fault from external fault. The method is based on the principle that the high frequency component of transient traveling wave caused by external fault will be attenuated by the bus capacitance but the traveling wave caused by bus internal fault changes slightly. Simulation is carried out with PSCAD/EMTDC, the result verifies the bus protection is reliable and accurate. The novel bus protection also can treat lightning failure or lightning disturbance happened on transmission lines as bus external fault, without malfunction. Introduction

Identification of Lightning Disturbance in UHVDC Transmission Lines Using Correlation Degree Based on Short Time Window Data

In this paper, the simulation of ±800kV UHVDC transmission line in which fault lightning stroke and non-fault lightning stroke, line short circuit occur shows: because there is fault current lumped parameter access to earth during the fault lightning stroke or ground fault, the voltage waveform decrease suddenly and cross repeatedly the zero line in 5ms time window；There is no fault current accessing to earth during non-fault lighting stroke, the disturbance caused by lightning is too less than value of the pole voltage. The voltage waveform comes from the protect position change up and down around the direct voltage line and decays to the pole voltage line in the 5ms time window at last. In the case of the fault lightning or ground fault non-lightning, the correlation degree of transient component and pole voltage line in the time window is little. On the contrary, it is large during the non-fault lighting. Above this, the correlation degree is calculated using 5ms samples. This kind of algorithm can resist random noise effectively,calculating speed is very fast. Many PSCAD simulations show that the algorithm can identify lighting disturbance correctly.

Study on The Novel Transient Bus Protection Based on Morphological Top-bottom-operator

A novel transient component bus protection based on mathematical morphology is presented in this paper, which takes the morphological max top-bottom- operator of current traveling wave to fast distinguish the bus internal fault from the external fault. The method is based on the principle that the high frequency component of transient traveling wave caused by bus external fault will be attenuated by the bus capacitance but the traveling wave caused by bus internal fault changes slightly. Simulation is carried out with the electromagnetic transient simulation software PSCAD/EMTDC, the result verifies the bus protection is reliable and accurate. The novel bus protection also can treat lightning failure or lightning disturbance happened on transmission lines as bus external fault, without malfunction.

Analysis of Simultaneous Line-to-Ground Faults

A CERTAIN PERCENTAGE of the faults on power systems occur simultaneously at different points in the circuits. Such faults may result from a ground at one location on a circuit which raises the voltage on a healthy phase so that a flashover occurs at a second location. Such faults may also occur on circuits which are physically close to each other, as two circuits on the same poles which flash over because of the same lightning disturbance. It has been estimated that up to 20% of faults on double-circuit lines involve conductors of both circuits.