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Insulation Coordination of Arcing Horns on HVDC Electrode Lines: Protection Performance Evaluation, Influence Factors and Improvement Method

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Insulation Coordination of Arcing Horns on HVDC Electrode Lines: Protection Performance Evaluation, Influence Factors and Improvement Method energies Article Insulation Coordination of Arcing Horns on HVDC Electrode Lines: Protection Performance Evaluation, Influence Factors and Improvement Method Xiandong Li 1,2,3,* ID , Hua Li 1,2,3,*, Yi Liu 1,2,3 and Fuchang Lin 1,2,3 1 State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science & Technology, Wuhan 430074, China; [email protected] (Y.L.); [email protected] (F.L.) 2 School of Electrical and Electronic Engineering, Huazhong University of Science & Technology, Wuhan 430074, China 3 Key Laboratory of Pulsed Power Technology (Huazhong University of Science and Technology), Ministry of Education, Wuhan 430074, China * Correspondence: [email protected] (X.L.); [email protected] (H.L.) Received: 19 January 2018; Accepted: 11 February 2018; Published: 13 February 2018 Abstract: Arcing horns are widely used in high voltage overhead lines to protect insulator strings from being destroyed by the free burning arcs caused by lightening faults. In this paper, we focus on the insulation coordination of arcing horns on the electrode lines of a 5000 MW, ±800 kV high voltage direct current (HVDC) system. The protection performance of arcing horns are determined by the characteristics of not only the external system but also the fault arc. Therefore, the behaviors and characteristics of long free burning arcs are investigated by the experiments at first. In order to evaluate the protection performance of arcing horns, the static stability criterion U-I characteristic method is introduced. The influence factors on the protection performance of arcing horns are analyzed theoretically. Finally, the improvement methods for the protection performance of arcing horns are proposed, and the diversified configuration strategy of arcing horns is recommended for cost saving. Keywords: HVDC electrode line; arcing horn; insulation coordination; protection performance; long free burning arc; arc behavior and characteristic 1. Introduction 1.1. Insulation Coordination Problem of Arcing Horns on HVDC Electrode Lines Arcing horns are widely used on high voltage overhead transmission lines to protect insulator strings from being destroyed by the free burning arcs caused by lightening faults. However, it is hard to extinguish arcs in high voltage direct current (HVDC) system, since there is no natural current zero point. Besides, it is difficult to detect fault arcs, especially for HVDC electrode lines, so fault arcs may continue to burn once formed if the fault arc is not detected. As a result, both arcing horns and insulator strings will be destroyed in the end. With the fast growing power transfer and transmission distance of HVDC systems, the insulation coordination problem of HVDC electrode lines is becoming more serious. Therefore, research on the performance of the arcing horns on HVDC electrode lines is very necessary. Electrode lines are used for the current return pass and as the voltage reference point of HVDC system. When the system is operating in bi-polar mode, as shown in Figure1a, the unbalanced current on the electrode lines can be ignored. Hence, there will be no problem with the extinction of fault arcs. However, when the system is operating in mono-polar mode, as shown in Figure1b, the operation Energies 2018, 11, 430; doi:10.3390/en11020430 www.mdpi.com/journal/energies Energies 2018, 11, 430 2 of 19 Energies 2018, 11, x FOR PEER REVIEW 2 of 19 currentoperation on the current electrode on the lines electrode is rather lines large. is rather If ala lightningrge. If a lightning fault happens, fault happens, the fault the fault arc arc may may not be extinguished,not be extinguished, then both then the arcingboth the horns arcing and horns insulator and insulator strings strings will be will burned be burned and and destroyed. destroyed. (a) HVDC system operated in bi-polar mode (b) HVDC system operated in mono-polar mode Figure 1. Operation mode of HVDC system. Figure 1. Operation mode of HVDC system. 1.2. Current Reaserches on Insulation Coordination of Arcing Horns on HVDC Electrode Lines 1.2. Current Reaserches on Insulation Coordination of Arcing Horns on HVDC Electrode Lines To solve this problem, the characteristics of fault arcs should be investigated firstly, and an optimizedTo solve insulation this problem, coordination the characteristicsscheme should be of studied fault based arcs the should characteristics be investigated of fault arcs. firstly, andThus, an optimized the whole insulation problem involves coordination two aspects: scheme the shouldcharacteristics be studied of fault based arcs and the characteristicsthe insulation of faultcoordination arcs. Thus, scheme. the whole problem involves two aspects: the characteristics of fault arcs and the insulationThe coordination fault arcs in scheme.HVDC systems are long free burning arcs. The long free burning arc (>100 mm) has quite different properties compared with the short arc (<10 mm) and the arc in closed space The fault arcs in HVDC systems are long free burning arcs. The long free burning arc (>100 mm) because of its complex behavior. The existing studies about long arcs are mainly concerned with its has quite different properties compared with the short arc (<10 mm) and the arc in closed space movement [1–5] and electrical [4–11] characteristics. because ofAs its for complex the insulation behavior. coordinati The existingon scheme, studies some aboutstudies long have arcs been are carried mainly out concerned [12–14]. Those with its movementworks can [1– 5be] andclassified electrical by their [4– methods11] characteristics. into two kinds: the maximum arc extinction current method andAs the for U-I the characteristic insulation method. coordination scheme, some studies have been carried out [12–14]. Those worksCanellas can [12] be classified carried out by studies their methodson the extinction into two of kinds:direct current the maximum (DC) arcs arc on extinctionlong electrode current methodlines and based the on U-I the characteristic experimental method. results of the Itaipu group, and gave the relations between the maximumCanellas [ 12arc] carriedextinction out current studies and on thethe extinctiongap length of of direct arcing current horns. (DC)However, arcs onthe long maximum electrode arc lines basedextinction on the experimental current is only results few hundreds of the Itaipu (≤400 group, A) and and the gavemaximum the relations gap length between is less thethan maximum 500 mm, arc extinctionwhich currentare not suitable and the for gap the length HVDC of systems arcing horns.with large However, operation the currents maximum used arc today. extinction current is Jankov [13] discussed about the protection performance of arcing horns on the HVDC system only few hundreds (≤400 A) and the maximum gap length is less than 500 mm, which are not suitable with neutral conductor. The static stability criterion Voltage-Current characteristic method (or U-I for the HVDC systems with large operation currents used today. characteristic method as usually called) was adopted to find the maximum protection region of arc horns.Jankov In [ 13our] discussedprevious works. about th thee protection protection performance performance of arcing of arcing horns horns in HVDC on the electrode HVDC lines system withwas neutral investigated conductor. also based The staticon the stabilityU-I characterist criterionic method, Voltage-Current and the influence characteristic factors were method analyzed (or U-I characteristicpreliminarily method [14]. Although, as usually the called) U-I characteristic was adopted method to find has the been maximum proved to protection be an effective region way of arc horns.for Inthe our insulation previous coordination works. the of protection arcing horns performance by [13,14], none of arcing of them horns provided in HVDC a comprehensive electrode lines was investigatedstudy on the influence also based factors on theand U-I the characteristicprotection performance method, improvement and the influence strategy factors for arcing were horns. analyzed preliminarily [14]. Although, the U-I characteristic method has been proved to be an effective way for the insulation coordination of arcing horns by [13,14], none of them provided a comprehensive study on the influence factors and the protection performance improvement strategy for arcing horns. Energies 2018, 11, 430 3 of 19 EnergiesIn this 2018 paper,, 11, x FOR the PEER insulation REVIEW coordination of arcing horns on the electrode lines of a3 5000 of 19 MW, ±800 kV HVDC system is studied. The U-I characteristic method is used to evaluate the protection performanceIn this of paper, arcing the horns. insulation Since coordination the protection of arcing performance horns on the of electrode arcing horns lines of is adecided 5000 MW, by the ±800 kV HVDC system is studied. The U-I characteristic method is used to evaluate the protection characteristics of not only electrode line system but also the fault arc, experiments have been carried performance of arcing horns. Since the protection performance of arcing horns is decided by the out tocharacteristics investigate of the not characteristics only electrode ofline long system free but burning also the arcs. fault The arc, factorsexperiments influencing have been the carried protection performanceout to investigate of arcing the horns characteristics are analyzed of long theoretically.free burning arcs. Finally, The factors the improvement influencing the strategy protection
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