scholarly journals An Optimized Coordination Strategy between Line Main Protection and Hybrid DC Breakers for VSC-Based DC Grids Using Overhead Transmission Lines

Energies ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1462 ◽  
Author(s):  
Zheng ◽  
Jia ◽  
Gong ◽  
Zhang ◽  
Pei
Keyword(s):  
Transmission Lines ◽  
Power Transmission ◽  
Short Circuit ◽  
Power Grids ◽  
Fault Line ◽  
Long Distance ◽  
Coordination Strategy ◽  
Overhead Transmission Lines ◽  
Depth Analysis ◽  
Dc Breaker

Compared with alternating current (AC) power grids, the voltage-sourced converter (VSC)-based direct current (DC) grid is a system characterized by “low damping”, as a result, once there is a short-circuit fault on the DC transmission line, the fault current will rise more sharply and the influence range will be much wider within the same time scale. Moreover the phenomenon that a local fault causes a whole power grid outage is more likely to occur. Overhead transmission lines (OHLs) have been regarded as the mainstream form of power transmission in future high-voltage, large-capacity and long-distance VSC-based DC grids. However, the application of overhead transmission lines will inevitably lead to a great increase in the probability of DC line failure. Therefore, research on how to isolate the DC fault line quickly is of great significance. Based on the technology route for fault line isolation using DC breakers, on the basis of in-depth analysis of traditional coordination strategy, an optimized coordination strategy between line main protection and a hybrid DC breaker for VSC-based DC grids using overhead transmission lines is proposed in this paper, which takes the start-up output signal of line main protection as the pre-operation instruction of the corresponding hybrid DC breaker. As a result, the risks of blockage of the modular multilevel converter (MMC) closer to the fault position and of damage to power electronic devices in main equipment can be reduced effectively. Finally, the proposed coordination strategy was verified and analyzed through simulation.

scholarly journals Reducing Short Circuit Level in 400 kV Iraqi Grid System by Using FACTS Device

2019 ◽  
pp. 90-99
Keyword(s):  
Power Systems ◽  
Transmission Lines ◽  
Power Transmission ◽  
Short Circuit ◽  
Electrical Power ◽  
Short Circuit Current ◽  
Power Grids ◽  
Power Transmission Lines ◽  
Power Stations ◽  
Flexible Alternating Current Transmission

Electrical power systems are different in their sizes because of their amount of generation power stations, substations, transmission lines and loads. Therefore, these factors may impact on short circuit levels values. Capacity of power stations and dummy transmission lines in Extra high voltage grid (400kV) of the Iraqi Electrical power grids cause high short circuit levels values such that exceed both rating of the peak and breaking capacity of switchgear equipment's. Reduction of short-circuit levels by using Fast-acting Flexible Alternating Current Transmission Systems (FACTS) types devices in power grids maintain the operation of power grids with acceptable value of short circuit levels for their electrical equipment's and preventing cascading event outages which may lead to blackouts. This paper mainly studies strategies on how to add Short Circuit Current Limiter (SCCL) device by determining its number, value and location of connection in power grids by programing with (PSS™E version 30.3 Package Program). IEEE 25-bus system is used for testing the adding series SCCL at power transmission lines method procedure. The results of adding series SCCL with power transmission lines give significant reducing short circuit levels for the stations have highest short circuit levels in order to prevent the blackouts of overall power grid.

scholarly journals Research on the decision of state maintenance for transmission line based on set pair analysis

2021 ◽  
Vol 71 (1&2) ◽  
pp. 17
Author(s):  
Shiyang Zhu ◽  
Le Wang
Keyword(s):  
Power System ◽  
Transmission Line ◽  
Transmission Lines ◽  
Power Grids ◽  
Financial Control ◽  
Set Pair Analysis ◽  
Overhead Transmission Lines ◽  
Maintenance Work ◽  
Maintenance Decision ◽  
Pair Analysis

Overhead transmission lines are important parts of a power system; their operation state directly affects the reliability level of the entire power system. With the in-depth development of state maintenance work for power grids, correctly evaluating the reliability of overhead transmission lines is the key to successful maintenance. A maintenance decision model for transmission lines is established in this study based on set pair analysis to achieve human financial control and low maintenance efficiency. Full consideration is provided to the influence of environmental factors, and a theoretical basis for transmission line maintenance decision is established.

scholarly journals A Study for the Measurement of the Minimum Clearance Distance between the 500 kV DC Transmission Line and Vegetation

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2606
Author(s):  
Kumail Kharal ◽  
Chang-Hwan Kim ◽  
Chulwon Park ◽  
Jae-Hyun Lee ◽  
Chang-Gi Park ◽  
...  
Keyword(s):  
High Voltage ◽  
Transmission Lines ◽  
Power Transmission ◽  
Electrical Power ◽  
Long Distance ◽  
Dc Voltage ◽  
Hvdc Transmission ◽  
High Voltage Direct Current ◽  
Dc Line ◽  
Pass Through

High voltage direct current (HVDC) transmission is being widely implemented for long-distance electrical power transmission due to its specific benefits over high voltage alternating current (HVAC) transmission. Most transmission lines pass through forests. Around the HVDC lines, an arc to a nearby tree may be produced. Thus, there should be a minimum possible clearance distance between a live conductor and a nearby tree, named the minimum vegetation clearance distance (MVCD), to avoid short-circuiting. Measurement of minimum clearance distance between the conductor and trees is a significant challenge for a transmission system. In the case of HVAC transmission, a large amount of research has been undertaken in the form of the Gallet equation for the measurement of this distance, whereas for HVDC transmission no substantial work has been done. An equivalent AC voltage value can be derived from the DC voltage value in order to use the Gallet equation. This paper presents an experimental measurement technique for determining the MVCD at 500 kV to verify the results obtained from the Gallet equation in the case of DC voltage. Performing the experiment with a 500 kV DC line is not possible in the laboratory due to safety concerns. Therefore, an experiment up to 60 kV is conducted to measure the MVCD for DC voltage. The measured results achieved from the experiment are then extrapolated to calculate the MVCD at 500 kV.

Grounding Connections

2018 ◽  
pp. 84-123
Keyword(s):  
Transmission Lines ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Power Sources ◽  
Grounding Resistance ◽  
Overhead Transmission Lines ◽  
Ground Fault ◽  
Multiple Power

This chapter sheds light on the following: TT system (earthed neutral), automatic disconnection for TT system, TN system (exposed conductive parts connected to the neutral), TN-C system, TN-S system- TN-C-S system, IT system (isolated or impedance-earthed neutral), IT system (impedance-earthed neutral), grounding transformer connection and design, grounding of industrial and commercial generators, Zigzag grounding transformer earthed systems (solid grounding, resistance grounding, reactance grounding, resonant grounding (ground-fault neutralizer), location of system grounding points selection and grounding locations specified by the NEC and multiple power sources. The chapter contains also the different methods used in determining the levels of short circuit current. It contains also details about the grounding through resistances for transformers and generators and reactances for overhead transmission lines.

scholarly journals Power quality in high voltage mains supplying mainline railroads’ traction substations

2019 ◽  
Vol 114 ◽  
pp. 04001
Author(s):  
Yu.N. Bulatov ◽  
A.V. Kryukov ◽  
A.V. Cherepanov
Keyword(s):  
Power Quality ◽  
Transmission Lines ◽  
Large Scale ◽  
Power Transmission ◽  
Short Circuit ◽  
Far East ◽  
Power Transmission Lines ◽  
Quality Factors ◽  
Significant Deterioration ◽  
Traction Substations

The increase in the trains weight and their operation speeds leads to considerable growth of abrupt-variable, non-linear and one-phase traction loads. This, in its own turn, leads to significant deviations, unsymmetry and voltage harmonic distortions in 110-220 kV mains adjacent to traction substations of AC railroads. Significant deterioration in power quality factors is observed in Siberian and Far East regions where 110-220 kV main power transmission lines are immediately adjacent to Transsib traction substations; in this case, in points with lower levels of short circuit power, power quality factors exceed by far the permissible levels. The articles provides the results of studies aimed at solution of power quality enhancement is-sues for mains adjacent to traction substations of Trans-Siberian Railway. To enhance power quality in mains supplying traction substations, smart grid technologies can be used together with multiagent control systems. Technical solutions, based on the results obtained, are proposed that allow to bring the power quality factors to the regulatory values. Due to a big investments amount, an implementation of tar-get program is needed to resolve the large-scale issue of enhancing power quality in mains adjacent to traction substations of AC railroads.

The UHVDC Transmission Line Lightning Disturbance Identification Based on the Morphology

2014 ◽  
Vol 1008-1009 ◽  
pp. 603-609
Author(s):  
Rui Rui Cao ◽  
Ju Rui Yang
Keyword(s):  
Transmission Lines ◽  
Short Circuit ◽  
Low Frequency ◽  
Transient State ◽  
Spectral Energy ◽  
Complex Signal ◽  
Main Criterion ◽  
Lightning Stroke ◽  
Multi Scale ◽  
Overhead Transmission Lines

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.

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