Backflashover Rate Of Transmission Lines Research Articles

Review of measures to improve the lightning performance of transmission lines

• Measures for improving the lightning performance of transmission lines. • Reducing the backflashover rate of transmission lines. • Techniques for improving TL lightning performance. • Threshold tower-footing grounding resistance for improved lightning performance. • Impulse impedance of tower-footing electrodes of transmission lines. This paper discusses fundamental aspects related to the measures for improvement of the lightning performance of transmission lines, considering the advantages and constraints on their application. The content reflects the experiences developed by the authors facing exciting challenges related to the improvement of the performance of real transmission lines installed under very unfavorable conditions. The work considers the approaches and the calculating procedure the authors adopted for providing the support required for decisions about the measure to be adopted. The results seem to be useful for academics and professionals involved with theoretical and practical aspects related to the lightning performance of transmission lines.

Influence of the earthing systems described in the IEEE 1243 Standard on the back-flashoverrate of transmission lines

Este trabajo trata sobre los dos diferentes modelos resistivos de puesta a tierra usados en líneas de transmisión presentados en el estándar IEEE 1243-1997: tierra suplementaria con varillas y con contrapesos. Se analizó el efecto de variar los parámetros internos de cada modelo que afectan el valor resistivo de puesta a tierra en la reducción o aumento de la tasa de fallas por flameo inverso por impactos de rayos sobre la torre o el cable de guarda sobre terrenos con diferentes conductividades. El software ATPDraw se usó para obtener las corrientes críticas, para luego con estas obtener la tasa de fallas de la línea. Se simuló el efecto del número, la longitud, radio y enterramiento de los electrodos en las tasas de fallas por flameo inverso de una línea de transmisión para diferentes valores de conductividad del terreno. Se obtuvieron porcentajes de reducción de la tasa de fallas que van en general desde el 50 hasta el 95%.

Constraints on the use of surge arresters for improving the backflashover rate of transmission lines

The effectiveness of using transmission line surge arresters (TLSA) under different conditions for improving the lightning performance of lines is assessed by means of computational simulation. These conditions comprise using TLSA only in critical towers and/or using devices only in certain phases, leaving one or two-phases unprotected. In addition to assess the effect on stricken towers, the transfer of overvoltage to unprotected adjacent towers is also addressed, considering different values of tower-footing impedance. In the analyses, lightning overvoltages across insulator of typical single-circuit 138-kV and double-circuit 230-kV transmission lines were calculated by using the Hybrid Electromagnetic Model (HEM) and flashover occurrence was assessed by using the Disruptive Effect method (DE), in each simulated condition. The results indicate that the operation of TLSA protects the own insulator and diminishes the backflashover risk at unprotected insulators. However, this risk remains high, depending on tower-footing impedance. Also, the risk of flashover at the unprotected adjacent towers due to the operation of surge arresters at the stricken tower was found to be significant in the case of all phases of the stricken tower protected, notably when the tower-footing impedance of the protected tower is high and that of the adjacent tower is low.

Lightning performance of transmission lines: Assessing the quality of traditional methodologies to determine backflashover rate of transmission lines taking as reference results provided by an advanced approach

This paper presents a critical review of CIGRE and IEEE traditional methodologies for calculating the backflashover outage rate (BFOR) of transmission lines, considering their adopted simplifications. These methodologies, along with an advanced computational approach named HEM-DE, were applied to a real 138-kV line to determine its backflashover rate. The quality of the results produced by the methodology at each step of their calculation procedure was assessed and discussed, taking as reference the accurate results provided by the advanced approach, based on the application of the hybrid electromagnetic model (HEM) and disruptive effect model (DE). According to this assessment, in the 40-to-10-Ω range of tower footing grounding resistance, the CIGRE methodology overestimates outage rate of the line in relation to the reference values (98–21% larger in the 40-to-10-Ω range of tower footing grounding resistance). The IEEE methodologies underestimates the BFOR, yielding rates 47–23% lower in the same resistance range.

The effect of wide band modeling of tower-footing grounding system on the lightning performance of transmission lines: A probabilistic evaluation

This paper presents a probabilistic evaluation, based on Monte-Carlo method, to estimate back flashover rate (BFR) and shielding failure flashover rate (SFFOR) of overhead transmission lines (TLs). In the proposed approach, as opposed to the conventional methods, a wide band model of the tower-footing grounding system is adopted assuming the soil electrical parameters to be either constant or frequency dependent. The statistical parameters affecting the TLs’ outage rate are taken into account in the probabilistic studies. Simulations are done for a typical 400-kV transmission line which is modeled in EMTP.RV. From the simulation results, it is found that the BFR of transmission lines is markedly affected by the tower footing grounding system model. This effect is more pronounced when the soil electrical parameters are frequency dependent. It is also found that the SFFOR of the transmission lines is not significantly affected by the wide-band model of the tower-footing grounding system.